CN100421438C

CN100421438C - Bit-loading method in frequency-selective single-carrier block transmission system

Info

Publication number: CN100421438C
Application number: CNB2005100420564A
Authority: CN
Inventors: 杜岩; 袁静; 李剑飞; 宫良
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2005-01-28
Filing date: 2005-01-28
Publication date: 2008-09-24
Anticipated expiration: 2025-01-28
Also published as: CN1649333A

Abstract

The present invention provides a bit loading method in a frequency-selective single-carrier block transmission system, which includes the following steps: (1) After the two parties establish communication, the receiving end selects the number M of available sub-channels and the amplitude gains of these sub-channels , to obtain the equalized noise power, and obtain the system's equalized SNR according to the received SNR and the equalization method; (2) determine the system according to the system's equalized SNR and the SNR loss caused by the channel estimation error and synchronization error Different linear modulation methods adopted, the data describing different linear modulation methods are called modulation method information, and the modulation method information is transmitted to the sending end through the feedback channel; (3) The sending end performs symbol mapping and sends signals according to the received modulation method information; (4) The receiving end demodulates the signal according to the modulation mode information, and makes a decision. The present invention is better than the existing SC-FDE and OFDM systems in terms of spectral efficiency and power efficiency under the condition of ensuring certain system performance.

Description

Bit-loading method in frequency-selective single-carrier block transmission system

(一)技术领域 (1) Technical field

本发明涉及宽带数字通信传输方法。属于宽带无线通信技术领域。The invention relates to a broadband digital communication transmission method. The invention belongs to the technical field of broadband wireless communication.

(二)背景技术 (2) Background technology

通信技术在最近几十年，特别是二十世纪九十年代以来得到了长足发展，对人们日常生活和国民经济的发展产生了深远的影响。而未来通信技术正朝着宽带高速的方向发展，因此许多宽带数字传输技术受到广泛的关注，正交频分复用(以下简称OFDM：OrthogonalFrequency Division Multiplexing)和频域均衡的单载波(以下简称SC-FDE：SingleCarrier with Frequency Domain Equalization)就是两种被人们重视的宽带数字传输技术，它们都属于分块传输技术，而目前OFDM受关注的程度要远远超过SC-FDE，并且在多种标准中成为支撑技术，例如：无线局域网(WLAN：Wireless Local Area Network)中的IEEE802.11a；无线城域网(WMAN：Wireless Metropolitan Area Network)中的IEEE802.16；有线数据传输中的各种高速数字用户线(xDSL：Digital Subscriber Line)都是基于OFDM技术的标准。SC-FDE并没有被这些标准采用，只是在IEEE802.16中与OFDM共同建议为物理层传输技术。Communication technology has developed rapidly in recent decades, especially since the 1990s, and has had a profound impact on people's daily life and the development of the national economy. The future communication technology is developing towards broadband and high speed, so many broadband digital transmission technologies have received widespread attention, such as Orthogonal Frequency Division Multiplexing (hereinafter referred to as OFDM: Orthogonal Frequency Division Multiplexing) and frequency domain balanced -FDE: Single Carrier with Frequency Domain Equalization) are two broadband digital transmission technologies that are valued by people. Become a supporting technology, such as: IEEE802.11a in Wireless Local Area Network (WLAN: Wireless Local Area Network); IEEE802.16 in Wireless Metropolitan Area Network (WMAN: Wireless Metropolitan Area Network); various high-speed digital users in wired data transmission Digital Subscriber Line (xDSL: Digital Subscriber Line) is a standard based on OFDM technology. SC-FDE has not been adopted by these standards, but it is jointly proposed as a physical layer transmission technology together with OFDM in IEEE802.16.

OFDM系统是一种多载波传输技术，它用N个子载波把整个宽带信道分割成N个并行的相互正交的窄带子信道。OFDM系统有许多引人注目的优点：1.非常高的频谱效率；2.实现比较简单；3.抗多径干扰能力和抗衰落能力强；4.可以利用信道状态信息(即自适应OFDM技术)进一步提高频谱效率等等。The OFDM system is a multi-carrier transmission technology, which uses N subcarriers to divide the entire wideband channel into N parallel narrowband subchannels that are orthogonal to each other. The OFDM system has many compelling advantages: 1. Very high spectral efficiency; 2. It is relatively simple to implement; 3. It has strong anti-multipath interference and anti-fading capabilities; 4. It can use channel state information (that is, adaptive OFDM technology ) to further improve the spectral efficiency and so on.

自适应OFDM技术可以根据给定输入信号功率和信道状况，调节不同频域点(也就是不同的子信道)上分配的比特数，控制各子信道上的误码率基本相同，使其满足系统性能要求，尽可能的提高系统传码率，从而实现OFDM系统的比特加载(bit-loading)。这种自适应OFDM技术可以充分利用信道状态信息，提高系统的频谱效率。Adaptive OFDM technology can adjust the number of bits allocated on different frequency domain points (that is, different sub-channels) according to the given input signal power and channel conditions, and control the bit error rate on each sub-channel to be basically the same, so that it meets the requirements of the system. The performance requirement is to increase the system code rate as much as possible, so as to realize the bit-loading of the OFDM system. This adaptive OFDM technology can make full use of channel state information and improve the spectral efficiency of the system.

正是这些优点使得OFDM成为近十年来的研究热点，以致被认为是未来通信，特别是宽带无线通信的支撑技术。但OFDM系统自身的许多缺点，特别是它的峰值平均功率比(简称PAPR：Peak to Average Power Ratio)过大，限制着它的实用步伐，而现有SC-FDE具有OFDM上述除第四点以外的所有优点，并且不存在OFDM的PAPR问题，性能和效率跟OFDM基本相当。它是人们在研究OFDM的基础上发展而来，这种SC-FDE系统跟OFDM一样采取分块传输，并且采用循环前缀(Cyclic Prefix，简称CP)方式，这样就可以把信号与信道脉冲响应的线性卷积转化为循环卷积，并且消除了多径引起的帧间干扰。这样在接收端采用简单的频域均衡技术就可以消除符号间干扰，例如：迫零均衡和最小均方误差均衡。It is these advantages that make OFDM a research hotspot in the past ten years, so that it is considered as the supporting technology of future communication, especially broadband wireless communication. However, many shortcomings of the OFDM system itself, especially its peak-to-average power ratio (PAPR: Peak to Average Power Ratio) is too large, which limits its practical pace, and the existing SC-FDE has OFDM above except the fourth point All the advantages, and there is no PAPR problem of OFDM, the performance and efficiency are basically equivalent to OFDM. It is developed on the basis of people's research on OFDM. This SC-FDE system adopts block transmission like OFDM, and uses a cyclic prefix (Cyclic Prefix, CP for short), so that the signal and the channel impulse response can be combined. Linear convolution is transformed into circular convolution, and inter-frame interference caused by multipath is eliminated. In this way, inter-symbol interference can be eliminated by adopting simple frequency-domain equalization techniques at the receiving end, such as zero-forcing equalization and minimum mean square error equalization.

