Method and device for transmitting data according to a hybrid ARQ method

p0001The present invention relates to a method and a correspondingly configured apparatus for data transmission according to a hybrid ARQ method in a communication system, particularly a mobile radio system.

p0002Especially in connection with mobile radio systems often use so-called package access method or packet-oriented data connections proposed that the emerging types of messages often have a very high burst factor, so that only short periods of activity exist, which are interrupted by long periods of rest. Packet-oriented data connections can in this case, greatly increase the efficiency in comparison with other data transmission method in which a continuous stream of data is present, since data transmission method with a continuous data stream, a once assigned resource, such. As a carrier frequency or a time slot during the allocated entire communication relationship remains, ie a resource also remains available when currently bear no data transfers, so that this resource is not available to other network participants. This leads to a non-optimal use of the scarce frequency spectrum for mobile radio systems.

p0003Future mobile radio systems, such as according to the UMTS mobile radio standard ( "Universal Mobile Telecommunications System") are offering a variety of services, which multimedia applications are becoming increasingly important in addition to pure voice transmission. The associated services diversity with different transmission rates requires a very flexible access protocol on the air interface of future mobile radio systems. Packet-oriented data transmission methods have proved to be very useful here.

p0004In connection with UMTS mobile radio systems, a so-called ARQ ( "Automatic Repeat Request") has been proposed for packet-oriented data connections. The from a transmitter transmitted to a receiver data packets at the receiver end checks after their decoding in terms of quality. Is a received data packet in error, the receiver requests a retransmission of that data packet from the transmitter, ie it is sent, a retransmission data packet from the transmitter to the receiver, which is identical to the data packet previously transmitted and received in error or partially identical (depending on on whether the retransmission data packet is less than or equal to contain much data as the original data packet, is spoken by a full or partial repetition). With respect to the ARQ method proposed for the UMTS mobile radio standard, both the transmission of data as well as so-called header information provided in a data packet, wherein the header information also comprise information for error checking, such as CRC bits ( "Cyclic Redundancy Check"), and can also be encoded for error correction (known. FEC, Forward error correction).

p0005According to the current proposals the UMTS specification, the introduction of a so-called hybrid ARQ method is provided, which is also called a "incremental redundancy" -ARQ method. The main difference with the conventional ARQ processes described above is that in the receiver an encoding using a plurality of data packets with the same information origin, but different channel coding is performed. This means that multiple data packets are decoded with the same information origin and evaluated until an originally transmitted data packet in the receiver shall be decoded as errors. In contrast to the ARQ method described above, the retransmission data packets (also referred to as a "Retransmission") are typically not identical to the data packet originally transmitted in the hybrid ARQ method.

p0006In <figref idrefs="f0002">Fig. 3</figref> is shown, the signal processing for the discussion in accordance with the current state of UMTS standardization, hybrid ARQ process.

p0007As in <figref idrefs="f0002">Fig. 3</figref> As shown, the generation of the transmission signal in the processing of the actual data and the processing of the header information is divided. On the Header page, the header information generated by a function block 3 ( "Header Concatenation" so-called.) Is a function block 12 supplied, which ensures that all headers are summarized all data packets to be transmitted in the same radio packet to a single header , A function block 13 adds the resulting header information CRC bits added for error detection. Then, a channel coding and a function block 15, a rate matching the resulting bit stream is supplied from a function block fourteenth An interleaver 16 causes the supplied thereto symbols or bits arranged in a certain way and are spread in time. The output from the interleaver 16 data blocks are assigned to each transmission or radio frames by a function block 17 (so-called. "Radio Frame Segmentation").

p0008On the data side, a functional block 4 is provided for adding CRC bits as well. A functional block 5 is used for splitting of a channel coder 6 supplied data such that of the channel encoder 6 is a limited to a specific number of bits coding may always be carried out.

