CN105721115A

CN105721115A - Automatic repeat request method needing no error check code

Info

Publication number: CN105721115A
Application number: CN201610264870.9A
Authority: CN
Inventors: 吴茗蔚; 甘培润; 宋天宇
Original assignee: Zhejiang Lover Health Science and Technology Development Co Ltd
Current assignee: Zhejiang Lover Health Science and Technology Development Co Ltd
Priority date: 2016-04-26
Filing date: 2016-04-26
Publication date: 2016-06-29
Anticipated expiration: 2036-04-26
Also published as: CN105721115B

Abstract

本发明公开了一种无需差错校验码的自动重传请求方法，包括以下步骤：该方法先在接收端设定最佳信道系数门限，该门限可最小化平均接收误比特率；然后接收端进行信道估计；当信道系数幅度小于门限时，接收端向发送端发出仅一比特的否定应答(NAK)；否则接收端则不反馈表示肯定；发送端根据应答，发送下一帧或进行重传。本发明发送端无需差错校验码、无需信道信息；接收端信道系数门限可灵活调整，ACK/NAK反馈仅需一比特。本发明性能优于传统ARQ、分集接收和具有理想信道信息的发送功率控制，其分集增益随有效信噪比线性增大。The invention discloses an automatic retransmission request method without an error check code, comprising the following steps: the method first sets the optimal channel coefficient threshold at the receiving end, and the threshold can minimize the average received bit error rate; and then the receiving end Perform channel estimation; when the channel coefficient amplitude is less than the threshold, the receiving end sends a negative acknowledgment (NAK) of only one bit to the sending end; otherwise, the receiving end does not feedback to indicate positive; the sending end sends the next frame or retransmits according to the response . In the present invention, the sending end does not need error check codes and channel information; the receiving end channel coefficient threshold can be adjusted flexibly, and only one bit is needed for ACK/NAK feedback. The performance of the invention is superior to traditional ARQ, diversity reception and transmission power control with ideal channel information, and its diversity gain linearly increases with effective signal-to-noise ratio.

Description

A method of automatic retransmission request without error check code

技术领域technical field

本发明涉及一种无需差错校验码的自动重传请求方法，基于有效信噪比对门限进行了优化，适用于无线通信技术领域。The invention relates to an automatic retransmission request method without an error check code, optimizes the threshold based on the effective signal-to-noise ratio, and is suitable for the technical field of wireless communication.

背景技术Background technique

广泛应用于数据通信的两种差错控制策略是前向差错控制FEC和自动重传请求ARQ。ARQ通过差错校验和数据重传实现通信系统可靠性的提高。现代通信标准中ARQ常用的差错校验码是循环冗余校验码，如以太网、无线局域网、LTE(长期演进)。ARQ原为时不变的加性高斯白噪声信道AWGN设计的，也能直接应用于无线衰落信道。Two error control strategies widely used in data communication are Forward Error Control (FEC) and Automatic Repeat Request (ARQ). ARQ improves the reliability of the communication system through error checking and data retransmission. The error checking code commonly used in ARQ in modern communication standards is cyclic redundancy checking code, such as Ethernet, wireless local area network, LTE (Long Term Evolution). ARQ was originally designed for the time-invariant additive Gaussian white noise channel AWGN, and can also be directly applied to wireless fading channels.

ARQ对可靠性的提高依赖于对检出差错帧的重传。众所周知，重传会降低系统的吞吐量。而往往被忽视的是，重传也提高了成功接收帧所需的总发送能量。常用的可靠性指标平均接收误比特率、以及有效性指标吞吐量的分析，都是基于传统信噪比。信噪比的定义为符号能量和AWGN功率谱密度的比值，即The improvement of ARQ reliability depends on the retransmission of detected error frames. It is well known that retransmissions reduce the throughput of the system. What is often overlooked is that retransmissions also increase the total transmit energy required to successfully receive a frame. The analysis of the commonly used reliability index average received bit error rate and effectiveness index throughput is based on the traditional signal-to-noise ratio. The signal-to-noise ratio is defined as the ratio of the symbol energy to the AWGN power spectral density, that is,

