Current Issue : October - December Volume : 2013 Issue Number : 4 Articles : 4 Articles
RFID have continued to suffer the Reader Collision Problem (RCP). A situation where the RF\r\ninterference wave from a particular Reader distorts the communication between another\r\nReader and it�s neighboring Tags. RCP is common in RFID largely because most RFID\r\napplications deploy large number of Readers. Carrier Sense Multiple Access with Collision\r\nAvoidance (CSMA/CA) has been used by many researchers as a MAC algorithm in\r\naddressing RCP. CSMA/CA alone cannot effectively addressed RCP especially in Dense\r\nPassive type of RFID. In this paper, an improved collision avoidance algorithm is proposed\r\nby incorporating time slotting to CSMA/CA. An RFID network was modeled and simulated\r\nwith varying network load. The result of the simulation shows a throughput of over 960\r\nsuccessful tag reading per seconds with slotted CSMA/CA as against 730 successful tag\r\nreading per second for CSMA/CA and more importantly, a relatively stable probability of\r\nsuccessful tag querying value of 0.82 as against 0.61 obtained from CSMA/CA using a\r\nmaximum of thirty readers and with a simulation time of 180 seconds....
The eccentricity of a node in a graph is defined as the length of a longest shortest\r\npath starting at that node. The eccentricity distribution over all nodes is a relevant descriptive\r\nproperty of the graph, and its extreme values allow the derivation of measures such as the\r\nradius, diameter, center and periphery of the graph. This paper describes two new methods\r\nfor computing the eccentricity distribution of large graphs such as social networks, web\r\ngraphs, biological networks and routing networks.We first propose an exact algorithm based\r\non eccentricity lower and upper bounds, which achieves significant speedups compared to the\r\nstraightforward algorithm when computing both the extreme values of the distribution as well\r\nas the eccentricity distribution as a whole. The second algorithm that we describe is a hybrid\r\nstrategy that combines the exact approach with an efficient sampling technique in order to\r\nobtain an even larger speedup on the computation of the entire eccentricity distribution. We\r\nperform an extensive set of experiments on a number of large graphs in order to measure\r\nand compare the performance of our algorithms, and demonstrate how we can efficiently\r\ncompute the eccentricity distribution of various large real-world graphs....
The wide utilization of Wireless Sensor Networks (WSNs) is obstructed by the\r\nseverely limited energy constraints of the individual sensor nodes. This is the reason why a\r\nlarge part of the research in WSNs focuses on the development of energy efficient routing\r\nprotocols. In this paper, a new protocol called Equalized Cluster Head Election Routing\r\nProtocol (ECHERP), which pursues energy conservation through balanced clustering, is\r\nproposed. ECHERP models the network as a linear system and, using the Gaussian\r\nelimination algorithm, calculates the combinations of nodes that can be chosen as cluster\r\nheads in order to extend the network lifetime. The performance evaluation of ECHERP is\r\ncarried out through simulation tests, which evince the effectiveness of this protocol in\r\nterms of network energy efficiency when compared against other well-known protocols....
Network coding has shown a good potential for improving network throughput and, recently,\r\nhas been used in multimedia transmission over wireless networks. In addition to guaranteed\r\nthroughput, real-time multimedia transmission requires bounded delay, delay variation, and\r\npacket loss. This paper presents RTOC, a new XOR-based opportunistic network coding\r\narchitecture for real-time data transmission. RTOC is an application-independent architecture\r\nthat takes into consideration the characteristics of real-time traffic and provides an efficient\r\nframework to optimize multimedia application requirements such as bandwidth, delay, delay\r\nvariation, and loss. The performance of RTOC was evaluated using simulated video\r\nstreaming traffic. The results demonstrated that RTOC can improve the real-time performance\r\nmetrics such as the packet delivery ratio, end-to-end delay, jitter, and throughput by\r\nconsiderable margins....
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