Abstract:
A method for retransmitting reverse link data practiced by a media access control layer, the method comprising: buffering a plurality of data frames encapsulated in a first access probe in a memory; obtaining information regarding data frames encapsulated in the first access probe that are successfully decoded by a telecommunication network; selecting the buffered data frames that are required to be retransmitted, according to the obtained information; and passing down the selected data frames to a physical layer, to encapsulate the selected data frames into a second access probe and transmit the second access probe to the telecommunication network.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Applications No. 61/703,012 and No. 61/713,386, filed on Sep. 19, 2012 and Oct. 12, 2012, respectively, and the entirety of which is incorporated by reference herein. 
    
    
     BACKGROUND 
     Technical Field 
     The present invention relates to data retransmission, and in particular, relates to methods for retransmitting reverse link data and apparatuses using the same. 
     Description of the Related Art 
     At the level of interconnected network systems, protocol schemes have been developed to facilitate the exchange of data among multiple elements of the system. A protocol scheme specifies the manner of interpreting every data bit of a data packet exchanged across the networks. In order to simplify network design, several well-known techniques of layering the protocols have been developed. Protocol layering divides the network design into functional layers and then assigns separate protocols to perform each layer&#39;s task. 
     In a data retransmission mechanism, an upper layer is responsible for comprehending information of a SACK (Selective Acknowledgement) order, which indicates which frames have been successfully transmitted to the network, but the lower layer does not have the capability to comprehend the content of a SACK order. The lower layer cannot know which frames have been successfully transmitted to the network through received data after instructing RF (radio frequency) circuits to transmit data via a reverse link frame by frame. It may cause the lower layer to mistakenly instruct the RF hardware to retransmit the frames, which have been successfully transmitted, after receiving a data retransmission command from the upper layer, resulting in the unnecessary occupation of network bandwidth. 
     Methods for retransmitting reverse link data and apparatuses using the same are needed so as to have the lower layer instruct the RF circuits to retransmit frames that have not been successfully transmitted correctly. Therefore, the unnecessary occupation of network bandwidth may be avoided. 
     BRIEF SUMMARY 
     An embodiment of a method for retransmitting reverse link data practiced by a media access control layer, the method comprising: buffering a plurality of data frames encapsulated in a first access probe in a memory; obtaining information regarding data frames encapsulated in the first access probe that are successfully decoded by a telecommunication network; selecting the buffered data frames that are required to be retransmitted, according to the obtained information; and passing down the selected data frames to a physical layer, to encapsulate the selected data frames into a second access probe and transmit the second access probe to the telecommunication network. 
     An embodiment of an electronic device. The electronic device comprises a radio frequency processing module and a control module. The control module coupled to the radio frequency processing module. The control module configured to execute a method for retransmitting reverse link data practiced by a media access control layer, wherein the method comprises: buffering a plurality of data frames encapsulated in a first access probe in a memory, obtaining information regarding data frames encapsulated in the first access probe that are successfully decoded by a telecommunication network, selecting the buffered data frames that are required to be retransmitted, according to the obtained information, and passing down the selected data frames to a physical layer, to encapsulate the selected data frames into a second access probe and enable the PHY layer to drive the radio frequency processing module to transmit the third access probe to the telecommunication network. 
     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention can be fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  is a schematic diagram illustrating the architecture of an access network according to an embodiment of the invention; 
         FIG. 2  is a schematic diagram of a protocol stack according to an embodiment of the invention; 
         FIG. 3  is a flowchart illustrating a method for retransmitting reverse link data, which is practiced in the MAC layer, according to an embodiment of the invention; 
         FIG. 4  illustrates a message-exchange diagram in a situation where a SACK order has been received according to an embodiment of the invention; 
         FIG. 5  illustrates a message-exchange diagram in a situation where a SACK order has not been received according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
     The present invention will be described with respect to particular embodiments and with reference to certain drawings, but the invention is not limited thereto and is only limited by the claims. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
       FIG. 1  is a schematic diagram illustrating the architecture of an access network according to an embodiment of the invention. The access network contains at least a base station  110  and a subscriber device  120 . The subscriber device  120  may be a mobile phone, a tablet PC (personal computer), wireless telecommunication network card, or any electronic device having the capability of communicating with the base station  110 . Forward link RF (radio frequency) signals transmitted from the base station  110  are received by the antenna  121  and passed to the RF processing module  123 . The RF processing module  123  down-converts the signals to baseband and digitizes the baseband signals. The digital signal processing unit  125  processes the digitized baseband signals in accordance with a protocol. The protocol may be a CDMA (code division multiple access)-based or a LTE (Long Term Evolution)-based protocol, or others. The signal processing performed by the digital signal processing unit  125  includes demodulation with the forward link spreading code and channel code, as well as the Viterbi decoding and block de-interleaving, the use of which is well known in the art. This processing is performed on a frame-by-frame basis. The resulting frames of digital data from the digital signal processing unit  125  are passed to the control unit  127 . The control unit  127  receives the frames of digital data and determines if the digital data is a signaling message or user data based on header information contained in each frame. The control unit  127  may further configure the digital signal processing unit  125  for the reception of forward link data and the transmission of reverse link data by providing the necessary spreading and channel codes, as well as the generation of outgoing signaling messages that are transmitted to the base station  110 . The reverse link data are forwarded along with the outgoing signaling messages to the digital signal processing unit  125  which Viterbi encodes, block interleaves, modulates and spreads the data. 