${γ γ}_{T T} = = \frac{22 {σ σ}^{22} {E E.}_{b b,, T T}}{{N N}_{00}}$

其中E_b,T是每比特发送能量，并不计入重传所需的能量。而有效接收每比特所需的发送能量实为E_b＝E[L]E_b,T，其中E[L]是平均传输次数。因此，有效信噪比应定义为Among them, E _b,T is the transmitted energy per bit, and does not include the energy required for retransmission. The transmission energy required to receive each bit effectively is actually E _b =E[L]E _b,T , where E[L] is the average number of transmissions. Therefore, the effective SNR should be defined as

$γ γ = = \frac{22 {σ σ}^{22} {E E.}_{b b}}{{N N}_{00}}$

如图1所示在AWGN信道下，由于中低信噪比时使用CRC的传统ARQ的平均传输次数较高，因此基于有效信噪比的平均接收误比特率性能实际并没有文献中显示的基于传统信噪比的性能那么好。实际上，ARQ的平均接收误比特率在中低信噪比时比无差错校验的系统差很多，而且不随有效信噪比的增大而单调递减。As shown in Figure 1, under the AWGN channel, because the average number of transmissions of traditional ARQ using CRC is relatively high at medium and low SNRs, the average received bit error rate performance based on the effective SNR is actually not as good as that shown in the literature based on The traditional SNR performance is so good. In fact, the average receiving bit error rate of ARQ is much worse than that of the system without error checking at medium and low SNR, and it does not decrease monotonously with the increase of effective SNR.

无线通信中，信号除了受AWGN噪声影响外，还经历时变的乘性复信道系数。对应每个信道系数的信道等价于不同信噪比的AWGN信道。ARQ直接应用于无线衰落信道，在深衰落下的性能显然较差。无论平均信噪比的取值大小，在瞬时信噪比较小时，ARQ瞬时性能较差。衰落信道的平均性能等价于其在不同信噪比AWGN信道的性能平均。因此ARQ在低平均信噪比的平均性能也较差。对应用CRC和汉明码的ARQ分析都显示了以上现象，具有一定的普遍性。In wireless communication, in addition to being affected by AWGN noise, the signal also experiences time-varying multiplicative complex channel coefficients. The channel corresponding to each channel coefficient is equivalent to an AWGN channel with different SNR. ARQ is directly applied to wireless fading channels, and its performance under deep fading is obviously poor. Regardless of the value of the average SNR, when the instantaneous SNR is small, the ARQ instantaneous performance is poor. The average performance of a fading channel is equivalent to the average performance of AWGN channels with different signal-to-noise ratios. Therefore the average performance of ARQ at low average SNR is also poor. The ARQ analysis of the application of CRC and Hamming codes has shown the above phenomenon, which has certain universality.

发明内容Contents of the invention

本发明的目的在于克服上述现有ARQ在无线衰落信道低平均信噪比下的问题，提出一种无需差错校验码的自动重传请求方法，通过对信道系数监测以及基于信道系数的重传请求条件，灵活的提高通信的可靠性。The purpose of the present invention is to overcome the above-mentioned existing ARQ problems under the low average signal-to-noise ratio of wireless fading channels, and propose an automatic retransmission request method without error checking codes, by monitoring channel coefficients and retransmitting based on channel coefficients Request conditions, flexibly improve communication reliability.

本发明的目的是通过以下技术方案实现的：一种无需差错校验码的自动重传请求方法，该方法包括以下步骤：The purpose of the present invention is achieved by the following technical scheme: a kind of automatic retransmission request method without error check code, the method comprises the following steps:

(1)设定接收端的信道系数门限h^TH；(1) Set the channel coefficient threshold h ^TH of the receiving end;

(2)发送端的信息经调制后，以帧为单位进行发送。(2) After the information at the sending end is modulated, it is sent in units of frames.

