Modulated Coding For Frequency-Selective Multipath Channels

本研究涉及频率选择性衰落信道中多径干扰的抑制。随着人们对宽带数字无线通信的需求越来越大，如无线图像/视频网页浏览和无线数据传输，技术挑战呈指数级增长。其中一个挑战是，当信道的带宽变宽时，无线系统中会出现更多严重的多路径。这意味着多径干扰的抑制变得比以往任何时候都更加重要。调制编码（MC）是一种定义在复场上的卷积编码，最近由PI提出，当发送端和接收端都知道码间干扰（ISI）信道时，它可以最优地减轻码间干扰（ISI）。MC的优点是，由于MC和ISI的算术运算都在复杂场上，因此它们可以自然地结合在一起，这为给定ISI信道的最优MC研究提供了方便。由于MC的编码简单，在MC之前进一步添加常规纠错编码（ECC）也很方便。研究表明，在低信噪比下，ISI信道的组合纠错编码和turbo编码的性能可能优于AWGN信道的容量。例如，对于两个分接ISI信道[0.7071,0.7071]，在码率为1/4时误码率为0.00001，信噪比E_b/N_0=-1.15 dB，高于awgn信道容量。以前MC研究的缺点是发射机需要知道ISI信道，尽管对于某些应用（如存储信道和有线信道）可能是可能的，但对于其他一些应用（如无线信道）可能不实用。本提案的目的是优化设计和更新mcs，而不需要充分了解发射机的ISI/多径信道，特别是在无线通信系统中。由于MC的结构简单，因此可以在发送端进行MC更新，这与现有的编码方案不同。

This research involves the mitigation of multipath interferencesin a frequency-selective fading channel. As broadband digital wirelesscommunications is more demanded than ever, such as wireless image/videoweb browsing and wireless data transmission, the technical challengesare exponentially increasing. One of such challenges is that, when thebandwidth of a channel becomes wider, there are more severe multipathsin a wireless system. This implies that the multipath interferencemitigation becomes more important than ever.Modulated coding (MC), a convolutional coding defined on the complexfield, has been recently proposed by the PI to optimally mitigateintersymbol interferences (ISI) when the ISI channel is known at boththe transmitter and the receiver. The advantage of MC is that, sincethe arithmetic operations of both MC and ISI are over the complex field,they can be naturally combined together, which provides the convenienceof the optimal MC study for a given ISI channel. Since the encodingsimplicity of the MC, it is also convenient for further adding aconventional error correction coding (ECC) before the MC. It has beenshown that the combined MC and turbo coding of an ISI channel mayoutperform the AWGN channel capacity at low SNR. As an example, for thetwo tap ISI channel [0.7071,0.7071], the bit error rate is 0.00001 at thecode rate 1/4 and the SNR E_b/N_0=-1.15 dB, which is above the AWGNchannel capacity. The disadvantage of the previous MC study is that thetransmitter needs to know the ISI channel, which although may be possiblefor some applications, such as storage channels and wireline channels,may not be practical for some other applications, such as wirelesschannels. The aim of this proposal is to optimally design and update MCwithout the full knowledge of the ISI/multipath channel at thetransmitter with applications, in particular, in wireless communicationsystems. Due to the simple structure of MC, the MC update at thetransmitter is possible, which is unlike the existing coding schemes.