CA2256282A1

CA2256282A1 - Integrated data centric network (idcn)

Info

Publication number: CA2256282A1
Application number: CA002256282A
Authority: CA
Inventors: Patrick Siu; Yair Bourlas; Richard Joseph Nowak; Wendy S. Smith; Wing F. Lo
Original assignee: Northern Telecom Ltd
Current assignee: Individual
Priority date: 1998-06-02
Filing date: 1998-12-17
Publication date: 1999-12-02
Also published as: WO1999063710A1; CN1304606A; BR9910869A; CA2332567A1; US6522641B1; JP2002517948A; CN1129275C; EP1084551A1; JP4817497B2

Description

INTEGRATED DATA CENTRIC NETWORK (IDCN) FIELD OF THE INVENTION
This invention relates to a point-to-point or point-to-multipoint wireless communication system but more particularly, to an integrated data centric network wherein voice data and voice services are integrated on the same network.
BACKGROUND OF THE INVENTION
Currently, multicellular digital telephone systems are being utilized within many of the world's countries, with design elements and principles such as digital modulation techniques, common control channels, dynamic power adjustments and dynamic channel assignment on a per phone call basis being used. The systems typically service portable or mobile users, and are designed for the constraints for the mobile portable environment.
Specifically, these constraints are the use of omni-directional antennae at the mobile/portable site, omni- -directional or sectorized antennae at the cell site, equivalent Rx/Tx patterns at the mobile/portable site, and significant multipathing and delay spreads due to a combination of factors, including cell site and mobile/portable site antennae heights, the movement of the mobile/portable site, and minimum antennae directionality at the mobile/portable site.
Traditional fixed wireless access networks have, in the past, had to use separate networks in order to provide voice and data services to remote customers. In addition, since the intelligence was actually contained within the network, the customer services were actually defined by the network and therefore the services were not portable. These types of networks wherein the intelligence is contained within the network, makes use of dumb terminals and services and features are controlled by the switching centers. Any such services are offered through complex signalling protocols and are therefore slow to be introduced. These types of networks have -, resulted in a high cost of network maintenance for customers.
Accordingly, a need exists for an integrated data centric network wherein voice, data and video services are integrated within the network. In addition, a need exists for integrated data centric network wherein services are defined by the user and enable service portability.
SUi~ARY OF TH8 INVENTION
It is therefore an object of the present invention to provide an integrated data centric network wherein voice,.data and video services are integrated into a single network.
Another object of the present invention is to provide an integrated data centric network wherein user services are defined by the end user by providing middleware to enable user to develop services and applications.
Yet another object of the present invention is to provide an integrated data centric network wherein a carrier grade service is provided with distributed networking and services.
The present invention relates to a point-to-multipoint wireless distribution network for providing seamless communication coverage to a plurality of subscribers, comprising:
a plurality of base stations for providing wireless access to said subscribers;

each base station having connectivity to one another on a first network layer via at least one of a number of ATM switches;
each ATM switch having connectivity to one another over a second network layer via a transport ring thereby enabling one user to communicate directly with another user in said first network layer, or externally of said first network layer via one of said ATM switches.
BRIEF DESCRIPTION OF THE DRAWINGS
Particular embodiments of the invention will be described in association with the following drawings, in which:
Figure 1 is a block diagram of a prior art point-to-multipoint wireless distribution network;
Figure 2 is a block diagram illustrating the transport of voice services over the prior embodiment of Figure 1;
Figure 3 is an illustration of the point-to-multipoint wireless distribution network of the present invention;
Figure 4 illustrates the multiple transport layers for the point-to-multipoint wireless distribution system of the present invention;
Figure 5 is a functional block diagram illustrating the network architecture of the point-to-multipoint wireless distribution system of the present invention;
Figure 6 is a block diagram of the network node equipment used in the architecture of Figure 5; and Figure 7 is a block diagram of the network interface unit used with the network node equipment of Figure 6 in the architecture shown in Figure 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT
In order to facilitate the description of the present invention, the following abbreviations have been used:
ABR available bit rate ALM ATM layer multiplexes AMM ATM multiplexes module AWM ATM Wireless multiplexes NIU Network Interface Unit, a subscriber site device that provides the interface between the customer premise equipment and the wireless access network.

