CA2115211C - Adaptive medium access control scheme for wireless lan - Google Patents

Adaptive medium access control scheme for wireless lan

Info

Publication number
CA2115211C
CA2115211C CA002115211A CA2115211A CA2115211C CA 2115211 C CA2115211 C CA 2115211C CA 002115211 A CA002115211 A CA 002115211A CA 2115211 A CA2115211 A CA 2115211A CA 2115211 C CA2115211 C CA 2115211C
Authority
CA
Canada
Prior art keywords
base station
remote stations
slots
remote
period
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
CA002115211A
Other languages
French (fr)
Other versions
CA2115211A1 (en
Inventor
Hamid Ahmadi
David F. Bantz
Frederic J. Bauchot
Arvind Krishna
Richard O. Lamaire
Kadathur S. Natarajan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Wistron Corp
Original Assignee
International Business Machines Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by International Business Machines Corp filed Critical International Business Machines Corp
Publication of CA2115211A1 publication Critical patent/CA2115211A1/en
Application granted granted Critical
Publication of CA2115211C publication Critical patent/CA2115211C/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W74/00Wireless channel access, e.g. scheduled or random access
    • H04W74/02Hybrid access techniques
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W48/00Access restriction; Network selection; Access point selection
    • H04W48/08Access restriction or access information delivery, e.g. discovery data delivery
    • H04W48/12Access restriction or access information delivery, e.g. discovery data delivery using downlink control channel
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W84/00Network topologies
    • H04W84/02Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/10Small scale networks; Flat hierarchical networks
    • H04W84/12WLAN [Wireless Local Area Networks]

Abstract

A Medium Access (MAC) Protocol is utilized for wireless radio access for a plurality of remote stations to a base station on a LAN. The MAC protocol is based on a reservation scheme for user data traffic and a random access technique for control and signalling traffic. There is a time division fixed frame structure in which time is slotted, and time slots are grouped into fixed frames consisting of data and control subframes or periods. The fixed frame structure consists of three periods (A, B, and C) along with their respective headers. The first period, the A period, is the outbound channel which is used exclusively for data transfer from the base station to the remote stations. The following period, the B period, is the inbound channel that is used for contention-free data transfer from the remote stations to the base station. The allocation of the data slots in the A and B periods is performed by the base station. The last period of the frame, designated as the C period, is the control channel used for the transmission of reservation requests and data from the remote stations to the base station in a random-access contention mode using a slotted Aloha protocol. The duration of the three periods may be varied using a movable boundary technique. The base station estimates the number of actively transmitting remote stations utilizing feedback information from the remote stations. This estimate is broadcast to the remote stations as control indicia to control their transmission attempts in the C period, thus yielding high transmission efficiency.

Description

YO9-93-018 1 2~1~21~

AN ADAPTIVE MEDIUM ACCESS CONTROL SCHEME FOR WIRELESS LAN

Field of the Invention This invention relates generally to data communications, and in particular such communications in a Local Area Network (LAN).
Specifically, the invention is directed to a Medium Access Control (MAC) protocol for wireless access in a LAN.

Background of the Invention The need for personal wireless communications is expanding rapidly with the advances in digital communications and personal communications systems. The progress in cellular radio technology and the growth rate of the cellular telephone systems over the last years is indicative of tremendous market demand for location independence communication via wireless access. Many of the current wireless networks architectures are primarily designed and optimized for voice communications and wide area coverage. With the proliferation of personal and portable computers, and local area networks, it is envisioned that data services and applications such as file server access, client-server execution, and electronic mail will require wireless access in the LAN environment supporting distributed computing. Since the characteristics and profile of data tr~ffic are very different ~rom those of voice traffic, the wireless access protocol must efficiently accommodate the very dynamic and bursty nature of data traffic.

U.S. Patent 4,907,224 to Scoles et al discloses a method for transmitting data in packet switching networks which provides a Collision-Eliminating Multiple Access protocol in which nodes desiring to transmit over the network channel transmit reservation request~ during a plurality of contention slots, the number of contention slots being dynamically controlled according to network load. A node designated to next obtain control of the channel receives the identifiers of nodes transmitting reservation requests and, prior to transmitting application data, transmits network control data consisting of the identifiers of nodes from whom reservation requests were successfully received. The transmitted identifiers are received and stored by each node in an identical Y09-93-018 2 2 1 1 ~ 2 1 1 queue whereby subsequent control of the channel is rotated based on the order of node identifiers appearing on each node. The transmitted network control data includes reservation requests received during a previous contention slot period, queue correction information, and the identifiers of nodes from which the controlling node expects to receive data.

U.S. patent 5,123,029 to Bantz et al which is assigned to the assignee of this invention, discloses a hybrid controlled access and random access scheme using frequency hopping spread spectrum communication techniques implemented in an indoor digital data radio communication system between mobile stations and a computer system. A hop in the frequency hopping spread spectrum communication system is subdivided into two intervals so that different media-access protocols can be used in each interval. The protocol use~ a centralized control scheme in one interval and a decentralized scheme in the other, and the intervals may be varied depending on the load of the system.

L. G. Roberts, "Dynamic Allocation of satellite capacity through packet reservation", Nat. Comput. Conf. AFIPS Conf. Proc. Vol. 42, pp. 711-716, June 1973, describes a proposal for a MAC protocol baaed on a reservation scheme for user data traffic and a contention scheme for making reservations.

According to the present invention, an adaptive and efficient Medium Acce~s Control (MAC) protocol for wireless access in a local area environment i~ capable of supporting both bursty data traffic and synchronous services such as voice and video. A
packet-switched architecture is utilized in which several mobile remote stations within a given cell (small cells covering a range of a few hundred meters) communicate with a base station using radio channels, which can be connected to a fixed local area network. Remote stations can operate both indoor and outdoor with limited range and have wireless access to the base stations on the backbone network. As an example, consider the environment of an industrial campus consisting of several office buildings. The buildings are divided into cells, and cells are connected via some backbone network such as wired LAN. This invention addresses the intra-cell multiaccess problem. The basic problem here is how to coordinate the wireless channel bandwidth which is shared by all Y09-93-018 3 2~2~1 mobile stations within a cell in a fair, flexible demand-driven manner and achieve a high throughput.

Disclosure of the Invention A Medium Access Control (MAC) Protocol for wireless radio access for a plurality of remote stations to a base station on a LAN is disclosed. The MAC protocol is based on a reservation scheme for user data traffic and a random access technique for control and signalling traffic. There is a time division fixed frame structure in which time is slotted, and time slots are grouped into fixed frames consisting of data and control subframes or periods. The fixed frame structure consists of three periods (A, B, and C) along with their respective headers. The first period, the A period, is the outbound channel which is used exclusively for data transfer from the base station to the remote stations. The following period, the B period, is the inbound channel that is used for contention-free data transfer from the remote stations to the base station. The allocation of the data slots in the A and B periods i8 performed by the base station. The last period of the frame, designated as the C period, is the control channel used for the transmission of reservation requests and data from the remote stations to the base station in a random-access contention mode using a slotted Aloha protocol. The duration of the three periods may be varied using a movable boundary technique. The base station estimates the number of actively transmitting remote stations utilizing feedback information from the remote stations. This estimate is broadcast to the remote stations as control indica to control their transmission attempts in the C period, thus yielding high transmission efficiency.

Brief Description of the Drawings FIG. l is a pictorial diagram showing an indoor radio digital data communication system of the type in which the invention is implemented;

FIG. lA is a block diagram of the system shown in FIG.
illustrating the basic components of a mobile station and a base station;

Y09-93-018 4 2 ~ 1 5 2 ~ ~

FIG. 2 is a block diagram of the radio system used in the implementation of a preferred embodiment of the invention;

FIG. 3 is a diagram of the frame structure of the MAC protocol according to the invention;

FIG. 4 is a flow chart of the logic followed by a base station in the MAC protocol of the invention;

FIG. 5 is a flow chart of the logic followed by a remote station in the MAC protocol of the invention;

FIG. 6 is a flow chart for computing the number of outstanding packets for period A of the MAC protocol;

FIG. 7 is a flow chart for computing the number of outstanding packets for period B of the MAC protocol;

FIG. 8 is a flow chart for computing the length of periods A, B and C of the MAC protocol;

FIG. 9 i~ a flow chart of a method of estimating the number of remote station~ that are attempting to transmit during the period C o~ the MAC protocol;

FIG. 10 is a detailed flow chart of block 208 of the flow chart of FIG. 9; and FIGS. 11 and 12 are each schematic diagrams of a Bernoulli random variable generator as used in the practice of the invention.

Doscription of the Preforred Embodiment A MAC protocol is described that is based on a reservation scheme for user data traffic and a random access technique for the control and signaling traffic. The proposed scheme is based on a time division frame structure. Time is slotted, and time slots are grouped into fixed frames consisting of data and control subframes.
The data channel is also divided into two segments one for the inbound (remote stations to base station) and the other for the outbound (base station to remote) transmissions. The motivation 21:~21~

for using the reservation scheme for data transmission is described below.

The nature of user traffic could be very bursty, unpredictable and highly correlated, therefore, reserving bandwidth on demand would accommodate a superior grade of service and performance. Since radio channels have a higher error rate than a typical wired channel, it is necessary to transmit small packets over the wireless link. Therefore a user data message must be fragmented into small packets for the wireless link. This implies that a ~ingle user message or request may result in a group of wireless packets that need to be transmitted with a minimum delay.

Stream-like traffic such as voice and video require guaranteed bandwidth for synchronous transmission.

The invention includes the following features:

1. A random access control channel which is used for reservation requests and a demand-driven reservation-based data channel, one for inbound and one for outbound.
2. A unified scheme for support of bursty interactive data and stream like synchronous traffic.
3. Small contention slots to accommodate more users and achieve hlgher throughput.
4. A technique for flexibly and dynamically adjusting frame boundaries between control and data channels as well as between inbound and outbound channels to achieve maximum throughput.
5. An adaptive state-dependent random-access transmission scheme for the control channel to achieve maximum throughput using a real-time estimation technique.
6. A simple Bernoulli random variable generator that is computationally efficient.

Referring now to the drawings, and more particularly to FIG. l, Y09-93-018 6 ~ 2 1 1 there is shown an indoor radio system allowing communication between a plurality of mobile stations 10, 12, 14, and 16 and applications and data residing in a computing system. The computing system typically includes a Wireless Network Mana~er (WNM) or Wireless Network Controller 18, with attached monitor 20 and keyboard 22, of a local area network (LAN), generally indicated by reference numeral 24, having a plurality of attached workstations or personal computers (not shown for simplicity).
Also attached to the LAN are one or more gateways 26 and 28 with which the mobile stations 10, 12, 14, and 16 communicate. These gateways, referred to as base stations, are augmented according to the invention to provide certain radio system management functions which coordinate the mobile stations' access to the common radio channel. Communications between mobile stations is supported via relay through the base stations 26 and 28.

