WO2011113200A1

WO2011113200A1 - Method and apparatus for broadcasting/multicasting retransmission based on network coding

Info

Publication number: WO2011113200A1
Application number: PCT/CN2010/071107
Authority: WO
Inventors: Gang Wu; Zhenhong Li; Haifeng Wang; Wei Zou
Original assignee: Nokia Corporation
Priority date: 2010-03-17
Filing date: 2010-03-17
Publication date: 2011-09-22

Abstract

Disclosed are methods and apparatus for broadcasting or multi-casting retransmission based on network coding. In an embodiment, a source receives a request for retransmitting packets in a previous transmitted batch of packets from destination devices; in response to the request, arrange a new batch of packets including retransmission packets; allocate a network coding indicator (NCI) consisting of bits mapped to packets in a previous transmitted batch, to indicate how the mapped packet is combined in network coding for respective packet in the new batch; and broadcast or multicast the new batch of packets with the NCI to the destination devices.

Description

METHOD AND APPARATUS FOR BROADCASTING/MULTICASTING RETRANSMISSION BASED ON NETWORK CODING

TECHNICAL FIELD

The exemplaiy and non-limiting embodiments of this invention relate generally to retransmission technology in broadcasting and multicasting, and more particularly, relate to the method and apparatus for broadcasting and multicasting retransmission based on network coding.

BACKGROUND

Various abbreviations that appear in the specification and/or in the drawing figures are defined as follows:

ACK Acknowledgement

ARQ Automatic Repeat reQuest

BLER BLock Error Rate

BS Base Station

CH Cluster Head

CRC Cyclic Redundancy Check

DCCH Dedicated Control Channel

D2D Device to Device

E-MBS Enhanced Multicast and Broadcast Services

HARQ Hybrid Automatic Repeat reQuest

LTE-A Long Term Evolution - Advanced

MAC Media Access Control

MB MS Multimedia Broadcast Multicast Services

NACK Negative Acknowledgement

NC Network Coding

NCI Network Coding Indicator

NDI New Data Indicator

OPNI Original Packet Number Indicator

PDCCH Physical Downlink Control CHannel

PHY PHysical Channel

RPNI Retransmission packet Number Indicator SBM Step-down Bit Map

UE User Equipment

XOR Exclusive OR

3GPP LTE The Third Generation Partnership Project Long Term Evolution Broadcast/Multicast is one of the important services offered for example via a cellular network, where the data packets are distributed from one source to multiple destination devices. As shown in Fig. 1, the source may be embodied as a Base Station (BS), and also may be enhanced user equipment (UE) such as UE 3 in Fig. 1, or other equipments for example providing the connection between the BS and the destinations, such as a relay station (RS) or a Cluster Head (CH) device in Device-to-Device (D2D) communication.

If the data packets are sent to all destination devices, the transmission is called as broadcast. If the data packets are sent to some dedicated destination devices, the transmission is called as multicast. By utilizing the shared wireless channel, the broadcast/multicast service can reach a large number of users with constant network load, and also enables the possibility to send information simultaneously to the users.

In the broadcast/multicast transmission, if the destinations cannot receive all the data packets correctly in the first round of transmission, traditionally a HARQ/ARQ protocol is incorporated into the packet broadcast/multicast process to ensure the reliable transmission by recovering the error packets. Take an example in Table 1, Al, A2, A8 is the broadcasted packets from a source to destination devices UEl and UE2. After the first round of transmission, some packets are correctly received, and the others are not. If both UEl and UE2 send back ACK/NACK for each packet, i.e. the feedback is unicasted, the source will broadcast Al, A2, A3, A5, A6 in the second round of transmission to UEl and UE2, then total 5 time slots are needed for the retransmission (hereinafter, the "N" is denoted as NACK, and the "A" is denoted as ACK, as shown in table 1).

Table 1 ACK/NACK table for 1^st transmission (A: ACK; N: NACK)

In order to improve transmission efficiency of HARQ/ARQ, network coding (NC) can be used to the retransmission for broadcast/multicast. NC is a technique to mix the data packets efficiently in a source or an intermediate network node, and the destination devices receive these data packets and deduce the original signals transmitted from the source or the intermediate network node. In the application of NC, a batch of packets is processed for broadcasting at one time, and some packets within the batch can be XOR combined for a broadcasting/multicasting retransmission. For example, in accordance with table 1, for packet Al and A3, both of UE1 and UE2 have one correct packet and error packet within the two packets, then the source can only broadcast one packet Al © A3 ( © means XOR operation) in the retransmission for example using the simplest NC. Because UE1 has A3 received correctly, UE1 can recover Al by A3 © (Al © A3). And at the same time, because UE2 has correct Al, then UE2 can recover A3 by Al © (Al © A3).

Assume NC combinations are generally carried out in turn from the beginning to the end within the batch. A sample of the corresponding retransmission arrangement is shown in Table 2, where packets in the original batch are NC combined sequentially and each packet is only combined in NC one time. Then, the source can just broadcast A1 © A3, Α2 Φ Α5, A6 respectively at time slot Tl, T2, T3 in the second round of transmission. As such, only 3 time slots are needed for the broadcasting/multicasting retransmission. Therefore, the occupied time slots for the retransmission are saved and the transmission efficiency is improved.

Table 2 Broadcast retransmission arrangement using network coding

In a general HARQ process based on a stop-and-wait protocol, the signaling for the retransmission mainly consists of:

· New Data Indicator (NDI), whitch indicates whether the transmistted packet is a new transmission or a retransmission;

• Transport Block (TB) size, whitch indicates the number of total transmisison bits in one TB;

• HARQ process indentificator (HARQ ID), whitch indicates the serial number of a HARQ process;

• Redundancy Version (RV), whitch indicates the redundancy version of the retransmisison packets.