(3)接收端根据接收的信号估计信道系数的幅度。(3) The receiving end estimates the magnitude of the channel coefficient according to the received signal.

(4)接收端将信道系数幅度与预先设定的信道系数门限h^TH比较。当信道系数幅度小于此门限时，接收端向发送端发出1比特的否定应答(NAK)。当信道系数幅度大于或等于门限时，接收端则发出1比特的肯定应答(ACK)或以不反馈表示肯定，并对接收信号进行解调判决。(4) The receiving end compares the amplitude of the channel coefficient with the preset channel coefficient threshold ^hTH . When the channel coefficient amplitude is smaller than this threshold, the receiving end sends a 1-bit negative acknowledgment (NAK) to the sending end. When the channel coefficient amplitude is greater than or equal to the threshold, the receiving end sends a 1-bit acknowledgment (ACK) or expresses affirmation with no feedback, and demodulates and judges the received signal.

(5)发送端接收应答，根据应答发送下一帧或进行重传，具体为：若接收ACK应答或没有接收到应答，则发送下一帧；若接收到NAK应答，则进行重传。(5) The sender receives the response, and sends the next frame or retransmits according to the response, specifically: if an ACK response is received or no response is received, the next frame is sent; if a NAK response is received, retransmission is performed.

进一步地，步骤1中信道系数门限通过以下步骤设定：Further, in step 1, the channel coefficient threshold is set through the following steps:

(1.1)接收端通过信道估计获取以下参数：信道系数h，瑞利衰落信道系数的方差2σ²，AWGN双边功率谱密度N₀/2。(1.1) The receiving end obtains the following parameters through channel estimation: channel coefficient h, variance 2σ ² of Rayleigh fading channel coefficient, AWGN bilateral power spectral density N ₀ /2.

(1.2)假设接收端可实现理想信道估计，接收端收到每比特信号的瞬时误比特率可表示为：(1.2) Assuming that the receiving end can realize ideal channel estimation, the instantaneous bit error rate of each bit signal received by the receiving end can be expressed as:

$P P (({e e}_{b b} | | | | h h | |)) = = \frac{11}{22} e e r r f f c c ((\sqrt{\frac{{αE αE}_{b b,, T T} {| | h h | |}^{22}}{{N N}_{00}}})) - - c c \cdot &Center Dot; {erfc erfc}^{22} ((\sqrt{\frac{{αE αE}_{b b,, T T} {| | h h | |}^{22}}{{N N}_{00}}})) - - - - - - ((11))$

其中erfc为高斯误差函数，e_b表示比特误码事件，E_b,T为发送的每比特能量，常数α和c由调制方式决定(本领域的公知常识)。公式(1)可近似为Where erfc is a Gaussian error function, e _b represents a bit error event, E _{b, T} is the energy per bit transmitted, and the constants α and c are determined by the modulation method (common knowledge in this field). Formula (1) can be approximated as

$P P (({e e}_{b b} | | | | h h | |)) = = \frac{11}{22} e e r r f f c c ((\sqrt{\frac{{αE αE}_{b b,, T T} {| | h h | |}^{22}}{{N N}_{00}}})) - - - - - - ((22))$

使用切诺夫界，公式(1)上界为Using the Chernoff bound, the upper bound of formula (1) is

$P P (({e e}_{b b} | | | | h h | |)) \leq \leq \frac{11}{22} exp exp ((- - \frac{{αE αE}_{b b,, T T} {| | h h | |}^{22}}{{N N}_{00}})) - - - - - - ((33))$

(1.3)利用贝叶斯定理，接收端接收帧的误比特率表示为(1.3) Using Bayesian theorem, the bit error rate of the received frame at the receiving end is expressed as