     The digital signal processing unit  125  may include a DSP (digital signal processor) controlled by software instructions stored in the memory  120 . The control unit  127  may include a microprocessor, when loading and executing software instructions stored in the memory  129 , performing methods for retransmitting reverse link data. The digital signal processing unit  125  and/or the control unit  127  may be considered as a control module  130 , which drives the RF processing module  123  to receive forward link RF signals from the base station  110  and transmit reverse link RF signals to the base station  110 . 
       FIG. 2  is a schematic diagram of a protocol stack according to an embodiment of the invention. The control module  130  may implement the protocol stack  200  to incorporate with the PHY (physical) layer  210 , the MAC (media access control) layer  220 , the LAC (link access control) layer  230  and the layer three  240 . The protocol stack  200  may be practiced in software instructions, which can be loaded and executed by the digital signal processing unit  125  or/and the control unit  127  of the control module  130  to realize methods for retransmitting reverse link data in accordance with an embodiment of the invention. 
       FIG. 3  is a flowchart illustrating a method for retransmitting reverse link data, which is practiced in the MAC layer  220 , according to an embodiment of the invention. The control module  130  performs the method for retransmitting reverse link data as follows when loading and executing the software instructions of the MAC layer  220 . The MAC layer  220  receives an instructive message for transmitting reverse link data from the LAC layer  230 , wherein the instructive message comprises all the data frames of a very first enhanced access probe (step S 312 ), and detects that a currently selected access mode is the basic mode and has elapsed for a random delay which means the accessing procedure is begin (step S 314 ). Information regarding the selected access mode may be achieved by inspecting register settings, or variable values stored in the memory  129 . In alternative embodiments, the LAC layer  230  may encapsulate the information regarding the selected access mode into the instructive message for subsequent judging by the MAC layer  220 . 
     After the random delay, it is determined whether the SACK (Selective Acknowledgement) is used (step S 320 ). If not, the PHY layer  210  is directed to transmit the designated data following the specification, which is well known by those skilled in the art (step S 322 ). In step S 320 , the MAC layer  220  may determine whether the SACK is used by inspecting a register setting, or a particular value stored in the memory  129 . In alternative embodiments, the LAC layer  230  may encapsulate information regarding whether the SACK is used into the instructive message for subsequent judging by the MAC layer  220 . Whether to make use of the SACK is decided by a telecommunication network, and is broadcast through a PCH (paging channel), which can be got by the subscriber device  120 . Information carried in the PCH regarding whether the SACK is used can be comprehended by the layer three  240 . In step S 322 , the MAC layer  220  may use the conventional ACK (acknowledgement) procedure to direct the PHY layer  210  to transmit the designated data, and the ACK procedure is specified in the 3GPP2 (3 rd  Generation Partnership Project 2) CS0003-e published in June 2010. 
     After determining that the SACK is used, the “Yes” path of step S 320 , the MAC layer  220  determines whether it is a first EAP (enhanced access probe) in an access attempt (step S 330 ). In step S 330 , the MAC layer  220  may inspect the serial number “seqno” of the instructive message received from the LAC layer  230  to achieve the determination, where “0” indicates it is a first EAP in the access attempt, and a value other than “0” indicates it is a retransmitted EAP of the access attempt. If it is a first EAP, the “Yes” path of step S 330 , data frames of the instructive message including all data frames in the very first access probe are passed down to the PHY layer  210 , where the total number of the data frames may be N (step S 332 ), and the data frames of the instructive message are buffered in the memory  129 , which means all data frames in the very first access probe are buffered (step S 334 ). The PHY layer  210  drives the requisite hardware, e.g. the RF processing module  123 , to transmit an EAP carrying the data frames via the R-EACH (Reverse-enhanced Access Channel) to the telecommunication network through the base station  110  after receiving the data frames. The memory  129  may be a RAM (Random Access Memory) and allocate a buffer region to store the data frames. 
     After it is determined that the SACK is not used, the “No” path of step S 320 , it is determined whether a SACK order has been received (step S 340 ). The SACK order is generated by the telecommunication network, which contains information indicating which data frames were successfully decoded, where the data frames were transmitted by one or more EAPs. The layer three  240  is capable of comprehending the SACK order and may notify the MAC layer  220  of whether a SACK order has been received by setting one or more registers (not shown) or storing relevant information in the memory  129 . In alternative embodiments, the LAC layer  230  may encapsulate information whether a SACK order has been received, which is notified by the layer three  240 , into the instructive message for subsequent judging by the MAC layer  220 . 