PVC Permanment Virtual Circuit, a PVC is a connection that is set up using administrative procedures.

QOS Quality of service SDM Signal demodulator module SMM Signal modulator module SVC Switched Virtual Circuit, an SVC is connection that is set up using standard signalling procedures.
UBR unspecified bit rate As indicated above, fixed wireless access networks consist of topologies having multiple overlapping cells which provide coverage to an urban, suburban or rural area. The design of overlapping cell structures will depend on the application but should ideally provide for link redundancy for customer sites as well as for the accommodation of new urban structures which may block previously available links.
Those systems that make use of wireless ATM access are designed around the concepts of frequency division multiple access (FDMA) and time division multiple access (TDMA). The FDMA is used for service bandwidths from DS1/E1 and above (i.e. leased lines) and TDMA is used for bursty traffic sources with rates specifically below DS1/E1. TDMA systems are designed to share bandwidth 5 among many users, thus allowing for its greater efficiency -~ when dealing with bursty traffic sources. TDMA systems allow for bandwidth sharing, thereby providing for multiple bursty or low bit rate users to access the channel. TDMA systems share a single demodulator between hundreds of users and are especially appropriate for l0baseT ethernet, Internet and POTS voice applications.
FDMA systems, on the other hand, are designed to provide dedicated bandwidth to a specific user, with those users typically being leased line users that have fairly constant data rate requirements.
Wireless ATM systems allow for the use of broadband microwave infrastructure, thereby making effective use of the multicarrier nature of the broadband microwave system. These multicarrier microwave systems allow for the best mixture of low entry costs of the network operator with flexibility to expand the cell range and traffic handling capabilities.
Typically, at each cell site, there exists a base station consisting of microwave and digital radio equipment. The base station provides the network connections, with the connections being typically OC3 ATM.
Base station microwave equipment is mounted on the top of the building, typically outside, and provides the wireless connection capability to the subscriber.
At the customer premises, outdoor microwave equipment (antenna integrated with transceiver) connects to a network interface. Cell sizes are typically 1-10 kilometers, depending on the frequency of the system operation, availability level which is required by the system operator, and service's performance that is required by the system operator. Generally, the wireless access system is designed to cost effectively support system requiring voice, video and data solutions, in which the number of customers is large enough to warrant a - point-to-multipoint implementation. These types of systems include LMCS (Canada), LMDS (U. S. and worldwide) and MVDS (Europe).
Referring now to Figure 1, we have shown a block diagram of a wireless distribution system according to the prior art. In this configuration, customers receive fixed wireless access to the telephone network via various customer premise equipment. Access is provided by means of a wireless link, communication tower and a base station. An ATM switch.is used to provide access to various multimedia services, such as voice and data. The connection between the base station and the ATM switch might either be done via a leased line or a point-to-point wireless link.
In order for a customer to access one of various services, such as voice, data, the ATM switch requires a connection link to the PSTN (through the public network), a link to NIP network for Internet access or a link to a frame relay network for data communications. Similarly, a link may be provided to access other ATM networks.
In a situation where the subscriber requires access or a link with the PSTN, the ATM switch is required to be connected to the central office switch via a multiplexer and a concentrator as shown in Figure 2.
As illustrated in Figure 2, depending on the customer's site configuration, the customer premise equipment can either be connected to a PBX via lObaseT
ethernet link or an access node via a DS1 link. The customer site is then linked to the base station via a wireless fixed access link. The base station consists of a transmitting/receiving tower and radio equipment which is connected to the ATM switch via either a leased line or a point-to-point wireless link. The ATM switch is then connected to a 3 to 1 multiplexer via a DS3 link. The multiplexer then connects to the concentrator via a DS1 link before being connected to the central office switch via a TRT03 link.
As indicated previously, the shortcomings associated with this existing telecom network is that separate voice and data networks are required depending on the communication needs of the subscriber. Since access to various services may have different owners, customer' services are actually defined by the network as opposed to the customer. Similarly, by the very nature of the network, the service logic resides in the network thereby making service portability difficult to achieve. The transnetwork design is such that the network dictates to the customer the capacity and availability of a communication link to the customer.. In other words, regardless of the needs of the subscriber, the network will deliver what it can, when it can.
Another problem associated with the prior art telecom networks is that the intelligence is contained within the network. That is, subscribers are provided with terminals wherein features and services are controlled by the switching centers. Because the services are offered through complex signalling protocols, operators are slow to introduce new services and applications. Complex interworking functions between protocols are caused by the clear distinction between protocols used within the network and the protocols between users of network elements.

