Transmitter and method for transmitting data block in wireless communication system

The present invention relates to wireless communication, and more particularly to a data block transmission method in a wireless communication system and a transmitter using the data block transmission method.

Recently, various wireless communication technologies have been developed with the development of information and communication technology. Of these, WLAN (Wireless Local Area Network) is based on wireless frequency technology, such as personal digital assistants (PDAs), laptop computers, and portable multimedia players (PMPs). It is a technology that enables a wireless connection to the Internet at home, a company, or a specific service providing area by using such a portable terminal.

The Institute of Electrical and Electronics Engineering (IEEE) 802.11n is a relatively recently established technical standard to overcome the limitation on communication speed, which has been pointed out as a weakness in WLAN. IEEE802.11n aims to increase the speed and reliability of networks and extend the operating range of wireless networks. More specifically, IEEE802.11n supports high processing rates (HT) with data processing speeds up to 540 Mbps or higher, and also transmits to minimize transmission errors and optimize data speeds. It is based on MIMO (Multiple Inputs and Multiple Outputs) technology, which uses multiple antennas for both the receiver and receiver. In addition, this standard not only uses a coding method that sends multiple duplicate manuscripts to improve data reliability, but also uses OFDM (Orthogonal Frequency Division Multiplex) to increase the speed. You can also.

Generally, in wireless communication systems, codewords are interleaved over the entire frequency band in order to obtain frequency diversity gain and maximize the interleaving effect. As the size of the frequency band used increases, codewords and interleavers are increased by the size of the frequency band to obtain coding gain and diversity gain.

However, increasing the size of the interleaver by increasing the size of the frequency band increases the burden of changing the existing structure and can increase the complexity.

<p> The present invention provides a data block transmission method that supports a wide band and a transmitter using the data block transmission method in a wireless LAN system.</p>

<p> In one aspect, a data block transmission method in a wireless communication system is provided. In the above method, the number of bits (s) and the number of encoders (N) allocated to one axis of the signal constellation._ES) Is determined; the above s and N_ESTo generate a coded block by encoding information bits based on the above s and N_ESIncludes a step of parsing the coded block based on the above to generate a plurality of frequency subblocks, and a step of transmitting the plurality of frequency subblocks to a receiver.</p><p><maths num="1"><img file="JP6550366B2_D0001.tif" /></maths> And N_BPSCSIs the number of bits coded per subcarrier per spatial stream.</p><p> The step of encoding the information bit is N_ESSteps to encode the information bits using FEC (forward error correction) encoders, and the s and N_ESIncludes the step of rearranging the encoded information bits based on to generate the coded block.</p><p> The signal constellation is used for at least one of BPSK (Binary phase shift keying), QPSK (Quadrature phase shift keying), 16-QAM (Quadrature amplitude modulation), 64-QAM and 256-QAM.</p><p> The plurality of frequency subblocks correspond to a plurality of frequency bands, respectively.</p><p> Each frequency band has a bandwidth of 80 MHz.</p><p> The number of the plurality of frequency subblocks is 2.</p><p> The coded block is parsed in a round robin fashion to generate the plurality of frequency subblocks.</p><p> In another aspect, a transmitter is provided that transmits a block of data in a wireless communication system. The transmitter has the number of bits (s) and the number of encoders (N) assigned to one axis of the signal constellation._ES), And the above s and N_ESCoding unit that encodes information bits based on and generates a coded block, said s and N_ESIncludes a parsing unit that parses the coded block based on the above to generate a plurality of frequency subblocks, and a transmitter that transmits the plurality of frequency subblocks to a receiver.</p><p> In another aspect, a data block transmission method in a wireless communication system is provided. In the above method, the number of bits assigned to one axis of the signal constellation s and the number of encoders N_ESSteps to determine; steps to generate coded blocks; sN_ESIt includes a step of parsing the coded block bit by bit to generate a plurality of frequency subblocks; and a step of transmitting the plurality of frequency subblocks to a receiver;</p>

<p> Adjacent bits of the encoding block can be prevented from continuously having the same reliability in the signal constellation, and the decoding performance of the receiver can be prevented from being deteriorated.</p>

