WO2018082760A1

WO2018082760A1 - Reducing overhead by omitting header fields

Info

Publication number: WO2018082760A1
Application number: PCT/EP2016/076293
Authority: WO
Inventors: Samuli Heikki TURTINEN; Benoist Pierre Sebire
Original assignee: Nokia Technologies Oy
Priority date: 2016-11-01
Filing date: 2016-11-01
Publication date: 2018-05-11

Abstract

A method for reducing overhead by omitting header fields. A plurality of RLC PDUs are provided to a MAC layer of a protocol stack and at least one sequence number is removed from one or more of the plurality of RLC PDUs and at least one sequence number is retained in the plurality of RLC PDUs. The RLC PDUs are then processed at the MAC layer to form a MAC PDU, which is then passed to a physical layer of the protocol stack.

Description

Title

REDUCING OVERHEAD BY OMITTING HEADER FIELDS Field The present application relates to a method, apparatus, system and computer program and in particular but not exclusively to a method and apparatus for use in a layer 2 of a communication network.

Background

A communication system can be seen as a facility that enables communication sessions between two or more entities such as user terminals, base stations/access points and/or other nodes by providing carriers between the various entities involved in the

communications path. A communication system can be provided for example by means of a communication network and one or more compatible communication devices. The communication sessions may comprise, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and/or content data and so on. Non-limiting examples of services provided comprise two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet.

In a wireless communication system at least a part of a communication session between at least two stations occurs over a wireless link. A user can access the communication system by means of an appropriate communication device or terminal. A communication device of a user is often referred to as user equipment (UE). A communication device is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other users. The communication device may access a carrier provided by a station or access point, and transmit and/or receive communications on the carrier. The communication system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and/or parameters which shall be used for the connection are also typically defined. One example of a communications system is UTRAN (3G radio). Other examples of

communication systems are the long-term evolution (LTE) of the Universal Mobile

Telecommunications System (UMTS) radio-access technology (4G radio) and so-called 5G or New Radio (the term used by 3GPP) networks. Standardization of 5G or New Radio networks is currently under discussion. LTE is being standardized by the 3rd Generation Partnership Project (3GPP).

One of the requirements that must be taken into consideration in the development of the new radio networks is the need to support the very high bit rates required for 5G.

Summary of Invention

According to a first aspect, a method comprising: providing a plurality of RLC PDUs to a MAC layer of a protocol stack; removing at least one sequence number from one or more of the plurality of RLC PDUs; processing the plurality of RLC PDUs at the MAC layer to form a MAC PDU, wherein at least one of the plurality of RLC PDUs in the MAC PDU includes at least one sequence number; and providing the MAC PDU to a physical layer of the protocol stack.

In one embodiment, the step of processing the plurality of RLC PDUs at the MAC layer to form a MAC PDU comprises the steps of: concatenating the plurality of RLC PDUs at the MAC layer to form concatenated data; and processing the concatenated data to produce the MAC PDU.

In one embodiment, the at least one sequence number comprises a sequence number associated with a first RLC PDU in sequence in the MAC PDU.

In one embodiment, the at least one sequence number comprises a sequence number associated with a last RLC PDU in sequence in the MAC PDU. In one embodiment, the plurality of RLC PDUs comprises a first group of RLC PDUs and a second group of RLC PDUs; a last RLC PDU in sequence in the first group of RLC PDUs comprises a sequence number which is non-consecutive with a sequence number associated with a first RLC PDU in sequence in the second group of RLC PDUs; and wherein the at least one sequence number comprises: a sequence number associated with a first RLC PDU in sequence in the first group; and the sequence number associated with the first RLC PDU in sequence in the second group.

In one embodiment, the method further comprises affixing a part of a MAC header to the first group; and affixing a further part of the MAC header protocol to the second group.

In one embodiment, the method further comprises including in the part of the header an indication as to whether the last RLC PDU in sequence in the first group is a segmented RLC PDU.

In one embodiment, the method further comprises including segmentation information in at least one of the plurality of RLC PDUs in the MAC PDU, wherein the segmentation information comprises an indication as to whether the corresponding RLC PDU is a segmented RLC PDU.

In one embodiment, the at least one of the plurality of RLC PDUs consists of a first RLC PDU and a last RLC PDU in a sequence of RLC PDUs in the MAC PDUs having consecutive sequence numbers.

In one embodiment, the method further comprises removing segmentation information from one or more of the plurality of RLC PDUs, wherein at least one of the plurality of RLC PDUs in the MAC PDU includes segmentation information, wherein the segmentation information comprises an indication as to whether the corresponding RLC PDU is a segmented RLC PDU.

In one embodiment, the at least one of the plurality of RLC PDUs comprises a last RLC PDU in a sequence of RLC PDUs in the MAC PDUs having consecutive sequence numbers.

In one embodiment, the method further comprises removing one or more headers from one or more RLC PDUs, wherein a first RLC PDU in sequence in the MAC PDU includes a header.

