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Wireless, Mobile and Multimedia Networks (ICWMMN 2008), IET 2nd International Conference on

Date 12-15 Oct. 2008

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Displaying Results 1 - 25 of 133
  • A merger weight-based synchronization algorithm for WiMedia MAC

    Page(s): 163 - 166
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (561 KB)  

    WiMeida MAC, coupled with physical layer based on UWB technology, is now widely applied in high data rate wireless personal area networks (WPANs). Because the transmission with the UWB technology is restricted to a short range, multiple piconets may exist in a network at the same time. We investigate problems related to beacon collisions and data communication disruptions when piconets interfere into each other due to changes in propagation environment, moving devices, or other effects. For the purpose of resolving this problem and minimizing the cost, we propose a merger weight-based synchronization algorithm. The performance of the algorithm is simulated and compared with coordinated merger of BPs scheme provided in WiMedia MAC, and results show that there is room for further improvement over the current synchronization algorithm in WiMedia MAC. View full abstract»

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  • Improving upper bound on the capacity of planar wireless networks with omnidirectional antennas

    Page(s): 191 - 194
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (807 KB)  

    In this paper, we improve the upper bounds on the maximum number of simultaneously successful wireless transmissions and the maximum achievable per-node end-to-end throughput under the same general network scenario as in Arpacioglu and Haas (2004) [1]. View full abstract»

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  • An energy efficient routing protocol based on cluster head forecasting and power controlling

    Page(s): 187 - 190
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (613 KB)  

    Due to the constrained energy of nodes without supply in wireless sensor networks, how to reduce energy consumption of nodes becomes the important target of routing protocols. An energy efficient routing protocol based on cluster head forecasting and power controlling (CHFPC) was proposed. In CHFPC, cluster head is forecasted based on both energy and distance parameters, and power controlling is introduced in cluster routing and data transmission in order to reduce energy consumption of nodes. Finally, the performances of the CHFPC algorithm are simulated with OMNeT++ platform. The results indicate that the energy efficient performance of proposed scheme is better than LEACH, the lifetime and residual energy of wireless sensor networks are improved by 23% and 15%. View full abstract»

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  • A CDMA-assisted seamless handover scheme for WLAN

    Page(s): 183 - 186
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (694 KB)  

    With the development of WLAN (Wireless Local Area Network) technologies, many hotspots have been deployed and mobile devices can get Internet services through WLAN in many places. Some schemes based on the RSS (Receive Signal Strength) have been proposed to provide the seamless handover between WLANs. However, they can not avoid the ping-pong effect, and the handover performance is always influenced, especially when the handover is performed between adjacent cells which are not overlapping with each other very well. So in this paper, we propose a CDMA-assisted handover scheme (CAHO) for WLAN, which uses the CDMA connection during the handover. To evaluate the performance of CAHO, we set up a test-bed and compare it with other schemes. The experimental results show that the CAHO can reduce disruptions and lost packets. Furthermore, it can avoid the ping-pong handovers effectively. View full abstract»

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  • A new test rule of local mean of a mobile radio signal

    Page(s): 179 - 182
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (621 KB)  

    The pivotal parameters, which include statistical interval, sampling interval and sampling points, of the local mean of a mobile radio signal is described. A new test rule of estimate of local mean of a mobile radio signal is deduced by considering the correlation between different sampling points, the mutual influence between statistical interval and sampling interval, based on the mean estimate sampling algorithm composed by W.C.Y Lee. View full abstract»

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  • One type of GSM-R fast handover algorithm for high-speed railway

    Page(s): 175 - 178
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (550 KB)  

    With the construction of high-speed railway and passenger-dedicated railway, GSM-R digital mobile communication system is developing fast in China. Meanwhile it brings some problems demanding to be solved promptly, fast and reliable handover is one of them. In this paper, a new type of fast handover algorithm which is applied in high-speed railway is present, analysis is made on implementation methods and performance of this algorithm, comparison to the normal handover algorithm is also made to indicate the advantage on decreasing the handover time delay of the fast handover algorithm. View full abstract»

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  • Research on integrated network management model based on CORBA and mobile agents

    Page(s): 135 - 138
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (439 KB)  

