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Wireless Communications, IEEE Transactions on

Issue 11 • Date November 2011

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  • Table of contents

    Publication Year: 2011 , Page(s): c1 - c4
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  • [Staff list]

    Publication Year: 2011 , Page(s): c2
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  • Beamforming Effects on Measured mm-Wave Channel Characteristics

    Publication Year: 2011 , Page(s): 3553 - 3559
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (406 KB) |  | HTML iconHTML  

    Beamforming is an important feature of 60 GHz communications. We present an analysis of the influence of beamforming in indoor ultrawideband radio channels measured in the mm-wave 60 GHz band. The performance of narrowband and wideband direction-based beamformers is investigated in terms of improving channel metrics such as the delay spread, excess delay, and the signal-to-noise ratio (SNR). The performance of the direction-based beamformers is compared with dominant eigenmode transmission and statistical beamforming. Our analysis reveals that in line-of-sight (LOS) scenarios, the two direction-based beamformers have a similar performance that approaches the upper bound set by dominant eigenmode transmission. In non-LOS (NLOS) scenarios, the direction-based beamformers show a performance degradation in relation to the upper bound, with the narrowband beamformer worse off than the wideband variant. The array gain in our measured NLOS scenarios is observed to exceed the theoretical upper limit valid for a rich scattering environment. We show that this result follows from the spatial structure of the measured NLOS channels that has only a few strong reflected components. We investigate the influence of array size on beamforming performance; 5×5 planar arrays are observed to improve the channel's delay metrics as well as the larger 7×7 planar arrays. View full abstract»

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  • On the Decoding of Matrix C in the WiMAX Standard

    Publication Year: 2011 , Page(s): 3560 - 3564
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB) |  | HTML iconHTML  

    The decoding of Matrix C in the WiMAX standard is investigated. We propose an exhaustive search and zero-forcing (ES-ZF) decoder and an exhaustive search and nulling canceling (ES-NC) decoder for uncoded systems. The computational complexity of the ES-ZF decoder for Matrix C decoding is shown to be the same as the complexity of the ZF decoder for Matrix B decoding with twice the number of receive antennas times the complexity of the maximum likelihood (ML) decoder for Matrix B decoding with twice the number of receive antennas. Matrix C can be implemented in a 2 x 2 multiple-input multiple-output (MIMO) system using the ES-NC decoder with reduced complexity compared to ML decoding with no performance loss. For coded systems, double pruned trees using a zero-forcing (DPT-ZF) algorithm or nulling canceling (DPT-NC) algorithm are proposed. The DPT-NC decoder is shown to be implemented in a 2 x 2 MIMO coded system with reduced complexity compared to the Max-Log decoding, with no performance loss, by computer simulations. View full abstract»

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  • Smart Trend-Traversal Protocol for RFID Tag Arbitration

    Publication Year: 2011 , Page(s): 3565 - 3569
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB) |  | HTML iconHTML  

    A self-learning Smart Trend-Traversal (STT) protocol for tag arbitration is proposed in this work, which effectively reduces the collision overhead occurred in large-scale RFID systems. The protocol dynamically issues queries according to the adaptively learned tag density and distribution; and therefore, it significantly reduces delay and energy consumption. The optimality of STT does not rely on any presumed network conditions, which is in sharp contrast to other available schemes and renders it a highly desirable and practical solution. View full abstract»

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  • MIMO Transceiver Designs for Spatial Sensing in Cognitive Radio Networks

    Publication Year: 2011 , Page(s): 3570 - 3576
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB) |  | HTML iconHTML  