According to a second aspect, there is provided an apparatus comprising at least one processor and at least one memory including a computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: provide a plurality of RLC PDUs to a MAC layer of a protocol stack; remove at least one sequence number from one or more of the plurality of RLC PDUs; process the plurality of RLC PDUs at the MAC layer to form a MAC PDU, wherein at least one of the plurality of RLC PDUs in the MAC PDU includes at least one sequence number; and provide the MAC PDU to a physical layer of the protocol stack.

According to a third aspect, there may be provided a method comprising providing a plurality of first protocol data packets associated with a first protocol layer of a protocol stack to a second protocol layer of the protocol stack; removing segmentation information from one or more of the plurality of first protocol data packets, wherein the segmentation information comprises an indication as to whether a corresponding data packet is a segmented data packet; processing the plurality of first protocol data packets at the second protocol layer to produce a second protocol data packet, wherein the second protocol data packet comprises segmentation information for the last data packet in a sequence of first protocol data packets in the second protocol data packet having consecutive sequence numbers; and providing the second protocol data packet to a third protocol layer of the protocol stack. In one embodiment, the step of processing the plurality of first protocol data packets at the second protocol layer to form a second protocol data packet comprises the steps of: concatenating the plurality of first protocol data packets at the second protocol layer to form concatenated data; and processing the concatenated data to produce the second protocol data packet.

According to a fourth aspect, there may be provided a method comprising: providing a plurality of first protocol data packets associated with a first protocol layer of a protocol stack to a second protocol layer of the protocol stack; removing at least one sequence number and segmentation information from one or more of the plurality of first protocol data packets, wherein the segmentation information comprises an indication as to whether a corresponding data packet is a segmented data packet; processing the plurality of first protocol data packets at the second protocol layer to produce a second protocol data packet, wherein at least one of the plurality of first protocol data packets in the second protocol data packet includes at least one sequence number; wherein the second protocol data packet comprises segmentation information for the last data packet in a sequence of first protocol data packets in the second protocol data packet having consecutive sequence numbers; and providing the second protocol data packet to a third protocol layer of the protocol stack.

In one embodiment, the step of processing the plurality of first protocol data packets at the second protocol layer to form a second protocol data packet comprises the steps of: concatenating the plurality of first protocol data packets at the second protocol layer to form concatenated data; and processing the concatenated data to produce the second protocol data packet.

According to a fifth aspect, there is a method comprising: providing a plurality of first protocol data packets associated with a first protocol layer of a protocol stack to a second protocol layer of the protocol stack; processing the plurality of first protocol data packets at the second protocol layer to produce a second protocol data packet, wherein the second protocol data packet comprises segmentation information only for the first data packet and the last data packet in a sequence of first protocol data packets in the second protocol data packet having consecutive sequence numbers, wherein the segmentation information comprises an indication as to whether a corresponding data packet is a segmented data packet; and providing the second protocol data packet to a third protocol layer of the protocol stack.

In one embodiment, the step of processing the plurality of first protocol data packets at the second protocol layer to form a second protocol data packet comprises the steps of: concatenating the plurality of first protocol data packets at the second protocol layer to form concatenated data; and processing the concatenated data to produce the second protocol data packet. According to a sixth aspect, there is a method comprising: providing a plurality of first protocol data packets associated with a first protocol layer of a protocol stack to a second protocol layer of the protocol stack; removing at least one sequence number from one or more of the plurality of first protocol data packets; processing the plurality of first protocol data packets at the second protocol layer to produce a second protocol data packet, wherein at least one of the plurality of first protocol data packets in the second protocol data packet includes at least one sequence number, wherein the second protocol data packet comprises segmentation information only for the first data packet and the last data packet in a sequence of first protocol data packets in the second protocol data packet having consecutive sequence numbers, wherein the segmentation information comprises an indication as to whether a corresponding data packet is a segmented data packet; and providing the second protocol data packet to a third protocol layer of the protocol stack.

In one embodiment, the step of processing the plurality of first protocol data packets at the second protocol layer to form a second protocol data packet comprises the steps of: concatenating the plurality of first protocol data packets at the second protocol layer to form concatenated data; and processing the concatenated data to produce the second protocol data packet. Description of Figures

Embodiments will now be described, by way of example only, with reference to the accompanying Figures in which:

Figure 1 shows a schematic diagram of an example communication system comprising a plurality of base stations and a plurality of communication devices; Figure 2 shows a schematic diagram of an example mobile communication device;

Figure 3 shows a schematic diagram of the LTE protocol stack;

Figure 4a shows an example of a PDCP PDU;

Figure 4b shows an example of an RLC PDU;

Figure 4c shows an example of a MAC PDU; Figure 5 shows an example of a MAC PDU, wherein concatenation has been performed at the RLC layer;

Figure 6 shows an example of a MAC PDU, wherein concatenation has been performed at the MAC layer;

Figure 7 shows an example of a MAC PDU, wherein concatenation has been performed at the MAC layer in accordance with embodiments of the application;

Figure 8 shows an example of a MAC PDU comprising two non-consecutive groups of RLC PDUs;

Figure 9 shows an example of a method for according to embodiments of the application; and Figure 10 shows a schematic diagram of an example control apparatus.

