TWI784732B - Methods and apparatus for enabling data transmission using harq - Google Patents

Abstract

Methods and apparatus for enabling data transmission using HARQ in IEEE 802.11 systems are described. A method is disclosed, performed by a transmitting device, comprising computing a plurality of redundancy frames based on a plurality of data frames, transmitting the plurality of data frames to a receiving device, and transmitting a set of the plurality of redundancy frames to the receiving device determined by the transmitting device in response to receiving acknowledgement. One embodiment includes a method determining failed data frames of the plurality of data frames, requesting a set of the plurality of redundancy frames, and recovering the failed data frame using a decoder employing hard decision inputs. Other embodiments include an apparatus in a receiver device implementing the method of decoding the failed data frames using a decoder employing soft decision inputs.

Description

Method and device for enabling data transmission using HARQ

Embodiments of the invention generally relate to the field of wireless communications. More specifically, the embodiments of the present invention relate to a system and method for data transmission using Hybrid Automatic Repeat Request (HARQ) in a wireless network.

Modern electronic devices usually transmit and receive data with other electronic devices wirelessly (for example, using Wi-Fi), and data may often be lost or damaged. This could be due to interference from other electronic devices or other common problems with wireless data transmission. For these reasons, several techniques have been developed for reliable transmission so that transmissions intended for a receiver can be successfully delivered when retransmissions are required.

Two commonly used technologies for reliable data transmission are Automatic Repeat Request (ARQ) and Forward Error Coding (FEC). Automatic Repeat Request (ARQ) is a technology that requires a receiver (also referred to as a receiver, receiver) to send an acknowledgment packet (acknowledgment packet) after successfully receiving data. If the data is not successfully transmitted, no acknowledgment is sent to the sender. In this case, when the sender does not receive an acknowledgment, the material is retransmitted. However, automatic repeat request (ARQ) is relatively bandwidth inefficient, and the receiver cannot exploit the potential spectrum improvement with partially decoded data because the receiver discards any unsuccessfully received data frames. Forward Error Correction Coding (FEC) is a method of encoding raw material messages using error correcting codes technology, which includes redundant bits (parity bits). The use of Forward Error Correction Coding (FEC) increases transmission reliability because the receiver can correct a certain amount of errors without retransmitting the data.

Hybrid automatic repeat request (hybrid ARQ or HARQ) is a scheme that combines forward error-correcting coding (forward error-correcting coding) with automatic repeat request (ARQ). With HARQ, data frames that are not correctly decoded are not discarded, but are stored for later combination by the receiver with the retransmitted data frame before decoding. Under poor channel conditions, the performance of HARQ is better than that of automatic repeat request (ARQ), and when the channel condition is relatively good, due to the increase of redundancy, the performance of HARQ may be better than that of automatic repeat request (ARQ). )Difference. In practice, the two most common HARQ combining techniques are Chase Combining (CC) and Incremental Redundancy (IR). HARQ combined with CC enhances decoding by combining past and current transmissions, while Incremental Redundancy (IR) is performed by sending additional parity bits in batches in order to control the coding rate.

Currently under the IEEE 802.11ax standard, the physical (Physical, PHY) layer uses a low-density parity-check (low-density parity-check, LDPC) code for forward error correction coding (FEC), and the medium access control (Medium Access The Control, MAC) layer uses Block ACK (Block ACK, BACK) for Automatic Repeat Request (ARQ). That is to say, in 802.11, Automatic Repeat Request (ARQ) and Forward Error Correction Coding (FEC) are not combined, but used independently in different protocol layers. The introduction of HARQ under the IEEE 802.11 standard presents many challenges. For example, if HARQ is only used in the MAC protocol using MAC protocol data units (MAC protocol data units, MPDU) or aggregate MPDU (Aggregate MPDU, A-MPDU), regarding the retransmission request, each retransmission will carry a different codewords (or encoded material), because retransmitted codewords are generated by the PHY using different MPDU payloads and headers (eg, different number of delimiters, different CRC/FCS bits, and/or different MAC headers). Therefore, a receiver cannot combine current and past codewords for decoding purposes. Additionally, an MPDU or A-MPDU can span multiple complete and partial codewords (codeword). This results in a codeword mismatch that also prevents retransmitted codewords from being combined at the receiver. On the other hand, if HARQ is only used at the LDPC codeword level, then the existing 802.11 PHY layer cannot perform the detection of the wrong LDPC codeword and request retransmission, because the PHY layer defined according to the current IEEE 802.11 standard does not have the support for code-based The ability of the automatic repeat request (ARQ) mechanism of words.

Therefore, there is a need for a HARQ method and device that conforms to emerging IEEE 802.11 standards (eg, IEEE 802.11be and later versions) by adjusting existing PHY and MAC layer protocols.

Embodiments of the present invention provide an apparatus and method for performing HARQ functions according to the 802.11 standard (eg, 802.11be), including minimal changes to the PHY layer and the MAC layer. On the sender side, a forward error correction coding (FEC) frame-based (FEC Frame-based, FECF) encoder is used to generate parity (aka redundancy) frames from data frames. These parity frames are sent by the sender in response to Automatic Repeat reQuest (ARQ) requests sent by the receiver. The sender can use the parity frame to recover lost data frames using the FECF decoder. According to some embodiments, a HARQ-hard scheme using an FECF hard input decoder employed entirely on the MAC layer is described. According to other embodiments, a HARQ-soft scheme (HARQ-soft scheme) using an FECF soft input decoder (FECF soft input decoder) employed on a PHY layer is described. The sender can also compensate for packet losses in the wireless channel by opportunistically transmitting a certain number of parity frames.

