Pre-bundling of RLC SDUs in the RLC layer

Certain aspects of the present disclosure provide a technique for pre-bundling the received service data units (SDU) into an SDU bundle in a first communication layer before receiving a scheduling information from a second communication layer and adjusting the SDU bundle when the scheduling information is received.

TECHNICAL FIELD

Certain embodiments of the present disclosure generally relate to wireless communications and, more particularly, to pre-bundling of received service data units (SDUs) in a communication layer.

BACKGROUND

Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. This communication link may be established via a single-input-single-output, multiple-input-single-output or a multiple-input-multiple-output (MIMO) system.

In a wireless multiple-access communication system, transmitters and receivers may communicate using a multiple layer communication stack. The layers may include, for example, a physical layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a protocol layer (e.g., packet data convergence protocol (PDCP) layer), an application layer and so on. The RLC layer receives service data units (SDU) from the PDCP layer, and concatenates and/or segments the SDUs into RLC protocol data units (PDU) for transmission to the MAC layer.

SUMMARY

Certain embodiments provide a method for wireless communications. The method generally includes concatenating one or more received service data units (SDU) to generate an SDU bundle in a first communication layer, receiving a scheduling decision from a second communication layer, adjusting the SDU bundle based on the scheduling decision, and sending the adjusted SDU bundle to the second communication layer.

Certain embodiments provide an apparatus for wireless communications. The apparatus generally includes logic for concatenating one or more received service data units (SDU) to generate an SDU bundle in a first communication layer, logic for receiving a scheduling decision from a second communication layer, logic for adjusting the SDU bundle based on the scheduling decision, and logic for sending the adjusted SDU bundle to the second communication layer.

Certain embodiments provide an apparatus for wireless communications. The apparatus generally includes means for concatenating one or more received service data units (SDU) to generate an SDU bundle in a first communication layer, means for receiving a scheduling decision from a second communication layer, means for adjusting the SDU bundle based on the scheduling decision, and means for sending the adjusted SDU bundle to the second communication layer.

Certain aspects provide a computer-program product for wireless communications, comprising a computer-readable medium having instructions stored thereon, the instructions being executable by one or more processors. The instructions generally include instructions for instructions for concatenating one or more received service data units (SDU) to generate an SDU bundle in a first communication layer, instructions for receiving a scheduling decision from a second communication layer, instructions for adjusting the SDU bundle based on the scheduling decision, and instructions for sending the adjusted SDU bundle to the second communication layer.

Certain aspects of the present disclosure provide an apparatus for wireless communications. The apparatus generally includes at least one processor configured to concatenate one or more received service data units (SDU) to generate an SDU bundle in a first communication layer, receive a scheduling decision from a second communication layer, adjust the SDU bundle based on the scheduling decision, and send the adjusted SDU bundle to the second communication layer.

DETAILED DESCRIPTION

Single carrier frequency division multiple access (SC-FDMA), which utilizes single carrier modulation and frequency domain equalization is a technique. SC-FDMA has similar performance and essentially the same overall complexity as those of OFDMA system. SC-FDMA signal has lower peak-to-average power ratio (PAPR) because of its inherent single carrier structure. SC-FDMA has drawn great attention, especially in the uplink communications where lower PAPR greatly benefits the mobile terminal in terms of transmit power efficiency. It is currently a working assumption for uplink multiple access scheme in 3GPP Long Term Evolution (LTE), or Evolved UTRA.

Referring toFIG. 1, a multiple access wireless communication system according to one embodiment is illustrated. An access point100(AP) includes multiple antenna groups, one including104and106, another including108and110, and an additional including112and114. InFIG. 1, only two antennas are shown for each antenna group, however, more or fewer antennas may be utilized for each antenna group. Access terminal116(AT) is in communication with antennas112and114, where antennas112and114transmit information to access terminal116over forward link120and receive information from access terminal116over reverse link118. Access terminal122is in communication with antennas106and108, where antennas106and108transmit information to access terminal122over forward link126and receive information from access terminal122over reverse link124. In an FDD system, communication links118,120,124and126may use different frequency for communication. For example, forward link120may use a different frequency then that used by reverse link118.

Each group of antennas and/or the area in which they are designed to communicate is often referred to as a sector of the access point. In the embodiment, antenna groups each are designed to communicate to access terminals in a sector, of the areas covered by access point100.

