The throughput of some wireless multiaccess systems
The throughput of some wireless multiaccess systems
复制标题
DOI：
10.1109/tit.2002.802629
复制
发表时间：
2002-10
期刊：
影响因子：
--
通讯作者：
Daniela Tuninetti;G. Caire
中科院分区：
文献类型：
--
作者：
Daniela Tuninetti;G. Caire
我们计算了具有无限多个非协调用户访问公共信道的数据通信的多址无线系统的吞吐量。信道受到块衰落的影响，并且信道状态对于接收器来说是完全已知的，但对于发射机来说是未知的。为了应对多址干扰(MAI)和衰落，用户使用错误接收的分组的重传。我们考虑具有分散(单用户)译码的未扩频和随机扩频(码分多址(CDMA))系统以及其中接收机采用联合多用户译码的系统。分析结果表明：(A)分组重传的非扩频系统性能优于常规检测的码分多址系统，但优于线性最小均方误差(MMSE)检测的码分多址系统。(B)对于所有基于单用户译码(SUD)的系统，存在阈值(E/SUB//N/SUO/)，低于该阈值，通过以消失率发送的每个维度的无限数量的用户来最大化吞吐量，超过该阈值，通过以非零速率发送的每个维度的有限平均用户数量来最大化吞吐量。此外，随着(E/SUB//N/SUB/)的增加，每个维度的最佳平均用户数趋于1。从这个意义上说，我们说优化后的系统是“自正交的”。(C)对于基于联合多用户译码的系统，简单的时隙ALOHA策略能够恢复由于高限(E/subb//N/subo/)的衰落而造成的吞吐量代价，而增量冗余(INR)策略能够恢复任意(E/subb//N/subo/)的衰落代价。
We compute the throughput of some multiaccess wireless systems for delay-tolerant data communications, characterized by an infinite population of uncoordinated users accessing a common channel. The channel is affected by block fading, and the channel state is perfectly known to the receiver but unknown to the transmitters. To cope with multiaccess interference (MAI) and fading, the users employ retransmission of erroneously received packets. We consider unspread and randomly spread (code-division multiple-access (CDMA)) systems with decentralized (single-user) decoding and a system where the receiver employs joint multiuser decoding. The following conclusions can be drawn from our analysis: (a) unspread systems with packet retransmission outperforms CDMA systems with conventional detection, but are outperformed by CDMA with linear minimum mean-square error (MMSE) detection. (b) For all systems based on single-user decoding (SUD), there exists a threshold value of (E/sub b//N/sub o/) below which the throughput is maximized by an infinite number of users per dimension transmitting at vanishing rate, and above which the throughput is maximized by a finite average number of users per dimension transmitting at nonvanishing rate. Moreover, as (E/sub b//N/sub o/) increases, the optimal average number of users per dimension tends to one. In this sense, we say that the optimized systems "self-orthogonalize." (c) For the system based on joint multiuser decoding, a simple slotted ALOHA strategy is able to recover the throughput penalty due to fading in the limit for high (E/sub b//N/sub o/), while an incremental redundancy (INR) strategy recovers the fading penalty for any (E/sub b//N/sub o/).