Papers by Keyword: NS2

Abstract: By studying multicast routing algorithm for MANET, this paper proposes a new heuristic algorithm to improve MAODV performance. Algorithm calculate the cost function under the delay constraint conditions, dynamically adjust the leader node, thus reducing crowded areas produce, for MAODV provide Qos. Simulation results show that when the expansion of the network, this algorithm has less routing overhead, high efficiency.

Abstract: This paper analyzed wireless sensor network simulation technology. We discussed the principles of wireless sensor network simulation based on NS2 and constructed a visual simulation model for wireless sensor networks. By adding NS2 protocol and setting the sensor nodes and some simple parameters, the system presented the running process and the performance of the network in the form of animation and graphics. The results show that this method simplifies the process of simulation of wireless sensor networks, and improves the efficiency of wireless sensor networks research and development, which provides support for the development of application-oriented networking of wireless sensor networks.

Abstract: The throughput of traditional TCP degrades drastically in high speed satellite links, where the characteristics of long round trip time (RTT) and high bit error rate (BER) happen together. Two typical improved algorithms, Hybla and Westwood, are designed to solve the problems of long RTT and high BER respectively. TCP-HW which combines the advantages of Hybla and Westwood is proposed in this paper, on the basis of consideration of both long RTT and high BER. At slow start and congestion avoidance phase, TCP-HW adopts a radical congestion window (cwnd) growth policy to eliminate the low data transmission rate bring by long RTT as Hybla does. At fast retransmit and fast recover phase, TCP-HW updates the cwnd according to the estimated available bandwidth in Westwood to avoid the frequently unnecessary reduction of cwnd due to high BER. There, the cwnd can be kept large enough to achieve high throughput. Simulation results in NS2 indicate that the change of RTT and packet error rate (PER) has little impact on TCP-HW and the bandwidth utilization of TCP-HW can reach more than fifty percent in the 1Gbps GEO satellite link with 500ms RTT and 0.001 PER. In addition, TCP-HW still have good fairness.

Abstract: VANETs is a rapid developed wireless mobile MANETs network with special challenge nature. It is a distributed and self-organized communication network based on moving vehicle. This network has characteristics like limited bandwidth, strong mobility, strong dynamic network topology, limited node degrees freedom, equipment capacity constraints and weak physical security. These characteristics usually make typical routing protocol in mobile MANET show a low efficiency in mobile VANETs, even fail. MANET routing algorithm is roughly divided into two categories, namely table driven routing protocol and on-demand routing protocol. It is due to the particularity of driving cars on the road. So how to improve network routing protocol in the performance is now a challenging problem. The purpose of this article studies network routing mechanism based on wireless vehicular networks simulation method. On the basis of analyzing the performance of typical routing protocols in MANET, such as DSDV, AODV and DSR, the improved scheme of AODV on-demand routing algorithm is put forward.

Abstract: Given a scenario of Vehicle Ad hoc Network (VANET), this paper presented a GIS-Based routing (GBR) strategy to resolve frequent reconstruction caused by rapid topology changes. Due to the use of road information based on GIS, the protocol can evade permanent or temporary topology holes respectively which frequently occurred in the city scenario. Simulation results showed new routing protocols could achieve better performance in packet delivery ratio and proved GBR’s lower routing overhead, as well as it is better performances in high mobility, compared with DSR in urban vehicle environment.

Abstract: Mobile Ad Hoc network is a self-composing network with a highly dynamic network topology. Although it has many advantages, there are still some safety problems in it. One of these problems is the black hole attack. The black hole attack is a typical attack to the Ad Hoc network and is also the main threat facing it. In this paper, the safety problems exist in the AODV protocol, which is a kind of routing protocol in the Ad Hoc, has been analyzed in detail. In the meanwhile, an improved Secure Ad Hoc On-Demand Distance Vector Routing called OSAODV has been proposed and realized based on the NS2. Finally, three set of experiments have been made, the results have shown that the OSADOV can avoid the black hole attack very well.

Abstract: WSN is the network which is used mostly in the world nowadays, and it has the characteristics that lower cost and better functions than other kinds of the network, and the WSN network is built by the ordinary nodes and the super nodes.Theoretical study of the complex network is widely involved in the fields of computer networks, and the applied research becomes more and more important in the future. It has caused many academic attention about how to apply the complex network theory among the specific application in recent years. In the complex network theory, there has been a number of important research results about the use of the small-world network, scale-free network in the field of transportation.

Abstract: To overcome the insufficient of Sliding Window Non-parameter Cumulation Sum (SWN-CUSUM) algorithm, a Threshold-based K-means (TK-means) algorithm was presented to detect the selfish behaviors in an IEEE 802.15.4 Wireless Sensor Network (WSN).By judging the threshold and tracing the statistics characteristic of the average delay and the average throughput from each link, a node can determine if there is a selfish behavior and distinguish selfish nodes from normal nodes in the WSN. In the TK-means detection mechanism, when the threshold is lower than zero, it is judged that selfish behavior happens in network; In the presence of selfish behaviors, the data set is divided into K groups composed by a number of similar object, which have high similarity in the same groups and low similarity in different groups to distinguish normal nodes and selfish nodes. Simulation results from NS2 show that the TK-means algorithm can effectively detect the selfish behaviors generated by one selfish node or multiple selfish nodes in the WSN.

Abstract: TFRC protocol is very suitable for video transmission, while quality assessment is also essential in video transmission system. In this paper a real-time video transmission system based on TFRC protocol is proposed, and an evaluation model about the system is improved in the framework of Evalid. It assesses the quality and efficiency of the video transmission according to the actual video file, and analyzes losses frame in different video types during transmission as well as the picture quality in receiver. The results of simulation experiment in NS-2 show that when real-time video transmitted in complex network environment using this system, the receiver can get satisfactory video quality by reason of the TFRC protocol friendliness and the smoothness of sending rate.

Abstract: This paper analyzes the wireless local area network existing safety and efficiency problem. It put forward the VPN tunnel technology to solve these problems. Theory explains that it is very the advantages of layer second tunneling protocol in a wireless local area network. This technology is proved to be reliable by Network Simulate 2 tool. It is proved that the technique is the advantage of high efficiency and safety.