Abstract:
In data communication systems, data packet processing for transmission and reception may go through different stages such as segmentation or packing of the data packets on the transmission side and duplicate detection, reordering, and reassembly on the reception side. For reliable data transmission between peer entities, acknowledgement based retransmission protocol known as Automatic Repeat Request may be used where each retransmission can further segment previously transmitted data packets. This type of data processing may lead to high memory requirements and high processing requirements. A method and apparatus are disclosed that maintain additional information about the data packets which enables virtual segmentation and packing on the transmitter side and on the receiver side, virtual duplicate detection, reordering and reassembly. Performing the segmentation, packing, duplicate detection, reordering and reassembly operations in virtual manner reduce the memory and processing requirements and this may lead to reduced power consumption and improved user experience.

Description:
BACKGROUND 
     In data communication systems, data packet processing for transmission and reception may go through different stages such as segmentation, concatenation or packing of the data packets on the transmission side and duplicate detection, reordering, and reassembly on the reception side. Also in some data communication systems, for reliable data transmission between the peers, an acknowledgement (positive or negative) based retransmission protocol known as Automatic Repeat Request (ARQ) may be used where each retransmission can further segment the previously transmitted data packets. This type of data processing may lead to high memory requirements and high processing requirements. 
     The services and features of data communication systems may be implemented in distinct layers. The data packets given by an application or upper layer of any protocol may be referred as Service Data Unit (SDU) and the data unit provided to the lower layer may be referred to as Protocol Data Unit (PDU) as shown in  FIG. 1 . On the transmission side a protocol entity works on the SDU as the input and performs data packet processing. On the receiving side, a protocol entity works on a PDU as the input and performs data packet processing. The data packet processing on the transmission side may add headers or footers or both to an SDU. The data packet processing on the reception side may remove headers or footers or both from the PDU and provide an SDU to an application or upper layer. 
     When a PDU transmitted by a transmit entity is correctly received by a receiving entity, it may send a positive acknowledgement (ACK) to the transmitting entity. When a PDU transmitted by a transmit entity is not correctly received by a receiving entity, it may send a negative acknowledgement (NACK) to the transmitting entity. As a response to the NACK, the transmitting entity may retransmit a PDU. The retransmitted PDU may have to be resegmented depending on the available transmission resources. 
     There are many different scenarios in which an SDU may be processed by a protocol entity to generate PDUs using segmentation and packing. An SDU may be divided into two or more parts for transmission and each part is referred herein as an SDU segment. Examples of the data packet processing scenarios on transmission side are illustrated in  FIG. 2 , Examples of the processing scenarios illustrated in  FIG. 2  include transmission of an SDU in a PDU without segmentation or packing, segmentation of an SDU and transmission in two different PDUs, and two different SDUs or SDU segments packed and transmitted in a single PDU. In general, an SDU may be segmented in two or more PDUs and two or more SDU or SDU segments may be packed in a single PDU. In some cases, due to errors in transmission or reception, a PDU may need to be retransmitted. When a PDU is retransmitted, in order to match the available transmission resource size, it may have to be segmented into smaller size called retransmission PDU segments (PDUS). Alternatively, if the available transmission resources are larger than the size of the original PDU, two or more PDUs or PDU segments that need to be retransmitted may be packed into a single PDU. The single packed PDU used for retransmission may still be referred to as retransmission PDU segments. The PDU retransmission examples are illustrated in  FIG. 2  by the PDU m+3  which may be retransmitted as PDU segments PDUS x  and PDUS x+1 . The PDU m+4  and a segment of PDU m+5  may be retransmitted as a PDU segment PDUS x+2 . The remaining segment of PDU m+5  may be retransmitted as a PDU segment PDUS X+3 . 
     Similarly, examples of the packet data processing scenarios on the reception side are illustrated  FIG. 3 . Examples of the processing scenarios illustrated in  FIG. 3  include reception of an SDU in a PDU without unpacking or reassembly, reassembly of an SDU from reception of two different PDUs, unpacking of two different SDUs or SDU segments from a single PDU and reassembling an SDU from two different PDUs, and reassembling a retransmitted PDU from multiple PDU segments. In general, an SDU may be reassembled from two or more PDUs and two or more SDU or SDU segments may be unpacked from a single PDU. The PDU retransmission examples at the receiver are illustrated in  FIG. 3  by reception of a retransmitted PDU m+3  by packing the PDU segments PDUS x  and PDUS x+1 . The PDU m+4  and a segment of PDU m+5  are received by retransmitted PDU segment PDUS m+2 . The remaining segment of PDU m+5  is received as retransmitted PDU segment PDUS m+3 . 
     As discussed above, when a transmitting entity retransmits a PDU that was previously transmitted, it may lead to segmentation of a single PDU or packing of multiple PDUs. 
     A method and apparatus are disclosed in application “METHOD AND APPARATUS FOR DATA PACKET PROCESSING”, filed Jan. 11, 2016, U.S. application Ser. No. 14/992,229, incorporated by reference herein, that maintain additional information about the data packets which enable virtual segmentation and packing on the transmitter side and similarly, on the receiver side, virtual duplicate detection, reordering and reassembly. Performing the segmentation, packing, duplicate detection, reordering and reassembly operations in virtual manner reduce the memory and processing requirements and this may lead to reduced power consumption and improved user experience. 
     SUMMARY 
     A method and apparatus are disclosed that enable data processing during retransmission without actually segmenting, resegmenting or packing. The disclosed method maintains the information about the data packets which are to be retransmitted and enables virtual segmentation, packing, re-segmenting on the transmitter side. 
