卫星通信系统中的ALOHA技术

ALOHA Techniques for Satellite Communication Systems

文章在研究卫星系统中实现分组通信的短数据包纯ALOHA、扩频ALOHA方式和时隙ALOHA(SALOHA)多址接入方式,以及适合长数据包的预约ALOHA多址接入方式的基础上,介绍了防止S-ALOHA系统饱和与振荡的输入控制(ICP)、重发控制(RCP)和输入重发控制(IRCP)3种动态稳定控制策略。首先,针对3种策略都涉及到的积压终端数估计,文章提出了一种修正算法,并进行了仿真验证。在分组高到达率的情况下,该算法较于传统算法仍然能保证系统的小时延和吞吐率相应增加。其二,就无线信号分组被遮蔽但仍存在捕获效应的移动卫星通信场景,介绍了一种基于S-ALOHA的终端分组发送概率的动态稳定的计算算法,该算法利用捕获效应可以进一步改善陆地移动卫星通信系统性能。

This paper discusses the ALOHA multiple access technique of packet communication in satellite systems. General ALOHA methods are firstly introduced including the pure ALOHA,spread ALOHA and slotted ALOHA （ S-ALO-HA） suitable for short packets, and the reservation ALOHA for long packets. Then three dynamic stability control strate-gies,Input Control Procedure （ ICP） , Retransmission Control Procedure（ RCP） and Input Retransmission Control Procedure （ IRCP） , are given to prevent the saturation and oscillation of S-ALOHA systems. In order to implement the above control strategies,the receiving satellite needs to estimate the number of backlogged terminals in the system. A modified estimation algorithm for the number of backlogged terminals is presented and is validated by simulations. In addition,a Terminal-Pack-ets-Transmission-Probability computation algorithm, which is suitable to satellite communication scenarios with dodging effect, is introduced. This channel-sensitive, dynamically stabilized S-ALOHA algorithm can improve the performance of land-mobile satellite communication systems by applying captive effect.