     After it is determined that a SACK order has been received, the “Yes” path of step S 340 , the buffered data frame(s) that are required to be retransmitted are selected and passed down to the PHY layer  210  (step S 342 ), and information regarding which data frame(s) have been retransmitted is stored in the memory  129  (step S 344 ). The PHY layer  210  drives requisite hardware, e.g. the RF processing module  123  to transmit an EAP carrying the data frame(s) that are required to be retransmitted, by using the R-EACH to the telecommunication network through the base station  110  after receiving the data frames. Additionally, it should be appreciated that the layer three  240  may set one or more registers (not shown) or store relevant information in the memory  129  to notify the MAC layer  220  of which data frames have been successfully decoded after comprehending a SACK order. In alternative embodiments, the LAC layer  230  encapsulates information regarding which data frame(s) have been successfully decoded by the telecommunication network, which is notified by the layer three  240 , into the instructive message for subsequent judging by the MAC layer  220 . In step S 342 , the MAC layer  220  may store a vector of a bit mask in the memory  129  to indicate which buffered data frame(s) have been successfully decoded by the telecommunications network. For example, a bit n in the vector equaled to “1” indicates that the n-th data frame has been successfully decoded while a bit m in the vector equaled to “0” indicates that the m-th data frame has not been successfully decoded. An exemplary vector “101001” indicates the buffered 0-, 2- and 5-th data frames have been successfully decoded by the telecommunication network. In alternative embodiments of step S 342 , the MAC layer  220  may further remove the data frame(s) that have been successfully decoded by the telecommunication network from the memory  129 , and rearrange the remaining data frames in an order that is in compliance with the retransmission. 
     In order to illustrate steps S 342  and S 344  precisely,  FIG. 4  illustrates a message-exchange diagram in a situation where a SACK order has been received according to an embodiment of the invention. Suppose that t 1  is a moment of performing the method as shown in  FIG. 3 . Before t 1 , the subscriber device  120  has encapsulated six data frames  412   a  to  412   f  into an EAP  410 , transmitted the EAP  410  to the base station  110 , and received a SACK order  420 , which contains information regarding the 0-, 2- and 5-th data frames having been successfully decoded by the telecommunication network. It is to be understood that, when the EAP  410  was transmitted, the MAC layer  220  buffered the six data frames  412   a  to  412   f , reference can be made to description of steps S 332  and S 334 . At t 1 , the MAC layer  220  passes down the buffered data frames  412   b ,  412   d  and  412   e , which are required to be retransmitted, to the PHY layer  210  (step S 342 ), thereby enabling the PHY layer  210  to drive the requisite hardware, e.g. the RF processing module  123 , to transmit the EAP  430  carrying the data frames  412   b ,  412   d  and  412   e  via the R-EACH to the telecommunication network through the base station  110 . Additionally, the MAC layer  220  may further store information about the data frames  412   b ,  412   d  and  412   e  having been retransmitted in the memory  129 , reference can be made to description of step S 344 . 
     After it is determined that a SACK order has not been received , the “No” path of step S 340 , all of the buffered data frames including all the data frames in the very first access probe are passed down to the PHY layer  210  (step S 346 ). The PHY layer  210  drives the requisite hardware, e.g. the RF processing module  123  to transmit an EAP carrying the retransmitted data frames via the R-EACH to the telecommunication network through the base station  110  after receiving the data frames. In order to illustrate step S 346  precisely,  FIG. 5  illustrates a message-exchange diagram in a situation where a SACK order has not been received according to an embodiment of the invention. Suppose that t 2  is a moment of performing the method as shown in  FIG. 3 . Before t 2 , the subscriber device  120  has encapsulated six data frames  512   a  to  512   f  into an EAP  510  and transmitted the EAP  510  to the base station  110 , but has not received any SACK order. At t 2 , the MAC layer  220  passes down all the buffered data frames  512   a  to  512   f  to the PHY layer  210  (step S 346 ), thereby enabling the PHY layer  210  to drive the requisite hardware, e.g. the RF processing module  123  to transmit the EAP  520  carrying the data frames  512   a  to  512   f  via the R-EACH to the telecommunication network through the base station  110 . 
     Although the embodiment has been described by having specific elements in  FIG. 1 , it is noted that additional elements may be included to achieve better performance without departing from the spirit of the invention. While the process flows described in  FIG. 3  includes a number of operations that appear to occur in a specific order, it should be apparent that these processes can include more or fewer operations, which can be executed serially or in parallel ,e.g., using parallel processors or a multi-threading environment. 
     While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.