     In accordance with an aspect of the present invention, a method for processing a data packet for transmission in a wireless communication system may include: (A) controlling, by a processing device, when a data packet as a new Service Data Unit (SDU) is determined to be received from a first layer of a protocol used in the wireless communication system, creating, for a given new SDU, a new entry in an SDU Information Queue (SIQ) indicating: a Start Address set to a system memory address of the given new SDU, a Total Size set to a size of the given new SDU, a Remaining Length set to the size of the given new SDU, a Previous Pointer set to (i) an index of a previously received SDU in the SIQ, when the SIQ includes an entry for the previously received SDU, and (ii) null, when the given new SDU is a first received SDU, and a Next Pointer set to a next free element in the SIQ configured to store information of a next received SDU; (B) controlling, by the processing device, when a transmission resource is determined to be allocated and a retransmission PDU is determined not to be pending in a PDU Retransmission Information Queue (PRIQ), (a) preparing a data packet as a Protocol Data Unit (PDU) at a second layer of the protocol for transmission, in which the second layer is at a lower level in the protocol than the first layer, (b) updating a PDU Information Queue (PIQ) by setting: a PDU Sequence Number of the PDU to a next sequence number in a predetermined range of sequence numbers, a Total Size to an entire size of the PDU, a Total Number of SDU Segments packed to a total number of whole SDUs or SDU segments to be packed in the PDU, and a Pointer to a SDU Segment Information Queue (SSIQ) to an index of the SSIQ to be updated with information about the whole SDUs or SDU segments packed into the PDU; (c) setting the index of the SSIQ to be updated to an index in the SIQ of a SDU or a segment of an SDU packed in the PDU, (d) when a whole SDU or a first segment of a SDU is packed in the PDU, setting a SDU Segment Address Offset to the Start Address, (e) when a whole SDU or the first segment of a SDU is not packed in the PDU, setting the SDU Segment Address Offset to a sum of the Start Address and the Total Size less the Remaining Length, and (f) setting: a SDU Segment Length to a size of the SDU or the SDU segment packed in the PDU, a SDU Segment Offset to a memory address of the PDU in which the SDU or the SDU segment is packed, the Previous Pointer to an index of a most recently formed entry in the SSIQ, the Next Pointer to an index of a next free entry in the SSIQ, and the Remaining Length to (i) zero, when a whole SDU is packed in the PDU, and (ii) the Remaining length minus the SDU segment length, when at least one SDU segment remains and is not to be packed in the PDU; and (C) controlling, by the processing device, when a transmission resource is determined to be allocated and a retransmission PDU is determined to be pending in the PRIQ, updating the PRIQ by: setting a Retransmitted PDU Size equal to an allocated transmission resource size, and preparing a PDU segment as the retransmission PDU according to the allocated transmission resource size using a PDU Segment Offset and a SDU Segment Offset of the PRIQ. 
     In one alternative, the method may include controlling, by the processing device, repeatedly performing (A) (B) and (C), until a result of a determination after (B) or (C) is performed is all new received SDUs in the SIQ have been transmitted as a given PDU and the PRIQ does not indicate any retransmission PDU is pending. 
     In one alternative, the PDU may include one or more SDUs or SDU Segments. 
     In one alternative, the retransmission of a given PDU may be prioritized over transmission of a new PDU, information for only one PDU Segment may be stored in the PRIQ at a time, and information for the PDU or PDU segment current being retransmitted may be stored in the PRIQ. 
     In one alternative, a first PDU to be retransmitted from at least one PDU to be retransmitted may be formed as the retransmission PDU. 
     In one alternative, the retransmission PDU may be one of (i) a same size as the first PDU when transmitted a first time, (ii) a segment of a previously transmitted PDU, and (iii) a segment of two previously transmitted PDUs. 
     In one alternative, a Number of Retransmissions for the PDU indicated in the PRIQ may be set to a value of one greater than a current value of the Number of Retransmissions when the PDU is transmitted, and the value of the Number of Retransmission may be initialized to zero. 
     In one alternative, the method may further comprise: (D) controlling, by the processing device, when a positive Transmission Completion Status (ACK) is received for a given PDU having a given Sequence Number, searching the PIQ for an information element corresponding to the given Sequence Number, based on a Pointer to the SSIQ of the information element determined from the searching the PIQ, identifying an associated information element in the SSIQ, from an SIQ Index of the associated information element in the SSIQ, identifying an information element in the SIQ to which the Transmission Completion Status corresponds; (E) controlling, by the processing device, performing (D) until a positive ACK Status for all SDU segments of a given SDU is received, and when a positive ACK status for all SDU segments of the given SDU is determined to be received, releasing the information element in the SIQ corresponding to the given SDU and the information element in the SSQI corresponding to each SDU segment of the given SDU, updating the Next Pointer and the Previous Pointer with regard to each remaining element in the SIQ and the SSIQ, and releasing the information element in the PIQ corresponding to the Sequence Number of the PDU for which the Transmission Complete Status is received; and (F) controlling, by the processing device, when a negative Transmission Completion (NACK) status is received for a given unsuccessfully transmitted PDU, searching the PIQ for a second information element corresponding to a Sequence Number of the given unsuccessfully transmitted PDU, based on a Pointer to the SSIQ in the PDU determined from the second information element, identifying an associated information element in the SSQI, setting: the PDU Segment Offset to zero, the SDU Segment Offset by indexing into the associated information element of the SSQI identified based on the Pointer to the SSIQ of the second information element determined from the searching the PIQ, and the Remaining Length to Total Size from the PIQ. 
     In one alternative, the method may further comprise: (G) controlling, by the processing device, when the positive Transmission Completion (ACK) status is received for a given retransmitted PDU, (a) searching the PRIQ for a third information element corresponding to the Sequence Number of the PDU for which a NACK status was received, (b) when the Sequence Number of the PDU corresponding to the positive ACK status received is determined not to match a Sequence Number for the third information element in the PRIQ, performing (D), (E) and (F), and (c) when the Sequence Number of the PDU corresponding to the positive ACK status received is determined to match the Sequence Number for the third information element in the PRIQ, incrementing the PDU Segment Offset and the SDU Segment Offset by the Retransmitted PDU Size, decrementing the Remaining Length by subtracting the Retransmitted PDU size therefrom, when the Remaining Length in the PRIQ is zero, performing (D), (E) and (F), and when the Remaining Length is not equal to zero, performing (G)(a), G(b) and (G)(c) when a determination is a next positive Transmission Completion (ACK) status is received. 
