IET 3rd International Conference on Wireless, Mobile and Multimedia Networks (ICWMMN 2010)
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- Location: Beijing, China
- Conference date: 26-29 Sept. 2010
- ISBN: 978-1-84919-240-8
- Conference number: CP569
- The following topics are dealt with : communication network; wireless communication; signal processing for communication; speech and video processing for multimedia networks; and ubiquitous computing.
1 - 20 of 93 items found
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A trusted neighbor table based location verification for VANET routing
- Author(s): Xiaoping Xue ; Nizhong Lin ; Jia Ding ; Yiwen Ji
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In this paper, we examine one of the security issues in vehicular ad-hoc network (VANETs) routing: position-spoofing attack. We propose a trusted neighbor table (TNT) based location verification scheme to detect and prevent position-spoofing attack. The basic idea of our scheme is to establish a TNT for each node to record the latest location of its neighbors, and each neighbor has a trust value. Since our TNT is trusted, by choosing a next hop from it and considering its trust value, we can mitigate the influence of falsified position information in geographic routing protocols. Analysis shows that our scheme is secure and efficient.
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GSM-R network planning for high speed railway
- Author(s): Guo Hui ; Wu Hao ; Zhang Yushu
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It is necessary to provide corresponding wireless communication network plan scheme for China high speed railway development. This paper investigates the quality of service of high speed railway wireless communication system according to carrier-to-interference, bit error rate and handover standard. Simulation results indicate that this communication network could hardly work rightly in urban and suburban; whereas in the rural area it could provide enough quality under some network plan conditions: for rural quasi-open area the cell radius should be less than 7km and the overlap area should be between 3.9km and 5.5km; for rural open area, the cell radius could reach 10km with the overlay area between 4.8km and 8.1km.
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The research of improved PTS method for peak-to-average power ratio reduction
- Author(s): Zhang Xiuyan and Tao Guobin
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One of the main drawbacks of orthogonal frequency division multiplexing (OFDM) is the high peak-to-average power ratio (PAPR) of the OFDM signal. How to reduce the PAPR is the key to applying the technology of OFDM efficiently. In this paper, two new methods to reduce the PAPR of OFDM signals based on the combination of Clipping or matrix transform with PTS are presented. Then PAPR is reduced by using the combination method through simulation. Simulation results have shown that the proposed methods are very effective and flexible to improve PAPR performance in the MIMO-OFDM.
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A hybrid low complexity decoding of LDPC codes
- Author(s): Hua Wang ; Guangrong Fan ; Jingming Kuang
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An efficient early stopping criterion based on the evolution of the number of reliable variable nodes (NRVN) is proposed for low density parity check (LDPC) codes in this paper. This criterion can significantly reduce the average number of iterations (ANI) at low to middle signal to noise ratios (SNRs) with minimal performance degradation. Furthermore, a hybrid decoding method is presented to reduce the decoding complexity of LDPC codes by combining the proposed stopping criterion and forced convergence (FC) decoding algorithm. Compared with the classic belief propagation (BP) decoding, significant computation complexity reduction can be achieved with small computation overhead.
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Enhancing the performance of IDMA system by irregular LDPC codes
- Author(s): Jingxi Zhang ; Zhisong Bie ; Weiling Wu
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A method to enhance the performance of IDMA system by means of irregular LDPC codes was studied. Interleavers were used as signature character for user identification and iterative turbo detection and decoding approach was employed with reduced complexity. Gaussian approximation was applied to approximate the message probability density function on factor graph with multiple users. Iterative message update formulas on factor graph were derived. Degree profiles were obtained by using the iterative formula. Simulation result shows that the performance of irregular LDPC-Coded LDMA system is better than that of (3,6) regular LDPC-Coded IDMA system in terms of BER and performance gain about 0.6 dB is achieved at BER 10s with 8 users for AWGN multiple access channel.