According to some embodiments, the present invention provides a method of wirelessly transmitting information, which is performed by a sending device. The method includes: calculating/generating a plurality of redundant frames based on a plurality of data frames, wherein the plurality of data frames include data bits; sending the plurality of data frames to a receiving device; receiving a first acknowledgment from the receiving device , the first acknowledgment indicating that one or more of the plurality of data frames was lost at the receiving device; and, in response to receiving the first acknowledgment, sending the plurality of redundant A first set of the plurality of redundancy frames in which the sending device and the receiving device communicate according to a version of the IEEE 802.11 standard.

In some embodiments, the method further comprises: after transmitting the first set of redundant frames, receiving a second acknowledgment from the receiving device, the second acknowledgment indicating one or one of the plurality of data frames The above is lost at the receiving device; and, in response to receiving the second acknowledgment, sending a second set of the plurality of redundant frames to the receiving device, wherein the first set and the second set include the plurality of Different redundant frames in redundant frames.

In some embodiments, the method further includes: storing the plurality of redundant frames in a buffer memory (buffer memory/cache) of the sending device.

In some embodiments, a redundant frame of the plurality of redundant frames is duly sent to the receiving device before receiving the first acknowledgment.

In some embodiments, the plurality of redundant frames are used to provide information to the receiving device to reconstruct lost data frames of the plurality of data frames.

In some embodiments, each redundant frame in the plurality of redundant frames includes a corresponding header (header), and the header includes: an indication that the corresponding frame where the header is located is a redundant frame; and, for identifying The sequence number of a group of data frames to which the corresponding frame belongs.

According to some other embodiments of the present invention, there is provided a method of decoding wirelessly transmitted information, which is performed by a receiving device. The method includes: receiving a plurality of data frames including data bits from a sending device; examining the plurality of data frames to determine a failed data frame in the plurality of data frames; sending a request to the sending device to request that the sending device sending a redundant frame associated with the plurality of data frames; receiving the redundant frame from the sending device; and using a data frame of the plurality of data frames and a data frame that failed to decode the redundant frame, wherein the The sending device and receiving device communicate according to a version of the IEEE 802.11 standard.

In some embodiments, each redundant frame of the plurality of redundant frames includes a corresponding header, The header includes: an indication that the corresponding frame where the header is located is a redundant frame; and a sequence number used to identify a group of data frames to which the corresponding frame belongs.

In some embodiments, the method further includes: before sending a request to the sending device to request the sending device to send redundant frames, determining the number of successfully decoded data frames in the plurality of data frames plus the number of The number of successfully decoded redundant frames among the redundant frames is less than a predetermined value.

In some embodiments, examining the plurality of data frames to determine failed data frames of the plurality of data frames is accomplished using a decoder operative to decode a Low Density Parity Check (LDPC) code and Using soft decision input (soft decision input) and hard decision output (hard decision output).

In some embodiments, the method further includes: determining a failed data frame in the plurality of data frames; sending a request for an additional (additional, additional) redundant frame; receiving the additional redundant frame from the sending device; and Decoding the failed data frame by using the received data frame in the plurality of data frames and the received redundant frame in the plurality of redundant frames.

According to some embodiments of the present invention, there is provided receiving means (or means within a receiving device) for decoding wirelessly transmitted information from sending means. Wherein, the receiving device includes: a controller, coupled to the buffer memory and used for receiving the log-likelihood ratio (LLR) of the received data frame and the LLR of the received redundant frame and storing them in the In the buffer memory; the 802.11 decoder is used to decode the code word of the received data frame, and transmit the decoded bit of the code word to the 802.11 MAC interface, wherein the 802.11 decoder is coupled to the control The 802.11 MAC interface is coupled to the controller and the 802.11 decoder, wherein the 802.11 MAC interface is used to provide the controller with an indication of a failed data frame in the received data frame; and, redundancy A decoder, coupled to the controller and the 802.11 MAC interface, the redundant decoder is used to receive instructions from the controller to decode bits of the failed data frame using the LLR stored in the buffer memory.

In some embodiments, the receiving means is operable to identify the received data based on An indication of a failed data frame in a frame requests an additional redundant frame, and the redundant decoder is operable to utilize the LLR pair stored in the buffer memory and the LLR of the last received (last received) redundant frame The bits of the failed data frame are decoded.

In some embodiments, the 802.11 decoder and the redundant decoder reside at the physical layer of the receiving device.

In some embodiments, the controller is further operable to clear the buffer memory when the 802.11 MAC interface indicates that all bits of the failed data frame were successfully decoded.

In some embodiments, the receiving device communicates with the sending device according to a version of the IEEE 802.11 standard.

In some embodiments, the receiving device further includes: a demodulator, coupled to the controller and the 802.11 decoder, the demodulator is operable to transmit the LLR of the received frame to the controller and decode the The modulated signal is sent to the 802.11 decoder to decode the received data frame.

In some embodiments, the 802.11 MAC interface is operable to receive the decoded bits of the codeword from the 802.11 decoder, and is further operable to discard decoded bits of redundant frames, and is further operable to To store the decoded bits of the data frame.

In some embodiments, the redundancy decoder is operable to decode using the same redundancy check matrix as used by the redundancy encoder of the sending device, and further identify the matrix to the receiving device based on a MAC protocol .

