In this paper, we study the dynamic wavelength assignment problem in waveband-switched (WBS) networks composed of wavelength-convertible multi-granular OXCs (MGOXCs). With the aim to minimize the extra port consumption and utilize wavelength converters in an efficient manner, we propose a heuristic wavelength assignment algorithm named Least Weighted Configuration Cost (LWCC). WAPG, an algorithm proposed in previous literature, is compared with LWCC in both blocking performance and converter utilization. Numerical results show that LWCC offers more benefit in waveband grouping, which results in significant improvement in terms of blocking probability.

In the paper, we study the wavelength assignment problem in waveband switching (WBS) networks, which is composed of multi-granular optical cross-connect (MG-OXCs) interconnected by fiber links. WBS networks with MG-OXCs can route traffic at multiple granularities at the same time; therefore, the complexity of switching fabrics can be efficiently reduced. Moreover, in order to relax the wavelength continuity constraint on lightpath establishments, each MG-OXC node is equipped with certain number of wavelength converters. Focusing on minimizing the extra port consumption and utilizing wavelength converters in an efficient manner, we propose a heuristic algorithm, named Least-Configuration with Bounded Conversion (LCBC), under the dynamic traffic environment. Simulation results show that our algorithm can achieve a considerable port saving and significant performance gain by a well-design cost function.

Among various signaling protocols designed for OBS networks, the most popular one is just-enough-time (JET) protocol. JET can utilize the network capacity efficiently and reduce end-to-end transmission delay effectively. However, it may suffer from an intrinsic deficiency -fairness problem. Fairness problem is a traditional problem existing in various kinds of networks. It not only results in a phenomenon that bursts with shorter hops are generally favored but also deteriorates the networks utilization. In this paper, we investigated this problem and proposed a fair channel scheduling algorithm as a solution. Generally speaking, there is usually a tradeoff between fairness and blocking performance. Hence, our objective is to keep balanced between the two conflicting metrics. It gives each burst a dynamic priority which is defined by several characteristics of the burst. When a contention occurs, the proposed scheme picks the preferable burst and drops the other one according to their priorities then. Simulation results show that our scheme can improve fairness without degrading dropping performance too much. In addition, it increases the effective link utilizations as well.

To accommodate the demands of quality of service (QoS) and multicast applications, a multicast QoS traffic-scheduling algorithm with tuning latency consideration in wavelength-division multiplexing star-coupled networks is provided in this paper. To furnish different levels of QoS, two classes of traffic are considered: constant bit rate and available bit rate (ABR). An effective bandwidth-normalization scheme for ABR traffic is also derived. We define the slot scanning problem in the connection-setup process as the maximum assignable slots (MAS) problem. We prove that the optimal solution of the MAS problem can be obtained in polynomial time. Owing to its high-order time complexity, we also propose two heuristics for the MAS problem. The performance of these strategies are evaluated and compared by simulations under different system parameters, such as number of wavelengths, traffic load, and tuning latency.

Generally speaking, buffer requirement is not vital for JET-based optical burst switching (OBS). However, if deflection routing is enabled, optical buffers are necessary to solve the insufficient offset time problem. Another solution, which can alleviate buffering, is to lengthen offset time in the beginning. As previous work indicated, a burst with extra offset time has higher priority than that without extra offset time and quality of service (QoS) can be accomplished in this way. Therefore, we investigate the performance of deflection routing in prioritized JET-based optical burst-switched networks. A queuing model is proposed to approximate loss probability. We also evaluate the impact of deflection routing in Arpanet-2 topology by simulation.

We investigate adaptive routing in wavelength-routed networks. Exploiting the concept of load balancing, we propose an adaptive routing strategy named weighted-shortest-cost-path (WSCP). The salient feature of WSCP is that it seeks the path that minimizes the resource cost while simultaneously maintaining the traffic load as balanced as possible. We compare the blocking probability and average hops of WSCP with those of the traditional shortest-cost-path (SCP) strategy, fixed routing, and alternate routing. The numerical results show that WSCP can enhance blocking performance and lengthen hop distances just a little. The improvement is more significant in denser networks or with more wavelengths. We also develop an analytical model to estimate blocking performance of WSCP.

To accommodate the demands of QoS and multicast applications, a multicast QoS traffic scheduling algorithm with tuning latency consideration in a WDM star-coupled network is provided in this paper. We define the slot scanning problem in the connection setup process as the maximum assignable slots (MAS) problem. We prove that the optimal solution of the MAS problem can be obtained in polynomial time. Owing to its high-order time-complexity, we also propose two heuristics for the MAS problem. The performance of these strategies is evaluated and compared by simulations under different system parameters, such as traffic load and tuning latency.

This paper concerns itself with the performance of deflection routing in optical burst-switched networks based on just-enough-time (JET) signaling. Generally speaking, buffer requirement is not vital for JET-based optical burst switching (OBS). However, if deflection routing is enabled, optical buffers are necessary to solve the insufficient offset time problem. A variant of priority queuing model is proposed to approximate burst loss probability and the results show that the model provides an accurate estimation. We also evaluate the performance of deflection routing in Arpanet-2 topology. Simulation results indicate that deflection routing evidently brings significant blocking performance gain, especially with fewer wavelengths and under lighter load. In addition, we notice that excessive deflection will cause longer end-to-end delay and reduce the blocking performance. Therefore, it is necessary to control the maximum allowed deflection occurrences of a burst.

This paper proposes a dynamic traffic scheduling algorithm in single-hop WDM/TDM networks with arbitrary tuning latencies to support guaranteed QoS. To furnish different levels of QoS, two classes of traffic are considered: constant bit rate (CBR) and available bit rate (ABR). An effective bandwidth normalization scheme for ABR traffic is also derived. By applying distinct normalization schemes to CBR and ABR traffic individually, the bandwidth can be allocated more accurately and meanwhile the QoS is also guaranteed. Two slot allocation policies are also suggested to allocate the time slots to connections. The performance of proposed algorithm is evaluated and compared by simulations under different system parameters, such as wavelength number, traffic load, and tuning latency.