p0009Through the processing performed by the channel encoder 6 channel encoding the redundant actually data to be transmitted information is added. This has the result that a plurality of data packets sequentially transmitted comprise bits with the same information origin. In the hybrid-ARQ process (according to the so-called type II and III) is not sent when a faulty reception or an erroneous decoding of a data packet by the receiver the same data packet again from the transmitter to the receiver, but the transmitter transmits a data packet which at least partially comprises bits with the same information origin as the bits contained in the originally transmitted data packet. The recipient can through joint evaluation of all data packets which have bits with the same information origin, recover the originally transmitted information with better quality.

p0010To carry out the above-described hybrid ARQ method, it is necessary that when there is a corresponding request of the recipient of the same information originating the data transmission signals with "incremental redundancy", which enter into the originally transmitted data packet and the corresponding repeat data packets generated (so-called "Redundancy Selection"). For this purpose, a corresponding functional block 7 is provided by channel coder 6, which is controlled by the function block 3 as a controlling and after channel coding performs a corresponding Bitselektion. In this manner, by the function block 7, depending on the control, the selected bits to be sent by the functional block 3 in the first packet, and in retransmission data packets.

p0011The output from the function block 7 data is supplied to a function block 8, which by hiding or omitting individual bits (so-called. Dotting) or repeating individual bits (so-called. Repetition) adjusts the bit rate of the data stream. By a subsequent function block 9 the data stream so-called DTX bits ( "Discontinuous Transmission") can be added. Furthermore, also on the data side functional blocks 10 and 11 which have the same functions as those provided on the header page function blocks 16 and 17 perceive.

p0012Finally, the output on the data and header bits are mapped page of a function block 18 on the respective transmission or existing physical transmission channel or multiplexed (so-called. "Multiplexing").

p0013For a powerful possible hybrid or "incremental redundancy" -ARQ process the FEC coding of the different data packets repetition is possible to choose so that these data packets typically have low identity or correspondence with one another. This is especially problematic in UMTS due to the high flexibility of the performed channel coding and data adjusting for individual transmission channels, in particular since the channel coding can not be optimized solely in terms of performance. It play also other factors, such as the memory requirements and the complexity of running algorithms, an essential role, and this particularly concerns the algorithms executed on the side of the mobile station.

p0014Generally, with the reference <figref idrefs="f0002">Fig. 3</figref> explained Hybrid ARQ process the problem, an originally transmitted data packet and optionally one or more transmitted below repeating data packets to achieve the highest possible quality for encoding as cheaply as possible.

p0015From the technical specification ETSI TS 125 212 V3.5.0 (2000-12) "Multiplexing and channel coding (FDD) (3GPP TS 25.212 version 3.5.0 Release 1999) method for bit rate adjustment of generated by a Bitseparation parallel bit streams are known.

p0016From the technical specification ETSI TS 125 322 V3.5.0 (2000-12) "RLC protocol specification" (3GPP TS 25.322 version 3.5.0 Release 1999), however, is in Chapter 4.2.1 the model of so-called RLC layer (Radio Link Control layer) announced a distinction in which after an unconfirmed and an acknowledged mode.

p0017The present invention therefore has the object to propose a method and a correspondingly configured apparatus for data transmission according to a hybrid ARQ process on which the principle of a hybrid ARQ method with increased flexibility and better utilization of the potential coding gain without significant increase in complexity and memory requirements can be realized.

p0018This object is achieved by a method having the features of claim 1, and by a device according to claim 12 comprising means for carrying out the process. Dependent claims each define preferred and advantageous embodiments of the present invention.

p0019The inventive method for data transmission according to a hybrid ARQ method comprises the steps of:<ul><li>data from a transmitter in the form of data packets are transmitted to a receiver,</li><li>from the transmitter at least one repeat data packet is transmitted to the receiver after transmitting a data packet in the presence of a relevant request by the receiver, the retransmission data packet and the originally transmitted data packet bits with the same information origin have,</li><li>to select in the data packet and the repeat data packet bits to be transmitted a Bitselektion with respect to a channel-coded bit stream is carried out,</li><li>the in the data packet and the repeat data packet bits to be transmitted are subjected to bit rate matching,</li><li>the Bitselektion and the bit rate adjustment will be carried out jointly by the fact that the bits of the channel encoded bit stream is divided into at least a first bitstream and a second bit stream and the individual bit streams (AC) each having a separate bit rate adaptation undergo. Characterized by the inventive method is the following:</li><li>in the data packet and the at least one repeat data packet is a respective different bit stream transmitted in full, and</li><li>from that of the bit stream whose bits are not completely transferred to the currently transmitted data packet or retransmission data packet, a part of the bits is removed before application of the bit rate adaptation.</li></ul>