     In one alternative, the method may further comprise: (H) controlling, by the processing device, repeatedly performing (D), (E), (F) and (G), until a result of a determination after (G) is performed is all SDUs received are transmitted successfully. 
     In accordance with an aspect of the present invention, an apparatus for processing a data packet for transmission in a wireless communication system may include: circuitry configured to control operations of: (A) when a data packet as a new Service Data Unit (SDU) is determined to be received from a first layer of a protocol used in the wireless communication system, creating, for a given new SDU, a new entry in an SDU Information Queue (SIQ) indicating: a Start Address set to a system memory address of the given new SDU, a Total Size set to a size of the given new SDU, a Remaining Length set to the size of the given new SDU, a Previous Pointer set to (i) an index of a previously received SDU in the SIQ, when the SIQ includes an entry for the previously received SDU, and (ii) null, when the given new SDU is a first received SDU, and a Next Pointer set to a next free element in the SIQ configured to store information of a next received SDU; (B) when a transmission resource is determined to be allocated and a retransmission. PDU is determined not to be pending in a PDU Retransmission Information Queue (PRIQ), (a) preparing a data packet as a Protocol Data Unit (PDU) at a second layer of the protocol for transmission, in which the second layer is at a lower level in the protocol than the first layer, (b) updating a PDU Information Queue (PIQ) by setting: a PDU Sequence Number of the PDU to a next sequence number in a predetermined range of sequence numbers, a Total Size to an entire size of the PDU, a Total Number of SDU. Segments packed to a total number of whole SDUs or SDU segments to be packed in the PDU, and a Pointer to a SDU Segment Information Queue (SSIQ) to an index of the SSIQ to be updated with information about the whole SDUs or SDU segments packed into the PDU; (c) setting the index of the SSIQ to be updated to an index in the SIQ of a SDU or a segment of an SDU packed in the PDU, (d) when a whole SDU or a first segment of a SDU is packed in the PDU, setting a SDU Segment Address Offset to the Start Address, (e) when a whole SDU or the first segment of a SDU is not packed in the PDU, setting the SDU Segment Address Offset to a sum of the Start Address and the Total Size less the Remaining Length, and (f) setting: a SDU Segment Length to a size of the SDU or the SDU segment packed in the PDU, a SDU Segment Offset to a memory address of the PDU in which the SDU or the SDU segment is packed, the Previous Pointer to an index of a most recently formed entry in the SSIQ, the Next Pointer to an index of a next free entry in the SSIQ, and the Remaining Length to (i) zero, when a whole SDU is packed in the PDU, and (ii) the Remaining length minus the SDU segment length, when at least one SDU segment remains and is not to be packed in the PDU; and (C) when a transmission resource is determined to be allocated and a retransmission PDU is determined to be pending in the PRIQ, updating the PRIQ by: setting a Retransmitted PDU Size equal to an allocated transmission resource size, and preparing a PDU segment as the retransmission PDU according to the allocated transmission resource size using a PDU Segment Offset and a SDU Segment Offset of the PRIQ. 
     In one alternative of the apparatus, the circuitry may be configured to control repeatedly performing (A), (B) and (C), until a result of a determination after (B) or (C) is performed is all new received SDUs in the SIQ have been transmitted as a given PDU and the PRIQ does not indicate any retransmission PDU is pending. 
     In one alternative of the apparatus, the PDU may include one or more SDUs or SDU Segments. In one alternative of the apparatus, retransmission of a given PDU may be prioritized over transmission of a new PDU, information for only one PDU Segment may be stored in the PRIQ at a time, and information for the PDU or PDU segment current being retransmitted may be stored in the PRIQ. 
     In one alternative of the apparatus, a first PDU to be retransmitted from at least one PDU to be retransmitted may be formed as the retransmission PDU. 
     In one alternative of the apparatus, the retransmission PDU may be one of (i) a same size as the first PDU when transmitted a first time, (ii) a segment of a previously transmitted PDU, and (iii) a segment of two previously transmitted PDUs. 
     In one alternative of the apparatus, a Number of Retransmissions for the PDU indicated in the PRIQ may be set to a value of one greater than a current value of the Number of Retransmissions when the PDU is transmitted, and the value of the Number of Retransmission may be initialized to zero. 
     In one alternative of the apparatus, the circuitry may be configured to control operations of: (D) when a positive Transmission Completion Status (ACK) is received for a given PDU having a given Sequence Number, searching the PIQ for an information element corresponding to the given Sequence Number, based on a Pointer to the SSIQ of the information element determined from the searching the PIQ, identifying an associated information element in the SSIQ, from an SIQ Index of the associated information element in the SSIQ, identifying an information element in the SIQ to which the Transmission Completion Status corresponds; (E) performing (D) until a positive ACK Status for all SDU segments of a given SDU is received, and when a positive ACK status for all SDU segments of the given SDU is determined to be received, releasing the information element in the SIQ corresponding to the given SDU and the information element in the SSQI corresponding to each SDU segment of the given SDU, updating the Next Pointer and the Previous Pointer with regard to each remaining element in the SIQ and the SSIQ, and releasing the information element in the PIQ corresponding to the Sequence Number of the PDU for which the Transmission Complete Status is received; and (F) when a negative Transmission Completion (NACK) status is received for a given unsuccessfully transmitted PDU, searching the PIQ for a second information element corresponding to a Sequence Number of the given unsuccessfully transmitted PDU, based on a Pointer to the SSIQ in the PDU determined from the second information element, identifying an associated information element in the SSQI, and setting: the PDU Segment Offset to zero, the SDU Segment Offset by indexing into the associated information element of the SSQI identified based on the Pointer to the SSIQ of the second information element determined from the searching the PIQ, and the Remaining Length to Total Size from the PIQ. 