SC-FDE系统跟OFDM相比，不存在PAPR问题。而PAPR问题是OFDM系统本身难以用低代价(频谱效率和功率效率)方式解决的问题。因此SC-FDE技术目前受到越来越多的重视。下面简单介绍一下传统SC-FDE系统的数学模型。Compared with OFDM, SC-FDE system does not have PAPR problem. The PAPR problem is a problem that the OFDM system itself is difficult to solve in a low-cost (spectrum efficiency and power efficiency) way. Therefore, SC-FDE technology is receiving more and more attention at present. The following briefly introduces the mathematical model of the traditional SC-FDE system.

SC-FDE系统在发送端发送的一帧时域信号为s(n)，(n＝0，1，…，N-1)，通过多径信道，其中信道的脉冲响应为h(n)，(n＝0，1，…L-1)，信号传输过程中受到加性白高斯噪声(AWGN：Additive White Gaussian Noise)的干扰，设噪声为w(n)，(n＝0，1，…，N-1)，去掉CP之后，接收到的时域信号r(n)为：A frame of time domain signal sent by SC-FDE system at the sending end is s(n), (n=0, 1, ..., N-1), through a multipath channel, where the impulse response of the channel is h(n), (n=0, 1,...L-1), the signal transmission process is interfered by additive white Gaussian noise (AWGN: Additive White Gaussian Noise), let the noise be w(n), (n=0, 1,... , N-1), after removing the CP, the received time-domain signal r(n) is:

$r r ((n no)) = = s the s ((n no)) &CircleTimes; &CircleTimes; h h ((n no)) + + w w ((n no)),, ((n no = = 0,1 0,1,, . . . . . .,, N N - - 11)) - - - - - - ((11))$

其中，表示循环卷积运算。in, Represents a circular convolution operation.

在接收端对信号做离散傅立叶变换(以下简称DFT：Discrete Fourier Transform)变换到频域，根据DFT的时域卷积定理，所得到的频域信号为：At the receiving end, the discrete Fourier transform (hereinafter referred to as DFT: Discrete Fourier Transform) is performed on the signal to the frequency domain. According to the time domain convolution theorem of DFT, the obtained frequency domain signal is:

R(k)＝S(k)·H(k)+W(k)，(k＝0，1，…，N-1) (2)R(k)=S(k)·H(k)+W(k), (k=0, 1,..., N-1) (2)

其中，R(k)，S(k)，H(k)，W(k)分别是r(n)，s(n)，h(n)，w(n)做N点DFT的频域符号，并且，H(k)，(k＝0，1，…，N-1)是信道的频域响应。经过迫零均衡以后频域信号为：Among them, R(k), S(k), H(k), W(k) are the frequency domain symbols of r(n), s(n), h(n), w(n) for N-point DFT respectively , and, H(k), (k=0, 1, . . . , N-1) is the frequency domain response of the channel. After zero-forcing equalization, the frequency domain signal is:

$\overset{~ ~}{S S} ((k k)) = = S S ((k k)) + + \frac{W W ((k k))}{H h ((k k))} = = S S ((k k)) + + \overset{~ ~}{W W} ((k k)),, ((k k = = 0,1 0,1,, . . . . . .,, N N - - 11)) - - - - - - ((33))$

最后，将信号做离散傅里叶逆变换(以下简称IDFT：Inverse Discrete FourierTransform)变回时域进行判决，得到发送端传输的数据。Finally, the signal is transformed back to the time domain by inverse discrete Fourier transform (hereinafter referred to as IDFT: Inverse Discrete FourierTransform) for judgment, and the data transmitted by the sender is obtained.

从(3)式可以看出，最终得到的信号跟发送的真实信号存在误差，这种误差是由噪声引起的，尤其在信道存在深衰点的情况下会过分放大噪声，另外用最小均方误差均衡时会使信号产生畸变。如果在SC-FDE系统中利用了信道状态信息，这些问题就可以得到缓解。因此，申请人提出了一种选频方式的单载波分块传输方法(已申请国家发明专利，专利申请号：200410036439.6)，克服了传统SC-FDE系统不能利用信道状态信息的缺点，这种新的SC-FDE系统具有更高的系统性能和效率。It can be seen from formula (3) that there is an error between the final signal and the real signal sent. This error is caused by noise, especially when there is a deep fading point in the channel, the noise will be over-amplified. In addition, the least mean square Error equalization distorts the signal. These problems can be alleviated if channel state information is utilized in SC-FDE systems. Therefore, the applicant proposed a frequency-selective single-carrier block transmission method (has applied for a national invention patent, patent application number: 200410036439.6), which overcomes the shortcomings of the traditional SC-FDE system that cannot use channel state information. The SC-FDE system has higher system performance and efficiency.

这种选频方式的单载波分块传输方法的实现步骤分为：The implementation steps of the single-carrier block transmission method in this frequency selection mode are divided into:

第一步，找出可用子信道，并将信道是否可用作标记，然后将子信道标记信息通过反向信道发送给发送端。The first step is to find out the available sub-channel and mark whether the channel is available, and then send the sub-channel mark information to the sender through the reverse channel.

接收端根据估计出的信道状态信息H(k)，(k＝0，1，…，N-1)，从N个子信道中，按照幅度增益从大到小选出M(M≤N)个可用子信道，设这M个可用子信道的标号为k_i(i＝0，1，…，M-1)，而将剩下的子信道禁用，用1比特信息，即“0”或“1”标记每个子信道是可用子信道还是禁用子信道，这就是发送端所需要的子信道标记信息，如果接收端作N点的DFT，即共有N个子信道，反馈给发送端的子信道标记信息共有N比特，然后将这N比特信息通过反向信道发回发送端。According to the estimated channel state information H(k), (k=0, 1, ..., N-1), the receiving end selects M (M≤N) sub-channels from N sub-channels according to the amplitude gain from large to small Available sub-channels, set the labels of these M available sub-channels as _ki (i=0, 1, ..., M-1), and disable the remaining sub-channels, using 1-bit information, namely "0" or "1" marks whether each sub-channel is an available sub-channel or a disabled sub-channel. This is the sub-channel marking information required by the sending end. If the receiving end performs N-point DFT, that is, there are N sub-channels in total, and the sub-channel marking information fed back to the sending end There are N bits in total, and then the N bits of information are sent back to the sender through the reverse channel.

