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Wireless Communications, IEEE Transactions on

Issue 1 • Date Jan. 2006

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Displaying Results 1 - 25 of 33
  • IEEE Transactions on Wireless Communications - Table of contents

    Publication Year: 2006 , Page(s): 1 - 217
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  • IEEE Executive staff

    Publication Year: 2006 , Page(s): 0_2
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  • From the editor-in-chief

    Publication Year: 2006 , Page(s): 1 - 2
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  • QoS-Constrained information-theoretic sum capacity of reverse link CDMA. Systems

    Publication Year: 2006 , Page(s): 3 - 7
    Cited by:  Papers (14)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (222 KB) |  | HTML iconHTML  

    The information-theoretic sum capacity of reverse link CDMA systems with QoS constraints is investigated in this paper. Since the reverse link of CDMA systems are, for a given channel and noise conditions, interference-limited, the sum capacity can be achieved by optimally allocating the transmit powers of the mobile stations with the optimal (Shannon) coding. Unfortunately, the sum capacity is usually achieved via unfair resource allocation. This can be avoided by imposing QoS constraints on the system. The results here show that for a single cell system, the sum capacity can be achieved while meeting the QoS constraints with a semi-bang-bang power allocation strategy. Numerical results are then presented to show the multi-user diversity gain and the impact of QoS constraints. The implication of TDM operation in a practical reverse link CDMA system is also discussed. View full abstract»

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  • Modified modulation formats using time-varying phase functions

    Publication Year: 2006 , Page(s): 8 - 11
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB) |  | HTML iconHTML  

    New modulation formats are presented that increase the transmission rate over that of conventional systems, without degrading the bit error rate (BER) and with minimal bandwidth variation. A time-varying function called an "extra phase variation function" (EPVF) is added to the discrete phase of conventional modulation formats such as M-PSK and QAM to transmit additional data bits. A receiver configuration is presented that allows the decoding of information represented by the discrete and extra phases. It is shown that in an additive white Gaussian noise (AWGN) channel, the BER performance of the bits carried by the discrete phase and the extra phase in the modified format improves over the BER of conventional modulation formats. View full abstract»

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  • Throughput performance of an adaptive ARQ scheme in Rayleigh fading channels

    Publication Year: 2006 , Page(s): 12 - 15
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (259 KB) |  | HTML iconHTML  

    Using a simulation study we analyze the throughput performance of Yao's adaptive ARQ scheme in time-varying channels. The simulation takes into account the Rayleigh amplitude and the fast or the slow fading characteristics of a wireless channel, under a representative M-FSK modulation and Reed-Solomon coding scheme. We show that, for a specific set of design parameters, Yao's adaptive procedure works well for all channel fading rates, except for moderately slow rates. By observing variations of packet error rates at a specified SNR we provide an explanation for these varied behaviors under different channel fading rates. View full abstract»

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  • On the use of rate and power adaptation in V-BLAST systems for data protocol performance improvement

    Publication Year: 2006 , Page(s): 16 - 22
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (226 KB) |  | HTML iconHTML  

    In this paper we address the issue of optimizing the performance of data-link and transport protocols running on a system including multiple transmit and receive antennas with a V-BLAST architecture. More specifically, we explore the possibility of adaptively selecting which transmit antennas and which per antenna rates to use as well as the antenna transmit powers in order to maximize the rate of data packets successfully delivered through the system. This is a novel approach with respect to the recent literature which is generally focused on channel capacity optimization. We show that the use of this rate/power adaptation technique, when a data transmission protocol is running over the link, may lead to significant throughput improvements especially at small signal-to-noise ratios. View full abstract»

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  • A channel effect prediction-based power control scheme using PRNN/ERLS for uplinks in DS-CDMA cellular mobile systems

    Publication Year: 2006 , Page(s): 23 - 27
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB) |  | HTML iconHTML  