Detailed description Before explaining in detail the examples, certain general principles of a wireless communication system and mobile communication devices are briefly explained with reference to figures 1 to 2 to assist in understanding the technology underlying the described examples.

In a wireless communication system 100, such as that shown in figure 1 , mobile communication devices or user equipment (UE) 102, 104, 105 are provided wireless access via at least one base station or similar wireless transmitting and/or receiving node or point. A base station is referred to as an eNodeB (eNB) in LTE. Base stations are typically controlled by at least one appropriate controller apparatus, so as to enable operation thereof and management of mobile communication devices in communication with the base stations. The controller apparatus may be located in a radio access network (e.g. wireless communication system 100) or in a core network (CN) (not shown) and may be implemented as one central apparatus or its functionality may be distributed over several apparatus. The controller apparatus may be part of the base station and/or provided by a separate entity such as a Radio Network Controller. In figure 1 control apparatus 108 and 109 are shown to control the respective macro level base stations 106 and 107. In some systems, the control apparatus may additionally or alternatively be provided in a radio network controller. Compared to UTRAN, LTE systems may however be considered to have a so-called "flat" architecture, without the provision of RNCs; rather the eNB is in communication with a system architecture evolution gateway (SAE-GW) and a mobility management entity (MME), which entities may also be pooled meaning that a plurality of these nodes may serve a plurality (set) of eNBs. Each UE is served by only one MME and/or S-GW at a time and the (e)NB keeps track of current association. SAE-GW is a "high-level" user plane core network element in LTE, which may consist of the S-GW and the P-GW (serving gateway and packet data network gateway, respectively). The functionalities of the S-GW and P-GW are separated and they are not required to be co-located. In figure 1 base stations 106 and 107 are shown as connected to a wider communications network 1 13 via gateway 1 12. A further gateway function may be provided to connect to another network.

The smaller base stations 1 16, 1 18 and 120 may also be connected to the network 1 13, for example by a separate gateway function and/or via the controllers of the macro level stations. The base stations 1 16, 1 18 and 120 may be pico or femto level base stations or the like. In the example, stations 1 16 and 1 18 are connected via a gateway 1 1 1 whilst station 120 connects via the controller apparatus 108. In some embodiments, the smaller stations may not be provided.

A possible mobile communication device will now be described in more detail with reference to figure 2 showing a schematic, partially sectioned view of a communication device 200. Such a communication device is often referred to as user equipment (UE) or terminal. An appropriate mobile communication device may be provided by any device capable of sending and receiving radio signals. Non-limiting examples comprise a mobile station (MS) or mobile device such as a mobile phone or what is known as a 'smart phone', a computer provided with a wireless interface card or other wireless interface facility (e.g., USB dongle, smart watch, smart meter...), personal data assistant (PDA) or a tablet provided with wireless communication capabilities, or any combinations of these or the like. A mobile communication device may provide, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia, and so on. Users may thus be offered and provided numerous services via their communication devices. Non-limiting examples of these services comprise two-way or multi-way calls, data communication or multimedia services or simply an access to a data communications network system, such as the Internet. Users may also be provided broadcast or multicast data. Non-limiting examples of the content comprise downloads, television and radio programs, videos, advertisements, various alerts and other information.

The mobile device 200 may receive signals over an air or radio interface 207 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In figure 2 transceiver apparatus is designated schematically by block 206. The transceiver apparatus 206 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

A mobile device is typically provided with at least one data processing entity 201 , at least one memory 202 and other possible components 203 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference 204. The user may control the operation of the mobile device by means of a suitable user interface such as key pad 205, voice commands, touch sensitive screen or pad, combinations thereof or the like. A display 208, a speaker and a microphone can be also provided. Furthermore, a mobile communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto. The communication devices 102, 104, 105 may access the communication system based on various access techniques.

Reference is now made to figure 3, which provides an illustration of the UE protocol stack that is part of the LTE standard. As may be seen in the figure, the stack includes 3 different layers through which a data packet passes on the uplink, when being prepared for transmission over the network, and on the downlink, when being received from the network for delivery to the host. Embodiments of the application are directed to a method of optimising the performance of layer 2 of the protocol stack. Such optimisation may help to improve the throughput and processing efficiency of network communications, thus helping to support the requirements of the 5G systems. Layer 2 of the protocol stack comprises, a first protocol layer 301 , a second protocol layer 302, and a zeroth protocol layer 303. In this example, the first protocol layer 301 is a Radio Link Control (RLC) layer 301 , the second protocol layer 302 is a Medium Access Control (MAC) layer 302, and the zeroth protocol layer 303 is a Packet Data Convergence Protocol (PDCP) Layer 303. However, it would be understood that these are example only, and that the present application is not limited in its scope only to the LTE protocol stack, but may find application to other protocol stacks.

The RLC layer 301 is configured to receive data packets from the PDCP 303. The RLC 301 then performs the necessary processing in order to produce data packets which are passed to the MAC layer 302.The data packets passed by the RLC layer 301 to the MAC layer 302 may be referred to as RLC protocol data units (PDU) or MAC service data units (SDU). The term "service data units" refers to packets received by a layer of the stack, whilst packets output by a layer of the stack are referred to as "protocol data units". Therefore, when the term "RLC PDU" is used, this may also be understood to refer to a "MAC SDU", and vice versa.