In view of this complexity, service operators do not like giving access to services and transport protocols to prevent any potential network failures. This results in a limited amount of user-to-user signalling. This S complexity further results in a rigid billing structure and a high cost of network maintenance for the operator.
Referring now t4 Figure 3, we have shown a block diagram illustrating the network configuration of the point-to-multipoint wireless distribution network of the present invention. The architecture of Figure 3 provides an integrated data centric network wherein voice, data and video network services become integrated. The network configuration enables service portability as well as user defined services required by individual users. Network parameters and requirements are dictated by a user's needs as opposed to the network needs. Each end user is provided with an intelligent terminal, such as a PC, to enable service logic of the network to reside at the end user's terminal. The network, in effect, provides the middleware to enable users to develop services and applications according to their needs. The network configuration illustrated in Figure 3 represents a hybrid ring and star architecture wherein a plurality of base stations provide wireless access to a plurality of subscribers. Each base station has connectivity to one another on the first network layer via at least one of a number of ATM switches. This enables one user to communicate directly to another user in this first network layer. As illustrated in Figure 4, each ATM switch has connectivity to one another on a second network layer over the hybrid ring.
As illustrated in Figure 4, at the national/regional level, a transport and routing layer is supported by means of multiple ATM switches connected in a ring configuration. Similarly, at the metro distribution level and routing layer, a transport ring and LAN is utilized between base stations with connectivity to ATM
switches to enable access to a higher level of layers.
The routing layer enables a customer to access the ATM
network, IP network, frame relay network or the PSTN
public network via a telephony gateway. The sublayer to the metro distribution and routing layer is the access/last mile layer where the base station communicates over fixed wireless access to multiple customers identified as the customer premises layer.
Referring now to Figure 5, we have shown a block diagram illustrating the network architecture of the point-to-multipoint wireless distribution of the present invention. As indicated above, the distribution level is done on one layer between base stations and ATM switches.
This enables the consolidation of back haul from the base station to ATM switches, thereby optimizing the routing for the distribution network. This configuration enables signalling between base stations, the management of sections, home location register for address of translation/registration is contained within the subnet controller. In the event, that a subscriber or user requires access to an Internet protocol network, the ATM
switch can have direct access to the IP gateway.
Similarly, depending on the user requirement, the ATM
switch can access the frame relay gateway or the telephony gateway for data and voice communication, respectively.
The point-to-multipoint wireless distribution system consists of several major system software and hardware blocks. These are the point-to-multipoint base stations for ATM transport; point-to-point base station equipment for ATM transport; broadcast base station equipment for MPEG2 digital T.V.; customer premise equipment; building interfaces; centralized compression; network operations center.
The point-to-multipoint base station for ATM
transport consists of digital and microwave equipment 5 designed to route ATM cells to appropriate modulators, with the cells being transmitted to the subscriber population. The base station provides both FDMA and TDMA
access alternatives. It supports the encryption on a per BPI/BCI basis, routing based on BPI/BCI basis, ATM

10 signalling interfaces for support of FDC and PVC
connections, open NMS interfaces through the use of FMP
interface standards on all equipment including microwave transmitters and receivers, OC-3c network interfaces. The base stations include both video network to wireless transmission equipment, as well as microwave transmitters, receivers, antennae and common equipment elements.
Referring to Figure 6, we have shown the block diagram configuration of the network node equipment (base station). In the point-to-multipoint mode, the network node equipment may use more than a single chassis.
Bridging between the chassis is achieved through the use of an ATM layer multiplexer. The card required at the base station to provide either point-to-point or point-to-multipoint services are described below. The network node equipment required at the base station is:
(1) transmitter;
(2) receiver;
(3) ATM wireless multiplexer;
(4) ATM layer multiplexer;
(5) signal modulator module; and (6) signal demodulator module.
Figure 6 describes the relationship between the different cards at the base station.