p0020A basic idea of ​​the present invention is based on the in <figref idrefs="f0002">Fig. 3</figref> shown functional blocks 7 and 8 for redundancy selection ( "Redundancy Selection") or rate matching ( "rate matching") together, so that can be done a more efficient coding. The functional blocks 7 and 8 are in the<figref idrefs="f0002">Fig. 3</figref> shown Hybrid ARQ particular structure is replaced by a structure, which performs Bitseparation for generating a plurality (coded differently) of parallel bit streams with subsequent Bitkollektion. The different bit streams are subjected to an independent rate matching. In this way, a higher flexibility is achieved in the encoding. the different parallel bitstreams can be preferably combined proportionately Pro to be transmitted data packet or retransmission data packet. This is advantageous particularly applicable Bitrepetierung.

p0021The advantage of the proposed inventive method and the corresponding device is greater flexibility and better use of possible coding gain, while in addition a less based on repetition rate matching without any appreciable increase in the complexity and the (in particular for the execution of interleaving required) storage requirements can be achieved ,

p0022In the dependent claims preferred embodiments of the present invention are described, which relate in particular to the manner of the present invention carried out Bitseparation or Bitkollektion and the choice of rate matching for each different bit streams, which result from the Bitseparation.

p0023The present invention is explained in detail with reference to the accompanying drawings with reference to preferred embodiments of a packet-oriented data transmission in a mobile radio system in which the present invention is of course not limited to cellular systems, but can be generally used in any type of communication systems, in which a hybrid ARQ method is provided for data transmission.<ul><li><figref idrefs="f0001">Fig. 1</figref> shows a diagram for illustrating the signal processing in accordance with a particular packet-based hybrid ARQ method of the present invention,</li><li><figref idrefs="f0002">FIG. 2</figref> shows a diagram for illustrating communication in a mobile radio system, and </li><li><figref idrefs="f0002">Fig. 3</figref> shows a diagram for illustrating the signal processing according to a conventional packet-based hybrid ARQ method.</li></ul>

p0024As is already previously explained, it is assumed hereinafter that with the help of the present invention, a packet-oriented data transmission in a mobile radio system, as for example schematically in <figref idrefs="f0002">FIG. 2</figref> is shown to be realized. It is in<figref idrefs="f0002">FIG. 2</figref> for example, the communication between a base station 1 and a mobile station 2 of a mobile radio system, for example a UMTS mobile radio system is illustrated. The transmission of information from the base station 1 to the mobile station 2 via the so-called "downlink" channel DL, during the transfer of the information from the mobile station 2 to the base station 1 via the so-called "uplink" channel UL is performed. The present invention is described by way of example with reference to a packet-oriented data transmission from the base station 1 to the mobile station 2, that is using a packet-oriented data transmission via the "downlink" channel, explained, and the present invention, however, in analogy to a data transfer on the "uplink" channel is applicable. Furthermore, the present invention is to analog below<figref idrefs="f0002">Fig. 3</figref> explained with reference to be carried out in the respective transmitter signal processing steps, but is to be noted that in the respective receiver for evaluation of the in this manner the transmitter side data processed an appropriate signal processing is necessary in reverse order, so that by the present invention not only the transmitter side, is concerned but also the receiver side.