The PDCP layer 303 receives the PDCP SDUs and then may perform at least some of the following functions to produce the PDCP PDUs: header compression and decompression, transfer of user data, ciphering & deciphering, and timer-based SDU discard. When dual connectivity is configured, PDCP may also perform reordering.

The RLC layer 301 receives the PDCP PDUs from the PDCP layer 303 and then may perform some of the following functions to produce the RLC PDUs: transfer of upper layer PDUs; error correction through ARQ; concatenation, segmentation and reassembly of RLC SDUs; re-segmentation of RLC data PDUs; reordering of RLC data PDUs; duplicate detection; and protocol error detection. The MAC layer 302 receives the RLC PDUs from the RLC layer 301 and then may perform some of the following functions to produce the MAC PDUs: Mapping between logical channels and transport channels; Multiplexing/demultiplexing of MAC SDUs belonging to one or different logical channels into/from transport blocks (TB) delivered to/from the physical layer on transport channels; Scheduling information reporting; Error correction through HARQ; Priority handling between logical channels of one UE; Priority handling between UEs by means of dynamic scheduling; Transport format selection; and Padding.

The protocol stack may include a third protocol layer 304, which in this example is a physical layer 304. However, it would be understood that the physical layer is just an example, and that the third protocol layer may take forms other than the physical layer 304. When the MAC layer 302 has processed the RLC PDUs 301 to produce the MAC PDUs 302, the MAC layer 302 may then pass the MAC PDUs to the physical layer 304. The physical layer is configured to prepare and transmit the data packets over the network to a receiving entity. The transmitting entity, which performs the above described processing and transmission of data packets, may be may comprise a user equipment (UE), such as that described above with reference to figure 2. Similarly the receiving entity, which receives the data packets from over the network may comprise a user equipment (UE), such as that described above with reference to figure 2.

Reference is made to figures 4a, 4b, and 4c. Figure 4a shows an example of a PDCP PDU 410. The PDCP PDU 410 includes a PDCP SDU 420, which is received by the PDCP layer 303, and a PDCP header 430, which is affixed to the PDCP SDU by the PDCP layer. Figure 4b shows an example of a RLC PDU 440. The RLC PDU 440 includes a RLC Payload 450 and a RLC header 460, which is affixed to the RLC payload 450 by the RLC layer 301 . The RLC payload 450 comprises one or more PDCP PDUs 410.

Figure 4c shows an example of a MAC PDU 470. The MAC PDU 470 includes a MAC Payload 480, and a MAC header 490, which is affixed to the MAC payload 480 by the MAC layer 302. The MAC payload 480 comprises one or more RLC PDUs 440. Typically when the RLC PDU 450 is produced, the RLC layer 301 concatenates a plurality of PDCP PDUs/RLC SDUs to produce the RLC payload 440 upon request from the MAC layer once the transport block size is known. Hence, concatenation of several data packets into a larger data packet is typically performed at the RLC layer 301. The concatenation function could instead or additionally be performed at the MAC layer 302. In this case, the MAC layer 302 could be configured to concatenate a plurality of RLC PDUs/MAC SDUs to produce the MAC payload 480.

There are advantages to performing the concatenation of data packets at the MAC layer that may help enable the support of higher bit rates for transmission. Specifically, moving the concatenation function from the RLC layer to the MAC layer makes is possible to be able to process the RLC PDUs offline before the grant has been received by the UE or scheduling decision for the DL transmission has been made by the network. However, there is a problem associated with performing the concatenation at the MAC layer: it increases the overhead as a result of additional header information in the final MAC PDU, since when concatenation is performed in the MAC layer, the resulting MAC PDU will include a plurality of RLC headers. However, if concatenation is performed at the RLC layer, the MAC PDU - which results after processing at the MAC layer - will typically only contain one RLC header per logical channel.

The difference in the MAC PDUs produced by different forms of concatenation is illustrated by figures 5 and 6. Reference is made to figure 5, which shows an example of a MAC PDU, wherein concatenation has taken place in the RLC layer. The MAC PDU comprises a first part of a MAC header 510, a second part of a MAC header 520, a first part of an RLC header 530, a second part of an RLC header 540, and the RLC payload 550. In this case, the RLC payload 550 comprises four PDCP PDUs that have been concatenated. The MAC payload comprises the combination of the RLC header and the RLC payload. Therefore, the MAC PDU comprises four PDCP PDUs.

The first part of the RLC header 530 comprises a sequence number SN1. The sequence number provides an indication of the order of the RLC PDU with respect to other RLC PDUs. The receiving entity is configured to inspect the sequence number in each RLC PDU header and order the RLC PDU packets in dependence upon the sequence numbers in the packets. Furthermore, the ARQ function used for the re-transmission of data packets for which a failed transmission occurs makes use of the sequence numbers in data packets for identifying data packets at the receiving entity. The RLC payload 550 comprises a plurality of PDCP PDUs that have been concatenated.