As shown in more detail in FIG. lA, a base station 26 or 28, which may be a conventional microcomputer, has a LAN adapter 30 inserted in a bus slot and connected to LAN cabling 32. The WNM 18, typically also a conventional microcomputer and including one or more direct access storage devices (DASDs) such as hard disks (not shown), also has a LAN adapter 34 inserted in a bus slot and connected to LAN cabling 32. The LAN adapters 30 and 34 and the LAN cabling 32 together with LAN software constitute the LAN 24.
The LAN 24 is of conventional design and does not form part of the invention. The base station 26 or 28 also has an RF transceiver adapter 36 implemented as a printed circuit card which is inserted in a bus slot of the base station. The transceiver adapter 36 includes a spread spectrum transceiver of conventional design. The transceiver adapter 36 has an antenna 38 by which a radio link 40 is established with one or more remote or mobile stations, 10, 12, 14, or 16. The mobile station may itself be a hand held or lap top computer of conventional design and, like the base station, it is provided with an antenna 42 and a transceiver adapter 44, also implemented as a printed circuit card which is inserted in a bus slot of the computer. The transceiver adapter 44, like transceiver adapter 36, includes a spread spectrum transceiver of similar design. The base station and the mobile stations are further provided with software, generally indicated by reference numerals 46 and 48, respectively, which support their respective transceiver adapters.

Y09-93-018 7 21~2 ~ 1 FIG. 2 shows the radio system common to both the mobile stations and the base stations of FIG. 1. The radio system includes a transceiver adapter 36 or 44 connected to the computer 50 via the computer's bus interface 52. The transceiver section is itself divided into an RF transceiver 54, which may be a commercially available spread spectrum transceiver, and a dedicated microprocessor system 56 which controls the transceiver via an interface 58. The microprocessor system 56 further includes a system interface 60 which interfaces the transceiver section to the computer section 50. The microprocessor system includes a dedicated microprocessor 62 containing high-resolution time interval determination hardware or "timers" typical of real-time microprocessor systems.

Microprocessor 62 is connected by a memory bus 64 to program storage 66 and data storage 68 as well as to interfaces 58 and 60 providing attachment to bus interface 52 and RF transceiver 54, respectively. Program storage 66 is typically read only memory (ROM), while data storage 68 is static or dynamic random access memory (SRAM or DRAM). Packets received or to be sent are held in data storage 68 and communicated to or from the RF transceiver 54 via interface 58 under control of serial channels and a direct memory access (DMA) controller (not shown) which is part of the microprocessor 62. The function of these serial channels is to encapsulate data and control information in an HDLC (high-level data link control) packet structure and provide the packet in ~erial form to the RF transceiver 54. For more information on the HDLC packet structure, see, for example, Mischa Schwartz, Telecommunication Networks: Protocols, Modeling and Analysis, Addi~on- Wesley (1988).

When a packet is received through the RF transceiver 54, the serial channels check the packet destination address, check for errors, and deserialize the packet to data storage 68. The serial channels must have the capability to recognize a specific adapter address as well as a broadcast address. Specific microprocessors with appropriate serial channel and timer facilities include the Motorola 68302 and the National HPC46400E microprocessors.

The computer 50 runs an operating system 70 which supports one or more user application programs 72. The operating system 70 may 21 1~2~.~

include a communications manager 74, or the communications manager 74 may itself be an application program installed on the computer.
In either case, the communications manager 74 controls a device driver 76 via the operating system 70. The device driver 76, in turn, communicates with the transceiver adapter 36 or 44 via bus interface 52.

Protocol System Description The fixed frame structure consists of three periods (A, B, and C) along with their respective headers as is shown in FIG. 3. The first period, designated as the A period, is the outbound channel which is used exclusively for data transfer from the base station to the remote stations. The following period, designated as the B
period, is the inbound channel that is used for contention-free data transfer from the remote stations to the base station. The allocation of the data slots in the A and B periods is performed by the base station. The last period of the frame, designated as the C period, is the control channel used for the transmission of reservation requests and data from the remote stations to the base station in a random-access mode using a slotted Aloha protocol.
finite number of remote stations contend on the control channel to make requests for a number of slots (corresponding to one user message) on the outbound or inbound data channel. The slot sizes in the A and B periods are equal and each accommodates one wireless data packet. The slots in the C period are typically much smaller and are referred to as mini-slots. Each such mini-slot accommodates one control packet. The use of mini-slots for the control channel yields higher efficiency both in terms of the number of users that can be supported and bandwidth utilization, than if full sized slots were used. This is because the contention channel achieves a throughput of about 37% in slotted Aloha (i.e., a wastage of 63%) whereas the A and B periods always have 100% utilization. Thus, the only bandwidth wastage occurs in the control channel so wastage is minimized in the invention by making the C slots small.

Each period has a header section in which it carries access control information as is shown in FIG. 3. The A header is the time interval during which the base station broadcasts a message to all of the remote stations that signals the beginning of the A period.
This header also contains the length of the A period, the outbound .- . ~ .

Y09-93-018 9 ~ 2 1 1 slot allocation schedule and control information for the physical layer.

The B header is the time interval during which the base station broadcasts a message signalling the end of the A period and the beginning of B period. It also contains the length of the B period and additional control information. In particular, a slot allocation schedule is specified in the B header so that each remote station will know when to transmit in the B period.

Similar to the A and B headers, the C header signals the end of the B period and the beginning of the C period. The C header also contains the length of the C period and other control information concerning the probability of transmission that will be used by the remote statiQns for the C period of the frame. In the C period, any remote station may contend for the channel and transmit a message without an explicit allocation from the base station. The contention scheme is based on a slotted Aloha protocol such that each of the finite number of remote stations attempts to transmit in a given mini-slot (i.e., a C slot) with some probability p. The ~tochastic decision to transmit or not is made independently at each of the remote stations. If at most one remote station Qttempts to transmit in a slot, then that station has successfully contended for transmission. If more than one station attempts transmission in a slot, then they collide and will try to retransmit in the next C slot with the same probability p. The value of this probability is adaptive and it may be changed from one frame to another by the base station. An estimation algorithm for adapting this p value is described later. As mentioned above, the base station informs (using the C header) all of the remote ~tations about the new value of p at the beginning of the C period.
Since collisions cannot be!detected, an acknowledgement message is used to signify the correct reception of a packet. Therefore, all packet transmissions must be acknowledged either individually or as a group.

Period C is used for the following types of information:

1. Registration requests that enable remote stations to identify themselves and request the services of the base station.

yog-93-018 10 2 :1 ~ 5 2 1 1 2. Requests for transmission time in the B period.

The transmission time requests can be either for synchronous or asynchronous services. Here, by synchronous service is implied establishment of a connection that requires guaranteed bandwidth for a sustained period of time. When a remote station transmits a reservation request, it identifies the type of service it requires plus the number of slots for asynchronous service or the bandwidth for the synchronous service. The base station schedules the allocation of slots and transmits the map of the schedule to each remote station. For the asynchronous traffic, slots are allocated in each frame for the duration of the connection. These slots can be positioned anywhere within a frame. For the synchronous traffic, slots are reserved in the first available frame, and in the following frames, for the requested allocation. The re~ervation requests can also be piggy-backed on the first data packet in order to reduce contention on the control channel. The base station ensures the scheduling of all received requests.

Operation at the Base Station An overview of the logic followed by a base station is shown in FIG. 4. When the base station is powered on, it executes an initialization procedure at block 100.

At the beginning of a frame, as shown at block 101, the base station may have packets for outbound transmission to a set of remote stations. If there is no outbound data, then parameter TA
i~ ~et to 0. If outbound packets are to be transmitted to a remote station V, then the A period header at block 102 will include <V,Out(V)>, where Out(V) is the number of packets that V will receive in the current frame. TA is set equal to the total number of outbound packets that will be transmitted in the current frame.
The base station then transmits to remote stations in a reservation mode at block 103.

At the beginning of each frame, the base station may have a set of pending bandwidth reservation requests for inbound data transfer (from remote stations to the base station). If the set of pending requests is empty, then parameter TB (block 101) is set to 0.
Otherwise, the base station attempts to grant as many of the ~ : . - :

yog-93-0l8 ll 2~ 15211 reservation requests as is possible. If remote station V is granted In(V) slots in the current frame, then the B period header is transmitted at block 104 and will include ~V,In(V)>. TB is set equal to the total number of inbound slots that have been allocated. At block 105, remote stations transmit to a base station in a reservation mode.

At the beginning of the C period, the base station transmits at block 106 the current estimate K of the number of active remote stations as well as TC, the length of the C period. When remote stations transmit at block 107 using the slotted Aloha protocol in the C period, the base station obtains control information from the header of each packet that is successfully received. This control information is a single bit called a retry bit, which indicates whether or not the packet has been retried. That is, has the packet been retransmitted due to collision or noise during its first transmission attempt. The retry bit is used by an estimation procedure in block 108 that is run in the base station to revise its estimate of K. The method used to estimate K is described in detail in a later section. At the conclusion of the C period, the base station returns to the steps of computing the lengths of the three intervals for the next frame at block 101.

Operation at the Remote Station An overview of the logic followed by a remote station is shown in FIG. 5. When the remote station is powered on, it executes an initialization procedure at block 120 and sets a set of internal parameters. Then, it obtains synchronization with the base station and starts listening to the header messages of a frame.

At the beginning of a frame, a remote station, S, receives the A
period header at block 121 and extracts TA, the length of the A
period. It sets a timer for duration TA. It receives all packets broadcast by the base station that are addressed to it. At block 122, the base station transmits to the remote stations in a reservation mode.

At the end of the A period, the timer elapses and the remote station receives the B period header at block 123. It extracts TB, the length of the B period and sets a timer for duration TB. If a yo9-93-018 12 2 1 1 ~ 2 ~ 1 remote station has slots allocated to it, then it transmits to the base station at its designated time at block 124.

At the end of the B period, the timer elapses and the remote station receives the C period header at block 125. It extracts TC, the length of the C period and sets a timer for duration TC. It also learns about K and computes p=1/K, the probability for transmission in a C period slot. In the C period, the remote station follows the slotted Aloha protocol for transmitting to the base station in a contention mode. When the timer elapses, the current frame is finished and the remote station returns to the ~tep of listening for the A period header of the next frame at block 121.

Boundary Ad~ustment Method An adaptive method is used to adjust the lengths of the three periods, A, B, and C, of the protocol so as to rapidly adapt the sizes of the three periods of the frame according to changes in the traffic conditions. The lengths of the three periGds are computed by the base station at the beginning of the frame and transmitted to all the remote stations in the A period header. The lengths of periods B and C are also included in the headers of their respective periods transmitted by the base station. The choices are designed to achieve a desirable throughput in each of the three periods.

The three main goals of the method are described below. Priority is given to the outbound traffic (period A). Since traffic is generated by reservation requests originating from the remote stations, by giving priority to the outbound traffic the outstanding requests can be completed before more requests enter the sy~tem. A minimum bandwidth is preserved for the inbound traffic (period B) to help prevent starvation of the inbound channel. Finally, a minimum bandwidth is preserved for the C
period to provide good performance for the control channel and to ensure that when a new remote station enters the base station's cell, it will find a non-zero C period in which to perform registration.

The method must comply with the following constraint, which is YO9-93-018 13 ~ 2 1 1 dictated by the system description given earlier. Assume that the slots in the A and B periods are of the same size and that the ratio of these regular-sized slots to the mini-slots of the C
period is R:l, then TA + TB + TC/R = TF where TA, TB and TC are the number of slots in the A, B and C periods, respectively, and where TF is the frame size divided by the size of an A or B slot.