In some embodiments, the redundant decoder outputs only the decoded bits of the failed data frame to the 802.11 MAC interface for identification of the failed data frame.

This summary is provided by way of example and is not intended to limit the invention. Other embodiments and advantages are described in the detailed description below. The present invention is limited by the scope of the patent application.

100: an exemplary HARQ protocol sequence

115,120,125,130: Data frame

135: block confirmation

140: Parity frame

205,210,215: MPDU

220,225:R-MPDU

300, 350, 950: Exemplary methods

305, 310, 320, 330, 315, 325: steps

360, 362, 363, 375, 370, 365: steps

405,505,410,510,415,515,420,520: curve

605,705,610,710,615,715,620,720: curve

805,810,815,820: curve

955, 960, 965, 970: steps

900: Exemplary Device

915: Shared FECF cache

905:FECF LDPC decoder

910: FECF controller

920:802.11 MAC module

925: LDPC decoder

930: demodulator

1005,1010,1015,1020,1105,1110,1120,1115: curve

1205,1210,1215,1220,1305,1310,1320,1315: curve

1405,1410,1415,1420,1505,1510,1520,1515: curve

1612: Electronic systems

1608:Communication device

1615: wireless transceiver

1609: RF front end

1610:802.11 PHY interface

1611:802.11 MAC interface

1601: Processor

1602, 1603: memory

1604: data storage device

A more complete understanding of the invention can be obtained by reading the ensuing detailed description and the examples, which are given with reference to the accompanying drawings.

FIG. 1 is a block diagram illustrating an exemplary frame exchange sequence using a novel HARQ scheme according to an embodiment of the present invention.

Figure 2 is a block diagram of an exemplary FECF encoder according to an embodiment of the present invention.

3A is a flowchart illustrating an example methodology for performing HARQ transmissions.

3B is a flowchart illustrating an example method for performing HARQ-hard decoding.

Figure 4 shows the packet error rate (Packet Error Rate, PER) as the signal-to-noise ratio (Signal-to-Noise ratio, SNR) for the HARQ hard scheme using 4-way quadrature amplitude modulation (Quadrature Amplitude Modulation, QAM) Schematic diagram of the function.

Fig. 5 shows a schematic diagram of PER as a function of SNR for a HARQ hard scheme using 16QAM.

Fig. 6 shows a schematic diagram of the average number of transmissions per data frame as a function of SNR for a HARQ hard scheme using 4QAM.

Fig. 7 shows a schematic diagram of the average number of transmissions per data frame as a function of SNR for the HARQ hard scheme using 16QAM.

Figure 8 depicts a schematic graph of throughput (megabits per second) as a function of SNR for the HARQ hard scheme.

Figure 9A shows a flowchart of an example method for decoding HARQ transmissions at a HARQ-soft receiver.

Figure 9B shows a flowchart of an example method for performing HARQ soft decoding.

Figure 10 is a graph showing bit error rate (BER) as a function of SNR for a HARQ soft scheme using a 2/3 basis code rate.

Fig. 11 is a graph of BER as a function of SNR described for a HARQ soft scheme using a 3/4 base code rate.

Figure 12 is a graph showing PER as a function of SNR for a HARQ soft scheme using a 2/3 base code rate.

Figure 13 is a graph showing PER as a function of SNR for a HARQ soft scheme using a 3/4 base code rate.

Figure 14 is a graph showing throughput (megabits per second) as a function of SNR for a HARQ soft scheme using a 2/3 base code rate.

Fig. 15 is a schematic diagram showing throughput (megabits per second) as a function of SNR for the HARQ soft scheme using 3/4 base code rate.

Figure 16 shows a block diagram of an exemplary electronic system platform upon which embodiments of the present invention may be implemented.

In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to enable those having ordinary skill in the art to better understand the embodiments of the present invention. It is evident, however, that one or more embodiments may be practiced without these specific details, that different embodiments or different features disclosed in different embodiments may be combined as desired and should not be limited to the drawings Examples cited.

The following descriptions are preferred embodiments for implementing the present invention. The following examples are only used to illustrate the technical characteristics of the present invention, and are not intended to limit the scope of the present invention. Certain terms are used throughout the specification and claims to refer to particular components. It should be understood by those skilled in the art that manufacturers may use different terms to refer to the same component. This specification and the scope of the patent application do not use the difference in name as a way to distinguish components, but the difference in function of the components as a basis for distinction. The scope of the present invention should be determined with reference to the appended claims. The terms "comprising" and "comprising" mentioned in the following description and scope of patent application are open terms, so they should be interpreted as the meaning of "including, but not limited to...". Also, the term "coupled" means an indirect or direct electrical connection. Therefore, if it is described that a device is coupled to another device, it means that the device may be directly electrically connected to the other device, or indirectly electrically connected to the other device through other devices or connection means. The term "basically" or "approximately" used herein means that within an acceptable range, a person with ordinary knowledge in the technical field can solve the technical problem to be solved and basically achieve the technical effect to be achieved. For example, "approximately equal to" means that there is a certain error from "exactly equal to" that can be accepted by those with ordinary knowledge in the technical field without affecting the correctness of the result.

Portions of the detailed description below are presented and discussed in terms of methods. Although steps and sequences thereof are disclosed in figures describing the operation of the method (eg, Figures 3A, 3B, 9A, and 9B), these steps and sequences are exemplary. Embodiments are adapted to perform various other steps or variations of the steps enumerated in the flowcharts of the figures herein, and may be performed in other orders than those depicted and described herein.

