WO2018077417A1

WO2018077417A1 - Sequence numbers in multiple protocol layered mobile communication

Info

Publication number: WO2018077417A1
Application number: PCT/EP2016/076059
Authority: WO
Inventors: Thomas Lundgren; Philip Mansson
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2016-10-28
Filing date: 2016-10-28
Publication date: 2018-05-03

Abstract

According to an embodiment, a receiver is described, the receiver comprising: a decoder configured to a mobile communication over a radio signal; wherein the mobile communication comprises packet data successively encapsulated by a first, a second, and a third layer, wherein the layers divide a data link of the mobile communication into multiple protocol layers and the layers are logically configured on top of each other: wherein a protocol data unit (PDU) of the second layer is associated with a sequence number (SN) and wherein the SN is configured as a monotonic function; wherein a PDU of the third layer comprises a SN field including the SN of the PDU of the second layer; wherein the decoder is configured to decode the SN of each PDU of the second layer from the SN field. Furthermore, a corresponding transmitter, a method and a computer program are described.

Description

SEQUENCE NUMBERS IN MULTIPLE PROTOCOL LAYERED MOBILE

COMMUNICATION

TECHNICAL FIELD

[0001 ] The present application relates to the field of wireless

communications, and more particularly to a mobile device, a base station, a method and a protocol stack.

BACKGROUND

[0002] Telecommunication technologies have evolved from voice centric first generation to data centric all internet protocol (IP) fourth generation. During this evolution both the number of connected devices and the volume of data routed over the telecommunication networks have grown exponentially necessitating more capacity. Multiple protocols are involved in wireless communication carrying out this data. These protocols are needed to convert data, for example in the form of IP data into a form which can be communicated over wireless links reliably and efficiently. These protocols are layered as a protocol stack; being logically placed over one another such that the output of one protocol may possibly serve as an input to the next protocol. The protocol stack may be responsible for fitting data into radio and time resource channels, error checking, integrity maintenance, etc. Each protocol layer may encapsulate the data it receives from the previous layer with some additional information relevant for the layer, increasing the overall size of the data packet to be communicated. Evolution of wireless communication often aims at improving efficiency. In one aspect efficiency can be measured in number of payload data bits in relation to non-payload bits added. The non-payload bits added can, for example, be header information bits or other kind of administrative control data required for the actual data payload.

SUMMARY

[0003] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0004] It is an object of the invention to provide sequence numbers in a multiple protocol layers mobile communication. The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

[0005] According to a first aspect a receiver is provided, the receiver, comprising: a decoder configured to a mobile communication over a radio signal; wherein the mobile communication comprises packet data successively

encapsulated by a first, a second, and a third layer, wherein the layers divide a data link of the mobile communication into multiple protocol layers and the layers are logically configured on top of each other: wherein a protocol data unit (PDU) of the second layer is associated with a sequence number (SN) and wherein the SN is configured as a monotonic function; wherein a PDU of the third layer comprises a SN field including the SN of the PDU of the second layer; wherein the decoder is configured to decode the SN of each PDU of the second layer from the SN field. Having a single SN field containing information of SNs of multiple PDUs of second layer may reduce the protocol overhead and increase the efficiency of transmission as the number of non-payload bits in a third layer is decreased. A receiver able to decode such transmission may be able to receive data at a higher rate. Radio resources may be used more efficiently by using the receiver.

[0006] In a first possible implementation of the receiver according to the first aspect, a PDU of the first layer is associated with an SN, and the SN field further includes a representation of the SN of the PDU of the first layer; and the decoder is further configured to compute the SN of the PDU of the first layer from the representation in the SN field. Having a single SN field containing information of SNs of multiple PDUs of second layer and multiple PDUs of first layer may further reduce the protocol overhead and further increase the efficiency of transmission as the number of non-payload bits in a third layer PDU is decreased. A receiver able to decode such communication may be able to receive data at a higher rate. Radio resources may be used more efficiently by using the receiver. [0007] In a second possible implementation of the receiver according to the first aspect as such or according to the first implementation of the first aspect, the representation comprises an offset between the SN of the PDU of the first layer and the SN of the corresponding PDU of the second layer, so that the mobile device is configured to determine the SN of the PDU of the first layer based on the offset and the SN of the corresponding PDU of the second layer; or the mobile device is configured to determine the SN of the PDU of the second layer based on the offset and the SN of the corresponding PDU of the first layer; or the representation comprises directly the SN of the PDU of the first layer. A PDU of second layer may comprise a single PDU of first layer, resulting in a one on one correspondence between the two. Knowing an offset between the SN of PDU of first layer and the corresponding PDU of second layer, and given either the SN of the first PDU of first layer or the corresponding PDU of second layer, calculation of the other may be achieved by simple addition or modulo addition. It may be computationally less intensive to calculate one from another based on an offset between the

corresponding SNs, improving efficiency of both communication resources as the number of non-payload bits is reduced and computational resources of the receiver. Further less processing needed to obtain the SNs of PDUs of first layer and second layer may improve power efficiency of the receiver.

[0008] In a third possible implementation of the receiver according to the first aspect as such or according to any of the preceding implementations of the first aspect, the SN of the PDU of the first layer is configured as a monotonic function. Configuring the SNs of PDU of first or second layer as a monotonic function may simplify tracking and processing of SNs.