     In one alternative of the apparatus, the circuitry may be configured to control operations of: (G) when the positive Transmission Completion (ACK) status is received for a given retransmitted PDU, (al) searching the PRIQ for a third information element corresponding to the Sequence Number of the PDU for which a NACK status was received, (b) when the Sequence Number of the PDU corresponding to the positive ACK status received is determined not to match a Sequence Number for the third information element in the PRIQ, performing (D), (E) and (F), and (c) when the Sequence Number of the PDU corresponding to the positive ACK status received is determined to match the Sequence Number for the third information element in the PRIQ, incrementing the PDU Segment Offset and the SDU Segment Offset by the Retransmitted PDU Size, decrementing the Remaining Length by subtracting the Retransmitted PDU size therefrom, when the Remaining Length in the PRIQ is zero, performing (D), (E) and (F), and when the Remaining Length is not equal to zero, performing (G)(a), G(b) and G(c) when a determination is a next positive Transmission Completion (ACK) status is received. 
     In one alternative of the apparatus, the circuitry may be configured to control operations of: (H) controlling, by the processing device, repeatedly performing (D), (E), (F) and (G), until a result of a determination after (G) is performed is all. SDUs received are transmitted successfully. 
     A wireless communication device comprising: a receiver to receive a data packet in a wireless communication system; and a processing device to control operations of: (A) when a data packet as a new Service Data Unit (SDU) is determined to be received from a first layer of a protocol used in the wireless communication system, creating, for a given new SDU, a new entry in an SDU Information Queue (SIQ) indicating: a Start Address set to a system memory address of the given new SDU, a Total Size set to a size of the given new SDU, a Remaining Length set to the size of the given new SDU, a Previous Pointer set to (i) an index of a previously received SDU in the SIQ, when the SIQ includes an entry for the previously received SDU, and (ii) null, when the given new SDU is a first received SDU, and a Next Pointer set to a next free element in the SIQ configured to store information of a next received SDU; (B) when a transmission resource is determined to be allocated and a retransmission PDU is determined not to be pending in a PDU Retransmission. Information Queue (PRIQ), (a) preparing a data packet as a Protocol Data Unit (PDU) at a second layer of the protocol for transmission, in which the second layer is at a lower level in the protocol than the first layer, (b) updating a PDU Information Queue (PIQ) by setting: a PDU Sequence Number of the PDU to a next sequence number in a predetermined range of sequence numbers, a Total Size to an entire size of the PDU, a Total Number of SDU Segments packed to a total number of whole SDUs or SDU segments to be packed in the PDU, and a Pointer to a SDU Segment. Information Queue (SSIQ) to an index of the SSIQ to be updated with information about the whole SDUs or SDU segments packed into the PDU; (c) setting the index of the SSIQ to be updated to an index in the SIQ of a SDU or a segment of an SDU packed in the PDU, (d) when a whole SDU or a first segment of a SDU is packed in the PDU, setting a SDU Segment Address Offset to the Start Address, (e) when a whole SDU or the first segment of a SDU is not packed in the PDU, setting the SDU Segment Address Offset to a sum of the Start Address and the Total Size less the Remaining Length, and (f) setting: a SDU Segment Length to a size of the SDU or the SDU segment packed in the PDU, a SDU Segment Offset to a memory address of the PDU in which the SDU or the SDU segment is packed, the Previous Pointer to an index of a most recently formed entry in the SSIQ, the Next Pointer to an index of a next free entry in the SSIQ, and the Remaining Length to (i) zero, when a whole SDU is packed in the PDU, and (ii) the Remaining length minus the SDU segment length, when at least one SDU segment remains and is not to be packed in the PDU; and (C) when a transmission resource is determined to be allocated and a retransmission PDU is determined to be pending in the PRIQ, updating the PRIQ by: setting a Retransmitted PDU Size equal to an allocated transmission resource size, and preparing a PDU segment as the retransmission PDU according to the allocated transmission resource size using a PDU Segment Offset and a SDU Segment Offset of the PRIQ. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a layered architecture of a data communication system. 
         FIG. 2  illustrates example segmentation and packing scenarios in a protocol entity at the transmitter side. 
         FIG. 3  illustrates an example reassembly and unpacking scenarios in a protocol entity at the receiver side. 
         FIG. 4  illustrates details of the different information queues maintained by a transmitter protocol entity according to the aspects of the present invention. 
         FIG. 5  illustrates example interactions amongst different queues by a transmitter protocol entity according to the aspects of the present invention. 
         FIG. 6A  illustrates an example flow diagram for processing steps when a new SDU is received at a transmitter protocol entity according to aspects of the present invention. 
         FIG. 6B  illustrates an example flow diagram for processing steps when a retransmission PDU is pending in PRIQ and new transmission resources are allocated according to aspects of the present invention. 
         FIG. 7A  illustrates an example flow diagram for processing steps when a positive Transmission Completion status (ACK) is received for a PDU by a transmitter protocol entity according to aspects of the present invention. 
         FIGS. 7B and 7D  illustrate an example flow diagram for processing steps when a negative. Transmission Completion status (NACK) is received for a PDU by a transmitter protocol entity according to aspects of the present invention. 
         FIG. 7C  illustrates an example flow diagram for processing steps when a positive Transmission Completion status (ACK) is received for a retransmitted PDU by a transmitter protocol entity according to aspects of the present invention. 
         FIG. 8  illustrates details of the different information queues maintained by a receiver protocol entity according to the aspects of the present invention. 
         FIG. 9  illustrates example interactions amongst different queues by a receiver protocol entity according to the aspects of the present invention. 
         FIG. 10  illustrates an example flow diagram for processing steps when a new PDU is received at a receiver protocol entity according to aspects of the present invention. 
         FIG. 11  illustrates a conventional mobile wireless communication system. 
         FIG. 12  illustrates a wireless mobile station diagram, which may be employed with aspects of the invention described herein. 
         FIG. 13  illustrates an application processor subsystem for a wireless mobile station, which may be employed with aspects of the invention described herein. 
