Performance analysis and transmission strategies comparison for synchronous WDM passive star LANs

Two synchronous transmission strategies suitable for optical WDM networks of passive star topology are presented in this study. The fiber bandwidth is divided into parallel WDM channels: the control and the data channels, while the number of control channels is less than the number of data channels. In particular, the control channels are used for the control information exchange prior to the data packet transmission, aiming to avoid the data channel collisions. This is achieved by effectively exploiting the propagation delay latency as appropriate acknowledgment time. The first transmission strategy performs the data channel collisions avoidance by allowing only one station per cycle to transmit over a data channel, employing appropriate transmission rules, like in [12]. On the other hand, the second transmission strategy (Improved Protocol) assigns to each control channel a dedicated data channel to ensure that each successfully transmitted control packet corresponds to a successful data packet transmission. Thus, it requires less processing overhead as compared to the first one. The performance of both the WDMA strategies are analytically studied based on Markovian models for finite population, while the performance measures are derived by closed mathematical formulas. The protocol performance is extensively studied for various number of stations, control and data channels. Finally, the comparison of the two protocols proves that second one essentially improves the throughput, while this improvement is an increasing function of the number of control channels.