<figref num="1">It is a drawing which shows the architecture of IEEE802.11.</figref><figref num="2">It is a block diagram which shows an example of a PPDU format.</figref><figref num="3">It is a block diagram which shows an example of the transmitter which embodies the embodiment of this invention in an adjacent band.</figref><figref num="4">It is a block diagram which shows an example of the transmitter which embodies the embodiment of this invention in a non-adjacent band.</figref><figref num="5">An example of segment parsing is shown.</figref><figref num="6">An example of applying the segment parsing shown in Fig. 5 is shown.</figref><figref num="7">Another example of applying segment parsed in Figure 5 is shown.</figref><figref num="8">An example of segment parsing according to an embodiment of the present invention is shown.</figref><figref num="9">Another example of segment parsing according to one embodiment of the present invention is shown.</figref><figref num="10">The segment parsing according to one embodiment of the present invention is shown.</figref><figref num="11">Segment parsing according to another embodiment of the present invention is shown.</figref><figref num="12">The simulation result is shown.</figref><figref num="13">The simulation result is shown.</figref><figref num="14">The simulation result is shown.</figref><figref num="15">It is a flowchart which shows the data transmission method which concerns on one Example of this invention.</figref><figref num="16">It is a flowchart which shows the data transmission method which concerns on other Examples of this invention.</figref><figref num="17">It is a block diagram which shows the transmitter which embodies the Example of this invention.</figref>

The WLAN (Wireless Local Area Network) system in which the embodiment of the present invention is embodied includes at least one BSS (Basic Service Set). A BSS is a collection of stations (stations) that are successfully synchronized to communicate with each other. BSS can be classified into Independent BSS (IBSS) and Infrastructure BSS.

A BSS can include at least one STA and AP (Access Point). The STA is an AP or non-AP STA. The AP is a functional medium that provides connectivity via each Wireless Medium of the STA within the BSS. APs are sometimes referred to by other names such as centralized controller, BS (Base Station), and scheduler.

FIG. 1 is a drawing showing the architecture of IEEE 802.11.

The IEEE 802.11 PHY (wireless-medium physical layer) architecture includes PLME (PHY Layer Management Entity), PLCP (Physical Layer Convergence Procedure) sublayer 110, and PMD (Physical Medium Dependent) sublayer 100.

PLME provides PHY management functions in cooperation with MLME (MAC (Medium Access Control) Layer Management Entity).

The PLCP sub-layer 110 transmits the MPDU (MAC Protocol Data Unit) received from the MAC sub-layer 120 between the MAC sub-layer 120 and the PMD sub-layer 100 according to the instruction of the MAC layer, or transmits the MPDU (MAC Protocol Data Unit) received from the MAC sub-layer 120 to the sub-layer, or from the PMD sub-layer 100. The coming frame is transmitted to the MAC sub-layer 120.

The PMD sub-layer 100 is a PLCP sub-layer and enables transmission and reception of two STA-to-STA PHY entities (entities) via a wireless medium.

The MPDU transmitted by the MAC sub-layer 120 is called a PSDU (Physical Service Data Unit) in the PLCP sub-layer 110. MPDUs are similar to PSDUs, but when A-MPDUs (aggregated MPDUs) that aggregate multiple MPDUs are transmitted, the individual MPDUs and PSDUs are different from each other.

The PLCP sub-layer 110 adds an additional field containing information required by the physical layer transmitter / receiver in the process of receiving the PSDU from the MAC sub-layer 120 and transmitting it to the PMD sub-layer 100. At this time, the fields added are the PLCP preamble, the PLCP header, the tail bits required on the data field, and the like in the MPDU. The PLCP preamble serves to ensure that the receiver prepares the synchronization function and antenna diversity before transmitting the PSDU. The PLCP header contains a field that contains information about the frame.

In the PLCP sub-layer 110, the above-mentioned field is added to the PSDU to generate a PPDU (PLCP Protocol Data Unit), which is transmitted to the receiving station via the PMD sub-layer. The receiving station receives the PPDU , obtains the information necessary for data restoration from the PLCP preamble and PLCP header, and restores the data.