         FIG. 14  illustrates a baseband subsystem for a wireless mobile station, which may be employed with aspects of the invention described herein. 
         FIG. 15  illustrates a Radio Frequency (RF) subsystem for a wireless mobile station, which may be employed with aspects of the invention described herein. 
     
    
    
     DETAILED DESCRIPTION 
     The foregoing aspects, features and advantages of the present invention will be further appreciated when considered with reference to the following description of exemplary embodiments and accompanying drawings, wherein like reference numerals represent like elements. In describing the exemplary embodiments of the invention illustrated in the appended drawings, specific terminology will be used for the sake of clarity. However, the aspects of the invention are not intended to be limited to the specific terms used. 
     The data packet processing is performed by maintaining the required information for the SDUs, PDUs and SDU segments in their respective information queues. According to an aspect of the present invention, in case where the PDU processing requires retransmission, an additional information queue namely “PDU Retransmission Information Queue” (PRIQ) may be created and maintained to enable virtual data packet processing as shown in  FIG. 4 . Next, each of the information queues is described in detail. 
     The SDU Information Queue (SIQ) maintains the following information:
         Start Address of an SDU   Total Size of an SDU   Remaining Length after an SDU has been segmented   Previous Pointer and Next Pointer to form bidirectional link between each element in the SIQ for fast traversal through the elements in the queue.       

     The PDU Information Queue (PIQ) maintains the following information:
         PDU Sequence Number   Total Size of a PDU   Total number of SDU segments packed into a PDU   Number of Retransmissions performed on the PDU   Pointer to SDU Segment Information Queue (SSIQ). Each SDU segment in a PDU has an element in the SSIQ.       

     The SSIQ maintains the following information:
         SIQ Index for an SDU to which a SDU segment belongs. This index is required to link the SDU segment information element directly to the SIQ when providing the Transmission Completion status for the application or upper layer and to release the memory of the SDU.   SDU Segment Address Offset   SDU Segment Length   SDU Segment Offset   Previous Pointer and Next Pointer to form bidirectional link between each element in the SSIQ for fast traversal through the elements in the queue.       

     The PRIQ maintains the following information:
         Sequence Number of PDU that is undergoing further segmentation and retransmission   PDU Segment Offset   SDU Segment Offset   Retransmitted PDU Size   Remaining Length to be transmitted in the PDU for next transmission       

     According to the aspects of the present invention, a field named “Number of Retransmissions” is included in the information element for the PIQ. Whenever a PDU is transmitted for the first time, the value of this field may be initialized to zero. 
     The relationship among the four queues is illustrated in  FIG. 5 . According to the ARQ protocols, the retransmissions PDUs may be prioritized over new transmissions of PDUs. Based on this prioritization of retransmission PDUs, according to the aspects of the present invention, the PRIQ stores only one PDU segment information at a given time and stores the information for the PDU or PDU segment which is currently being retransmitted. According to the aspects of the present invention, the single element in PRIQ enables performing all the data processing required for all the pending PDU retransmissions. According to an aspect of the present invention, the PRIQ may take the first PDU to be retransmitted and form the retransmission PDU which may be the same size as the first time transmitted PDU, or the retransmission PDU may be a segment of a previously transmitted PDU, or the retransmission PDU may be segment of two PDUs which were to be retransmitted as shown in  FIG. 2 . The present disclosure enables the packet data processing for retransmission scenarios at any protocol layer without using any memory copy operation. This reduces the required clock cycles for memory copy operation which may be typically performed either by a processor or a Direct Memory Access (DMA) controller. Furthermore, not performing copy operation eliminates the need for allocation of multiple memories for the same data packet. Reduced copy operations and reduced memory storage requirements may lead to reduced power consumption. 
     According to the aspects of the present invention, whenever a NACK is received for a particular PDU sequence number, it is used to traverse the PIQ and the information element for the NACKed PDU my be identified. From this information element the information about the PDU may be updated in the PRIQ. The PDU Segment Offset field may be initialized to zero. The SDU Segment Offset field may also be updated by indexing into the SSIQ using the field Pointer to SSIQ of the identified element in PIQ. The Remaining Length field may be initialized to Total Size from the PIQ. 
     When transmission resources are allocated, a PDU Segment is prepared for retransmission and the PRIQ is updated as follows:
         The Retransmitted PDU Size field is set equal to the allocated transmission resources size.   The retransmission PDU is prepared according to the allocated transmission resources size using the PDU Segment Offset and the SDU Segment Offset.       

     When a positive Transmission Completion (ACK) message is received, the PDU Sequence Number in the received message may be compared with the PDU Sequence Number field of the PRIQ. If the retransmitted PDU is positively acknowledged, the PDU Segment Offset and SDU Segment offset fields may be incremented by the value of the Retransmitted PDU Size field of the PRIQ. The Remaining Length field may be updated by subtracting the value of the Retransmitted PDU size field from the current value of the Remaining Length field. If the Remaining Length field becomes zero, the retransmission of a PDU is considered complete. The information element corresponding to the PDU Sequence Number of the original PDU in the PIQ is updated according to the aspects of the invention described in “METHOD AND APPARATUS FOR DATA PACKET PROCESSING”, filed Jan. 11, 2016, U.S. application Ser. No. 14/992,229. 
