Performance analysis of channel access protocols in spread spectrum packet radio networks

Abstract

The use of spread spectrum signaling in packet radio networks was motivated largely by the desire to achieve good performance in the fading multipath channels resulting from the users in the mobile environment and by the need for secure communications in tactical applications. The spread spectrum signaling also enables simultaneous successful transmissions to take place within the same local area, which are not generally possible in narrow-band networks. If a packet transmission is to be successful in the presence of other ongoing transmissions, the destination receiver of a transmitted packet should be leady for packet reception and lock onto the packet successfully, and then accomplish the reception of the packet rejecting the interference due to the other transmissins as noese. In other words, we can say that the success of a packet transmission is determined by the receiver availability and the effect of the multivser interference. In this thesis, we model and incorporate these two factors in the performance analysis of spread specctrum packet radio networks. In addition, we propose the channel access protocols which regulate these two factors properly so as to enhance the network performance. Firstly, we analyze the performance of an unslotted network. We account for the receiver availability through a Markovian network model and the preamble collision probability, and make a simple threshold approximation to the effect of the multiuser inerference. Secondly, we consider a slotted network. We derive a detailed model for the channel with the frequency hopping modulation, which accounts for both the receiver avalability and the effect of the multiuser interference. Then, the channel model is incorporated in a Markovian network model for the performance analysis of the network. We also evaluate the asymptotic performance of the slotted network as the number of nodes and the codeword length approach infinity, and derive the optimal retransmission probability f...