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The circulate property of generator matrices of protograph LDPC codes
- Author(s): Kaiyao Wang ; Shaohai Hu ; Yang Xiao ; Kiseon Kim
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The LDPC application involves the problem: encoding complexity. Since the generator matrices are dense and with random positions of "1s", the encoder needs to store every "1" of the generator matrices by using huge chip area. To solve problem, we need to design the LDPC codes with block cyclic generator matrices. This paper reveals that the protograph LDPC codes can have lower encoding complexity under the condition of the proposed theorem that the parity check matrices of the LDPC codes are nonsingular and circulate. The circulate property of generator matrix of protograph LDPC codes can be obtained from the quasi-cyclic parity check matrix of protograph LDPC codes. Thus it can reduce the encoding complexity. We give an algorithm of protograph LDPC codes with fast encoding based on the theorem, and it verifies that protograph LDPC codes with circulate property of generator matrices can simplify encoder hardware implementation.
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The differential transmitter and receiver for cognitive MIMO systems
- Author(s): Jing Liu ; Shaohai Hu ; Yang Xiao ; Xiaoli Liu ; Moon Ho Lee ; Kiseon Kim
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In this paper, a cognitive MIMO system with differential space-time coding is proposed, in which the cognitive link communicates using two transmission antennas and one receiving antenna. Cognitive MIMO systems allow the licensed spectrum to be opportunistically exploited by the cognitive user, so they enable public access to the underutilized spectral bands and therefore the overall spectral efficiency can be economically increased. While in some situations, such as high-mobility environment or channel fading rapidly, it may be difficult and costly to estimate the channel accurately for cognitive MIMO systems. To solve the problem, differential spacetime coding scheme has been proposed for cognitive MIMO systems. The construction of the differential transmitter and receiver for the cognitive MIMO system is provided.
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Performance comparison of LDPC-coded IDMA system with equal spreading and unequal spreading
- Author(s): Jingxi Zhang ; Zhisong Bie ; Weiling Wu ; Yang Li
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A scheme of applying unequal spreading to LDPCCoded IDMA system was proposed. The issue of LDPC-Coded DDMA system with equal spreading and unequal spreading was studied. Gaussian approximation was applied to the messages probability density distribution function between nodes on factor graph of LDPC-Coded spreading system. We compare two cases, the first is optimization of LDPC with fixed spreading factor, and the second is joint optimization of LDPC and spreading degree. By means of iteration and applying the method of differential evolution we obtained degree profiles in the case of 8 users with equal spreading and unequal spreading on condition that the system spectral efficiency is the same. We constructed the check matrix randomly based on the optimized degree profiles and made simulations. It has shown that the performance of LDPC-Coded spreading IDMA system cannot be improved by joint optimization of LDPC code and spreading degree for AWGN Multiple Access Channel (MAC) from the perspective of approaching MAC channel capacity. The result gives us guidance in designing LDPC-Coded IDMA spreading system.
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A novel nonsinusoidal orthogonal band division modulation method
- Author(s): Xiguo Liu ; Lei Zhang ; Genchun Shu ; Chuanhui Liu
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In this paper, a novel nonsinusoidal orthogonal band division modulation method novel nonsinusoidal orthogonal band division modulation method (NOBDM) is proposed. The idea of frequency division multiplexing is used in the nonsinusoidal orthogonal modulation in time domain (NOM). The frequency band of the system is divided into a lot of shoulder-to-shoulder subbands and the NOM are used in each subband. Due to the best energy concentration character of the Prolate Spheroidal Wave Function (PSWF), the modulated signals of different bands are not interfered each other. The novel method not only has the advantages for compensation and bit loading but also reduces the complexity of orthogonal pulse sets design and implementation. The results of the Monte Carlo simulation show that the proposed method has approximate the same BER performance as the old ways. The scheme is suitable for the wire or wireless broadband communication system.
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Improvement of direct spreading spectrum by multi-spreading spectrum
- Author(s): Fan Jing and Xu Shufang
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In the direct spreading spectrum(DSS) the number of length of spreading is less, and the several errors will lead to sharp decrease of peak-to-sidelobe ratio and the errors sometimes cannot be corrected. To solve this problem, a new method of Multi-Spreading Spectrum (i.e. MSS) with error-correcting ability is proposed. The new method is combining several correlation receptions and majority algorithm and its performance on error-correcting is much more batter than the DSS, and the new MSS method also give more number of spreading length. MSS not only performs better than Direct Spreading Spectrum (DSS) in the similar condition, but also is easier to be realized.