In the broadcast/multicast retransmission using NC, the destinations must know which packets are encoded and combined into one retransmitted packet; otherwise it cannot decode the packet retransmitted by the source. Hence, the general HARQ signaling as mentioned above are not enough to support NC, and the source needs to send the information about which packets are encoded (i.e. table 2) and combined into one retransmitted packet, called as NC indicator (NCI) here, to the destination.

Especially, when the number of the packets involved in NC increases, more time slots for broadcast/multicast retransmission will be saved, because the possibility of NC combining more packets becomes larger. But at the same time, the amount of retransmission signaling supporting the NC will be also increased greatly, because more NC encoded packets need to be indicated to destination devices. Then, how to reduce the retransmission signaling based on NC is an important issue in the broadcast/multicast retransmission.

The retransmission signaling is dependent on the feedback manner of ACK/NACK signaling. After received a packet from the source, the destination devices generally have three options of feedback manner for sending the response, including unicast feedback, common feedback and no feedback. Unicast feedback means each destination device sends back ACK/NACK signaling to the source at dedicate channels independently. Common feedback means each destination device sends back ACK/NACK signaling at a common channel. No feedback means all destination devices do not send back ACK/NACK signaling. Unicast feedback has higher transmission efficiency of broadcast/multicast than no feedback and common feedback, because the source can get detail ACK/NACK information of the destination devices and allocate as many NC combinations as possible, but obviously needs more feedback signaling. Hence unicast feedback is more suitable for the case that the number of the destination devices is not very large, for example a broadcasting/multicasting from a source of a D2D CH device and a relay station.

In the prior art, the retransmission signaling are mostly designed with respect to the manner of no feedback or common feedback. For example, in an IEEE 802.16m proposal, NC has been used in the retransmission for 16m E-MBS, and the special retransmission signaling for each packet are also proposed, such as

• Flag indicating whether the packet is encoded or not;

• Index of the coding coefficient in a pre-defined codebook ;

• Batch sequence number of the packets in the unit of batch to ensure only packet within the same number be decoded using linear operation;

· The number of original packets in one batch; • Etc..

More detailed descriptions of the special retransmission signaling for 16m E-MBS can be found in IEEE C80216m-09-1682 "Proposed Text for IEEE P802.16m/Dl: Network Coding based E-MBS Retransmission".

However, all these signaling for 16m E-MBS do not match the case of unicast feedback. The reason is that, in the case of unciast feedback, the NC combination of different packets will be based on the actual ACK/NACK state of all involved destinations within a batch, so that the NC combination cannot be informed by a pre-defined codebook as that in no feedback or common feedback.

In a 3GPP document, 3GPP TSG-RAN WG RANl#55bis Rl-090063 "Optional retransmission schemes for LTE-A MBMS", NC has been proposed in the retransmission for LTE-A MBMS, and the feedback therein is considered as a manner of unicast feedback. In the proposal, a request indicator bit (RIB) is proposed specially for retransmission signaling based on NC. However, the RIB only use one bit to show whether the packet is the retransmitted packet using NC or a new packet. How to indicate which packets are combined in NC for each retransmitted packet is not considered in the proposal.

Thus, it would be advancement in the art to provide solutions for indicating NC combination for each retransmitted packet in the case of unicast feedback in broadcasting/multicasting retransmission.

SUMMARY OF THE INVENTIONS

To overcome limitations in the prior art described above, and to overcome other limitations that will be apparent upon reading and understanding the present specification, the disclosure provides methods, apparatus and computer program products for broadcasting/multicasting retransmission based on network coding, especially a novel NC indicator for indicating network coding combination for each retransmitted packet in the broadcasting/multicasting retransmission.

In a first aspect of the exemplary embodiments of the present invention provide a method that comprises receiving a request for retransmitting packets in a previous transmitted batch of packets; in response to the request, arranging a new batch of packets including retransmission packets; allocating a NCI consisting of bits mapped to packets in a previous transmitted batch, to indicate how the mapped packet is combined in network coding for respective packet in the new batch; and broadcasting or multicasting the new batch of packets with the NCI.

In an exemplary embodiment, in response to the request, the packets requested to be retransmitted can be network encoded for generating network encoded retransmission packets, wherein the retransmission packets comprising the network encoded retransmission packets.

In an exemplary embodiment, NCI can be only allocated for each of the retransmission packets.

In an exemplary embodiment, from a NCI for each packet, one bit mapped to the packet which is mapped by the first bit of the NCI for one packet directly before said each packet, and bits before said one bit, can be removed in turn. Alternatively or additionally, from a NCI for each packet, bits mapped to packets that are combined in the network coding for packets before said each packet, can be remove.

In an exemplary embodiment, an indicator indicative of the number of packets in one batch can be informed prior to the network encoding.

In an exemplary embodiment, the retransmission packets can be arranged to be ordered sequentially before new packets in the new batch, and an indicator indicative of the number of the retransmission packets in the new batch can be informed.

In a second aspect of the exemplary embodiments of the present invention provide a method that comprises transmitting a request for retransmitting packets in a previous transmitted batch of packets; in response to the request, receiving a new batch of packets including retransmission packets and NCIs; and determining from the NCI consisting of bits mapped to packets in a previous transmitted batch, how the mapped packet is combined in network coding for respective packet in the new batch.

In an embodiment, when it is determined that respect packet in the new batch is network encoded, respective network encoded retransmission packets can be network decoded according to the determining.

