Abstract-Transmission Control Protocol (TCP) is known to suffer from performance degradation in mobile wireless environments. This is because such environments are prone to packet losses due to high bit error rates and mobility induced disconnections. TCP interprets packet losses as an indication of congestion and inappropriately invokes congestion control mechanisms, leading to degraded performance.While there are several proposals to optimize TCP in the presence of high bit error rates and mobility, they focus mainly on scenarios where the TCP sender is a fixed host. In this paper we propose ATCP, an approach which mitigates the of degrading effect of host mobility on TCP performance for two-way data transfers, i.e. scenarios where the TCP sender is a mobile host, in addition to scenarios where the TCP sender is a fixed host.ATCP uses network layer feedback in terms of disconnection and connection signals, to modify the congestion control mechanisms of TCP, thereby achieving enhanced throughput in mobile wireless environments. We have compared ATCP with 3-dupacks (3DA) [10], Freeze TCP [4] and TCP Reno, by simulations using ns-2. We show that ATCP achieves an improvement of up to 40% over TCP Reno in WLAN environments and up to 150% in WWAN environments in both directions of data transfer.

In recent years, Wireless S ensor Networks (WS Ns) have gained much attention because of its varying applications from catastrophic region to industrial and household region. In few applications, sensors are deployed in extreme environmental conditions. Hence, node access is not possible in that scenario. Therefore, a large number of sensor nodes are deployed in the target field so that node replacement problem is eliminated. Also, coverage is a very important parameter because it measures how effectively a target field is monitored by the sensor network. This paper focuses on the coverage issue in wireless sensor networks. Initially, three different types of coverage issues are discussed. Then, full coverage issue is examined by considering different points such as node type, deployment type, relation of communication range to sensing range, strategy used to detect full coverage and positioning based/independent algorithms. S ome applications of wireless sensor networks are given. Finally, research challenges in the field of area coverage are discussed.

Abstract-Transmission Control Protocol (TCP) is known to suffer from performance degradation in mobile wireless environments. This is because such environments are prone to packet losses due to high bit error rates and mobility induced disconnections. TCP interprets packet losses as an indication of congestion and inappropriately invokes congestion control mechanisms, leading to degraded performance.While there are several proposals to optimize TCP in the presence of high bit error rates and mobility, they focus mainly on scenarios where the TCP sender is a fixed host. In this paper we propose ATCP, an approach which mitigates the of degrading effect of host mobility on TCP performance for two-way data transfers, i.e. scenarios where the TCP sender is a mobile host, in addition to scenarios where the TCP sender is a fixed host.ATCP uses network layer feedback in terms of disconnection and connection signals, to modify the congestion control mechanisms of TCP, thereby achieving enhanced throughput in mobile wireless environments. We have compared ATCP with 3-dupacks (3DA) [10], Freeze TCP [4] and TCP Reno, by simulations using ns-2. We show that ATCP achieves an improvement of up to 40% over TCP Reno in WLAN environments and up to 150% in WWAN environments in both directions of data transfer.

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