FIG. 2 is a block diagram showing an example of the PPDU format.

PPDU600 is L-STF (Legacy-Short Training Field) 610, L-LTF (Legacy-Long Training Field) 620, L-SIG (Legacy-Signal) field 630, VHT (Very High Throughput) -SIG A field 640, It can include VHT-STF650, VHT-LTF660, VHT-SIG B670, and data field 680.

The L-STF610 is used for frame timing acquisition, AGC (Automatic Gain Control), coarse frequency acquisition, and so on.

L-LTF620 is used for channel estimation for demodulation of L-SIG field 630 and VHT-SIG A field 640.

The L-SIG field 630 contains control information regarding the transmission time of the PPDU.

The VHT-SIG A field 640 contains common information that a STA that supports MIMO (multiple input multiple output) transmissions needs to receive a spatial stream. VHT-SIG A field 640 contains information for spatial streams for each STA, channel bandwidth information, group identifier, information for STAs assigned each group identifier, short GI (Guard Interval), beam formation information. Includes (including SU-MIMO or MU-MIMO).

VHT-STF650 is used to improve the performance of AGC estimation in MIMO transmission.

VHT-LTF660 is used by each STA to estimate MIMO channels.

The VHT-SIG B field 670 contains individual control information for each STA. The VHT-SIG B field 670 contains MCS (Modualtion and Coding Scheme) information. The size of the VHT-SIG B field 640 depends on the type of MIMO transmission (MU-MIMO or SU-MIMO) and the channel bandwidth used for PPDU transmission.

Data field 680 includes PSDUs, service fields, tail bits, and padding bits when needed, as transmitted from the MAC hierarchy.

To support higher data rates, WLAN systems can support a wide variety of bandwidths. For example, the supported bandwidth can include at least one of 20MHz, 40Hz, 80MHz, and 160MHz. Also, non-contiguous bandwidth can be used because continuous bandwidth is not always available. For example, using two non-adjacent 80MHz bands (denoted as 80 + 80Mhz), 160MHz bandwidth is supported.

Hereinafter, the contiguous 160 MHz band and the non-adjacent 80 + 80 MHz band will be described as examples. However, there are no restrictions on the size or number of bandwidths.

WLAN systems can support MU-MIMO and / or SU-MIMO. SU-MIMO will be described below as an example, but those skilled in the art can easily apply it to MU-MIMO.

FIG. 3 is a block diagram showing an example of a transmitter in which an embodiment of the present invention is embodied in an adjacent band.

The data unit is encoded by at least one FEC (Forward Error Coorrection) encoder (S710). The data unit contains scrambled information bits with PHY padding bits added to the PDSU. The data unit is divided into bit sequences having a specific bit size by an encoder parser, and each bit sequence can be input to each FEC encoder.

The encoding method is BCC (Binary Convolution Code). However, the posted encoding method is only an example, and those skilled in the art can apply the technical idea of the present invention to a well-known encoding method such as LDPC (low-density parity-check) and turbo code. it can.

The encoded data unit is N by the stream parser._SSRearranged in blocks of space (S720). N_SSIs the number of spatial streams.

The output bits of each stream parser are divided into two frequency subblocks (S730). One frequency subblock can accommodate 80MHz bandwidth.

Each of the two frequency subblocks is independently interleaved by the BCC interleaver (S740). The interleaver can have sizes corresponding to 20MHz, 40MHz and 80MHz. Since one frequency subblock corresponds to the 80MHz band, the frequency subblock can be interleaved by an interleaver corresponding to 80MHz.

Each interleaved frequency subblock is independently mapped onto the signal constellation by the constellation mapper (S750). The signal constellation can support various modulation methods such as BPSK (Binary Phase Shift Keying), QPSK (Quadrature phase-shift keying), 16-QAM (Quadrature amplitude modulation), 64-QAM or 256-QAM. Yes, there are no restrictions on the modulation method.

The mapped subblocks are spatially mapped using STBC (Space-time block coding) and CSD (Cyclic Shift Delay) (S760).

