US20110019628A1

US20110019628A1 - Method and Apparatus for Scheduling Request

Info

Publication number: US20110019628A1
Application number: US12/789,474
Authority: US
Inventors: Li-Chih Tseng
Original assignee: Innovative Sonic Corp
Current assignee: Innovative Sonic Corp
Priority date: 2009-07-23
Filing date: 2010-05-28
Publication date: 2011-01-27
Also published as: ES2721602T3; CN101965021A; EP2282597A1; EP2282598A1; TWI440374B; JP2011030197A; KR20110010053A; TW201127157A; US20110019619A1; TR201905654T4; TW201129159A; PL2282598T3; EP2282598B1; EP2282597B1; ES2395655T3; US8665822B2; KR101176911B1

Abstract

The present invention provides a method of performing Scheduling Request (SR) in a user equipment (UE) of a wireless communication system. The method includes steps of triggering an SR, sending an SR message on a Physical Uplink Control Channel (PUCCH) when the UE has a configured PUCCH resource, and skipping a plurality of subsequent SR transmission opportunities after the SR message is sent.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/228148, filed on Jul. 23, 2009 and entitled “Advanced Transmission and Reception for DRX and SR”, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a method and apparatus for performing Scheduling Request, and more particularly, to a method and apparatus for performing Scheduling Request in a user equipment (UE) of a wireless communication system to reduce unnecessary Scheduling Request transmission when the Scheduling Request is sent in a short periodicity, such that power consumption can be saved.
2. Description of the Prior Art
Long Term Evolution wireless communication system (LTE system), an advanced high-speed wireless communication system established upon the 3G mobile telecommunication system, supports only packet-switched transmission, and tends to implement both Medium Access Control (MAC) layer and Radio Link Control (RLC) layer in one single communication site, such as in base stations (Node Bs) alone rather than in Node Bs and RNC (Radio Network Controller) respectively, so that the system structure becomes simple.
In LTE system, the network, such as an evolved Node B (eNB), performs radio resource allocation to provide user equipments (UEs) with resources for uplink or downlink data transfer. There are two kinds of resource allocations: dynamic resource allocation and pre-configured resource allocation. For the pre-configured resource allocation, the network allocates resource to the UEs by Radio Resource Control (RRC) signaling, and allows the UEs periodically transmitting a certain amount of data, for example, voice data. That means, at periodic time intervals, the UEs can utilize the pre-configured radio resources for data transmission or reception, to achieve data exchange with the network. On the other hand, for the dynamic resource allocation, the network dynamically allocates radio resources to the UEs depending on UE number of the cell area, traffic volume and quality of service (QoS) requirements of each UE, and the UE has to monitor a physical downlink control channel (PDCCH) to find possible allocation of dynamic resources for both downlink and uplink transmission.
For the dynamic resource allocation, when the UE has new uplink data to transmit and there is no Uplink Shared Channel (UL-SCH) resource available, the UE shall trigger a Scheduling Request (SR) procedure to request the network to allocate uplink transmission resources. In such a situation, if the UE has configured Physical Uplink Control Channel (PUCCH) resources, the SR procedure is performed via PUCCH signaling. Otherwise, such as the UE has no configured PUCCH resources or the configured PUCCH resources are invalid, for example, the SR procedure is then performed via a Random Access Procedure. Since the PUCCH resources are dedicated transmission resources, the SR message transmitted on PUCCH is referred to as a Dedicated Scheduling Request (D-SR) message, while the SR message transmitted via the Random Access procedure is referred to as a Random Access Scheduling Request (RA-SR) message.
If the UE has a configured PUCCH resource after an SR is triggered, the UE shall periodically transmit a D-SR message on PUCCH until the SR is cancelled. Note that the SR is cancelled when an uplink transmission resource for a new transmission is received or the number of D-SR transmissions reaches to a pre-defined parameter DSR_TRANS_MAX. When the number of D-SR transmissions reaches to the pre-defined parameter DSR_TRANS_MAX, it indicates uplink transmission of the UE may have some problem, such as the PUCCH resources for SR become invalid (probably due to poor signal quality or improper power settings) or the UE loses synchronization on uplink timing, and thus the D-SR messages sent by the UE cannot be successfully received by the network. In this case, the UE shall stop the D-SR transmission, and trigger a Random Access procedure to transmit the SR message instead.
According to current specifications, a minimum periodicity for sending SR on PUCCH is 5 ms. It means that UE can send an SR on PUCCH every 5 ms. In this case, the average waiting time required by the UE for sending SR on PUCCH is 2.5 ms. For the growing demands on real-time communication services, the waiting time may be too long. Thus, it has been proposed by the industry to consider having a shorter periodicity like 2 or 3 ms. However, when the periodicity is shorter than the time expenditure the eNB requires to handle the SR message or shorter than packet Round Trip Time (RTT), some of the SR transmission is redundant, and causes unnecessary power waste of the UE.

