Impact of BER in fragmentation-aware routing and spectrum assignment in elastic optical networks

Abstract

Routing and spectrum assignment (RSA) in elastic optical network (EON) is a challenging task as an inefficient RSA may result in spectral and spatial fragmentation, leading to under-utilization of spectrum and increased connection blocking. Previous fragmentation-aware RSA algorithms, based on the assumption of an ideal physical layer, are not suitable for the performance evaluation of practical networks, where quality of the optical signal degrades while travelling long distances through the optical fiber links. Therefore, while running a RSA algorithm, it is necessary to consider the impact of all noise components to evaluate receiver bit-error rate (BER) on the fly, so that each connection is setup only when the estimated BER remains below an acceptable limit. This problem, hitherto unexplored in EONs though more significant and complex as compared to the conventional optical networks, is taken into consideration in this paper while framing fragmentation-aware RSA algorithm. In particular, we present a novel BER-cum-fragmentation-aware RSA algorithm, by using online estimates of BER values while executing fragmentation-aware RSA. The simulation results show that awareness of BER increases the connection blocking, which can however be addressed favorably by increasing transmit power, as much as possible from the available transmitter modules. Finally, we present a histogram of number of established connections versus delay-bandwidth product of the connections, leading to an assessment of the proposed algorithm in respect of the ability to allow long-haul connections with large bandwidth requests.