Two spatially mapped subblocks are sent by performing an IDFT (inverse discrete Fourier transform) (S770).

FIG. 4 is a block diagram showing an example of a transmitter in which an embodiment of the present invention is embodied in a non-adjacent band.

Compared to the transmitter in Figure 3, each of the two frequency subblocks performs IDFT independently. Each frequency subblock corresponds to the 80MHz band, and the 80MHz bandwidth is non-adjacent, so IDFT is performed independently.

The segment parser parses the encoded data unit into multiple frequency subblocks. This is to support wider bandwidth without increasing the size of the BCC interleaver.

For example, suppose an existing BCC interleaver supports up to 80MHz. To support 160MHz bandwidth, the BCC interleaver must be changed to support 160MHz. However, by utilizing a segment parser, the data stream is parsed into subblocks with the magnitude of the frequency bandwidth supported by the BCC interleaver. Therefore, it is possible to support a wider bandwidth without changing the size of the interleaver, and it is also possible to obtain a frequency diversity gain.

Hereinafter, the following parameters are defined.

N_CBPS: Number of coded bits per symbol

N_CBPSS: Number of codedbits persymbolperspatialstream per spatial stream

N_BPSC: Number of coded bits per subcarrier over all spatial streams

N_BPSCS: Number of coded bits per subcarrier per spatial stream

N_SS: Number of spatial streams

N_ES: The number of encoders for data fields, the number of encoders is the same as the number of codewords.

R: code rate

FIG. 5 shows an example of segment parsing. The existing and simplest segment parsing is to assign even bits to the first subblock and odd bits to the second subblock for each spatial stream.

FIG. 6 shows an example in which the segment parsing of FIG. 5 is applied. 64-QAM, N_ES= 4, N_SS= 6, R = 6/5, bandwidth 80MHz.

The number of bits corresponding to the Q-axis (or I-axis) of the 64-QAM signal constellation is 3. Therefore, the output of the encoder is assigned to the Round Robin method by 3 bits for each spatial stream. Each spatial stream is parsed by a stream parser to generate subblocks.

The parsed subblocks are interleaved by the interleaver. Interleaver input bits are sequentially assigned to the 26 columns, and the 3j, 3j + 1, 3j + 2 columns in the 3ith column are directly mapped to the signal constellation, and the 3j, 3j + in the 3i + 1st column. Columns 1, 3j + 2 are mapped to the signal constellation by applying a cyclic shift one step down. The 3j, 3j + 1, and 3j + 2 columns in the 3i + second column are mapped to the signal constellation by applying a cyclic shift two steps down.

It is shown that consecutive bits of a codeword are mapped to bits having different reliability on the signal constellation.

FIG. 7 shows another example in which the segment parsed in FIG. 5 is applied. 64-QAM, N_ES= 1 or 2, N_SSThis is the case when = 1, R = 6/5, and the bandwidth is 160 MHz. Unlike the example in FIG. 6, under such conditions, it is shown that consecutive bits of codeword are continuously mapped to positions with the same reliability on the signal constellation.

If the codeword bits continue to have the same reliability in the signal constellation, the decoding performance of the receiver can be significantly reduced. This is because an error can occur if the channel state drops with the reliability.

Therefore, the present invention proposes segment parsing that prevents the codeword bits from continuously having the same confidence in the signal constellation.

The proposed segment parsing takes into account the number of encoders and the number of bits allocated to one axis of the signal constellation.

Consider the number of bits s assigned to one axis of the signal constellation as follows.

<maths num="2"><img file="JP6550366B2_D0002.tif" /></maths>

For example, s = 1 for BPSK and QPSK, s = 2 for 16-QAM, s = 4 for 64-QAM, and s = 4 for 256-QAM.

FIG. 8 shows an example of segment parsing according to an embodiment of the present invention. An example of allocating two frequency subblocks in s units for each spatial stream by each modulation method is shown.

FIG. 9 shows another example of segment parsing according to an embodiment of the present invention. This is a bundle of outputs for each encoder. That is, sN for each spatial stream_ESParsing into units.

Bits of adjacent codewords can be mapped to have different confidence in the signal constellation.

