Modulated Coding For Frequency-Selective Multipath Channels

频率选择性多径信道的调制编码

• 批准号: 0097240
• 负责人: Xiang-Gen Xia
• 金额: $ 29.91万
• 依托单位: University of Delaware
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-01 至 2006-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0097240&HistoricalAwards=false
• 关键词: Modulated; Coding; Frequency; Selective; Multipath

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.

这项研究涉及频率选择性衰落信道中多径干扰的抑制。随着宽带数字无线通信的需求越来越大，如无线图像/视频浏览和无线数据传输，技术挑战呈指数级增加。这样的挑战之一是，当信道的带宽变得更宽时，无线系统中会有更严重的多径。这意味着多径干扰的消除变得比以往任何时候都更加重要。调制编码(MC)是一种定义在复数域上的卷积编码，最近由PI提出，用于在发射机和接收机都知道码间干扰(ISI)的情况下最优地抑制符号间干扰(ISI)。MC的优点是，由于MC和ISI的算术运算都是在复数域上进行的，所以它们可以很自然地结合在一起，这为给定ISI信道的最优MC研究提供了便利。由于MC编码的简单性，还便于在MC之前进一步添加传统的纠错编码(ECC)。研究表明，在低信噪比条件下，结合MC和Turbo编码的ISI信道容量可以超过AWGN信道容量。例如，对于两个抽头码间干扰信道[0.7071，0.7071]，在码率1/4和信噪比E_b/N_0=-1.15dB时，误码率为0.00001，高于AWGN码信道容量。以前MC研究的缺点是发送者需要知道ISI信道，这虽然对于某些应用可能是可能的，例如存储信道和有线信道，但对于其他一些应用可能不实用，例如无线信道。该方案的目的是在不完全了解ISI/多径信道的情况下优化设计和更新MC，特别是在无线通信系统中的应用。由于MC的结构简单，与现有的编码方案不同，在发射机上进行MC更新是可能的。