For IEEE 802.11 wireless LANs (WLAN) with multiple access points (AP), it is critical to allocate the limited number of radio channels dynamically and efficiently. In this paper, we present a new radio channel allocation (RCA) scheme for WLANs with multiple data rates. First, we propose a new algorithm to dynamically estimate the number of active stations by using the least square estimator (LSE), which is unbiased and has minimum variance. Second, we derive an expression to evaluate the impact of the co-channel stations of an AP on the channel utilization of the AP based on the number of equivalent co-channel stations, which is the difference between the numbers of stations that are sensed by and associated with the AP. Third, we develop a new distributed RCA (DRCA) that considers the changing number of active stations, the impact of co-channel interference (CCI), and different traffic demands for different APs, which have not been considered by the existing RCA schemes. Simulation results have demonstrated that DRCA quickly finds optimal or suboptimal channel assignments and improves overall channel utilization for about 15 ~ 50% for different AP layouts, as compared to the existing schemes.

For IEEE 802.11 wireless LANs (WLAN) with multiple access points (AP), it is critical to allocate the limited number of radio channels dynamically and efficiently. This paper proposes a new framework for radio channel allocation (RCA) strategy for WLAN APs with power control capabilities. First, we formulate the RCA as a min-max optimization problem regarding channel utilization with constraints of data rate, channel quality, and transmission power. Second, we derive an expression to evaluate the channel utilization, which incorporates the condition of wireless channel, such as signal-to-noise (SNR) ratio and transmission power, in addition to the transmitting probability of a station. Third, we propose a new RCA algorithm that considers both link adaptation and power control mechanisms, in addition to the impact of co-channel interference (CCI) and multiple data rates, which have not been considered by the existing RCA schemes. Simulation results have demonstrated the effectiveness of the proposed strategy.

In the development of various large-scale sensor systems, a particularly challenging problem is how to dynamically organize the sensors into a wireless communication network and route sensed information from the field sensors to a remote base station. This paper presents a new energy-efficient dynamic clustering technique for large-scale sensor networks. By monitoring the received signal power from its neighboring nodes, each node estimates the number of active nodes in realtime and computes its optimal probability of becoming a cluster head, so that the amount of energy spent in both intra- and inter-cluster communications can be minimized. Based on the clustered architecture, this paper also proposes a simple multihop routing algorithm that is designed to be both energy-efficient and power-aware, so as to prolong the network lifetime. The new clustering and routing algorithms scale well and converge fast for large-scale dynamic sensor networks, as shown by our extensive simulation results.

In the design of mobile ad hoc sensor networks, a particularly challenging problem is how to effectively route the information among field sensors to a collection station to meet network performance requirements by using minimum energy consumption. In this paper, we propose to adopt a twotier network architecture based on energy-efficient clustering technique. For the tier-2 network formed by the cluster heads, we develop a multihop routing algorithm, called energy-efficient path availability routing (EEPAR). In the new routing algorithm, the parameters for node mobility and energy consumption are incorporated into routing metrics, including link availability, energy-efficiency, and power-awareness. The extensive simulation results have demonstrated that EEPAR improves network performance in link connectivity, delivery ratio, and node lifetime without sacrificing throughput. as compared to existing routing algorithms.

In this paper, we propose a new energy-efficient routing algorithm for mobile ad hoc sensor networks. The network architecture is based on a two-tier energy-efficient clustering scheme. The number of active nodes is estimated in real-time based on signal power a node received from others. Each node tries to become a cluster head (CH) in an optimal probability that minimizes the total clustering energy consumption. For the multihop routing domain formed by the CHs, we propose a new routing algorithm, that is, path availability routing in sensors (PARIS), by incorporating the availability of mobile links into routing metrics, in addition to energy consumption metrics, to establish multihop routes between a source node and a sink node. It has been shown that the routing algorithm is not only energy-efficient but also avoids link breakages in moderate to high mobility scenarios, while the existing ad hoc routing algorithms fail to maintain the links. Compared to the existing routing algorithms, the proposed routing algorithm is more energy efficient and has 40 ~ 60% less link breakages, therefore significantly increases route reliability and extends network lifetime