Analysis of packet radio networks using slotted protocols

The purpose of this research is to first develop access protocols with time slots for packet radio networks, and then to evaluate the network performance in single hop networks and multihop networks. For single hop networks, successful transmission probability and throughput are used as the performance measures. The access protocols developed for single hop networks are compared. For multihop networks, expected progress is used, and the optimal transmission range is obtained for each given network model. In networks using narrowband signaling, two new slotted protocols are proposed. Both methods take advantage of sensing capabilities by randomly delaying packet starting times. In one protocol, terminals have a capability to sense the carriers of other packets. In the other protocol, terminals can sense a busy tone emitted by a current receiver. These sensing capabilities apply to spread spectrum network systems in different forms. Because of the properties of spread signals, terminals can identify the number of transmissions and the spreading code used for transmission. Considering the advantages of these properties, two CSMA protocols and one BTMA protocol are proposed. Compared to an existing slotted protocol (ALOHA), these access protocols are analyzed in single hop networks. More significantly, the results for spread spectrum networks show that the capture capability possessed by spread spectrum greatly contributes to a performance enhancement. The formulas obtained here play important roles in analyses of multihop networks. In multihop networks, it is assumed that each terminal has a finite-length buffer forming a first-in first-out (FIFO) structure. The inability to receive a packet when a buffer is full has an obvious impact on network performance. Using a Markovian model to represent the buffer, the probability of a terminal having either a full or empty buffer is analyzed. In order to evaluate expected progress, a method is derived which is applicable to any multihop network using slotted protocols. The results for buffer analyses show that there is a certain optimal buffer size according to the given traffic. In order to maximize the expected progress, the optimal transmission range is given for each network model in terms of the number of terminals within range of one another.