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Wireless Channels (wireless + channel)
Selected AbstractsError-aware and energy-efficient routing approach in MANETsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 1 2009Liansheng Tan Abstract The lifetime of a network is the key design factor of mobile ad hoc networks (MANETs). To prolong the lifetime of MANETs, one is forced to attain a tradeoff of minimizing the energy consumption and load balancing. In MANETs, energy waste resulting from retransmission due to high bit error rate (BER) and high frame error rate (FER) of wireless channel is significant. In this paper, we propose two novel protocols termed multi-threshold routing protocol (MTRP) and enhanced multi-threshold routing protocol (EMTRP). MTRP divides the total energy of a wireless node into multiple ranges. The lower bound of each range corresponds to a threshold. The protocol iterates from the highest threshold to the lowest one and chooses those routes with bottleneck energy being larger than the current threshold during each iteration. This approach thus avoids overusing certain routes and achieves load balancing. If multiple routes satisfy the threshold constraint, MTRP selects a route with the smallest hop count to further attain energy efficiency. Based on MTRP, EMTRP further takes channel condition into consideration and selects routes with better channel condition and consequently reduces the number of retransmissions and saves energy. We analyze the average loss probability (ALP) of the uniform error model and Gilbert error model and give a distributed algorithm to obtain the maximal ALP along a route. Descriptions of MTRP and EMTRP are given in pseudocode form. Simulation results demonstrate that our proposed EMTRP outperforms the representative protocol CMMBCR in terms of total energy consumption and load balancing. Copyright © 2008 John Wiley & Sons, Ltd. [source] Measurement-based admission control scheme with priority and service classes for application in wireless IP networks,INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 6 2003Abbas Jamalipour Abstract Wireless IP networks will provide voice and data services using IP protocols over the wireless channel. But current IP is unsuitable to provide delay or loss bounds and insufficient to support diverse quality of service, both required by real-time applications. In order to support real-time applications in wireless IP networks, in this paper a measurement-based admission control (MBAC) with priority criteria and service classes is considered. First we have shown the suitability of MBAC in wireless IP networks by comparing its performance with a parameter-based scheme. Next, we have investigated the performance of strictly policy-based MBAC and policy plus traffic characteristic-based MBAC schemes in terms of (1) increasing the user mobility, (2) changing traffic parameters and (3) the presence of greedy users. The efficiency and fairness of each scheme are measured in terms of lower class new and handoff traffic performance. Copyright © 2003 John Wiley & Sons, Ltd. [source] An efficient dynamic group key agreement protocol for imbalanced wireless networksINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 4 2010Yun-Hsin Chuang Owing to the popularity of wireless networks, the group key agreement (GKA) design is critical for providing secure group communications over an insecure wireless channel. In 2005, Nam et al. proposed a GKA protocol for imbalanced wireless networks in which an imbalanced wireless network consists of many mobile nodes with limited computing capability and a powerful node with less restriction. In 2007, Tseng showed that Nam et al.'s protocol is not a contributory GKA, while he also proposed a new GKA protocol. However, neither GKA protocol is concerned with dynamic member joining/leaving. This is an important functionality of GKA, especially for a wireless network environment. In this paper, we propose a dynamic group key agreement protocol for imbalanced wireless networks, and show that it requires less computation cost for dynamic member joining/leaving as compared to the previously proposed protocols. We also show that the proposed protocol is provably secure against passive attacks under the decision Diffie,Hellman problem and the hash function assumptions. Furthermore, by the pre-shared two-party key between a mobile node and the powerful node in the existing imbalanced wireless networks, we propose a generalized GKA protocol that requires only several hash functions. Copyright © 2010 John Wiley & Sons, Ltd. [source] Iterative channel estimation and data detection in frequency-selective fading MIMO channels,EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 5 2004Maja Lon Signals transmitted through multiple-input multiple-output (MIMO) wireless channels suffer from multiple-access interference (MAI), multipath propagation and additive noise. Iterative multiuser receiver algorithms mitigate these signal impairments, while offering a good tradeoff between performance and complexity. The receiver presented in this paper performs channel estimation, multiuser detection and decoding in an iterative manner. The estimation of the frequency selective, block-fading channel is initiated with the pilot symbols. In subsequent iterations, soft decisions of all the data symbols are used in an appropriate way to improve the channel estimates. This approach leads to significant improvement of the overall receiver performance, compared to other schemes. The bit-error-rate (BER) performance of the receiver is evaluated by simulations for different parameter setups. Copyright © 2004 AEI. [source] Prioritisation of data partitioned MPEG,4 video over mobile networks,EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 3 2001Stewart T. Worrall Despite much research in the field of mobile multimedia, delivery of real,time,interactive video over noisy wireless channels remains a challenging problem. Two of the major issues in providing true end,to,end mobile multimedia capability are interoperability between platforms and networks and the poor performance of video compression algorithms in error,prone environments. This paper presents a method for prioritising data partitioned MPEG,4 video in a way suitable for transmission over a mobile network. The effectiveness of the technique is demonstrated by examining the performance when transmitted using the Real,Time Transport protocol over GPRS (General Packet Radio Service) data channels under varying channel conditions. [source] Closed-form expression for the BER of m-QAM-OFDM systems over time- and frequency-selective wireless channelsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 8 2006F. Castells Abstract The broadcast DVB-T system is an m-QAM-OFDM communication system that includes pilot-symbol-assisted modulation (PSAM) in order to enhance channel estimation at the receiver. This characteristic makes DVB-T suitable for a mobile reception, over time- and frequency-selective wireless channels. In this work, a closed-form expression for the BER as a function of the transmission system, channel model and the channel estimation strategy employed at the receiver is derived. In addition, adjacent channel interference due to Doppler effects is also considered. The results are focused on the DVB-T system under different scenarios. The channel estimation at the receiver has been shown to be very critical, and the impact of channel estimation errors on the BER is analysed in detail. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||