Abstract:
A communication device for handling scheduling request (SR) transmissions comprises a storage unit for storing instructions and a processing circuit coupled to the storage unit. The processing circuit is configured to execute the instructions stored in the storage unit. The instructions comprise being configured to communicate with a first cell and a second cell; being configured a first SR period for a first SR transmission on the first cell and a second SR period for a second SR transmission on the second cell, wherein the second SR period is smaller than the first SR period; starting a SR prohibit timer according to the second SR period; receiving a radio resource control (RRC) message and releasing the second SR transmission in response to the RRC message; and keeping the SR prohibit timer running in response to the release of the second SR transmission.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 62/213,126 filed on Sep. 2, 2015, which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a device and a method used in a wireless communication system, and more particularly, to a device and a method of handling a scheduling request transmission. 
         [0004]    2. Description of the Prior Art 
         [0005]    A long-term evolution (LTE) system provides high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, a radio access network known as an evolved universal terrestrial radio access network (E-UTRAN) includes at least one evolved Node-B (eNB) for communicating with at least one user equipment (UE), and for communicating with a core network including a mobility management entity (MME), a serving gateway, etc., for Non-Access Stratum (NAS) control. 
         [0006]    A LTE-advanced (LTE-A) system is an evolution of the LTE system. The LTE-A system extends cell coverage of an eNB, increases peak data rate and throughput, and includes advanced techniques, such as carrier aggregation (CA), licensed-assisted access (LAA) using LTE, etc. 
         [0007]    According to the prior art, a UE can only transmit a scheduling request (SR) to a primary cell (PCell) of an eNB. Recently, it is proposed that the SR can also be transmitted to a secondary cell (SCell) of the eNB to improve flexibility of SR transmission. Accordingly, mechanisms such as control of a SR prohibit timer only designed for the PCell cannot be applied to the case of the SCell. The UE and/or the eNB cannot operate regularly, if the mechanisms are used for the SCell. 
         [0008]    Thus, how to handle the SR transmission is an important problem to be solved. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention therefore provides a communication device and method for handling a scheduling request transmission to solve the abovementioned problem. 
         [0010]    A communication device for handling scheduling request (SR) transmissions comprises a storage unit for storing instructions and a processing circuit coupled to the storage unit. The processing circuit is configured to execute the instructions stored in the storage unit. The instructions comprise being configured to communicate with a first cell and a second cell; being configured a first SR period for a first SR transmission on the first cell and a second SR period for a second SR transmission on the second cell, wherein the second SR period is smaller than the first SR period; starting a SR prohibit timer according to the second SR period; receiving a radio resource control (RRC) message and releasing the second SR transmission in response to the RRC message; and keeping the SR prohibit timer running in response to the release of the second SR transmission. 
         [0011]    A communication device for handling scheduling request (SR) transmissions comprises a storage unit for storing instructions and a processing circuit coupled to the storage unit. The processing circuit is configured to execute the instructions stored in the storage unit. The instructions comprise being configured to communicate with a first cell and a second cell; being configured a first SR period for a first SR transmission on the first cell and a second SR period for a second SR transmission on the second cell, wherein the second SR period is smaller than the first SR period; starting a SR prohibit timer according to the second SR period; receiving a radio resource control (RRC) message and releasing the second SR transmission in response to the RRC message; and stopping the SR prohibit timer or determining the SR prohibit timer as expired in response to the release of the second SR transmission. 
         [0012]    A communication device for handling scheduling request (SR) transmissions comprises a storage unit for storing instructions and a processing circuit coupled to the storage unit. The processing circuit is configured to execute the instructions stored in the storage unit. The instructions comprise being configured to communicate with a first cell and a second cell; being configured a first SR period for a first SR transmission on the first cell and a second SR period for a second SR transmission on the second cell, wherein the second SR period is smaller than the first SR period; starting a SR prohibit timer according to the second SR period; receiving a radio resource control (RRC) message and releasing the second SR transmission in response to the RRC message; and restarting the SR prohibit timer according to the first SR period in response to the release of the second SR transmission. 
         [0013]    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 
         [0014]      FIG. 1  is a schematic diagram of a wireless communication system according to an example of the present invention. 
           [0015]      FIG. 2  is a schematic diagram of a communication device according to an example of the present invention. 
           [0016]      FIG. 3  is a flowchart of a process according to an example of the present invention. 
           [0017]      FIG. 4  is a flowchart of a process according to an example of the present invention. 
