Routing and time slot assignment in PLC access networks

In this work, we address the Routing and Time slot Assignment (R&TA) problem in multi-hop PLC access networks. In our system, time is divided into fixed sized TDM cycles. Each cycle comprises a semi-dynamic bandwidth allocation period (SBAP) and a dynamic bandwidth allocation period (DBAP). The SBAP is used to provide each PLC CPE fixed bandwidth for providing bandwidth guaranteed services. It´s a persistent bandwidth provisioning. The bandwidth of DBAP is shared by all of the nodes. This bandwidth is dynamically allocated to each node by a per cycle basis. We take spatial reuse and rate adaption into account. Our design also takes channel quality into consideration in determining the optimal multi-hop routing. We formulate the R&TA problem for the SBAP as an ILP model in which the objective function is to minimize the total bandwidth usage for supporting all bandwidth sensitive services in the network. Since this problem is an NP-hard problem, in order to reduce the computation time, we have developed a Lagrangean relaxation (LR) based algorithm to resolve the problem. For the DBAP part, we propose a token-based scheduling algorithm. Numerical results reveal that the proposed LR algorithm can obtain a near optimal solution in short computation time. For the DBAP part, the proposed token-based scheduling algorithm can provide high throughput especially it can provide excellent fairness for bandwidth sharing among all nodes.