As may be seen from figure 5, in this example, the combination of the MAC header 510, 520 and the RLC header 530, 540 comprises 9 bytes of information.

Reference is made to figure 6, which shows an example of a MAC PDU, wherein concatenation has taken place in the MAC layer. The MAC PDU comprises a first part of a MAC header 510 and a plurality of RLC payloads - for example RLC payload 550. The MAC PDU comprises four RLC payloads. Each RLC payload comprises one PDCP PDU and, therefore, as in the example of figure 5, the MAC PDU comprises four PDCP PDUs.

For each RLC payload, there is provided a second part of a MAC header - for example second part of MAC header 520 - and an RLC header 530. The MAC PDU header also includes a third header part 610 comprising an indication "SDUs in LC" of how many RLC PDUs from the logical channel indicated by the Logical channel ID (LCID) in the first part of the MAC header 510 are concatenated in the MAC PDU. This enables the receiving entity to determine the logical channel of the RLC PDUs without requiring a separate LCID for each RLC PDU. Alternatively, each of the second parts of the MAC header 520 may comprise a field (e.g. an Extension field) which indicates whether the associated RLC PDU is the last RLC PDU belonging to a logical channel in the MAC PDU. In other words, the field indicates whether the RLC PDU after the associated RLC PDU belongs to the same logical channel as the associated RLC PDU. As may be seen from figure 6, in this example, the combination of the MAC header 510, 520, 610, and the RLC header 530 comprises 14 bytes of information.

Therefore, when the concatenation is performed in the MAC layer rather than RLC layer, there is an increase the number of bytes required in the MAC PDU for the storage of header information as soon as more than one RLC PDU is concatenated. This increases the overhead associated with processing and transmitting MAC PDUs.

Therefore, there is a need for a method of concatenating data packets at the MAC layer in such a way so as to reduce the amount of header information in the MAC PDU.

Embodiments of the application address this issue by omitting at least part of the RLC headers from the MAC PDU, whilst still enabling the receiving entity to determine the required information, e.g. the sequence number, for each RLC PDU. This may be achieved by including an RLC header only for the first and last RLC PDUs in the MAC PDU that are from same logical channel and that have consecutive sequence numbers. For the remaining RLC PDUs having consecutive sequence numbers, the RLC header may be removed in part or in full.

In some embodiments, the sequence numbers may not be present in the RLC headers, but may instead by present in the PDCP headers In this case, the PDCP layer may be configured to include the sequence numbers in the PDCP headers of the PDCP PDUs, which are then processed by the RLC layer to produce RLC PDUs. The processing by the RLC layer may comprise including within the RLC PDUs segmentation, polling, and data/control PDU information.

Reference is made to figure 7, which shows an example MAC PDU that has been produced by concatenation at the MAC layer in accordance with embodiments of the application. As in figure 6, the MAC PDU comprises a first part of a MAC header 510 and a plurality of RLC payloads - for example RLC payload 550. The MAC PDU comprises four RLC payloads. Each RLC payload comprises one PDCP PDU and, therefore, as in the example of figure 6, the MAC PDU comprises four PDCP PDUs. Also, as in figure 6, there is provided a second part of a MAC header - for example second part of MAC header 520 - for each RLC payload. Additionally, there may be provided a third header part 610 of the MAC header comprising an indication "SDUs in LC" of how many RLC PDUs from the logical channel indicated by the Logical channel ID (LCID) in the first part of the MAC header 510 are concatenated in the MAC PDU.

The second part of the MAC header 520 may comprise a field (MAC length field, indicated as 'L'), which indicates the size of the RLC PDU which follows the second part of the MAC header. The transmitting entity may be configured to use this field to perform MAC header precomputing.

There is provided an RLC header 530a for the first RLC PDU in the MAC PDU 700, and an RLC header 530b for the last RLC PDU in the MAC PDU 700. The RLC PDUs concatenated together in the MAC PDU have consecutive sequence numbers and, therefore, the receiving entity is configured to determine the sequence number of an RLC PDU in the MAC PDU from the sequence number of the first RLC PDU and an indication of the number of RLC PDUs concatenated in the MAC PDU. The indication of the number of RLC PDUs concatenated in the MAC PDU may be given from the field "SDUs in LC" 610. In one embodiment, the RLC header 530b of the last RLC PDU in the MAC PDU does not include a sequence number. The RLC header 530b may, however, include segmentation information. The segmentation information enables the receiving entity to determine any segmentation of a group of RLC PDUs that may have been carried out by the transmitting entity. In some embodiments, the MAC layer of the receive entity is configured to indicate to the RLC layer of the receiving entity if the segmentation was applied so that the RLC layer may determine if the header was present for the last RLC PDU of an RLC PDU group. In some embodiments, only the sequence numbers of the RLC PDUs are removed from the RLC headers. This may enable the transmission of control PDU, or ARQ information (like polling bit), or indication of segmentation of RLC SDU into RLC PDU with Framing Info (Fl) in all the RLC headers. Figure 7 illustrates an example of a MAC PDU in which all of the RLC PDUs have consecutive sequence numbers. In this case, the header information is retained for the first and last RLC PDUs in the MAC PDU. In some cases, the MAC PDU may contain a first group of RLC PDUs having consecutive sequence numbers and a second group of RLC PDUs having consecutive sequence numbers. However, there may be a discontinuity between these two groups such that the sequence numbers are not consecutive between the two groups. This may occur, for example, when one of the groups is a re-transmission (for example, an ARQ re-transmission) from a previously failed transmission and the other group is a new transmission. This may also occur, for example, when at least two discontinuous groups of RLC PDUs are being retransmitted in the same MAC PDU. In some embodiments, the MAC PDU may also contain more than two groups of RLC PDUs.

