Performance analysis of frequency-hopped packet radio networks with side information generated from test symbols

Abstract

This paper is concerned with the performance analysis of frequency-hopped packet radio networks with erasure only decoding. Reliable side information are generated by inserting a special group of test symbols in each dwell. Although the primary use of test symbols is to insure reliable side information, it has the additional potential benefit of making data symbols capable of discriminating partial overlaps. Closed form expressions for packet capture probabilities are derived for random and one-coincidence hopping patterns. Numerical results indicate that, increasing the number of test symbols leads to a sigmficant improvement in the throughput at high traffic levels. L IntroductionIt is well known that the performance of frequencyhopped packet radio networks (FH-PRNs) is substantially improved when side information are provided [1]-[4]. The side information takes the form of a single binary decision about the presence or absence of interference in each dwell interval. One simple method for generating side information due to Pursley [1]-[3] is to insert a known sequence of test symbols in each dwell, and the number of test symbols that are received correctly determines the reliability of the data symbol(s). This method is used in [4] to assist the performance of networks protocols in multi hop FH-PRNs subjected to partial band interference. Although inserting non-data symbols in the dwell intervals tends to decrease the information rate (or alternatively increase the transmission rate), it has the positive effect of reducing the hit rate for the data symbols, by making the data symbols able to discriminate against some interfering packets. This is because some of the asynchronous interfering packets are seen as synchronous by the data symbols [6]. This effect is pictured out in Fig. 1. Here, packet 0 is the reference packet, and the other three are asynchronously interfering packets. However, due to the fact that data symbols do not occupy the whole dwell interval, packets 1 and 3 interfere synchronously with the data symbols of packet 0. Increasing the length of test symbols tends to improve the packet capture probability since the proportion of the interfering packets which hit the data symbols synchronously will be increased. In fact increasing the number of test symbols has the primary advantages of increasing the reliability of side information [11-[31.Fig. 1. Packet 0 and three interfering packets, with arrival times $1 < c4, CA < 50) < 1-c4 and 50) < l-cb. Test symbols are shown for the ith dwell on packet 0 only.Accommodating the additional non-data symbols in the packet must be compensated by one of the following actions 1. increasing the packet transmission time, or equivalently, increasing the transmission rate. 2. decreasing the number of information symbols per packet. 3. decreasing the number of redundant symbols.In this paper we pay attention to the calculation of exact packet capture probabilities, focusing on the capability of data symbols of discriminating against partial interference. The com...

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