Some portions of the detailed description are presented in terms of procedures, steps, logical blocks, processing and other symbolic representations of operations on data bits that can be performed on computer memory. These descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. Here, a program, computer-implemented steps, logical blocks, procedures, etc., is generally considered to be a self-consistent sequence of steps or instructions leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated in a computer system. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.

However, it should be borne in mind that all these and similar terms are to be associated with the appropriate physical quantities are associated and are merely convenient labels applied to these quantities. Unless clearly stated otherwise from the following discussion, it should be understood that throughout the discussion terms such as "access", "configure", "coordinate", "store", "transmit", "retransmit", "authenticate" , "recognition", "request", "report", "determination", etc. refer to the actions and processes of computer systems or similar electronic computing devices, which operate and convert data expressed in physical (electronic) quantities. Convert the registers and memory of a computer system into other data, similarly expressed as physical quantities within computer system memory or registers or other such information storage, transmission or display devices.

A Novel HARQ Scheme for IEEE 802.11

Embodiments of the present invention provide apparatus and methods for performing HARQ functions according to 802.11 standards (eg, 802.11be), which include minimal changes to the PHY layer and the MAC layer. A forward error correction coding (FEC) frame-based (FEC Frame-based, FECF) encoder is used to generate a parity (also known as redundancy, redundancy) frame from a sender (sender) data frame. These parity frames are sent by the sender in response to Automatic Repeat Request (ARQ) requests sent by the receiver. According to some embodiments, the sender can use the parity frame to allow the FECF decoder to recover lost data frames. According to some embodiments, the present invention describes a HARQ hard scheme that uses a FECF hard-input decoder that is entirely employed at the MAC layer. According to other embodiments, the present invention also describes a HARQ soft scheme using a FECF soft-input decoder employed at the PHY layer. The sender can also compensate for packet loss in the wireless channel by transmitting a certain number of parity frames in a timely manner.

Fig. 1 shows an exemplary HARQ protocol sequence 100 according to an embodiment of the present invention, which includes original (original) data frames 115, 120, 125, 130, block acknowledgment (block acknowledgment, BACK) 135 and parity check frame ( parity frame) 140. In sequence 100, a parity frame (eg, parity frame 140) is generated by sender 105 from k data frames using a code generator matrix. First, the sender transmits data frames. Data frame 1 (115) is sent by sender 105 ("sender") to receiver 10 ("receiver"). As used herein, The term station (station, STA) generally refers to an electronic device capable of sending and receiving data through Wi-Fi, and the electronic device does not operate as an access point (Access Point, AP). The sender 105 and receiver 10 may comprise wireless STAs or APs. Recipient 110 successfully (without errors) receives Data Frame 1 (115) and Data Frame 2 (120). Data frame 3 (125) was not successfully received by recipient 10. After the sender 105 sends all k data frames 115, 120, 125, and 130, the receiver 10 sends a BACK indicating which data frames (eg, MPDUs) were or were not successfully received. In example 100, a BACK is sent from receiver 10 to sender 105, indicating that data frame 3 (125) was not successfully decoded.

Based on the BACK 135, the sender 105 can identify the number of failed data frames. The sender 105 may use one of any well-known predetermined algorithmic rules to determine the number of parity frames to send to the receiver 10 . In the example of FIG. 1 , the sender 105 has determined that it is sufficient to send only one parity frame 140 to the receiver 10 so that all bits in the data frame 3 can be reconstructed at the receiver side. A group of k data frames and parity frames are regarded as codewords of a linear block code by the sender (105) and the receiver (110).

In one embodiment, the FECF encoder at the sender side can use any systematic block code C ( n , k , d ), which enables the sender to construct r parities from k data frames Check frame, where C ( n , k , d ) is the standard representation of typical block coding, n is the length of the codeword, that is, the length of the FECF coding group, and k is the length of the message, that is, the number of data frames , n=k+r. Table I below shows an exemplary process for generating a codeword c from a coding matrix G _k×n with k data frames, where u _i,j and p _i,j are the i-th symbols and the i-th symbol of the j-th parity frame. The FECF symbols u _i,j and p _i,j can be defined as bits, sequences of bits, or modulated symbols.

The first k rows (first k columns) of c = ( u ₁ , .. ,u _k ,p _{k +1} , .. ,p _n ) represent the original data frame, and the remaining (nk) rows represent the parity check frame. The size of each data frame is L bits or symbols. Although the code C ( n,k,d ) can be any block code, it is desirable to choose the code C with the best or near-best fault correction capability.

Referring to FIG. 2, an exemplary series of data frames (MPDUs as shown) and parity frames (R-MPDUs as shown) are depicted in accordance with an embodiment of the present invention. Each parity MPDU has a MAC header (header, HDR) and frame checksums (frame check sums, FCS) for error detection. As shown in Figure 2, when the FECF encoder uses the C ( n , k , d ) code, r parity frames (such as R-MPDUs 220 and 225). This forms a FECF Coding Group (FECF CG) of size n frames. FECF CG is the set of coded MPDU frames belonging to the same codeword of code C ( n , k , d ). The sender is operated to store r parity frames (eg, R-MPDUs 220 and 225 ) in a buffer. The FECF encoder requires that all MSDUs be the same size (eg, L bits). For example, this can be achieved by using zero padding. The sender must include a set of predefined elements or fields in the HDR of a parity frame (such as R-MPDU) for the receiver to identify the parity frame.