    We propose transceiver algorithms in cognitive radio networks where the cognitive users are equipped with multiple antennas. Prior work has focused on the design of precoding matrices to suppress interference to the primary receivers. This work considers designs of precoding and decoding matrices for spatial sensing to achieve two objectives: (i) to prevent interference to the primary receivers and (ii) to remove the interference, due to primary transmissions, at the secondary receiver. With single antenna primary terminals and two antenna cognitive terminals, a linear transceiver design has been introduced under a global channel state information (CSI) assumption . In this letter, multiple antenna primary and cognitive terminals and three different CSI scenarios depending upon the amount of CSI are studied: (i) local CSI, (ii) global CSI, and (iii) local CSI with side information. When local CSI is available, we leverage prior work and employ the projected-channel singular value decomposition (P-SVD). In the global CSI scenario, we propose a joint transmitter-receiver design under the assumption of full CSI of all the users at the secondary transceiver. To reduce the feedback overhead, we also propose a new iterative algorithm that exploits only local CSI with side information. In this algorithm, the secondary transmitter and receiver iteratively update precoding and decoding matrices based on the local CSI and side information (precoding/decoding matrices at the previous iteration step) to maximize the rate of the secondary link while maintaining the zero-interference constraint. Convergence is established in the special case of single stream beamforming. Numerical results confirm that the proposed joint design and the iterative algorithm show better achievable rate performance than the P-SVD technique at the expense, respectively, of CSI knowledge and side information. View full abstract»

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  • Statistics-Based ICI Mitigation in OFDM over High-Mobility Channels with Line-of-Sight Components

    Publication Year: 2011 , Page(s): 3577 - 3582
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (390 KB) |  | HTML iconHTML  

    Statistics-based inter-subchannel interference (ICI) mitigation schemes are developed for orthogonal frequency division multiplexing (OFDM) transmission over high-mobility channels with line-of-sight components. By utilizing the channel statistics, we develop the Wiener filtering in the downlink and the transmit preprocessing in the uplink for ICI mitigation. Numerical and simulation results demonstrate that the proposed schemes effectively mitigate ICI and lower the error floor, especially in the presence of a strong line-of-sight path. View full abstract»

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  • Simple, Practical, and Effective Opportunistic Routing for Short-Haul Multi-Hop Wireless Networks

    Publication Year: 2011 , Page(s): 3583 - 3588
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB) |  | HTML iconHTML  

    In this paper, we propose a simple and practical opportunistic routing algorithm, and we analyze its performance along a multi-hop wireless network path, while considering link-level interference among the network nodes. Through our analysis, we show that our algorithm results in significant improvement in throughput, especially for short-haul paths. The proposed algorithm can be easily integrated into most routing protocols with only minor modifications. Consequently, the algorithm provides a practical and effective approach for implementation of opportunistic routing in wireless networks. View full abstract»

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  • Cooperative Spectral Covariance Sensing under Correlated Shadowing

    Publication Year: 2011 , Page(s): 3589 - 3593
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB) |  | HTML iconHTML  

    This paper investigates the theoretical limits of white space sensing in a cognitive radio (CR) network limited by channel correlation. In a log-normal shadowing channel, the received signal power is correlated based on the distance between the sensors and this makes sensing the presence of a signal difficult, even with several cooperative sensors. In the proposed system, each sensor uses the spectral covariance sensing (SCS) algorithm to detect the primary signal and then sends its decision statistic to the base station (BS). The BS, using the Neyman Pearson log-likelihood ratio test, makes the final decision. We analyze the probability of a false alarm (PFA) and compare it with that of the cooperative energy detector. We show that an asymptotic lower bound on the PFA is an order of magnitude lower than that of the energy detector. We also demonstrate improvements in the cooperation gain in terms of the effective number of independent sensors, and the required number of sensors for a given detection metric. The results of this paper show that cooperative SCS detection has far better white space sensing properties than cooperative energy detection in correlated channels. View full abstract»

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  • A Simple Distributed Power Control Algorithm for Cognitive Radio Networks

    Publication Year: 2011 , Page(s): 3594 - 3600
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB) |  | HTML iconHTML  

    This paper studies the power control problem for spectrum sharing based cognitive radio (CR) networks with multiple secondary source-to-destination (SD) pairs. A simple distributed algorithm is proposed for the secondary users (SUs) to iteratively adjust their transmit powers to improve the performance of the network. The proposed algorithm does not require each SU (or PU) to negotiate with other SUs (or PUs) during the communication. It is proved that the proposed algorithm can obtain a time average performance as good as that achieved when the Nash equilibrium (NE) is chosen in hindsight. More specifically, the average performance of CR networks will converge to an ε-Nash equilibrium at a rate of Tε = O (exp (1/ε)). A sub-optimal algorithm is also introduced to further improve the convergence rate to Tε'/log Tε' = O (1/ε'). Numerical results are presented to show the performance of the proposed algorithms under different settings. View full abstract»