第二步，根据子信道标记信息改变信号频谱The second step is to change the signal spectrum according to the sub-channel label information

在发送端收到接收端发送回来的子信道标记信息后，就可以用M个可用子信道来传输信号，这样对一帧M个SC-FDE符号s(n)，(n＝0，1，…，M-1)，作M点DFT变换到频域：After the sending end receives the sub-channel label information sent back by the receiving end, it can use M available sub-channels to transmit signals, so for M SC-FDE symbols s(n) in one frame, (n=0, 1, ..., M-1), do M-point DFT transformation to the frequency domain:

$S S ((i i)) = = {Σ Σ}_{n no = = 00}^{M m - - 11} s the s ((n no)) {e e}^{- - j j \frac{22 π π}{M m} ni ni},, ((i i = = 0,1 0,1,, . . . . . .,, M m - - 11)) - - - - - - ((44))$

就得到M点的频域信号，用选出来的第k_i，(i＝0，1，…，M-1)个可用子信道H(k_i)，(i＝0，1，…，M-1)传输第i个频域信号S(i)，(i＝0，1，…，M-1)，即在可用子信道对应的信号频谱点上放置要传输的频域信号，而将禁用子信道对应的信号频谱点置零，也可以填充一些非信息数据，这样就得到一帧新的频域信号S′(k)，(k＝0，1，…，N-1)，点数为N：The frequency domain signal of M points is obtained, and the selected k _i , (i=0, 1, ..., M-1) available sub-channels H(k _i ), (i = 0, 1, ..., M -1) Transmit the i-th frequency domain signal S(i), (i=0, 1, ..., M-1), that is, place the frequency domain signal to be transmitted on the signal spectrum point corresponding to the available subchannel, and place The signal spectrum points corresponding to the disabled sub-channels are set to zero, and some non-information data can also be filled, so that a new frame of frequency domain signal S'(k), (k=0, 1, ..., N-1), the number of points for N:

${S S}^{' '} ((k k)) = = \{\begin{matrix} S S ((i i)),, & k k = = {k k}_{i i} \\ 00,, & k k &NotEqual; &NotEqual; {k k}_{i i} \end{matrix},, ((k k = = 0,1 0,1,, . . . . . .,, N N - - 11)) - - - - - - ((55))$

然后对S′(k)，(k＝0，1，…，N-1)作N点IDFT：Then do N-point IDFT on S'(k), (k=0, 1, ..., N-1):

${s the s}^{' '} ((n no)) = = \frac{11}{N N} {Σ Σ}_{k k = = 00}^{N N - - 11} {S S}^{' '} ((k k)) {e e}^{j j \frac{22 π π}{N N} nk nk},, ((n no = = 0,1 0,1,, . . . . . .,, N N - - 11)) - - - - - - ((66))$

变成时域信号，过抽样时IDFT点数要大于N，高频部分置零，对该时域信号作D/A(数模变换)后，再进行调制发送出去。It becomes a time-domain signal. When oversampling, the number of IDFT points must be greater than N, and the high-frequency part is set to zero. After D/A (digital-to-analog conversion) is performed on the time-domain signal, it is modulated and sent out.

第三步，选出可用子信道上传输的信号，然后对选出来的信号进行均衡，并变换回时域进行判决，最终得到传输的数据。The third step is to select the signal that can be transmitted on the sub-channel, then equalize the selected signal, and transform it back to the time domain for judgment, and finally obtain the transmitted data.

接收端接收到信号，去掉CP后的时域离散信号为：The receiving end receives the signal, and the time-domain discrete signal after removing the CP is:

${r r}^{' '} ((n no)) = = {s the s}^{' '} ((n no)) &CircleTimes; &CircleTimes; h h ((n no)) + + w w ((n no)),, ((n no = = 0,1 0,1,, . . . . . .,, N N - - 11)) - - - - - - ((77))$

对其作N点的DFT：Do N-point DFT on it:

${R R}^{' '} ((k k)) = = {Σ Σ}_{n no = = 00}^{N N - - 11} {r r}^{' '} ((n no)) {e e}^{- - j j \frac{22 π π}{N N} nk nk},, ((k k = = 0,1 0,1,, . . . . . .,, N N - - 11)) - - - - - - ((88))$

并且：and:

R′(k)＝S′(k)H(k)+W(k)，(k＝0，1，…，N-1) (9)R'(k)=S'(k)H(k)+W(k), (k=0, 1,..., N-1) (9)

这样就可以根据子信道标记信息选出M个可用子信道上的信号R(k_i)，(i＝0，1，…，M-1)，然后用估计出来的信道状态信息中可用子信道参数H(k_i)，(i＝0，1，…，M-1)，对选出来的信号进行均衡；可以选择下述三种均衡方式之一：In this way, the signals R(k _i ), (i=0, 1, ..., M-1) on M available sub-channels can be selected according to the sub-channel label information, and then the available sub-channels in the estimated channel state information can be used The parameter H(k _i ), (i=0, 1, ..., M-1), equalizes the selected signal; one of the following three equalization methods can be selected:

1、迫零均衡，1. Zero-forcing equilibrium,

2、最小均方误差均衡，2. Minimum mean square error equalization,

3、混合均衡，即一部分子信道用迫零均衡，而另一部分子信道用最小均方误差均衡；3. Mixed equalization, that is, some sub-channels are equalized by zero-forcing, while other sub-channels are equalized by minimum mean square error;

以迫零均衡为例作介绍：Take zero-forcing equilibrium as an example for introduction:

$\overset{~ ~}{S S} (({k k}_{i i})) = = \frac{R R (({k k}_{i i}))}{H h (({k k}_{i i}))},, ((i i = = 0,1 0,1,, . . . . . .,, M m - - 11)) - - - - - - ((1010))$

令make

$\overset{~ ~}{S S} ((i i)) = = \overset{~ ~}{S S} (({k k}_{i i})),, ((i i = = 0,1 0,1,, . . . . . .,, M m - - 11)) - - - - - - ((1111))$

对其作M点的IDFT：IDFT of M points on it:

$\overset{~ ~}{s the s} ((n no)) = = \frac{11}{M m} {Σ Σ}_{i i = = 00}^{M m - - 11} \overset{~ ~}{S S} ((i i)) {e e}^{j j \frac{22 π π}{M m} ni ni},, ((n no = = 0,1 0,1,, . . . . . .,, M m - - 11)) - - - - - - ((1212))$

对这组数据进行判决就可以恢复出原始数据。The original data can be restored by making a judgment on this set of data.

选频方式的单载波分块传输方法利用信道状态信息，对频率选择性衰落信道可以避开深衰点，从而显著改善了系统的误码性能。通信系统普遍有一定的性能要求，而系统性能是由均衡后信噪比及信道估计误差和同步误差引起的信噪比损失决定的，均衡后信噪比是指均衡后信号功率和噪声功率的比值。并且均衡后信噪比及信道估计误差和同步误差引起的信噪比损失还决定系统的信道容量，所以根据系统的均衡后信噪比及信道估计误差和同步误差引起的信噪比损失和系统性能要求，自适应的调节系统的调制方式，可进一步提高频谱效率。The frequency-selective single-carrier block transmission method uses channel state information to avoid deep fading points for frequency-selective fading channels, thereby significantly improving the bit error performance of the system. Communication systems generally have certain performance requirements, and system performance is determined by the signal-to-noise ratio after equalization and the loss of signal-to-noise ratio caused by channel estimation errors and synchronization errors. ratio. And the SNR loss caused by the equalized SNR and channel estimation error and synchronization error also determines the channel capacity of the system, so according to the SNR after equalization of the system, the SNR loss caused by the channel estimation error and synchronization error and the system According to the performance requirements, the modulation mode of the adaptive adjustment system can further improve the spectrum efficiency.

