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Wireless Communications, IEEE Transactions on

Issue 10 • Date October 2007

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  • IEEE Transactions on Wireless Communications - Table of contents

    Page(s): c1 - c4
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  • 3-d localization error analysis in wireless networks

    Page(s): 3472 - 3481
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (187 KB) |  | HTML iconHTML  

    In the paper we investigate 3-D positioning by making use of distance/range and angle-of-arrival (AOA) measurements. Two estimation methods (linear least squares (LS) estimator and optimization) are developed for node positioning in wireless networks. We derive the Cramer-Rao lower bound (CRLB) for positioning with both range and AOA measurements in a 3-D environment, which is not seen in the literature. Also we derive compact approximate expressions of the variances of the LS algorithms. In the literature, positioning accuracy is usually studied by assuming perfect anchor location information. To evaluate positioning accuracy under realistic conditions, we also analyze the impact of anchor position error. Numerical results demonstrate that the derived analytical results have a good match with the simulated results. View full abstract»

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  • Cross-Layer Design for End-to-End Throughput and Fairness Enhancement in Multi-Channel Wireless Mesh Networks

    Page(s): 3482 - 3486
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    In this paper, we study joint rate control, routing and scheduling in multi-channel wireless mesh networks (WMNs), which are traditionally known as transport layer, network layer and MAC layer issues respectively. Our objective is to find a rate allocation along with a flow allocation and a transmission schedule for a set of end-to-end communication sessions such that the network throughput is maximized, which is formally defined as the maximum throughput rate allocation (MRA) problem. As simple throughput maximization may result in a severe bias on rate allocation, we take account of fairness based on a simplified max-min fairness model and the proportional fairness models. We define the max-min guaranteed maximum throughput rate allocation (MMRA) problem and proportional fair rate allocation (PRA) problem. We present efficient linear programming (LP) and convex programming (CP) based schemes to solve these problems. Numerical results show that proportional fair rate allocation schemes achieves a good tradeoff between throughput and fairness. View full abstract»

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  • Serially Concatenated Space-Time Coded Continuous Phase Modulated Signals

    Page(s): 3487 - 3492
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    We investigate the detection of space time codes (STC) modulated using continuous phase modulation (CPM), in quasi-static fading channels. A symbol-by-symbol iterative detector with an optimum front-end is derived, and its reduced-complexity implementation is considered. Also, we have introduced several full-rank STC-CPM systems, constructed by combining full-diversity STCs with simple, widely-used CPM schemes, and introducing a small frequency offset. According to the simulation results, the bit error rate (BER) performance of the detector for quasi-static fading is around 1 dB from the case without fading. Furthermore, a comparison of the performance of the proposed detector with results from previous work on STC-CPM showed an improvement in the range of 2-3 dB. Moreover, the detector is robust to the errors in estimating the channel state information (CSI), which is a desirable feature for practical implementation. View full abstract»

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  • A Technique for Multiuser and Intercarrier Interference Reduction in Multiple-Antenna Multiuser OFDM Downlink

    Page(s): 3493 - 3497
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    We propose a two-stage precoder/equalizer to suppress intercarrier interference (ICI) and multiuser interference (MUI) in downlink multiuser OFDM with multiple transmit antennas. The first stage, non-linear Tomlinson-Harashima preceding (THP) at the base station (BS) transmitter, mitigates the effect of the spatial inter-stream interference caused by transmission from multiple transmit antennas to decentralized users. In the second stage, each user's receiver employs low- complexity iterative linear minimum mean-square error (MMSE) equalization to suppress the ICI due to frequency offset. Our proposed technique virtually eliminates the bit error rate (BER) degradation due to normalized frequency offsets as high as 10%. View full abstract»

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  • Robust Downlink Beamforming Based on Outage Probability Specifications

    Page(s): 3498 - 3503
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    A new approach to multi-antenna downlink beam- forming is proposed that provides an improved robustness against uncertainty in the downlink channel covariance matrices caused by errors between the actual and estimated channel values. The proposed method uses the knowledge of the statistical distribution of such a covariance uncertainty to minimize the total downlink transmit power under the constraint that the outage probability does not exceed a certain threshold value. Although our approach initially leads to a non-convex optimization problem, it can be reformulated in a convex form using the semidefinite relaxation technique. The resulting convex optimization problem can be solved efficiently using the well-established interior point methods. Computer simulations verify performance improvements of the proposed technique as compared to the robust transmit beamforming method based on the worst-case performance optimization with judicious selection of the upper bounds on channel covariance errors. View full abstract»

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  • A Unified Exact BER Performance Analysis of Asynchronous DS-CDMA Systems Using BPSK Modulation over Fading Channels