The method described is a centralized scheme that is run at the base station. The base station computes the lengths of the periods based on the queue lengths (traffic waiting to be transmitted in the period) for the periods A and B as shown in FIG. 6 and FIG. 7.
The base station maintains the two variables QA and QB as described in detail below. As shown in FIG. 6, the base station maintains a variable QA at block 159 which represents the total number of "outbound waiting packets" to be sent in the A period. For each new outbound data message received for transmission at block 160 by the base station, QA is incremented at block 161 by the number of packets required to tran~mit the associated buffer. For each packet transmitted in the A period at block 162, QA is decremented by one at block 164 if the packet is successfully received by the remote station at block 163 (i.e., an acknowledgment is received).
If the packet i~ not received successfully at block 163, a return is made to block 160, as is the case following QA being decremented by one at block 164.

As shown in FIG. 7, the base station maintains a variable QB at block 169 which represents the total number of "inbound waiting packets" to be received by the base station from the remote stations in the B period. For each slot allocation request received from a remote station at block 170, QB is incremented by the number of required slots at block 171. For each packet that is transmitted in the B period at block 172, QB is decremented by one at block 174, if the packet is successfully received by the base station as determined at block 173 (i.e., an acknowledgment is received). Otherwise (e.g., if a packet is lost, that is, it is not received successfully, due to radio interference) QB is not changed. Following either event, a return is made to block 170.

The movable boundary method has two parameters that are chosen by the user: TB_MIN and TC_MIN. These values can be fixed at some nominal values or they can be varied with time as the Y09-93-018 14 2 1 ~ ~ 2 1 1 characteristics of the traffic change. TB_MIN is defined to be the minimum length of the B period when there is at least TB_MIN
traffic waiting to be received in the B period. That is, a minimum bandwidth is preserved for the inbound traffic. The number of slots in the C period is lower bounded by the value TC_MIN. These values are chosen such that TB_MIN + TC_MIN/R < TF.

At the end of each frame (or equivalently at the beginning of a frame), TA, TB and TC are set according to the following strategy, shown in FIG. 8. The base station identifies the regime in which the variables (QA, QB) lies according to the formulas at blocks 150, 151, and 153 and computes TA, TB, and TC according to the formulas at blocks 152, 156, 155, and 154. In the absence of traffic (i.e., QA and ~B are equal to zero), the frame contains an empty A period, an empty B period and a C period with TC = R TF.
Thls sltuatlons occurs when the base station starts broadcasting just after initialization.

To lllustrate how the proposed invention reacts rapidly to traffic changes, consider the following example. Assume that there is "background" stationary traffic such that the base station receives 4 new outbound packets QA for each frame and a global request to receive 4 new inbound packets QB. Further, assume that at time i an outbound traffic peak of 16 extra packets is received by the base station. Later on, at time j, an inbound traffic peak of 16 extra packets is received by the base station. Finally at time k, a combination of inbound and outbound traffic peaks is received by the base station. Table 1 shows how the three period sizes vary with time assuming the following parameter values: TF=16, TB_MIN=2, and TC_MIN=4. For simplicity of illustration, it is assumed that R=l in this example.

The outbound traffic peak is absorbed in 4 frames, the inbound traffic peak is absorbed in 4 frames and their combination is absorbed in 8 frames. Some techniques in the prior art rely on fixed size periods and do not allow the absorption of the traffic peak so quickly. For instance, if TA and TB are kept fixed at 6 slots, then the time required to absorb the inbound or outbound traffic peak is 8 frames (twice as long as for the movable boundary method).

Y09-93-018 15 2 1 ~ ~ 2 1 ~

Table 1. Illustration of period ~ize adjustment Time QA QB TA TB TC
:
i-2 4 4 4 4 16 i-l 4 4 4 4 16 i 20 4 10 2 8 i+l 14 6 10 2 8 i+2 8 8 8 4 8 i+3 4 8 4 8 8 i+4 4 4 4 4 16 ~-1 4 4 4 4 16 j+l 4 16 4 8 8 j+2 4 12 4 8 8 j+3 ~ 8 4 8 8 j+4 4 4 4 4 16 k-l 4 4 4 4 16 k 20 20 10 2 8 k+l 14 2Z 10 2 8 k+2 8 24 8 4 8 k+3 4 24 4 8 8 k+4 4 20 4 8 8 k+5 4 16 4 8 8 k+6 4 12 4 8 8 k+7 4 8 4 8 8 ~+8 4 4 4 4 16 . , . , . ; -.; , : :

Y09-93-018 16 2 1 ~ ~ 2 1 1 Estimation Method for the Nu~ber of Active Remote Stations Using feedback information from the remote stations (i.e., the retry bit), an adaptive algorithm running at the base station is used to adjust the estimate of the number of remote stations, K, that are attempting to transmit (i.e., are active) during the C
period. This parameter is used by the base station to determine the probability of transmission, p, according to the formula K =
l/p. This choice for p can be shown to maximize throughput in a slotted Aloha system. As was described in the protocol system description, the probability p is used by the remote stations in their stochastic decision to transmit or not in a given mini-slot of the C period.

The key attributes of this method are as follows:

The method is centralized at the base station. Most previously disclosed algorithms use backoff strategies in which a distributed algorithm is run at each of the remote stations.

The method uses two pieces of information to estimate K, 1. A measurement of the probability of successful transmission in a C slot. Specifically, in a frame, the ratio of the number of C slots in which a successful transmission occurs to the total number of C slots is computed.

2. A measurement of the probability that a remote station succeeds on its first attempt in a C slot given that it has succeeded. This is the ratio of the C slots in which a remote succeeds for the first time to the total number of C slots in which successful transmissions occur in the frame. The fact that the success was the first try of a remote station is communicated by a retry bit in the header of the packet that is sent from the remote to the base station.

A smoothing filter is used because of the highly varying Y09-93-018 17 21 ~5211 nature of the above two measurements.

The estimate of K is updated infrequently using the same time constant as the smoothing filter.

When the base station detects that many received packets have been retried, it increases the estimated value of K (i.e., decreases the p value used by the remote stations) to decrease the number of collisions and hence increase the throughput. Alternatively, when the base station sees that only a small fraction of the packets have been retried, it decreases the value of K (i.e., increases the p value) to decrease the number of idles (i.e., slots in which no remote station attempts to transmit) and hence increase the throughput. In the described estimation algorithm, the base station increases or decreases the estimate of K by powers of 2 and 1/2, respectively.

Performance analyses have shown that using the set of five K
values: 2, 4, 8, 16, and 32 (e~uivalently, five p values corresponding to the reciprocals of the listed K values), results in little loss of per~ormance when the number of the remote stations i8 less than about 45. The techni~ue can, of course, be extended to situations in which there are a larger number of remote stations than 45 by using larger powers of two (i.e., 64, 128, etc.). The motivation for using powers of two is that such p values can be easily implemented at the remote stations using a simple Bernoulli random variable generator that is described later.

The K estimation method of FIG. 9 must determine which value of p to use: l/2, 1/4, 1/8, 1/16, or 1/32. An index, I, is used to identify which value of p = 1/K is being used. Thus, I takes on values 1,..., 5, where p = (1/2)l and K = 2l. This estimation method is executed in the base station at the end of each frame as is shown at block 108 of FIG. 4. At the beginning of the C period, the base station sets two counters to zero, a NSUC counter and a NFRSTS counter. The NSUC counter is incremented by one for each C
slot that results in a successful reception of a packet by the base station. Similarly, the NFRSTS counter is incremented by one for each C slot that results in a successful packet reception in which the a retry bit is set to zero. That is, the packet header includes a control bit called the retry bit that is zero if the Y09-93-018 18 ~ 2 1 1 packet is being sent for t~le first time and is one if the packet has been retried one or more times. Thus, NFRSTS is the number of first packet transmissions that are successful in a given C period.
These two pieces of information along with the length of the C
period, TC, are used to compute two probability measures: 1) the probability of success, PSMEAS, and 2) the probability of first success, PFMEAS. As shown in block 200, PSMEAS and PFMEAS are computed. At block 201, a determination is made if NSUC is greater than zero. If so, in block 202, PSMEAS is computed according to the equation, PSMEAS = NSUC / T5. It is assumed that TC > O, but PSMEAS could be set to O if TC = O. Further in block 202, PFMEAS
is computed by the equation, PFMEAS = NFRSTS/NSUC. If NSUC is zero at the end of the frame, then PFMEAS is set to zero. This decision to set PFMEAS to zero corresponds to an assumption of many remote ~tations rather than none in a situation where NSUC = O. If NSUC is not greater than zero, as tested at block 201, then PSMEAS and PFMEAS are each set equal to zero in block 203.

It has been observed that the measured values, PSMEAS and PFMEAS, vary greatly from frame to frame even when the number of active remote stations is constant. This variation requires the use of the smoothing filter in block 204 to generate more reliable mea~urements of the probability of success and first success. The following recursive filtering equations provide a new smoothed estimate at the end of the current frame time given the last ~moothed estimate at the end of the previous frame time and the current measurement:

PSHAT = (l-ALPHA) PSHAT + ALPHA PSMEAS
PFHAT = (l-ALPHA) PFHAT + ALPHA PFMEAS

PSHAT and PFHAT are the filtered estimates of the probability of success and first success, respectively. When the base station is initialized, the values of PSHAT and PFHAT are initialized to zero.

Simulation results indicate that a value of ALPHA = 1/8 yields adequate smoothing properties. This value of ALPHA corresponds to a filter time constant of 7.5 frame times. Other filtering techniques are possible including sliding windows methods. An advantage of the filtering equations shown above is that they give more weight to recent measurements than older ones whereas simple Y09-93-018 19 ~ 2 1 1 sliding window techniques treat all data in the window with equal weight.

Since the required filter introduces an effective lag of about 8 time frames, the estimate of K should only be updated this often.
The parameter TIMEL denotes the period of the K parameter updates in units of time frames. A good choice for TIMEL is 1/ALPHA or TIMEL = 8 time frames for the proposed choice of ALPHA. Thus, the value of p = l/K is kept constant for 8 time frames during which new information is gathered for making the next estimate. If the value of TIMEL is chosen to be much smaller than 1/ALPHA, very oscillatory behavior can result. This infrequent update procedure is implemented in blocks 205, 206 and 207. When the base station is initialized, the frame counter J is initialized to zero in block 207. Thus, for the first TIMEL-1 frames, the initial I is not changed, but at the end of the TIMEL-th frame, the frame counter value J i~ reset and the I value is updated in block 208. The procedure that is used for choosing I in block 208 is shown in FIG.
10 where the values of the discrete functions PSMIN(I), PFUP(I), and PFDWN(I) are shown in Table 2. When the base station is initialized, the value of I is initially set to one corresponding to an initial K value of 2l as shown in block 209.