SUMMARY OF THE INVENTION

It is therefore an objective of the present invention to provide a method and apparatus for performing Scheduling Request (SR) in a user equipment (UE) of a wireless communications system.
According to the present invention, a method for performing Scheduling Request (SR) in a user equipment (UE) of a wireless communication system is disclosed. The method includes steps of triggering an SR; sending an SR message on a Physical Uplink Control Channel (PUCCH) when the UE has a configured PUCCH resource; and skipping a plurality of transmission opportunities for sending the SR message after the SR message is sent.
According to the present invention, a communications device for performing Scheduling Request (SR) in a user equipment (UE) of a wireless communication system is disclosed. The communications device includes a processor for executing a program code, and a memory, coupled to the processor, for storing the program code. The program code includes steps of triggering an SR; sending an SR message on a Physical Uplink Control Channel (PUCCH) when the UE has a configured PUCCH resource; and skipping a plurality of transmission opportunities for sending the SR message after the SR message is sent.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a wireless communications system.

FIG. 2 is a function block diagram of a wireless communications device.

FIG. 3 is a diagram of a program code of FIG. 2.

FIG. 4 is a flowchart of a process according to an embodiment of the present invention.

FIG. 5 is an operational diagram of the process of FIG. 4 according to the embodiment of the present invention.

DETAILED DESCRIPTION

Please refer to FIG. 1, which illustrates a schematic diagram of a wireless communications system 10. The wireless communications system 10 is preferred to be a Long Term Evolution (LTE) system, and is briefly composed of a network and a plurality of user equipments (UEs). In FIG. 1, the network and the UEs are simply utilized for illustrating the structure of the wireless communications system 10. Practically, the network may comprise a plurality of base stations (Node Bs), radio network controllers and so on according to actual demands, and the UEs can be devices such as mobile phones, computer systems, etc.
Please refer to FIG. 2, which is a functional block diagram of a communications device 100 in a wireless communications system. The communications device 100 can be utilized for realizing the UEs in FIG. 1, and the wireless communications system is preferably the LTE system. For the sake of brevity, FIG. 2 only shows an input device 102, an output device 104, a control circuit 106, a central processing unit (CPU) 108, a memory 110, a program 112, and a transceiver 114 of the communications device 100. In the communications device 100, the control circuit 106 executes the program 112 in the memory 110 through the CPU 108, thereby controlling an operation of the communications device 100. The communications device 100 can receive signals input by a user through the input device 102, such as a keyboard, and can output images and sounds through the output device 104, such as a monitor or speakers. The transceiver 114 is used to receive and transmit wireless signals, delivering received signals to the control circuit 106, and outputting signals generated by the control circuit 106 wirelessly. From a perspective of a communications protocol framework, the transceiver 114 can be seen as a portion of Layer 1, and the control circuit 106 can be utilized to realize functions of Layer 2 and Layer 3.
Please continue to refer to FIG. 3. FIG. 3 is a schematic diagram of the program 112 shown in FIG. 2. The program 112 includes an application layer 200, a Layer 3 202, and a Layer 2 206, and is coupled to a Layer 1 218. The Layer 3 202 is used for performing resource control. The Layer 2 includes a Radio Link Control (RLC) layer and a Medium Access Control (MAC) layer, and is used for performing link control. The Layer 1 218 is used for performing physical connection.
In LTE system, when the UE has new uplink data to transmit such as uplink data arrives to a transmission buffer of the UE, for example, and there is no Uplink Shared Channel (UL-SCH) resource available, the UE would trigger a Scheduling Request (SR) procedure to request the network to allocate uplink transmission resources, such that the uplink data can be transmitted. Under such a situation, the embodiment of the present invention provides a scheduling request program 220 in the program 112 for avoiding unnecessary transmission of scheduling request messages and saving UE power consumption.
Please refer to FIG. 4, which illustrates a schematic diagram of a process 40 according to an embodiment of the present invention. The process 40 is utilized for performing Scheduling Request (SR) in a UE of a wireless communication system, and can be compiled into the scheduling request program 220. The process 40 includes the following steps:
Step 400: Start.
Step 402: Trigger an SR.
Step 404: Send an SR message on a Physical Uplink Control Channel (PUCCH) when the UE has a configured PUCCH resource.
Step 406: Skip a plurality of SR transmission opportunities after the SR message is sent.
Step 408: End.
According to the process 40, after the SR is triggered, if the UE has configured PUCCH resources, the UE sends an SR message on PUCCH. After the SR message is sent, the UE then skips a plurality of transmission opportunities for sending the SR message. In this case, even a short SR periodicity is used by the UE to transmit the SR message, since the plurality of SR transmission opportunities is skipped each time after the SR message is sent, the embodiment of the present invention is able to reduce unnecessary transmission of the SR message, while the average waiting time for sending the SR message can still be shortened.
If the SR is still pending (i.e. not being cancelled) after the plurality of transmission opportunities is skipped, the UE shall keep on sending the SR message at a next transmission opportunity. Note that the SR is cancelled when an uplink transmission resource for a new transmission is received or the number of times the SR message is sent reaches to a pre-defined parameter DSR_TRANS_MAX.
For example, please refer to FIG. 5. FIG. 5 is an operational diagram of the process 40 according to the embodiment of the present invention. Assume that an SR is triggered due to uplink data arrival at a timing point T1. If the UE has configured PUCCH resources, transmission opportunities for the UE to send an SR message would be periodically formed on PUCCH (timing points T2-T6). The time interval between each transmission opportunity is configured according to periodicity of the PUCCH resource, which can be 1 ms to 4 ms but is not limited to these. In the beginning, the UE sends the SR message at a first transmission opportunity (i.e. at the timing point T2). Then, based on the process 40, the UE skips a plurality of transmission opportunities, such as two transmission opportunities in this case, for example. If the SR is still pending after the plurality of transmission opportunities is skipped, the UE then sends the SR message again at a next transmission opportunity (i.e. at the timing point T5). And, the UE repeats in this manner until the SR is cancelled.
In the present invention, since the plurality of follow-up transmission opportunity is skipped by the UE each time after the SR message is sent, the UE is able to avoid unnecessary transmissions of the SR message till receiving response from the network, so that the power consumption can be saved. Accordingly, the short SR periodicity can still be used by the UE, and thus the average waiting time required by the UE for sending the SR message (i.e. the time interval between the timing points T1 and T2) can be significantly shortened as well.
It is worth noting that appropriate modifications or alternations can be certainly made by those skilled in the art according to practical demands, which all belong to the scope of the present invention. For example, the way that the UE skips the plurality of opportunity can be controlled by a counter or a timer, which is also not restricted by this.
As mentioned above, the embodiment of the present invention provides a method and apparatus for performing scheduling request to avoid unnecessary transmission of the SR message when the UE uses the short SR periodicity, such that power consumption can be saved.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.