In a third aspect of the exemplary embodiments of the present invention provide an apparatus comprising a transmitter; a receiver; and a controller configurable with the transmitter and the receiver to receive a request for retransmitting packets in a previous transmitted batch of packets; in response to the request, arrange a new batch of packets including retransmission packets; allocate a NCI consisting of bits mapped to packets in a previous transmitted batch, to indicate how the mapped packet is combined in network coding for respective packet in the new batch; and broadcast or multicast the new batch of packets with the NCI.

In a fourth aspect of the exemplary embodiments of the present invention provide an apparatus comprising a transmitter; a receiver; and a controller configurable with the transmitter and the receiver to transmit a request for retransmitting packets in a previous transmitted batch of packets; in response to the request, receive a new batch of packets including retransmission packets and NCIs; and determine from the NCI consisting of bits mapped to packets in a previous transmitted batch, how the mapped packet is combined in network coding for respective packet in the new batch.

In a fifth aspect of the exemplary embodiments of the present invention provide an apparatus comprising means for receiving a request for retransmitting packets in a previous transmitted batch of packets; means for in response to the request, arranging a new batch of packets including retransmission packets; means for allocating a NCI consisting of bits mapped to packets in a previous transmitted batch, to indicate how the mapped packet is combined in network coding for respective packet in the new batch; and means for broadcasting or multicasting the new batch of packets with the NCI.

In a sixth aspect of the exemplary embodiments of the present invention provide an apparatus comprising means for transmitting a request for retransmitting packets in a previous transmitted batch of packets; means for in response to the request, receiving a new batch of packets including retransmission packets and network coding indicators (NCI)s; and means for determining from the NCI consisting of bits mapped to packets in a previous transmitted batch, how the mapped packet is combined in the network coding for respective packet in the new batch.

The exemplary embodiments of the present invention also provide computer program products comprising at least one computer readable storage medium having computer program instructions stored therein, the execution of which result in operations of the methods according to the first and second aspects.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the [element, device, apparatus, component, means, step, etc]" are to be interpreted openly as referring to at least one instance of said element, device, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

Those of skill in the art will appreciate that the above is merely an introduction to the subject matter described in more detail below. Other objectives, features and advantages of the present invention will appear from the following detailed disclosure, from the attached dependent claims as well as from the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described in more detail, reference being made to the enclosed drawings, in which:

Fig. 1 illustrates a sample scenario of general broadcasting/multicasting;

Fig. 2 illustrates a sample of bit map for a first retransmission according to exemplary embodiments of the invention;

Fig. 3 illustrates a sample of bit map for a second retransmission according to the exemplary embodiments of the invention;

Fig. 4 illustrates a sample of bit map for a first retransmission according to another exemplary embodiments of the invention;

Fig. 5 illustrates a sample of bit map for a second retransmission according to another exemplary embodiments of the invention;

Figs. 6 and 7 are logic flow diagrams that illustrate the operations of methods in accordance with exemplary embodiments of the present invention; and

Fig. 8 illustrates a simplified block diagram of various devices that are suitable for use in practicing the exemplary embodiments of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

An exemplary embodiment of the present invention will be hereinafter described with reference to the drawings.

For simplicity of the expression, broadcast is assumed in the following descriptions, and as can be understood by a person skilled in the art, all that for broadcasting in the following descriptions are also applicable to multicasting.

Exemplary embodiments of the invention propose a novel solution for indicating NC combination for each retransmitted packet. In the solution, a novel NC indicator is allocated in the retransmission signaling to indicate NC combination for respective retransmission packet. The NC indicator consists of a bit map, of which each bit is mapped to packets in the previous transmitted batch to indicate how the mapped packet is combined in the network coding for the respective retransmitted packet. For example, when the first bit in a bit map for the first packet in the retransmitted batch is in a value of "1", it can mean that the first packet in the previous transmitted batch is combined in the network coding for the first retransmitted packet. A detailed description of the bit map will be described in more detail with reference to Figs. 2-5 later.

In an exemplary embodiment, a source, such as a BS, D2D CH device or a relay station, broadcast a batch of original packets to at least two destination devices (e.g. in a example assumed two UEs denoted as UE1 and UE2) during multiple HARQ processes. In an example, the number of packets in one batch can be predefined as 8. The number can be indicated through a number indicator denoted as OPNI, (for example OPNI=8, which may be indicated by 3 bits). OPNI can be a semi-static pre-configurable parameter. OPNI can be indicated inside each packet. Alternatively, OPNI can be delivered in a common control signaling, e.g. PDCCH in 3GPP LTE PHY layer, or preconfigured in the higher layer, such as DCCH in MAC layer, without being indicated inside each packet.

In the example, a signaling broadcasted from the source to the destination devices for each original packets can include NDI (called as RIB in 3GPP TSG-RAN WG RANl#55bis Rl-090063 "Optional retransmission schemes for LTE-A MBMS") and HARQ ID. For example, the signaling for the transmission of the batch of original eight packets (denoted as Al, A2, ..., A8) can be allocated as shown in table 3.

Table 3 The signaling for the original packets (I^s transmission)

As shown in table 3, the signaling for the each original packet can include NDI and HARQ ID, and optionally TB size. As the packets listed in table 3 are all new (original) packets for a new transmission, NDI=1 is configured to means the transmitted packet Al (or A2, A3, A8) is a new packet. HARQ ID indicates the serial number of a HARQ process of the transmitted packet. As can be seen, HARQ ID can indicate the order of the original packets in the batch, i.e. in an order of {Al, A2, A3, A4, A5, A6, A7, A8}. TB size can be decided according to a service requirement, and it may be larger than or equal to the length of the number of packets in one batch. It should be appreciated that table 3 is only used for the purpose of illustrating an example, not a limitation to the invention. The information of these signaling can be organized in any other appropriate form.