Given that a certain value of I has been used in the past, the K
e~timation method uses the current estimates, PSHAT and PFHAT, to determine whether to use I-l, I, or I+l for the next group of TIMEL
frame~ according to the procedure of FIG. 10. If PSHAT > PSMIN(I) at block 210, then no action i~ taken meaning that the current I
value continue~ to be used. If PSHAT < PSMIN(I), then three po~ible ~ituations occur depending on the value of PFHAT:

1. If PFHAT < PFUP(I) at block 211, then the value of I is increased by 1 at block 213 corresponding to a doubling of K.
2. If PFUP(I) < PFHAT < PFDWN(I) at block 212, then the value of I is not changed, and a return is made to block 210.
3. If PFDWN(I) < PFHAT in block 212, then the value of I is decreased by 1 in block 214, corresponding to a halving of K.

Y09-93-018 20 ~ 2 L l Analytic results have been used to compute the function values shown in Table 2. These results are based on the analysis of a slotted Aloha system with a constant number of active remote stations.

Table 2. Function values for estimation method.
I PSMIN(I) PFUP(I) PFDWN(I) 1 0.414 0.306 1.0 2 0.377 0.274 0.612 3 0.361 0.261 0.549 4 0.354 0.256 0.523 0.350 0.0 0.511 Note that PFDWN(I) has been set to one to indicate that I cannot be decreased below one, which corresponds to K = 2. Further, PFUP(5) has been set to zero since I cannot be increased beyond 5, which corresponds to K = 32.

The ba~ic rule that is embedded in the estimation method is to use a large K corresponcling to a small p in situations where the estimator has little reliable information. For example, if NSUC is zero for several frames this could be due to two situations: 1) there are no active remote stations, or 2) there are many active remote stations, but they are all colliding due to the use of too large a p value. Since the estimation method sets NFRSTS e~ual to zero in this situation, it is implicitly assuming that case 2 is the cause of NSUC being zero. This is the preferred behavior, since it is better to overestimate rather than underestimate the number of active remote stations. Similarly, if there are many errors due to the radio media, the K estimation method will tend to overestimate the number of active remote stations. Again, given the lack of information, this is the preferred behavior.

A brief explanation of the procedure for obtaining the values listed in Table 2 is provided~ In a slotted Aloha system, it can be shown that the probability of a successful transmission occurring in a slot, PS, is given by PS(K,p)=K p(1-p)(K-1). This Y09-93-018 21 21~2~

value and hence throughput can be maximized by using a value of p=1/K for each K value. Recall that in the method of the invention, p takes on one of the following five values: 1/2, 1/4, 1/8, 1/16, or 1/32, where each value corresponds to a different I value. To compute when to switch from one p value to the next, the equation for PS is used to find the values of K that yield equal values of PS for different adjacent values of p. For the five p values shown, these intersection points occur at K values of 2.71, 5.50, 11.05, and 22.14. Thus, if the number of stations is between 6 and 11, a p value of 1/8 should be used to maximize PS whereas if the number of stations is between 12 and 22, a p value of 1/16 should be used. These intersection points occur at Kint(I)=ln(1/2)/ln((1-(1/2)I)/(1-(1/2)~l+l)))+1 between the curves for p=(1/2)I and p=(1/2)~l+1). The value of PS at these intersection points is used to compute PSMIN(I) in Table 2 where PSMIN(I)=PS(Kint(I),(1/2)I).

To compute the PFUP and PFDWN values in Table 2, compute the probability of a first success, PF, given that a success has occurred, which is given by PF.((K,p),~ p)~K-l) for a slotted Aloha system. Using this e~uation, it is found that PFUP(I)=PF(Kint(I),(1/2)I) for I=1, 2, 3 and 4. Further, PFDWN(I)=PF(Kint(I-1),(1/2)I) for I=2, 3, 4 and 5.

Bernoulli R~n~o Varl~ble Generator Computationally efficient mechanisms are described below for generating Bernoulli random variables given a value of p. A
Bernoulli random variable is 1 with probability p and 0 otherwise.
The invented schemes achieve their computational simplicity by restricting the values of p to certain discrete values. A stream of random bits is generated in which the values 0 and 1 appear with equal probability. There are several known ways to approximately generate such a stream of random bits. In the approach of this invention, as shown in FIG. 11, a shift register 301 with a linear feedback mechanism is used (see block 301 of FIG. 11). During each clock cycle of the shift register, the binary sum of the indicated register bits is computed as shown by the summation points 300 and shifted into the register 301 as indicated by the arrows. The bits in the various positions of the shift register are readable for use as an address in the look-up table 302.

yo9-93-018 22 ~11 5 2 1 1 In this example, the taps on the shift register correspond to the use of a primitive polynomial that achieves a maximal length sequence from the shift register. In the example shown in FIG. 12, the polynomial, y8 + y4 + y3 + y2 + y + 1 is used. In this case, the shift register sequence does not repeat for 28- 1 or 255 clock cycles. Longer shift register lengths may be used to generate longer length sequences. When the shift register is initialized, at least one non-zero value must be loaded into a bit of the register. To prevent stations that have been started simultaneously from generating the same sequence of random bits, the shift registers of different stations can be initialized with a value that is derived from its unique equipment identification tag (e.g., the 48-bit MAC address used in the IEEE 802 standards).

Two mechanisms that use the aforementioned random bit stream for generating Bernoulli random variables are described. In the first mechanism of FIG. 11 table 302 takes i bits from the shift register 301 and can thus generate Bernoulli random variables for p=j/21, where j=l, 2, ..., 2i _ 1. For example, with i=5, the look-up table method can generate Bernoulli random variables for p=l/32, 2/32, ..., 31/32. An example is shown for generating the transmit signal for a p value of 5/32, which is indicated at signal line 303. In the table in blolck 302, the five-bit address value is determined by the five binary signals Xl, X2, X3, X4, and X5that are obtained from the shift register 301. For each address value, the stored binary value that is used to generate the signal on line 303 i8 shown. Only five of the 32 equally-likely addresses are set to one to generate the transmit signal for a p value of 5/32. Note that the shift register 301 must be shifted by i bits for each Bernoulli random variable that is generated. Even greater computational simplicity can be achieved with a smaller set of p values as shown in the following mechanism.

In the second mechanism of FIG. 12, a Bernoulli random variable is generated for p=(l/2)~ with integer m, by using a logical AND
operation such as gate 352 on m bits from the random bit stream.
For the case that was considered in the K estimation method, m values of 1, 2, 3, 4, and'5 were used. Thus, for each C period slot, the shift register needs to be clocked by m bits (up to five).

Claims (50)

1. In a digital data radio communication system, the combination comprising:

a plurality of remote stations, each of which includes a transceiver;

a base station having a transceiver for radio communications with the transceivers of each of said plurality of remote stations, said base station including:

means for defining a plurality of frames during which messages and data are transmitted, each of said plurality of frames being divided into three intervals, the first interval for transmission from said base station to said plurality of remote stations, the second interval for contention free transmission from said plurality of remote stations to said base station, and the third interval for contention access by said plurality of said remote stations for transmission to said base station; and means for including control indicia in a transmission from said base station to a given remote station that is indicative of the probability of said given remote station gaining access during said third interval.
2. The combination claimed in claim 1, wherein said third interval is divided into a plurality of sub-intervals in each of which a remote station may contend for access to transmit to said base station, and wherein said control indicia includes the probability of a remote station gaining access in a given sub-interval of said third interval.
3. The combination claimed in claim 2, including:

means for providing an indication in a transmission from a remote station to said base station of whether or not a given transmission of data is a retransmission.
4. The combination claimed in claim 3, including:

means for computing said control indicia as a function of said indication in a transmission from each of said remote stations in a given frame.
5. The combination claimed in claim 4, wherein said control indicia is recomputed from one frame to the next.
6. The combination claimed in claim 1, including means for changing said control indicia from one frame to the next as a function of an estimate of the number of remote stations contending for access.
7. The combination claimed in claim 6, wherein said third interval is divided into a plurality of sub-intervals in each of which a remote station may transmit to said base station, and wherein said means for changing said control indicia includes:

means for computing said control indicia as a function of the ratio of the number of sub-intervals in which a successful transmission from a remote station to the base station occurs relative to the total number of sub-intervals.
8. The combination claimed in claim 7, wherein said means for changing said control indicia includes:

means for computing said control indicia as a function of the ratio of the number of sub-intervals in which a remote station succeeds on its first attempt to transmit to the base station relative to the total number of remote stations that succeeded in an attempt to transmit to the base station.
9. The combination claimed in claim 6, wherein each of said frames are of a fixed length, including means for varying the duration of each of said three intervals as a function of the message traffic load of the system.
10. The combination claimed in claim 9, including:

means for insuring that said third interval has a predetermined minimum duration.
11. The combination claimed in claim 10, including:

means for insuring that the second interval transmission time is greater than a minimum of a predetermined threshold or the transmission time for scheduled traffic in the second interval, and means for insuring that the first interval transmission time has priority over the second interval transmission time that exceeds said minimum.
12. The combination claimed in claim 9, wherein each of the three intervals are divided into slots, where the slot sizes in the first and second intervals are equal in size and are referred to as regular sized slots and each accommodates one wireless data packet, and the slots in the third interval are mini-slots which axe smaller by a predetermined factor than the slots in the first and second interval, with each such mini-slot accommodating one control packet.
13. The combination claimed in claim 12, wherein the number of slots in the first, second and third intervals are TA, TB and TC, respectively, and said predetermined factor is the ratio of the regular sized slots relative to the mini-slots, with this ratio being referred to as R:1.
14. The combination claimed in claim 13, including:

means for computing TA, TB and TC for a fixed frame size TF, according to the constraint: TF = TA + TB + TC/R
15. In a digital data radio communications system the combination comprising:

a plurality of remote stations, each of which includes a transceiver;

a base station having a transceiver for radio communications with the transceivers of each of said plurality of remote stations, said base station including:

means for defining a plurality of frames of fixed frame length, each of said frames being divided into three periods A, B
and C with each period being divided into slots, including headers, with the slot sizes in the A and B periods being equal in size and being referred to as regular sized slots, and each accommodating one wireless data packet, with the slots in the C period being mini-slots which are smaller by a predetermined factor than the slots in the A and B periods, with each such mini-slot accommodating one wireless control packet, with the A period being for communications from said base station to said plurality of remote stations, the B period being for allocated communications from said plurality of remote stations to said base station, and the C period being for access by contention for communications from said remote stations to said base station;

means for varying each of the A, B and C periods as a function of message traffic load on the system; and means for including control indicia in at least one of the A, B and C periods that is indicative of the probability of a remote station gaining access for communication to said base station in the C period, including means for changing said control indicia from one frame to the next as a function of an estimate of the number of remote stations contending for access.
16. The combination claimed in claim 15, wherein said control indicia includes the probability of a remote station gaining access in a given mini-slot in the C period.
17. The combination claimed in claim 16, including:

means for providing an indication in a transmission from a remote station to said base station of whether or not a given transmission of data is a retransmission.
18. The combination claimed in claim 17, including:

means for computing said control indicia as a function of said indication in a transmission from each of said remote stations in a given frame.
19. The combination claimed in claim 15, including:

means for computing said control indicia as a function of the ratio of mini-slots in which a successful transmission from a remote station relative to the base station occurs relative to the total number of mini-slots.
20. The combination claimed in claim 19, including:

means for computing said control indicia as a function of the ratio of the number of mini-slots in which a remote station succeeds on its first attempt to transmit to the base station relative to the total number of remote stations that succeed in an attempt to transmit to the base station.
21. The combination claimed in claim 20, including:

means for insuring that said C period has a predetermined minimal duration.
22. The combination claimed in claim 21, including:

means for insuring that said B period transmission time is greater than a minimum of a predetermined threshold or the transmission time for scheduled traffic in the B period; and means for insuring that said A period transmission time has priority over said B period transmission time that exceeds said minimum.
23. The combination claimed in claim 20, wherein the number of slots in periods A, B and C are TA, TB and TC, respectively, and said predetermined factor is the ratio of the regular sized slots relative to the mini-slots, with this ratio being referred to as R:1.
24. The combination claimed in claim 23, including:

means for computing TA, TB and TC for a fixed frame size TF, according to the constraint:

TF = TA + TB + TC/R
25. A method of operating a digital data radio communication system which includes a plurality of remote stations, each of which includes a transceiver, and a base station having a transceiver for radio communications with the transceivers of each of said plurality of remote stations, said method comprising the steps of:

defining a plurality of frames, at said base station, during which messages and data are transmitted, each of said plurality of frames being divided into three intervals, the first interval for transmission from said base station to said plurality of remote stations, the second interval for contention free transmission from said plurality of remote stations to said base station, and the third interval for contention access by said plurality of remote stations for transmission to said base station; and including control indicia in a transmission from said base station to a given remote station that is indicative of the probability of said given remote station gaining access during said third interval.
26. The method claimed in claim 25, wherein said third interval is divided into a plurality of sub-intervals in each of which a remote station may contend for access to transmit to said base station, and wherein said control indicia includes the probability of a remote station gaining access in a given sub-interval of said third interval.
27. The method claimed in claim 26, including the step of:

providing an indication in a transmission from a remote station to said base station of whether or not a given transmission of data is a retransmission.
28. The method claimed in claim 27, including the step of:

computing said control indicia as a function of said indication in a transmission from each of said remote stations in a given frame.
29. The method claimed in claim 28, wherein said control indicia is recomputed from one frame to the next.
30. The method claimed in claim 25, including the step of:

changing said control indicia from one frame to the next as a function of an estimate of the number of remote stations contending for access.
31. The method claimed in claim 30, wherein said third interval is divided into a plurality of sub-intervals in each of which a remote station may transmit to said base station, wherein said step of changing said control indicia includes the step of:

computing said control indicia as a function of the ratio of the number of sub-intervals in which a successful transmission from a remote station to the base station occurs relative to the total number of sub-intervals.
32. The method claimed in claim 31, wherein said step of changing said control indicia includes the step of:

computing said control indicia as a function of the ratio of the number of sub-intervals in which a remote station succeeds on its first attempt to transmit to the base station relative to the total number of remote stations that succeed in an attempt to transmit to the base station.
33. The method of claim 32, wherein each of said frames are of a fixed length, including the step of:

varying the duration of each of said three intervals as a function of the message traffic load of the system.
34. The method claimed in claim 33, including the step of:

insuring that said third interval has a predetermined minimum duration.
35. The method claimed in claim 34, including the steps of:
insuring that the second interval transmission time is greater than a minimum of a predetermined threshold or the transmission time for scheduled traffic in the second interval; and insuring that the first interval transmission time has priority over the second interval transmission time that exceeds said minimum.
36. The method of claim 33, wherein each of the three intervals are divided into slots, where the slot sizes in the first and second intervals are equal and are referred to as regular sized slots, and each accommodates one wireless data packet, and the slots in the third interval are mini-slots which are smaller by a predetermined factor than the slots in the first and second interval, with each such mini-slot accommodating one control packet.
37. The method claimed in claim 36, wherein the number of slots in the first, second and third intervals are TA, TB and TC, respectively, and said predetermined factor is the ratio of the regular sized slots relative to the mini-slots, with this ratio being referred to as R:1.
38. The method claimed in claim 37, including the step of:

computing TA, TB and TC for a fixed frame size TF, according to the constraint TF = TA + TB + TC/R.
39. A method of operating a digital data radio communications system which includes a plurality of remote stations, each of which includes a transceiver, and a base station having a transceiver for radio communications with the transceivers of each of said plurality of remote stations, said method comprising the steps of:

defining a plurality of frames, at said base station, of fixed frame length, each of said frames being divided into three periods A, B and C with each period being divided into slots, including headers, with the slot sizes in the A and B periods being equal in size and being referred to as regular sized slots, and each accommodating one wireless data packet, with the slots in the C
period being mini-slots which are smaller by a predetermined factor than the slots in the A and B periods, with each such mini-slot accommodating one wireless control packet, with the A period being for communications from said base station to said plurality of remote stations, the B period being for allocated communications from said plurality of remote stations to said base station, and the C period being for access by contention for communications from said remote stations to said base station;

varying the duration of each of the A, B and C periods as a function of message traffic load on the system; and including control indicia in one of the A, B and C periods that is indicative of the probability of a remote station gaining access for communication to said base station in the C period, including means for changing said control indicia from one frame to the next as a function of the number of remote stations contending for access.
40. The method claimed in claim 39, wherein said control indicia includes the probability of a transmission by a remote station gaining access in a given mini-slot in the C period.
41. The method claimed in claim 40, including the step of:

providing an indication in a transmission from a remote station to said base station of whether or not a given transmission of data is a retransmission.
42. The method claimed in claim 41, including the step of:

computing said control indicia as a function of said indication in a transmission from each of said remote stations in a given frame.
43. The method claimed in claim 42, including the step of:

computing said control indicia as a function of the ratio of mini-slots in which a successful transmission from a remote station to the base station occurs relative to the total number of mini-slots.
44. The method claimed in claim 43, including the step of:

computing said control indicia as a function of the ratio of the number of mini-slots in which a remote station succeeds on its first attempt to transmit to the base station relative to the total number of remote stations that succeed in an attempt to transmit to the base station.
45. The method claimed in claim 44, wherein the number of slots in periods A, B and C are TA, TB and TC, respectively, and said predetermined factor is the ratio of the regular sized slots relative to the mini-slots, with the ratio being referred to as R:1.
46. The method claimed in claim 45, including the step of:

computing TA, TB and TC for a fixed frame size TF, according to the constraint TF = TA + TB + TC/R.
47. The method claimed in claim 47, including the step of:

insuring that said C period has a predetermined minimal duration.
48. The method claimed in claim 39, including the steps of:

insuring that said B period transmission time is greater than a minimum of a predetermined threshold or the transmission time for scheduled traffic in said B period; and insuring that said A period transmission time has priority over said B period transmission time that exceeds said minimum.
49. In a digital data radio communications system the combination comprising:

a plurality of remote stations, each of which includes a transceiver;

a base station having a transceiver for radio communications with the transceivers of each of said plurality of remote stations, said base station including means for defining a plurality of frames during which information is transmitted between said plurality of remote stations and said base station, with a portion of each frame being allocated for contention access by said plurality of remote stations for transmission to said base station;

means for providing an estimation of the number of remote stations that attempt to transmit based on feedback information in transmissions from remote stations in at least a previous frame;
and means for a remote station to determine whether to transmit in a given frame as a function of said estimation.
50. In a digital data radio communications system the combination comprising:

a plurality of remote stations, each of which includes a transceiver;

a base station having a transceiver for radio communications with the transceivers of each of said plurality of remote stations, said base station including means for defining a plurality of frames during which information is transmitted between said plurality of remote stations and said base station, with a portion of each frame being allocated for contention access by said plurality of remote stations for transmission to said base station;

means for providing an indication in a transmission of information from a remote station to said base station of whether or not there has been a previous attempt to transmit this information;

means for providing an estimation of the number of remote stations that attempt to transmit based on said indication in transmissions from remote stations in at least a previous frame;
and means for a remote station to determine whether to transmit in a given frame as a function of said estimation.
CA002115211A 1993-04-19 1994-02-08 Adaptive medium access control scheme for wireless lan Expired - Lifetime CA2115211C (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US049,052 1993-04-19
US08/049,052 US5384777A (en) 1993-04-19 1993-04-19 Adaptive medium access control scheme for wireless LAN

Publications (2)

Publication Number Publication Date
CA2115211A1 CA2115211A1 (en) 1994-10-20
CA2115211C true CA2115211C (en) 1997-09-23

Family

ID=21957816

Family Applications (1)

Application Number Title Priority Date Filing Date
CA002115211A Expired - Lifetime CA2115211C (en) 1993-04-19 1994-02-08 Adaptive medium access control scheme for wireless lan

Country Status (11)

Country Link
US (1) US5384777A (en)
EP (1) EP0621708B1 (en)
JP (1) JP2662181B2 (en)
KR (1) KR0138001B1 (en)
CN (1) CN1115820C (en)
AT (1) ATE199617T1 (en)
BR (1) BR9401518A (en)
CA (1) CA2115211C (en)
DE (1) DE69426788T2 (en)
ES (1) ES2154652T3 (en)
TW (1) TW240358B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105303808A (en) * 2015-11-05 2016-02-03 深圳市深仪兆业科技有限公司 Photoelectric direct reading meter multicast protocol self-adapting method and system