p0025In <figref idrefs="f0001">Fig. 1</figref> is shown according to a hybrid ARQ method according to the invention the signal processing of the transmitted data in data packets and header information. The present invention relates generally to the processing of the data part, so that in<figref idrefs="f0001">Fig. 1</figref> Function blocks shown 12-17 which concern the header part, the in <figref idrefs="f0002">Fig. 3</figref> Function blocks 12 shown - 17 correspond. Likewise, corresponding to in<figref idrefs="f0001">Fig. 1</figref> shown functional blocks: 3 - 6 and 9-11 and 18 in the corresponding <figref idrefs="f0002">Fig. 3</figref> Functional blocks shown, so to respect the role and function of these function blocks to the above explanations <figref idrefs="f0002">Fig. 3</figref> reference may be made.

p0026As from <figref idrefs="f0001">Fig.1</figref> It can be seen that in were <figref idrefs="f0002">Fig. 3</figref> Function blocks shown 7 and 8 are replaced by a new feature section 19th This functional portion 19 includes a function block 20, wherein the 6 output from the upstream channel encoder encoded bits divided in dependence on a control by the function block 3 on at least two parallel bitstreams, which ie independently of one another, a rate matching are respectively separately subjected. In<figref idrefs="f0001">Fig. 1</figref> in this regard are three bit streams shown, wherein for each bitstream, a functional block 21 - 23 for carrying out a rate matching, that is, for puncturing or repetition of individual bits, is provided. In this way, several differently coded parallel bit streams which are fed to a further function block 24th This additional function block 24 has the task of the individual bits of the parallel bit streams in the same order, which has been used by the function block 20 for Bitseparation, ie, the allocation to the individual parallel bitstreams to pick up. In this way it is ensured that a total of the order of rate matching after the remaining bits are not changed.

p0027If per data packet selected exclusively one of a plurality of parallel bit streams, the signal processing is in accordance with <figref idrefs="f0001">Fig. 1</figref> according to the signal processing <figref idrefs="f0002">Fig. 3</figref> transferable. However, it is apparent that with the help of the in<figref idrefs="f0001">Fig. 1</figref> Signal processing shown an increased flexibility can be obtained in coding. In particular, the different parallel bitstreams may be proportionately combined per packet, this being particularly advantageously at Bitrepetierung. For example, instead of using a pure repetition coding on a single bit stream, as in the in<figref idrefs="f0002">Fig. 3</figref> Repetition coding of the case shown would be in in <figref idrefs="f0001">Fig. 1</figref> shown signal processing of the bitstream A unchanged, ie without performing a rate matching, transmitted, while the in <figref idrefs="f0001">Fig. 1</figref> Bitstream B shown can be used with a corresponding rate adjustment for filling the remaining transmission signal. In particular, the division of the bits of the channel encoded bit stream can be chosen in the individual bit streams AC such that only bits of the bit streams are 1 to N used for a data or repeat data packet number. N. This is in accordance with the<figref idrefs="f0002">Fig. 3</figref> shown prior art is not possible and only by the inventively proposed principle, as exemplified in <figref idrefs="f0001">Fig. 1</figref> is shown, realized. This variant has the advantage that the receiver for receiving the retransmission data packet number. N only memory for N blocks of bits must be reserved, as is known a priori that the receive data only from these N bit blocks originate. More generally, can also be a scheme designed in which the number of blocks of bits used for repeating data packets 1 to N monotonically increases or even strictly with N.

p0028Below, preferred embodiments of the processing performed by the function blocks 20 and 24, respectively Bitseparation Bitkollektion and for those of the functional blocks 21 - 23 performed rate adaptation are discussed.

p0029Regarding the choice of the parallel rate matching patterns which are realized by the function blocks 21 and 22 and optionally 23, can be provided to choose this in such a way that a function is executed by the overall function section 19, which is equivalent to that of the in <figref idrefs="f0002">Fig. 3</figref> shown functional blocks 7 and 8 function performed in accordance with the current state of the specification.

p0030Likewise, the data packets can with data from more than two parallel bitstreams A at repetition - are C replenished such that the bits of a bit stream or branch to 100%, ie unchanged, transmitted, while the bits of the other bit streams or branches, the remaining fill data. According to a further embodiment, the rate matching pattern can also be selected in such a way that the data packets are filled with repetition with data from precisely two parallel bitstreams, wherein said one bit stream to 100%, that is unchanged, is transferred, while the other bit stream fills the remaining data.