Then, each destination device receives the batch of original packets and corresponding signaling for the original packets, and processes the receipted packets to determine whether the original packets are received correctly. When destination devices found packets not received correctly, they can transmit a request for retransmitting the error packets to the source. For example, each of UE1 and UE2 reports the ACK/NACK for each original packet to the source, for example via respective dedicated unicast feedback channel. As a sample, ACK/NACK information for each original packet can appear as that shown in table 1. However, it should be appreciated that table 1 is only used for the purpose of giving an example, not a limitation to the invention. The ACL/NCAK information can be appears and organized in any other appropriate form.

Then, the source can collect ACK/NACK information of all destination devices, and accordingly generate retransmission packets via network coding. As a sample, the NC combination of each retransmission packets can be arranged as shown in table 2. For example, packets Al and A3 can be network encoded to generate retransmission packet Bl, packets A2 and A5 can be network encoded to generate retransmission packet B2, and packet A6 is left to be retransmitted alone as retransmission packet B6.

At the same time, the source can allocate for each retransmission packet with a respective NC indicator (NCI) consisting of a bit map, of which each bit is mapped to one original packet to indicate how the mapped original packet is combined in the NC for the respective retransmission packet. Then the source broadcasts a batch of the retransmission packets and new packets to the destination devices, together with the NCIs. As the signaling for the original packets in the first transmission, NDI, TB size, and HARQ ID can also be indicated for each packet in this round of transmission (referred as the first retransmission hereinafter). The NC indicator NDI, and HARQ ID, can be located in the head field of respective packets or the head section of the batch or TB of the first retransmission. The other related parameters, such as TB size and OPNI, can be pre-configured and located in the head field of respective retransmission packets or the head section of the batch or TB of the retransmission packets, or be signaled via a common channel just once prior to the NC adaptation.

In an example, the related signaling for the retransmission packets are listed in table 4, where B l, B2 and B6 are the retransmission packets, and B3, B4, B5, B7 and B8 are new packets. NDI=0 means that the transmitted packet is a retransmission packet. In an embodiment, if NDI shows that there is a retransmission packet, a NC indicator (NCI) is allocated for the packet; otherwise NCI is not allocated for the packet.

Table 4 The signaling for the retransmission packets (I^s retransmission)

Now reference is made to Fig. 2 illustrating details of the signaling in table 4, especially a sample of bit mapping in NCI for a first retransmission according to exemplary embodiments of the invention. As illustrated in Fig. 2, the eight rows of Packet 1, Packet 2, Packet 8 respond to packet Bl, B2, B8 respectively. Take the row of Packet 1 for example, the one block at the right-side of Packet 1 represents the indicator NDI bit for Packet 1, the block at the right-side of the row represent the data part (i.e. payload) to be carried in Bl, and the highlighted blocks between the NDI bit and the data part represent the bit map for Packet 1, to indicate the detail NC combination in the composite retransmission packet (such as Packet 1). In an example, a bit value of "1" means the original packet mapped by the bit may be combined in the networking encoding for the corresponding retransmission packet.

In an example, bit map is only provided to retransmission packets (whose NDI=0), and new packets (NDI=1) need no bit mapping of NCI.

The embodiments of the invention can provide any one of three kinds of bit mapping for NCI as follows. As shown in Fig. 2, each row of the three rows of bit map block represents one kind of bit map.

• Fixed Length Bit Map (denoted by blocks filled with diagonal lines): the actual packet combination is indicated by a NCI of a fixed length (equal to batch length). In this example the length of NCI is 8 bit for each packet. For example, the eight bits in the NCI in Packet 1 are corresponded to the eight original packets in the batch of the first transmission one by one. For example, the first bit in the NCI is corresponded to Al, the second bit is corresponded to A2, and so on. As shown in this row, bits in position I^s and 3^r are indicated as "1", which means NC Al © A3. Other bits in other position n are indicated as "0", which means the corresponding packet An are not combined in the NC for Bl.

• Fixed Step-down Bit Map (denoted by blocks filled with dots): the length of NCI for each packet can be reduced based on a fixed reduction criterion. The fixed reduction criterion is that, the NCI for each packet can be removed in turn one bit mapped to the packet which is mapped by the first bit of the NCI for one packet directly before said each packet, and bits before said one bit. That is because the original packet mapped by the removed bit has been already indicated in the NCI of the previous packet. Thus, the NCI of one packet has 1 bit less than the previous packet. For example, as shown in Fig. 2, the middle row of bit map for Packet 2 has 7 bit length with removing the bit in position 1^st, because the condition of NC combination of the first packet Al has been indicated already by the first bit of NCI for Packet 1, no mater original packet Al is NC encoded or not. And in turn, when come to the NCI for Packet 6, only three bits are included in the bit mapping. .

• Adaptive Step-down Bit Map (denoted by blocks filled with grids): the length of NCI for each packet is reduced based on a fixed criterion and an adaptive criterion. The adaptive criterion is that the NCI for each packet can be removed bits mapped to packets that are combined in the network coding for packets before said each packet. Thus, in addition to removed the first one bit in turn based on the fixed reduction criteria, the size of the bit map can be further reduced if any original packets following the first original packet have been indicated in the previous bit map. For example, as shown in Fig. 2, in addition to omitting the first bit in position 1^st, according to a fixed reduction criteria, the bottom row of bit map for Packet 2 (the second retransmission packet) has also removed a bit in 3 rd , because the condition of NC combination of the first packet Al and A3 have been all indicated by the previous bit map (i.e. bit map for Packet 1). When the destination devices receive the bit map for retransmission Packet 1, it can know that original packets Al and A3 are network encoded in Packet 1. As such, only six bits is enough for indicating Α2 Θ Α5 for Packet 2. It is similarly to Packet 6 (the third retransmission packet).