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A novel radio propagation channel sounding method based on antenna pattern diversity
- Author(s): Yi Zhou ; Ping Wang ; Xiaoyan Huang ; Aihuang Guo ; Fuqiang Liu
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In this contribution, we propose a novel radio propagation channel sounding platform and an analysis method based on antenna pattern diversity. The proposed method can avoid possible antenna mutual coupling and correlation phenomena; otherwise the characteristics discrimination capability in time-space domain will be weakened, and the channel analysis complexity will be increased as well. The beam-scanning space measurement, combining with the high resolution parameter estimation algorithm, will contribute to analyze the detailed characteristics of propagation channels, improve the accuracy of the channel analysis, and reduce the complexity of data post-processing. These features are beneficial to conduct accurate channel modeling in future wireless communications.
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Scalable link lifetime estimating mechanisms in mobile ad hoc network
- Author(s): Wang Ru-yan ; Wu Da-peng ; Dai Qi ; Huang Sheng
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In order to guarantee the quality of service (QoS) of multimedia applications in Mobile Ad hoc network (MANET), the stable end to end path should be established effectively. An effective link lifetime estimation mechanism is introduced, which can also be used to select the better path in the route discovery process. Simulations show that with the estimating interval selected reasonably, our mechanisms can provide accuracy estimating results for link lifetime.
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Scintillation of a tracked gaussian beam for ground-to-satellite laser communication
- Author(s): Xiang Jingsong and Zhang Xiaolei
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Recent researches have revealed that, for a tracked uplink Gaussian beam, the scintillation index predicted by the weak fluctuation theory is significantly different from that of the numerical wave optics simulation method when the size of the transmitter aperture is large. In this paper, turbulence-induced scintillation index and the probability distribution of fluctuating irradiance for a tracked uplink Gaussian beam are studied using numerical wave optics simulation method. The simulated data show that in the discrepancy region between the weak fluctuation theory and the numerical simulation method, the simulated fluctuating irradiance is not governed by the generally accepted lognormal distribution even when the weak fluctuation condition is still satisfied.
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A cognitive spatial multiplexing scheme for MIMOCDMA networks
- Author(s): Yang Xiao ; Kiseon Kim ; Guangzhi Qu
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The existing cognitive schemes have not considered cognitive spatial multiplexing (CSM) for MIMO-CDMA network, there are three vital problems to hinder CSM's application: spatial channels' estimation for mobile stations(MSs), space-time coding and decoding for base station (BS) and MSs, the implementation complexity of BS and MSs. To solve the problems, a simplified cognitive spatial multiplexing scheme is proposed, including BS and MS systems, where MIMO BS in a cell has two antennas and each MS of lower moving speed has one antenna only. To ensure communication quality of the network, the scheme applies LDPC as the channel coding instead of space-time coding for BSs and MSs. BS assigns the same CDMA channels for MSs to have larger space interval. Simulations show that good spatial multiplexing capacity and BER performance have been achieved by the proposed scheme.
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One scheme of cooperative diversity with two satellites based on the Alamouti code
- Author(s): Zang Guo-zhen ; Huang Bao-hua ; Mu Jing
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Aiming at the low Earth orbiting (LEO) satellite mobile communication, the cooperative diversity technology is applied to the forward downlink in this paper, and one scheme for cooperative diversity with two satellites based on the Alamouti code is presented. To reduce the non-negligible path delay from the different satellite to the same terminal, the synchronous CDMA is used and satellites are distinguished by the spreading codes which are orthogonal each other in this scheme. Simulation results show the satellite cooperative diversity system can obtain better performance than the traditional uncoded BPSK system with the same fading channel and system parameters. Though the satellite cooperative diversity system has worse performance than the traditional satellite diversity system, it has the advantage in communication range and low complex mobile terminal. Particularly, this new scheme can be used as an effective means to improve the performance in the area where the gateway can not be built.