[0009] In a fourth possible implementation of the receiver according to the first aspect as such or according to any of the preceding implementations of the first aspect, the decoder is configured to determine a number and an order of SNs of PDUs of the first layer on a basis of the monotonic function and the received or determined SN of a PDU of the first layer. Since a monotonic function changes predictably, the SN of the next PDU from may be calculated by proceeding one step in the monotonic function. The calculation may be light on computing resources, improving efficiency.

[001 0] In a fifth possible implementation of the receiver according to the first aspect as such or according to any of the preceding implementations of the first aspect, the PDU of the third layer further includes a count field representing the number of SNs of PDUs of the second layer present in the mobile

communication. Including the count field representing number of PDUs of the second layer or the number of SNs thereof may simplify calculation of the individual SNs and also decapsulating of the packet.

[001 1 ] In a sixth possible implementation of the receiver according to the first aspect as such or according to any of the preceding implementations of the first aspect, the decoder is further configured to determine the number and an order of the SNs of the PDUs of the second layer on a basis of the count field and the received SN of the PDU of the second layer, wherein the received SN of the PDU of the second layer is the SN of a first PDU of the second layer. Given the number of PDUs present in the PDU of third layer or the corresponding mobile

communication, and the SN of first PDU of second layer, the SNs of other PDUs of second layer may be calculated, counting starting from the first SN till as many times as indicated by the count field. This may reduce the complexity of processing needed to calculate the SNs of individual PDUs of second layer.

[001 2] In a seventh possible implementation of the receiver according to the first aspect as such or according to any of the preceding implementations of the first aspect, the decoder is configured to determine a number and an order of SNs of PDUs of the first layer on a basis of the count field and corresponding SNs of PDUs of the second layer. Once SNs of PDUs of second layer are obtained, the receiver may obtain the SNs of PDUs of first layer as there based on a one to one correspondence between a PDU of second layer and first layer. If the SNs of PDUs of first layer are calculated in this fashion, the need to have SNs of PDUs of first layer in PDUs of second layer is eliminated, reducing non payload bits in PDUs of second layer. This may improve efficiency of the communication. [001 3] In an eighth possible implementation of the receiver according to the first aspect as such or according to any of the preceding implementations of the first aspect, a header of the PDU of third layer comprises the count field; or wherein a trailer of the PDU of the third layer comprises the count field. The count field may be located flexibly within the PDU of third layer, allowing multiple implementations of the decoding logic. This may reduce the constraints on receiver design.

[001 4] In a ninth possible implementation of the receiver according to the first aspect as such or according to any of the preceding implementations of the first aspect, the PDU of the third layer further includes a field indicating a presence of the count field. It may be advantageous to indicate whether a count field is present or not. If the count field is present, the receiver becomes aware of the number of PDUs of second layer present in the PDU of third layer. If it is absent, the receiver may determine the number of PDUs of second layer present in the PDU of third layer by other means.

[001 5] In a tenth possible implementation of the receiver according to the first aspect as such or according to any of the preceding implementations of the first aspect, the decoder is configured to compare a size of a service data unit (SDU) of the third layer and a size of the PDU of the third layer so as to determine a presence of the count field, wherein the SDU of the third layer comprises at least one PDU of the second layer and the PDU of the third layer comprises the SN field, the count field and the SDU of the third layer.

[001 6] If the field indicating the count field is absent, its presence may be computed by comparing the size of PDU of third layer with a PDU of second layer. This allows the receiver to decode PDUs of third layer whether the indication of count field is present or not.

[001 7] In an eleventh possible implementation of the receiver according to the first aspect as such or according to any of the preceding implementations of the first aspect, the decoder is configured to determine a number and an order of SN of a PDU of the second layer on a basis of the monotonic function and the received SN of a PDU of the second layer, wherein the received SN of the PDU of the second layer is the SN of the first PDU of the second layer. Given the SN of first PDU of second layer, the SNs of other PDUs of second layer may be calculated, for example by incrementing the monotonic function which the SNs follow, starting from the first SN. The function may be incremented as many times as the number of PDUs indicated by the count field. This may reduce the complexity of processing needed to calculate the SNs of individual PDUs of second layer.

[001 8] In a twelfth possible implementation of the receiver according to the first aspect as such or according to any of the preceding implementations of the first aspect, a header of the PDU of the third layer comprises the SN field; or a trailer of the PDU of the third layer comprises the SN field. The SN field may be flexibly located within the PDU of third layer, simplifying protocol and decoder design or providing support for multiple encapsulating implementations.

[001 9] According to a second aspect a transmitter is provided, the transmitter comprising: an encoder configured to a mobile communication over a radio signal; wherein the mobile communication comprises packet data

successively encapsulated by a first, a second, and a third layer, wherein the layers divide a data link of the mobile communication into multiple protocol layers and the layers are logically configured on top of each other: wherein a protocol data unit (PDU) of the second layer is associated with a sequence number (SN) and wherein the SN is configured as a monotonic function; wherein a PDU of the third layer comprises a SN field including the SN of the PDU of the second layer; and wherein the encoder is configured to encode the SN of each PDU of the second layer into the SN field. Having a single SN field containing information of SNs of multiple PDUs of second layer may reduce the protocol overhead and increase the efficiency of transmission as the number of non-payload bits in a third layer is decreased. A transmitter able to encode such transmission may be able to transmit data at a higher rate. Radio resources may be used more efficiently by using the transmitter.