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  • Spectral Efficient Multihop Relaying Based on Alternate Transmission

    Publication Year: 2011 , Page(s): 3601 - 3606
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (349 KB) |  | HTML iconHTML  

    A spectral efficient multihop relaying scheme is proposed based on scheduling the source transmission in alternate time slots. Each relay processes its received signal and forwards it in the subsequent time slot. An interference cancellation mechanism is developed to eliminate the interference term at each relay caused by the source alternate-based transmission. The frame error probability and the achievable rate of the proposed scheme are evaluated. It is shown that the individual bit-by-bit detection at the destination performs almost as well as the optimal joint detection, and achieves a data rate that approaches the Shannon channel capacity limit. In addition, the proposed scheme significantly outperforms the conventional orthogonal multihop transmission in terms of the achievable data rate, especially for larger numbers of hops, with slightly inferior frame error rate performance. View full abstract»

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  • Low Complexity Codebook-Based Beamforming for MIMO-OFDM Systems in Millimeter-Wave WPAN

    Publication Year: 2011 , Page(s): 3607 - 3612
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (358 KB) |  | HTML iconHTML  

    In this paper, we consider a beamforming system in millimeter-wave wireless personal area networks (WPAN), where transmit and receive weight vectors are jointly derived by exchanging a training sequence repeatedly with different combinations of transmit and receive weight vectors. We propose a low complexity codebook-based beamforming scheme that consists of multiple levels and level-adaptive antenna selection in order to reduce the beamforming setup time. For each level, 1) the transmit and receive antennas are selected according to pre-determined inter-element spacings, 2) the training sequences are sent with different weight vectors from a pre-defined codebook and 3) the receiver selects the best transmit and receive weight vectors in order to optimize an effective signal-to-noise ratio (SNR) and these vectors are used to determine the codebook for the next following level. Even with low complexity, we show from the numerical results that our proposed scheme can provide an effective SNR gain and an average spectral efficiency approaching those of the codebook-based beamforming with exhaustive search. View full abstract»

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  • Probability Density of the Received Power in Mobile Networks

    Publication Year: 2011 , Page(s): 3613 - 3619
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (446 KB) |  | HTML iconHTML  

    Probability density of the received power is well analyzed for wireless networks with static nodes. However, most of the present days networks are mobile and not much exploration has been done on statistical analysis of the received power for mobile networks in particular, for the network with random moving patterns. In this paper, we derive probability density of the received power for mobile networks with random mobility models. We consider the power received at an access point from a particular mobile node. Two mobility models are considered: Random Direction (RD) model and Random way-point (RWP) model. Wireless channel is assumed to have a small scale fading of Rayleigh distribution and path loss exponent of 4. 3D, 2D and 1D deployment of nodes are considered. Our findings show that the probability density of the received power for RD mobility models for all the three deployment topologies are weighted confluent hypergeometric functions. In case of RWP mobility models, the received power probability density for all the three deployment topologies are linear combinations of confluent hypergeometric functions. The analytical results are validated through NS2 simulations and a reasonably good match is found between analytical and simulation results. View full abstract»

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  • Adaptive Threshold Based Relay Selection for Minimum Feedback and Channel Usage

    Publication Year: 2011 , Page(s): 3620 - 3625
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (309 KB) |  | HTML iconHTML  

    We propose adaptive threshold based relay selection scheme for type-2 (user equipment) relay that requires only minimum 1-bit feedback, for which each relay reports to the source if its R-D (relay-destination) instantaneous channel gain is above threshold (i.e., available). A source then selects the best relay among those that yields the highest S-R (source-relay) instantaneous gain, provided threshold is adjusted according to a target signal-to-noise ratio (SNR). Exact and upper bound on the symbol-error rate (SER) are derived for M-PSK signaling to show that the proposed scheme provides the SER performance close to that of an optimal scheme . Further, it is shown that the spectral efficiency can be improved without degrading the link quality in terms of the SER, via adaptive selection between relay (S-R-D) link and direct (S-D) link based on their link SNRs. View full abstract»