(三)发明内容 (3) Contents of the invention

针对上述选频方式的单载波分块传输方法，本发明提供一种基于该传输方法的可以充分利用发送功率、提高系统频谱利用率的比特加载方法。Aiming at the above-mentioned single-carrier block transmission method in the frequency selection mode, the present invention provides a bit loading method based on the transmission method that can make full use of the transmission power and improve the utilization rate of the system spectrum.

该比特加载方法包括以下步骤：The bitloading method includes the following steps:

(1)收发双方建立通信后，接收端根据选取的可用子信道数M及这些子信道的幅度增益|H(k_i)|，(i＝0，1，…，M-1)，得到均衡后噪声功率，记为σ²，根据接收信噪比和均衡方式得到系统的均衡后信噪比记为SNR_eq；(1) After the sending and receiving parties establish communication, the receiving end obtains the equalization according to the number of available sub-channels M selected and the amplitude gains of these sub-channels |H(k _i )|, (i=0, 1, ..., M-1). The post-noise power is denoted as σ ² , and the post-equalization SNR of the system obtained according to the received SNR and equalization method is denoted as SNR _eq ;

(2)根据系统的均衡后信噪比及信道估计误差和同步误差引起的信噪比损失确定系统采取的不同线性调制方式，描述不同线性调制方式的数据称为调制方式信息，通过反馈信道将调制方式信息传给发送端；(2) Determine the different linear modulation modes adopted by the system according to the signal-to-noise ratio after equalization of the system and the loss of signal-to-noise ratio caused by channel estimation errors and synchronization errors. The data describing different linear modulation modes is called modulation mode information. Through the feedback channel, the The modulation mode information is transmitted to the sending end;

(3)发送端根据接收到的调制方式信息进行符号映射发送信号；(3) The sending end performs symbol mapping and sending signals according to the received modulation mode information;

(4)接收端根据调制方式信息解调信号，并判决。(4) The receiving end demodulates the signal according to the modulation mode information, and makes a decision.

下面对以上步骤作详细说明：The above steps are described in detail below:

第(1)步，接收端根据子信道标记信息及接收信噪比和均衡方式计算均衡后信噪比。In step (1), the receiving end calculates the equalized SNR according to the sub-channel label information, the received SNR and the equalization method.

其中，接收信噪比的测量和计算方法可以参照相关文献，在此不作介绍。均衡方式不同，均衡后的信号功率和噪声功率就不同，系统的均衡后信噪比也不同，当采用迫零均衡时，计算均衡后信噪比的方法如下：设接收端根据信道状态信息选取M个可用子信道，这些子信道的幅度增益为|H(k_i)|，(i＝0，1，…，M-1)，且白高斯噪声双边功率谱密度以W/Hz为单位为

则均衡后噪声功率为，以W单位：Wherein, the measurement and calculation method of the receiving signal-to-noise ratio can refer to relevant literature, and will not be introduced here. The equalization method is different, the signal power and noise power after equalization are different, and the signal-to-noise ratio after equalization of the system is also different. When zero-forcing equalization is used, the method of calculating the signal-to-noise ratio after equalization is as follows: Suppose the receiver selects according to the channel state information M available sub-channels, the amplitude gain of these sub-channels is |H(k _i )|, (i=0, 1, ..., M-1), and the white Gaussian noise bilateral power spectral density in W/Hz is

Then the noise power after equalization is, in W:

${σ σ}^{22} = = E E. (({Σ Σ}_{i i = = 00}^{M m - - 11} {| | \frac{N N (({k k}_{i i}))}{H h (({k k}_{i i}))} | |}^{22})) = = \frac{{N N}_{00}}{22} {Σ Σ}_{i i = = 00}^{M m - - 11} {| | \frac{11}{H h (({k k}_{i i}))} | |}^{22} - - - - - - ((1313))$

N(k_i)是序号为k_i子信道上的均衡前的噪声，k_i是第i个可用子信道的序号，设均衡后信号功率为S_eq，则系统的均衡后信噪比为：N(k _i ) is the noise before equalization on the sub-channel with the sequence number _ki , and _ki is the sequence number of the i-th available sub-channel. If the signal power after equalization is _Seq , then the SNR of the system after equalization is:

$SN SN {R R}_{eq eq} = = \frac{{S S}_{eq eq}}{{σ σ}^{22}} . . - - - - - - ((1414))$

第(2)步，根据系统的均衡后信噪比及信道估计误差和同步误差引起的信噪比损失确定系统采用的不同线性调制方式。In step (2), different linear modulation modes adopted by the system are determined according to the SNR after equalization of the system and the SNR loss caused by channel estimation error and synchronization error.

经分析，当信道估计误差和同步误差可以忽略时，多径环境下的选频单载波分块传输系统均衡后可以等价为通过理想高斯信道的通信系统，均衡后信噪比等价为在理想高斯信道下的信噪比，所以系统的误码率由均衡后信噪比决定，则SNR＝SNR_eq，当考虑信道估计误差和同步误差时，通过测量实际的接收信噪比下的误比特率性能，和计算出的没有信道估计误差和同步误差的系统达到同样的误比特率所需要的信噪比，就能够估计出信噪比损失，记为SNR_loss，信噪比损失的计算方法可以参考有关文献，这时决定系统误码性能的是均衡后信噪比和信噪比损失的比值，记为SNR＝SNR_eq/SNR_loss，其中信噪比损失SNR_loss的计算方法可以参照相关文献；After analysis, when the channel estimation error and synchronization error can be ignored, the frequency-selective single-carrier block transmission system in the multipath environment can be equivalent to a communication system through an ideal Gaussian channel after equalization, and the SNR after equalization is equivalent to The signal-to-noise ratio under the ideal Gaussian channel, so the bit error rate of the system is determined by the equalized signal-to-noise ratio, then SNR=SNR _eq , when considering the channel estimation error and synchronization error, by measuring the error rate under the actual receiving signal-to-noise ratio The bit rate performance, and the calculated signal-to-noise ratio required for the system without channel estimation error and synchronization error to achieve the same bit error rate, can estimate the signal-to-noise ratio loss, denoted as SNR _loss , and the calculation of the signal-to-noise ratio loss The method can refer to the relevant literature. At this time, the ratio of the signal-to-noise ratio and the SNR loss after equalization determines the bit error performance of the system, which is recorded as SNR=SNR _eq /SNR _loss . The calculation method of the SNR loss SNR _loss can refer to related literature;

如果采取一种调制方式，要达到系统要求的误比特率BER_req，所需的信噪比一般高子或者低于SNR，为了充分利用功率，提高传码率，可以采用两种或两种以上不同进制的调制方式。因为系统的每个时域点只能携带整数比特的信息，所以所采用的调制方式的进制数普遍为2^k，(k＝1，2，…)，在选频单载波分块传输系统中，普遍采取线性调制方式，如QAM或者MPSK，下面以采取两种调制方式为例介绍：If a modulation method is adopted to achieve the bit error rate BER _req required by the system, the required signal-to-noise ratio is generally high or lower than the SNR. In order to make full use of the power and improve the code rate, two or more types can be used Modulation methods of different bases. Because each time-domain point of the system can only carry integer bits of information, the base number of the modulation method used is generally 2 ^k , (k=1, 2, ...), in the frequency-selective single-carrier block transmission system Among them, linear modulation methods are generally adopted, such as QAM or MPSK. The following two modulation methods are used as examples to introduce:

设理想高斯信道情况下，采用两种进制线性调制方式时，达到相同的系统误码要求，即误比特率BER_req，所需要的信噪比分别为SNR_k，(k＝1，2，…)，而选取的两种不同进制的线性调制方式所携带的信息比特数分别为k₁和k₂，且k₂＝k₁+1。若满足In the case of an ideal Gaussian channel, when two binary linear modulation methods are used, the same system bit error requirement is achieved, that is, the bit error rate BER _req , and the required signal-to-noise ratios are SNR _k , (k=1, 2, ...), and the numbers of information bits carried by the two selected linear modulation schemes are k ₁ and k ₂ respectively, and k ₂ =k ₁ +1. If satisfied

SNR_k≤SNR ≤SNR_k+1，(k＝1，2，…) (15)SNR _k ≤ SNR ≤ SNR _k+1 , (k=1, 2, ...) (15)

则：k₁＝k (16)Then: k ₁ =k (16)

平均映射功率是指采用不同调制方式映射时对应所有星座点的平均功率。设所选取的两种线性调制方式的平均映射功率分别为S₁和S₂，则每帧中携带k₂比特信息的点数为：The average mapping power refers to the average power corresponding to all constellation points when different modulation modes are used for mapping. Assuming that the average mapping powers of the two selected linear modulation methods are S ₁ and S ₂ respectively, then the number of points carrying k _2- bit information in each frame is:

表示下取整。则每帧中携带k₁比特信息的点数为：

Indicates rounding down. Then the number of points carrying k _1- bit information in each frame is:

M₁＝M-M₂ (18)M ₁ =MM ₂ (18)

这样，每帧有M₁个时域点采用

进制调制，M₂个时域点采用

进制调制，在实际情况中，系统所提供的功率要留有一定的余量，使系统能够达到所要求的相对稳定的性能。In this way, each frame has M ₁ time-domain points using

Hexadecimal modulation, M ₂ time domain points adopt

In the actual situation, the power provided by the system should have a certain margin, so that the system can achieve the required relatively stable performance.

将每帧M个时域点中采用

进制调制方式的点数M₁和每点携带的信息比特数k₁，形成调制方式信息，将其同子信道标记信息一起传回发送端。Use M time domain points in each frame

The number of points M ₁ of the base modulation mode and the number of information bits k ₁ carried by each point form the modulation mode information, which is sent back to the sending end together with the sub-channel label information.

第(3)步，发送端根据接收到的调制方式信息进行符号映射，根据子信道标记信息进行信号变换，发送信号；In step (3), the transmitting end performs symbol mapping according to the received modulation mode information, performs signal transformation according to the sub-channel label information, and sends the signal;

发送端根据反馈的调制方式信息k₁，M₁以及可用子信道数M，其中M可以根据子信道标记信息得到，和系统给出的发送信号功率，就可以进行调制映射，任意选取M₁个时域点，令每个点携带k₁比特信息进行

进制调制，剩余的M₂个时域点，每个点携带k₂比特信息进行进制调制，具体哪些点采用

进制调制，哪些采用

进制调制由通信双方采用的约定或通信协议规定，例如，可以选定一帧数据的前M₁个时域点采用进制调制，后M₂个时域点采取

进制调制；将每帧发送端的发送总功率按照不同调制方式的平均映射功率比值分配到M个时域点上，然后发送信号，例如，前M₁个时域点采用

进制调制，后M₂个时域点采用

进制调制，前M₁个时域点平均每个点分配的功率跟后M₂个时域点分配的平均功率比值为

并且每帧中采用相同调制方式的时域点分配的功率相同。完成符号映射后，根据子信道标记信息按背景技术中提到的选频单载波分块传输方法进行信号变换，发送信号。The transmitter can perform modulation mapping according to the feedback modulation information k ₁ , M ₁ and the number of available sub-channels M, where M can be obtained from the sub-channel label information and the transmission signal power given by the system, and M ₁ can be selected arbitrarily Points in the time domain, let each point carry k _1- bit information for

Hexadecimal modulation, the remaining M ₂ time-domain points, each point carrying k _2- bit information Hexadecimal modulation, which specific points are used

Modulation, which uses

The hexadecimal modulation is stipulated by the agreement or communication protocol adopted by the two parties in communication. For example, the first _M1 time domain points of a frame of data can be selected to use Hexadecimal modulation, after M ₂ time domain points are taken

Hexadecimal modulation; distribute the total transmission power of the sending end of each frame to M time domain points according to the average mapping power ratio of different modulation modes, and then send signals, for example, the first M ₁ time domain points use

Hexadecimal modulation, the last M ₂ time domain points adopt

Base modulation, the ratio of the average power allocated to each point in the first M ₁ time domain points to the average power allocated to the next M ₂ time domain points is

And the power allocated to the time domain points using the same modulation mode in each frame is the same. After symbol mapping is completed, signal conversion is performed according to the sub-channel label information according to the frequency-selective single-carrier block transmission method mentioned in the background technology, and the signal is sent.

第(4)步，接收端根据调制方式信息解调信号。In step (4), the receiving end demodulates the signal according to the modulation mode information.

接收端根据子信道标记信息选出可用子信道上的信号，经过均衡之后变回时域，再根据不同时域点采用的调制方式对信号进行解调和判决，得到正确的传输数据，解调方法跟发送端进行信号映射类似，是信号映射的逆过程，如果按照第(3)步的例子，解调时前M₁个时域点进行

进制解调判决，而后M₂个时域点进行

进制解调判决。The receiving end selects the signal on the available sub-channel according to the sub-channel label information, and changes it back to the time domain after equalization, and then demodulates and judges the signal according to the modulation method adopted by different time domain points to obtain the correct transmission data, demodulate The method is similar to the signal mapping at the sending end, which is the inverse process of signal mapping. If the example in step (3) is followed, the first M ₁ time domain points are demodulated

base demodulation judgment, and then M ₂ time domain points

Hexadecimal demodulation judgment.

本发明基于选频方式的单载波分块传输方法，在时域自适应地加载信息比特，可以更加充分的利用信号发射功率。在保证误码率稳定的情况下，根据接收信噪比和均衡方式及信道估计误差和同步误差造成的信噪比损失，可以自适应调节传码率。本发明提出的自适应方法在整体性能上比传统的自适应OFDM稍差，但在实现复杂度方面，该自适应方法远远低于传统的自适应OFDM系统。The present invention is based on the single-carrier block transmission method of the frequency selection mode, adaptively loads information bits in the time domain, and can make more full use of signal transmission power. In the case of ensuring a stable bit error rate, the bit rate can be adaptively adjusted according to the signal-to-noise ratio loss caused by the received signal-to-noise ratio and equalization method, as well as channel estimation error and synchronization error. The overall performance of the adaptive method proposed by the present invention is slightly worse than that of traditional adaptive OFDM, but in terms of implementation complexity, the adaptive method is far lower than that of traditional adaptive OFDM systems.