[0020] In a first possible implementation of the transmitter according to the second aspect, the SN field further comprises a representation of sequence numbers (SNs) of PDUs of the first layer such that the SN of a PDU of the first layer is computable from the representation in the SN field. A PDU of second layer may comprise a single PDU of first layer, resulting in a one on one correspondence between the two. Knowing an offset between the SN of PDU of first layer and the corresponding PDU of second layer, and given either the SN of the first PDU of first layer or the corresponding PDU of second layer, calculation of the other may be achieved by simple addition or modulo addition. It may be computationally less intensive to calculate one from another based on an offset between the

corresponding SNs, improving efficiency of both communication resources as the number of non-payload bits is reduced and computational resources of the transmitter. Further less processing needed to encode the SNs of PDUs of first layer and second layer may improve power efficiency of the transmitter.

[0021 ] According to a third aspect a mobile device is provided, the mobile device comprising the receiver of the first aspect or any implementation form thereof or the transmitter of the second aspect or any implementation form thereof; or a mobile device comprising both the receiver and the transmitter. The mobile device may be able to transmit and receive data at a higher rate as the number of non-payload bits is reduced in both transmission and reception.

[0022] According to a fourth aspect a base station is provided, the base station comprising the receiver of the first aspect or any implementation form thereof or the transmitter of the second aspect or any implementation form thereof; or a base station comprising both the receiver and the transmitter. The base station may be able to transmit and receive data at a higher rate as the number of non- payload bits is reduced in both transmission and reception.

[0023] According to a fifth aspect a method is provided, the method comprising: exchanging communication over a radio signal; wherein the mobile communication comprises packet data successively encapsulated by a first, a second, and a third layer, wherein the layers divide a data link of the mobile communication into multiple protocol layers and the layers are logically configured on top of each other: wherein a protocol data unit (PDU) of the second layer is associated with a sequence number (SN) and wherein the SN is configured as a monotonic function; wherein a PDU of the third layer comprises a SN field including the SN of the PDU of the second layer; and decoding the SN of the PDU of the second layer for each PDU of the second layer from the SN field. Applying this method, communication with the number of payload bits reduced may be decoded, facilitating efficient communication. A receiver employing this method may be able to receive data at a higher rate and expend lesser power in doing so.

[0024] According to a sixth aspect a method is provided, the method comprising: exchanging mobile communication over a radio signal; wherein the mobile communication comprises packet data successively encapsulated by a first, a second, and a third layer, wherein the layers divide a data link of the mobile communication into multiple protocol layers and the layers are logically configured on top of each other: wherein a protocol data unit (PDU) of the second layer is associated with a sequence number (SN) and wherein the SN is configured as a monotonic function; wherein a PDU of the third layer comprises a SN field including the SN of the PDU of the second layer; and encoding the SN of each PDU of the second layer into the SN field. Applying this method, communication with the number of payload bits reduced may be achieved, facilitating efficient communication. A transmitter employing this method may be able to transmit data at a higher rate and expend lesser power in doing so.

[0025] In a first possible implementation of the method according to the fifth and sixth aspect, computer program comprising a program code is configured to perform the method when executed. For example a baseband processor of a mobile device or a base station may be configured to execute the program code, enabling communication in which the number of non-payload bits is decreased.

[0026] Many of the attendant features will be more readily appreciated as they become better understood by reference to the following detailed description considered in connection with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

[0027] The present description will be better understood from the following detailed description read in light of the accompanying drawings, wherein: [0028] FIG. 1 illustrates a schematic representation of a receiver configured to decode sequence numbers in a multiple protocol layered mobile communication according to an embodiment;

[0029] FIG. 2 illustrates a schematic representation of a transmitter configured to encode sequence numbers in a multiple protocol layered mobile communication according to an embodiment;

[0030] FIG. 3 illustrates a schematic representation of a transceiver configured to decode and encode sequence numbers in a multiple protocol layered mobile communication according to an embodiment;

[0031 ] FIG. 4 illustrates a schematic representation of a sequence number field and a count field in a multiple protocol layered mobile communication according to an embodiment;

[0032] FIG. 5 illustrates a schematic representation of an presence indication field for the count field in a multiple protocol layered mobile communication according to an embodiment;

[0033] FIG. 6 illustrates a schematic representation of sequence numbers in a multiple protocol layered mobile communication, wherein a presence of a count field is determined by comparing lengths of certain part of the transmission blocks according to an embodiment;

[0034] FIG. 7 illustrates a schematic representation of sequence numbers in a multiple protocol layered mobile communication without a count field according to an embodiment;

[0035] FIG. 8 illustrates a schematic representation of sequence numbers in a multiple protocol layered mobile communication, wherein sequence number information is placed at a trailer after the data unit according to an embodiment;

[0036] FIG. 9 illustrates a schematic flowchart showing a method of receiving communication having sequence numbers in a multiple protocol layered mobile communication according to an embodiment; and

[0037] FIG. 10 illustrates a schematic flowchart showing a method of transmitting communication having sequence numbers in a multiple protocol layered mobile communication according to an embodiment. [0038] Like references are used to designate like parts in the accompanying drawings.

DETAILED DESCRIPTION

[0039] The detailed description provided below in connection with the appended drawings is intended as a description of the embodiments and is not intended to represent the only forms in which the embodiment may be constructed or utilized. However, the same or equivalent functions and structures may be accomplished by different embodiments.

