Multiple-Access Codes & Random-Access Protocols with Multiple Reception

多路访问代码

• 批准号: 9304763
• 负责人: Bixio Rimoldi
• 金额: $ 9.59万
• 依托单位: Washington University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-09-01 至 1997-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9304763&HistoricalAwards=false
• 关键词: Multiple; Access; Codes; & Random

9304763 Rimoldi We are approaching the era of personal communication which requires an infrastructure capable of providing untethered access to a global network from any point on (and above) the surface of the earth. Implementation of this scenario requires efficient communication via a wireless network. One major component of a wireless network is the Gaussian multiple-access channel. The objective of the proposed research is to extend recent results of the principal investigator leading to a novel procedure to construct codes for this channel. The following two steps have led to the proposed procedure. Step 1 A simpler channel model called G-adder channel was considered and multiple-access codes for this channel were studied. The G-adder channel associated to some finite group G has inputs that are elements of G and output that is the sum (over G) of the inputs. To start on a more familiar ground it was assumed that G is the additive group of a finite field F. It was shown that multiple-access codes for such G-adder channels can be studied and constructed in a framework that is akin to the algebraic theory of error control codes. Two simple procedures to construct multiple-access codes with desirable properties via maximum distance separable codes were given. A G-adder channel does not arise naturally. It can be created on a local area network by means of "smart" nodes that add information symbols according to the arithmetic in G. A stronger motivation for the study or G-adder channels came from step two. Step 2: It has been shown that it is possible to decompose the Gaussian multiple-access channel into a number of independent G-adder channels provided that each such channel is then used to transmit multiple-access codewords over G considered in step one. The decomposition is obtained via T "modulators" (one for each channel input node) and a "demodulator." The modulator outputs are lattice-type signal-space codewords for the Gaussian channel. *** Compared to spread spectrum (the common practice) the codes resulting from steps 1 and 2 above have the following advantages: (l) They are designed keeping in mind that interference and noise are two distinct problems that need different solutions. In particular, active users do not contribute to the noise level of other users; (2) Decoding is simple and algebraic; (3) There is no bandwidth expansion. in the sense that while taking care of the problem of assigning the channel to busy users. the codes allow transmission of the same amount of information that would be possible via time-division multiple-access (or frequency-division multiple-access). (4) They support transmission of several bits per dimension which is an important attribute for codes designed to operate in a bandlimited environment. (5) They are natural offspring of the powerful coding and shaping techniques that have revolutionized the design of signal-space codes for the (single-user) bandlimited Gaussian channel. (6) They have the properties that are needed for the codes assumed in recently proposed random-access protocols with multiple reception capability. These protocols can achieve throughputs arbitrarily close to 1.

9304763 Rimoldi 我们正在接近个人通信时代，这需要一个能够从地球表面（及上方）任何一点不受限制地访问全球网络的基础设施。该场景的实现需要通过无线网络进行有效的通信。无线网络的主要组成部分是高斯多址信道。 拟议研究的目的是扩展主要研究者的最新成果，从而开发出一种新的程序来构建该通道的代码。 以下两个步骤导致了拟议的程序。 步骤1 考虑一种称为G-adder 信道的更简单的信道模型，并研究该信道的多址编码。 与某个有限群 G 关联的 G 加法器通道的输入是 G 的元素，输出是输入的总和（在 G 上）。为了从更熟悉的基础开始，假设 G 是有限域 F 的加法群。结果表明，可以在类似于差错控制码代数理论的框架中研究和构造此类 G 加法器通道的多址码。给出了通过最大距离可分离码构造具有所需特性的多址码的两个简单过程。 G加法器通道并不是自然产生的。它可以通过“智能”节点在局域网上创建，这些节点根据 G 中的算术添加信息符号。研究或 G 加法器通道的更强烈动机来自第二步。 步骤2：已经表明，可以将高斯多址信道分解为多个独立的G加法器信道，前提是每个这样的信道然后用于在步骤一中考虑的G上传输多址码字。分解是通过 T 个“调制器”（每个通道输入节点一个）和一个“解调器”获得的。 调制器输出是高斯信道的点阵型信号空间码字。 *** 与扩频（常见做法）相比，上述步骤 1 和 2 产生的代码具有以下优点： (l) 设计它们时考虑到干扰和噪声是需要不同解决方案的两个不同问题。特别是，活跃用户不会影响其他用户的噪音水平； (2)解码简单、代数性强； (3)没有带宽扩展。从某种意义上说，同时解决了将信道分配给繁忙用户的问题。这些代码允许通过时分多址（或频分多址）传输相同数量的信息。 (4) 它们支持每个维度传输几个比特，这对于设计用于在带限环境中运行的代码来说是一个重要属性。 (5) 它们是强大的编码和整形技术的自然产物，这些技术彻底改变了（单用户）带限高斯信道的信号空间代码的设计。 (6) 它们具有最近提出的具有多重接收能力的随机接入协议中假设的代码所需的属性。这些协议可以实现任意接近 1 的吞吐量。