Then, the procedure return to above broadcasting receipt step, until all packets are ACK or the maximum number of retransmission has been reached. That is, each destination device receives the batch of retransmission packets and corresponding signaling, and processes the receipted packets to determine whether these packets are received correctly. If the retransmission packets are received correctly, then the destination devices such as UEl and UE2 can obtain NCI, NDI, HARQ ID, and other related parameters such as OPNI. For example, UEl and UE2 can extract NCI, NDI, and HARQ ID from the head field of respective packet, and obtain a pre-configured OPNI from a high layer or from a signaling received via a common channel just once prior to the first retransmission. Then, UEl and UE2 can network decode the respective received retransmission packets with the aid of corresponding NCI.

For example, UEl and UE2 can sequentially process packets Bl to B8 one by one according to their HARQ ID. With respect to the received packet Bl, from "NDI=0", Ul and U2 can determine Bl is a retransmission packet. Then UEl and UE2 can determine from the NCI bits mapped to packets in a previous transmitted batch, how the mapped packet is combined in the network coding for respective packet in the new batch. For example, UEl and UE2 can read the bit map (including 8 bits corresponding to Al to A8 respectively) for Bl and found only bits in the first and third positions are "1". So UEl and UE2 are aware that original packets Al and A3 are combined in the network encoding for Bl . Accordingly, UEl and UE2 can network decode Bl to derive their respective needed packet. When the process comes to the received retransmission packet B2, UEl and UE2 read the bit map for B2. In the case of taking a solution of fixed step-down bit map, UEl and UE2 have the knowledge that the bit map for B2 has 7 bits denoting A2 to A8 respectively, and bit denote to Al has been removed under the fixed reduction criteria. In the case of taking a solution of adaptive step-down bit map, UEl and UE2 have a knowledge that the bit map for B2 has 6 bits denoting A2, A4 to A8 respectively, and bits denote to Al and A3 has been removed under the fixed and adaptive reduction criteria. In both cases, UEl and UE2 can learn the NC combination of B2 and can network decode B2 accordingly.

The proposed solution can be extended to the several rounds of retransmission. If the feedback ACK/NACK table for the batch of packets transmitted in the first retransmission is shown in table 5 (noted that here ACK/NACK is for network coded packet), and thus the corresponding bit map of a second retransmission can be arranged as shown in Fig. 3.

Table 5 ACK/NACK table for 1st retransmission (A: ACK; N: NACK)

UE1 A N A A N N A A

UE2 A A N A A A N A

It can be seen that through the bit map the NC combination can be indicated using much less signaling, and thus the related resource are saved. Further, the fixed step-down bit map can save bit information compared to the fixed length bit map, and the adaptive step-down bit map can save more bit information compared to the fixed step-down bit map. The fix step-down bit map is suitable for the case that the length of bit map is fixed in each packet, while the adaptive step-down bit map is suitable for the case that the length of bit map is variable in each packet.

A simulation is carried out to show the advantages of the fixed step-down bit map and adaptive step-down bit map compared to the fixed length bit map. The main simulation parameters include:

• UE number: 2, 4, 6, or 8;

• OPNI: 8, or 16;

• BLER: 0.1, or 0.2, or 0.3.

The average bit amount of the signaling (Average bit) in the three schemes are calculated as follows:

• Fixed length bit map: Average bit =number of bits in (NDI + bit map)

• Fixed step-down: Average bit = number of bits in (NDI + bit map)

• Adaptive step-down: Average bit= number of bits in (NDI + bit map)

From the simulation results in Table 6 and Table 7, it can be seen that the proposed solutions of the fixed step-down bit map and adaptive step-down bit map can both save bits compared to fixed length scheme. The signaling amount saving is larger when OPNI, UE number and BLER increase. The reason is that the possibility of NC combination is increased. Moreover, adaptive step-down saves more bits than fixed step-down. Especially, when UE number is 8, and OPNI=16, the signaling saving of adaptive step-down is more than 60%.

6 Average signaling consumption for OPNI=16

(1) BLER=0.3

Average bit (Ada. step-down) 58 52 49 50

(2) BLER=0.2

UE number 2 4 6 8

Average bit (Fix-length) 64 67 74 80

Average bit (Fix step-down) 46 51 55 58

Average bit (Ada. step-down) 44 44 42 40

(3) BLER=0.1

UE number 2 4 6 8

Average bit (Fix-length) 44 47 48 50

Average bit (Fix step-down) 33 37 40 41

Average bit (Ada. step-down) 33 35 36 36

Table 7 Average signaling consumption for OPNI=8

(1) BLER=0.3

UE number 2 4 6 8

Average bit (Fix-length) 30 33 36 39

Average bit (Fix step-down) 22 25 26 28

Average bit (Ada. step-down) 20 20 20 20

(2) BLER=0.2

UE number 2 4 6 8

Average bit (Fix-length) 22 24 25 26

Average bit (Fix step-down) 17 19 20 21

Average bit (Ada. step-down) 16 17 17 17

(3) BLER=0.1

UE number 2 4 6 8

Average bit (Fix-length) 16 16 16 16

Average bit (Fix step-down) 14 15 15 16

Average bit (Ada. step-down) 14 15 15 16 In the embodiments of the invention as shown in figures 2 and 3, the retransmission packets (such as Bl, B2, B6, C2, C5, C6) and new packets can be blended in a batch. In another embodiment of the invention, the retransmission packets can be sent at the beginning of the batch, and followed by new packets. In this scenario, during one batch of time slots, another option to minimize signaling is to remove NDI for each retransmission packet but add an indicator with fewer bits to indicate the number of retransmission NC encoded packets. The indicator of the number of retransmission packets (referred as RPNI) could be allocated as a data packet header or signaled in a common control signaling. Examples for this scenario will be discussed with reference to tables 8-10 and figures 4 and 5 as follows.

