By Topic

Wireless Communications, Networking and Mobile Computing, 2006. WiCOM 2006.International Conference on

Date 22-24 Sept. 2006

Filter Results

Displaying Results 1 - 25 of 410
  • Copyright - WiCOM2006

    Page(s): 1
    Save to Project icon | Request Permissions | PDF file iconPDF (62 KB)  
    Freely Available from IEEE
  • Welcome

    Page(s): 1 - 2
    Save to Project icon | Request Permissions | PDF file iconPDF (25 KB)  
    Freely Available from IEEE
  • Committees-WiCOM2006

    Page(s): 1 - 3
    Save to Project icon | Request Permissions | PDF file iconPDF (26 KB)  
    Freely Available from IEEE
  • A Novel Wideband MIMO Channel Model and the Wideband MIMO Software Defined Radio

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (339 KB) |  | HTML iconHTML  

    In the following, we present a novel wideband multiple-input, multiple-output (MIMO) channel model. The model is based on the eigenvalue decomposition (EVD) of the wideband channel correlation matrix. It does not assume the scatterers at the receiver fade independently of those at the transmitter. It also models correlation between delay bins in the power delay profile (PDP). With preliminary data gathered using the Wideband MIMO software defined radio (WMSDR) in fixed outdoor locations, we show good agreement between modeled and measured data View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Correlation Effects and Channel Capacities for MIMO Polarization Diversity

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (659 KB) |  | HTML iconHTML  

    In consequence of the high demand for high transmission data rates in the outdoor and indoor environment, an exploitation of multiple-input multiple output (MIMO) systems appears recently. The MIMO channel is obviously characterized by antenna configuration and propagation environment. The antenna configuration is responsible mainly for the antenna correlation effect which can be reduced by increasing antenna array spacing or by employing multi-polarized antenna arrays. In this paper, we assume that all scatterers are uncorrelated, independent and identically distributed (i.i.d). In addition we investigate the channel capacity of single, dual and triple polarized dipole antennas compared with omni-vertical and omni-horizontal antennas with various solid angles based on 2times2 and 3times3 MIMO systems. The results of simulations illustrate that a combination of angular and polarization diversities can be exploited to increase the transmission performance View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the MIMO Channel Capacity Saturation for Spatially Constrained Multielement Antenna Systems

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (254 KB) |  | HTML iconHTML  

    In MIMO wireless communication systems, when more and more antennas are packed into a limited space, the antenna saturation phenomenon will appear. Moreover, the electromagnetic interactions among antennas will also become stronger and stronger and affect the antenna saturation effect considerably. Despite this, few studies consider these two effects jointly. Here, the effects of antenna saturation and mutual coupling are investigated jointly, thus a more practical result can be obtained View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Capacity Enhancement Scheme for Downlink Multiuser MIMO Systems with Limited Feedback

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (125 KB) |  | HTML iconHTML  

    Many precoding schemes in downlink multiuser MIMO systems require perfect channel state information of all users at the transmitter, which is hard to realize in practical systems. Random beamforming scheme is a conventional method to reduce the amount of feedback. However, it only enjoys significant performance gains with a large number of users, which limits its practical application. We propose a limited feedback capacity enhancement scheme based upon Grassmannian beamforming for downlink multiuser MIMO systems. In order to get better performance when users with multiple receive antennas we also propose a MMSE based scheme to further eliminate multi-user interference. The proposed scheme outperforms conventional random beamforming scheme when the number of users is small or moderate View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Impacts of Gaussian Error and Doppler Spread on the Performance of MIMO Systems with Antenna Selection

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (241 KB) |  | HTML iconHTML  

    Recently, the antenna selection (AS) scheme is a hot topic in the region of multiple-input multiple-output (MIMO) systems, due to lower complexity. In the previous research, it is assumed that the channel state information (CSI) is available at the receiver, which, however, is impractical in the wireless transmission environment. During the process of the channel estimation, there exists two-aspect impacts, namely Gaussian errors and Doppler spread, which are caused by Gaussian noise and the speed of mobile, respectively. In this paper, we analyze the performance of AS systems with the imperfect CSI, caused by Gaussian errors and Doppler spread, and derive the exact bit-error-ratio (BER) expression of AS systems in Rayleigh fading channel, using space-time coding transmission scheme. The corresponding simulations are carried out to illustrate the impacts of Gaussian errors and Doppler spread on the performance of AS systems and to prove the theoretical analysis. The results show that the length of pilot symbols needs a tradeoff under this environment with Doppler spread and Gaussian errors View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Hybrid Zero-Forcing and Sphere-Decoding Method for MIMO Systems

