• Journal of the Institute of Convergence Signal Processing
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• v.9 no.4
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• pp.313-320
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• 2008

The dynamic clustering technique has some problems regarding energy consumption. In the cluster configuration aspect the cluster structure must be modified every time the head nodes are re-selected resulting in high energy consumption. Also, there is excessive energy consumption when a cluster head node receives identical data from adjacent cluster sources nodes. This paper proposes a solution to the problems described above from the energy efficiency perspective. The round-robin cluster header(RRCH) technique, which fixes the initially structured cluster and sequentially selects duster head nodes, is suggested for solving the energy consumption problem regarding repetitive cluster construction. Furthermore, the issue of redundant data occurring at the cluster head node is dealt with by broadcasting metadata of the initially received data to prevent reception by a sensor node with identical data. A simulation experiment was performed to verify the validity of the proposed approach. The results of the simulation experiments were compared with the performances of two of the must widely used conventional techniques, the LEACH(Low Energy Adaptive Clustering Hierarchy) and HEED(Hybrid, Energy Efficient Distributed Clustering) algorithms, based on energy consumption, remaining energy for each node and uniform distribution. The evaluation confirmed that in terms of energy consumption, the technique proposed in this paper was 29.3% and 21.2% more efficient than LEACH and HEED, respectively.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.9 s.351
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• pp.165-174
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• 2006

In this paper, we propose a new contention window control algorithm to increase TCP performance in wireless multi-hop networks. The new contention window control algorithm is suggested to reduce the hidden and exposed terminal problems of wireless multi-hop networks. Most of packet drops in wireless multi-hop networks results from hidden and exposed terminal problems, not from collisions. However, in normal DCF algorithm a failed user increases its contention window exponentially, thus it reduces the success probability of fined nodes. This phenomenon causes burst data transmissions in a particular node that already was successful in packet transmission, because the success probability increases due to short contention window. However, other nodes that fail to transmit packet data until maximum retransmission attempts try to set up new routing path configuration in network layer, which cause TCP performance degradation and restrain seamless data transmission. To solve these problems, the proposed algorithm increases the number of back-of retransmissions to increase the success probability of MAC transmission, and fixes the contention window at a predetermined value. By using ns-2 simulation for the chain and grid topology, we show that the proposed algorithm enhances the TCP performance.