$P P (({e e}_{b b} | | | | h h | | > > | | {h h}^{T T H h} | |)) = = \frac{P P (({e e}_{b b},, | | h h | | > > | | {h h}^{T T H h} | |))}{P P ((| | h h | | > > | | {h h}^{T T H h} | |))} = = \frac{{&Integral; &Integral;}_{{| | {h h}^{T T H h} | |}^{22}}^{∞ ∞} P P (({e e}_{b b} | | x x = = {| | h h | |}^{22})) {p p}_{{| | h h | |}^{22}} ((x x)) d d x x}{{&Integral; &Integral;}_{{| | {h h}^{T T H h} | |}^{22}}^{∞ ∞} {p p}_{{| | h h | |}^{22}} ((x x)) d d x x} - - - - - - ((44))$

其中，|h^TH|为接收端的门限；Among them, |h ^TH | is the threshold of the receiving end;

代入信道系数h的复高斯分布和公式(3)中的瞬时误比特率，接收误比特率为Substituting the complex Gaussian distribution of the channel coefficient h and the instantaneous bit error rate in formula (3), the received bit error rate is

$P P (({e e}_{b b} | | | | h h | | > > | | {h h}^{T T H h} | |)) < < \frac{11}{22} \frac{11}{{e e}^{- - ρ ρ} α α γ γ + + 11} exp exp ((- - {ρe ρe}^{- - ρ ρ} α α γ γ)) - - - - - - ((55))$

其中ρ＝|h^TH|²/2σ²为归一化信道系数门限，γ为考虑重传能量的有效信噪比。公式(4)可近似为Where ρ=|h ^TH | ² /2σ ² is the normalized channel coefficient threshold, and γ is the effective signal-to-noise ratio considering retransmission energy. Formula (4) can be approximated as

$P P (({e e}_{b b} | | | | h h | | > > | | {h h}^{T T H h} | |)) \approx \approx \frac{11}{22 α α γ γ} exp exp ((- - {ρe ρe}^{- - ρ ρ} α α γ γ + + ρ ρ)) - - - - - - ((66))$

(1.4)基于公式(6)求得最小化平均接收误比特率的最佳门限值为(1.4) Based on formula (6), the optimal threshold for minimizing the average received bit error rate is obtained as

$| | {h h}_{o o}^{T T H h} | | = = σ σ \sqrt{22 [[11 - - W W ((\frac{e e}{α α γ γ}))]]} - - - - - - ((77)) . .$

本发明与现有技术相比，具有以下优点：Compared with the prior art, the present invention has the following advantages:

(1)发送端的信息经调制以帧为单位发送，对该信息是否经编码不做要求。无需差错校验编码或其他差错校验方法；当设计目标和信道状况变化需进行调整时，无需改变帧长和码长，因此电路实现较为简单。(1) The information at the sending end is modulated and sent in units of frames, and it is not required whether the information is encoded or not. There is no need for error-checking coding or other error-checking methods; when the design target and channel conditions need to be adjusted, there is no need to change the frame length and code length, so the circuit implementation is relatively simple.

(2)接收端根据接收的信号估计信道系数的幅度。信道估计是相干解调的必要步骤，因此无需改动接收端原有信道估计部分。(2) The receiving end estimates the magnitude of the channel coefficient according to the received signal. Channel estimation is a necessary step for coherent demodulation, so there is no need to change the original channel estimation part at the receiving end.

(3)接收端将信道系数幅度与预先设置的信道系数门限比较，以决定ACK/NAK应答的发送和信号解调。门限可根据不同的设计目标和信道长期状况进行线下或线上实时调整，方法的实现较为灵活。(3) The receiving end compares the magnitude of the channel coefficient with the preset channel coefficient threshold to determine the transmission of the ACK/NAK response and signal demodulation. The threshold can be adjusted offline or online in real time according to different design goals and long-term channel conditions, and the implementation of the method is more flexible.