In communication over forward links120and126, the transmitting antennas of access point100utilize beamforming in order to improve the signal-to-noise ratio of forward links for the different access terminals116and124. Also, an access point using beamforming to transmit to access terminals scattered randomly through its coverage causes less interference to access terminals in neighboring cells than an access point transmitting through a single antenna to all its access terminals.

An access point may be a fixed station used for communicating with the terminals and may also be referred to as an access point, a Node B, or some other terminology. An access terminal may also be called an access terminal, user equipment (UE), a wireless communication device, terminal, access terminal or some other terminology.

FIG. 2is a block diagram of an embodiment of a transmitter system210(also known as the access point) and a receiver system250(also known as access terminal) in a MIMO system200. At the transmitter system210, traffic data for a number of data streams is provided from a data source212to a transmit (TX) data processor214.

Pre-Bundling of RLC SDUs in the RLC Layer

Certain embodiments of the present disclosure present techniques for pre-bundling of service data units (SDU) in a communication layer in order to decrease the processing time after receiving scheduling information from other layers. An SDU is a set of data that is sent by a user of the services of a given layer, and is transmitted unchanged to a peer service user.

In a wireless communication system, transmitters and receivers may communicate using a multiple layer protocol stack.FIG. 3illustrates protocol stacks for a user equipment (UE)302and an evolved node B (eNB)304in the LTE standard. The protocol stack may include a packet data convergence protocol (PDCP) layer306, a radio link control (RLC) layer308, a medium access control (MAC) layer310and a physical (PHY) layer312. Each layer receives a plurality of SDUs from a higher layer and adds headers to the SDUs to generate protocol data units (PDU) and transmits the PDUs to a lower layer. The PDUs are treated as SDUs by the lower layer.

In the LTE standard, the RLC layer receives RLC SDUs from the PDCP layer. Upon receiving a scheduling decision from the medium access control (MAC) layer, the RLC SDUs are concatenated and/or segmented in the RLC layer to generate an RLC PDU. Since the SDUs are continually received from the protocol layer, the RLC layer should create the related RLC PDUs without delay to avoid service delays. Therefore, the segmentation and concatenation need to be completed under an absolute time budget. Complexity of segmentation and concatenation operations grows as the number of received SDUs increases.

FIG. 4illustrates an example block diagram400of the segmentation and concatenation processes performed in a radio link control (RLC) layer. A plurality of RLC SDUs402are received from a PDCP layer and stored in a buffer404in the RLC layer. When a scheduling decision is received from a MAC layer, the segmentation and concatenation block406, concatenates the received RLC SDUs and segments them according to the sizing information in the scheduling decision to generate RLC PDUs. The RLC PDUs are then sent to the MAC layer for further processing.

For certain embodiments of the present disclosure, the complexity of segmentation and concatenation processes may be reduced by pre-bundling the SDUs before receiving the scheduling decision. This may result in savings in processing time after reception of the scheduling decision, which may have a strict time budget. In one example, the RLC SDUs received from a protocol data convergence protocol (PDCP) layer may be pre-bundled at the RLC layer before the scheduling decision is received from the MAC layer. Pre-bundling the RLC SDUs may require creating appropriate RLC headers and payload. It should be noted that the pre-bundling and header creation are performed offline.

Size of an SDU bundle may change based on the average packet rate for the corresponding flow, such as internet protocol (IP) flow and so on. For certain embodiments, when a scheduling decision is received by the RLC layer, size of the SDU bundle may also be increased or decreased based on the amount of bytes scheduled. The RLC headers may also be adjusted appropriately. For certain embodiments, segmentation may be performed to fit the RLC SDUs into one or more MAC packets.

For certain embodiments, if the bundle size is the same as the amount of bytes scheduled for the RLC SDU bundle, the RLC SDU bundle may be submitted to the MAC layer as the RLC PDU with minor modifications, such as adding a serial number to the RLC SDU bundle.

For certain embodiments, the RLC SDU bundle may be treated as a PDU which is going to be re-transmitted to the MAC layer although the RLC SDU bundle has not been transmitted before. Hence, the bundle may be re-segmented, and its header can be created based on the header in the RLC SDU bundle.

