Adaptive Scheduling in Ad Hoc and Cellular Wireless Networks
Next generation 4G LTE-Enhanced wireless cellular networks are designed to provide broadband high speed transport services to mobile users. Due to the scarcity of spectral resources that can be employed, it is essential for the networks to engage in multi-dimensional adaptations in the dynamic assignment of wireless access resources. The robustness of wireless cellular networks is also of importance, since failures or degradations of network elements inevitably lead to major network service disruptions. Thus, efficient failover mechanisms are required to handle this scenario.
This dissertation introduces efficient adaptive scheduling algorithms for multicast and unicast downlink transmission operations in cellular wireless networks. Under multicast operations, the newly developed adaptive power scheduling algorithms enable base stations to coordinate, on a spatial-TDMA basis, the transmission of multicast packets to identified mobile users. This joint scheduling and power control problem is shown to be representable as a mixed-integer linear programming model, which is NP-hard. Consequently, heuristic algorithms of polynomial complexity are developed for solving the problem in a practical manner. These algorithms are shown to yield excellent throughput rate performance behavior, and to lower communications energy consumption levels. Under unicast networking operations, we introduce dynamic scheduling algorithms that allow busy base stations to make use of resources that remain under-utilized by lightly loaded neighboring base stations. Such a dynamically employed resource sharing mechanism is shown to provide significant enhancement to the system throughput capacity. Furthermore, the algorithms exhibit efficient performance behavior under failover scenarios.
We also study multicast networking in wireless ad hoc networks. We consider an energy-aware mobile backbone network architecture under which certain nodes are dynamically elected to act as backbone nodes. Each backbone node manages the wireless access network that it controls, providing for the transport of messages from/to mobile clients and the Bnet. We introduce the concept of performing multicast packet distributions among the mobile ad hoc wireless network nodes using a hybrid multicast protocol. We show that the hierarchical Bnet based hybrid multicast architecture leads to efficient system performance behavior under different operational scenarios examined.