Study on the problem of routing, wavelength, and time-slot assignment towards optical time-slot switching technology

Conventional optical burst switching (OBS) is incapable of providing connection-oriented service, and burst loss is more likely to occur with increasing of traffic load due to its inherent architecture where the burst size is variable. In this paper, we propose and evaluate the optical time-slot switching technology, in which the fixed-size time-slot is adopted as the basic switching granularity, and switching is done in the time domain, rather than the wavelength domain. Also, we prove that time-slot switching has an equivalent function to eliminate data conflict relative to wavelength converter. Subsequently, the routing, wavelength, and time-slot assignment problem is studied in this paper. An adaptive weight function is introduced to the routing and wavelength selection algorithm, then several useful approaches, such as the train approach, wagon approach and p-distribution approach, are presented for time-slot assignment and scheduling. The results show that our scheme can perform better than conventional OBS in the aspect of blocking performance, quality of service, and class of service.