[0040] A mobile communication, which is conducted over a radio signal, has packet data which may be successively encapsulated by layers, for example into a first, a second and a third layer. These layers divide a data link of the mobile communication into multiple protocol layers. The layers are logically configured on top of each other. Consequently, Internet protocol (IP) packets may be conveyed accordingly, and coded into the layers. The data may be conducted within data units, such as service data unit (SDU) which are modified to form a protocol data unit (PDU) having addressing and control information, etc. This modification by layer N of the (higher) layer N+l SDU may contain encapsulation. In

encapsulation, the SDU is preserved as it is and an additional header is added by the layer N protocol. This modification may also perform concatenation, where more than one SDU is combined in a single PDU. For example SDUs coming from the upper layer may be concatenated to PDUs. Hence, one PDU can host more than one SDU. Each PDU may be assigned a sequence number (SN). SNs may be used to allow for the receiver to detect possible missing or duplicated packets and to be able to request retransmission, and to possibly perform error correction. For example, encapsulated IP packet is associated with a SN that is used for reordering of received packets and/or for encryption or decryption. SNs may be monotonically increasing numbers in a number space. SNs with respect to two different layers may be also increasing monotonically, however they may have a different SN number space. For very high bit rates it is possible that the number of IP packets become large. The normal case is that the sequence numbers are increasing monotonically one step for each IP packet.

[0041 ] Evolution of wireless communication systems often aims at improving efficiency. In one aspect efficiency can be measured in number of payload data bits in relation to non-payload bits added. The non-payload bits added can for example be header information bits or similar PDU address and control information bits. It is vital to keep the number of non-payload bits to a minimum. The embodiments enable reduction of the non-payload bits and thus increase system efficiency while not sacrificing any essential functionality of the

communication.

[0042] To improve the device efficiency and to make the protocol stack more suitable for HW acceleration the concatenation function can be moved from an upper layer to a lower layer. Here upper layer may be represented, for example by Radio Link Control, RLC, layer and lower layer by Medium Access Control, MAC, layer. However, this will require more SNs per time unit because each IP packets are sent with its own SN. Thus, no IP packets are concatenated and transmitted with the same SN.

[0043] According to an embodiment, SNs of upper layer (such as N+l) are transmitted in a SN field which is included in a PDU of a lower layer (such as N); instead of in the upper layer PDU. This may be in the form of an indication of SN for one of the PDUs of upper layer in an SN field in a lower layer, for example the first. Because the SNs are monotonic functions and on a basis of the first (or main) SN in the field, SNs for each respective PDUs may be decoded accordingly.

[0044] The format may be consequently compact and compressed. To send each possible SN, for example born by the concatenation, over the air interface is wasteful since the SN may be reconstructed in the receiver. The SN so

communicated may be used, as for the known sequence number, for arranging the data communication, identification, re-transmission, encryption or decryption, or to error correction. Additionally the SN of more than one layer, such as the upper layers, may be similarly compressed into the SN field of the lower layer and sent in the lower layer PDU administrative and control part. [0045] FIG. 1 illustrates receiver 100 comprising a decoder 101, configured to receive a communication from an input 102 and output a decoded

communication to an output 103, according to an embodiment. The input 102 may be configured to process upper layers of a multi layered protocol stack

implemented by receiver 100. In an embodiment the decoder may be integral and configured to process the whole protocol stack.

[0046] Referring to FIG. 1, the decoder 101 is configured to receive a communication comprising a packet data encapsulated in three successive layers. The first layer may take each of the packets of the packet data (which may itself comprise packet data encapsulated using a protocol stack, for example IP packets) as its service data units (SDUs) and encapsulate them into protocol data units (PDUs) of the first layer. The encapsulation may comprise appending some data, for example, to enable error correction. The second layer may take PDUs of the first layer as its SDUs and associate a serial number SN to each of the SDUs before encapsulation them into PDUs of the second layer. In some embodiments, a PDU of the second layer may comprise the SN associated with the corresponding SDU. In other embodiments, a PDU of the second layer may not include SN of the corresponding SDU. The third layer may take multiple PDUs of second layer as SDUs and associate an SN with each SDU. The SNs associated with PDUs of second layer may follow a monotonic function. A PDU of the third layer comprises an SN field containing information about SN of the SDUs of the third layer. In embodiments where a PDU of the second layer does not contain SN of the corresponding SDU of the second layer, the SN field of the third layer PDU may comprise information to represent the SNs of PDUs of second layer.

[0047] Referring again to FIG. 1, decoder 101 is configured to take data encapsulated as described above from the input 102, decode it and extract the SNs of SDUs of third layer from the SN field in the PDU of third layer. Further, in some embodiments, the decoder may obtain the SNs of SDUs of second layer. The decoder is configured to pass the decoded information to output 103. For example, on the receiver side MAC layer passes the derived SN based on the SN information in a MAC header to the receiving upper layer entity. [0048] FIG. 2 illustrates a transmitter 200 comprising an encoder 201, configured to receive a communication from an input 202 and output an encoded communication to an output 203, according to an embodiment. The input 202 may be configured to process lower layers of a multi layered protocol stack

implemented by transmitter 200. In an embodiment the encoder may be integral and configured to process the whole protocol stack.