Families Citing this family (210)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5559805A (en) * 1990-12-12 1996-09-24 Gpt Limited Outstation ranging in demand assignment, time division multiple access, communication system
US7924783B1 (en) * 1994-05-06 2011-04-12 Broadcom Corporation Hierarchical communications system
FR2708124B1 (en) * 1993-07-20 1995-09-01 Thomson Csf Method for optimizing the throughput of a time-sharing communication channel.
US5542115A (en) * 1994-06-24 1996-07-30 Pioneer Tech Development Limited Paging method and apparatus
US5502722A (en) * 1994-08-01 1996-03-26 Motorola, Inc. Method and apparatus for a radio system using variable transmission reservation
EP0709982B1 (en) * 1994-10-26 2004-06-30 International Business Machines Corporation Medium access control scheme for wireless LAN using a variable length interleaved time division frame
US5761197A (en) * 1994-11-14 1998-06-02 Northern Telecom Limited Communications in a distribution network
US5592470A (en) * 1994-12-21 1997-01-07 At&T Broadband wireless system and network architecture providing broadband/narrowband service with optimal static and dynamic bandwidth/channel allocation
SE514987C2 (en) * 1995-03-30 2001-05-28 Telia Ab Procedure and apparatus for a telecommunications system for HIPERLAN transmission
US5537395A (en) * 1995-04-13 1996-07-16 Northern Telecom Limited Method and apparatus for setting a channel congestion message in a wireless multiple access packet data system
MX9606669A (en) * 1995-05-04 1997-12-31 Philips Electronics Nv Telecommunication network with improved access protocol.
US5673259A (en) * 1995-05-17 1997-09-30 Qualcomm Incorporated Random access communications channel for data services
US6370135B1 (en) * 1995-06-07 2002-04-09 Cirrus Logic, Inc. Continuous CDPD base station and method of facilitating efficient data transfer
US5638371A (en) * 1995-06-27 1997-06-10 Nec Usa, Inc. Multiservices medium access control protocol for wireless ATM system
US5574728A (en) * 1995-06-27 1996-11-12 Motorola, Inc. Methods of terminal registration
US5729542A (en) * 1995-06-28 1998-03-17 Motorola, Inc. Method and apparatus for communication system access
KR970706673A (en) * 1995-08-09 1997-11-03 요트. 게. 아. 롤페즈 A transmission control method and a communication system between a plurality of stations and corresponding stations,
JP3212238B2 (en) 1995-08-10 2001-09-25 株式会社日立製作所 Mobile communication system and mobile terminal device
EP0758822B1 (en) * 1995-08-11 2006-03-01 Alcatel Method and arrangement for dynamic allocation of bandwidth in a TDM/TDMA network
US5636211A (en) * 1995-08-15 1997-06-03 Motorola, Inc. Universal multimedia access device
US6192053B1 (en) * 1995-09-07 2001-02-20 Wireless Networks, Inc. Enhanced adjacency detection protocol for wireless applications
CN1196145A (en) * 1995-09-11 1998-10-14 摩托罗拉公司 Device, router, method and system for providing hybrid multiple access protocol for users with multiple priorities
EP1768439B1 (en) * 1995-09-20 2010-08-11 NTT Mobile Communications Network, Inc. Access method and mobile station for CDMA mobile communication system
FR2739511A1 (en) * 1995-10-02 1997-04-04 Canon Kk METHODS, APPARATUSES AND SYSTEMS FOR SHARING TRANSMISSION MEDIUM, TRANSMISSION METHOD, COMMUNICATION APPARATUSES AND COMMUNICATION SYSTEMS USING THEM
US6230203B1 (en) 1995-10-20 2001-05-08 Scientific-Atlanta, Inc. System and method for providing statistics for flexible billing in a cable environment
US5966163A (en) * 1995-10-20 1999-10-12 Scientific-Atlanta, Inc. Providing constant bit rate upstream data transport in a two way cable system by scheduling preemptive grants for upstream data slots using selected fields of a plurality of grant fields
DE69627630T2 (en) * 1995-10-23 2003-12-18 Koninkl Philips Electronics Nv TELEPHONE COMMUNICATION NETWORK
CN1110161C (en) * 1995-11-06 2003-05-28 Ntt移动通信网株式会社 System for transmission between base station and exchange of mobile communication using fixed length cell
US5654968A (en) * 1995-12-08 1997-08-05 Multipoint Networks Method and apparatus for managing a number of time slots during which plural bidding devices can request communication access to a central device
CA2166343C (en) * 1995-12-29 1999-08-10 Lee F. Hartley Carrier sense collision avoidance with auto abort
JP3000913B2 (en) * 1996-02-02 2000-01-17 富士ゼロックス株式会社 Data transmission apparatus and method
EP0885506B1 (en) * 1996-03-08 2004-08-04 Siemens Aktiengesellschaft Method and device for transmitting a data packet using ethernet from a first device to at least one other device
US7028088B1 (en) 1996-04-03 2006-04-11 Scientific-Atlanta, Inc. System and method for providing statistics for flexible billing in a cable environment
TW317058B (en) * 1996-04-23 1997-10-01 Ibm Data communication system for a wireless access to an atm network
US6324207B1 (en) 1996-04-29 2001-11-27 Golden Bridge Technology, Inc. Handoff with closed-loop power control
US5953344A (en) * 1996-04-30 1999-09-14 Lucent Technologies Inc. Method and apparatus enabling enhanced throughput efficiency by use of dynamically adjustable mini-slots in access protocols for shared transmission media
US6055268A (en) * 1996-05-09 2000-04-25 Texas Instruments Incorporated Multimode digital modem
US5892769A (en) * 1996-08-28 1999-04-06 Motorola Inc. Method and system for prioritized multiple access using contention signatures for contention-based reservation
EP0828363A3 (en) * 1996-09-04 2000-04-05 Texas Instruments Incorporated Multicode modem with a plurality of analogue front ends
US5805978A (en) * 1996-10-15 1998-09-08 Motorola, Inc. Method and apparatus for overlaying an inbound channel on an outbound system
US6002691A (en) * 1996-10-22 1999-12-14 Zenith Electronics Corporation Dynamic search tree for resolution of contention between transmitting stations
US6016313A (en) * 1996-11-07 2000-01-18 Wavtrace, Inc. System and method for broadband millimeter wave data communication
US5905720A (en) * 1996-11-13 1999-05-18 Motorola, Inc. Method and apparatus for traffic management of inbound communications in a radio communication system
FI101666B1 (en) * 1996-11-29 1998-07-31 Nokia Multimedia Network Terminals Oy The realization of delay-critical services in a cable television system
KR100194577B1 (en) * 1996-12-02 1999-06-15 정선종 Media Access Control Architecture and Method for Wireless ATM Network
US6141336A (en) * 1996-12-13 2000-10-31 International Business Machines Corporation Traffic scheduling method, system and article of manufacture for a wireless access to an asynchronous transfer mode network
US6198728B1 (en) * 1996-12-19 2001-03-06 Phillips Electronics North America Corp. Medium access control (MAC) protocol for wireless ATM
US6034967A (en) * 1996-12-27 2000-03-07 Zenith Electronics Corporation Adaptive random access protocol and dynamic search tree expansion resolution for multiple station networks
US5978382A (en) * 1996-12-27 1999-11-02 Zenith Electronics Corporation Adaptive random access protocol and fixed search tree expansion resolution for multiple station networks
FR2758404B1 (en) * 1997-01-10 1999-03-05 Serge Hethuin SYSTEM FOR MULTIPLEXED ONE-WAY DATA TRANSMISSION FROM A SERIES OF INDIVIDUALS TO A CENTRAL COLLECTION AND ANALYSIS STATION
US6272150B1 (en) 1997-01-17 2001-08-07 Scientific-Atlanta, Inc. Cable modem map display for network management of a cable data delivery system
US6324267B1 (en) 1997-01-17 2001-11-27 Scientific-Atlanta, Inc. Two-tiered authorization and authentication for a cable data delivery system
US6240083B1 (en) * 1997-02-25 2001-05-29 Telefonaktiebolaget L.M. Ericsson Multiple access communication network with combined contention and reservation mode access
US6286058B1 (en) 1997-04-14 2001-09-04 Scientific-Atlanta, Inc. Apparatus and methods for automatically rerouting packets in the event of a link failure
US6091717A (en) * 1997-05-05 2000-07-18 Nokia Mobile Phones Limited Method for scheduling packet data transmission
EP0888021A1 (en) * 1997-06-24 1998-12-30 Motorola, Inc. TDMA communication system with a plurality of base stations in communication with mobile units via a radio interface comprising a dimensionable feedback channel
US6577610B1 (en) * 1997-06-30 2003-06-10 Spacenet, Inc. Flex slotted Aloha transmission system and method
GB9716626D0 (en) * 1997-08-07 1997-10-15 Philips Electronics Nv Wireless network
US6049549A (en) 1997-08-14 2000-04-11 University Of Massachusetts Adaptive media control
WO1999009680A1 (en) * 1997-08-20 1999-02-25 Mitsubishi Denki Kabushiki Kaisha Mobile communication system
AUPO932297A0 (en) * 1997-09-19 1997-10-09 Commonwealth Scientific And Industrial Research Organisation Medium access control protocol for data communications
US6115390A (en) * 1997-10-14 2000-09-05 Lucent Technologies, Inc. Bandwidth reservation and collision resolution method for multiple access communication networks where remote hosts send reservation requests to a base station for randomly chosen minislots
US6681315B1 (en) 1997-11-26 2004-01-20 International Business Machines Corporation Method and apparatus for bit vector array
EP0924896A1 (en) * 1997-12-17 1999-06-23 Hewlett-Packard Company Communicating isochronous and asynchronous data
KR100249814B1 (en) 1997-12-17 2000-04-01 정선종 Method of multiple access for guaranting the reservation request of the real-time band
US6426959B1 (en) 1998-01-20 2002-07-30 Innovative Communications Technologies, Inc. System and method for facilitating component management in a multiple vendor satellite communications network
US6381250B1 (en) 1998-01-23 2002-04-30 Innovative Communications Technologies, Inc. Capacity allocation system using semi-autonomous network elements to implement and control a transmission schedule
US6614779B1 (en) 1998-02-17 2003-09-02 Nortel Networks Limited CDMA physical layer packet mechanisms for distributed bursty traffic
CA2287304C (en) 1998-03-03 2003-10-21 Itron, Inc. Method and system for reading intelligent utility meters
JP3864545B2 (en) * 1998-03-17 2007-01-10 ソニー株式会社 Wireless communication method, communication station and control station
KR100381012B1 (en) 1998-05-04 2003-08-19 한국전자통신연구원 Random connection device for reverse common channel in cdma scheme and method therefor
US6580725B1 (en) * 1998-06-30 2003-06-17 Motorola, Inc. Method and apparatus for dynamic allocation of a messaging system resource
WO2000005904A2 (en) 1998-07-21 2000-02-03 Tachyon, Inc. Method and apparatus for multiple access in a communication system
US6674730B1 (en) 1998-08-04 2004-01-06 Tachyon, Inc. Method of and apparatus for time synchronization in a communication system
US6546001B1 (en) * 1998-08-14 2003-04-08 Samsung Electronics Co., Ltd. Medium access control message acknowledgment system and method of operation thereof
JP4037965B2 (en) * 1998-08-18 2008-01-23 富士通株式会社 Code division multiple access communication system, base station for code division multiple access communication system, terminal apparatus for code division multiple access communication system, code division multiple access communication method, and communication method for terminal apparatus
WO2000016518A2 (en) * 1998-09-11 2000-03-23 Sharewave, Inc. Method and apparatus for controlling communication within a computer network
AU5820899A (en) * 1998-09-11 2000-04-03 Sharewave, Inc. Shadow clients for computer networks
EP1635511B1 (en) 1998-10-05 2009-05-27 Sony Deutschland GmbH Transmission of random access bursts with at least one message part
EP0993211B1 (en) * 1998-10-05 2005-01-12 Sony International (Europe) GmbH Random access channel partitioning scheme for CDMA system
US6747959B1 (en) 1998-10-07 2004-06-08 At&T Corp. Voice data integrated mulitaccess by self-reservation and blocked binary tree resolution
US6963545B1 (en) 1998-10-07 2005-11-08 At&T Corp. Voice-data integrated multiaccess by self-reservation and stabilized aloha contention
US6256483B1 (en) * 1998-10-28 2001-07-03 Tachyon, Inc. Method and apparatus for calibration of a wireless transmitter
JP2000151641A (en) * 1998-11-13 2000-05-30 Sony Corp Transmission control method and transmitter
US6574267B1 (en) * 1999-03-22 2003-06-03 Golden Bridge Technology, Inc. Rach ramp-up acknowledgement
US6169759B1 (en) 1999-03-22 2001-01-02 Golden Bridge Technology Common packet channel
US6606341B1 (en) 1999-03-22 2003-08-12 Golden Bridge Technology, Inc. Common packet channel with firm handoff
FI107306B (en) * 1999-04-13 2001-06-29 Nokia Mobile Phones Ltd Procedure in a wireless data transfer system as well as a wireless data transfer system
DE19919177A1 (en) * 1999-04-28 2000-11-02 Philips Corp Intellectual Pty Network with multiple network clusters for the wireless transmission of packets
US20090219879A1 (en) 1999-05-21 2009-09-03 Wi-Lan, Inc. Method and apparatus for bandwidth request/grant protocols in a wireless communication system
US6925068B1 (en) 1999-05-21 2005-08-02 Wi-Lan, Inc. Method and apparatus for allocating bandwidth in a wireless communication system
US6801513B1 (en) * 1999-06-23 2004-10-05 At&T Wireless Services, Inc. Methods and apparatus for dynamically assigning time slots in a wireless communication system
US6804211B1 (en) 1999-08-03 2004-10-12 Wi-Lan Inc. Frame structure for an adaptive modulation wireless communication system
KR100526508B1 (en) * 1999-08-17 2005-11-08 삼성전자주식회사 apparatus and method for access communicating in cdma communication system
US6865609B1 (en) * 1999-08-17 2005-03-08 Sharewave, Inc. Multimedia extensions for wireless local area network
US6665292B1 (en) 1999-08-27 2003-12-16 Tachyon, Inc. Transmission and reception of TCP/IP data over a wireless communication channel
US6532220B1 (en) 1999-08-27 2003-03-11 Tachyon, Inc. System and method for efficient channel assignment
US6463070B1 (en) 1999-08-27 2002-10-08 Tachyon, Inc. System and method for clock correlated data flow in a multi-processor communication system
US6982969B1 (en) 1999-09-28 2006-01-03 Tachyon, Inc. Method and system for frequency spectrum resource allocation
US6674731B1 (en) 1999-08-27 2004-01-06 Tachyon, Inc. Transmission and reception of TCP/IP data over a wireless communication channel
US6735188B1 (en) 1999-08-27 2004-05-11 Tachyon, Inc. Channel encoding and decoding method and apparatus
US6650636B1 (en) 1999-08-27 2003-11-18 Tachyon, Inc. Transmission and reception of TCP/IP data over a wireless communication channel
US6218896B1 (en) 1999-08-27 2001-04-17 Tachyon, Inc. Vectored demodulation and frequency estimation apparatus and method
