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Wireless Communications & Signal Processing, 2009. WCSP 2009. International Conference on

Date 13-15 Nov. 2009

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Displaying Results 1 - 25 of 368
  • [Title page]

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    Freely Available from IEEE
  • [Copyright notice]

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    Freely Available from IEEE
  • Analysis of per-layer transmit and receive filters design for multiuser MIMO systems with Tomlinson-Harashima precoding

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB) |  | HTML iconHTML  

    In this paper, the per-layer design for Tomlinson-Harashima precoding (THP) in the downlink of multiuser multiple-input multiple-output (MIMO) systems is investigated. In these systems, multiple antennas are located at all the transceivers, and the number of the receivers is equal to that of the transmit antennas. Based on the criterion of maximizing system sum-capacity, we propose two per-layer joint transmit and receive filters design schemes with receive antenna beamforming (RAB) and receive antenna selection (RAS), respectively. Moreover, the differences of the equivalent channel gains between these two schemes are theoretically analyzed. Simulation results indicate that by the proposed schemes, the system sum-rate can be improved significantly relative to the per-user processing scheme. View full abstract»

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  • On the optimal antenna placement for DAS systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (230 KB) |  | HTML iconHTML  

    As a promising technique, distributed antenna systems has attracted much research attention in the past few years. In this paper, an optimal antenna placement criterion is proposed to maximize the lower bound of the cell average ergodic capacity. In the analysis, per-antenna power constraint (PAPC) is considered and the single transmit selection strategy (where just one distributed antenna is used) is used. The numerical results demonstrate the significant performance gain of the proposed system topology over the random DAS and CAS, which proves the rationality of the proposed criterion. View full abstract»

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  • Detection of ships for OTHR based on AR-MUSIC algorithm

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB) |  | HTML iconHTML  

    In order to ensure the data rate, ship detection within short coherent integration time (CIT) is an operational requirement for over-the-horizon radar (OTHR). However, the resulting low Doppler resolution of short CIT brings difficulties in discrimination of the ship target peak and the powerful ocean clutter. To solve this problem, high resolution spectrum estimation techniques have been used to replace the conventional Fast Fourier Transform (FFT) for Doppler spectrum analysis. In this paper, a new spectrum estimation algorithm is proposed for ship detection by OTHR, which has higher Doppler resolution compared with the conventional method. In addition, in case that the signal-to-noise ratio (SNR) is low or the Doppler frequency of the target is close to that of the first-order ocean clutter Bragg peak, the presented algorithm can still effectively be used for ship detection for OTHR. The superiority of the proposed algorithm is illustrated by simulated OTHR data. View full abstract»

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  • High-resolution DOA estimation of noncircular signals without source enumeration and eigendecomposition

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB) |  | HTML iconHTML  

    This paper presents a fast method for estimating directions of arrival (DOAs) of multiple narrowband noncircular signals (such as AM, ASK, and BPSK signals), which involves neither eigende-composition nor source enumeration. This method also eliminates the need for knowledge of the spatial characteristics of the circular noise and interference, by exploiting merely the conjugate spatial coherence, namely the conjugate correlations between the received signals at different sensor positions. The proposed approach is still applicable to the integer conjugate minimum redundancy linear arrays (CMRLA), designed by Gelli and Izzo, to accommodate possibly more uncorrelated noncircular signals and enhance the DOA estimation accuracy for a given number of sensors. View full abstract»

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  • A high efficiency spread spectrum modulation based on Non-Strictly Orthogonal Sequences

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (282 KB) |  | HTML iconHTML  

    Wireless spread spectrum technologies are widely used in the implementation of WLAN physical layer. Bits error rate (BER) and bandwidth efficiency are the two most important aspects we concern. In this paper, we propose a high efficiency spread spectrum modulation technology based on the definition of non-strictly orthogonal sequences (NS-OS). Simulation shows that the proposed scheme has a better performance than the traditional technologies do under AWGN channel, and a parameter q defined in this scheme could be tuned to balance BER performance and bandwidth efficiency according to different applications. View full abstract»

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  • ARC-MAC: An automatic relay cooperative MAC protocol for wireless Ad Hoc networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (275 KB) |  | HTML iconHTML  