(4)发送端收到ACK/NAK应答后，可使用任何重传协议继续发送下一帧/重传，比如但不限于传统的停等式、回退N帧和选择性重传。因此适用于任何现有的发送端重传协议，不要求修改发送端。(4) After receiving the ACK/NAK response, the sender can continue to send the next frame/retransmission using any retransmission protocol, such as but not limited to traditional stop-equation, back-off N frames and selective retransmission. Therefore, it is applicable to any existing sender retransmission protocol and does not require modification of the sender.

(5)本发明的整体误码率性能随着有效信噪比的增大而单调递减，便于确定达到误码率性能要求所需的信噪比。误码率性能优于无重传系统、使用CRC的传统ARQ、发送端具有连续理想信道状态信息CSI的发送功率控制通信系统，而本发明发送端无需信道状态信息。本发明的可实现分集增益随有效信噪比线性增大，并趋向于无穷大，即大于传统单入多出SIMO系统的固定接收增益。(5) The overall bit error rate performance of the present invention monotonically decreases with the increase of the effective signal-to-noise ratio, which is convenient for determining the required signal-to-noise ratio to meet the bit error rate performance requirement. The bit error rate performance is better than that of no retransmission system, traditional ARQ using CRC, and a transmission power control communication system with continuous ideal channel state information (CSI) at the sending end, while the sending end of the present invention does not need channel state information. The achievable diversity gain of the present invention increases linearly with the effective signal-to-noise ratio and tends to infinity, that is, it is greater than the fixed receiving gain of the traditional single-input multiple-output SIMO system.

附图说明Description of drawings

图1是传统ARQ在AWGN信道下基于有效信噪比的误比特率性能。Fig. 1 shows the bit error rate performance based on the effective signal-to-noise ratio of traditional ARQ under the AWGN channel.

图2是本发明方法的系统框图。Fig. 2 is a system block diagram of the method of the present invention.

图3是本发明方法实例的误比特率性能。Figure 3 is the bit error rate performance of an example of the method of the present invention.

具体实施方式detailed description

下面结合附图对本发明的实例作详细说明。本实例在以本发明技术方案为前提下进行实施，给出了详细的实施方式和性能分析，但本发明的保护范围不限于下述的实例1。包括以下步骤：The examples of the present invention will be described in detail below in conjunction with the accompanying drawings. This example is implemented on the premise of the technical solution of the present invention, and detailed implementation and performance analysis are given, but the protection scope of the present invention is not limited to the following example 1. Include the following steps:

步骤一，接收端设定信道系数门限，当实际信道系数低过此门限时，信道被视为不可靠。Step 1: The receiving end sets a channel coefficient threshold, and when the actual channel coefficient is lower than the threshold, the channel is considered unreliable.

步骤二，发送端的信息不经信道编码，由二进制相移键控(BPSK)调制，以帧长k＝12为单位发送。In step 2, the information at the sending end is modulated by binary phase shift keying (BPSK) without channel coding, and sent in units of frame length k=12.

步骤三，信道为瑞利衰落信道。接收端可实现理想信道估计，得到准确的信道系数h。Step 3, the channel is a Rayleigh fading channel. The receiving end can realize ideal channel estimation and obtain accurate channel coefficient h.

步骤四，接收端将信道系数幅度|h|与预先设置的信道系数门限|h^TH|比较。当|h|<|h^TH|时，接收端向发送端发出1比特的否定应答(NAK)。当|h|>|h^TH|时，接收端则发出1比特的肯定应答(ACK)，并对接收信号进行BPSK解调。Step 4, the receiving end compares the channel coefficient amplitude |h| with the preset channel coefficient threshold |h ^TH |. When |h|<|h ^TH |, the receiving end sends a 1-bit negative acknowledgment (NAK) to the sending end. When |h|>|h ^TH |, the receiver sends a 1-bit positive response (ACK), and performs BPSK demodulation on the received signal.