     The transmitter side processing aspects of the present invention when there is no retransmission PDU pending are illustrated in the flow diagram  600 A contained in  FIG. 6 . At processing stage  602 , the SIQ, PIQ, SSIQ, and PRIQ data structures are created. At processing stage  604 , a transmitter side protocol entity waits for a new SDU from an application or upper layer. If a new SDU is received, the processing flow continues at processing stage  606 , where the various fields of the SIQ are updated. The Start Address is updated with the memory address of the newly received SDU. The Total Size field is set equal to the size of the newly received SDU. The Remaining Length field is also set equal to the size of the newly received SDU. The Previous Pointer is set to the index of a previously received SDU. In case of a very first SDU, the Previous Pointer is set to null to indicate the end of the queue. The Next Pointer is set to the next free element in the SIQ. The processing then continues at processing stage  607 . Returning to processing stage  604 , if no new SDU is received from an application or upper layer, the processing continues at processing stage  607 . At processing stage  607 , determination is made whether transmission resources are allocated or not. If transmission resources are not allocated, the processing returns to processing stage  604 . If transmission resources are allocated, the processing continues at processing stage  608  where a PDU is prepared for transmission. Next at processing stage  610 , the next free element in PIQ is updated. The PDU Sequence Number field is updated by the next sequence number in the range 0 to N−1 as described earlier. The Total Size field is updated according to the size of the allocated resources. The Number of SDUs Packed field is updated with the total number of SDUs or SDU segments packed to form the current PDU. The Pointer to SSIQ field is updated with the index of the SSIQ which is to be updated with the information about the SDUs or SDU segments that are packed in the current PDU. Next the processing continues at processing stage  612 , where the SSIQ is updated. At processing stage  612 , the SIQ Index field is updated with the SIQ index of the SDU or the SDU segment that is packed in the current PDU. At processing stage  614 , a determination is made whether a complete SDU or a first segment of an SDU is packed in current PDU. If it is the complete SDU or the first segment of the SDU, the processing continues at processing stage  616  where the SDU Segment Address Offset field in the SSIQ is updated with the SDU Start Address. Returning to processing stage  614 , if it is not the full SDU or the first segment of the SDU, the processing continues at processing stage  618  where the SDU Segment Address Offset field of the SSIQ is updated with the value (SDU Start Address+(Total Size−Remaining Length)). The further processing after stages  616  or  618  continues at processing stage  620  where the remaining fields of the SSIQ are updated. The SDU Segment Length field is updated with the size of the SDU or SDU segment packed. The SDU Segment Offset is updated with the memory address of the PDU in which the SDU or SDU segment is packed. The Previous Pointer is updated with the index of the most recently formed entry in the SSIQ. The Next Pointer is updated with the index of the next free element in the SSIQ. The processing then continues at processing stage  622  where the Remaining Length field in the SIQ index for the SDU that is packed in the current PDU is updated as Remaining Length=Remaining Length−SDU Segment Length. At processing stage  624 , determination is made whether all the SDUs in the queue are transmitted or not. If not all the SDUs are transmitted then the processing continues at processing stage  604 . If all the SDUs are transmitted then the processing suitably terminates at stage  626 . 
     The transmitter side processing aspects of the present invention when a retransmission PDU is pending in the PRIQ are illustrated in the flow diagram  600 B contained in  FIG. 6B . At processing stage  652 , the transmitter entity waits for transmission resources allocation. When transmission resources are allocated, the processing continues at stage  654  where a PDU Segment is prepared. The Retransmitted PDU Size field is set equal to the allocated transmission resources size. The retransmission PDU is prepared according to the allocated transmission resources size using the PDU Segment Offset and the SDU Segment Offset. The processing then suitably terminates at stage  656 . The transmitter entity awaits for allocation of additional transmission resource for transmitting additional PDUs. It also waits for Transmission Completion status (ACK or NACK) from the peer entity. 
     The transmitter side processing aspects of the present invention when a positive Transmission Completion status (ACK) is received from the peer entity are illustrated in the flow diagram  700 A contained in  FIG. 7A . The processing relevant to the aspects of the present invention begins at processing stage  702 , where the transmitter entity waits for receiving Transmission Completion status from peer entity. At processing stage  704 , indication of Transmission Completion status for a PDU with a particular PDU Sequence Number is received from a peer entity. At processing stage  706 , the PIQ is searched to find the element corresponding to the Sequence Number of the successfully transmitted PDU. From the found PIQ element, the Pointer to SSIQ field is used to identify the associated element in the SSIQ. At processing stage  710 , from the identified SSIQ information element, the SIQ Index field is used to identify the SIQ information element to which the received Transmission Completion status corresponds. At processing stage  712 , determination is made whether Transmission. Completion status is received for all the SDU segments of an SDU. If the Transmission Completion status is not received for all the SDU segments of an SDU, the processing returns to the processing stage  702 . If the Transmission Completion status is received for all the SDU segments of an SDU, the processing continues at processing stage  714 . At processing stage  714 , the SIQ is updated by freeing the information element for the SDU whose transmission is completed successfully. The Previous and Next Pointers are updated to maintain the bidirectional link in the SIQ for the remaining elements in the queue. At processing stage  716 , the information elements from SSIQ corresponding to the successfully transmitted SDU segments are freed. The Previous and Next Pointers are updated to maintain the bidirectional link in the SSIQ for the remaining elements in the queue. At processing stage  718 , the information element from PIQ corresponding to the successfully transmitted PDU Sequence Number is freed. At processing stage  720 , determination is made whether all the SDUs are transmitted successfully. If not all the SDUs are transmitted successfully, the processing returns to stage  702 . Otherwise, the processing suitably terminates at stage  722 . 
     The transmitter side processing aspects of the present invention, when a negative Transmission Completion status (NACK) is received from the peer entity, are illustrated in the flow diagram  700 B contained in  FIG. 7B . The processing relevant to the present invention begins at processing stage  752 , where the transmitter entity waits for receiving Transmission Completion status from the peer entity. Also referring to  FIG. 7D , at processing stage  754 , indication of negative Transmission Completion status (NACK) for a PDU with a particular PDU Sequence Number is received from the peer entity. At processing stage  756 , the PIQ is searched to find the element corresponding to the Sequence Number of the PDU for which NACK is received. At processing stage  758 , from the found PIQ element, the Pointer to SSIQ field is used to identify the associated element in the SSIQ. At processing stage  760 , the PRIQ is updated using the information from the PIQ about the NACKed PDU. The PDU Segment offset in the PRIQ is set to zero. The SDU Segment Offset field may also be updated by indexing into the SSIQ element identified using the field Pointer to SSIQ of the identified element in PIQ. For example, in stages  754 ,  756 ,  758  and  760  and referring to  FIGS. 4 and 7D , if the NACKed PDU Sequence Number matches the PDU Sequence Number field in the element PDU(m) in the PIQ, the value of the field “Pointer to SSIQ” is read from the PDU(m). If such read value refers to the SDU segment (n) in SSIQ, from the SDU segment (n) the value of “SDU Segment Offset” field is read and written into the “SDU Segment Offset” field of the PRIQ. Further in processing stage  760 , the Remaining Length field may be initialized to Total Size from the PIQ. Now the PRIQ is ready to be used when a new transmission resources are allocated, the PDU referenced by the PRIQ may be prioritized for transmission. The processing suitably terminates at stage  762 . 