The recipient can use R-MPDUs 220 and 225 to reconstruct any original material contained in MPDUs 205, 210, and 215 (and any other frames of material sent) that were not successfully decoded. For example, in Figure 2, if MPDU-2 is not successfully decoded at the receiver, the R-MPDU parity frame can be used to reconstruct the payload bits of MPDU-2, i.e., the 2nd The figure shows MSDU U ₂ . According to some embodiments, the MPDU and R-MPDU used to generate the same codeword are identified by the receiver using the FECF CG number (number) and frame sequence number (FSN) carried in the HDR. Both the FECF CG number and the FSN are parsed in the HDR by the sender according to predetermined rules.

FIG. 3A is a flowchart depicting an example method 300 for performing FECF-based HARQ encoding at a transmitting device (transmitter). When the HARQ encoder uses C ( n , k , d ) codes, the sender can only send at most r parity frames belonging to the same FECF CG.

Specifically, at step 305, the sender sends k data frames (for example, k MPDU frames).

At step 310 , the sender may also timely/opportunistically send α parity frames after step 305 . For example, the sender can use a bit error rate estimate P _B and some additional function f(.) to determine how many parity frames to send to compensate for channel loss and reconstruct lost frame. The bit error rate estimate PB can be determined, for example, by calculating the average number of errors in the channel from previously received acknowledgment messages (eg, _BACKs ), or using other well-known error estimation methods. Sending parity in a timely manner is a way to predict errors in the channel so that receivers employing simpler HARQ (such as HARQ hard schemes) can manage redundancy and throughput.

At step 315, the bit error rate estimate P _B is updated based on the most recently received BACK.

At step 320, the sender determines whether all transmitted data frames have been successfully received according to the BACK received from the receiver. At step 330, if all data frames have been successfully transmitted at step 320 or if the sender has sent all r parity frames at step 325, the sender flushes the buffer storing the transmitted frames. If it is determined that some data frames are lost (in step 320), or if the number of transmitted parity frames belonging to the same FEC CG is less than r (in step 325), then at step 315 the sender may _The received BACK updates PB and a new partial parity frame can be sent (in step 310). At step 330, the method 300 ends and any buffers used to store material and parity frames may be flushed.

It should be understood that for decoding, as described above with respect to Fig. 2, the FECF decoder may use only those parity frames belonging to the same set of encoded data and the same codeword of the code C(n,k,d). Figure 3B is an example of a method 350 for performing HARQ hard decoding depicted according to an embodiment of the present invention flow chart of the steps.

At step 360, the receiving device examines the received frames (eg, performs an FCS check on the received frames) to determine any failed/unsuccessful frames. When the receiving device (receiver/receiver) is operated to implement the HARQ hard scheme, a FECF decoder operating on hard decision inputs is employed on the MAC layer. The receiver can use FCS checks to locate failed frames (also called error frames). When the location of the erroneous frame is known in the FECF CG, the FECF decoder can exploit the erasure capabilities of the code. Step 362 determines whether at least k frames were successfully decoded/received to enable the FECF decoder to recover any failed data frames in the FECF CG of size n frames. Step 363 determines whether the MAC has reached the limit of retry requests. If at step 363 it is determined that the retry limit has been exceeded, then method 350 ends.

At step 365, if it is determined in step 363 that the retry limit has not been exceeded, the receiving device sends a request to the sending device to send redundancy frames associated with the plurality of data frames.

At step 370, the receiving device receives the redundant frame from the sending device. The method 350 proceeds to step 360 using the redundant frame received at step 370 . According to some embodiments, the redundant frames include an indication of whether each redundant frame is a redundant frame and a sequence number for identifying a group of data frames to which each redundant frame belongs.

If at step 362 it is determined that at least k frames were successfully received, then at step 375 any failed data frames are decoded using the received data frames and redundant frames. For example, assuming k=5, r=2, n=7, when k frames (for example, 3 data frames and 2 parity frames) are successfully received, the failed 2 frames can be recovered according to the received frames. data frames. After successfully decoding all data frames, any padded zeros are removed from the MPDU. The actual size of the frame can be tracked from the frame's delimiter field. After step 375, method 350 ends.

According to some embodiments, the system model with the HARQ hard scheme uses the following parameters: n=64, L=500 bytes (byte), and, α= n (1-(1- P _B ) ^L ), wherein, P _B Represents an estimate of the bit error rate. The k data frames are encoded using a Reed-Solomon code that can correct up to r erasures. The number α of parity frames is chosen to minimize the packet error rate by compensating for independent frame loss. Redundant bits are added by adding r parity frames, which have a code rate of k/n. The channel is modeled as a fast-changing Rayleigh fading channel (Rayleigh fading channel) at 20MHz, which has 2 modulation coding schemes (Modulation Coding Schemes, MCS), 4QAM with rate R ₁ =16mbps and 4QAM with rate R ₂ =33mbps 16QAM.

Figures 4 and 5 show PER and SNR for HARQ hard schemes using 4QAM and 16QAM, respectively. Understandably, for both cases using 4QAM and 16QAM, using the HARQ hard scheme significantly improves the average PER over the entire transmission power range. Specifically, as shown in Figure 4, for 16QAM, the realized coding gain can reach 14dB, and for 4QAM it can reach 4dB. In Figures 4 and 5, curves 405 and 505 represent theoretical non-HARQ, curves 410 and 510 represent simulated non-HARQ, curves 415 and 515 represent theoretical HARQ hard schemes, and curves 420 and 520 represent simulated HARQ hard scheme.