The mathematical example of FIG. 9 is as follows.

Set the output bits of each spatial stream parser to N_CBPSSDivide by a block of bits. Each block is N_CBPSSIt is parsed into two frequency subblocks of / 2 bits as shown in the following formula.

<maths num="3"><img file="JP6550366B2_D0003.tif" /></maths> here,<maths num="4"><img file="JP6550366B2_D0004.tif" /></maths>Is the largest integer equal to or less than z, z mod t is the remainder of the integer z divided by the integer t, x_mIs N_CBPSSThe mth bit of the bit block, m = 0, ..., N_CBPSS-1 and l is the subblock index, l = 0,1, y_{k, l}Is the kth bit of subblock l.

On the other hand, the number of bits of the coded block (that is, the number of bits of the i-th spatial block) is 2sN._ESIf it is not a multiple of, there may be extra bits (residue bits) that are not assigned to the frequency subblock. That is, the number of bits of the coded block is 2sN._ESIf it is not divisible by, the question is how to allocate the extra bits. Typically, the 160MHz bandwidth causes problems in the following cases. (1) 64-QAM, R = 2/3, N_SS= 5, N_ES= 5 (2) 64-QAM, R = 2/3, N_SS= 7, N_ES= 7 (3) 64-QAM, R = 3/4, N_SS= 5, N_ES= 5 (4) 64-QAM, R = 3/4, N_SS= 7, N_ES=7

FIG. 10 shows segment parsing according to an embodiment of the present invention.

<maths num="5"><img file="JP6550366B2_D0005.tif" /></maths>Bits up to are parsed as in Equation 2. At this time, 2sQ (Q = (N_CBPSSmod 2sN_ES) / (2s)) Extra unparsed bits remain. Then, the extra bits are divided by the subset of s bits. Each subset is assigned to a different subblock in a round robin fashion. The first s bit is assigned to the first subblock (l = 0). That is, s bit bundles are sequentially assigned to the first subblock and the second subblock.

That is, N_CBPSSIs 2sN_ESIf not divided by, each block is N_CBPSSIt is parsed into two frequency subblocks of / 2 bits as shown in the following formula.

<maths num="6"><img file="JP6550366B2_D0006.tif" /></maths>

Equation 3 additionally indicates the allocation of extra bits to Equation 2.

FIG. 11 shows segment parsing according to another embodiment of the present invention.

<maths num="7"><img file="JP6550366B2_D0007.tif" /></maths>Bits up to are parsed as in Equation 2. Then the extra bits are divided by a 2-bit subset. Each subset is assigned to a different subblock in a round robin fashion.

12 to 14 show the simulation results. Figure 12 shows N_SS= 3, 16-QAM, R = 1/2, Figure 13 shows N_SS= 3, 16-QAM, R = 3/4, Figure 14 shows N_SS= 3, 256-QAM, R = 3/4. 'Nseg = 1'uses one interleaver over the 60MHz bandwidth without segment parsing. 'Nseg = 2, parser = 0'is the application of the existing segment parsing in Fig. 5. 'Nseg = 2, parser = 1'is an application of the proposed segment parsing in Figure 10.

The existing segment parsing increases the PER (Packet Error Rate) as compared to the case where the segment parsing is not performed, but the proposed segment parsing shows that the PER hardly increases.

FIG. 15 is a flowchart showing a data transmission method according to an embodiment of the present invention.

A coded block is generated by encoding the information bits (S910). The encoding can include spatial mapping by stream parser along with FEC encoding such as BCC or LDPC. The number of bits in the coded block (per spatial stream) is N_CBPSSIs.

The stream parser can be parsed based on s. The output bit of the FEC encoder is N_CBPSSIs rearranged into NSSS spatial blocks. A contiguous block of s bits can be assigned to other spatial streams in a round robin fashion.

Perform segment parsing in units of the first segment (S920). The first segment unit is sN_ESCan have a value of. Each encoded block is N_CBPSSIt can be parsed into M frequency subblocks of / M bits. Subblocks can accommodate bandwidths that correspond to the size of the interleaver.