[0049] Referring to FIG. 2, the encoder 201 is configured to receive a communication comprising a packet data and encapsulate it in three successive layers. The first layer may take each of the packets of the packet data (which may itself comprise packet data encapsulated using a protocol stack, for example IP packets) as its service data units (SDUs) and encapsulate them into protocol data units (PDUs) of the first layer. The encapsulation may comprise appending some data, for example, to enable error correction. The second layer may take PDUs of the first layer as its SDUs and associate a serial number SN to each of the SDUs before encapsulation them into PDUs of the second layer. In some embodiments, a PDU of the second layer may comprise the SN associated with the corresponding SDU. In other embodiments, a PDU of the second layer may not include SN of the corresponding SDU. The third layer may take multiple PDUs of second layer as SDUs and associate an SN with each SDU. A PDU of the third layer comprises an SN field containing information about SN of the SDUs of the third layer. In embodiments where a PDU of the second layer does not contain SN of the corresponding SDU of the second layer, the SN field of the third layer PDU may comprise information to extract the SNs of PDUs of second layer.

[0050] Referring again to FIG. 2, encoder 201 is configured to take packet data from the input 202, encode it as described above. The encoder may pass the encoded information to output 203.

[0051 ] FIG. 3 illustrates a device 300 comprising the receiver 100 of FIG. 1 and transmitter 200 of FIG. 2 according to an embodiment. According to an embodiment, device 300 is able to receive communication comprising encapsulated packet data and decode it as described in embodiments of FIG. 1. Further the device 300 is able to encode packet data as described in embodiments of FIG. 2. [0052] Referring to FIGs. 1, 2 and 3, according to an embodiment, device

100, 200 or 300 may be a base station device. According to another embodiment, device 100, 200, or 300 may be a mobile device or user equipment (UE).

[0053] Mobile device, such as the UE, may include various types of devices used directly by the end user and capable of communication in a cellular network. Such devices include but are not limited to smartphones, tablet computers, smart watches, lap top computers etc. Although embodiments may be described in terms of a mobile device and UE, it is by way of example and in no way a limitation. Further embodiments may be described in terms of a base station, it is by way of an example and in no way a limitation. A base station may include nodeBs, evolved nodeBs or any such device at the edge of a cellular network providing an air interface for UEs to connect to the cellular network.

[0054] The devices 100, 200, and 300 may be configured to perform the respective functionalities on operations described in the embodiments below, for example relating to FIGs. 4 to 10. For example, the receiver 100 may be configured to perform the receiving part of the communication and decoding, and the transmitter 200 the transmitting part of the communication and encoding.

[0055] Referring to FIG. 1, FIG. 2 and FIG. 3, according to an embodiment, the first layer, second layer and third layer may comprise sublayers of layer two in a radio access network (RAN). The first layer, second layer and third layer may respectively correspond to the Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC) layer, and Medium Access Control (MAC) layer of a Long Term Evolution (LTE) RAN or LTE advanced RAN or any subsequent RAN, for example New Radio (NR).

[0056] Although embodiments may be described in terms of certain layers such as packet data convergence protocol (PDCP) for first layer, radio link control (RLC) layer for the second layer, and a media access control (MAC) layer for the third layer, they are illustrated by way of possible embodiments only and in no way a limitation. Other than PDCP, RLC and MAC, the layers may include various types of multiple protocol layers that divide data link of the mobile

communications into multiple protocol layers, and that are logically configured on top of each other. They may, for example be used in different kind of radio access in various types of mobile communication.

[0057] According to an embodiment, the RLC SN (or information regarding the RLC SN) is sent in the MAC PDU non-payload part, such as MAC header or trailer. RLC SN is the ordinary number used by RLC, for example it may be used for the ARQ function (error correction), retransmission, reordering, encryption, etc. The RLC SN information may be represented in different ways. According to an embodiment, if only one IP packet is sent, then only that RLC SN is sent in one SN field (such as FIELD_SN) in the MAC header. According to another embodiment, if more than one IP packet is sent, then the RLC SN of one of the IP packets are sent and another field (such as a count field) in the MAC header is used together with the SN field to represent the SN of the other IP packets. This second field may be either always present, signaled via a third field, or recognized implicitly so that the other IP packets may be associated with their respective SNs based on the monotonic function of the SNs and the received SN. In alternative embodiments, instead of the count field, a bitmask, or similar type of coding method, may be used to signal the set of SNs in the communication. For example, the MAC PDU may contain a bitmask wherein a bit represents information like whether more than one IP packet is present, and other bits represent SNs of the IP packets in the MAC PDU with respect to the SN number space used. The actual SNs may be calculated, for example, by adding the SN indicated by the bit mask with SN in the SN field.

[0058] To further reduce redundancy, according to an embodiment the

PDCP SN may also be signaled in the SN field in a compressed representation. By realizing that each RLC PDU contains exactly one PDCP or encapsulated IP packet, and that the PDCP SN is increasing monotonically, for each RLC SN there is a corresponding PDCP SN within one MAC PDU. According to an embodiment, the PDCP SN may be signaled as a relationship between the PDCP SN and RLC SN. According to another embodiment, the PDCP SN may be signaled directly. According to an embodiment, both RLC SN and PDCP SN may be represented so as to extend the SN filed to include both the RLC SN and the PDCP SN. Another embodiment is to signal RLC SN and an offset to the PDCP SN, wherein the PDCP SN may be determined based on the RLC SN and the offset.

[0059] FIG. 4 illustrates a schematic representation of a SN field 307 and a count field 309 in a multiple protocol layered mobile communication according to an embodiment. FIG. 4 illustrates an embodiment of compressing SNs when a count field 309 is present and used, and shows a MAC PDU.

[0060] It should be noted that MAC PDU such as the header or the trailer may contain more data information as is illustrated in the FIGs. 4-8. For example, LTE MAC headers may also contain MAC Control Elements and also MAC padding, etc. However, for the purpose of illustration they and other data have not been described.