Figures 6 and 7 plot the average number of transmissions per data frame at different SNRs for HARQ hard schemes using 4QAM and 16QAM, respectively. It is worth noting that the HARQ hard scheme advantageously reduces the PER, resulting in fewer retransmissions. Therefore, this improves end-to-end latency (latency). In Figures 6 and 7, curves 605 and 705 represent theoretical non-HARQ, curves 610 and 710 represent simulated non-HARQ, curves 615 and 715 represent theoretical HARQ hard schemes, and curves 620 and 720 represent simulated HARQ hard scheme.

Figure 8 shows throughput versus SNR in megabits per second (Mbps) for the HARQ hard scheme. When rate adaptation (Rate Adaptation, RA) is not enabled, the HARQ hard scheme alone is a relatively mediocre scheme for improving throughput. However, executing with RA enabled HARQ hard schemes can advantageously provide gain in systems with QoS requirements to meet a certain target PER (eg, video or audio applications). If the system cannot meet the target PER even for the lowest available MCS, it is reasonable to consider the throughput to be zero, in which case the QoS service is interrupted. It can be appreciated that in low to medium SNR regimes, throughput can be significantly improved in systems with HARQ hard schemes.

In Figure 8, curve 805 represents non-HARQ with 16QAM, curve 810 represents the HARQ hard scheme enabled in conjunction with RA to achieve the 15% target, curve 815 represents the HARQ hard scheme with 16QAM, and curve 820 represents non-HARQ with 4QAM , curve 825 represents the HARQ hard scheme with 4QAM, and curve 830 represents the baseline situation of the non-HARQ scheme with RA and 15% target PER.

FIG. 9A depicts a block diagram of an example apparatus 900 including PHY (Physical Layer)-MAC protocol interaction for performing a HARQ soft scheme. The HARQ soft scheme is based on using an additional LDPC decoder (also called a redundant decoder, labeled FECF LDPC decoder 905 in Figure 9A). The FECF LDPC decoder is essentially a conventional LDPC decoder (or soft input decoder) with soft input, which is used on the 802.11 PHY layer. The MAC layer and the PHY layer cooperate to decode transmissions, detect errors, control decoding and request retransmission of data, etc. The FECF LDPC decoder 905 uses the log-likelihood ratio (log-likelihood ratio, LLR) of the bits stored in the FECF cache (cache) 915 (also called a buffer memory, which is coupled to the FECF controller 910) as an input . The controller 910 stores accumulated LLRs of bits obtained after demodulating the data frame or the parity frame.

When the original data frame is successfully received, the FECF controller 910 clears the FECF buffer 915 . Otherwise, the sender stores all LLRs for all bits in the FECF cache 915 . The 802.11 MAC module 920 (labeled "802.11 MAC" in the figure) determines whether a frame was successfully received, and the LLRs for the parity frame and the data frame are used by the FECF LDPC decoder 905 to recover any failed data The bits of the frame. The input L ( C _i,j ) and the decision output Q ( C _i,j ) of the FECF LDPC decoder 905 represent the i-th bit in the j-th frame. The output bit sequence Q ( C _i,j ) is passed to the 802.11 MAC module 920 (also referred to as 802.11 MAC layer for short). The input to FECF LDPC decoder 905 is controlled by FECF controller 910 . In Figure 9A, LDPC decoder 925 is a conventional LDPC decoder used in the 802.11 PHY standard, which receives input directly from demodulator (demodulator) 930 and delivers the decoded bits of the data frame to 802.11 MAC module 920 for FCS error checking. Parity frames after the demodulator 930 do not need to go through the FCS since their LLRs can be directly used by the FECF LDPC decoder 905 . Although the implementation complexity of the HARQ soft scheme is higher than that of the HARQ hard scheme, the introduction of the FECF LDPC decoder 905 can significantly improve the throughput because its decoding is performed using LLRs of data bits and parity bits .

FIG. 9B is a flowchart depicting an exemplary method 950 for performing a decoding process using a HARQ soft scheme, according to an embodiment of the present invention. The method can be performed according to the block diagram depicted in Fig. 9B as follows.

At step 955, the modulated signal is received at a demodulator, such as demodulator 930 shown in FIG. 9A. After demodulation, a soft decision input (soft decision input, e.g., LLRs of received bits) is passed to an LDPC decoder (LDPC decoder 925 as shown in FIG. 9A ) and FECF controller (as shown in FIG. 9A FECF controller 910 shown in the figure). That is, the demodulator outputs LLRs.

At step 960, the LDPC decoder decodes the LDPC codewords of the data frame and the parity frame, and the decoded bits are passed to the 802.11 MAC layer (i.e. the 802.11 MAC mode described in the embodiment of Fig. 9A Group). After the FCS check, the MAC discards correctly decoded parity frames and stores correctly received data frames.

At step 965, the LLRs of the received data bits and parity bits are provided to the FECF controller, and these LLRs are stored in the shared FECF buffer.

