Orthogonal Frequency Division Multiple Access (OFDMA) is an emerging multiple access technology. In this paper, we consider OFDMA in the context of fixed wireless networks. This paper addresses the problem of assigning subcarriers and bits to point-to-point wireless links in the presence of cochannel interference and Rayleigh fading. The objective is to minimize the total transmitted power over the entire network while satisfying the data rate requirement of each link. We formulate this problem as a constrained optimization problem and present centralized algorithms. The simulation results show that our approach results in an efficient assignment of subcarriers and transmitter power levels in terms of the energy required for transmitting each bit of information. However, centralized algorithms require knowledge of the entire network topology and channel characteristics of every link. In a practical scenario, that would not be the situation and there is a need for distributed rate allocation algorithms. To address this need, we also present a distributed algorithm for allocating subcarriers and bits in order to satisfy the rate requirements of the links.

This paper addresses the problem of joint scheduling, power control and rate control while maximizing end-to-end data rates in multi-hop wireless networks. Using a "physical layer" network model that explicitly takes into account interference due to spatial spectrum reuse, we formulate the throughput maximization problem as a mixed integer linear programming problem (MILP). While a MILP based approach yields an optimal solution, it does not scale well to large networks. To address this issue, we also present a computationally efficient water-filling based heuristic. Simulation results, obtained using our heuristic, highlight several capacity related tradeoffs that arise in wireless ad-hoc networks. Prior work only provides either asymptotic results on ad-hoc network capacity or, at best, techniques for computing loose upper bounds for throughput in specific instances of networks.

Orthogonal frequency division multiple access (OFDMA) is an emerging multiple access technology. We consider OFDMA in the context of fixed wireless ad hoc networks. We address the problem of assigning subcarriers and bits to point-to-point wireless links in the presence of cochannel interference and Rayleigh fading. The objective is to minimize the total transmitted power over the entire network while satisfying the data rate requirement of each link. We formulate this problem as a constrained optimization problem and present a heuristic algorithm. The simulation results show that our algorithm results in an efficient assignment of subcarriers and transmitter power levels in terms of the energy required for transmitting each bit of information.

Sensor networks consist of autonomous wireless sensor nodes that are networked together in an ad hoc fashion. The tiny nodes are equipped with substantial processing capabilities, enabling them to combine and compress their sensor data. The aim is to limit the amount of network traffic, and as such conserve the nodes' limited battery energy. However, due to the small packet payload, the MAC header is a significant, and energy-costly, overhead. To remedy this, we propose a novel scheme for a MAC address assignment. The two key features which make our approach unique are the exploitation of spatial address reuse and an encoded representation of the addresses in data packets. To assign the addresses, we develop a purely distributed algorithm that relies solely on local message exchanges. Other salient features of our approach are the ability to handle unidirectional links and the excellent scalability of both the assignment algorithm and address representation. In typical scenarios, the MAC overhead is reduced by a factor of three compared to existing approaches.

In wireless sensor networks, the vast majority of wide-scale traffic consists of only a few bytes, including all network and application layer IDs. Therefore, MAC addresses, which are vital in a shared medium, present major overhead, particularly because they are traditionally chosen network-wide unique. To tackle this overhead, we propose a dynamic MAC addressing scheme based on a distributed algorithm. The assigned addresses are reused spatially and represented by variable length codewords. Our scheme scales very well with the network size, rendering it well suited for sensor networks with thousands or millions of nodes