    CORBA and mobile agents are two popular network management technologies. This research investigates these two technologies and some existing integrated approaches thoroughly. Based on this investigation, a novel network management model is proposed, which provides a comprehensive, efficient approach to network management, by integrating CORBA and mobile agents technologies into a unified model and pertaining the advantages of each of the technologies. The result of the experiment showed that the performance of network management can be significantly improved. View full abstract»

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  • A fast Automatic Gain Control scheme for IEEE 802.15.4 receiver

    Page(s): 167 - 170
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (646 KB)  

    The requirements for IC core based on IEEE 802.15.4 are fast computing and low complexity which challenge the traditional Automatic Gain Control (AGC) design. This paper presents a fast AGC scheme for IEEE 802.15.4 receiver, which can quickly accomplish gain adjustment in less than 1.5 symbols. Relating to numeric constant parameters determining the gain convergence speed and the number of samples beyond given thresholds, exponential non-linear adjustment functions are employed. For signals with large dynamic range, the proposed AGC scheme can adjust signals quickly and accurately. By achieving the full scale of Analog-to-Digital (A/D) converter, the proposed scheme can work well in low Signal-to-Noise Ratio (SNR) environment with low complexity. View full abstract»

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  • New decoding algorithms for super-symmetric rank codes

    Page(s): 204 - 207
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (612 KB)  

    New decoding algorithms for the super-symmetric rank codes [1] are constructed. They include the recurrent decoding algorithm and the majority decoding algorithm. The super-symmetric rank codes are rank-metric codes over binary fields with lengths Ns = 2s, s = 0, 1, …, where codes of length Ns are designed recursively from codes of length N−1. This provides block symmetry construction of code matrices and allows to decode corrupted received matrices starting with a small size. The new decoding algorithms are described and simulation results are presented. View full abstract»

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  • Adaptive image delivery based on WAP

    Page(s): 159 - 162
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (501 KB)  

    The limited display capability, storage, processing ability and the changing bandwidth of wireless network are main obstacles for mobile devices to access the images on website using WAP technology. This paper proposes a new method to design a WAP gateway, which can modify the images on website automatically according to Quality of Service (QoS). The quality of images on website, the capability of mobile devices and the bandwidth of wireless network are used to establish an optimal target function. An improved genetic algorithm (GA) with a new coding method, a new crossover operator and a mutation operator is put forward to solve the optimal modifying parameters for the images on website. The simulation results show that the proposed method in this paper can quickly access the images on website by WAP with the requirement of QoS. View full abstract»

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  • Satellite imaging traffic modeling and simulation

    Page(s): 155 - 158
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (780 KB)  

    The satellite imaging traffic modeling and simulation is mainly discussed in this thesis. Firstly, there are two kinds of satellite reconnaissance imaging traffic models are built. They are focus and bar scan. And some calculation examples of them are given according to the parameters of “Starlite” reconnaissance satellite constellation of U.S. Secondly, the information storage capacity of the reconnaissance satellite without satellite transmission network is simulated and calculated which illustrates satellite transmission network is necessary. Lastly, the transmission of satellite recon imaging information through a satellite transmission network is simulated and some primary simulation conclusions are given. View full abstract»

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  • Study on interference suppression for UWB communications

    Page(s): 151 - 154
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (749 KB)  

    In this paper, the performance of interference suppression method named adaptive modified template waveform (AMRTW) is analyized. Due to the disadvantages of interference suppression for this method, a novel algorithm for sub-band signal decomposition is proposed in this paper. By the signal sub-band weighted parameters adjustment, this new algorithm can improve the performance of the AMRTW technology for interference suppression efficiently in Ultra-Wideband communications with the low complication. View full abstract»

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  • On increasing system throughput for non real-time users using hierarchical modulation in IEEE802.16 network

    Page(s): 147 - 150
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (373 KB)  

    In this paper, we propose a novel cross-layer approach of opportunistic scheduling to increase system throughput for IEEE 802.16 downlink transmission. Traditionally wireless users are scheduled according to the type of their subscribed service. The key idea of this paper is to combine hierarchical modulation with opportunistic scheduling, which not only yields a larger over-all system throughput, but also maintains the fairness determined by the type of traffic. As shown by the provided simulation results, the total information capacity for non real-time user is increased without penalising much on the real-time user. View full abstract»

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  • Integrating MANET and the internet via an adaptive TTL gateway discovery scheme

    Page(s): 143 - 146
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (650 KB)  