p0031The operation of the function blocks 20 and 24 may be chosen such that a packet to be transmitted original data is always data of the bitstream A or - data contains the bitstreams A and B - if the data of the bitstream A are transmitted already 100%. Data of the bitstream B and A used - For the first repetition packet then preferably data of the bitstream B or - if the data of the bitstream B are transferred already to 100%. For the second retransmission data packet, it is particularly advantageous for data of the bit stream C, or - if the data of the bitstream C is transmitted already 100% - data of the bitstreams B and C to be used.

p0032Generally, it is the goal of most efficient use by combining the memory in the mobile station 2 and thus prevent excessive spread data in the data packets with respect to their origin as possible. In addition to the highest possible gain can be exploited in the encoding.

p0033Subsequently, an optimal choice with respect to the memory requirements of the mobile station 2 will be explained, the embodiment described below represents a compromise between the storage requirement and the expected performance. According to this embodiment are selected to be repeated and to repeat only bits of such branches or bit streams, the data according to them by the prior art<figref idrefs="f0002">Fig. 3</figref> are already being transmitted, whereby an increased memory requirements, especially in the receiver is avoided. The original data packet contains according to this embodiment, only data of the bit stream A. The first repeat data packet contains data of the bitstream B or - if the data of the bitstream B are already transferred to 100% - data of the bitstreams B and A. To this extent, this embodiment with the above-described embodiment match. In contrast to the embodiment described above, however, the second retransmission data packet includes data of the bitstream C, or - if the data of the bitstream C are already transferred to 100% - of the bit stream data C as well as of the bit stream B and / or the bit stream A.

p0034Generally, it is favorable if after exactly one requested repetition in a similar number of bits of the bit streams A and B are transmitted. After exactly two iterations requested should be transferred in a similar number of bits of the bit streams A, B and C.

p0035Of course it is all embodiments described in the present patent application generally also be applied to more than two repetitions.

p0036According to a further variant of the present invention, a large part of the data may according to the encoding by the channel encoder 6 of those branches or bitstreams AC, the queue is not primarily for the transmission, are punctured, as in any case of these bitstreams, only a small by the subsequent rate matching share (typically z. B. 10%) of the bits to be transmitted is selected. Therefore, it is harmless if immediately 90% of the bits of these branches or bitstreams will be deleted. By this measure, less storage is accordingly in the intermediary function blocks required, so that this variant aimed primarily at further reducing memory footprint.

p0037For the latter variant is the type described below are equivalent. Instead of the selection of a particular bit stream (eg the bitstream B) followed by puncturing 90% two bit streams can also take this bit stream are introduced (eg, bit stream B 'and bitstream B "), wherein said one bit stream (B') 10% of the bits contains the original bit stream (B).

LIST OF REFERENCE NUMBERS

p0038<dl id="dl0001" compact="compact"><dt>1</dt><dd>base station</dd><dt>2</dt><dd>mobile station</dd><dt>3</dt><dd>Function block for HARQ header generation and redundancy control</dd><dt>4.13</dt><dd>Function block for adding CRC bits</dd><dt>5</dt><dd>Function block to the code block segmentation</dd><dt>6.14</dt><dd>Function block for channel coding</dd><dt>7</dt><dd>Function block for redundancy selection</dd><dt>8.15, 21-23</dt><dd>Function block for rate matching</dd><dt>9</dt><dd>Function block for adding DTX bits</dd><dt>10.16</dt><dd>Function block for interleaving</dd><dt>11.17</dt><dd>Function block for transmit frame segmentation</dd><dt>18</dt><dd>Function block for multiplexing on a broadcast channel</dd><dt>19</dt><dd>Functional section for redundancy selection and rate matching</dd><dt>20</dt><dd>Function block for Bitseparation</dd><dt>24</dt><dd>Function block for Bitkollektion</dd><dt>25</dt><dd>AC bitstream</dd><dt>26</dt><dd>DL "downlink" channel</dd><dt>UL "</dt><dd>Uplink "channel</dd></dl>