    In this paper, we present a cooperative MAC protocol called automatic relay cooperative MAC (ARC-MAC) for wireless Ad Hoc networks. ARC-MAC develops the 802.11 DCF to five handshakes, which is suitable for cooperative transmission. According to the channel condition, neighbors decide whether it is a relay by itself, and the relay helps the source transmitting packets with a definite probability. An analytical model is also presented to compute the throughput of the ARC-MAC, and the results show ARC-MAC can improve the system performance greatly. View full abstract»

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  • Increasing reliability of an interactive mobile satellite telecommunication system using diversity and MIMO schemes

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB) |  | HTML iconHTML  

    Observation of the mobile satellite system industry shows a significant growth in the need for more demanding services and higher rates these last years; as an example, recent success of hybrid broadcasting system (XM, Sirius) and DVB-SH arrival are meeting commercial users expectations in terms of high rates mobile communications. In this context, the use of diversity and MIMO schemes (cyclic delay diversity and Alamouti) is studied in this paper in the aim of increasing reliability of interactive systems which don't take benefit of very long interleaving time durations (as pure broadcasting systems). Simulations have been done on a DVB-SH physical layer adapted to support 1×1, 1×2, 2×1, 2×2 multiplexing schemes. Satellite mobile MIMO channels have been used. This paper presents combinations of diversity/MIMO architectures, interleaving durations, channels, and makes the trade off of the air interface adjustment regarding of the results. View full abstract»

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  • Study on routing protocol for WSNs based on the improved Prim algorithm

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (241 KB) |  | HTML iconHTML  

    In wireless sensor networks, the size of backbone network have a great impact on communication overhead, as well as the network lifetime. It can be designed based on cluster tree. MIS (maximum independent sets) composed of clusterheads is achieved by clustering algorithm, based which MCDS(minimal connected dominating sets) and MST(minimum spanning tree) are built with improved Prim algorithm, and construct backbone network. Besides that, the maintenance and update algorithm of spanning tree is also given. In the end, simulation analysis proves the efficiency of the proposed algorithm. View full abstract»

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  • A new beam-forming algorithm based on flank acoustic vector-sensor array sonar

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1237 KB) |  | HTML iconHTML  

    An algorithm of Bartlett beam-forming with null-forming weights is proposed based on acoustic vector-sensor array, which is located on or near the flank shell of a ship. The influence of shell's reflection to the spatial spectrum estimation is analyzed. The performance of this algorithm is examined in two simulation examples. It can suppress effectively one or several coherent noise sources from aft part of the ship. It gives high bearing resolution and results in left-right unambiguous DOA estimation in all directions. Furthermore, it won't cause grating lobes if space under-sampling took place and, hence, is very useful in practical engineering. View full abstract»

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  • UPF algorithm and its application in the GPS/INS integrated navigation

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (137 KB) |  | HTML iconHTML  

    The integration of position and velocity is commonly adopted for observation model in GPS/INS integrated navigation system. But the navigation accuracy of this system is decreased by the correlation between the system's measurements. So the pseudo-range of the original measurements of GPS was adopted for observation model to eliminate the correlation. To reduce the linearization error, the unscented particle filter (UPF) was introduced to estimate the system states. The simulation was carried out under the condition of less than four GPS satellites data. The simulation results show that the estimated values with UPF method are quite close to the real values and the estimation error is much smaller than the inherent error of GPS. Both the figures and the statistical results prove that the UPF method present high navigation accuracy when employed in GPS/INS integrated navigation system. View full abstract»

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  • MMSE equalization of OFDM/OQAM systems for channels with time and frequency dispersion

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1431 KB) |  | HTML iconHTML  

    An MMSE per channel fractionally spaced equalizer is developed for an OFDM/OQAM system with a time varying channel, under the assumption of perfect channel knowledge at the receiver. The equalizer is analyzed for an example with a doubly dispersive channel with Jakes Doppler spectrum and an exponential delay profile, and where the transmitter and receiver filters are square root of cosine rolloff. The performance is measured in terms of ergodic channel capacity, which will be an upper bound for the throughput of the system, assuming perfect channel estimation and ideal channel coding. The results show that the channel capacity may be significantly increased by using an equalizer of finite length, instead of a one-tap equalizer. The channel capacity is for instance increased by 60% for Es/N0 = 20 dB in a channel with spreading factor 0.01. View full abstract»