步骤五，发送端收到ACK/NAK应答后，使用传统的停等式、回退N帧和选择性重传协议进行重传。这些重传协议的误比特率性能相同。Step 5: After receiving the ACK/NAK response, the sender uses the traditional stop-and-equal, back-off-N frame and selective retransmission protocol for retransmission. The bit error rate performance of these retransmission protocols is the same.

步骤一中设定信道系数门限的方法如下：The method for setting the channel coefficient threshold in step 1 is as follows:

步骤1.1，接收端通过信道估计获取以下参数：信道系数h，瑞利衰落信道系数的方差2σ²，AWGN双边功率谱密度N₀/2。In step 1.1, the receiving end obtains the following parameters through channel estimation: channel coefficient h, variance 2σ ² of Rayleigh fading channel coefficient, and AWGN bilateral power spectral density N ₀ /2.

步骤1.2，假设接收端可实现理想信道估计。当信道系数为h时，接收端收到每比特信号的瞬时误比特率可表示为In step 1.2, it is assumed that the receiver can achieve ideal channel estimation. When the channel coefficient is h, the instantaneous bit error rate of each bit signal received by the receiving end can be expressed as

其中erfc为高斯误差函数，e_b表示比特误码事件，E_b,T为发送的每比特能量，作为本领域的公知常识，常数α和c由调制方式决定。不同的调制方式，常数α和c值不同，(1)式可近似为Where erfc is a Gaussian error function, e _b represents a bit error event, E _{b, T} is the energy per bit transmitted, as common knowledge in the field, constants α and c are determined by the modulation method. Different modulation methods have different values of constant α and c, and formula (1) can be approximated as

使用切诺夫界，(1)式上界为Using Chernoff bound, the upper bound of (1) is

其中，BPSK调制解调最佳接收机对应的常数为α＝1。Wherein, the constant corresponding to the optimal receiver of BPSK modulation and demodulation is α=1.

步骤1.3，利用贝叶斯定理，自动重传请求方法接收端接收帧的误比特率表示为Step 1.3, using Bayesian theorem, the bit error rate of the frame received by the receiving end of the automatic retransmission request method is expressed as

代入信道系数h的复高斯分布和(3)式中的瞬时误比特率，接收误比特率为Substituting the complex Gaussian distribution of the channel coefficient h and the instantaneous bit error rate in (3), the receiving bit error rate is

$P P (({e e}_{b b} | | | | h h | | > > | | {h h}^{T T H h} | |)) < < \frac{11}{22} \frac{11}{{e e}^{- - ρ ρ} γ γ + + 11} exp exp ((- - {ρe ρe}^{- - ρ ρ} γ γ)) - - - - - - ((55))$

其中ρ＝|h^TH|²/2σ²为归一化信道系数门限，γ为考虑重传能量的有效信噪比。在中高信噪比时，式(4)可近似为Where ρ=|h ^TH | ² /2σ ² is the normalized channel coefficient threshold, and γ is the effective signal-to-noise ratio considering retransmission energy. When the signal-to-noise ratio is medium or high, formula (4) can be approximated as

$P P (({e e}_{b b} | | | | h h | | > > | | {h h}^{T T H h} | |)) \approx \approx \frac{11}{22 γ γ} exp exp ((- - {ρe ρe}^{- - ρ ρ} γ γ + + ρ ρ)) - - - - - - ((66))$

步骤1.4，基于(6)式求得最小化平均接收误比特率的最佳门限值应为Step 1.4, based on formula (6), the optimal threshold for minimizing the average received bit error rate should be

$| | {h h}_{o o}^{T T H h} | | = = σ σ \sqrt{22 [[11 - - W W ((\frac{e e}{γ γ}))]]} - - - - - - ((77))$

将门限取值分别设为最优值0.5σ和2σ，通过对瑞利衰落信道下的平均接收误比特率性能进行理论分析和数值计算，结果见图3。使用最佳门限的本发明性能优于门限值0.5σ和2σ。Set the threshold value to the optimal value respectively 0.5σ and 2σ, through the theoretical analysis and numerical calculation of the average received bit error rate performance under the Rayleigh fading channel, the results are shown in Figure 3. The present invention using the optimal threshold outperforms threshold values of 0.5σ and 2σ.