    Page(s): 3504 - 3509
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (231 KB) |  | HTML iconHTML  

    An asynchronous binary DS-CDMA system using random spreading sequences is considered when communicating over various fading channels. New closed-form expressions are derived for the conditional characteristic function (CF) of the multiple access interference. A unified analysis is provided for calculating the exact average bit error rate (BER) expressed in the form of a single numerical integration based on the CF approach. The numerical results obtained from our exact BER analysis are verified by our simulation results and are also compared to those obtained by the standard Gaussian approximation (SGA), confirming the accuracy of the SGA for most practical conditions, except for high signal-to-noise ratios (SNR) and for a low number of interferers. View full abstract»

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  • Inter-Frame, Fine Frequency/Phase Synchronization forSimple Space-Time-Coded OFDM Receivers

    Page(s): 3510 - 3514
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    This paper proposes an enhanced receiver (Rx) configuration for multiple-input, multiple-output (MIMO) OFDM systems, operating under the composite effect of phase noise (PHN), residual frequency offset (RFO) and the transmission channel, herein modeled as quasi-static but unknown. The proposed Rx identifies the different impairments by exploiting their different time constants and compensates for each one accordingly. It includes a novel inter-frame fine frequency synchronization (FFS) scheme, which is closely coupled to an intra-frame adaptive phase synchronizer/channel estimator. The proposed scheme is evaluated for a 2 times 2, Alamouti space-time code (STC), and is shown to provide significant performance gain. The theory can be employed with any other STC scheme. View full abstract»

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  • Outage Probabilities of Wireless Systems with LCMV Beamforming

    Page(s): 3515 - 3523
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (325 KB) |  | HTML iconHTML  

    This paper investigates the outage probability of a wireless system with linear constrained minimum variance (LCMV) beamforming using a uniform linear array beamformer. LCMV beamforming is able to perfectly cancel a number of dominant interferers while other interferers remain. A simplified beamforming model is used to derive closed-form outage probability expressions considering the impact of LCMV beam patterns on various interferers. Fading statistics of Rayleigh, Rician, and Nakagami are used to characterize the desired signal, whereas interferers are assumed to be subject to Rayleigh fading. One important aspect of this paper is the consideration of the directions of arrivals (DOA) of the dominant interferers and the exact beam patterns in the outage performance evaluations of LCMV beamforming systems. Numerical results of the outage probability are presented to illustrate the impact of DOA's of the dominant interferers and the impact of different fading scenarios. The paper also presents performance comparison between LCMV beamforming and conventional beamforming considering different interference scenarios (DOA's of dominant interferers). View full abstract»

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  • Combined Selective Mapping and Binary Cyclic Codes for PAPR Reduction in OFDM Systems

    Page(s): 3524 - 3528
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (237 KB) |  | HTML iconHTML  

    In this paper, we consider reduction of PAPR in OFDM systems with BPSK subcarriers by combining SLM and binary cyclic codes. This combining strategy can be used for both error correction and PAPR reduction. We decompose a binary cyclic code into direct sum of two cyclic subcodes: the correction subcode used for error correction and the scrambling subcode for PAPR reduction. The transmitted OFDM signal is selected that achieves minimum PAPR, from the set of binary cyclic codewords. The received signal can be easily decoded without the need of any side information. Simulations show that the proposed scheme with simplex code as scrambling subcode achieves good PAPR reduction. View full abstract»

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  • Scaling of Spatial Reuse and Saturation Throughput in a Class of MAC Protocols

    Page(s): 3529 - 3533
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    In this paper, we investigate the spatial reuse and saturation throughput of static ad-hoc networks with unbiased medium access control (MAC) protocols. Under the stochastic assumptions of our model, we obtain the upper bound on the equivalent saturation throughput of such MAC protocols as a function of node density. We also obtain the scaling properties of the spatial reuse and saturation throughput. View full abstract»

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  • Symmetry-Embedded Spreading Sequences for Multicarrier CDMA

    Page(s): 3534 - 3539
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (380 KB) |  | HTML iconHTML  

    It was shown by Slimane that the bit error rate (BER) performance of the downlink of multicarrier code-division multiple-access (MC-CDMA) systems can be improved significantly by employing quadrature spreading sequences instead of binary Walsh-Hadamard sequences. Inspired by Slimane's work, we propose a class of complex-valued spreading sequences, which are mathematically derivable from the Kronecker product of some basic matrices. The good algebraic structure in the proposed spreading sequences, when applied in a BPSK based MC-CDMA system, can be exploited for multiple access interference (MAI) suppression, for order-2 diversity combining, and for the reduction of peak-to-average power ratio. The new spreading sequences outperform the Slimane's quadrature sequences, as evidenced by various numerical results. View full abstract»