The whole procedure of the broadcasting in this scenario are similar with the procedure described above, except that retransmission packets are arranged in series at the front of all new packets in a batch, and the NDI for each packet is removed and instead an indicator RPNI is allocated.

In short, the source broadcasts a batch of the original packets to at least two destination devices such as UEl and UE2 during the multiple HARQ processes. In the example, the signaling for the transmission of the batch of original eight packets (denoted as Al, A2, A8) can be allocated as shown in table 8. As can be seen, the difference between table 3 and 8 is that NDI for each packet is removed. Since there is no retransmission packet, this signaling does not include RPNI, or RPNI can be set to "0" to indicate there is no retransmission packet.

Table 8 The signaling for the original packets (I^s transmission)

Then, UEl and UE2 receive the batch of original packets and corresponding signaling as shown in table 8, and processes the receipted packets to determine whether the original packets are received correctly. Since UEl and UE2 found there is no RPNI (or RPNI=0), they can determine that Al to A8 are all new packets. As a result, each destination device reports the ACK/NACK information to the source, for example as that shown in table 1 to request a retransmission.

Then, the source can collect ACK/NACK information of all destination devices, and accordingly generate network encoded retransmission packets via network coding, as shown in table 2. At the same time, the source provides each retransmission packet with a respective NC indicator including a bit map according to the same way as disclosed above. Then the source broadcasts a batch including the retransmission packets and new packets to the destination devices, together with the indicators NCI. In the batch, retransmission packets are arranged in series at the front of all new packets. The signaling for the retransmission packets can include: TB size, HARQ ID, RPNI, NCI. A sample of the related signaling is listed as in Table 9.

Table 9 The signaling for the retransmission packets (I^s retransmission)

As seen in table 9, there is no NDI for packets Bl to B8. There are three retransmission packets (Packet 1, Packet 2 and Packet 3) ordered sequentially at the front of new packets B4 to B8. Thus, an indicator RPNI is allocated in the first retransmission packet (Packet 1) within the batch of retransmission packets (totally need log₂ (OPNI) = 3bits). Alternatively, RPNI can be associated with PDCCH in every 8 packet. RPNI=3 means there are total 3 time slots will be NC encoded retransmitted packets, and the following 5 time slots will be new packets.

Fig. 4 further illustrates details of the signaling in table 9. As illustrated in Fig. 4, the three blocks at the right-side of Packet 1 (highlighted by grey) represents three bits of the indicator RPNI with a value "110".

The detail bit map as shown in Fig. 4 are arranged similarly with that in Fig. 2. As to the solution of Fixed Length Bit Map, the NCI for all retransmission packets (Packet 1, Packet 2 and Packet 3) have a fixed length of 8 bits.

As to an alternative solution, i.e. Fixed Step-down Bit Map, the NCI for each packet in turn does not have, one bit mapped to the packet which is mapped by the first bit of the NCI for one packet directly before said each packet, and bits before said one bit. For Packet 2, its NCI does not have the bit in the position 1^st (corresponding to the first original packet mapped by the first bit in the NCI for Packet 1), and for Packet 3, in addition to the bit in the position 1^st, its NCI also does not have one bit in the position 2^nd (corresponding to the second original packet mapped by a first bit in the NCI for Packet 2).

As to another alternative solution, i.e. Adaptive Step-down Bit Map, the NCI for each packet is removed bits mapped to packets that are combined in the network coding for packets before said each packet. For Packet 3, bits in the position 1^st, 2^nd, 3^rd and 5^th are removed, wherein bits in the position 1^st, and 3^rd are mapped to packets Al and A3 combined in the network encoding for Packet 1, bits in the position 2^nd and 5^th are mapped to packets A2 and A5 combined in the network encoding for Packet 2. Then a bit map of only 4 bits is enough for indicating only A6 is retransmitted in Packet 3, i.e. Packet 3 involves no network coding.

Then, the procedure return to above broadcasting receipt step, until all packets are ACK or the maximum number of retransmission has been reached. If the retransmission packets are received correctly, then the destination devices such as UE1 and UE2 can obtain NCI, RPNI, and HARQ ID, and other related parameters such as OPNI, and determine from the NCI how the mapped packet is combined in the network coding for respective packet in the new batch, so as to correctly network decode the respective received retransmission packets.

The proposed solutions for this scenario can be also extended to the several rounds of retransmission.

For example, if the feedback ACK/NACK table for the first retransmission is shown in Table 10, the corresponding bit map of a second retransmission is shown in Fig. 5 (noted that here ACK/NACK is for NC encoded packet). RPNI=3 means there are 3 retransmission packets.

Table 10 ACK/NACK table for 1^st retransmission (A:ACK; N:NACK)

The simulation is also carried out to show the advantages of the fixed step-down bit map and adaptive step-down bit map compared to the fixed length bit map. The main simulation parameters include:

• UE number: 2,4,6,8

• OPNI: 8 (RPNI = 3 bits), or 16 (RPNI = 4 bits)

• BLER: 0.1, 0.2, 0.3

The average bit amount of the signaling (i.e. "Average bit") in three schemes in the above scenario are calculated as follows:

• Fixed length bit map: Average bit = (RPNI + bit map)

• Fixed step-down: Average bit = (RPNI + bit map)

• Adaptive step-down: Average bit = (RPNI + bit map)

From the simulation results in Table 11 and Table 12, it also can be seen that the proposed solutions of the fixed step-down bit map and adaptive step-down bit map can both save bits compared to fixed length scheme in the above scenario.