At step 970, the FECF LDPC decoder decodes the FECF encoded codeword. All LLRs for data bits and parity bits must belong to the same FECF CG. The FECF decoder regards the LLRs of data bits and parity bits stored in the FECF buffer as well as the LLRs of newly received parity bits as LDPC codewords. Receiving a new parity frame adds more non-zero LLRs, which increases the probability of successful decoding. Both the FECF decoder and the FECF controller are managed by the 802.11 MAC module. Note that the FECF decoder uses code puncturing for all LLRs in codewords corresponding to parity frames that have not been transmitted, e.g., for all j parity frames that have not been requested, L ( C _{i, j} )=0. Code shortening is not recommended for HARQ soft schemes due to its poor properties, eg, L ( C _i,j )>>0.

According to some embodiments, the system model with the HARQ soft scheme uses the following exemplary parameters: LDPC codes with a block length of 64,800 bits and base code rates (also called mother code rates) of 2/3 and 3/4, MPDU and The R-MPDU frame is 500 bytes, and the FECF CG length is n=648 frames, where k=432 and k=486 data frames are used for 2/3 and 3/4 code rates respectively. The FECF-encoded symbols (eg, u ( i , j ) and p ( i , j ) defined above) are 100 bits long. The channel uses an additional Gaussian white noise model (additive white Gaussian noise model, AGWN), the bandwidth is 20MHz, the constellation size (constellation size) is 4QAM, and the PHY rate is 33Mbps. The first transmission carries k data frames, and subsequent transmissions carry parity frames. The receiver allows up to 3 requests for parity frames to correct failed data frames in the FECF CG. The number of parity frames per retry is a fixed value of (nk)/3 frames. By transmitting a limited number of parities, the code can be effectively punctured for higher bit rates. At the input of the FECF LDPC decoder 905, the LLRs of the missing bits are set to zero, eg, L ( C _i,j )=0 for the i-th bit in the j-th frame that has not yet been transmitted.

Fig. 10 depicts a schematic diagram of BER versus SNR using 2/3 base code rate for the HARQ soft scheme. Figure 11 depicts the BER and SNR values for the HARQ soft scheme using 3/4 of the base code rate. The HARQ soft scheme can significantly improve BER in medium to high SNR state. When all parity frames are transmitted (in this example, after 3 retries), the HARQ soft scheme can provide reliable transmission with near zero BER. In Figures 10 and 11, curves 1005 and 1105 Shows the baseline results of BER obtained when HARQ is not enabled, curves 1010 and 1110 show the BER results obtained after transmitting 1/3 of the parity frames, and curves 1015 and 1115 are after the sender sends 2/ BER results when all parity frames are sent, curves 1020 and 1120 represent the BER results when all parity frames are sent. As shown in Figures 10 and 11, a lower 2/3 code rate provides better performance than a higher 3/4 code rate due to the larger number of parity frames when retrying.

Figure 12 depicts a schematic diagram of PER and SNR using a 2/3 base code rate, and Figure 13 depicts a schematic diagram of PER and SNR using a 3/4 base code rate. When all parity frames have been transmitted, the HARQ soft scheme is expected to provide near-reliable data packet transmission. Curves 1205 and 1305 are the baseline results when the HARQ soft scheme is not enabled, curves 1210 and 1310 represent the results after transmitting 1/3 of the parity frames, and curves 1215 and 1315 represent the results after transmitting 2/3 of the parity frames , and curves 1220 and 1320 represent the results obtained after all parity frames have been transmitted.

FIG. 14 depicts a schematic diagram of throughput (Mbps) and SNR using 2/3 base code rate, and FIG. 15 depicts a schematic diagram of throughput (Mbps) and SNR using 3/4 base code rate. At medium and low SNR values, the HARQ soft scheme is significantly better than the non-HARQ baseline scheme. In the high SNR state, no error correction is required, since the added redundant frames are essentially a data rate penalty, since the BER is very low. In addition, in addition to the throughput gain, the HARQ soft solution can also extend the transmission range to 5dB for 2/3 of the basic code rate. Throughput gains can be as high as 100%, despite the rate loss due to increased redundant frames. In Figures 14 and 15, curves 1405 and 1505 represent the throughput results when the HARQ soft scheme is not enabled, curves 1410 and 1510 represent the results after transmitting 1/3 of the parity frames, and curves 1415 and 1515 represent the results in The results obtained after transmitting 2/3 of the parity frames, curves 1420 and 1520 represent the results after all the parity frames have been transmitted.

Exemplary electronic system

Embodiments of the present invention relate to electronic systems having wireless capabilities operable to transmit and/or receive data according to the IEEE 802.11 standard (also known as Wi-Fi). Figure 16 depicts an exemplary An electronic system 1612, which may serve as a platform for implementing embodiments of the present invention. For example, system 1612 may be an embedded wireless device, STA or AP.

Fig. 16 shows electronic system 1612, which includes communication device 1608, central processing unit/processor 1601, memory (memory) 1602 (such as non-volatile ROM) and 1603 (such as volatile RAM), Data storage device 1604 and other peripheral devices such as removable disk drives, flash memory and/or optical storage devices.

Wireless transceiver 1615 of communication device 1608 enables system 1612 to communicate wirelessly with other 802.11 capable devices, either directly or over a network. Generally, the transceiver 1615 is composed of three main functional blocks: RF front end (RF front end) 1609, PHY baseband (PHY baseband) module 1610 (or called 802.11 PHY interface) and 802.11 MAC 1611 (or called 802.11 MAC interface ). At MAC 1611 and baseband PHY 1610, embodiments of the present invention will be employed in communication device 1608. Specifically, the functionality of the HARQ hard scheme is fully implemented in the MAC 1611 without changing any hardware blocks using the existing system-on-chip 802.11 MAC architecture. The HARQ hard scheme can be implemented in software, usually in the form of microcode (microcode), which runs on a microcontroller or an embedded CPU. Some functions can be implemented in hardware to speed up calculations.