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  • Sum of Squared Shadowed-Rice Random Variables and its Application to Communication Systems Performance Prediction

    Page(s): 3540 - 3545
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (233 KB) |  | HTML iconHTML  

    The distribution of the sum of non-negative random variables plays an essential role in the performance analysis of diversity schemes for wireless communications over fading channels. While for common fading models such as the Rayleigh, Rice, and Nakagami, the performance of diversity systems is well understood, a minor attention has been devoted to the shadowed-Rice (SR) case, namely a Rice fading channel with fluctuating (e.g. random) Line of Sight (LOS) component. Indeed, the analytical performance evaluation of diversity systems on SR fading channels requires the availability of handy expressions for the distribution of the combined received power. To this end, the rationale of this paper is twofold: first, to evaluate the distribution of the sum of SR random variables, both for the case of independent as well as correlated LOS components, and then to carry out an extensive performance analysis of maximal ratio combining (MRC) detection scheme on SR fading channels. View full abstract»

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  • Carrier Frequency Offset Compensation with Successive Cancellation in Uplink OFDMA Systems

    Page(s): 3546 - 3551
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (154 KB) |  | HTML iconHTML  

    Similar to OFDM systems, OFDMA systems also suffer from frequency mismatches between the receiver and the transmitter. However, the fact that each uplink user has a different frequency offset makes the compensation more challenging than that of OFDM systems. This letter proposes successive interference cancellation (SIC) for compensating the frequency offset in the uplink OFDMA systems. A decorrelator is used to remove the inter-carrier interference (ICI) within a user's signal and successive cancellation is applied to mitigate the multi access interference (MAI) arising due to the frequency difference among uplink users. The proposed algorithm is shown to eliminate the interference and has a manageable complexity. View full abstract»

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  • Design of Turbo-MUD Receivers for Overloaded CDMA Systems by Density Evolution Technique

    Page(s): 3552 - 3557
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (266 KB) |  | HTML iconHTML  

    This paper deals with a turbo multiuser detector suitable for applications in overloaded coded DS-CDMA systems. The turbo-MUD receiver is based on the use of a linear MMSE detector in the first iteration and a parallel interference cancellation scheme in the successive ones. The inputs of the interference cancellator are both the detector outputs and the soft information from a bank of turbo decoders. The performance of the proposed receiver has been derived by means of computer simulations and applications of the density evolution theory: in particular, this technique permits to properly evaluate the number of MMSE iterations, simplifying the overall receiver design. View full abstract»

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  • Rate-Distortion Optimized Video Transmission Over DS-CDMA Channels with Auxiliary Vector Filter Single-User Multirate Detection

    Page(s): 3558 - 3566
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (243 KB) |  | HTML iconHTML  

    In this paper, we consider the rate-distortion optimized resource allocation for video transmission over multi-rate wireless direct-sequence code-division-multiple-access (DS-CDMA) channels. We consider the performance of transmitting scalable video over a multipath Rayleigh fading channel via a combination of multi-code multirate CDMA and variable sequence length multirate CDMA channel system. At the receiver, despreading is done using adaptive space-time auxiliary-vector (AV) filters. We propose a new interference cancelling design that uses just a single AV filter for single-user mutirate despreading. Our experimental results show that the proposed interference cancelling design has excellent performance in scalable video transmission over DS-CDMA systems that use a combination of multicode multirate and variable processing gain multirate CDMA. The proposed design takes advantage of the fact that single user's video data is transmitted using two spreading codes, one for the base layer and one for the enhancement layers, and of the fact that these spreading codes can have different processing gains. The proposed interference cancelling design is compared with two conventional single-user multirate CDMA receiver configurations, however now we use an AV filter rather than a simple matched filter. We also propose a resource allocation algorithm for the optimal determination of source coding rate, channel coding rate and processing gain for each scalable layer, in order to minimize the expected distortion at the receiver. View full abstract»

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  • Performance Improvements of Mobile SCTP in Integrated Heterogeneous Wireless Networks

    Page(s): 3567 - 3577
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (337 KB) |  | HTML iconHTML  