Reference is made to figure 8, which shows an example of a MAC PDU comprising two RLC PDU groups from the same logical channel. The figure additionally shows buffers from which the two groups of RLC PDUs are taken. The first buffer 801 comprises a group of RLC PDUs having consecutive sequence numbers. This group of RLC PDUs may be a group for which a previously failed transmission was previously carried out, and for which a re-transmission is to be carried out. The RLC layer may perform processing to produce the RLC PDUs, including by affixing headers including the sequence numbers to the RLC payloads, and then may pass the RLC group in the first buffer 801 to the MAC layer. Similarly, the second buffer 802 comprises a group of RLC PDUs having consecutive sequence numbers. This group of RLC PDUs may be a group for a new transmission. The RLC layer may perform processing to produce the RLC PDUs of this group, including by affixing headers including the sequence numbers to the RLC payloads, and then may pass the RLC group in the second buffer 802 to the MAC layer.

The MAC layer then performs concatenation of both groups of the RLC PDUs. The MAC layer may perform such concatenation of multiple groups of RLC PDUs, wherein each group for which concatenation is performed belongs to a different logical channel. The MAC layer may then perform processing using the resulting sets of concatenated data from different logical channels to produce the MAC PDU 800. The processing includes removing from one or more the RLC PDUs at least part of the RLC headers. The at least part of the RLC headers may include the sequence numbers. The processing additionally includes affixing a MAC subheader before each of the groups of RLC PDUs. This processing may comprise adding MAC control elements to the MAC PDU. The processing may comprise adding padding bits to the MAC PDU. In the example, the first group 805 comprises RLC PDUs having consecutive sequence numbers from 1 to 4. The second group 810 comprises RLC PDUs having consecutive sequence numbers from 8 to 10.

As shown, the first group of RLC PDUs begins with an RLC PDU having a header comprising a sequence number 815a. The last RLC PDU (which in this case is a partial/segmented RLC PDU) in the first group having consecutive sequence numbers comprises a header having a sequence number 815b. The sequence numbers have been removed from the headers of the remaining RLC PDUs in the first group 805. The sequence numbers may be removed by the MAC layer. Alternatively, the sequence numbers may be removed by the RLC layer. As noted above, the sequence number 815b may be removed from the header of the last RLC PDU in the group.

The MAC layer is configured to affix to the first group of RLC PDUs a MAC subheader 820a. The MAC subheader may comprise the at least some of the components shown in the first 510, second 520, and third 610 parts of the MAC header in figure 7.

In this example, the last RLC PDU in the first group is a segmented RLC PDU, which only contains part of the PDCP PDU. The remaining part of the PDCP PDU may be transmitted to the receiving entity as part of another RLC PDU in another group. In one embodiment, the header of the last RLC PDU in the group may include segmentation information. The segmentation information may indicate whether or not the RLC PDU is segmented. In another embodiment, the segmentation information may be included in the MAC Subheader. In one embodiment, the MAC subheader indicates with a flag if the segmentation was applied for the last RLC PDU of a RLC PDU group or not.

Also, as shown, the second group 810 of RLC PDUs begins with an RLC PDU having a header comprising a sequence number 815c. In this case, the sequence number has been removed from the last RLC PDU in the second group. The sequence numbers have also been removed by the MAC layer from the headers of the remaining RLC PDUs in the second group 810. In the case that no segmentation has been performed on the last RLC PDU of a group (as is shown for the second group 810 of figure 8) the segmentation information may also be omitted from the header of the last RLC PDU. In some embodiments, the entire RLC header of the last RLC PDU in the group may be removed from the RLC PDU.

The MAC layer is also configured to affix to the second group of RLC PDUs, a MAC subheader 820b. Therefore each group of RLC PDUs in the MAC layer having consecutive numbers may have affixed to it a separate MAC subheader. However, in the case that a group of RLC PDUs for re-transmission in the MAC PDU has sequence numbers that are consecutive with a group of RLC PDUs for new transmission in the MAC PDU, then instead of having separate MAC subheaders for each RLC group, a single MAC header may be affixed to the concatenated data.

Additionally, as shown, the MAC PDU may comprise a MAC length field, e.g. field 825, before each RLC payload. This indicates the size of the RLC payload which it precedes, and may be used to enable MAC header precomputing by the transmitting entity. In some embodiments, the MAC length fields indicating the size of the RLC payloads, may be located after the corresponding MAC header field, e.g., field 820a, and prior to the RLC payloads of the group.