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  • Impact of Outdated Relay Selection on the Capacity of AF Opportunistic Relaying Systems with Adaptive Transmission over Non-Identically Distributed Links

    Publication Year: 2011 , Page(s): 3626 - 3631
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (297 KB) |  | HTML iconHTML  

    In this paper, we derive probability density function (PDF) and cumulative distribution function (CDF) expressions for the end-to-end signal-to-noise ratio (SNR) of an opportunistic relaying amplify-and-forward (AF) cooperative diversity system over independent and non-identically distributed (i.ni.d.) Rayleigh fading links where outdated channel state information (CSI) is used for relay selection. Based on these expressions, we derive the analytical capacity and outage probability expressions for four classical adaptive transmission techniques, namely, optimal power and rate adaptation (OPRA), constant power with optimal rate adaptation (ORA), channel inversion with fixed rate (CIFR) and truncated channel inversion with fixed rate (TIFR). Numerical evaluations results are presented showing the impact of relay selection with outdated CSI and i.ni.d. links on the performance of each adaptive transmission technique in AF opportunistic relaying systems. View full abstract»

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  • On the Performance of Back-Pressure Scheduling Schemes with Logarithmic Weight

    Publication Year: 2011 , Page(s): 3632 - 3637
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (313 KB) |  | HTML iconHTML  

    Recently, significant advances have been made in wireless scheduling toward high-performance networks, leading to development of throughput-optimal scheduling schemes. Beyond throughput performance, however, scheduling with good delay performance has remained open except for a small class of network systems. In this paper, we extend the well-known back-pressure scheduling scheme by using logarithmic weight and improve the delay performance without any loss of throughput performance under multi-hop traffic. We provide rigorous analysis for throughput performance of the proposed solution, and evaluate delay performance through simulations. View full abstract»

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  • Iterative Multiuser Detection for Cooperative MIMO Systems over Quasi-Static Fading Channels

    Publication Year: 2011 , Page(s): 3638 - 3643
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB) |  | HTML iconHTML  

    In this paper, we propose a cooperative multiuser system for multiple-antenna terminals under quasi-static fading. The system employs a bit-interleaved code modulation scheme that combines space-time coding and cooperation based on the decode-and-forward protocol at the transmitter and iterative multiuser detection based on parallel interference cancellation and minimum mean square error filtering at the receiver. We investigate an approach that allows to provide diversity from different channels to each user up to full diversity. Frame error rate performance under Monte Carlo simulations is shown to confirm the effectiveness of the proposed schemes. View full abstract»

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  • Dynamic Sensing Strategies for Efficient Spectrum Utilization in Cognitive Radio Networks

    Publication Year: 2011 , Page(s): 3644 - 3655
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (595 KB) |  | HTML iconHTML  

    For cognitive radio (CR) networks with user hierarchy, the sensing strategy with "listen-before-talk" (LBT) policy plays a key role in spectrum utilization and primary user (PU) protection. However, existing sensing strategies do not handle satisfactorily the randomness of both user locations and channel conditions in the network environment, resulting in inefficient spectrum utilization. To cope with such randomness, this paper develops three dynamic sensing strategies that can adaptively schedule the sensing slots/cycles according to the online link conditions without assuming knowledge of the PU traffic model. The proposed strategies can improve the efficiency of spectrum utilization while being robust with respect to the uncertainty in the PU traffic pattern. To maximize spectrum utilization, the proposed strategies are formulated through closed-form expressions. Efficient methods are introduced to compute the optimal values of the parameters used in the strategies, such as sensing time and sensing threshold. Simulations verify that the proposed sensing strategies offer an evident improvement on the spectrum utilization of the CR network. View full abstract»

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  • Frequency Domain Variation of Eigenvalues in Adaptive MIMO OFDM Systems