           [0018]      FIG. 5  is a flowchart of a process according to an example of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]      FIG. 1  is a schematic diagram of a wireless communication system  10  according to an example of the present invention. The wireless communication system  10  is briefly composed of a network and a plurality of communication devices. The network and a communication device may communicate with each other via one or more carriers of licensed band(s) and/or unlicensed band(s). The network and the communication device may simultaneously communicate with each other via multiple cells (e.g., multiple carriers) including a primary cell (PCell) and one or more secondary cells (SCells). The abovementioned cells may be operated in the same or different frame structure types, or in the same or different duplexing modes, i.e. frequency-division duplexing (FDD) and time-division duplexing (TDD). For example, the PCell may be operated on a licensed carrier, while the SCell may be operated on an unlicensed carrier. 
         [0020]    In  FIG. 1 , the network and the communication devices are simply utilized for illustrating the structure of the wireless communication system  10 . Practically, the network may be an evolved universal terrestrial radio access network (E-UTRAN) including at least one evolved Node-B (eNB) and/or at least one relay in a long term evolution (LTE) system, a LTE-Advanced (LTE-A) system or an evolution of the LTE-A system. The network may be a fifth generation (5G) network including at least one 5G base station (BS) which employs orthogonal frequency-division multiplexing (OFDM) and/or non-OFDM, and transmission time interval (TTI) shorter than 1 ms (e.g. 100 or 200 microseconds) for communication with the communication devices. In general, a base station (BS) may also be used to refer any of the NB, the RNC, the eNB and the 5G BS. 
         [0021]    A communication device may be a user equipment (UE), a machine type communication (MTC) device, a mobile phone, a laptop, a tablet computer, an electronic book, a portable computer system, a vehicle, an aircraft. In addition, the network and the communication device can be seen as a transmitter or a receiver according to direction (i.e., transmission direction), e.g., for an uplink (UL), the communication device is the transmitter and the network is the receiver, and for a downlink (DL), the network is the transmitter and the communication device is the receiver. 
         [0022]      FIG. 2  is a schematic diagram of a communication device  20  according to an example of the present invention. The communication device  20  may be a communication device or the network shown in  FIG. 1 , but is not limited herein. The communication device  20  may include a processing circuit  200  such as a microprocessor or Application Specific Integrated Circuit (ASIC), a storage unit  210  and a communication interfacing unit  220 . The storage unit  210  may be any data storage device that may store a program code  214 , accessed and executed by the processing circuit  200 . Examples of the storage unit  210  include but are not limited to a subscriber identity module (SIM), read-only memory (ROM), flash memory, random-access memory (RAM), hard disk, optical data storage device, non-volatile storage unit, non-transitory computer-readable medium (e.g., tangible media), etc. The communication interfacing unit  220  is preferably a transceiver and is used to transmit and receive signals (e.g., data, messages and/or packets) according to processing results of the processing circuit  200 . 
         [0023]    In the following embodiments, a UE is used to represent a communication device in  FIG. 1 , to simplify the illustration of the embodiments. 
         [0024]      FIG. 3  is a flowchart of a process  30  according to an example of the present invention. The process  30  may be utilized in a UE, for handling scheduling request (SR) transmission(s). The process  30  may be compiled into the program code  214  and includes the following steps: 
         [0025]    Step  300 : Start. 
         [0026]    Step  302 : Be configured to communicate with a first cell and a second cell. 
         [0027]    Step  304 : Be configured a first SR period for a first SR transmission on the first cell and a second SR period for a second SR transmission on the second cell, wherein the second SR period is smaller than the first SR period. 
         [0028]    Step  306 : Start a SR prohibit timer according to the second SR period. 
         [0029]    Step  308 : Receive a radio resource control (RRC) message and release the second SR transmission in response to the RRC message. 
         [0030]    Step  310 : Keep the SR prohibit timer running in response to the release of the second SR transmission. 
         [0031]    Step  312 : End. 
         [0032]    According to the process  30 , the UE is configured by a BS to communicate with a first cell and a second cell (e.g., of the network in  FIG. 1 ). The second cell may be a SCell, but is not limited herein. Further, the UE is configured by the BS a first SR period for a first SR transmission on the first cell and a second SR period for a second SR transmission on the second cell, wherein the second SR period is smaller than the first SR period. The UE starts a SR prohibit timer according to the second SR period. That is, the UE determines to use the second SR period if the second SR period is shorter than the first SR period. Otherwise, the UE determines to use the first SR period. After a while or according to a certain condition, the UE receives a RRC message (e.g., RRCConnectionReconfiguration message), and releases the second SR transmission in response to the RRC message. In addition, the UE keeps the SR prohibit timer running in response to the release of the second SR transmission. That is, the UE keeps the SR prohibit timer running to avoid the UE from performing the second SR transmission (i.e., transmitting a SR on the first cell or the second cell), even if the second SR transmission is released. Thus, the second cell is not flushed by SR(s) transmitted by the UE, and loading (e.g., congestion) of the second cell is not deteriorated. 