为公平比较，以下用于比较的实例与本发明使用相同的BPSK调制、理想信道估计。For fair comparison, the following examples for comparison use the same BPSK modulation and ideal channel estimation as the present invention.

用于比较的实例2：无重传系统。Example 2 for comparison: no retransmission system.

用于比较的实例3：传统ARQ发送端信息位长k＝12，经CRC-4编码添加冗余位4比特。接收端CRC校验出错反馈NAK；校验通过则反馈ACK，并对接收信号进行BPSK解调。Example 3 for comparison: the information bit length of the traditional ARQ transmitter is k=12, and 4 redundant bits are added after CRC-4 encoding. The receiving end will feed back NAK if the CRC check fails; if the check passes, it will feed back ACK, and perform BPSK demodulation on the received signal.

用于比较的实例4：单入多出(SIMO)分集接收可通过时间、频率和空间三种方式实现分集。时间分集将同一帧信息重复发送L次。频率分集将同一帧信息用L个不同频段同时发送。空间分集通过L根天线接收同一帧信息。三者都将L次接收到同一帧信息的信号进行最大比合并。在相同的总有效信噪比(分集合并后)下，时间、频率和空间能实现相同的分集增益L。Example 4 for comparison: Single-Input-Multiple-Output (SIMO) diversity reception can realize diversity in three ways: time, frequency and space. In time diversity, the same frame information is repeatedly sent L times. Frequency diversity uses L different frequency bands to send the same frame of information simultaneously. Space diversity receives the same frame of information through L antennas. All three perform maximum-ratio combination on signals that receive the same frame of information L times. Under the same total effective signal-to-noise ratio (after diversity combining), the same diversity gain L can be realized in time, frequency and space.

用于比较的实例5：发送端具有连续理想信道状态信息的发送功率控制系统。接收端将精确的信道系数h无差错无延时的反馈至发送端。发送端根据精确信道系数，以最小化误比特率的目标调整发送功率。Example 5 for comparison: a transmit power control system with continuous ideal channel state information at the transmit end. The receiving end feeds back the accurate channel coefficient h to the sending end without error or delay. The sending end adjusts the sending power with the goal of minimizing the bit error rate according to the accurate channel coefficient.

如图3所示，本发明实例的差错性能随着有效信噪比的增大而单调递减，便于确定达到平均接收误比特率性能要求所需的信噪比。本发明的差错性能优于无重传系统，也优于传统使用CRC的ARQ。本发明的可实现分集增益随有效信噪比线性增大，并趋向于无穷大，即大于实例4传统SIMO系统的固定接收分集增益。本发明的差错性能也整体优于实例5发送端具有连续理想信道状态信息的发送功率控制系统；而本发明发送端无需信道状态信息，信道状态仅以一比特的ACK/NAK反馈至发送端，反馈量小。As shown in FIG. 3 , the error performance of the example of the present invention decreases monotonously with the increase of the effective SNR, which is convenient for determining the SNR required to meet the performance requirement of the average received bit error rate. The error performance of the present invention is superior to that of a non-retransmission system and also superior to traditional ARQ using CRC. The achievable diversity gain of the present invention increases linearly with the effective signal-to-noise ratio and tends to infinity, that is, it is greater than the fixed receiving diversity gain of the traditional SIMO system in Example 4. The error performance of the present invention is also overall better than that of the transmission power control system in which the sending end of Example 5 has continuous ideal channel state information; while the sending end of the present invention does not need channel state information, and the channel state is only fed back to the sending end with a one-bit ACK/NAK, Feedback is small.