    This paper proposes a channel effect prediction based power control scheme using pipeline recurrent neural network (PRNN)/extended recursive least squares (ERLS) for uplinks in direct sequence code division multiple access (DS-CDMA) cellular mobile systems. Conventional signal-to-interference (SIR) prediction-based power control schemes may incur prediction mistakes caused by the adjustment of transmission power. The proposed power control scheme purely tracks the variation of channel effect and, thus, can be immune to any power adjustment. Furthermore, it adopts the PRNN with ERLS for predicting the channel effect. Simulation results show that the channel effect prediction-based power control scheme using PRNN/ERLS achieves a 40% higher system capacity and a lower outage probability than the conventional SIR prediction-based power control scheme using grey prediction method (IEEE Trans. Veh. Technol., Vol. 49, No. 6, p. 2081, 2000). View full abstract»

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  • Dual-polarization versus single-polarization MIMO channel measurement results and modeling

    Publication Year: 2006 , Page(s): 28 - 33
    Cited by:  Papers (32)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (558 KB) |  | HTML iconHTML  

    This paper presents a simple multiple-input-multiple-output (MIMO) channel model that predicts the eigenvalue distribution and hence, the capacity of MIMO systems using vertically polarized and dual-polarized transmit-antenna configurations with dual-polarized receive antennas. The channel model is verified using broadband outdoor channel measurements taken by a 2 x 3 MIMO system in the 2.5 GHz band. View full abstract»

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  • Space-time coding over correlated fading channels with antenna selection

    Publication Year: 2006 , Page(s): 34 - 39
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (239 KB) |  | HTML iconHTML  

    In a previous paper by Bahceci et al., antenna selection ' for multiple-antenna transmission systems under the assumption that the subchannels between antenna pairs fade independently was studied. In this paper, the performance of such systems when the subchannels experience correlated fading is considered. It is assumed that the channel-state information (CSI) is available only at the receiver, the antenna selection is performed only at the receiver, and the selection is based on the instantaneous received signal power. The effects of channel correlations on the diversity and coding gain when the receiver system is a subset of the antennas are quantified. Theoretical results indicate that the correlations in the channel do not degrade the diversity order, provided that the channel is full rank. However, it does result in some performance loss in the coding gain. View full abstract»

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  • Signal detection for orthogonal space-time block coding over time-selective fading channels: The Hi systems

    Publication Year: 2006 , Page(s): 40 - 46
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (261 KB) |  | HTML iconHTML  

    One major assumption in all orthogonal space-time block coding (O-STBC) schemes is that the channel remains static over the length of the code word. However, time-selective fading channels do exist, and in such case conventional O-STBC detectors can suffer from a large error floor in the high signal-to-noise ratio (SNR) cases. As a sequel to the authors' previous papers on this subject, this paper aims to eliminate the error floor of the Hi-coded O-STBC system (i = 3 and 4) by employing the techniques of: 1) zero forcing (ZF) and 2) parallel interference cancellation (PIC). It is. shown that for an Hi-coded system the PIC is a much better choice than the ZF in terms of both performance and computational complexity. Compared with the, conventional Hi detector, the PIC detector incurs a moderately higher computational complexity, but this can well be justified by the enormous improvement. View full abstract»

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  • Peak power reduction for OFDM systems with orthogonal pilot sequences

    Publication Year: 2006 , Page(s): 47 - 51
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (329 KB) |  | HTML iconHTML  

    In this paper, a novel peak-to-average power reduction approach for orthogonal frequency division multiplexing (OFDM) has been addressed. Two-dimensional pilot-symbol assisted modulation (2D-PSAM) is employed in coherent OFDM for channel estimation, and it is based on inserting known symbols spread throughout the 2D time-frequency grid. These pilot symbols are employed to simultaneously perform distortionless peak power reduction with a suboptimum technique named orthogonal pilot sequences (OPS), which reduces additional system complexity and side information compared to optimum pilot values. This proposal attains a further step over other previous works, since this set of sequences allows blind detection at the receiver without prior knowledge of any side information. View full abstract»

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  • Organizing reserve channels for superior admission control performance