    Publication Year: 2011 , Page(s): 3656 - 3665
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (682 KB) |  | HTML iconHTML  

    We consider the effects of the frequency variation of frequency selective fading channels on adaptive multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. The magnitude of this variation has important effects on system performance and design as well as applications to temporal variation, feedback delay and channel estimation.We first examine the variation of the eigenvalues and eigenvalue sums across the frequency bins of a MIMO OFDM system focusing on the changes in the ordered eigenvalues and the eigenvalue sum or link gain between two distinct frequency bins. Here we derive distributions and moments for changes in the link gain and maximum eigenvalue and autocorrelation functions for the link gain and maximum eigenvalue as well as simple approximate results for the ordered eigenvalue differences. We then consider variations in performance via the level crossing rates (LCRs) of the bit error rates (BERs) across the frequency bins of the MIMO OFDM system operating over a Rayleigh fading channel. Each eigenmode constitutes a random process in the frequency domain and we compute the LCR for the BER of transmission down the eigenchannels of the MIMO OFDM channel. We finally verify our analysis using Monte Carlo simulations. View full abstract»

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  • Cross-Layer Antenna Selection and Channel Allocation for MIMO Cognitive Radios

    Publication Year: 2011 , Page(s): 3666 - 3674
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1280 KB) |  | HTML iconHTML  

    We propose algorithms to address the spectrum efficiency and fairness issues of multi band multiuser Multiple-Input and Multiple-Output (MIMO) cognitive ad-hoc networks. To improve the transmission efficiency of the MIMO system, a cross layer antenna selection algorithm is proposed. Using the transmission efficiency results, user data rate of the cognitive ad-hoc network is determined. Objective function for the average data rate of the multi band multiuser cognitive MIMO ad-hoc network is also defined. For the average data rate objective function, primary users interference is considered as performance constraint. Furthermore, using the user data rate results, a learning-based channel allocation algorithm is proposed. Finally, numerical results are presented for performance evaluation of the proposed antenna selection and channel allocation algorithms. View full abstract»

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  • Diversity-Multiplexing Tradeoff in OFDMA Systems: An H-Matching Approach

    Publication Year: 2011 , Page(s): 3675 - 3687
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (747 KB) |  | HTML iconHTML  

    OFDMA is a promising technique because it is capable of improving the transmission reliability and efficiency of multi-user wireless communications. However, previous works on the performance of OFDMA did not properly consider the fundamental relationship between multiplexing and diversity in OFDMA systems. As a comprehensive performance metric, the diversity-multiplexing tradeoff will be applied in this paper to evaluate the subcarrier allocation scheme. The OFDMA system will be formulated into a correlated random bipartite graph model, in which, whether the edges occur or not depends on the distribution of the channel fading. The H-matching method, which is used to determine the maximum collection of vertex-disjoint copies of a fixed sub-graph H contained in a given graph, will then be developed to address the optimal subcarrier allocation problem. Theoretical analysis will show that the proposed H-matching method achieves the optimal outage performance at a given target multiplexing gain, which implies that the optimal diversity-multiplexing tradeoff can be achieved by only allocating subcarriers. Although the H-matching problem is NP-complete, the proposed Random Rotation and Expansion based Hopcroft-Karp (R2EHK) algorithm can still achieve the asymptotically optimal outage performance (i.e., optimal diversity-multiplexing tradeoff) with a sub-linear complexity. Furthermore, the channel state information needed is only one bit per subcarrier. Simulation results will verify the theoretical analysis and will show that the performance loss of the R2EHK algorithm is negligible compared to the exhaustive search method. In addition, it is also shown that the R2EHK algorithm has at least a 2 dB SNR gain compared to the interleaved subcarrier allocation with water-filling power allocation in IEEE 802.16 standards. View full abstract»

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  • MIMO Cognitive Radios with Antenna Selection

    Publication Year: 2011 , Page(s): 3688 - 3699
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1447 KB) |  | HTML iconHTML  