    Gateways act as bridges for forwarding data packets between integrated mobile ad-hoc networks (MANETs) and the Internet. Mobile nodes in MANETs must discover available gateways to gain access to the Internet. This study presents an adaptive gateway discovery scheme that balances efficiency and overhead by limiting the flooding scope of gateway advertisement messages. The proposed scheme dynamically adjusts the ADV_TTL according to the average delay time of network. The simulation results showed that the proposed scheme obtains the shortest average delay time while keeping the network a relatively lower overhead. View full abstract»

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  • Performance analysis of SCPS-TP SNACK in space communication

    Page(s): 1 - 4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (675 KB)  

    TCP has been a robust and efficient protocol for terrestrial networks, but it does not fare very well in the space environment because of the long-link delay, high bit-error-rate, asymmetric bandwidth, intermittent links compare with the terrestrial networks. However, it does provide an excellent base for extension. The Space Communications Protocol Standards (SCPS) has proposed Transport Protocol (SCPS-TP) which is a popular modification of TCP that is very efficient for space environments. The Selective Negative Acknowledgement (SNACK) is an important option provided by SCPS-TP. The focus of this paper is to investigate the performance of SCPS-TP SNACK in hybrid networks with space segments. The paper proposes a new mode, which is IP over CCSDS AOS, to integrate the space network with the ground network at first, based on this mode; it designs the topology for the hybrid networks; then, the paper analyses the performance of the SCPS-TP SNACK in the hybrid networks. The results show that SCPS-TP SNACK has a better performance than the regular TCP in space communication. View full abstract»

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  • Smooth handoff in infrastructure wireless mesh networks

    Page(s): 171 - 174
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (450 KB)  

    Supporting user mobility is an important requirement for wireless mesh networks. We propose a relay-router buffering-and-forwarding scheme for supporting smooth handoff in the infrastructure wireless mesh networks. Our proposal is based on buffering packets at intermediate relay routers in the packets forwarding route and neighbouring relay routers working in promiscuous mode which can overhear the packet transmission from neighbouring relay routers to APs. With the help of relay routers, the forwarding path of buffered packets is shortened greatly. The relay routers selection is based on multipoint relays of OLSR protocol. Simulation results show that this scheme improves the data availability and results in reducing the packet loss significantly. View full abstract»

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  • A modified weighted bit-flipping algorithm for LDPC codes

    Page(s): 227 - 230
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (669 KB)  

    In this paper, a modified weighted bit-flipping (WBF) algorithm is proposed for finite geometry Low-Density Parity-Check (FG-LDPC) codes. The calculation for the flipping function in the new method includes all the elements in sum product algorithm (SPA) instead of the minimum one in most existing methods. Simulation results show that the proposed method exhibits better performance than the best method available in the literature so far. The performances of different algorithms are also considered in random constructed LDPC codes. The reliability ratio based WBF (RRWBF) method performs the best in this kind of codes and the proposed method performs very closely to the RRWBF method. The decoding complexities for both FG-LDPC and random constructed LDPC are also analyzed. View full abstract»

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  • Robustness of complex cooperative communication network

    Page(s): 260 - 263
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (740 KB)  

    The research on robustness is an important issue for complex networks. Recently, to improve the communication performances, wireless cooperative communication has become a promising way. Therefore, to achieve better benefits of cooperative communication, the robustness research on complex cooperative communication network — CCCN is necessary. In this paper, the network evolution model for CCCN is established and the average path length is used to evaluate its robustness performance. The simulation results show that the CCCN is power-law in degree distribution and more stable than the one without cooperative communication in combating the random nodes attack and intentional nodes attack. View full abstract»

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  • Particle swarm optimization for MIMO receivers

    Page(s): 255 - 259
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (788 KB)  

    MIMO receivers need to have good knowledge about channel. To get good channel estimation needs to good pilot sequences and good channel estimator. The good pilot sequences can ensure the channel estimator converge the channel parameters by short length of pilot sequences, while good channel estimator can employ fewer iteration to estimate channel parameters. To reach the first goal, this paper proposes a design of pilot sequences for MIMO channels, only with ML training symbols; to reach the second goal, this paper proposes a PSO channel estimation algorithm. Different from the known PSO algorithms, in the proposed PSO estimator algorithm, the ‘particle positions’ are virtual, they represent the MIMO weights matrices, and the ‘particle velocity’ is also virtual, it represent the updating increment of MIMO weights matrices, which simplifies the PSO algorithm's implementation. In the iteration of the estimator, the proposed PSO algorithm finds desired MIMO weights matrix through the interaction of individuals in a population of weights matrices. Simulations show that the BER performance of the proposed PSO MIMO equalizer is better than those of conventional adaptive equalizers. View full abstract»