US6643318B1 (en) 1999-10-26 2003-11-04 Golden Bridge Technology Incorporated Hybrid DSMA/CDMA (digital sense multiple access/code division multiple access) method with collision resolution for packet communications
SG114476A1 (en) * 1999-11-04 2005-09-28 Ntt Docomo Inc Method, base station and mobile station for timeslot selection and timeslot assignment
US6757319B1 (en) 1999-11-29 2004-06-29 Golden Bridge Technology Inc. Closed loop power control for common downlink transport channels
WO2001039452A1 (en) 1999-11-29 2001-05-31 Golden Bridge Technology, Inc. Closed loop power control for common downlink transport channels
DE60034931D1 (en) 1999-12-09 2007-07-05 Koninkl Philips Electronics Nv COMMUNICATION PROCESS FOR A COMMUNICATION NETWORK WITH MINIMUM CIRCULATION DELAY IN COMPETITION OPERATIONS
US6567396B1 (en) * 1999-12-13 2003-05-20 Telefonaktiebolaget Lm Ericsson (Publ) Adaptive throughput in packet data communication systems using idle time slot scheduling
US6681256B1 (en) 1999-12-21 2004-01-20 Nokia Corporation Method for dynamically selecting allocation of random access channels in a communication system
KR100657253B1 (en) * 2000-03-29 2006-12-14 삼성전자주식회사 Apparatus for transmitting/receiving wireless packet and method thereof
US6807146B1 (en) 2000-04-21 2004-10-19 Atheros Communications, Inc. Protocols for scalable communication system using overland signals and multi-carrier frequency communication
WO2001082500A2 (en) * 2000-04-22 2001-11-01 Atheros Communications, Inc. Methods for controlling shared access to wireless transmission systems and increasing throughput of the same
US7039032B1 (en) 2000-07-14 2006-05-02 At&T Corp. Multipoll for QoS-Driven wireless LANs
US6970422B1 (en) 2000-07-14 2005-11-29 At&T Corp. Admission control for QoS-Driven Wireless LANs
US6999442B1 (en) 2000-07-14 2006-02-14 At&T Corp. RSVP/SBM based down-stream session setup, modification, and teardown for QOS-driven wireless lans
US7151762B1 (en) * 2000-07-14 2006-12-19 At&T Corp. Virtual streams for QoS-driven wireless LANs
US6950397B1 (en) 2000-07-14 2005-09-27 At&T Corp. RSVP/SBM based side-stream session setup, modification, and teardown for QoS-driven wireless lans
US7756092B1 (en) 2000-07-14 2010-07-13 At&T Intellectual Property Ii, L.P. In-band QoS signaling reference model for QoS-driven wireless LANs connected to one or more networks
US6862270B1 (en) 2000-07-14 2005-03-01 At&T Corp. Architectural reference model for QoS-driven wireless LANs
US6804222B1 (en) * 2000-07-14 2004-10-12 At&T Corp. In-band Qos signaling reference model for QoS-driven wireless LANs
US6850981B1 (en) 2000-07-14 2005-02-01 At&T Corp. System and method of frame scheduling for QoS-driven wireless local area network (WLAN)
US7031287B1 (en) 2000-07-14 2006-04-18 At&T Corp. Centralized contention and reservation request for QoS-driven wireless LANs
US7068632B1 (en) 2000-07-14 2006-06-27 At&T Corp. RSVP/SBM based up-stream session setup, modification, and teardown for QOS-driven wireless LANs
US7068633B1 (en) 2000-07-14 2006-06-27 At&T Corp. Enhanced channel access mechanisms for QoS-driven wireless lans
US7298691B1 (en) 2000-08-04 2007-11-20 Intellon Corporation Method and protocol to adapt each unique connection in a multi-node network to a maximum data rate
US7352770B1 (en) 2000-08-04 2008-04-01 Intellon Corporation Media access control protocol with priority and contention-free intervals
US6909723B1 (en) 2000-08-04 2005-06-21 Intellon Corporation Segment bursting with priority pre-emption and reduced latency
US7469297B1 (en) 2000-08-04 2008-12-23 Intellon Corporation Mechanism for using a quasi-addressed response to bind to a message requesting the response
US6987770B1 (en) 2000-08-04 2006-01-17 Intellon Corporation Frame forwarding in an adaptive network
US6907044B1 (en) * 2000-08-04 2005-06-14 Intellon Corporation Method and protocol to support contention-free intervals and QoS in a CSMA network
US7024469B1 (en) 2000-08-28 2006-04-04 Avaya Technology Corp. Medium access control (MAC) protocol with seamless polling/contention modes
US7170904B1 (en) * 2000-08-28 2007-01-30 Avaya Technology Corp. Adaptive cell scheduling algorithm for wireless asynchronous transfer mode (ATM) systems
US6891822B1 (en) * 2000-09-08 2005-05-10 Sharewave, Inc. Method and apparatus for transferring isocronous data within a wireless computer network
JP2002118882A (en) * 2000-10-05 2002-04-19 Shimizu Corp Monitor and control system for managing building
WO2002041520A2 (en) 2000-11-15 2002-05-23 Ensemble Communications, Inc. Improved frame structure for a communication system using adaptive modulation
US6721302B1 (en) * 2000-11-17 2004-04-13 Nokia Corporation Apparatus, and associated method, for communicating packet data in a SDMA (Space-Division, Multiple-Access) communication scheme
JP2002204242A (en) * 2000-12-28 2002-07-19 Hitachi Kokusai Electric Inc Radio communication system
US7555011B2 (en) * 2001-02-16 2009-06-30 University Of Maryland, College Park SEAMA:a source encoding assisted multiple access protocol for wireless communication
US7180855B1 (en) 2001-04-19 2007-02-20 At&T Corp. Service interface for QoS-driven HPNA networks
US7142563B1 (en) 2001-02-20 2006-11-28 At&T Corp. Service interface for QoS-driven HPNA networks
US20020165968A1 (en) * 2001-05-03 2002-11-07 Ncr Corporation Methods and apparatus for wireless operator remote control in document processing systems
US6999441B2 (en) * 2001-06-27 2006-02-14 Ricochet Networks, Inc. Method and apparatus for contention management in a radio-based packet network
US7277413B2 (en) * 2001-07-05 2007-10-02 At & T Corp. Hybrid coordination function (HCF) access through tiered contention and overlapped wireless cell mitigation
CA2354177A1 (en) 2001-07-26 2003-01-26 Waverider Communications Inc. Polling using multiple dynamically updated lists
US7227852B2 (en) * 2001-09-21 2007-06-05 Sony Corporation Wireless transmission system, wireless transmission method, wireless reception method, transmitting apparatus and receiving apparatus
US6987753B2 (en) * 2001-10-09 2006-01-17 Alcatel Canada Inc Apparatus and method for dynamic bandwidth allocation with minimum bandwidth guarantee
EP1311088A1 (en) * 2002-01-11 2003-05-14 Alcatel Method for communicating messages within a wireless network and acces point implementing said method
KR20040102027A (en) * 2002-03-04 2004-12-03 에어 브로드밴드 커뮤니케이션스, 인코포레이티드 Hybrid wireless access bridge and mobile access router system and method
US7756090B2 (en) * 2002-03-12 2010-07-13 Koninklijke Philips Electronics N.V. System and method for performing fast channel switching in a wireless medium
US8432893B2 (en) 2002-03-26 2013-04-30 Interdigital Technology Corporation RLAN wireless telecommunication system with RAN IP gateway and methods
US7724764B2 (en) * 2002-04-23 2010-05-25 Coppergate Communications Ltd. Adaptive synchronous media access protocol for shared media networks
US20030198244A1 (en) * 2002-04-23 2003-10-23 Texas Instruments Incorporated Group polling and reservation requests in a wireless network
AU2003243229A1 (en) * 2002-05-13 2003-11-11 Meg Communications Dba Air Broadband Communications Dsl mobile access router system and method
US8149703B2 (en) * 2002-06-26 2012-04-03 Qualcomm Atheros, Inc. Powerline network bridging congestion control
US7826466B2 (en) * 2002-06-26 2010-11-02 Atheros Communications, Inc. Communication buffer scheme optimized for VoIP, QoS and data networking over a power line
US7120847B2 (en) * 2002-06-26 2006-10-10 Intellon Corporation Powerline network flood control restriction
AU2003284317A1 (en) 2002-10-21 2004-05-13 Intellon Corporation Contention-free access intervals on a csma network
US7411919B2 (en) * 2003-03-17 2008-08-12 University Of Rochester Multi-hop time reservation using adaptive control for energy efficiency
US7764706B2 (en) * 2003-03-20 2010-07-27 University Of Rochester Time reservation using adaptive control for energy efficiency
KR100544481B1 (en) * 2003-05-13 2006-01-24 삼성전자주식회사 Channel time allocation method in high rate WPAN
DE602004023441D1 (en) * 2003-05-16 2009-11-12 Panasonic Corp Media access control in master-slave systems
US7065144B2 (en) 2003-08-27 2006-06-20 Qualcomm Incorporated Frequency-independent spatial processing for wideband MISO and MIMO systems
US8284752B2 (en) * 2003-10-15 2012-10-09 Qualcomm Incorporated Method, apparatus, and system for medium access control
US8462817B2 (en) 2003-10-15 2013-06-11 Qualcomm Incorporated Method, apparatus, and system for multiplexing protocol data units
US8472473B2 (en) * 2003-10-15 2013-06-25 Qualcomm Incorporated Wireless LAN protocol stack
US8842657B2 (en) * 2003-10-15 2014-09-23 Qualcomm Incorporated High speed media access control with legacy system interoperability
US8233462B2 (en) * 2003-10-15 2012-07-31 Qualcomm Incorporated High speed media access control and direct link protocol
US8483105B2 (en) 2003-10-15 2013-07-09 Qualcomm Incorporated High speed media access control
US9226308B2 (en) 2003-10-15 2015-12-29 Qualcomm Incorporated Method, apparatus, and system for medium access control
US7281187B2 (en) 2003-11-20 2007-10-09 Intellon Corporation Using error checking bits to communicated an address or other bits
US8090857B2 (en) * 2003-11-24 2012-01-03 Qualcomm Atheros, Inc. Medium access control layer that encapsulates data from a plurality of received data units into a plurality of independently transmittable blocks
US8903440B2 (en) * 2004-01-29 2014-12-02 Qualcomm Incorporated Distributed hierarchical scheduling in an ad hoc network
US7818018B2 (en) * 2004-01-29 2010-10-19 Qualcomm Incorporated Distributed hierarchical scheduling in an AD hoc network
US7660327B2 (en) * 2004-02-03 2010-02-09 Atheros Communications, Inc. Temporary priority promotion for network communications in which access to a shared medium depends on a priority level
US7715425B2 (en) * 2004-02-26 2010-05-11 Atheros Communications, Inc. Channel adaptation synchronized to periodically varying channel
WO2005089413A2 (en) * 2004-03-17 2005-09-29 Air Broadband Communications, Inc. User movement prediction algorithm in wireless network environment
US8315271B2 (en) * 2004-03-26 2012-11-20 Qualcomm Incorporated Method and apparatus for an ad-hoc wireless communications system
US7564814B2 (en) * 2004-05-07 2009-07-21 Qualcomm, Incorporated Transmission mode and rate selection for a wireless communication system
US8401018B2 (en) * 2004-06-02 2013-03-19 Qualcomm Incorporated Method and apparatus for scheduling in a wireless network
DE602004003933T2 (en) 2004-08-06 2007-04-12 Matsushita Electric Industrial Co., Ltd., Kadoma Feedback control for multicast and broadcast services
US7882412B2 (en) * 2004-10-05 2011-02-01 Sanjiv Nanda Enhanced block acknowledgement
US7881339B2 (en) * 2004-10-06 2011-02-01 Qualcomm, Incorporated Method and apparatus for assigning users to use interlaces in a wireless cellular communication system
EP1686807A1 (en) * 2005-01-27 2006-08-02 Nagra France Sarl Method of load balancing of a management center transmitting informations to a big number of user-units
US7636370B2 (en) * 2005-03-03 2009-12-22 Intellon Corporation Reserving time periods for communication on power line networks
US9240834B2 (en) * 2005-03-22 2016-01-19 Hughes Network Systems, Llc Method and apparatus for providing open loop bandwidth allocation
US7787411B2 (en) * 2005-05-10 2010-08-31 Microsoft Corporation Gaming console wireless protocol for peripheral devices
US7822059B2 (en) 2005-07-27 2010-10-26 Atheros Communications, Inc. Managing contention-free time allocations in a network
US8175190B2 (en) * 2005-07-27 2012-05-08 Qualcomm Atheros, Inc. Managing spectra of modulated signals in a communication network
US8600336B2 (en) * 2005-09-12 2013-12-03 Qualcomm Incorporated Scheduling with reverse direction grant in wireless communication systems
JP4715433B2 (en) * 2005-10-03 2011-07-06 ソニー株式会社 Wireless communication system, wireless communication device, and computer program
KR100615139B1 (en) * 2005-10-18 2006-08-22 삼성전자주식회사 Method and apparatus for allocating transmission period in wireless telecommunication system and therefor system
JP5312734B2 (en) * 2006-09-20 2013-10-09 富士通株式会社 Mobile communication terminal
EP2109944B1 (en) * 2007-01-13 2017-03-08 Samsung Electronics Co., Ltd. Method and system for transmitting and receiving signals using multiple frequency bands in a wireless communication system
MX2009008522A (en) * 2007-02-08 2009-10-12 Xg Technology Inc Heterogeneous mac protocol for forwarding voip traffic on wireless networks.
KR101366332B1 (en) * 2007-04-19 2014-02-21 엘지전자 주식회사 A method of automatic repeat request(ARQ) in communication system
WO2009002032A1 (en) * 2007-06-22 2008-12-31 Lg Electronics Inc. A method of random access and a method of transporting information in broadband wireless access system
WO2008135975A2 (en) * 2007-05-02 2008-11-13 Visonic Ltd. Wireless communication system
BRPI0810271A2 (en) * 2007-05-10 2014-12-30 Xg Technology Inc "METHOD FOR ALLOWING DIRECT COMMUNICATION BETWEEN TWO OR MORE MOBILE HANDS"
ATE545241T1 (en) * 2007-05-10 2012-02-15 Qualcomm Atheros Inc MANAGING DISTRIBUTED ACCESS TO A SHARED MEDIUM
KR101449757B1 (en) * 2008-01-23 2014-10-13 한국전자통신연구원 Apparatus and Method for Random Access in Cellular System
JP5166125B2 (en) * 2008-06-05 2013-03-21 株式会社東芝 Wireless communication apparatus, method and program
US8526460B2 (en) * 2008-10-01 2013-09-03 Harris Corporation Systems and methods for scheduling asynchronous tasks to residual channel space
US8391225B2 (en) * 2009-03-10 2013-03-05 Stmicroelectronics, Inc. Frame based, on-demand spectrum contention destination resolution
CN101959311B (en) * 2009-07-17 2013-03-13 富士通株式会社 Wireless communication device and wireless communication method
WO2011130316A1 (en) 2010-04-12 2011-10-20 Qualcomm Atheros, Inc. Repeating for low-overhead communication in a network
CN101917772A (en) * 2010-08-26 2010-12-15 张若南 Media access control method based on double-buffer area mixed type media access control protocol
US8891605B2 (en) 2013-03-13 2014-11-18 Qualcomm Incorporated Variable line cycle adaptation for powerline communications
US9894581B2 (en) * 2014-01-06 2018-02-13 Intel IP Corporation Apparatus, system and method of access network discovery and selection function (ANDSF) for traffic offloading
FR3077384B1 (en) * 2018-01-30 2020-02-21 Somfy Activites Sa OPERATING METHOD OF A WIRELESS COMMUNICATING ELECTRONIC APPARATUS AND WIRELESS COMMUNICATING ELECTRONIC APPARATUS IMPLEMENTING SAID METHOD