Table 11 Average signaling consumption for the OPNI=16

(1) BLER=0.3

(2) BLER=0.2

(3) BLER=0.1

Table 12 Average signaling consumption for OPNI=8 (1) BLER=0.3

(2) BLER=0.2

(3) BLER=0.1

Figures 6 and 7 are logic flow diagrams that illustrate the operations of methods, and a result of executions of computer program instructions, in accordance with the exemplary embodiments of this invention for broadcasting retransmission based on network coding, and more specifically is descriptive of procedure flow in a source such as BS, and destination devices, such as D2D CH device or relay station.

At block 610, there is a step of receiving a request for retransmitting packets in a previous transmitted batch of packets. . At block 620, there is a step of in response to the request, arranging a new batch of packets including retransmission packets. In a an embodiment, the network encoded retransmission packets can be arranged to be ordered sequentially before new packets in the new batch (622). At block 630, there is a step of allocating a network coding indicator (NCI) consisting of bits mapped to packets in a previous transmitted batch, to indicate how the mapped packet is combined in network coding for respective packet in the new batch. In a preferable embodiment, the NCI can be allocated only for each of the retransmission packets (632). In an embodiment, in the NCI allocating, from a NCI for each packet, one bit mapped to the packet which is mapped by the first bit of the NCI for one packet directly before said each packet, and bits before said one bit, can be removed in turn (634). Alternatively or additionally, from a NCI for each packet, bits mapped to packets that are combined in the network coding for packets before said each packet, can be removed (636). At block 640, there is a step of broadcasting or multicasting the new batch of packets with the NCI.

At block 710, there is a step of transmitting a request for retransmitting packets in a previous transmitted batch of packets. At block 720, there is a step of receiving a new batch of packets including retransmission packets and network coding indicators (NCI), in response to the request. At block 730, there is a step of determining from the NCI consisting of bits mapped to packets in a previous transmitted batch, how the mapped packet is combined in network coding for respective packet in the new batch.

The various blocks shown in figures 6 and 7 may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s).

Now reference is made to Fig. 8 illustrating a simplified block diagram of various devices that are suitable for use in practicing the exemplary embodiments of the present invention. In Fig. 8, a source such as a BS which may be referred to as BS 10 is adapted for broadcasting to at least two destination devices, such as radio communication devices which may be referred to as UE1, UE2 and UE3 (denoted as UE 12 in general).

The BS 10 includes a data processor (DP) 10A, a memory (MEM) 10B that stores a program (PROG) IOC, and a suitable radio frequency (RF) transceiver 10D for broadcasting to UE 12 via one or more antennas and receive ACK/NACK from UEs through unicast feedback. In an exemplary embodiment, the transceiver 10D in the BS 10 can be used for both broadcasting to UEs and receiving unicast feedback from UEs. Alternatively, the transceiver 10D can comprise separate components to support broadcasting and unicast feedback receiving respectively.

The UE 12 also includes a DP 12A, a MEM 12B that stores a PROG 12C, and a suitable RF transceiver 12D. In an exemplary embodiment, the transceiver 12D in the UE 12 can be used for receiving broadcasting from a source and transmitting ACK/NACK to the source through unicast feedback. Alternatively, the transceiver 12D can comprise separate components to support receiving broadcasting and the transmitting of unicast feedback respectively.

At least one of the PROGs IOC, 12C is assumed to include program instructions that, when executed by the associated DP, enable the electronic device to operate in accordance with the exemplary embodiments of this invention, as discussed above. That is, the exemplary embodiments of this invention may be implemented at least in part by computer software executable by the DP 10A of the BS 10 and by the DP 12A of the UE 12, or by hardware, or by a combination of software and hardware. The basic structure and operation of BS 10 and UE 12 are known to one skilled in the art.

The MEMs 10B and 12B 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, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The DPs 10A and 12A may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multi-core processor architectures, as non-limiting examples.

In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects 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 exemplary embodiments of this 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.

As such, it should be appreciated that at least some aspects of the exemplary embodiments of the inventions may be practiced in various components such as integrated circuit chips and modules. It should thus be appreciated that the exemplary embodiments of this invention may be realized in an apparatus that is embodied as an integrated circuit, where the integrated circuit may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor, a digital signal processor, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this invention.

It should be appreciated that at least some aspects of the exemplary embodiments of the inventions may be embodied in computer-executable instructions, such as in one or more program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types when executed by a processor in a computer or other device. The computer executable instructions may be stored on a computer readable medium such as a hard disk, optical disk, removable storage media, solid state memory, RAM, etc. As will be appreciated by one of skill in the art, the functionality of the program modules may be combined or distributed as desired in various embodiments. In addition, the functionality may be embodied in whole or in part in firmware or hardware equivalents such as integrated circuits, field programmable gate arrays (FPGA), and the like. The present invention includes any novel feature or combination of features disclosed herein either explicitly or any generalization thereof. Various modifications and adaptations to the foregoing exemplary embodiments of this invention may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. However, any and all modifications will still fall within the scope of the non-Limiting and exemplary embodiments of this invention.

Claims

CLAMS What is claimed is:

1. A method, comprising:

receiving a request for retransmitting packets in a previous transmitted batch of packets;

in response to the request, arranging a new batch of packets including retransmission packets;

allocating a network coding indicator (NCI) consisting of bits mapped to packets in a previous transmitted batch, to indicate how the mapped packet is combined in network coding for respective packet in the new batch; and

broadcasting or multicasting the new batch of packets with the NCI.

2. The method of claim 1, further comprises:

in response to the request, network encoding the packets requested to be retransmitted for generating network encoded retransmission packets,

wherein the retransmission packets comprising the network encoded retransmission packets.