When M = 2, the block encoded as in Equation 2 can be parsed and divided into two subblocks.

Determine if there are extra bits (S930).

N_CBPSSIs not divided into M × first segment units (ie, N_CBPSS(If is not a multiple of M × first segment unit), the extra bits can be parsed into M frequency subblocks in the second segment unit (S940). The first segment unit is N in the second segment unit._ESIt is a fold and the second segment unit can have a value of s. When M = 2, the block encoded as in Equation 3 can be parsed and divided into two subblocks.

Each subblock is sent to the receiver (S950). The parsed subblocks are independently interleaved by the interleaver, mapped on the signal constellation and transmitted.

FIG. 16 is a flowchart showing a data transmission method according to another embodiment of the present invention.

A coded block is generated by encoding the information bits (S1010). The encoding can include spatial mapping by stream parser along with FEC encoding such as BCC or LDPC. The number of bits in the coded block (per spatial stream) is N_CBPSSIs.

The stream parser can be parsed based on s. The output bit of the FEC encoder is N_CBPSSIs rearranged into NSSS spatial blocks. A contiguous block of s bits can be assigned to other spatial streams in a round robin fashion.

Coded block size N_CBPSSDetermines if is divided into reference values (S1020). The reference value is M × 1st segment unit.

N_CBPSSIf is divided into M × first segment units, perform segment parsing on the first segment units (S1030). The first segment unit is sN_ESCan have a value of. Each encoded block is N_CBPSSIt can be parsed into M frequency subblocks of / M bits. Subblocks can accommodate bandwidths that correspond to the size of the interleaver. When M = 2, the block encoded as in Equation 2 can be parsed and divided into two subblocks.

N_CBPSSIf is not divided into M × 1st segment units, it can be parsed into M frequency subblocks for the extra bits and for the 1st and 2nd segment units (S1040). The first segment unit is N in the second segment unit._ESIt is double. The first segment unit is sN_ESThe second segment unit can have a value of s. First, segment parse is executed in the first segment unit, and segment parse is executed in the second segment unit for the extra bits. When M = 2, the block encoded as in Equation 3 can be parsed and divided into two subblocks.

Each subblock is sent to the receiver (S1050). The parsed subblocks are independently interleaved by the interleaver, mapped on the signal constellation and transmitted.

FIG. 17 is a block diagram showing a transmitter in which an embodiment of the present invention is embodied. The embodiments of FIGS. 15 to 16 can be embodied by a transmitter.

The transmitter 1000 includes a coding unit 1010, a parsing unit 1020, and a transmitter unit 1030. The coding unit 1010 can embody the functions of the FEC encoding and the stream parser of FIGS. 3 and 4. The parsing unit 1020 can embody the functions of the segment parsers of FIGS. 3 and 4. The transmitter 1030 can embody the functions of the interleaver and constellation mapper shown in FIGS. 3 and 4.

The coding unit 1010 generates an encoded block. The parsing unit 1020 parses the encoded block into a plurality of frequency subblocks. The segment parsing of formula 2 or formula 3 can be embodied by the parsing unit 1020. The transmitter 1030 transmits the subblock to the receiver.

The coding unit 1010, the parsing unit 1020, and the transmitting unit 1030 can be embodied by one or more processors. Processors can include application-specific integrated circuits (ASICs), other chipsets, logic circuits and / or data processing devices. Memory can include ROM (read-only memory), RAM (random access memory), flash memory, memory cards, storage media and / or other storage devices. When the embodiments are embodied in software, the techniques described above can be embodied in modules (processes, functions, etc.) that perform the functions described above. Modules are stored in memory and can be executed by the processor. The memory is inside or outside the processor and can be attached to the processor by a variety of well-known means.

In the exemplary system described above, the method is described in sequence of steps or blocks based on a sequence diagram, but the invention is not limited to the sequence of steps, and some steps differ from steps different from those described above. It can occur in sequence or at the same time. Also, those skilled in the art can delete the steps shown in the sequence diagram without being exclusive, including other steps, or one or more steps in the sequence diagram without affecting the scope of the present invention. Can be understood to be.