Fairness in orthogonal frequency-division multiplexing optical networks

Abstract

Orthogonal frequency-division multiplexing (OFDM) optical networks allow multiple subcarriers to be allocated so that both subwavelength and superwavelength traffic can be accommodated. The success of OFDM is based on routing and spectrum allocation, and fairness in this allocation is an important factor in guaranteeing customer satisfaction. In a traditional wavelength-division multiplexing network environment, the fairness is limited to individual source–destination pairs, and the blocking probabilities of calls requesting higher bandwidths are exponentially higher than those requesting lower bandwidths. We utilize here the fairness index to measure the fairness in allocating different calls in the network and investigate four fairness methods for resolving the fairness problem in OFDM: limited subcarrier reservation, limited waiting, limited number of alternate routes, and limited state blocking. We present simulation results obtained by assuming static routing and the first-fit frequency assignment. Limited subcarrier reservation and limited state blocking can substantially improve fairness with a minimum loss in the network gain.