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  • Research and design of EMI digital filters using scattering parameters

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB) |  | HTML iconHTML  

    Electromagnetic interference (EMI) filters are treated much as the effective equipments for controlling EMI. However, traditional EMI filter design methods are difficult, because the measurements of impedances are not easy due to the existences of parasitic parameters. In this paper, EMI filters are modeled by scattering parameters(S-parameter.) The paper also gives EMI digital filter design methods using S-parameters. Simulation is carried out to verify this design approach. After filtering, the conducted EMI produced by a DC/DC converter can meet the standard of GJB151A-91/CE102. The approaches here are very useful for the design and definition of EMI filters. View full abstract»

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  • An improved 8~32kbps embedded speech codec based on ITU-T EV-VBR candidate codec

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (178 KB) |  | HTML iconHTML  

    A candidate codec for ITU-T Embedded Variable Bit Rates (EV-VBR) standardization designed by Speech and Audio Signal Processing Laboratory (SASPL) of Beijing University of Technology is improved in this paper. In the improved codec, the second sub-frame's spectral parameters are quantized additionally to improve the overall quantization precision. Depth-first tree search algorithm replaces the full search and focus search in searching algebraic codebook. Transformation coding (TCX) process is redesigned and applied into the higher three layers which reduces the algorithm complexity dramatically. The objective mean opinion score (MOS) test results show that the improved codec achieves comparable speech quality as G.718 recommendation codec in most test items and has a lower algorithm delay. View full abstract»

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  • DLDCA: A distributed link-weighted and distance-constrained channel assignment for single-radio multi-channel wireless mesh networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (130 KB) |  | HTML iconHTML  

    In this work, we consider a distributed link-weighted and distance-constrained channel assignment (DLDCA) algorithm for a multi-channel multi-hop mesh network, such as community wireless networks, to maximize its throughput. Efficient channel assignment could greatly reduce interference of each link from its neighboring links and subsequently improve the network throughput. In response to it, we introduce an interference metric, namely, Min-Max I-value of an edge (MMIE), to explicitly accounts for interference among links that are at distance one. In addition, we further show that the above problem with respect to MMIE is NP-hard in computation. This guides us to develop a new distributed channel assignment algorithm called DLDCA algorithm. We study the DLDCA performance by implementing it in a wireless simulation environment. The simulation results show that in a multi-channel multi-hop network, DLDCA significantly outperforms previously proposed channel assignment schemes. View full abstract»

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  • A greedy-based resource allocation algorithm for multicast and unicast services in OFDM system

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB) |  | HTML iconHTML  

    We propose a resource allocation algorithm for OFDM system to provide QoS guarantee for unicast and multicast service concurrently. The optimization objective is to maximize the sum rate of the unicast service under the constraint of both the total power and the minimal rate provision of the multicast service, which can be solved by traditional two-step approach. To decrease the complexity, a greedy-based algorithm is proposed. According to the theoretical analysis and the simulation results, the performance of the proposed algorithm is close to the two-step approach meanwhile the complexity is effectively decreased. In conclusion, the proposed algorithm can balance the performance and the complexity well and so is suitable to be applied to practical scenario. View full abstract»

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  • Genetic algorithm in the design of thinned arrays with low sidelobe levels

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (887 KB) |  | HTML iconHTML  

    This paper discusses the problem of designing thinned linear and planar arrays with low peak sidelobe levels. It is concluded that the near-optimal method known as simulation is genetic algorithm. We see that genetic algorithm performs better on this synthesis problem by comparing the simulation results of uniform random arranged arrays (URA) and give a necessary analysis. View full abstract»

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  • Two-stage blind adaptive multiuser detection algorithm for DS-CDMA UWB in ISI channels

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (279 KB) |  | HTML iconHTML  

    Ultra wide-band (UWB) communication has to face two problems of multi-access interference (MAI) under multiple access scenario and intersymbol interference (ISI) in multipath environment. In this paper, we proposed a blind adaptive multiuser detection algorithm for direct-sequence code division multiple access (DS-CDMA) UWB systems in ISI channel, called two-stage algorithm, which consists of two stages. The first one jointly suppresses MAI and equalizes ISI to estimate multipath components of received symbol based on constrained minimum output energy (CMOE) criterion. The second combines these multipath components adaptively to achieve multipath diversity. Simulation results demonstrate that the proposed algorithm can effectively suppress MAI and equalize the ISI at the same time. View full abstract»