     The transmitter side processing aspects of the present invention, when a positive Transmission Completion status (ACK) is received from the peer entity for a retransmitted PDU, are illustrated in the flow diagram  700 C contained in  FIG. 7C . The processing relevant to the aspects of the present invention begins at processing stage  772 , where the transmitter entity waits for receiving Transmission Completion status from peer entity. At processing stage  74 , indication of positive Transmission Completion status (ACK) for a retransmitted PDU with a particular PDU Sequence Number is received from a peer entity. At processing stage  776 , the PRIQ is searched to find the element corresponding to the Sequence Number of the retransmitted PDU for which previously NACK was received. At processing stage  778 , a determination is made whether the received ACK is for retransmitted PDU or not. If the ACK is not for a retransmitted PDU, the processing continues with off-page reference A to the flow diagram  700 A in  FIG. 7A . If the ACK is for a retransmitted PDU, the processing continues at processing stage  780 . In the PRIQ, the PDU Segment Offset and SDU Segment Offset fields may be incremented by the value of the Retransmitted PDU Size field of the PRIQ. The Remaining Length field may be updated by subtracting the value of the Retransmitted PDU size field. At processing stage  782 , determination is made whether the Remaining Length in PRIQ has become zero. If the Remaining Length field in PRIQ becomes zero, the retransmission of a PDU is considered complete. The processing then continues with off-page reference A to the flow diagram in  FIG. 7A  where the information element corresponding to the PDU Sequence Number of the original PDU in the PIQ is updated according to the processing steps in the flow diagram  700 A. If the Remaining Length is not zero, the processing terminates for handling the currently received Transmission. Completion status and the processing flow returns to processing stage  772  where it awaits reception of next Transmission Completion status message from peer entity. 
     For the packet data processing at the reception side, similar method as that of the transmission side may be used. However, in this case PDUs are inputs and SDUs are formed as an output by the protocol entity. 
     Two different information queues are created and maintained in the receiving side to enable virtual data packet processing as shown in  FIG. 8 . Next, each of the information queues is described in detail. 
     The ReOrder Information Queue (ROIQ) maintains the following information:
         PDU Sequence Number   Total Size of the received PDU   PDU Memory Address   PDU Status which indicates whether a complete PDU or only a segment of a PDU is received   Previous and Next pointers to form bidirectional link between each element in the ROIQ for fast traversal of the elements in the queue       

     The ReAssembly Information Queue (RAIQ) maintains the following information:
         The address where the SDU or SDU segment is present in the PDU memory   SDU Segment Size   SDU Status
           SDU_COMPLETE: The SDU is non-segmented   SDU_FIRST_SEG: The SDU is segmented and is the first part of its parent SDU   o SDU_LAST_SEG: The SDU is segmented and is the last part of its parent SDU   o SDU_MIDDLE_SEG: The SDU is segmented and is an intermediate part of its parent SDU   
           Previous and Next pointers to form bidirectional link between each element in the RAIQ for fast traversal of the elements in the queue       

     The relationship among the two queues is illustrated in  FIG. 9 . According to another aspect of the present invention, the following are the steps performed in the packet data processing at the reception side when a PDU is received without a retransmission:
         1. Detect and discard duplicate PDU and do reordering of the received PDUs
           a. If the sequence number of the newly received PDU already has an entry in the ROIQ then discard the recently received PDU as duplicate.   
           2. Whenever a PDU is received that is not a duplicate, create an entry in the ROIQ and update the following information:
           a. PDU Sequence Number with the received PDU Sequence Number   b. PDU Status set to complete PDU if the PDU is complete PDU else the PDU status is set to PDU segment   c. PDU Memory Address is set to the start memory address of the received PDU stored in the system memory   d. Total Size of the PDU is set to the complete PDU size that is received   e. The Previous and Next pointer are updated to maintain the bidirectional link   
           3. After the PDU information is stored in ROIQ, check if there is a possibility for SDU reassembly and if the reassembly is possible, update the entry in the RAIQ.