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5888939A (en) * 1981-11-20 1983-05-27 Nec Corp Satellite communication system with packet reservation
US4679187A (en) * 1985-04-22 1987-07-07 International Business Machines Corp. Adaptive trunk-compression system with constant grade of service
EP0202485B1 (en) * 1985-04-22 1993-11-18 Nec Corporation Method of determining optimal transmission channel in multistation communications system
US4907224A (en) * 1986-10-17 1990-03-06 Bydatel Corporation Method for transmitting data in multiple access data communications networks
JP2603081B2 (en) * 1987-08-27 1997-04-23 日本電信電話株式会社 Wireless packet collision control method
US5012469A (en) * 1988-07-29 1991-04-30 Karamvir Sardana Adaptive hybrid multiple access protocols
US5040175A (en) * 1990-04-11 1991-08-13 Ncr Corporation Wireless information transmission system
US5123029A (en) * 1991-06-21 1992-06-16 International Business Machines Corporation Broadcast-initiated bipartite frame multi-access protocol
US5241542A (en) * 1991-08-23 1993-08-31 International Business Machines Corporation Battery efficient operation of scheduled access protocol

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105303808A (en) * 2015-11-05 2016-02-03 深圳市深仪兆业科技有限公司 Photoelectric direct reading meter multicast protocol self-adapting method and system

Also Published As

Publication number Publication date
EP0621708A2 (en) 1994-10-26
DE69426788T2 (en) 2001-08-02
CA2115211A1 (en) 1994-10-20
KR0138001B1 (en) 1998-07-01
EP0621708B1 (en) 2001-03-07
DE69426788D1 (en) 2001-04-12
TW240358B (en) 1995-02-11
CN1115820C (en) 2003-07-23
ES2154652T3 (en) 2001-04-16
JPH0715433A (en) 1995-01-17
ATE199617T1 (en) 2001-03-15
BR9401518A (en) 1994-12-27
JP2662181B2 (en) 1997-10-08
CN1100857A (en) 1995-03-29
US5384777A (en) 1995-01-24
EP0621708A3 (en) 1995-08-23

Similar Documents

Publication Publication Date Title
CA2115211C (en) Adaptive medium access control scheme for wireless lan
EP0709982B1 (en) Medium access control scheme for wireless LAN using a variable length interleaved time division frame
EP1109356B1 (en) Collision-free multiple access reservation scheme for burst communications using a plurality of frequency tones
JP4813679B2 (en) Communication apparatus and communication method
EP1597603B1 (en) Method and apparatus for transmitting information within a communication system
US7974302B2 (en) Hybrid implicit token carrier sensing multiple access/collision avoidance protocol
US6636496B1 (en) Packet data communication device and method in mobile communication system
Baldwin et al. A real-time medium access control protocol for ad hoc wireless local area networks
US20020093929A1 (en) System and method for sharing bandwidth between co-located 802.11a/e and HIPERLAN/2 systems
US20060029073A1 (en) Collision avoidance in IEEE 802.11 contention free period (CFP) with overlapping basic service sets (BSSs)
Khurana et al. Performance evaluation of distributed co-ordination function for IEEE 802.11 wireless LAN protocol in presence of mobile and hidden terminals
WO2009108295A2 (en) Contention protocols for wireless medium access in communication networks
JP2005530378A (en) Bandwidth management in wireless networks
Baldwin et al. Packetized voice transmission using RT-MAC, a wireless real-time medium access control protocol
US6031864A (en) Method and system for controlling the time occupation of signalling frequencies in a frequency hopping system
Ahn et al. Soft reservation multiple access with priority assignment (SRMA/PA): A novel MAC protocol for QoS-guaranteed integrated services in mobile ad-hoc networks
WO2002041590A1 (en) Media access control for wireless systems
Joe et al. Reservation csma/ca for multimedia traffic over mobile ad-hoc networks
Kim IEEE 802.11 MAC performance with variable transmission rates
Whitehead Distributed packet dynamic resource allocation (DRA) for wireless networks
Nicopolitidis et al. TRAP: a high performance protocol for wireless local area networks
Wang et al. Channel sharing of competing flows in ad hoc networks
Khan et al. Block Reservation Time Division Multiple Access (BRTDMA) protocol for a high capacity wireless network
Twu et al. Adaptive control strategy for the multi-layer collision resolution protocol
Salles et al. A new multiple access protocol for multimedia wireless networks

Legal Events

Date Code Title Description
EEER Examination request
MKEX Expiry

Effective date: 20140210