    The complementary characteristics of cellular networks and wireless local area networks (WLANs) make it attractive to integrate these two technologies. In this integrated heterogeneous environment, mobile stream control transmission protocol (MSCTP) is ideal to support vertical handover (VHO) between them by enabling a mobile client to freely switch between IP addresses acquired in different networks. In this paper, we show that the MSCTP-based VHO scheme suffers from poor throughput performance during WLAN to cellular forced VHOs. We propose a novel error recovery scheme called Sending-buffer Multicast-Aided Retransmission with Fast Retransmission (SMART-FRX) to improve performance during VHO by multicasting the buffered and new data over both WLAN and cellular links when handover losses occur. In addition, we propose a new analytical model for SCTP that takes into account the congestion window, the round trip time, the slow-start and congestion avoidance processes. By comparing numerical results from the proposed analytical model with simulation results, we demonstrate that our analytical model is able to predict the SCTP throughput accurately, with or without the SMART-FRX scheme. The analytical model provides a useful tool that can be extended to study the performance of SCTP in other applications. Analytical and simulation results show that the proposed SMART-FRX scheme can improve the SCTP throughput performance significantly in WLAN to cellular forced VHO situations. View full abstract»

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  • Two-Stage Acquisition in Time-Hopping Impulse Radio Systems for UWB Communications

    Page(s): 3578 - 3588
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (293 KB) |  | HTML iconHTML  

    Ultra wideband impulse radio is a promising radio technology for networks delivering extremely high data rates at short ranges. The use of extremely short duration pulses however makes synchronization task more difficult. In this paper a two-stage acquisition with serial search noncoherent correlator for time hopping impulse radio is proposed. The proposed two-stage acquisition scheme gets chip timing synchronization, and aligns phase of the local time-hopping code in two stages successively. With the aid of flow-graph approach, the analytical expressions are presented for the mean acquisition time and the probability of acquisition. Numerical results in a slow fading channel show that the proposed two-stage acquisition method can offer much shorter mean acquisition time or much higher probability of acquisition than that of the conventional acquisition. View full abstract»

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  • Mobility Tracking in Cellular Networks Using Particle Filtering

    Page(s): 3589 - 3599
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (888 KB) |  | HTML iconHTML  

    Mobility tracking based on data from wireless cellular networks is a key challenge that has been recently investigated both from a theoretical and practical point of view. This paper proposes Monte Carlo techniques for mobility tracking in wireless communication networks by means of received signal strength indications. These techniques allow for accurate estimation of mobile station's (MS) position and speed. The command process of the MS is represented by a first-order Markov model which can take values from a finite set of acceleration levels. The wide range of acceleration changes is covered by a set of preliminary determined acceleration values. A particle filter and a Rao-Blackwellised particle filter are proposed and their performance is evaluated both over synthetic and real data. A comparison with an extended Kalman filter (EKF) is performed with respect to accuracy and computational complexity. With a small number of particles the RBPF gives more accurate results than the PF and the EKF. A posterior Cramer Rao lower bound (PCRLB) is calculated and it is compared with the filters' root- mean-square error performance. View full abstract»

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  • Utility-based resource allocation in wireless networks

    Page(s): 3600 - 3606
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (658 KB) |  | HTML iconHTML  

    In this paper, we study utility-based maximization for resource allocation in the downlink direction of centralized wireless networks. We consider two types of traffic, i.e., best effort and hard QoS, and develop some essential theorems for optimal wireless resource allocation. We then propose three allocation schemes. The performance of the proposed schemes is evaluated via simulations. The results show that optimal wireless resource allocation is dependent on traffic types, total available resource, and channel quality, rather than solely dependent on the channel quality or traffic types as assumed in most existing work. View full abstract»

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  • Joint and Marginal Eigenvalue Distributions of (Non)Central Complex Wishart Matrices and PDF-Based Approach for Characterizing the Capacity Statistics of MIMO Ricean and Rayleigh Fading Channels

    Page(s): 3607 - 3619
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (673 KB) |  | HTML iconHTML  

    This paper characterizes the eigenvalue distributions of full-rank Hermitian matrices generated from a set of independent (non)zero-mean proper complex Gaussian random vectors with a scaled-identity covariance matrix. More specifically, the joint and marginal cumulative distribution function (CDF) of any subset of unordered eigenvalues of the so-called complex (non)central Wishart matrices, as well as new simple and tractable expressions for their joint probability density function (PDF), are derived in terms of a finite sum of determinants. As corollaries to these new results, explicit expressions for the statistics of the smallest and largest eigenvalues, of (non)central Wishart matrices, can be easily obtained. Moreover, capitalizing on the foregoing distributions, it becomes possible to evaluate exactly the mean, variance, and other higher order statistics such as the skewness and kurtosis of the random channel capacity, in the case of uncorrelated multiple-input multiple-output (MIMO) Ricean and Rayleigh fading channels. Doing so bridges the gap between Telatar's initial approach for evaluating the average MIMO channel capacity (Telatar, 1999), and the subsequently widely adopted moment generating function (MGF) approach, thereby setting the basis for a PDF-based framework for characterizing the capacity statistics of MIMO Ricean and Rayleigh fading channels. View full abstract»