           a. If there is no missing PDU sequence number up to the newly received PDU sequence number then reorder the PDUs to start the SDU reassembly   b. If an SDU is considered for reassembly then store the following information in the RAIQ:
               i. The address where the SDU or SDU segment is present in the PDU memory   ii. SDU or SDU segment size received in the PDU   iii. SDU Status set to either one of the following based on the information received in the PDU header
                   o SDU_COMPLETE: The SDU is non-segmented   o SDU_FIRST_SEG: The SDU is segmented and is the first part of its parent SDU   o SDU_LAST_SEG: The SDU is segmented and is the last part of its parent SDU   SDU_MIDDLE_SEG: The SDU is segmented and is an intermediate part of its parent SDU   
                   iv. When a complete SDU is received and when the SDU status is set to SDU_COMPLETE then deliver the complete SDU to the application or upper layer with the list consisting of memory offset and the size for each of the SDU segment that forms the complete SDU   
               
               

     The receiver side processing aspects of the present invention are illustrated in the flow diagram contained in  FIG. 10 . At processing stage  1002 , the ROIQ and RAIQ data structures are created. At processing stage  1004 , a determination is made whether a new PDU is received from a peer entity. If a new PDU is not received, the processing stays at the same stage. If a new PDU is received, the processing continues at processing stage  1006 , where the Sequence Number is extracted from the received PDU. The ROIQ is scanned to check whether there exists an entry with the same Sequence Number. At processing stage  1008 , determination is made whether the newly received PDU is a duplicate or not. If a duplicate PDU is received, the processing continues at stage  1010 , where the newly received PDU is discarded and the processing returns to the stage  1004 . If the received PDU is not a duplicate, the processing continues at processing stage  1012 , where a new entry is added in ROIQ and updated as follows. The Sequence Number field is updated with the sequence number of the received PDU. The PDU Status field is updated as either complete PDU or PDU segment depending on the received PDU headers. The PDU Memory Address field is updated with the received PDU system memory address. The Total Size field is updated with the size of the received PDU. The Previous Pointer field is updated with the ROIQ index of the previously received PDU. The Next Pointer is updated with the index of the next free element in the ROIQ. The processing then continues at stage  1014 , where determination is made whether there are any missing PDUs up to the sequence number of the newly received PDU. If there are any missing PDUs, the processing returns to the stage  1004 . If there are no missing PDUs, the processing continues at stage  1016 , where the received PDUs are reordered for reassembly. At processing stage  1018 , the reassembly of the PDUs to form an SDU is started by updating the RAIQ as follows. The Address field of the RAIQ is updated with the system memory address of the received PDU. The Segment Size field is updated with the size of the SDU or SDU segment received in the PDU. The SDU Status field is updated with one of the four possible values: SDU_COMPLETE, SDU_FIRST_SEG, SDU_LAST_SEG or SDU_MIDDLE_SEG. At processing stage  1020 , the SDU Status in the RAIQ is checked. If the SDU Status of none of the elements in RAIQ is set to SDU_COMPLETE, the processing returns to the stage  1002 . If the SDU Status is set to SDU_COMPLETE for at least one of the elements, the processing continues at processing stage  1022 , where the complete SDU is delivered to an application or upper layer by providing the list of memory address and segment size pairs from the RAIN. The processing then suitably terminates at stage  1024 . 
     According to the aspects of the present invention, the packet data processing at any layer may be performed without using any memory copy operation for retransmitted payload data. This reduces the required clock cycle for memory copy operation either from a processor or a Direct Memory Access (DMA) controller. Furthermore, not performing copy operation eliminates the need for allocation of multiple memories for the same packet data. Reduced copy operations and reduced storage requirements lead to reduced power consumption. 
     Aspects of the present invention may be applied to all types of mobile communications systems and the like, such as systems based on 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) of wireless communication standard, systems based on 3GPP Wideband Code Division Multiple Access (“WCDMA”) standard, systems based on an IEEE 802.16 wireless communication standard, etc. 
     Typically, as shown in  FIG. 11 , a wireless communication system, which is a type of data communication system, comprises elements such as client terminals or mobile stations and one or more base stations. Other network devices may also be employed, such as a mobile switching center (not shown). As illustrated in  FIG. 11 , the communication path from the base station (BS) to the client terminal or mobile station (MS) is referred to herein as a downlink (DL) direction or downlink channel, and the communication path from the client terminal to the base station is referred to herein as an uplink (UL) direction or uplink channel. In some wireless communication systems, the MS communicates with the BS in both the DL and UL directions. For instance, such communication is carried out in cellular telephone systems. In other wireless communication systems, the client terminal communicates with the base stations in only one direction, usually the DL. Such DL communication may occur in applications such as paging. As used herein, the terms “base station” and “network” are used interchangeably. 
     By way of example only, the above-described method may be implemented in a receiver, e.g., a user device such as a wireless mobile station (MS)  12  as shown in  FIG. 11 . 
     As shown in  FIG. 12 , MS  100  may include an application processor subsystem  101 , baseband subsystem  102  and a radio frequency (RF) subsystem  104  for use with a wireless communication network. A display/user interface  106  provides information to and receives input from the user. By way of example, the user interface may include one or more actuators, a speaker and a microphone. In some mobile devices, certain combination of the application processor subsystem  101 , the baseband subsystem  102  and the RF subsystem  104  are all integrated as one integrated chip. 
     The application processor subsystem  101  as shown in  FIG. 13  may include a controller  108  such as a microcontroller, another processor or other circuitry. The baseband subsystem  102  as shown in  FIG. 14  may include a controller  118  such as a microcontroller or other processor. The RF subsystem  104  as shown in  FIG. 15  may include a controller  128  such as a microcontroller, another processor or other circuitry. The controller  108  desirably handles overall operation of the MS  100 . This may be done by any combination of hardware, software and firmware running on the controller  108 . Such a combination of hardware, software and firmware may embody any methods in accordance with aspects of the present invention. 
     Peripherals  114  such as a full or partial keyboard, video or still image display, audio interface, etc may be employed and managed through the controller  108 . 
     Aspects of the present invention may be implemented in firmware of the controller  108  of the application processor and/or the controller  118  of the baseband subsystem. In another alternative, aspects of the present invention may also be implemented as a combination of firmware and hardware of the application processor subsystem  101  and/or the baseband subsystem  102 . For instance, a signal processing entity of any or all of the  FIG. 14  may be implemented in firmware, hardware and/or software. It may be part of the baseband subsystem, the receiver subsystem or be associated with both subsystems. In one example, the controller  118  and/or the signal processor  110  may include or control the protocol entity circuitry. The software may reside in internal or external memory and any data may be stored in such memory. The hardware may be an application specific integrated circuit (ASIC), field programmable gate array (FPGA), discrete logic components or any combination of such devices. The terms controller and processor are used interchangeably herein. 
     The consumer electronics devices that may use the aspects of the invention may include smartphones, tablets, laptops, gaming consoles, cameras, video camcorders, TV, car entertainment systems, etc. 
     Although aspects of the invention herein have been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the aspects of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the aspects of the present invention as defined by the appended claims. Aspects of each embodiment may be employed in the other embodiments described herein.