3. The method of claim 1, wherein allocating NCI only for each of the retransmission packets.

4. The method of claim 2, wherein allocating NCI further comprising: removing in turn from a NCI for each packet, one bit mapped to the packet which is mapped by the first bit of the NCI for one packet directly before said each packet, and bits before said one bit.

5. The method of any one of claims 1 to 4, wherein allocating NCI further comprising: removing from a NCI for each packet, bits mapped to packets that are combined in the network coding for packets before said each packet.

6. The method of any one of claims 1 to 4, further comprises informing an indicator indicative of the number of packets in one batch prior to the network encoding.

7. The method of any one of claims 1 to 4, wherein the retransmission packets are arranged to be ordered sequentially before new packets in the new batch, and the method further comprises informing an indicator indicative of the number of the retransmission packets in the new batch.

8. A method, comprising:

transmitting a request for retransmitting packets in a previous transmitted batch of packets;

in response to the request, receiving a new batch of packets including retransmission packets and network coding indicators (NCI); and

determining from the NCI consisting of bits mapped to packets in a previous transmitted batch, how the mapped packet is combined in network coding for respective packet in the new batch.

9. The method of claim 8, the method further comprises:

when it is determined that respect packet in the new batch is network encoded, network decoding respective network encoded retransmission packets according to the determining.

10. The method of claim 8, wherein only retransmission packets in the current batch have respective NCI.

11. The method of claim 10, wherein a NCI for each packet in turn does not have, one bit mapped to the packet which is mapped by the first bit of the NCI for one packet directly before said each packet, and bits before said one bit.

12. The method of any one of claims 8 to 11, wherein a NCI for each packet does not have, bits mapped to packets that are combined in the network coding for packets before said each packet.

13. The method of any one of claims 8 to 11, further comprises receiving an indicator indicative of the number of packets in one batch prior to the new batch.

14. The method of any one of claims 8 to 11, wherein the retransmission packets are arranged to be ordered sequentially before new packets in the new batch, and

the method further comprises receiving an indicator indicative of the number of the retransmission packets in the new batch.

15. An apparatus, comprising:

a transmitter;

a receiver; and

a controller configurable with the transmitter and the receiver to

receive a request for retransmitting packets in a previous transmitted batch of packets;

in response to the request, arrange a new batch of packets including retransmission packets;

allocate a network coding indicator (NCI) consisting of bits mapped to packets in a previous transmitted batch, to indicate how the mapped packet is combined in the network coding for respective packet in the new batch; and

broadcast or multicast the new batch of packets with the NCI.

16. The apparatus of claim 15, the controller is further configured to

in response to the request, network encode the packets requested to be retransmitted for generating network encoded retransmission packets,

17. The apparatus of claim 15, wherein the controller is further configured to allocate NCI only for each of the retransmission packets.

18. The apparatus of claim 17, wherein the controller is further configured to remove in turn from a NCI for each packet, one bit mapped to the packet which is mapped by the first bit of the NCI for one packet directly before said each packet, and bits before said one bit.

19. The apparatus of any one of claims 15 to 18, wherein the controller is further configured to remove from a NCI for each packet, bits mapped to packets that are combined in the network coding for packets before said each packet.

20. The apparatus of any one of claims 15 to 18, wherein the controller is further configured to arrange the retransmission packets to be ordered sequentially before new packets in the new batch, and

inform an indicator indicative of the number of the retransmission packets in the new batch.

21. An apparatus, comprising:

a transmitter;

a receiver; and

a controller configurable with the transmitter and the receiver to

transmit a request for retransmitting packets in a previous transmitted batch of packets;

in response to the request, receive a new batch of packets including retransmission packets and network coding indicators (NCI); and

determine from the NCI consisting of bits mapped to packets in a previous transmitted batch, how the mapped packet is combined in network coding for respective packet in the new batch.

22. The apparatus of claim 21, wherein the controller is further configured to

when it is determined that respect packet in the new batch is network encoded, network decode respective network encoded retransmission packets according to the determining.

23. The apparatus of claim 21, wherein only retransmission packets in the current batch have respective NCI.

24. The apparatus of claim 22, wherein a NCI for each packet in turn does not have, one bit mapped to the packet which is mapped by the first bit of the NCI for one packet directly before said each packet, and bits before said one bit.

25. The apparatus of any one of claims 21 to 24, wherein a NCI for each packet does not have, bits mapped to packets that are combined in the network coding for packets before said each packet.

26. The apparatus of any one of claims 21 to 24, wherein the retransmission packets are arranged to be ordered sequentially before new packets in the new batch, and the controller is further configured to receive an indicator indicative of the number of the retransmission packets in the new batch.

27. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code,

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

broadcasting or multicasting the new batch of packets with the NCI.

28. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code,

in response to the request, receiving a new batch of packets including retransmission packets and network coding indicators (NCI), and

29. A computer program product comprising a computer-readable medium bearing computer program code embodied therein for use with a computer, the computer program code comprising:

code for receiving a request for retransmitting packets in a previous transmitted batch of packets; code for in response to the request, arranging a new batch of packets including retransmission packets;

code for allocating a network coding indicator (NCI) consisting of bits mapped to packets in a previous transmitted batch, to indicate how the mapped packet is combined in network coding for respective packet in the new batch; and

code for broadcasting or multicasting the new batch of packets with the NCI.

30. A computer program product comprising a computer-readable medium bearing computer program code embodied therein for use with a computer, the computer program code comprising:

code for transmitting a request for retransmitting packets in a previous transmitted batch of packets;

code for in response to the request, receiving a new batch of packets including retransmission packets and network coding indicators (NCI); and

code for determining from the NCI consisting of bits mapped to packets in a previous transmitted batch, how the mapped packet is combined in network coding for respective packet in the new batch.