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (371 KB) |  | HTML iconHTML  

    In this paper, we describe a hybrid ZF-SD (zero-forcing and sphere decoding) algorithm. The basic idea is to reduce the dimensionality of decoding via pre-decoding and cancellation of those symbols that can be quickly and reliably detected. The proposed algorithm shows the BER performance similar to SD (sphere decoding) but with very lower computational complexity than SD View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Turbo Receiver for MIMO CDMA in Flat Fading Channel

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (295 KB) |  | HTML iconHTML  

    In this paper a multiple-input multiple-output (MIMO) (G.J. Foschini and M.J. Gans, 1998) CDMA system that employs space-time turbo codes is considered to enhance the system capacity. The turbo receiver introduced is able to combat the complicated interference mixture in this system. To evaluate the performance of the turbo receiver this paper focus on the performance analysis on the synchronous flat fading channel View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A New Detection Scheme for MIMO-BLAST Systems

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (217 KB) |  | HTML iconHTML  

    The VBLAST architecture has been proposed as an extremely spectral efficient tool for wireless communications. However, owing to the error propagation, the performance of VBLAST is constrained by the accuracy of the symbols recovered in the previous layer when the traditional detection successive interference cancellation (SIC) algorithm is applied. The performance of VBLAST depends on the performance of the first detected layer. So we proposed a new scheme that the first layer is detected with iterative method and others layers is detected using parallel interference cancellation (PIC) detection. . The proposed algorithm reduces the error propagation, and the performance of the first detected layer is improved. Simulation result states that proposed scheme outperform to MMSE-VBLAST about 1.6 dB at 10-3 BER for first detected layer View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Blind Channel Estimation for MIMO Uplink MC-CDMA Systems with Layered Space Frequency Equalisation

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (125 KB) |  | HTML iconHTML  

    In this paper, we investigate blind channel estimation for multiple input multiple output (MIMO) multi-carrier CDMA (MC-CDMA) systems in the uplink scenario. An autocorrelation contribution matrix (ACM) method is proposed in comparison with the subspace approach. Using only second order statistics, the ACM approach shows similar performance to that of subspace based approach. The added advantage is that it eliminates the need for rank estimation and noise power calculation as in subspace technique. In particular we incorporate blind channel estimation with layered space frequency equalisation (LSFE),which employs successive interference cancellation and therefore provides significant performance improvement over the conventional linear minimum mean square error (MMSE) based approach View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Opportunistic Spatial Multiuser Diversity when Transmitter has More Antennas in Downlink

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (218 KB) |  | HTML iconHTML  

    MIMO can enhance the performance of wireless system greatly. However, the limited battery life and terminal size of the UE in a cellular system put a constraint on the performance enhancement from MIMO. Especially when the transmitter has more antenna than the receiver in downlink, the conventional MIMO schemes can only exploit partial spatial multiplexing gain and diversity gain. For different users' independent locations lead to independent spatial fading one another, adaptive spatial and temporal scheduling can be developed to exploit the spatial multiuser diversity and achieve the tradeoff between multiplexing gain and spatial diversity gain available. In this paper, the enhanced MIMO schemes with greedy multiuser diversity are compared when Node B has more antenna than UE, e.g. zero forcing beamforming (ZFB), dual space time block coding (DSTBC), singular value decomposition (SVD) and vertical Bell labs layered spatial time code plus antenna selection (VBLAST-AS). From the simulation results, the ZFB has achieved the best spectrum efficiency, and the gain exceeds VBLATS-AS and DSTBC more than 50% View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimal Linear Precoder Design for Space-Time Block Coded Systems

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (209 KB)  

