Current Issue : April - June Volume : 2013 Issue Number : 2 Articles : 7 Articles
The explosions of Internet of Things industry have been bringing more and more smart devices (SDs) into business\r\nand people�s daily life. This creates new opportunities to build applications that better integrate real-time state of\r\nthe physical world and requires agility for the software to accommodate customers� requirements. Nevertheless,\r\ndevices are usually provided by different manufacturers, and applications are independently constructed based on\r\ntheir own infrastructures with little interoperability. Web of Things concept has enabled the interoperability\r\nbetween devices by RESTful web service in a light-weight way; however, it make less efforts to discuss how to\r\nintegrate devices into complex business environment. Service-Oriented Architecture and Business Process\r\nManagement approach are becoming applicable to embedded real-world devices and provide flexible service\r\ncomposition. However, it is based on WS-* web service specification which is too heavy and complex for devices\r\nand not compatible to RESTful style. In such situation, integrating device into business application with simplicity\r\nand providing agility composition of service based on device are significant challenges. We propose a web-based\r\ntwo-layered integration framework that enables SD to integrate with each other via light-weight interface and\r\nother back-end applications into agile business process. A real-life use case on elderly care is studied in detail\r\nbased on the framework....
Routing in MANETs is a challenging task because of dynamic nature of network topology and resource limitations. The Ad hoc On-demand Distance Vector (AODV) routing protocol is proposed for achieving dynamic, self-organizing and on-demand multi hop routing among mobile nodes in Mobile Ad hoc Networks (MANETs). In AODV, wireless links may be lost occasionally due to the nodes on the routing path being unreachable. For solving this issue, the AODV protocol provides a local repair mechanism that tries to find an alternative route to destination by broadcasting the RREQ message from the upstream node of the broken link. Although the local repair mechanism works with a specified Time to Live to limit the repair range of RREQ, large number of the broadcast RREQ messages result in extensive control messages and obvious power consumption for transmitting these broadcast messages. This paper proposes an improved routing protocol based on AODV for ad hoc network, which optimizes hello mechanism, local repair mechanism, and provides multi-backup pathways for the source node. Through network simulation, we show that new protocol can reduce network end-to-end delay and increase packet delivery ratio. Moreover, relative stability is another advantage of improved algorithm....
Multi-standard mobile devices are allowing users to enjoy higher data rates and ubiquitous connectivity. These\r\nadvances are achieved on the expense of higher energy consumption requirements due to the continuous\r\nconnectivity and the multiple active wireless interfaces. In this article, we use one advantage of the multiple\r\ninterfaces, namely short-range (SR) communications. Mobile terminals (MTs) use SR cooperative networking to take\r\nadvantage of the good channel quality of SR links to save energy in multi-standard MTs. In this cooperative\r\nnetwork, the combined energy of all MTs is treated as a pool of resources, which is used by all MTs in the\r\nnetwork. Towards this end, we propose using cooperation between MTs using SR technology to achieve energy\r\nsavings. We conduct a quantitative numerical analysis to show the energy saving gains that can be achieved. We\r\nderive the energy gains in different use cases, considering different combinations of technologies (WiFi-WiMedia,\r\nWiMAX-WiFi and WiFi-WiFi) and different channel conditions. We show that up to 80% energy savings can be\r\nachieved when using a combination of WiMedia as SR and WiFi as long-range technology, compared to using WiFi\r\nwithout cooperation. We also show that SR cooperation can be used to extend the lifetime of the whole network.\r\nIn such scenario, terminals, which are running out of battery or low in energy, can still relay their data through\r\nother MTs, even if this will result in a slight increase in the total consumption of all MTs. This way, source MTs with\r\nlow battery level benefit from the good condition of the SR channel, extending the lifetime of their batteries. The\r\nincrease in the energy consumption of the relays can hence be compensated by some kind of payment, which\r\nopens opportunities for new business models involving source MTs, relays and network operators....
Three-dimensional (3D) wireless sensor networks have attracted a lot of attention due to their great potential\r\nusages in both commercial and civilian applications, such as environmental data collection, pollution monitoring,\r\nspace exploration, disaster prevention, and tactical surveillance. Topology control in 3D sensor networks has been\r\nstudied recently, and different 3D geometric topologies were proposed to be the underlying network topologies\r\nto achieve the sparseness of the communication networks. However, most of these proposed 3D topologies\r\ncannot bound the maximum node degree, i.e., some nodes may need to maintain a large number of neighbors in\r\nthe constructed topologies, which is not energy efficient and may lead to large contention. In this article, we\r\nextend several existing 3D geometric topologies to a set of new 3D topologies with bounded node degree. We\r\nprovide both theoretical analysis and simulation evaluation on their power efficiency and node degree\r\ndistributions. Our simulation results over random 3D sensor networks confirm nice performances of these proposed\r\n3D topologies....
In this paper an overview of multiple input-multiple-output (MIMO) system is presented. Multiple antenna transmission technology or MIMO system can increase the overall system performance. With increasing popularity of multimedia communications, high data rate transmission is expected to be supported by cellular communication networks. The implementation of MIMO technology in wireless communication networks plays a major role in improving the quality of signal and multiplexing opportunities and in turn increasing data throughput. Multiple antennas can be used to accomplish a multiplexing gain, array gain, diversity gain, or an antenna gain for enhancing the bit rate and the error performance of system. MIMO can be considered as one of the several forms of smart antenna technology. MIMO offers significant increases in data throughput .Future wireless applications demands for high data rates and high link quality. MIMO systems can be treated as an emerging technology in the next generations of cellular communication networks and wireless local area networks....
Turbo codes play a very key role in making digital communications systems very efficient & at the same time very reliable. Turbo codes belong to powerful class of forward error correcting codes. They come very close to approaching the Shannon capacity limit on maximum achievable data transfer rate over a noisy channel. In turbo Codes iterative decoding mechanism is used. In matter of channel coding, upto the invention of turbo codes, 3.0 dB stood between what the theory promised and what real time systems were offering. In order to ensure the efficiency of the data transmission with high speed, we must ensure the excellent performance of decoding. There are two algorithms for decoding Turbo Codes Soft-output Viterbi algorithm and logarithmic-maximum a posteriori turbo decoding algorithm. Log Map algorithm is the extension of MAP algorithm operating in Log domain. MAP algorithm is very efficient but posses many difficulties because of necessity of non linear functions and high number of additions and multiplications. In this paper we focus on Bit Error Rate & Frame Error Rate performance of Turbo Codes in AWGN channel using code rate of ½ and BPSK modulation technique. Decoding is perfomed by using Log Map algorithm that avoids the approximation in Max Log Map algorithm. Simulation results are provided below which show that as SNR increases Bit & Frame Error rate decreases....
Since many range-free localization algorithms depend on only a few anchors and implicit range estimations, they\r\nproduce poor results. In this article, we propose a distributed range-free algorithm to improve localization accuracy\r\nby using one-hop neighbors as well as anchors. When an unknown node knows which nodes it can directly\r\ncommunicate with, but does not know how far they are exactly placed, the node should have a location having\r\nthe average distance to all neighbors since the location minimizes the sum of squares of hop distance errors. In\r\nthe proposed algorithm, each node initializes its location using the information of anchors and updates it based\r\non mass spring method and Kalman filtering with the location estimates of one-hop neighbors until the\r\nequilibrium is achieved. Subsequently, the network has the shape of isotropic graph with minimized variance of\r\nlinks between one-hop neighbors. We evaluate our algorithm and compare it with other range-free algorithms\r\nthrough simulations under varying node density, anchor ratio, and node deployment method....
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