    In this paper, we propose two solutions to the problem of joint transmit-receive antenna selection in a multiple-input multiple-output (MIMO) cognitive radio (CR) system. Our objective is to maximize CR data rates and satisfy interference constraints at the primary user (PU) receiver(s). In the first we approximate the original non-convex optimization problem using an iterative approach solving a series of smaller convex problems. Second we present a novel, norm-based transmit receive antenna selection technique that simultaneously improves throughput while maintaining the PU interference constraints. We show that this approach yields near optimal results with massive complexity reductions. We make a performance comparison between the proposed approaches and the optimal exhaustive search approach. We provide an analysis of the exhaustive search and relate selection gains to system parameters such as the shadow fading standard deviation, the path loss exponent and the number of PUs per square kilometer. Our results establish that antenna selection is a promising option for future MIMO CR devices in sparse PU environments. View full abstract»

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  • Signal Alignment for Multicarrier Code Division Multiple User Two-Way Relay Systems

    Publication Year: 2011 , Page(s): 3700 - 3710
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (634 KB) |  | HTML iconHTML  

    Two-way relay (TWR) transmission provides high spectral efficiency when one-pair of two users exchange information via a single relay. However, in multiuser relay systems where multi-pair of users exchange messages, if the relay does not have sufficient degrees of freedom, the gain of TWR communication may vanish. Fortunately, signal alignment (SA) signaling can recover the spectral efficiency of TWR transmission in multiuser scenarios, which is originally proposed for multiple-input-multiple-output (MIMO) systems. In this paper we investigate signal alignment for multicarrier code division multiple access (MC-CDMA) TWR systems. Due to the difference in channel characteristics and degrees of freedom, the existing SA signalings designed for MIMO TWR systems do not always perform well in MC-CDMA TWR systems. By exploiting the unique features of both TWR systems and MC-CDMA channels, we propose a spectral-efficient SA signaling for MC-CDMA TWR systems, where each pair of users employ a maximal ratio transmitter of its counterpart to align their signals at the relay. We then analyze the spectral efficiency of the designed SA signaling, compare it with non-SA (NSA) signaling, and optimize the power allocation among the relay and users. It is shown from asymptotic analysis and simulation results that the proposed SA signaling can support more users and achieve higher spectral efficiency than NSA signaling. View full abstract»

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  • Estimation of Correlated MIMO Channels using Partial Channel State Information and DPSS

    Publication Year: 2011 , Page(s): 3711 - 3719
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (325 KB) |  | HTML iconHTML  

    A novel approach is proposed for correlated multiple-input multiple-output (MIMO) channel estimation based on reduced-rank (RR) technique and partial channel state information (CSI). In contrast to previous proposals that used the channel correlation matrix (CCM) and its eigendecomposition, this paper shows that close linear minimum mean-square-error (LMMSE) performance can be achieved with the use of predefined bases derived from the knowledge of the maximum angular dispersion. A theoretical framework to synthesize a suitable set of bases is provided, from which discrete prolate spheroidal sequences (DPSSs) are identified as one of the appropriate predefined bases for spatial channel representation. The robustness of the proposed estimator allows changes in the propagation scenario to be managed according to the demands of realistic communications systems. The performance analysis of the channel estimator is shown and corroborated with simulation results. View full abstract»

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  • On the Capacity of MIMO Cellular Systems with Base Station Cooperation

    Publication Year: 2011 , Page(s): 3720 - 3731
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (521 KB) |  | HTML iconHTML  

    This paper is concerned with the capacity of multiple-input multiple-output (MIMO) cellular systems. We assume an equal rate constraint for all users and adopt a realistic channel model that incorporates path loss, lognormal fading and Rayleigh fading. Several bounds are derived for the minimum transmission power of such rate-constrained MIMO cellular systems with various base station (BS) cooperation strategies. In particular, the upper power bound is based on the maximum eigenmode beamforming (MEB) scheme. These power bounds are then used to obtain the corresponding cellular capacity bounds when partial BS cooperation strategies are adopted. Our results show that, allowing more users to transmit simultaneously, introducing cooperation among BSs and increasing the number of antennas (especially at each BS) are efficient ways to improve system performance. View full abstract»

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