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Efficient medium access control (MAC) algorithms are needed for nodes to share a transmission medium and achieve a high throughput. A MAC algorithm schedules packet transmissions so as to that minimize the time taken to send the packets without collisions. In wireless ad hoc and sensor networks, a MAC algorithm must conserve energy as well as provide good throughput. Most existing MAC algorithms for wireless networks are designed to work well under low traffic rates. In this paper we propose a new distributed algorithm Ad-ATMA for wireless ad hoc and sensor networks under relatively high traffic rates. We demonstrate using simulations that Ad-ATMA outperforms the best existing algorithms designed for higher traffic rates in terms of packet delivery ratio and latency while consuming almost identical energy as them. [ABSTRACT FROM AUTHOR]

Abstract: The positioning of wireless nodes has been an active research area over the last decade. Many network positioning algorithms have been proposed to solve this problem. The vast majority assume that a fixed set of nodes (called seeds) have a mechanism to position themselves at all times (using GPS or other means). The other nodes estimate their positions based on positional information exchanged between nodes using wireless communication. The monetary cost of a GPS unit is decreasing so systems where most nodes are equipped with a GPS unit is foreseeable. A problem with this assumption is that the task of self-positioning via a GPS unit is expensive in terms of energy consumption which results in faster battery decay. In this paper, we assume that every node is capable of self-positioning but activates that module selectively. This allows for balancing the energy costs of self-positioning among all nodes and results in reduced positional error. We investigate several different strategies for governing the self-positioning module and report on their performance. [Copyright &y& Elsevier]

Abstract: Medium access control is a key problem in wireless ad hoc and sensor networks. An efficient medium access control algorithm allows nodes to share the wireless medium at a lower energy cost and achieve a higher throughput. Most existing medium access control techniques for wireless networks are designed to work well under low traffic rates. In this paper we propose a new medium access control algorithm AdAMAC for wireless ad hoc and sensor networks under relatively high traffic rates. We demonstrate using simulations that AdAMAC outperforms the best medium access control algorithms designed for higher traffic rates in terms of packet delivery ratio and latency and has a similar energy cost to them. [Copyright &y& Elsevier]

Abstract: Localization is defined as the problem of determining the geographical locations of nodes in a wireless ad hoc or sensor network. Networks typically have some nodes (called seeds) that know their locations (using GPS or other means). Other (non-seed) nodes compute their locations by exchanging messages with nodes within their radio range.Several algorithms have been proposed for localization in different scenarios. Algorithms have been designed for networks in which each node has ranging capabilities (i.e., can estimate distances to its neighbors). Other algorithms have been proposed for networks in which no node has such capabilities. Some algorithms only work when nodes are static. Some other algorithms are designed specifically for networks in which all nodes are mobile. In this paper we propose a range-based localization algorithm RMCB for wireless sensor networks. Our algorithm uses a small fraction of seeds. It also makes use of the received signal strength measurements that are available from the sensor hardware. Our algorithm works well when nodes are static or mobile. We demonstrate using empirical data from sensor hardware (Texas Instruments EZ 430-RF2500) and simulations that RMCB outperforms a very good range-free algorithm WMCL in terms of localization error and has a similar computational complexity to WMCL. [Copyright &y& Elsevier]