In some embodiments, the MAC PDU may include at least one RLC control PDU. An RLC control PDU may not require use of a sequence number when processed at the receiving entity. In one embodiment, a separate MAC subheader may be affixed to each RLC control PDU in the MAC PDU. In another embodiment, the RLC control PDU may be concatenated with RLC Data PDUs in one of the RLC PDU groups - such as the first group 805 or second group 810 shown in figure 8 - such that the RLC control PDU is the first RLC PDU of the RLC PDU group. In this way, only a single MAC subheader may be needed for the RLC PDU group and there is no need for a separate subheader for the RLC control PDU. The RLC header of the first RLC Data PDU in RLC PDU group may retained. In this case, if the RLC group consists of a sequence of RLC PDUs, in which the first RLC PDU in the sequence is a RLC control PDU, and the second RLC PDU is a RLC Data PDU, the header of the second RLC PDU in the sequence may be retained. The transmitting entity may determine that the second RLC PDU is to be retained in dependence upon a determination that the first RLC PDU is an RLC control PDU.

In one embodiment, the transmitting entity may be configured to concatenate new transmissions of RLC PDUs adjacent to one another. The transmitting entity may be configured to concatenate re-transmissions of RLC PDUs adjacent to one another. By grouping together the same type of transmission in this way, the number of non-consecutive sequence numbers in a MAC PDU may be minimised, hence allowing more sequence numbers to be omitted.

In some embodiments, the transmitting entity may be configured to apply the methods described above in response to a signal received from the network. The signalling may be RRC or MAC signalling. In one embodiment, the UE may provide an indication to the network as to its capability to support the method.

Reference is now made to figure 9, which shows a method 900 performed at the transmitting entity for producing MAC PDUs and transmitting them over the network to a receiving entity. It would be understood by the person skilled in the art that not all of these steps are essential to the invention, and that some are optional and may be omitted in embodiments. It should furthermore be understood that the order of the steps of the method may be modified in different embodiments. Specifically, S930 and S940 may be performed in reverse order to the order presented in figure 9.

At S910, the RLC layer is configured to pass RLC PDUs to the MAC layer. These RLC PDUs may comprises one or more non-consecutive groups, which may be passed to the MAC layer in one or more separate buffers. At S920, the transmitting entity is configured to remove from at least some of the RLC headers one or more fields. The one or more fields may comprise a sequence number and an indication of whether the RLC PDU including the header is segmented. The sequence number is retained in the RLC header of the first RLC PDU in each group of RLC PDUs. At S930, the MAC layer is configured to affix at least one MAC header to the groups of RLC PDUs. If the RLC PDUs to be transmitted together all have consecutive sequence numbers, then the RLC PDUs may be concatenated (S940) and then a single MAC header may be affixed to the resulting concatenated data (i.e. the MAC payload). If the RLC PDUs consist of a plurality of groups having non-consecutive sequence numbers, then a separate MAC subheader may be affixed to each group prior to concatenation (s940). At S940, the RLC PDUs are concatenated to produce concatenated data. The concatenated data may be a MAC payload. The concatenated data is processed, e.g. by adding MAC headers, to produce a MAC PDU.

At S950, the MAC layer passes the MAC PDU to the physical layer, which transmits the MAC PDU over the network to the receiving entity.

By removing redundant information - in particular the sequence numbers - from the headers of the data packets, embodiments have the advantage that the amount of space required in the transmitted data packet for the storage of header information is reduced. This reduces the overhead resulting from storage of header information and enables higher bit rates to be achieved.

It is noted that whilst embodiments have been described in relation to one example of a standalone LTE network, similar principles may be applied in relation to other examples of standalone 3G, LTE or 5G networks. It should be noted that other embodiments may be based on other cellular technology other than LTE or on variants of LTE. Therefore, although certain embodiments were described above by way of example with reference to certain example architectures for wireless networks, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein.

It is also noted herein that while the above describes example embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

The method may additionally be implemented in a control apparatus as shown in figure 10. The method may be implanted in a single processor 201 or control apparatus or across more than one processor or control apparatus. Figure 10 shows an example of a control apparatus for a communication system, for example to be coupled to and/or for controlling a station of an access system, such as a RAN node, e.g. a base station, (e) node B, a central unit of a cloud architecture or a node of a core network such as an MME or S-GW, a scheduling entity such as a spectrum management entity, or a server or host. The control apparatus may be integrated with or external to a node or module of a core network or RAN. In some embodiments, base stations comprise a separate control apparatus unit or module. In other embodiments, the control apparatus can be another network element such as a radio network controller or a spectrum controller. In some embodiments, each base station may have such a control apparatus as well as a control apparatus being provided in a radio network controller. The control apparatus 1000 can be arranged to provide control on communications in the service area of the system. The control apparatus 1000 comprises at least one memory 1010, at least one data processing unit 1020, 1030 and an input/output interface 1040. Via the interface the control apparatus can be coupled to a receiver and a transmitter of the base station. The receiver and/or the transmitter may be implemented as a radio front end or a remote radio head. For example the control apparatus 1000 or processor 201 can be configured to execute an appropriate software code to provide the control functions. Control functions may comprise providing a plurality of RLC PDUs to a MAC layer of a protocol stack; removing at least one sequence number from one or more of the plurality of RLC PDUs; processing the plurality of RLC PDUs at the MAC layer to form a MAC PDU, wherein at least one of the plurality of RLC PDUs in the MAC PDU includes at least one sequence number; and providing the MAC PDU to a physical layer of the protocol stack.