Claims

1. the automatic retransmission request method without error check code, it is characterised in that the method comprises the following steps:

(1) the channel coefficients thresholding h of receiving terminal is set^TH；

(2), after the information of transmitting terminal is modulated, it is transmitted in units of frame.

(3) receiving terminal amplitude according to the Signal estimation channel coefficients received.

(4) receiving terminal is by channel coefficients amplitude and channel coefficients thresholding h set in advance^THRelatively.When channel coefficients amplitude is less than this thresholding, receiving terminal sends the negative response of 1 bit (NAK) to transmitting terminal.When channel coefficients amplitude is more than or equal to thresholding, receiving terminal then sends the affirmative acknowledgement (ACK) of 1 bit or with not feedback representation affirmative, and is demodulated judgement to received signal.

(5) transmitting terminal receives response, sends next frame according to response or retransmits, if particularly as follows: receive ACK response or be not received by response, then sending next frame；If receiving NAK response, then retransmit.

2. according to claim 1 without error check code automatic retransmission request method, it is characterized in that, in step 1, channel coefficients thresholding is set by following steps:

(1.1) receiving terminal obtains following parameter by channel estimating: channel coefficients h, variance 2 σ of rayleigh fading channel coefficient², the bilateral power spectral density N of AWGN₀/2。

(1.2) assuming that receiving terminal can realize perfect channel estimation, receiving terminal receives the instantaneous bit error rate of every bit signal and is represented by:

P (e_{b} | | h |) = \frac{1}{2} e r f c (\sqrt{\frac{{αE}_{b, T} {| h |}^{2}}{N_{0}}}) - c \cdot {erfc}^{2} (\sqrt{\frac{{αE}_{b, T} {| h |}^{2}}{N_{0}}}) - - - (1)

Wherein erfc is Gauss error function, e_bRepresent bit error code event, E_b,T(the known general knowledge of this area) is determined by modulation system for the energy per bit sent, constant α and c.Formula (1) can be approximately

P (e_{b} | | h |) = \frac{1}{2} e r f c (\sqrt{\frac{{αE}_{b, T} {| h |}^{2}}{N_{0}}}) - - - (2)

Using Qie Nuofu circle, formula (1) upper bound is

P (e_{b} | | h |) \leq \frac{1}{2} \exp (- \frac{{αE}_{b, T} {| h |}^{2}}{N_{0}}) - - - (3)

(1.3) utilizing Bayes theorem, receiving terminal receives the bit error rate of frame and is expressed as

P (e_{b} | | h | > | h^{T H} |) = \frac{P (e_{b}, | h | > | h^{T H} |)}{P (| h | > | h^{T H} |)} = \frac{{&Integral;}_{{| h^{T H} |}^{2}}^{\infty} P (e_{b} | x = {| h |}^{2}) p_{{| h |}^{2}} (x) d x}{{&Integral;}_{{| h^{T H} |}^{2}}^{\infty} p_{{| h |}^{2}} (x) d x} - - - (4)

Wherein, | h^TH| for the thresholding of receiving terminal；

Instantaneous bit error rate in the multiple Gauss distribution of substitution channel coefficients h and formula (3), receiving bit error rate is

P (e_{b} | | h | > | h^{T H} |) < \frac{1}{2} \frac{1}{e^{- ρ} α γ + 1} \exp (- {ρe}^{- ρ} α γ) - - - (5)

Wherein ρ=| h^TH|²/2σ²For normalization channel coefficients thresholding, γ is the effective signal-to-noise ratio considering retransmission energy.Formula (4) can be approximately

P (e_{b} | | h | > | h^{T H} |) = \frac{1}{2 α γ} \exp (- {ρe}^{- ρ} α γ + ρ) - - - (6)

(1.4) trying to achieve, based on formula (6), the optimum threshold value minimizing average received bit error rate is

| h_{o}^{T H} | = σ \sqrt{2 [1 - W (\frac{e}{α γ})]} - - - (7) .