[0061 ] FIG. 4 illustrates an embodiment of compressing RLC SNs. A MAC header of the MAC PDU comprises the SN field 307 and the count field 309.

Additionally, the MAC PDU comprises the MAC SDU length fields 311, 315, 319 illustrating a length of the respective MAC SDUs 313, 317, and 321 having identifications MAC SDU0 to MAC SDU2 in the FIG. 4. PDCP PDUs (each comprising an IP packet) 301, 303, and 305 are contained in the respective MAC SDUs 313, 317, and 321 as illustrated by the dashed lines in FIG. 4. The SN field 307 comprises the RLC SN. An RLC PDU (not shown in FIG. 4) contains the corresponding PDCP PDU and the RLC header. In this example we assume that no concatenation is performed in the RLC layer or the PDCP layer. This results in a one-to-one mapping between PDCP SDUs and RLC PDUs. Hence, one RLC PDU contains one PDCP SDU, the PDCP SDU being designated as an IP packet. The RLC PDUs are contained in the MAC SDUs 313, 317, 321 depending on the SN. MAC PDU non-payload part is indicated by the fields 307, 309, 311, 315, and 319.

[0062] An embodiment of compressing the SN information communicates only a SN of the first RLC PDU and/or the corresponding PDCP PDU in the SN field 307 and then has the count field 309 representing how many additional, or the total number of, RLC PDUs or SNs follow the first SN that is sent in this MAC PDU. In FIG. 4 the count field 309 comprises a number 2 so that two additional

RLC PDUs comprising the corresponding PDCP PDUs (ref. 303, 317; and ref. 305, 321) follows the first one (ref. 301, 313). The SN for the respective MAC

SDUs/RLC PDUs are determined based on the SN of the first MAC SDU/RLC PDU 301,303, which is contained in the SN filed 307, and further based on the number in the count field 309 on a basis of the monotonically increasing SNs. For example a SN of the MAC SDU 313 is 0, SN of the MAC SDU 317 is 1, and SN of the MAC SDU 321 is 2. There being a one on one correspondence between an RLC PDU and a RLC SDU and between a PDCP PDU and PDCP SDU (an IP packet), given the SN of an RLC PDU, the SN of a RLC SDU/PDCP PDU and the corresponding PDCP PDU/IP packet may be calculated.

[0063] FIG. 5 illustrates a schematic representation of a presence indication field 306 for the count field 309 in a multiple protocol layered mobile

communication according to an embodiment. FIG. 5 illustrates an embodiment of compressing the SNs when a presence of the count field 309 is indicated by a third field 306. FIG. 5 is similar to FIG. 4, and further shows an embodiment of it, where the presence of the count field 309 is signaled by a presence indication field 306. In FIG. 5 it may be called "more than one RLC SDU (references 313, 317, 321) present". For example, if the field 306 has a value indicating the presence of the count field 309, the receiver may decode the count field 309 for the number of MAC SDUs. In case the field 306 has a value indicating no presence of the count field 309, the receiver may realize not to apply the count field 309.

[0064] FIG. 6 illustrates a schematic representation of SNs in a multiple protocol layered mobile communication, wherein a presence of the count field 309 is determined by comparing lengths of certain parts of the transmission blocks of the MAC layer according to an embodiment. FIG. 6 is similar to FIG. 4, and further shows an embodiment of detecting the count field 309. However, the presence of the count field 309 is derived by the receiver checking RLC SDU length against a transport block length. Because the RLC SDU is the same as MAC SDU for example in respect of the length, the receiver can detect if count field 309 is present or not by comparing the length of the MAC SDU 313 with the length of the transport block. The length of the transport block equals to the length of the MAC PDU. Consequently the size of MAC PDU and the length of MAC SDUO 311 are compared to each other.

[0065] In order for the receiver 100 to decode the received data information, the receiver 100 should know if count field 309 is present or not. By looking at the transport block size, such as the MAC PDU size, and the first MAC SDU size, the receiver knows if count field 309 is present. For example, because if the first MAC SDU 313 does not fill the complete transport block, the receiver 100 knows that more SDUs 317, 321 will follow. The count field 309 is present, and the size of the first MAC SDU 313 is different from the size of the MAC PDU with that respect, as some part of the MAC PDU actually contains the count field 309 (based on the example of FIG.6, the beginning part).

[0066] FIG. 7 illustrates a schematic representation of SNs in a multiple protocol layered mobile communication without a count field according to an embodiment. The embodiment of FIG. 7 is similar to the FIG. 4. However, the count field 309 is not signaled or contained in the MAC layer, or in any other layer. The SNs are compressed on a basis on the SN field 307 and the monotonic function of the sequence numbers. The SN of the PDU following one PDU with SN = x is implicitly set to x + 1. For example, FIG. 7 SN field 307 comprises a SN having value 0 for the first MAC SDUO 313. Sequence numbers for the MAC SDU1 307 and MAC SDU2 321 are determined by the monotonically increasing sequence numbers, such as value 1 and value 2.