         [0033]    Realization of the process  30  is not limited to the above description. The following examples may be applied to the process  30 . 
         [0034]    An example is illustrated as followed. A UE is connected to an eNB via a first cell (e.g., PCell) in a RRC connected mode. The eNB transmits to the UE an RRCConnectionReconfiguration message which configures the UE to communicate with a second cell (e.g., SCell) while communicating with the UE via the first cell. That is, the UE simultaneously communicates with the eNB via both the first and second cells. The UE is configured by the eNB to transmit a physical UL control channel (PUCCH) on the second cell. The UE receives from the eNB a first sr-ConfigIndex which configures a first SR period for a first SR transmission on the first cell and a second sr-ConfigIndex which configures a second SR period for a second SR transmission on the second cell. In one example, the first sr-ConfigIndex and the second sr-ConfigIndex are transmitted in a same RRCConnectionReconfiguration message, or are transmitted in different RRCConnectionReconfiguration messages. In another example, the first sr-ConfigIndex is transmitted in an RRCConnectionSetup message, and the second sr-ConfigIndex is transmitted in an RRCConnectionReconfiguration message. The UE determines the first SR period according to the first sr-ConfigIndex, and determines the second SR period according to the second sr-ConfigIndex. 
         [0035]    When the UE determines to transmit or transmits a SR on the first cell or the second cell and the first SR period is smaller than the second SR period, the UE starts a SR prohibit timer according to the first SR period and sr-ProhibitTimer. When the UE transmits a SR on the first cell or the second cell and the first SR period is larger than the second SR period, the UE starts a SR prohibit timer according to the second SR period and sr-ProhibitTimer. The eNB transmits to the UE an RRCConnectionReconfiguration message which explicitly or implicitly configures the UE to release the second SR transmission. In one example, the term “explicitly” means that the RRCConnectionReconfiguration message explicitly indicates release of a SR configuration for the second SR transmission. In one example, the term “implicitly” means that the RRCConnectionReconfiguration message indicates release of a PUCCH configuration of the second cell or release of the second cell (e.g., sCellToReleaseList) instead of indicating the release of the SR configuration. To keep prohibiting the SR transmissions on the first cell and the second cell, the UE keeps the SR prohibit timer running in response to the RRCConnectionReconfiguration message. When the eNB releases the SR configuration for the UE, the eNB may assign SR resources of the UE indicated in the SR configuration to another UE by transmitting another SR configuration to the another UE. If the eNB does not assign the SR resources to any UE, the eNB will not detect the SR on the SR resources on the second cell. The SR resources may include at least one of time resource(s) (e.g., subframe or period), frequency resource(s) and/or code resource(s) for transmitting a SR. 
         [0036]    In one example, the UE may perform the first SR transmission on the first cell, after the SR prohibit timer expires. The UE starts the SR prohibit timer according to the first SR period in response to the first SR transmission. That is, the UE starts the SR prohibit timer when transmitting a SR, and the UE transmits the SR when the SR prohibit timer expires. In one example, the RRC message may include a sCellToReleaseList for configuring the UE to release the second cell. In one example, the RRC message may include SchedulingRequestConfig for configuring the UE to release a SR configuration of the second cell. 
         [0037]      FIG. 4  is a flowchart of a process  40  according to an example of the present invention. The process  40  may be utilized in a UE, for handling SR transmission(s). The process  40  may be compiled into the program code  214  and includes the following steps: 
         [0038]    Step  400 : Start. 
         [0039]    Step  402 : Be configured to communicate with a first cell and a second cell. 
         [0040]    Step  404 : Be configured a first SR period for a first SR transmission on the first cell and a second SR period for a second SR transmission on the second cell, wherein the second SR period is smaller than the first SR period. 
         [0041]    Step  406 : Start a SR prohibit timer according to the second SR period. 
         [0042]    Step  408 : Receive a RRC message and release the second SR transmission in response to the RRC message. 
         [0043]    Step  410 : Stop the SR prohibit timer or determine the SR prohibit timer as expired in response to the release of the second SR transmission. 
         [0044]    Step  412 : End. 