    Taking the pairwise error probability (PEP) as the performance criterion and exploiting the channel covariance information at the transmitter, this paper studies the optimal linear precoder design of the correlated multiple-input multiple-output (MIMO) wireless system. The precoder can be used along with any space-time block codes (STBC), which is an extension of Y. Zhao et al. (2004) . The optimal beamforming direction of the precoder is proved to match the structure of STBC and transmit correlation matrix. The optimal power allocation scheme is related to transmit correlation matrix, receive correlation matrix and STBC. The quasi-orthogonal space-time block codes (QSTBC) is taken as an illustration to investigate the performance of the optimal precoder View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The Performance Analysis of Non-Primitive Turbo Codes in MIMO System Over Flat Fading Channel

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB) |  | HTML iconHTML  

    So far almost all the research work on turbo codes focus on primitive turbo code (PTC). In multiple input multiple output (MIMO) system this paper concentrates on the research of non-primitive turbo code (NOPTC) over flat fading channel. It shows that NOPTC outperforms PTC at any size SIR. Thus NOPTC promotes both capacity and reliability of the communications in MIMO system. This paper concludes as well there is no direct proportion between the state-number and the BER performance of turbo code View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Channel Design: A Novel Approach for Blocking Interference and Achieving Interference-Free Capacity

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (210 KB) |  | HTML iconHTML  

    The topics of lifting the capacity and blocking the interferences of MIMO wireless systems are studied. The interferences can be blocked by filter design but with the consequence of noise enhancement and thus reduce the capacity. Or, the capacity can be maintained by filter design but some interference has to be accepted. In this paper, we present a new method, namely channel design, with which the interferences can be completely blocked and in the meantime the capacity is also lifted View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fast Antenna Subset Selection Algorithm for MIMO Wireless Systems

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (205 KB) |  | HTML iconHTML  

    Multiple-antenna wireless communication systems have recently attracted significant attention due to their higher capacity and better immunity to fading as compared to systems that employ single-sensor transceiver. Increasing the number of transmit and receive antennas enables to improve system performance but at the price of higher hardware cost and computational burden due to the multiple RF chains. Antenna selection is a low-cost low-complexity alternative to capture many of the advantages of MIMO systems. In this paper, we propose a new antenna selection algorithm with low complexity for wireless multiple-input multiple-output (MIMO) systems. The new algorithm is based on the analysis of the channel capacity. It achieves almost the same outage capacity as the optimal selection method while keeping lower computational complexity. The simulation results for quasi-static Rayleigh flat fading channel demonstrate the significant performance of the proposed selection algorithm View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Novel Detection Algorithm Using the Sorted QR Decomposition Based on Log-Likelihood Ratio in V-BLAST Systems

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (155 KB) |  | HTML iconHTML  

    In this paper, we propose a novel detection algorithm using log-likelihood ratio (LLR) to detect signals in V-BLAST systems. This algorithm utilizes the sorted QR decomposition (SQRD) of the channel matrix, and applies LLR to determine the order of detection. Simulation results show that the proposed algorithm provides a better performance than the conventional SQRD with a few additional computations. Approximately, the average BER performance of our algorithm is better than that of the conventional SQRD algorithm by 6 dB for BPSK and by 2 dB for QPSK respectively at 10-3 target BER View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A New Reduced-Complexity ML Joint Detection Algorithm Based Sphere Decoder for LS-CDMA System

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (286 KB) |  | HTML iconHTML  

    A new reduced-complexity joint detection algorithm based on sphere decoder for LS-CDMA system is proposed in this paper. This algorithm can approach ML performance in polynomial complexity. Special zero correlation window property of LS code can reduce complexity of this algorithm greatly. Simulation indicates it is more insensitive to the choice of initial radius. Thus, by making the choice of radius sufficiently large, the ML solution is guaranteed with low complexity, even for large constellations. We then extend this joint detection algorithm to MIMO case and compare it with MMSE, ZF multicode detectors. Numerical results show performance of this algorithm is good even at very high speed such as 160 Km/h, this give us some insights on developing high efficient practical joint detection algorithm for further LS-CDMA system View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance Analysis of a New MIMO Transmit Scheme

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB) |  | HTML iconHTML  

    In order to improve system performance and reduce receiver hardware complexity and cost, we investigate a new multiple-input multiple-output (MIMO) scheme combining maximal-ratio transmit and receiver antenna selection combining (the MRT/RAS scheme). In this scheme, a single receive antenna, which maximizes the received signal-to-noise (SNR) at the receiver, is selected for demodulation. The closed-form outage probability and the bit error rate (BER) of the MRT/RAS system are presented. The simulation demonstrates that the MRT/RAS scheme can achieve a full diversity order, as if all the receive antennas were used. It is shown that the TAS/MRC scheme outperforms some more complex space-time codes of the same spectral efficiency. The analytical results are verified by simulation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Pairwise Ordered Successive Interference Cancellation Algorithm for VBLAST