本发明在保证系统性能一定的情况下，频谱效率、功率效率都优于现有SC-FDE和OFDM系统，整个系统增加的复杂度小。Under the condition that the system performance is guaranteed, the present invention is superior to the existing SC-FDE and OFDM systems in terms of frequency spectrum efficiency and power efficiency, and the added complexity of the whole system is small.

(四)附图说明 (4) Description of drawings

附图是实现本发明所提出方法的系统框图。Accompanying drawing is the system block diagram that realizes the method proposed by the present invention.

图中：1.信源模块，2.符号映射模块，3.FFT模块(M点)，4.信号频谱变换模块，5.IFFT模块(N点)，6.加循环前缀(CP)模块，7.D/A模块，8.中频及射频调制模块，9.信道，10.射频及中频解调模块，11.A/D模块，12.去CP模块，13.FFT模块(N点)，14.信号频谱反变换模块，15.均衡模块，16.IFFT模块(M点)，17.判决模块，18.同步模块，19.信道估计模块，20.调制方式确定模块，21.反向信道In the figure: 1. Source module, 2. Symbol mapping module, 3. FFT module (M point), 4. Signal spectrum transformation module, 5. IFFT module (N point), 6. Cyclic prefix (CP) module, 7. D/A module, 8. IF and RF modulation module, 9. Channel, 10. RF and IF demodulation module, 11. A/D module, 12. CP removal module, 13. FFT module (N points), 14. Signal spectrum inverse transformation module, 15. Equalization module, 16.IFFT module (M point), 17. Judgment module, 18. Synchronization module, 19. Channel estimation module, 20. Modulation method determination module, 21. Reverse channel

(五)具体实施方式 (5) Specific implementation methods

实施例：Example:

附图给出了实现本发明所提出方法的系统框图，各模块作用如下：Accompanying drawing has provided the system block diagram realizing the proposed method of the present invention, and each module effect is as follows:

信源模块1：产生要传输的数据。Source module 1: Generates data to be transmitted.

符号映射模块2：根据反向信道21传回的调制方式信息选择不同进制的调制方式(QAM或者MPSK)，将信源产生的数据映射到星座图对应点上。Symbol mapping module 2: select different modulation schemes (QAM or MPSK) according to the modulation scheme information returned by the reverse channel 21, and map the data generated by the information source to the corresponding points of the constellation diagram.

M点FFT模块3：将每帧M个已映射信号变换到频域，得到信号的M点频域信号。M-point FFT module 3: Transform the M mapped signals of each frame into the frequency domain to obtain M-point frequency domain signals of the signal.

信号频谱变换模块4：根据接收端通过反向信道21发送回来的子信道标记信息，将模块3输出的M点频域信号放置到M个可用子信道对应频谱点上，而禁用子信道对应频谱点置零，或填充非信息数据，就得到一帧N点新的SC-FDE频域信号。此模块需要按照背景技术中提到的发明专利(专利申请号：200410036439.6)介绍的方法编程，由通用数字信号处理芯片实现。Signal spectrum transformation module 4: according to the subchannel label information sent back by the receiving end through the reverse channel 21, place the M point frequency domain signal output by module 3 on the spectrum points corresponding to the M available subchannels, and disable the corresponding spectrum of the subchannels If the points are set to zero or filled with non-information data, a new SC-FDE frequency domain signal of N points in a frame is obtained. This module needs to be programmed according to the method introduced in the invention patent (patent application number: 200410036439.6) mentioned in the background technology, and it is realized by a general digital signal processing chip.

N点IFFT模块5：将新得到的频域信号再变换到时域。N-point IFFT module 5: Transform the newly obtained frequency domain signal into the time domain.

加CP模块6：将得到的每帧数据加上循环前缀。Add CP module 6: Add a cyclic prefix to each frame of data obtained.

D/A模块7：将数字信号变换为模拟信号。D/A module 7: Convert digital signal to analog signal.

中频及射频调制模块8：如果在无线环境下使用该系统，需要对信号作射频调制才能送天线发射。有的时候需要先把信号调制到中频上进行中频放大，再作射频调制，最后将已调信号送天线发射。如果在有线环境(例如：xDSL)下使用该系统，则不需要作射频调制，也不需要天线发射信号，但也要把信号频谱搬移到语音信道频带以外，保证在传输数据的同时不影响话音传输。IF and RF modulation module 8: If the system is used in a wireless environment, the signal needs to be modulated by RF to send it to the antenna for transmission. Sometimes it is necessary to modulate the signal to the intermediate frequency for intermediate frequency amplification, then perform radio frequency modulation, and finally send the modulated signal to the antenna for transmission. If the system is used in a wired environment (for example: xDSL), there is no need for radio frequency modulation, and there is no need for antennas to transmit signals, but the signal spectrum must also be moved outside the frequency band of the voice channel to ensure that the voice is not affected while transmitting data transmission.

信道9：传输信号的有线信道或无线信道。Channel 9: A wired or wireless channel for transmitting signals.

同步模块18：通过参数估计(例如：盲估计和基于辅助数据的估计)的方法得到系统需要的各种同步数据。同步模块将频率同步数据送给射频及中频解调模块10；将抽样率同步数据送给模数转换模块11；将定时同步数据送给去CP模块12。Synchronization module 18: Obtain various synchronization data required by the system through parameter estimation (for example: blind estimation and estimation based on auxiliary data). The synchronization module sends the frequency synchronization data to the radio frequency and intermediate frequency demodulation module 10 ; sends the sampling rate synchronization data to the analog-to-digital conversion module 11 ; and sends the timing synchronization data to the CP module 12 .

射频及中频解调模块10：在无线环境中，将接收天线接收下来信号的频谱从射频或者中频搬移到低频。在解调之前需要用频率同步数据纠正信号传输过程中引起的频偏。Radio frequency and intermediate frequency demodulation module 10: In a wireless environment, move the frequency spectrum of the signal received by the receiving antenna from radio frequency or intermediate frequency to low frequency. Before demodulation, it is necessary to use frequency synchronization data to correct the frequency deviation caused in the signal transmission process.

A/D模块11：将解调后模拟信号变换为数字信号。A/D需要对模拟信号进行抽样，提供时钟信号的晶振需要跟发射机D/A模块的晶振频率相同，否则就会导致抽样率误差。因此在A/D之前要进行抽样率同步。A/D module 11: Convert the demodulated analog signal into a digital signal. The A/D needs to sample the analog signal, and the crystal oscillator that provides the clock signal needs to have the same frequency as the crystal oscillator of the D/A module of the transmitter, otherwise it will cause a sampling rate error. Therefore, the sampling rate must be synchronized before the A/D.

去CP模块12：将循环前缀去掉。这时就存在判断一帧数据何时开始的问题，因此去CP之前需要作定时同步。Go to CP module 12: remove the cyclic prefix. At this time, there is a problem of judging when a frame of data starts, so timing synchronization is required before going to the CP.

N点FFT模块13：将去掉CP的信号变换到频域。N-point FFT module 13: Transform the CP-removed signal into the frequency domain.