[0067] FIG. 8 illustrates a schematic representation of SNs in a multiple protocol layered mobile communication, wherein SN information is placed at a trailer after the data unit according to an embodiment. The embodiment of FIG. 8 is similar to the embodiment of FIG. 4. However, in the embodiment of FIG. 8 the SN field 307, the count field 309 is contained in the MAC trailer, being after the last data packet such as the MAC SDU2 321 as shown in FIG. 8. Also the MAC SDU length fields 311, 315, and 319 are positioned after the respective MAC SDUs 313, 317, and 321. Consequently, the MAC PDU information may be positioned at the MAC trailer, instead of the MAC header. [0068] FIG. 9 illustrates a method according to an embodiment as a flow chart diagram. The method comprises operations 400 through 405. The method may be used by receivers according to embodiments of the present invention to decode packet data successively encapsulated in three multiple layers. The first layer may take each of the packets of the packet data (which may itself comprise packet data encapsulated using a protocol stack, for example IP packets) as its service data units (SDUs) and encapsulate them into protocol data units (PDUs) of the first layer. The encapsulation may comprise appending some data, for example, to enable error correction. The second layer may take PDUs of the first layer as its SDUs and associate a serial number SN to each of the SDUs before encapsulation them into PDUs of the second layer. In some embodiments, a PDU of the second layer may comprise the SN associated with the corresponding SDU. In other embodiments, a PDU of the second layer may not include SN of the corresponding SDU. The third layer may take multiple PDUs of second layer as SDUs and associate an SN with each SDU. The SNs associated with PDUs of second layer may follow a monotonic function. A PDU of the third layer comprises an SN field containing information about SN of the SDUs of the third layer. In embodiments where a PDU of the second layer does not contain SN of the corresponding SDU of the second layer, the SN field of the third layer PDU may comprise information to extract the SNs of PDUs of second layer. According to an embodiment, the PDU of third layer may contain an additional count field indicating the number of SDUs contained in the packet.

[0069] Referring to FIG. 9, operation 400 includes receiving the

successively encapsulated data from a physical layer protocol.

[0070] Operation 401 includes decapsulating a packet received from the physical layer and read a sequence number (SN) field in the packet.

[0071 ] Operation 402 includes extracting multiple SDUs of the third layer from the packet. Each of these SDUs may be PDU of second layer or may comprise some part of a PDU of second layer.

[0072] Operation 403 includes obtaining an SN for each of the extracted

SDUs based on the information in the SN field. According to an embodiment, the SN field may contain SN of the first SDU and the rest of the SNs may be calculated based on the first SDU, the monotonic function that the SNs follow and the number of SDUs contained in the packet received by the third layer. According to an embodiment the count in count field, if present, may be used to obtain the SN of each SDU of the third layer in conjunction with the monotonic function and the SN in the SN field.

[0073] Operation 405 includes passing the SDUs and their respective associated SNs to the next layer.

[0074] In some embodiments, where SDU of the second layer is associated with an SN, operation 403 may include obtaining the SN of the SDUs of second layer as well.

[0075] FIG. 10 illustrates a method according to an embodiment as a flow chart. The method may be applied by transmitters according to embodiments of the present invention on packet data to successively encapsulate it in three layers to make it suitable for processing and transmission by a physical layer protocol. The method comprises operations 410 through 416.

[0076] Operation 410 includes receiving packet data from an upper layer, for example Internet Protocol (IP) packets from the IP layer.

[0077] Operation 411 includes encapsulating each of the received packets by a first layer protocol. This layer may compress some information contained in the packet (including headers if present) and may add some data, for example for error checking.

[0078] Operation 412 includes associating a serial number (SN) with each PDU of the first layer, taking the PDU of first layer as an SDU and encapsulating using a second protocol. In some embodiments the PDU so formed may comprise the SDU and an associated SN. In other embodiments, the PDU so formed may not comprise the SN associated with the encapsulated SDU.

[0079] Operation 413 includes receiving one or more PDUs of the second layer.

[0080] Operation 414 includes associating a SN to each PDU of the second layer. [0081 ] Operation 415 includes taking one or more PDUs of second layer as

SDUs and encapsulating them using a third layer protocol into a PDU, such the PDU contains a SN field. The SN field contains information such that SN of each of the SDUs may be obtained. According to an embodiment, the SN field may contain the SN of the first SDU and the SNs of other SDUs may be calculated from the first SN. In an embodiment, SN field may further contain information about SNs of SDUs of first layer. In yet another embodiment, the third layer may encapsulate the SDUs such that the PDU of third layer comprises an additional field, for example a count field indicating the number of SDUs contained in PDU of third layer.

[0082] Operation 416 includes sending the PDUs of third layer to the physical layer for further processing and/or transmission.

[0083] Referring to FIG. 9 and FIG. 10, according to an embodiment, the first layer, second layer and third layer may comprise sublayers of layer two in a radio access network (RAN). The first layer, second layer and third layer may respectively correspond to the Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC) layer, and Medium Access Control (MAC) layer of a Long Term Evolution (LTE) RAN or LTE advanced RAN or any subsequent RAN, for example New Radio (NR).

[0084] The functionality described herein can be performed, at least in part, by one or more software or computer program components. According to an embodiment, the mobile device 100 and/or base station 200 comprise a processor configured by the program code when executed to execute the embodiments of the operations and functionality described. Furthermore the functionality described herein can be performed, at least in part, by one or more hardware logic

components. Consequently alternatively, or in addition, the functionality described herein can be performed, at least in part, by one or more hardware logic

components. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-programmable Gate Arrays (FPGAs), Program- specific Integrated Circuits (ASICs), Program- specific Standard Products (ASSPs), System-on-a-chip systems (SOCs), Complex Programmable Logic Devices (CPLDs), Graphics Processing Units (GPUs).

[0085] Any range or device value given herein may be extended or altered without losing the effect sought. Also any embodiment may be combined with another embodiment unless explicitly disallowed.