Claims

1. A method for performing Scheduling Request (SR) in a user equipment (UE) of a wireless communication system, the method comprising:

triggering an SR;

sending an SR message on a Physical Uplink Control Channel (PUCCH) when the UE has a configured PUCCH resource; and

skipping a plurality of transmission opportunities for sending the SR message after the SR message is sent.

2. The method of claim 1, wherein the SR is triggered when uplink data arrives to a transmission buffer of the UE and there is no uplink transmission resource available.

3. The method of claim 1 further comprising:

keeping on sending the SR message at a next transmission opportunity next to the plurality of transmission opportunities when the SR is still not cancelled.

4. The method of claim 3, wherein the SR is cancelled when the UE receives an uplink transmission resource allocated to a new transmission.

5. The method of claim 4, wherein the uplink transmission resource is an Uplink Shared Channel (UL-SCH) resource.

6. The method of claim 3, wherein the SR is cancelled when the number of times that the SR message is sent reaches to a pre-defined number.

7. The method of claim 1, wherein the number of the plurality of transmission opportunities is determined by a timer.

8. The method of claim 1, wherein the number of the plurality of transmission opportunities is determined by a counter.

9. A communication device for performing Scheduling Request (SR) in a user equipment (UE) of a wireless communication system, the communication device comprising:

a processor for executing a program code; and

a memory coupled to the processor for storing the program code;

wherein the program code comprises:

triggering an SR;

10. The communication device of claim 9, wherein the SR is triggered when uplink data arrives to a transmission buffer of the UE and there is no uplink transmission resource available.

11. The communication device of claim 9, wherein the program code further comprises:

keeping on sending the SR message at a transmission opportunity next to the plurality of transmission opportunities when the SR is still not cancelled.

12. The communication device of claim 11, wherein the SR is cancelled when the UE receives an uplink transmission resource allocated to a new transmission.

13. The communication device of claim 12, wherein the uplink transmission resource is an Uplink Shared Channel (UL-SCH) resource.

14. The communication device of claim 11, wherein the SR is cancelled when the number of times that the SR message is sent reaches to a pre-defined number.

15. The communication device of claim 9, wherein the number of the plurality of transmission opportunities is determined by a timer.

16. The communication device of claim 9, wherein the number of the plurality of transmission opportunities is determined by a counter.