The ATM wireless multiplexer card is illustrated in Figure 6 and labelled as AWM. The AWM card is connected to the ATM network using a standard, sonic UNI
OC-3c connection. The AWM routes ATM cells to a specific SMN based on the VPI/VCI value, as VC functionality is also supported using UNI standard signalling protocol (ATM
Forum 3.1 and ITU CUPE.2931). The wireless controller manages messages better than ATM cells with a well-known VPI/VCI value. The AWN extracts the ATM cells and sends them to the management software. The ATM multiplexer (AMM) card is connected to the ATM network using a standard, SONET UNI OC-3c with either a multi-mode or a single mode fiber connection. The AMM splits the ATM
traffic of the OC-3c link into parallel streams. Each stream is sent to a different modulator. The process of splitting ATM cells into parallel paths is called the unbonding process. In the receive direction, ATM cells from parallel paths are combined into a single stream while preserving cell order and sent to the ATM network over the OC-3c fiber interface. This process is called bonding. In addition, sufficient buffers are provided in the transmit and receive directions so that cell timing is preserved during the bonding and unbonding process.
The next card is the ATM layer multiplexer card (ALM). The ALM card is used to connect two PCI shelves.
The ALM card operates in mated pairs. If the card is inserted into a shelf other than #1, it multiplexes the ATM cells from all the demodulators on the PCI shelf into a single stream and sends the multiplex signal to its mated ALM located in shelf #1. If the ALM is inserted into shelf #1, it receives ATM cells from its mated ALM
and sends these cells to the AWN. Each shelf can optionally be configured with a redundant ALM. If the primary ALM fails, traffic is switched to the redundant ALM.
The interface between the network node element, AWN card or AMM card, and the ATM switch consists of either of the following two interfaces:
(a) a monomode optical fiber OC3/SDM interface;
or (b) a multimode optical fiber OC3/SDM
interface.
The signal modulator module card (SMM) is a wide band modulator with software selectable modulation techniques. Three modulation techniques are supported:
(1) QSPK;
(2) 16-QAM; and (3) 64-QAM.
In addition, each SMM buffer is virtually divided in four buffers to support the traffic required by the ATM Forum and maintain the quality of the cell delay variation. The operation of the SMM is software configurable. The bandwidth of the SMM ranges from 4-11.5 MHz. The SMM
performs the encryption. The signal demodulator module (SDM) provides support for operating the network node element in various operating modes'. The SDM's are software configurable to operate in QSPK, 16-QAM or 64-QAM
for FDMA and DQSPK for TDMA. Examples of demodulators are:
(1) SDM Type 1: A load bandwidth SDMA
demodulator. Bandwidth ranges from 1-5 MHz;
(2) SDM Type 2: A high bandwidth SDMA
demodulator. Bandwidth ranges from 4-11.5 MHz;
(3) SDM Type 3: An FDMA demodulator with bandwidth ranging between 0.39-5 MHz; and (4) SDM Type 4: A TDMA demodulator having a burst mode FDN with 6 MHz bandwidth.