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  • Iterative Frequency Domain Joint-over-Antenna Detection in Multiuser MIMO

    Page(s): 3620 - 3631
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (452 KB) |  | HTML iconHTML  

    Multiuser multiple-input-multiple-output (MIMO) wireless systems have great potential in improving information rate, diversity and resistance to against interference. The primary objective of this paper is to derive for broadband signaling a new iterative frequency domain (FD) multiuser MIMO signal detection technique for joint-over-antenna (JA) detection. The proposed detector is based on soft-cancellation and minimum mean square error (MMSE) filtering, followed by maximum a posteriori probability (MAP) detector to detect several of each users transmit antennas. The purpose of jointly detecting several transmit antennas is to preserve the degrees of freedom (DoF) for MMSE. Computational complexities with FD and its time domain (TD) counterpart are evaluated in this paper, and it is shown that FD requires significantly lower complexity than TD. Numerical results show that JA significantly outperforms the receiver that detects transmit antenna signals antenna-by- antenna (AA). The proposed iterative FD JA technique achieves larger performance gains compared to AA when the total number of transmit antennas is larger than the number of receiver antennas, as well as in the presence of spatial correlation. View full abstract»

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  • Non-Blocking Pipeline Paging with Known Location Probabilities for Wireless Systems

    Page(s): 3632 - 3640
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (327 KB) |  | HTML iconHTML  

    Paging schemes for wireless systems have been well studied in the literature. However, most schemes are considered on per user basis. In these schemes, when an incoming call arrives at a mobile terminal (MT), a paging request (PR) is put in a queue. PRs are served in an FIFO manner. When a PR is served, a search process is carried out to find the corresponding MT in a location area (LA). Most schemes study how to achieve a better performance in terms of cost with/without delay constraints per PR, and totally ignore other PRs in the queue until the MT is found or all the cells in the LA have been paged. In this paper, we propose a non-blocking pipeline probability paging scheme, which assumes known knowledge on location probabilities of individual MTs, under a paging delay constraint, where the location probability of an MT in a cell is the probability that the MT is in the cell. The proposed scheme is independent of the number of PRs in the queue and the arrival rate of PRs. Our study shows that the proposed scheme outperforms both the sequential probability paging scheme with known knowledge on location probabilities of individual MTs and the blanket paging scheme in terms of discovery rate and the total delay. Finally, we study several optimization problems with quality of service constraint for the pipeline probability paging scheme. View full abstract»

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  • A Computationally Efficient QR-Successive Interference Cancellation Scheme for Simplified Receiver Implementation in SFBC-OFDM Systems

    Page(s): 3641 - 3647
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (238 KB) |  | HTML iconHTML  

    In this paper, we propose a computationally efficient square-root and division free recursive QR (SDRQR) decomposition based successive interference cancellation (SIC) receiver for space-frequency block coded orthogonal frequency division multiplexing (SFBC-OFDM) transmit diversity schemes. The performance of the proposed SDRQR-SIC receiver is semi- analytically evaluated taking into account the effects of channel estimation errors and error propagation during SIC. In addition, performance and complexity comparisons are drawn with previously proposed approaches. These comparisons show an excellent performance-complexity tradeoff achieved by SDRQR-SIC over the previous solutions under various channel conditions. View full abstract»

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  • Optimal Resource Allocation for Data Service in CDMA Reverse Link

    Page(s): 3648 - 3656
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (255 KB) |  | HTML iconHTML  

    The optimal resource allocation policy is studied for non-real-time users in CDMA reverse link. The resource allocation policy of interest includes channel coding, spreading gain control and power allocation under the conventional receiver operation. The constraints in the optimization include peak transmit power of the mobile station, total received power at the base station and QoS in the form of minimum SINR for each user. The coding and spreading gain control can be separated from the power allocation strategy. Our results show that the optimal power allocation policy depends on the objective function: a greedy policy is optimal to maximize the sum of throughput from each user, whereas a fair policy is optimal to maximize the product of throughput from each user. A unified approach is taken to derive the optimal policies, and it can also be applied to other power allocation problems in CDMA reverse link. Numerical results of the channel capacity are presented for both objectives along with the effect of QoS constraints. View full abstract»

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The IEEE Transactions on Wireless Communications publishes high-quality manuscripts on advances in the state-of-the-art of wireless communications.

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Editor-in-Chief
Jeff Andrews
Cullen Trust for Higher Education Endowed Professor of Engineering