Baoli Zhang et al, 2009 : In this paper, problems in estimating location of randomly deployed sensor nodes are tackled with the help of directional antennas. High accuracy, energy efficient, and low cost localization scheme is proposed using a mobile anchor node equipped with a directional antenna and a global positioning system receiver which automatically resolves the problem of hidden terminal and deafness. In antenna model, Border line intersection localization scheme is used in which omni directional antenna is used by sensor node to receive beacon messages from mobile anchor node and directional antenna is used by mobile anchor node to transmit beacon messages. After the network model, communication model is proposed in which directional ' omni directional communication is shown. Location determination is done with the help of timestamp and coordinates of anchor node along with the boundary lines of angle of transmission. Error analysis and correction is done with the help of neighbouring nodes and using the short distance movement pattern for the anchor node. Simulation results are compared with Yu's and Ssu's localization algorithm. In border line interaction algorithm less number of beacons are used which shows the higher accuracy and high energy efficiency. Throughput is increased and time delay decreased for the location estimation of the sensor nodes.
Hong-Ning Dai, 2009 : Paper considers the possibility of using directional antenna in Wireless sensor network. It prepare models for the antenna, propagation and interference which will be used to find the output. Each node is able to randomly choose its destination. For the network to be connected Torus Division is used in which plane is divided into even sized squares. Routing mechanism is used that chooses a route with the shortest distance. For collision free transmission time division multiple access technique is used in which a second is divided into number of cell slots and only one transmission/reception is done during each cell slot. Each cell slot is further divided into mini-slot which is used in scheduling the source to destination hopping. Considering these parameters average throughput and delay is calculated and is compared with the results of Omni-directional antenna. Comparison concludes that the use of directional antenna with time division multiple access technique improves the network throughput capacity and reduces the multihop transmission delay. It further shows that the directional antennas improved the transmission range and the interference is reduced significantly.
Nuraj Pradhan et al, 2011 : An energy efficient Distributed Power Management algorithm with Directional Antenna is proposed in this paper. Algorithm adaptively manages the node power and provides a strongly connected network in a dynamic topology. After defining the system model, problem formulation is done in which main focus was on maintaining the connectivity with least power consumption. Dependence of node connectivity on node density and transmit power is also shown in the paper. In proposed algorithm, creation of bi-directinal link is shown alongwith power management and reduced interference. Simulation parameter like power, delay, routing protocol, packet size, path loss(between 2.7 and 3.5) and environment are defined and the results are compared with COMPOW (commom power) algorithm. Result shows that the distributed power algorithm so proposed have 31.60% increase in network throughput, 73.70% reduction in average transmit power per antenna and 89.22% reduction in average interference level in comparison to COMPOW. Further no nodes in the network is left isolated as it was 2% in case of common power algorithm.
K. Vinod Kumar et al, 2011 : In this paper, a new time division multiple access based MAC protocol is introduced which can be used in mobile wireless sensor network. Objective is to fairly and effectively share the resources between all the sensor nodes. Different Mac protocols such as SMAC, EMAC, TRAM and mobile TDMA are discussed. Problem formulation has been done in which time delay and poor channel utilization problems are taken into considerations. Proposed algorithm along with some assumptions uses the FLOC algorithm for clustering the nodes. In proposed algorithm time is divided into frames and frames are sub divided into time slots. Time slots are splitted into three sections : first is communication request in which slot allotted node receive the request for slot from other nodes who wants to transmit the data. Secondly, channel allocation in which node decides whether to allot the channel or not depending upon the priority index of the node. Thirdly, packets are transmitted or received in the data section. After the simulation, results are compared with the traditional TDMA for static network and mobile TDMA for mobile network. In static network, it is shown that the proposed algorithm gives lesser delay compared to traditional TDMA and the network lifetime is approximately 30% more. In mobile network, good channel utilization was proved for incoming and outgoing node clusters against the mobile TDMA.
Hassan A. Ahmed et al, 2013 : A method is proposed to mitigate the effect of Doppler
shift in MMR system ( mobile multihop relaying system ) using directional antennas. It includes the possibility of deploying directional antennas at both the mobile satation and relay station sides in MMR. Objective is to decrease the bit error rate with the help of directional antenna. System model is proposed with taking two hopes as a reference in a multi hop environment keeping in view the Doppler shift effect of the mobile node. Doppler shift effects are calculated using direction antenna at relay station and secondly at both the relay station and mobile station. Analysis and simulation is done using the proposed approach for orientation, speed of mobile station and beam width of the directional antenna employed. The parallel orientation case provides the better bit error ratio as compared to the perpendicular orientation of the antenna. Significant BER enhancement is observed at low and high mobile station speeds. Further, it is shown that effect of inter carrier interference due to Doppler shift is reduced leading to enhanced bit error ratio performance of the system.
Zuopeng Zhao, 2012 : Time - delay simulation is performed with respect to the hops and hop spacing, Mac dormancy mechanism, back-off time and transmitted power, and relation between them are obtained. System model is prepared using the channel delay, transmission delay and number of required transmission to successfully transmit the data packets. Simulation of time delay is shown with respect to the hop number, as the number of hopes increases the time delay also increases. Then the experiment is performed with respect to different hops and jump distance, which shows that time delay is nearly equal for 3 hop but for 4 and more hops the time delay increases significantly. Next, time delay is compared with and without the sleep mechanism and it is shown that time delay is reduced significantly. On comparing the transmitting power with the time delay shows that adding the transmit power is the effective method to control communication delays. Hence it is concluded that by improving routing protocol, sleep mechanism, reasonable back-off time, number of nodes and transmitting power we can control the communication delay.