FIG. 5illustrates an example block diagram500of the proposed pre-bundling and bundle adjustment technique, in accordance with certain embodiments of the present disclosure. A plurality of RLC SDUs is received from a PDCP layer and stored in a buffer404. An offline bundle creator502receives the RLC SDUs and bundles the RLC SDUs into one or more RLC SDU bundles before receiving a scheduling decision from a MAC layer. The process of concatenating the received SDUs into SDU bundles before receiving the scheduling decisions from another layer may be called ‘pre-bundling.’

The pre-bundling process may be performed based at least on an average packet rate for a corresponding protocol flow, such as an IP flow. Therefore, the offline bundle creator502generates the appropriate RLC headers and payload for the bundle. The pre-bundled RLC SDUs504may be stored in a buffer. After receiving a scheduling decision from the MAC layer, the bundle adjustor506increases or decreases the size of the RLC SDU bundle based at least on the information in the scheduling decision to generate one or more RLC PDUs.

In one example, the scheduling decision from the MAC layer may comprise a number of bytes (or other measurements of a PDU size). If the PDU size is larger than the size of the SDU bundle, the bundle adjustor506may concatenate two or more SDU bundles and then adjust (e.g., segment) the concatenated SDU bundle to generate an SDU bundle with a size equal to the PDU size in the scheduling decision. If the PDU size is smaller than the size of the SDU bundle, the bundle adjustor506may decrease the size of the SDU bundle to match the number of bytes scheduled.

For certain embodiments, by pre-bundling the SDUs, the processing resources required to create the RLC PDUs are distributed across the time domain from the time of reception of the RLC SDUs instead of the time of reception of the scheduling decision. It should be noted that adjusting the bundle after the decision is received takes less time than generating the entire bundle.

For certain embodiments of the present disclosure, the bundle created by the offline bundle creator502may be treated as a PDU that needs to be re-transmitted (e.g., in a re-transmission communication scheme, such as automatic repeat-request (ARQ), hybrid ARQ (HARM), and/or the like). The bundle may then be re-segmented by a re-transmission engine (not shown inFIG. 5). In addition, the headers may be created based on the headers that were created in the pre-bundling process.

FIG. 6illustrates the RLC bundle creation, in accordance with certain embodiments of the present disclosure. A plurality of RLC SDUs such as RLC SDU n602, RLC SDU n+1604are bundled together to generate an SDU bundle606. The SDU bundle may be created by concatenating and/or segmenting the RLC SDUs and creating a header608for the SDU bundle. When the scheduling decision is received from the MAC layer, the SDU bundle is adjusted based at least on the sizing information included in the scheduling decision. The adjusted SDU bundle610may be used to generate an RLC PDU614. A PDU header612may also be created based on the SDU bundle header608.

FIG. 7illustrates example operations500for pre-bundling SDUs, in accordance with certain embodiments of the present disclosure. At702, one or more SDUs are concatenated to generate an SDU bundle in a first communication layer. At704, a scheduling decision is received from a second communication layer. For example, the first communication layer may be an RLC layer and the second communication layer may be a MAC layer. Therefore, the RLC layer may receive RLC SDUs from a PDCP layer.

At706, the SDU bundle is adjusted based on the information included in the scheduling decision. For example, the scheduling decision may be received from the MAC layer and may include information regarding PDUs that are to be transmitted to the MAC layer, such as number of bytes expected, and/or the like.

Thus, the SDU bundle may be created before the arrival of the scheduling decision to spread processing resources over time. The SDU bundle may be adjusted once the scheduling decision is received. As described, the bundle may be adjusted by adding or removing one or more portions of one or more SDUs. At708, the adjusted SDU bundle is sent to the second layer.

Certain embodiments of the present disclosure, presented techniques to reduce the processing time at a communication layer after receiving scheduling decision from other layers by pre-bundling the SDUs and adjusting the bundle when the information in the scheduling decision becomes available.

The various operations of methods described above may be performed by various hardware and/or software component(s) and/or module(s) corresponding to means-plus-function blocks illustrated in the Figures. For example, operations700illustrated inFIG. 7correspond to means-plus-function blocks700A illustrated inFIG. 7A. More generally, where there are methods illustrated in Figures having corresponding counterpart means-plus-function Figures, the operation blocks correspond to means-plus-function blocks with similar numbering.