信道估计模块19：跟同步类似，也需要通过参数估计来得到CSI，常用的一般是盲信道估计和基于辅助数据的信道估计。估计出CSI后选出可用子信道，将这些可用子信道参数送给均衡模块15；同时根据信道是否可用，用1比特信息(“0”或“1”)标记，形成子信道标记信息，将子信道标记信息同时送给信号频谱反变换模块14和反向信道21，通过反向信道发回发送端的信号频谱变换模块4；并将可用子信道状态信息传给调制方式确定模块20。此模块需要按照背景技术中提到的发明专利(专利申请号：200410036439.6)介绍的方法编程，由通用数字信号处理芯片实现。Channel estimation module 19: Similar to synchronization, it is also necessary to obtain CSI through parameter estimation. Commonly used are blind channel estimation and channel estimation based on auxiliary data. After estimating the CSI, the available sub-channels are selected, and these available sub-channel parameters are sent to the equalization module 15; at the same time, according to whether the channel is available, it is marked with 1-bit information ("0" or "1") to form sub-channel marking information, and the The subchannel label information is sent to the signal spectrum inverse transformation module 14 and the reverse channel 21 at the same time, and is sent back to the signal spectrum transformation module 4 at the sending end through the reverse channel; and the available subchannel state information is transmitted to the modulation mode determination module 20 . This module needs to be programmed according to the method introduced in the invention patent (patent application number: 200410036439.6) mentioned in the background technology, and it is realized by a general digital signal processing chip.

信号频谱反变换模块14：根据信道估计模块19送来的子信道标记信息，找出接收信号中由可用子信道携带的M点频域信号。此模块需要按照背景技术中提到的发明专利(专利申请号：200410036439.6)介绍的方法编程，由通用数字信号处理芯片实现。The signal spectrum inverse transformation module 14: according to the subchannel label information sent by the channel estimation module 19, find out the frequency domain signals of M points carried by available subchannels in the received signal. This module needs to be programmed according to the method introduced in the invention patent (patent application number: 200410036439.6) mentioned in the background technology, and it is realized by a general digital signal processing chip.

均衡模块15：用信道估计模块19送来的可用子信道参数，对信号频谱反变换模块14选出来的信号进行均衡。均衡方式可以选择下述三种均衡方式之一：迫零均衡、最小均方误差均衡、混合均衡(即：一部分子信道用迫零均衡，而另一部分子信道用最小均方误差均衡)。Equalization module 15: use the available sub-channel parameters sent by the channel estimation module 19 to equalize the signal selected by the signal spectrum inverse transformation module 14. The equalization method can choose one of the following three equalization methods: zero-forcing equalization, minimum mean square error equalization, and mixed equalization (that is, some sub-channels use zero-forcing equalization, while other sub-channels use minimum mean square error equalization).

M点IFFT模块16：将均衡后信号的M个频域信号变换到时域。M-point IFFT module 16: Transform the M frequency domain signals of the equalized signal into the time domain.

判决模块17：根据星座图和调制方式确定模块20传来的调制方式信息，完成时域信号的判决。Judgment module 17: according to the constellation diagram and the modulation scheme information transmitted from the modulation scheme determination module 20, complete the judgment of the time-domain signal.

调制方式确定模块20：根据信道估计模块19传来的可用子信道的状态信息和发送端提供的发送信号功率计算系统的均衡后信噪比，根据均衡后信噪比及信道估计误差和同步误差损失的信噪比确定每帧采取的调制方式，将调制方式信息传给判决模块17，并通过反向信道21传给发送端的映射模块2。此模块需要按照本发明介绍的方法编程，由通用数字信号处理芯片实现。Modulation mode determination module 20: Calculate the SNR after equalization of the system according to the state information of the available sub-channels transmitted from the channel estimation module 19 and the transmission signal power provided by the transmitting end, and according to the SNR after equalization and the channel estimation error and synchronization error The lost SNR determines the modulation mode adopted by each frame, and the modulation mode information is transmitted to the judgment module 17 and then transmitted to the mapping module 2 at the sending end through the reverse channel 21 . This module needs to be programmed according to the method introduced in the present invention, and is realized by a general-purpose digital signal processing chip.

反向信道21：将子信道标记信息和调制方式信息传回发送端。Reverse channel 21: transmit subchannel label information and modulation mode information back to the sender.

该实施例仿真参数：The simulation parameters of this embodiment:

仿真环境：Matlab7.0Simulation environment: Matlab7.0

子信道总数：N＝256Total number of sub-channels: N=256

可用子信道数，即每帧SC-FDE数据符号数：M＝208。The number of available sub-channels, that is, the number of SC-FDE data symbols per frame: M=208.

调制方式：QAMModulation method: QAM

CP长度：32CP length: 32

控制的误码率为：BER_req＝10-4Controlled bit error rate: BER _req = 10-4

仿真所选的收信噪比范围：SNR＝9∶30(dB)The range of receiving signal-to-noise ratio selected by simulation: SNR=9:30(dB)

信噪比损失：SNR_loss＝0(dB)(即忽略信道估计误差和同步误差造成的信噪比损失)SNR loss: SNR _loss = 0 (dB) (that is, ignoring the SNR loss caused by channel estimation error and synchronization error)

本实施例采用的信道模型是SUI-5信道(IEEE 802.16标准中建议的测试信道之一)的一个样本。The channel model used in this embodiment is a sample of the SUI-5 channel (one of the test channels suggested in the IEEE 802.16 standard).

下面附表第一列给出了系统提供的接收信噪比(单位：dB)；第二列和第三列为采用比特加载方法时不同接收信噪比对应的每帧信号传输的比特数和相应误码率；第四列和第五列为未采用比特加载方法时不同接收信噪比对应的每帧信号传输的比特数和相应误码率。从该表中可以看出，在接收信噪比相同的情况下，未采用比特加载方法系统的误码率比要求的误码率10^-4低很多，但传码率却远远比不上误码率相对稳定的采用比特加载方法的系统。这说明比特加载方法在控制误码率相对稳定的情况下，可以很大程度上提高频谱效率。The first column of the attached table below shows the received signal-to-noise ratio (unit: dB) provided by the system; the second and third columns are the number of bits and bits transmitted per frame corresponding to different received signal-to-noise ratios when using the bit loading method Corresponding bit error rate; the fourth and fifth columns are the number of bits per frame signal transmission and the corresponding bit error rate corresponding to different received signal-to-noise ratios when the bit loading method is not used. It can be seen from the table that, under the same receiving SNR, the bit error rate of the system without bit loading method is much lower than the required bit error rate of 10 ^-4 , but the bit rate is far lower than that of A system using the bit-loading method with a relatively stable bit error rate. This shows that the bit loading method can greatly improve the spectral efficiency under the condition that the bit error rate is relatively stable.

附表：Schedule:

其中，“--”表示误码率低于10^-7。Wherein, "--" indicates that the bit error rate is lower than 10 ^-7 .

为避免混淆，本说明书中所提到的一些名词做以下解释：To avoid confusion, some terms mentioned in this manual are explained as follows:

1.均衡后信噪比：均衡之后信号功率跟噪声功率的比值。1. SNR after equalization: The ratio of signal power to noise power after equalization.