According to an embodiment related to the HARQ soft scheme, the 802.11 PHY 1610 of the wireless transceiver 1615 includes a FECF LDPC decoder, a shared buffer, a FECF controller, a forward error correction coding (FEC) controller, and a conventional (conventional) The interface between LDPC decoders, and any other relevant interfaces for synchronization and clocking. Compared to the HARQ hard scheme, the HARQ soft scheme requires some minor changes in both the baseband PHY 1610 and the MAC 1611 . According to some embodiments, with the HARQ soft scheme or the HARQ hard scheme enabled, the communication device 1608 utilizes previously stored material and parity frames to decode missing data frames by combining current and future parity frames. A HARQ encoder is also implemented on the sender side. For example, using an additional protocol exchange with the receiver, the sender can generate parity frames using an FEFC encoder implemented in hardware or software. should be Solution, for the HARQ soft scheme or the HARQ hard scheme, there is no difference in the behavior of the FECF encoder at the sender side.

Some embodiments may be described in the general context of executable instructions, such as program modules, executed by one or more microcontrollers or embedded CPUs. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Generally, the functionality of the program modules may be combined or distributed as desired in various embodiments.

The use of ordinal terms such as "first", "second", "third", etc. in a claim to modify a claimed element does not in itself indicate any priority of one claimed element over another claimed element , priority or order, or chronological order in which method actions are performed, but are used only as markers to use ordinal numbers to distinguish one patentable element having the same name from another element element having the same name.

Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made to the present invention without departing from the spirit of the present invention and within the scope defined by the patent scope of the application, for example, New embodiments can be obtained by combining parts of different embodiments. The described embodiments are in all respects for the purpose of illustration only and are not intended to limit the invention. The scope of protection of the present invention should be defined by the scope of the appended patent application. Those skilled in the art can make some changes and modifications without departing from the spirit and scope of the present invention.

900: Exemplary Device

915: Shared FECF cache

905:FECF LDPC decoder

910: FECF controller

920:802.11 MAC module

925: LDPC decoder

930: demodulator

Claims (10)

A method for wirelessly transmitting information, which is performed by a sending device, the method comprising: constructing r redundant frames from k data frames, wherein the k data frames include data bits but not parity bits, The r redundant frames include parity bits, the k data frames and the r redundant frames correspond to the same group of codewords, wherein the length of each codeword is n, n=k+r, and, Each data frame and each redundant frame is an MPDU frame; sending the k data frames to a receiving device; receiving a first acknowledgment from the receiving device, the first acknowledgment indicating one or one of the k data frames The above is lost at the receiving device; and, in response to receiving the first acknowledgment, sending a set of redundant frames to the receiving device, wherein the set of redundant frames is one or more of the r redundant frames One, the sending device and the receiving device communicate according to a version of the IEEE 802.11 standard. The method according to claim 1, wherein the method further comprises: after sending the set of redundant frames, receiving a second confirmation from the receiving device, the second confirmation indicating one or more of the k data frames Lost at the receiving device; and, in response to receiving the second acknowledgment, sending another set of redundant frames to the receiving device, wherein the another set of redundant frames is one of the r redundant frames or A plurality of, and, the set of redundant frames and the another set of redundant frames include different redundant frames among the r redundant frames. The method according to claim 2, further comprising: storing the r redundant frames in a buffer memory of the sending device. The method of claim 1, wherein at least one redundant frame among the r redundant frames is timely sent to the receiving device before receiving the first acknowledgment. The method of claim 1, wherein the set of redundant frames is used to provide information to the receiving device to reconstruct a lost data frame among the k data frames. The method according to claim 1, wherein each redundant frame in the r redundant frames includes a corresponding header, and the header includes: an indication that the corresponding frame where the header is located is a redundant frame; and, for identifying The sequence number of the group of data frames to which the corresponding frame belongs. A method of decoding wirelessly transmitted information, performed by a receiving device, the method comprising: receiving k data frames comprising data bits from a transmitting device, wherein the k data frames do not include parity bits, and, Each data frame is an MPDU frame; use the FCS in each MPDU frame to check the k data frames to determine whether there is a failed data frame in the k data frames; if there is a failed data frame, send it to the sending device The first request is to request the sending device to send a redundant frame; receive a group of redundant frames from the sending device, wherein the group of redundant frames and the k data frames correspond to the same group of codewords; and, use the received The data frame and the received data frame of which the redundant frame fails to be decoded, wherein the sending device and the receiving device communicate according to the version of the IEEE 802.11 standard. The method of claim 7, wherein each redundant frame in the set of redundant frames includes a corresponding header, and the header includes: an indication that the corresponding frame in which the header is located is a redundant frame; and, for identifying The sequence number of the group of data frames to which the corresponding frame belongs. The method of claim 7, wherein examining the k data frames to determine a failed one of the k data frames is accomplished using a decoder operative to decode a low density parity check (LDPC ) code and adopt soft decision input and hard decision output. The method of claim item 7, wherein the method further includes: Determining that there are still failed data frames in the k data frames; sending a second request to request the sending device to send redundant frames; receiving another group of redundant frames from the sending device, wherein the another group of redundant frames The same group of codewords corresponds to the group of redundant frames and the k data frames; and, using the received data frames and the received redundant frames to decode the failed data frames.

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