    Publication Year: 2006 , Page(s): 52 - 56
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (237 KB) |  | HTML iconHTML  

    Good execution of seamless handoffs is key to the quality of service perceived by mobile service subscribers. Giving priority to handoff requests is a strategy commonly considered to guarantee low connection loss when performing handoffs. Often, priority systems can be implemented by adopting a pool of reserved (or guard) resources that is available only for calls or transactions being handed over. Most studies published thus far consider that fixed allocation of the guard resources is being employed. This work considers sharing the reserve channels among cells through the use of a particular method of dynamic resource allocation (DRA). It is shown here that the use of DRA on the pool of guard channels affords a great reduction in the probability of handoff failure without affecting the value of the new call blocking probability, thereby improving the quality of service provided by the cellular operator and also increasing system utilization. View full abstract»

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  • SNR gap approximation for M-PSK-Based bit loading

    Publication Year: 2006 , Page(s): 57 - 60
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (197 KB) |  | HTML iconHTML  

    Adaptive OFDM has the potential of providing bandwidth-efficient communications in hostile propagation environments. Currently, bit loading algorithms use M-ary quadrature amplitude modulation of the OFDM sub-carriers, where the number of bits per symbol modulating each of them is obtained in order to maximize the performance. SNR gap approximation for M-QAM signaling makes the algorithms simpler to implement. However, in some circumstances it may be preferable to use. M-ary phase shift keying. In this letter an approximation is derived for M-PSK similar to the SNR gap of M-QAM so that bit loading algorithms can be extended to this type of modulation. In addition, the performance obtained when using M-PSK is compared to that of M-QAM in a practical situation. View full abstract»

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  • Multiple access capacity of UWB m-ary impulse radio systems with antenna array

    Publication Year: 2006 , Page(s): 61 - 66
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (258 KB) |  | HTML iconHTML  

    In this paper, the multiple access capacity of an Mary pulse position modulation (PPM) impulse radio (IR) system with antenna array is analyzed in dense multipath environments. An antenna array with Rake receivers is used to capture the signal energy from multipaths. Multiple access performance of the system is evaluated in terms of number of supported users for a given bit error rate and bit transmission rate with different number of antenna elements and selected paths. Numerical results show that the multiple access capacity of an M-ary IR system can be improved significantly by increasing the number of antenna elements and/or by adding more paths coherently at the receiver. View full abstract»

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  • Improving the performance of switched diversity with post-examining selection

    Publication Year: 2006 , Page(s): 67 - 71
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (235 KB) |  | HTML iconHTML  

    Switched diversity offers one of the lowest complexity solution for fading mitigation. The receiver employing switched combining schemes. seeks and uses an acceptable diversity path for data reception. However, when no acceptable path is found after all paths have been examined, the receiver ends up randomly choosing an unacceptable path. In this paper, we consider the performance improvement of switched combining schemes. In particular, we modify conventional multi-branch switch and examine combining (SEC) schemes in a way that the best path is selected when no acceptable path is found after all paths have been examined. We carry out a thorough performance versus complexity tradeoff study on the resulting scheme: SEC with post-examining selection and illustrate the study with some selected numerical examples. View full abstract»

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  • Direct downconversion of multiband RF signals using bandpass sampling

    Publication Year: 2006 , Page(s): 72 - 76
    Cited by:  Papers (28)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (230 KB) |  | HTML iconHTML  

    Abstract-Bandpass sampling can be used by radio receivers to directly digitize the radio frequency (RF) signals. Although the bandpass sampling theory for single-band RF signals is well established, its counterpart for multiband RF signals is relatively immature. In this paper, we propose a novel and efficient method to find the ranges of valid bandpass sampling frequency for direct downconverting multiband RF signals. Simple formulas for the ranges of valid bandpass sampling frequency in terms of the frequency locations of the multiple RF bands are derived. The result can be used to design a multiband receiver for software defined radios. View full abstract»

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  • Jammer suppression in DS-CDMA arrays using independent component analysis

