Performance analysis of multiple-route packet combining scheme for real-time communications in wireless multihop networks

In real-time packet communications, packet retransmission is generally not used because it may produce undesired delays. In this case, however, packet errors caused by a channel may lead directly to a loss of transmitted information. Then it is necessary to employ a technique which can reduce the influence of packet errors. We propose to employ a multiple-route packet combining scheme in realtime communications on wireless multihop networks. The scheme, which we proposed previously (Nakagawa, N. et al., IEICE Commun. Soc. Conf., vol.B-5-119, p.496, 2003), can achieve diversity gain by combining multiple copies of the same packet that are transmitted along different routes. We analyze two characteristics of the proposed system. One is the average packet error probability, which is obtained as a function of the elapsed time after generating copied packet transmission requests. The other is the required time for achieving a required packet error probability. The results are evaluated from a quality of service (QoS) point of view. From numerical results, it is shown that for a given tolerable delay, there exists a number of multiple routes that minimizes the achievable average packet error probability. Moreover, if the number of multiple routes is selected appropriately, the required time for achieving a required packet error probability can be minimized.