2.平均映射功率：不同调制方式映射时对应所有不同星座点的平均功率。2. Average mapping power: the average power corresponding to all different constellation points when different modulation modes are mapped.

3.符号：是指信息比特经过调制映射(也称符号映射)后的数据。一般是一个实部和虚部均为整数的复数。3. Symbol: refers to the data after information bits are modulated and mapped (also called symbol mapping). Usually a complex number whose real and imaginary parts are integers.

4.一帧信号：对于OFDM，一帧信号在发送端是指作IFFT变换的N个符号，在接收端是指在去掉CP以后作FFT变换的N个符号。对于SC-FDE，一帧信号在发送端是指相邻两个CP之间的N个信息符号，在接收端是指在去掉CP以后作FFT变换的N个符号。对于按本发明提出的方法实现的SC-FDE系统，一帧信号在发送端是指作FFT变换的M个符号，在接收端是指在均衡以后作IFFT变换的M个符号。4. One frame signal: For OFDM, one frame signal refers to N symbols that undergo IFFT transformation at the sending end, and at the receiving end refers to N symbols that undergo FFT transformation after removing the CP. For SC-FDE, a frame signal refers to the N information symbols between two adjacent CPs at the sending end, and refers to the N symbols transformed by FFT after removing the CP at the receiving end. For the SC-FDE system realized by the method proposed by the present invention, a frame signal refers to M symbols that are transformed by FFT at the sending end, and refers to M symbols that are transformed by IFFT after equalization at the receiving end.

5.子信道：对于OFDM，SC-FDE基带信号，一个子信道是指在接收端FFT后一个频率点。对于射频信道，一个子信道是指射频信道的一段频谱。5. Sub-channel: For OFDM and SC-FDE baseband signals, a sub-channel refers to a frequency point after FFT at the receiving end. For a radio frequency channel, a subchannel refers to a section of frequency spectrum of the radio frequency channel.

6.信噪比：信号功率和噪声功率的比值，其中发明内容里面提到的信噪比是未取对数的，没有单位；实施例中提到的信噪比是对数信噪比，单位是dB。6. Signal-to-noise ratio: the ratio of signal power to noise power, wherein the signal-to-noise ratio mentioned in the summary of the invention is not logarithmic and has no unit; the signal-to-noise ratio mentioned in the embodiments is a logarithmic signal-to-noise ratio, The unit is dB.

Claims

1. A bit loading method in a frequency-selective single-carrier block transmission system, characterized in that:

The method includes the following steps:

(1) After the sending and receiving parties establish communication, the receiving end obtains the equalized noise according to the selected number of available sub-channels M and the amplitude gains of these sub-channels |H(k _i )|, i=0, 1, ..., M-1 Power, recorded as σ ² , according to the received signal-to-noise ratio and equalization method, the system's equalized signal-to-noise ratio is recorded as SNR _eq ;

(2) According to the signal-to-noise ratio after equalization of the system and the signal-to-noise ratio loss caused by channel estimation errors and synchronization errors, determine the different linear modulation methods adopted by the system. The data describing different linear modulation methods is called modulation information. Through the feedback channel, the The modulation mode information is transmitted to the sending end;

(3) The sending end performs symbol mapping and sending signals according to the received modulation mode information;

(4) The receiving end demodulates the signal according to the modulation mode information, and makes a decision.

2. the bit loading method in the frequency-selective single-carrier block transmission system according to claim 1, is characterized in that: (1) step adopts following method to realize:

When zero-forcing equalization is used, the method of calculating the SNR after equalization is as follows: Suppose the receiving end selects M available sub-channels according to the channel state information, and the amplitude gain of these sub-channels is |H(k _i )|, i=0, 1,...,M-1, and the white Gaussian noise bilateral power spectral density in W/Hz is Then the equalized noise power in W is:

{σ σ}^{22} = = E E. (({Σ Σ}_{i i = = 00}^{M m - - 11} {| | \frac{N N (({k k}_{i i}))}{H h (({k k}_{i i}))} | |}^{22})) = = \frac{{N N}_{00}}{22} {Σ Σ}_{i i = = 00}^{M m - - 11} {| | \frac{11}{H h (({k k}_{i i}))} | |}^{22}

N(k _i ) is the noise before equalization on the sub-channel with the sequence number _ki , and _ki is the sequence number of the i-th available sub-channel. If the signal power after equalization is _Seq , then the SNR of the system after equalization is:

{SNR SNR}_{eq eq} = = \frac{{S S}_{eq eq}}{{σ σ}^{22}} . .

3. the bit loading method in the frequency-selective single-carrier block transmission system according to claim 1, is characterized in that: (2) step adopts following method to realize:

When the channel estimation error and synchronization error can be ignored, the frequency-selective single-carrier block transmission system in the multipath environment is equivalent to the communication system through the ideal Gaussian channel after equalization, and the SNR after equalization is equivalent to the ideal Gaussian channel. SNR, so the bit error rate of the system is determined by the SNR after equalization, then SNR=SNR _eq ; when considering the channel estimation error and synchronization error, by measuring the bit error rate performance under the actual receiving SNR, The calculated signal-to-noise ratio required for the system without channel estimation error and synchronization error to achieve the same bit error rate can estimate the signal-to-noise ratio loss, which is recorded as SNR _loss . At this time, the system's bit error performance is determined by the balance The ratio of back signal-to-noise ratio and signal-to-noise ratio loss is recorded as SNR=SNR _eq /SNR _loss ;

In order to make full use of the power and improve the code rate, two or more modulation modes of different bases are used. Because each sub-channel of the system can only carry integer bits of information, the base number of the modulation mode used is 2 ^k , k=1, 2,..., in the frequency-selective single-carrier block transmission system, the linear modulation method is adopted, when two modulation methods are used:

In the case of an ideal Gaussian channel, when two binary linear modulation methods are used, the same system bit error requirement is achieved, that is, the bit error rate BER _req , and the required signal-to-noise ratios are SNR _k , k=1, 2, ... , and the numbers of information bits carried by the two selected linear modulation schemes are k ₁ and k ₂ respectively, and k ₂ =k ₁ +1; if it satisfies

SNR _k ≤ SNR ≤ SNR _k+1 , k=1, 2, ...

Then: k ₁ =k

The average mapping power refers to the average power corresponding to all constellation points when different modulation methods are used for mapping. Assuming that the average mapping powers of the two selected linear modulation methods are S ₁ and S ₂ , then each frame carries k ₂ bits of information The number of subchannels is:

Indicates the lower integer; then the number of sub-channels carrying k _1- bit information in each frame is:

M ₁ =MM ₂

In this way, each frame has M ₁ subchannels using

Hexadecimal modulation, M ₂ sub-channels adopt

In the actual situation, the power provided by the system should have a certain margin, so that the system can achieve the required relatively stable performance;

The number of sub-channels M ₁ of the base modulation mode and the number of information bits k ₁ carried by each sub-channel form the modulation mode information, which is sent back to the sending end together with the sub-channel label information.