    Publication Year: 2006 , Page(s): 77 - 82
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (377 KB) |  | HTML iconHTML  

    We propose using Independent Component Analysis (ICA) as an advanced pre-processing tool for blind suppression of interfering jammer signals in direct sequence spread spectrum communication systems utilizing antenna arrays. The role of ICA is to provide a jammer-mitigated signal to the conventional detection. If the jammer signal is weak or absent, preprocessing by ICA is not advisable. Therefore we also consider two possible switching schemes, called pre-switching and post-switching, which activate the ICA-based jammer canceller only when it is expected to improve conventional detection. ICA-RAKE pre-switching is less complex, while post-switching performs better, especially when the jammer is pulsed in nature. Simulations are given to illustrate the achieved performance gains for single- and multi-path channels. View full abstract»

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  • Performance analysis of maximum ratio transmission based multi-cellular MIMO systems

    Publication Year: 2006 , Page(s): 83 - 89
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (318 KB) |  | HTML iconHTML  

    In this paper, we analyze the performance of the uplink of multi-cellular MIMO systems in flat Rayleigh fading. There is co-channel interference from users within the same cell as well as from other cell users. I The channel model includes lognormal shadowing and path loss along with power control, resulting in a statistical model for user powers. Consistent with practical scenarios, the co-channel interference is categorized into two groups: intracell interference from users within the same cell as the desired user and intercell interference from outer cell users. We derive a compact, easily computable closed form outage probability expression in the form of finite sums. This expression allows for simpler and faster analysis of various MIMO configurations. It has been shown that using antennas on the receiver side results in better performance, since transmit diversity does not combat interference from same cell users. View full abstract»

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  • A stochastic MIMO channel model with joint correlation of both link ends

    Publication Year: 2006 , Page(s): 90 - 100
    Cited by:  Papers (167)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1132 KB) |  | HTML iconHTML  

    Abstract-This paper presents a novel stochastic channel model for multiple-input multiple-output (MIMO) wireless radio channels. In contrast to state-of-the-art stochastic MIMO channel models, the spatial correlation properties of the channel are not divided into separate contributions from transmitter and receiver. Instead, the joint correlation properties are modeled by describing the average coupling between the eigenmodes of the two link ends. The necessary and sufficient condition for the proposed model to hold is that the eigenbasis at the receiver is independent of the transmit weights, and vice versa. The authors discuss the mathematical elements of the model, which can be easily extracted from measurements, from a radio propagation point of view and explain the underlying assumption of the model in physical terms. The validation of the proposed model by means of measured data obtained from two completely different measurement campaigns reveals its ability to better predict capacity and spatial channel structure than other popular stochastic channel models. View full abstract»

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  • Reduced complexity closest point decoding algorithms for random lattices

    Publication Year: 2006 , Page(s): 101 - 111
    Cited by:  Papers (34)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (406 KB) |  | HTML iconHTML  

    Abstract-Closest point algorithms find wide applications in decoding block transmissions encountered with single- or multiuser communication links relying on a single or multiple antennas. Capitalizing on the random channel and noise models typically encountered in wireless communications, the sphere decoding algorithm (SDA) and related complexity-reducing techniques are approached in this paper from a probabilistic perspective. With both theoretical analysis and simulations, combining SDA with detection ordering is justified. A novel probabilistic search algorithm examining potential candidates in a descending probability order is derived and analyzed. Based on probabilistic search and an error-performance-oriented fast stopping criterion, a computationally efficient layered search is developed. Having comparable decoding complexity to the ing-canceling (NQ algorithm with detection ordering, simulations confirm that the novel layered search achieves considerable error-performance enhancement. View full abstract»

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  • Capacity of MIMO Rician channels

    Publication Year: 2006 , Page(s): 112 - 122
    Cited by:  Papers (95)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (342 KB) |  | HTML iconHTML  