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  • Channel estimation based on iterative interpolation for wireless communication in OFDM system

    Page(s): 251 - 254
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (993 KB)  

    OFDM has become the hotspot in the research of wireless communication, and channel estimation is one of the key techniques of OFDM. In this paper, a channel estimation algorithm based on iterative interpolation for wireless communication is proposed. This algorithm first obtains initial estimate of the next receiving symbol, then the precise estimate is acquired by the amendment of the frequency response of the symbols. The simulation results demonstrate that this algorithm can effectively track the channel properties, which leads to its good performance in channel estimation. View full abstract»

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  • A robust decision-directed channel estimator for OFDM systems

    Page(s): 247 - 250
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (876 KB)  

    This paper deals with the estimation of channel frequency response in orthogonal frequency division multiplexing (OFDM) systems. Since existing DD estimators such as LS estimator and the MMSE estimator do not appropriately reduce the influence brought by incorrect decision, and hence suffer from error propagation. Then, in order to mitigate error propagation in DD channel estimation, a DD estimator based on iterative LMMSE is proposed. The algorithm takes the error vector as innovation for the current channel state information (CSI), then calculates the impact that the innovation brings to the current CSI estimation according to the orthogonallity principle and then modify the current CSI, thereby the effect induced by error can be reduced. Simulation results show that the proposal can effectively track the time variations in both the Multipath channel and AWGN channel. View full abstract»

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  • Adaptive multiuser detection based on Gibbs sampler

    Page(s): 243 - 246
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (839 KB)  

    We present an adaptive multiuser detection scheme in multipath channel for coding CDMA systems. The scheme uses the Gibbs sampler[1] to estimate the channel gains and the transmitted symbols. In receiver, the channel decoder delivers information about the code bits prior distributions, which can be fed back to the multiuser detector to refine its detection processing. We estimate the BER of the feedback for multipath channels with quasi-static Rayleigh fading and quadrature phase-shift keying (QPSK) transmission. The simulation results show that the novel multiuser detector can offer the better performance in the DS-CDMA systems. View full abstract»

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  • Analysis of group multiuser detection based on coalitional game

    Page(s): 239 - 242
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (546 KB)  

    The issue of group-blind multiuser detection in MAC channel among wireless nodes in the environment of multiple networks coexisting and sharing spectrum is addressed under the Framework of coalitional game. We investigate the performance and stability of multiple access channel (MAC) with linear decorrelating multiuser detection under varying SNR, channel gains and coalitional structures, in which both single BS and multiple BSs cases were considered. The main results and conclusion are as follows: (1) the grand coalition is payoff maximizing under loose SNR; (2) it is in conformity with group and coalitional rationality forming coalition among nodes that have comparative channel gains. View full abstract»

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  • Opportunistic network coded information exchange among multi-user

    Page(s): 195 - 199
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (903 KB)  

    This paper investigates the strategies of relaying based on opportunistic network coding over wireless communication context with two pairs of users and one common relay exchanging their data, where the relay node can transmit either network-coded or un-coded packets. Resorting to a Markov model, the paper characterizes the average packet delay and energy power consumed by the relay node. The results of simulation indicate that there exists some tradeoff between delay and energy power. View full abstract»

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  • Crossover product accumulate codes: EXIT analysis and performance

    Page(s): 231 - 234
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1098 KB)  

    Crossover product accumulate (CPA) codes, proposed recently, are a novel class of provably good error-correcting codes with low encoding and decoding complexity. In this paper, EXIT chart is used to predict the SNR convergence threshold of CPA codes. Iterative decoding stop criteria are proposed for CPA codes, and are used to simulate the performance of CPA codes. Analysis and simulations show that CPA codes provide a lower error floor than product accumulate (PA) codes, while CPA codes possess the same convergence threshold as PA codes, and the iterative decoding stop criteria proposed can reduce the decoding complexity and achieve excellent bit-error-rate (BER) performance. View full abstract»

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