It should be understood that the apparatuses may comprise or be coupled to other units or modules etc., such as radio parts or radio heads, used in or for transmission and/or reception. Although the apparatuses have been described as one entity, different modules and memory may be implemented in one or more physical or logical entities.

In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects of the invention may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. The embodiments of this invention may be implemented by computer software executable by a data processor of the mobile device, such as in the processor entity, or by hardware, or by a combination of software and hardware. Computer software or program, also called program product, including software routines, applets and/or macros, may be stored in any apparatus- readable data storage medium and they comprise program instructions to perform particular tasks. A computer program product may comprise one or more computer-executable components which, when the program is run, are configured to carry out embodiments. The one or more computer-executable components may be at least one software code or portions of it.

Further in this regard it should be noted that any blocks of the logic flow as in the figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD. The physical media is a non-transitory media. The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may comprise one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), FPGA, gate level circuits and processors based on multi core processor architecture, as non-limiting examples.

Embodiments of the inventions may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

The foregoing description has provided by way of non-limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention as defined in the appended claims. Indeed there is a further embodiment comprising a combination of one or more embodiments with any of the other embodiments previously discussed.

Claims

1. A method comprising:

providing a plurality of RLC PDUs to a MAC layer of a protocol stack;

removing at least one sequence number from one or more of the plurality of RLC

PDUs;

processing the plurality of RLC PDUs at the MAC layer to form a MAC PDU, wherein at least one of the plurality of RLC PDUs in the MAC PDU includes at least one sequence number; and

providing the MAC PDU to a physical layer of the protocol stack.

2. A method as claimed in claim 1 , wherein the step of processing the plurality of RLC PDUs at the MAC layer to form a MAC PDU comprises the steps of:

concatenating the plurality of RLC PDUs at the MAC layer to form concatenated data; and

processing the concatenated data to produce the MAC PDU.

3. A method as claimed in any preceding claim, wherein the at least one sequence number comprises a sequence number associated with a first RLC PDU in sequence in the

MAC PDU.

4. A method as claimed in any preceding claim, wherein the at least one sequence number comprises a sequence number associated with a last RLC PDU in sequence in the MAC PDU.

5. A method as claimed in any preceding claim, wherein:

the plurality of RLC PDUs comprises a first group of RLC PDUs and a second group of RLC PDUs;

a last RLC PDU in sequence in the first group of RLC PDUs comprises a sequence number which is non-consecutive with a sequence number associated with a first RLC PDU in sequence in the second group of RLC PDUs; and

wherein the at least one sequence number comprises:

a sequence number associated with a first RLC PDU in sequence in the first group; and

the sequence number associated with the first RLC PDU in sequence in the second group.

6. A method as claimed in claim 5, further comprising:

affixing a part of a MAC header to the first group; and

affixing a further part of the MAC header to the second group.

7. A method as claimed in claim 6, further comprising:

including in the part of the header an indication as to whether the last RLC PDU in sequence in the first group is a segmented RLC PDU.

8. A method as claimed in any preceding claim, further comprising including segmentation information in at least one of the plurality of RLC PDUs in the MAC PDU, wherein the segmentation information comprises an indication as to whether the corresponding RLC PDU is a segmented RLC PDU.

9. A method as claimed in any preceding claim, wherein the at least one of the plurality of RLC PDUs consists of a first RLC PDU and a last RLC PDU in a sequence of RLC PDUs in the MAC PDUs having consecutive sequence numbers.

10. A method as claimed in a preceding claim, further comprising removing segmentation information from one or more of the plurality of RLC PDUs, wherein at least one of the plurality of RLC PDUs in the MAC PDU includes segmentation information, wherein the segmentation information comprises an indication as to whether the corresponding RLC PDU is a segmented RLC PDU.

1 1 . A method as claimed in claim 10, wherein the at least one of the plurality of RLC PDUs comprises a last RLC PDU in a sequence of RLC PDUs in the MAC PDU having consecutive sequence numbers.

12. A method as claimed in any preceding claim, further comprising removing one or more headers from one or more RLC PDUs, wherein a first RLC PDU in sequence in the MAC

PDU includes a header.

13. An apparatus comprising:

at least one processor and at least one memory including a computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:

provide a plurality of RLC PDUs to a MAC layer of a protocol stack; remove at least one sequence number from one or more of the plurality of RLC

PDUs;

process the plurality of RLC PDUs at the MAC layer to form a MAC PDU, wherein at least one of the plurality of RLC PDUs in the MAC PDU includes at least one sequence number; and

provide the MAC PDU to a physical layer of the protocol stack.