A hybrid MAC protocol for a metro WDM network using multiple free spectral ranges of an arrayed-waveguide grating

In this paper, we report on a novel quality-of-service supporting reservation-based medium access control (MAC) protocol for a reliable, scalable, and cost-effective switchless wavelength division multiplexing network. The network is completely passive and is based on an arrayed-waveguide grating (AWG). Each node at the network periphery is equipped with one single fast tunable transceiver for data and one low-cost broadband light source which is spectrally sliced for broadcasting control information. Direct sequence spread spectrum techniques are used to enable simultaneous transmission of data and control. All wavelengths are used for data transmission and signaling is done in-band. Each node has global knowledge and schedules variable-size data packets on a deterministic first-come-first-served and first-fit basis guaranteeing fairness and completely avoiding channel and receiver collisions. The proposed protocol provides both packet and circuit switching and supports multicasting. The network efficiency is significantly increased by spatially reusing wavelengths and exploiting multiple free spectral ranges (FSRs) of the AWG. The analysis accounts for propagation delay and protocol processing time. Results show that using three FSRs instead of one significantly decreases the mean delay and improves the mean throughput by up to 88%, resulting in a normalized mean throughput of approximately 78%. The analytical results are verified by simulation. 2002 Elsevier Science B.V. All rights reserved.