         [0045]    According to the process  40 , the UE is configured by a BS to communicate with a first cell and a second cell (e.g., of the network in  FIG. 1 ). The second cell may be a SCell, but is not limited herein. Further, the UE is configured by the BS a first SR period for a first SR transmission on the first cell and a second SR period for a second SR transmission on the second cell, wherein the second SR period is smaller than the first SR period. The UE starts a SR prohibit timer according to the second SR period. After a while or according to a certain condition, the UE receives a RRC message (e.g., RRCConnectionReconfiguration message), and releases the second SR transmission in response to the RRC message. In addition, the UE stops the SR prohibit timer or determines the SR prohibit timer as expired in response to the release of the second SR transmission. That is, the UE stops the SR prohibit timer such that the UE is allowed to perform the first SR transmission (i.e., transmitting a SR). Thus, transmission of the SR is not delayed by the release of the second SR transmission, and throughput of the UE is improved. 
         [0046]    Realization of the process  40  is not limited to the above description. The following examples may be applied to the process  40 . 
         [0047]    In one example, the UE may perform the first SR transmission on the first cell, after the SR prohibit timer expires. The UE starts the SR prohibit timer according to the first SR period in response to the first SR transmission. That is, the UE starts the SR prohibit timer when transmitting a SR, and the UE transmits the SR when the SR prohibit timer expires. In one example, the RRC message may include a sCellToReleaseList for configuring the UE to release the second cell. In one example, the RRC message may include SchedulingRequestConfig for configuring the UE to release a SR configuration of the second cell. 
         [0048]      FIG. 5  is a flowchart of a process  50  according to an example of the present invention. The process  50  may be utilized in a UE, for handling SR transmission(s). The process  50  may be compiled into the program code  214  and includes the following steps: 
         [0049]    Step  500 : Start. 
         [0050]    Step  502 : Be configured to communicate with a first cell and a second cell. 
         [0051]    Step  504 : Be configured a first SR period for a first SR transmission on the first cell and a second SR period for a second SR transmission on the second cell, wherein the second SR period is smaller than the first SR period. 
         [0052]    Step  506 : Start a SR prohibit timer according to the second SR period. 
         [0053]    Step  508 : Receive a RRC message and release the second SR transmission in response to the RRC message. 
         [0054]    Step  510 : Restart the SR prohibit timer according to the first SR period in response to the release of the second SR transmission. 
         [0055]    Step  512 : End. 
         [0056]    According to the process  50 , the UE is configured by a BS to communicate with a first cell and a second cell (e.g., of the network in  FIG. 1 ). The second cell may be a SCell, but is not limited herein. Further, the UE is configured by the BS a first SR period for a first SR transmission on the first cell and a second SR period for a second SR transmission on the second cell, wherein the second SR period is smaller than the first SR period. The UE starts a SR prohibit timer according to the second SR period. After a while or according to a certain condition, the UE receives a RRC message (e.g., RRCConnectionReconfiguration message), and releases the second SR transmission in response to the RRC message. In addition, the UE restarts the SR prohibit timer according to the first SR period in response to the release of the second SR transmission. That is, the SR prohibit timer is restarted according to a longer period. Accordingly, the UE needs to wait for a longer time interval to perform the first SR transmission (i.e., transmitting a SR). Thus, the first cell is not flushed by SR(s) transmitted by the UE, and loading (e.g., congestion) of the first cell is not deteriorated. 
         [0057]    Realization of the process  50  is not limited to the above description. The following examples may be applied to the process  50 . 
         [0058]    In one example, the UE may perform the first SR transmission on the first cell, after the SR prohibit timer expires. The UE starts the SR prohibit timer according to the first SR period in response to the first SR transmission. That is, the UE starts the SR prohibit timer when transmitting a SR, and the UE transmits the SR when the SR prohibit timer expires. In one example, the RRC message may include a sCellToReleaseList for configuring the UE to release the second cell. In one example, the RRC message may include SchedulingRequestConfig for configuring the UE to release a SR configuration of the second cell. 
         [0059]    Those skilled in the art should readily make combinations, modifications and/or alterations on the abovementioned description and examples. The abovementioned description, steps and/or processes including suggested steps can be realized by means that could be hardware, software, firmware (known as a combination of a hardware device and computer instructions and data that reside as read-only software on the hardware device), an electronic system, or combination thereof. An example of the means may be the communication device  20 . Any of the processes above may be compiled into the program code  214 . 
         [0060]    To sum up, the present invention provides a communication device and method of handling SR transmission(s), and various requirements can be satisfied. According to an example for avoiding overloading of a cell, the cell is not flushed by SR(s) transmitted by the communication device. According to an example for improving throughput of the communication device, transmission of a SR is not delayed by release of a SR transmission. 
         [0061]    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.