[0086] Although the subject matter has been described in language specific to structural features and/or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims.

[0087] It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item may refer to one or more of those items.

[0088] The operations of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the spirit and scope of the subject matter described herein. Aspects of any of the

embodiments described above may be combined with aspects of any of the other embodiments described to form further embodiments without losing the effect sought.

[0089] The term 'comprising' is used herein to mean including the method, blocks or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements.

[0090] It will be understood that the above description is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this specification.

Claims

1. A receiver (100), comprising:

a decoder (101) configured to a mobile communication over a radio signal; wherein the mobile communication comprises packet data successively encapsulated by a first, a second, and a third layer, wherein the layers divide a data link of the mobile communication into multiple protocol layers and the layers are logically configured on top of each other:

wherein a protocol data unit (PDU) of the second layer is associated with a sequence number (SN) and wherein the SN is configured as a monotonic function; wherein a PDU of the third layer comprises a SN field including the SN of the PDU of the second layer;

wherein the decoder (101) is configured to decode the SN of each PDU of the second layer from the SN field.

2. The receiver of claim 1, wherein a PDU of the first layer is associated with an SN, and the SN field further includes a representation of the SN of the PDU of the first layer;

and the decoder is further configured to compute the SN of the PDU of the first layer from the representation in the SN field.

3. The receiver of any preceding claim, wherein the representation comprises an offset between the SN of the PDU of the first layer and the SN of the

corresponding PDU of the second layer, so that the decoder is configured to determine the SN of the PDU of the first layer based on the offset and the SN of the corresponding PDU of the second layer; or the decoder is configured to determine the SN of the PDU of the second layer based on the offset and the SN of the corresponding PDU of the first layer; or

wherein the representation comprises directly the SN of the PDU of the first layer.

4. The receiver of any preceding claim, wherein the SN of the PDU of the first layer is configured as a monotonic function.

5. The receiver of any preceding claim, wherein the decoder is configured to determine a number and an order of SNs of PDUs of the first layer on a basis of the monotonic function and the received or determined SN of a PDU of the first layer.

6. The receiver of any preceding claim, wherein the PDU of the third layer further includes a count field representing the number of SNs of PDUs of the second layer present in the mobile communication.

7. The receiver of any preceding claim, wherein the decoder is further configured to determine the number and an order of the SNs of the PDUs of the second layer on a basis of the count field and the received SN of the PDU of the second layer, wherein the received SN of the PDU of the second layer is the SN of a first PDU of the second layer.

8. The receiver of any preceding claim, wherein the decoder is configured to determine a number and an order of SNs of PDUs of the first layer on a basis of the count field and corresponding SNs of PDUs of the second layer.

9. The receiver of any preceding claim, wherein a header of the PDU of third layer comprises the count field; or wherein a trailer of the PDU of the third layer comprises the count field.

10. The receiver of any preceding claim, wherein the PDU of the third layer further includes a field indicating a presence of the count field.

11. The receiver of any preceding claim, wherein the decoder is configured to compare a size of a service data unit (SDU) of the third layer and a size of the PDU of the third layer so as to determine a presence of the count field, wherein the SDU of the third layer comprises at least one PDU of the second layer and the PDU of the third layer comprises the SN field, the count field and the SDU of the third layer.

12. The receiver of any preceding claim, wherein the decoder is configured to determine a number and an order of SN of a PDU of the second layer on a basis of the monotonic function and the received SN of a PDU of the second layer, wherein the received SN of the PDU of the second layer is the SN of the first PDU of the second layer.

13. The receiver of any preceding claim, wherein a header of the PDU of the third layer comprises the SN field; or wherein a trailer of the PDU of the third layer comprises the SN field.

14. A transmitter (200), comprising:

an encoder (201) configured to a mobile communication over a radio signal;

wherein the mobile communication comprises packet data successively

encapsulated by a first, a second, and a third layer, wherein the layers divide a data link of the mobile communication into multiple protocol layers and the layers are logically configured on top of each other:

wherein a protocol data unit (PDU) of the second layer is associated with a sequence number (SN) and wherein the SN is configured as a monotonic function; wherein a PDU of the third layer comprises a SN field including the SN of the PDU of the second layer; and

wherein the encoder (201) is configured to encode the SN of each PDU of the second layer into the SN field.

15. The transmitter of claim 14, wherein the SN field further comprises a representation of sequence numbers (SNs) of PDUs of the first layer such that the SN of a PDU of the first layer is computable from the representation in the SN field.

16. A base station or a mobile device (300), comprising at least one of the receiver (100) of any of claims 1 to 13 or the transmitter (200) of any of claims 14 and 15.

17. A method, comprising:

exchanging (400) communication over a radio signal; wherein the mobile communication comprises packet data successively encapsulated by a first, a second, and a third layer, wherein the layers divide a data link of the mobile communication into multiple protocol layers and the layers are logically configured on top of each other:

decoding (401 , 402, 403, 404) the SN of the PDU of the second layer for each PDU of the second layer from the SN field.

18. A method, comprising:

exchanging (410) mobile communication over a radio signal; wherein the mobile communication comprises packet data successively encapsulated by a first, a second, and a third layer, wherein the layers divide a data link of the mobile communication into multiple protocol layers and the layers are logically configured on top of each other:

encoding (411, 412, 413, 414) the SN of each PDU of the second layer into the SN field.

19. A computer program comprising a program code configured to perform a method according to any of claims 17 to 18, when the computer program is executed on a computer.