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  • Cross-layer optimization of wireless multi-hop networks with network coding

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB) |  | HTML iconHTML  

    In this paper we present a cross-layer algorithm for joint optimization of congestion control, routing, and scheduling in wireless multi-hop networks with network coding. We introduce virtual flow variables in the formulation of capacity region of the networks. The utility maximization problem subject to constraints on the capacity region is solved using dual decomposition and subgradient method, based on which a new queuing model is obtained and which also can result in a cross-layer algorithm for distributed implementation. The new queuing model can facilitate coding operations and reduce coding complexity. Simulation results show that network coding in the proposed joint optimization algorithm can interact adaptively and optimally with other components in different layers, and thus yield higher performance than the routing scheme without network coding. View full abstract»

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  • Study on signal acquisition algorithm of laser communication at sea

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (370 KB) |  | HTML iconHTML  

    According to the characteristics of laser communication at sea, we propose a sort of step scanning acquisition method for maritime communication. Comparing with traditional continuous scanning method, it can get velocity, high sensitivity and large acquisition range. The proposed acquisition method is based on Yang's noisy model. Through quadrant devices, we processed the acquisition signal and set up QD model. From the simulation result of RBF neural network, we find only few errors exist. View full abstract»

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  • Block Turbo Coded OFDM scheme and its performances for UAV high-speed data link

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (430 KB) |  | HTML iconHTML  

    We investigate the case of Block Turbo Codes (BTCs) combined with Orthogonal Frequency Division Multiplexing (OFDM) technique for Unmanned Aerial Vehicles (UAVs) highspeed data link. Considering the UAV channel with time-varying and multipath fast fading characteristics, a 3-path UAV channel model is developed, which can be readily implemented under simulation condition. Two typical communication scenarios are studied in the basis of various UAVs flight situations. Simulations are conducted to evaluate the BER performances of BTC-OFDM over UAV channel. Comparisons among convolutional coded OFDM, turbo coded OFDM and the proposed scheme are also provided. Numerical results show that BTC-OFDM scheme can serve as an optimal solution for UAV high-speed data link even in the worst scenario. View full abstract»

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  • Improved particle swarm optimization algorithm based cross-layer power allocation scheme in distributed antenna systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB) |  | HTML iconHTML  

    A cross-layer power allocation scheme for distributed antenna systems is proposed in this paper. From a cross-layer perspective, system throughput coefficient and fairness coefficient are defined taking into consideration both queue state information in data-link layer and channel state information in physical layer. Particularly, an improved particle swarm based optimization algorithm is proposed to solve the proposed optimization problem. Simulation results show that improved particle swarm optimization algorithm can obtain lower queue delay. System throughput and fairness performance obtained by the proposed algorithm increase considerably compared with those by fixed power allocation algorithm. View full abstract»

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  • Multi-service QoS guaranteed based downlink cross-layer resource block allocation algorithm in LTE systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (233 KB) |  | HTML iconHTML  

    A sub-optimal multi-service quality-of-service (QoS) guaranteed resource block allocation algorithm for downlink LTE system is proposed in this paper. Its key features are that all users are classified into three categories according to their channel state information in physical layer and queue state information in data-link layer. Then proposed scheduler assigns resource blocks to predefined three user categories in turns. Numerical results demonstrate that the proposed algorithm reduces the data loss rate considerably and improves the resource exploitation rate meanwhile user QoS requirement is ensured. For a densely populated system, the proposed scheme shows a graceful degradation, possibly leading to a high average user satisfaction. View full abstract»

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  • A novel printed monopole antenna for dual-band WLAN application

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (413 KB) |  | HTML iconHTML  

    A novel dual-band microstrip antenna for WLAN applications is proposed. The antenna fed by a 50 ¿ microstrip line. The configuration is simple. The lower and higher resonant frequencies can be easily tuned by adjusting a few antenna parameters. HFSS is used to simulate and optimize this antenna. The requirement of the model is achieved to practical application. This antenna satisfies the requirements of wireless local area network (WLAN) 802.11b/g and 802.11a applications. View full abstract»

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