    This paper presents exact results on the capacity of multiple-input-multiple-output (MIMO) Rician channels when perfect channel state information (CSI) is assumed at the receiver but the transmitter has neither instantaneous nor statistical CSI. It first derives the exact expression for the average mutual information (MI) rate of MIMO Rician fading channels when the fading coefficients are independent but not necessarily identically distributed. The results for the independent and identically distributed (i.i.d.) MIMO Rician and Rayleigh fading channels are also obtained as special cases. These results are derived using a different approach than the one used by Telatar for the i.i.d. Rayleigh case. The complementary cumulative distribution function (CCDF) of the MI is also obtained using a Gaussian approximation. The CDF of MI can serve as an upper bound to the outage probability of nonergodic MIMO Rician channels. Numerical results confirm that for a fixed channel gain, a strong tine-of-sight component decreases the channel capacity due to the lack of scattering. View full abstract»

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  • FIR zero-forcing equalizer for ISI MIMO channels using space-time modulated codes

    Publication Year: 2006 , Page(s): 123 - 132
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (371 KB) |  | HTML iconHTML  

    Abstract-A systematic method for designing a finite-impulse response (FIR) zero-forcing equalizer (ZFE) of the space-time modulated code (STMC) system based on nonmaximally decimated filterbank is proposed. The physical channel considered is assumed to be multiple-input-multiple-output (MIMO) with intersymbol interference (ISI) and space-time correlated noise. STMC is a space-time block code (STBC) system. Most of the STMC systems require a long guard period to avoid interblock interference (IBI), but, with the proposed equalizer, the length of the guard period is greatly reduced. This can enhance the spectral efficiency of the STMC especially when the channel dispersion is large. The existence conditions for FIR ZFE of the STMC system were derived. These include the maximal code rate STMC for a given channel and the minimal filter order of the FIR ZFE. For a given STMC precoder, the equalizability of the system was verified. The solution of FIR ZFE of STMC was parameterized, which allows the design of optimal FIR ZFE through unconstrained optimization. It is further shown that FIR ZFE could be improved by adding a simple permutation in the system. Design examples and simulation results were presented to evaluate the proposed design method. View full abstract»

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  • Wireless communication systems with-spatial diversity: a volumetric model

    Publication Year: 2006 , Page(s): 133 - 142
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB) |  | HTML iconHTML  

    This paper presents a novel physical-modeling approach to wireless systems with multiple antennas. The fundamental problem of modeling the communication channel is studied, where the channel consists of a finite spatial volume for transmitting, a finite spatial volume for reception, and an arbitrary set of reflective-scattering bodies. The number of communication modes (or degrees of freedom) for such a system is calculated, using the procedure developed. We present a simple model for multipath channels, which allows insight into the development of a correlated multiple-input multiple-output (MIMO) channel model. In particular, the model is independent of transmitter and receiver elements and relies on the physical parameters of the channel involved. Our work explains which physical parameters determine the channel model and its channel capacity. View full abstract»

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  • Capacity of correlated MIMO Rayleigh channels

    Publication Year: 2006 , Page(s): 143 - 155
    Cited by:  Papers (31)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (363 KB) |  | HTML iconHTML  

    Abstract-This paper presents some exact results on the capacity of multiple-input-multiple-output (MIMO) channels subject to correlated Rayleigh fading when perfect channel state information (CSI) is known at the receiver. The authors focus on the semicorrelated scenario in which correlation exists either at the transmitter or at the receiver., They consider two cases: 1) the transmitter does not have any CSI and as such allocates power equally among transmitter antennas and 2) the transmitter only knows the statistical distribution of the channel. The first case derives the moment generating function (MGF) of the mutual information (MI) and then deduces from this MGF the mean MI. The authors also study the cumulative distribution function (CDF) of the MI, which can serve as an upper bound to the outage probability under the capacity versus outage formulation when the channel is nonergodic. The second case studies the capacity achieved by optimum power-loading and beamforming schemes based on covariance feedback. Numerical results illustrate that the full capacity of MIMO systems can be preserved even for relatively high values of correlation coefficients. View full abstract»

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Aims & Scope

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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Meet Our Editors

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