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB) |  | HTML iconHTML  

    The classic detection algorithm of VBLAST, OSIC (ordered successive interference cancellation), is a good compromise between performance and complexity comparing to the optimum ML (maximum likelihood) algorithm. Due to the error propagation, the detection errors in the previous stages would degrade the accuracy of the forthcoming stages' detection and the overall performance of OSIC. We propose, in this paper, an POSIC (pairwise OSIC) algorithm aiming at reducing the errors in each detection stage and the numbers of the stages in the detection process to diminish the error propagation. Instead of detecting one substream in each stage, the POSIC algorithm using ML to jointly detect two strongest sub streams in each stage and then eliminate the contribution of the detected substreams from the received signals until all the transmitted substreams were detected View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The Relation of Channel Estimation Error Parameters and System Capacity in MIMO CDMA System

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (202 KB) |  | HTML iconHTML  

    Pilot length and interval, velocity, the number of transmitting and receiving (TR) antenna numbers are the main parameters of the interpolation channel estimation error in MIMO CDMA system. Above parameters also influence on the MIMO CDMA system capacity. It analyses the relation of above parameters and the channel estimation error with system capacity. When the other parameters are fixed, simulation results show that optimal pilot interval decreases as the velocity increasing; with a fixed velocity, the system performance improves as the TR antenna numbers increasing; with low velocity, the optimal pilot interval increases with the number of TR antennas increasing; it decreases with high velocity. When the channel estimation error is smaller than one percent, the system capacity is increasing with the TR antenna numbers. When it is larger than ten percent, it does not increase nearly View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ordered Group Interference Cancellation for Quasi-Orthogonal Space Time Block Codes

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (205 KB) |  | HTML iconHTML  

    We consider a multiple input and multiple output system with quasi-orthogonal space time block codes. Quasi-orthogonal space time block code (QOSTBC) is greatly used because it can achieve a good tradeoff between diversity and multiplexing. However, since the transmit code is not orthogonal, there exists interantenna interference at the receiver. By studying the post detection SNR of transmit symbols at each detection step of ordered interference cancellation (OSIC), we propose an ordered group interference cancellation (OGIC) at reduced complexity. Simulation results show that the proposed method can achieve near the performance of OSIC View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On Capacity of Multiple Antenna LS-CDMA System in Ricean Fading Channel

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (255 KB) |  | HTML iconHTML  

    We considered the effects of Ricean fading and suboptimum multicode detector on capacity of MIMO LS-CDMA system. Suboptimal multicode detector's behavior is very different in different Ricean channels and the loss of capacity incurred by it is also different. When Ricean channel is friendly, performance of suboptimal multicode detector can approach that of optimal multicode detector rapidly as K-factor increases. On the other side, the loss of capacity incurred by suboptimal detector is huge when K-factor increases. This result gives guideline in the development of practical wideband MIMO-CDMA system based on LS code View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • rms Angular Spread Estimation Using CDM Based MIMO Channel Sounder with Loosely Synchronous Codes and Kasami Codes

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB) |  | HTML iconHTML  

    This paper presents rms angular spread estimation using the code-division multiplexing (CDM) based MIMO channel sounder applied loosely synchronous (LS) codes and Kasami codes for real time measurement of MIMO radio channel. Since this scheme has drawback of reduced dynamic range depending on the number of transmit antennas, it is important that low correlation codes should be utilized to get reliable performance. In this paper, the proposed scheme adopts two efficient codes, LS codes and Kasami codes, of which performance is investigated through Monte-Carlo simulation in 2 times 8 and 4 times 8 MIMO channel environment, respectively. According to the simulation focused on rms angular spread estimation, LS codes can be used for 2times8 MIMO channel measurement and Kasami codes is suitable for measuring 4times8 MIMO channel. For measuring 4times8 MIMO channel with LS codes properly, some modification is taken to the LS codes. Unitary ESPRIT is chosen for DOA estimation and rms angular spread is taken for the performance comparison View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.