The interface between these demodulators and the ALM is ATM. The demodulators perform the wireless packet to ATM depacketizing and the decrypt functions.
The RF module includes the outdoor equipment that comprises the IF/RF conversion and amplification functions. The base station incorporates the same type of RF functions as the user RF module. While the user RF
module can handle one up link channel and one down link channel at a time, the base station can send and receive several RS channels simultaneously.
The transmitter located at the top of the antennae tower is connected to the combiner by coaxial cable or fiber cable. Within the transmitter, the VHF signal is converted to the network operator. While at the customer premises, a single transceiver/antenna is used, at the base station separate transmitters, receivers and antennae are used to minimize the near and cross-talk effects between transmit and receive signals.
For sectors with multiple downstream channels, a combiner takes the input of several SDM's, up to 8 channels and sends it to a single transmitter. The receiver unit receives the entire sector and down converts the signal to the VHS band. The splitter functionality is exactly the opposite of that of the combiner. In the receive direction, the splitter takes the input from a single receiver and splits the signal among several SDM's.
The number of SDM's attached to a splitter varies according to the configuration and can be as high as 86 SDM's when a sector is configured to offer all the DS1 connections. The splitter operates at VHS frequency range as well.
Broadband filters are provided for channel filtering at the VHS level. These are used within each modulator and demodulator device, where it is at the subscriber modem or at the cell site. This filtering provides high level channel rejection and therefore the system does not use broadband filters, except on specific customer requests.
At the customer premise equipment, cell site acquisition and location is very important in order to provide the maximum coverage while reducing interference.
The cell site choice should provide the maximum coverage while reducing discontinuity. In addition, it should allow for migration toward a frequency reuse as close to 1 as possible. A key issue in choosing the cell site is accessibility for installation and maintenance and the distance from the backbone fiber infrastructure.
Referring now to Figure 7, the relationship between the network interface unit card and the RMM is shown. The number of applications cards per NIU depends on whether it is a commercial NIU or an integrated NIU.
Each network interface unit can operate either in a fixed bandwidth or a dynamic bandwidth mode. The fixed bandwidth cards can operate in PVC or FDC mode and are designed to have an FDMA RN~I. In PVC mode, a fixed bandwidth card is assigned air bandwidth permanently and does not make frequency requests. In FDC mode, a fixed bandwidth card is assigned a fixed bandwidth on request and for the duration of the call. The VS1/V1 card is an example of the fixed bandwidth card.
The dynamic bandwidth NIU is assigned bandwidth on demand. The RN~I attached to the NIU operates in TDMA
mode. The bandwidth allocated for these NIU's is assigned dynamically based on the channel traffic while maintaining the QOS. The network interface unit is configured from a remote terminal using the SNMP protocol, either via a dial-up modem or via an inband connection through the wireless link. The internal interface between the RMM and the application card is ATM based. The RMM keeps a list of all VCC's that terminate on the NIU, and discards all cells that do not match. The RMM also extracts idle cells. Only valid ATM cells (for this NIU) are sent over 5 the PCI bus.
The NIU performs statistical multiplexing of ATM
ATC's while preserving ATM quality of service. Priority buffers are provided for each class of service, where CBR
has the highest priority, seconded by BBR, and lastly, ADR
10 and UBR. Each buffer can hold up to 160 ATM cells per class of service buffer. Additional buffers, which are used to support second level of traffic shaping, are provided on all ABR application cards.
The radio modem module RMM can be integrated into 15 various subscriber network interface units. Two versions of the RMM exist, one for the TDMA and one for FDMA.
Services in an ATM network are provided in accordance with the ATM Forum plus ITU standards.
Services in the wireless ATM network interwork seamlessly with the wireline ATM network.
The key difference between the point-to-point and the point-to-multipoint services is that in the point-to-multipoint (PMP) service, ATM cells are routed to a specific modulator based on the ATM cell header. When configured in the PMP mode, the system is equipped with the AWM card. The AWM card is connected to the ATM
network using a standard,SONET UNI OC-3c with either a multimode or single mode fiber connections. The AWM
routes ATM cells to a specific SNM based on the VPI/VCI
value. SVC functionality is also supported using the UNI
standard signalling protocols (ATM Forum 3.1 and ITU
Q.2931). The wireless control and management messages are imbedded in ATM cells with a well-known VPI/VCI value.

The AWN extracts these ATM cells and sends them to the management software.

Claims

WHAT IS CLAIMED IS:

1. The present invention relates to a point-to-multipoint wireless distribution network for providing seamless communication coverage to a plurality of subscribers, comprising:
a plurality of base stations for providing wireless access to said subscribers;
each base station having connectivity to one another on a first network layer via at least one of a number of ATM switches;
each ATM switch having connectivity to one another over a second network layer via a transport ring thereby enabling one user to communicate directly with another user in said first network layer, or externally of said first network layer via one of said ATM switches.