A mobile ad hoc network (MANET) facilitates mobile hosts to communicate with one another based on wireless infrastructure. There are no base stations in ad hoc networks and the mobile hosts act as routers for data packets. Since the mobile hosts in a MANET keep moving, topological changes take place frequently in the network. This cause routing information kept by the nodes to get outdated easily. Effective ways of getting updated routing information is needed. This problem becomes more complex in wireless networks, where bandwidth is limited. This paper proposes an improved dynamic source routing (DSR) algorithm as a solution to this problem. The proposed algorithm, the Improved Dynamic Source Routing (I-DSR), has a hybrid feature, combined proactive and reactive, that enables all the hosts to get updated changing topology information with a low cost in communication instead of enabling only a few hosts to get the information when there is a route request for a new moved destination. In anticipation of the need of a route request to the new moved destination by other hosts, the operations in the algorithm are designed to eliminate these needs for route request flooding and eventually generate a small number of control packets. Through simulations, we demonstrate that I-DSR gives better network performance than the well-known on-demanding routing protocol, Dynamic Source Routing (DSR) Protocol. As it is improved from DSR, it just needs a few modification on DSR and is easy to implement.
The paper discusses the network calculus and its application for streaming media transmission in packet switched networks. With more and more new services and applications deployed over the Internet, the demands for a new theory and tool have been required tremendously. Conventional queueing theory has some limitations and difficulties in its application for the new services over Internet, since conventional queuing theory is based on stochastic theory. In a simple word, queuing theory assume each packet are independent with each other and conventional network mainly cares about packets. However, such assumption is not suitable for streaming media applications in the Internet. Network calculus provides a new approach to analysis the queueing problem in packet switched networks, particularly it provides a better analysis tool for streaming media. The network calculus is a flow based analysis tool and it will be much helpful for the information integrity and the transmission continuity for the streaming media. The paper introduces the network calculus and researches its applications for streaming media transmission.
This paper analyzes the steady-state throughput of network coding nodes when data is transmitted based on the stop-and-wait automatic repeat request (SW-ARQ) scheme. The state transition of network coding nodes employing SW-ARQ is analyzed, which shows that the operations of network coding nodes can be modeled by a finite state machine. Therefore, the throughput expressions of network coding nodes can be derived based on the properties of finite state machines. Furthermore, the throughput performance of network coding nodes is investigated either by simulations or by evaluation of the expressions obtained. It can be shown that the simulation results converge closely to the numerical results and justify the effectiveness of our analytical expressions obtained.
Cognitive Radio (CR) is a new paradigm that enable nodes to exploit unoccupied frequency spectrum for transmissions. Cognitive Radio Networks (CRNs) have been proposed to enable wireless mesh networks to communicate via dynamic channels. Many existing research consider routing in static CRNs with relatively stable communication channel where the duration of the availability of the communication channel is much longer than the communication time. However, there is limited routing related research in dynamic CRNs where the average available duration of the communication channel can be much shorter than the communication time. To address this, we propose a cross-layer cognitive routing protocol, the Opportunistic Service Differentiation Routing Protocol (OSDRP) for the dynamic CRNs. OSDRP discovers the minimum delay - maximum stability route in CRNs by considering the availability of spectrum opportunity in addition to switching delay and queuing delay across primary user networks. In addition, service differentiation is achieved through a combination of transmit power control and opportunistic routing. Simulation results demonstrate that OSDRP can achieve much better performance in terms of lower delay compared to other existing routing protocols in various scenarios.
Transfering and switching equipments are the main parts of Base Station Controller(BSC).Their performance is one of the decisive factors that influence the Service Quality and Customer Contentment of the whole system.This article discusses the method and technology of the test of voice channel in CDMA BSC, including transfering test of 64K PCM voice data stream, transfering test of voice data packet, transfering test of the whole data of voice channel, Cross Fire test of the whole voice channel and the subjective evaluating test of voice channel.
With the rapid development of global positioning system, cellular networks and relative technologies, people can request location-based services (LBSs) from the service provider using a handheld device quickly and easily. This greatly facilitates people's life. However, it brings a lot of privacy leakage problems. To reduce it, many methods have been proposed. But, they still don't balance the intensity and efficiency of privacy protection very well. Based on distributed storage and the quadratic residual theorem, this paper proposes a LBS user privacy protection scheme with both security features and efficiency. The traditional encryption method, private information retrieval (PIR), will bring high communication cost and computing pressure on the server side. A distributed storage system architecture can greatly reduce network overhead and the risk that the server will identify the user's real location because requests can be answered by the caching proxies without arriving at the server. To enable encrypted requests to be answered correctly by the caching proxies without being known by proxies, we build an index table. Compared with the similar work, simulation results show that our scheme can effectively reduce user communication and server computing overhead.
The Industrial Internet of Things (IIoT) has found extensive applications in intelligent transportation. However, as the number of vehicles increases, the issue of traffic congestion becomes more prominent, emphasizing the need for accurate congestion propagation prediction to enhance traffic conditions. Current methods for predicting congestion propagation lack consideration for the influence of communication networks and do not incorporate the path characteristics of congestion propagation. Therefore, we propose a path-based congestion propagation model, UAU_SIS_Path, employing multigrain abstraction of traffic congestion and information propagation. Specifically, UAU_SIS_Path effectively captures the propagation dynamics of congestion in IIoT by leveraging the interaction of two-layer networks and the path propagation characteristics of traffic congestion. Subsequently, we validate the effectiveness of the UAU_SIS_Path model through theoretical analysis, establishing tight upper and lower bounds of the propagation threshold and elucidating the relationship between the propagation of congestion information in the information network and the diffusion of congestion in the road network. Finally, based on theoretical analysis, we examine the impact of our model on congestion control strategies, utilizing path replanning, and traffic restriction as congestion control strategies. Experimental results in simulated road network BA and real road networks of varying sizes (GC, TA, and As) demonstrate the stability and scalability of our model. In comparison to the traditional contact-based propagation model, our model achieves a reduction in congestion propagation rates of 58.2%, 66.9%, 32.6%, and 48.6%, respectively.
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