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Fast iterative user selection for multiuser MIMO system
- Author(s): Xie Zhibin ; Yan Peiyu ; Liu Shujuan ; Wang Biao
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In a downlink multiuser multi-input multi-output (MU-MIMO) communication system, a base station (BS) transmits to multiple mobile stations (MS) simultaneously over the same frequency band, thereby greatly increasing the channel capacity. However, in previous works, the multiuser spatial multiplexing system has no special strategies for selecting the multiuser channel. Although the exhaustive search algorithm can achieve optimal performance, its cost is large. In this paper, we propose a suboptimal user selection algorithm for the MU-MIMO system to save hardware resources and serve more users. The proposed selecting criterion bases on maximum total throughput by selecting the best channel of user. To reduce the complexity further more, we give out an iterative selection scheme. Compared with the optimal algorithm, the proposed algorithm achieves good sum capacity performance, has lower complexity, and is suitable for practical communication system. Simulation results show the performance of the proposed scheme.
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Architecture of IMS over WiMAX PCC and the QoS mechanism
- Author(s): Ying Wang ; Wei Liu ; Wei Guo
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This paper discusses the IMS over WiMAX PCC framework and analyzes the end-to-end QoS mechanism based on the concept of bearer and integration, especially, feasible QoS provisioning signaling and a cross-layer QoS mapping strategy are proposed.
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CSMA/CA-based MAC protocol in cognitive radio network
- Author(s): Yanchang Liu ; Shaohai Hu ; Yang Xiao ; Xiaoli Liu ; Guangzhi Qu ; Kiseon Kim
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Different from the MAC of IEEE 802.11, the application of IEEE 802.22 suffers the uncertain spectrum and frequency width, which can not ensure the access of mobile users to be valid. To solve the problem, in this paper, we modify the CSMA/CA mechanism in order to make it suit the Cognitive Radio environments, in which the spectrum can be effectively used. We validate the modification by numerical analysis.
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The multiple prioritized access mechanism of cognitive networks
- Author(s): Xiaoli Liu ; Shaohai Hu ; Yang Xiao ; Yanchang Liu ; Guangzhi Qu ; Kiseon Kim
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Developments of wireless communication technology need higher standards of reliability of network and full utilization of resources. The proposition of Cognitive Network improves the utilization of frequency spectrum effectively. Main tasks of this paper are to introduce EDCA mechanism into the Cognitive Networks and validate if it can guarantee the classified service access effectively. First of all, we develop an access control for the Cognitive Networks, which adapts the EDCA mechanism of WLAN and sets different priorities for Cognitive users. Secondary, we propose a new prioritized access control algorithm for Cognitive Network, which adapts Linear Backoff Algorithm, Stall Avoidance Scheme etc. to enhance the performance. Finally, we use and extend NS2 to satisfy the Multi-priority access with multi-interface and multi-channel. Primary User and Cognitive Users connect to the same node, which satisfies multi-interface and multi-channel. We can reach the conclusion that the performance of Cognitive Network used mechanism of EDCA is better than that of used mechanism of DCF. The spectrum utilization of Cognitive Network is higher than that of Non-cognitive Network. Primary Users would not be interfered by Cognitive User.
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Distortion optimization based on power allocation for wireless video sensors
- Author(s): Xiaofeng Xu ; Chong Tan ; Jian Chen
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Wireless video sensor networks (WVSNs) feature the characteristics of easy deployment and low maintenance cost and therefore are suitable for a wide range of important applications, including remote surveillance, health care delivery and traffic control systems. Compared to traditional communication systems, Sensor nodes in WVSN operate under resource constrains such as power supply and transmission bandwidth. The main object of this paper is to study the resource allocation of a wireless sensor node and improve the system performance, especial the video distortion. More specifically, by taking into account the relations between separated modules on a sensor node, we build a comprehensive power-rate-distortion (PRD) framework for WVSN optimization. Based on this framework, we address the problem of power allocation between video encoder module and wireless transmission module on the node to achieve the optimal reconstructed video quality under power and rate constraints.
