Collision-Free Packet Retransmission Protocol for Wireless CSMA Systems

Recently, wireless networks using ISM band have been attracting a lot of attention. In these systems using carrier sense multiple access with collision avoidance (CSMA/CA), the packet collision and recollision between hidden nodes occur frequently and drastically decrease the network (NW) capacity. In this paper, we propose a packet retransmission protocol to avoid the packet recollision in 1 hop many-to-one network, in which all nodes send their packets to an access point (AP). In our proposed retransmission protocol, hidden nodes whose first transmitted packet is lost control their retransmission timing autonomously to avoid recollision with each other by using time lag between the finish time of their first transmitted packet and the received time of a collision inform signal, which is sent by AP to inform nodes about packet collision. The NW capacity using the proposed retransmission protocol is evaluated by computer simulation. And it is shown that the maximum network capacity of our proposed method is about 1.7 times better than that of the conventional method.