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Wireless Communications, IEEE Transactions on

Issue 11  Part 2 • Date November 2008

 This issue contains several parts.Go to:  Part 1 

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  • IEEE Transactions on Wireless Communications

    Publication Year: 2008
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    Freely Available from IEEE
  • On Throughput Performance of Channel Inequality in IEEE 802.11 WLANs

    Publication Year: 2008 , Page(s): 4425 - 4431
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (322 KB) |  | HTML iconHTML  

    In this paper we investigate the throughput performance of IEEE 802.11 distributed coordination function (DCF) in the presence of physical-layer (PHY) inequality, i.e. varied channel conditions and/or unequal data rates determined by the Link Adaptation (LA) scheme. We present a theoretical model for DCF protocol with the LA scheme of auto rate fallback (ARF). The analysis results show that the system throughput of DCF-based WLANs is determined by the lowest data rate used with stations; throughput sharing among stations depends on the variation of link qualities rather than the difference of data rates. The simulation results validate the accuracy of our analytical model. View full abstract»

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  • Statistical Multimode Transmit Antenna Selection for Limited Feedback MIMO Systems

    Publication Year: 2008 , Page(s): 4432 - 4438
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (551 KB) |  | HTML iconHTML  

    In a wireless multiple-input multiple-output (MIMO) system, transmit antenna selection is an effective means of achieving good performance with low complexity. We consider spatial multiplexing with linear receivers, and equal power and equal rate allocation over different selected transmit antennas in order to reduce feedback overhead. Under these constraints, we address the problem of statistical multimode transmit antenna subset selection to improve the capacity of spatially correlated MIMO fading channels. In particular, we first derive an analytical closed-form expression for the expectation of the lower bound on the capacity using the smallest eigenvalue distribution of a Wishart matrix. Then, we propose a transmit antenna subset selection criterion of maximizing this average lower-bound capacity. View full abstract»

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  • Achievable Rates and Fairness in Rateless Coded Relaying Schemes

    Publication Year: 2008 , Page(s): 4439 - 4444
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB) |  | HTML iconHTML  

    The average throughput of three decode-and-forward (DF) half-duplex (DFHD) and two DF full-duplex (DFFD) rateless coded relaying schemes are studied under a peak power constraint (PPC) and an average power constraint (APC). Two of the DFHD and one of the DFFD protocols are known. One new, much simpler, DFHD protocol, and one new DFFD protocol are proposed. The fairness in comparing the protocols in terms of energy cost is formulated, and the protocols are compared to each other in a power-fair regime. The two previously proposed DFHD protocols, one of which is superior to the other under the PPC, are found to have almost the same performances when compared power-fairly. The proposed protocols are built upon opportunistic communication and power optimization such that, although inferior to their predecessors in a PPC regime, they can slightly surpass them under the APC. View full abstract»

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  • Do We Really Need OSTBCs for Free-Space Optical Communication with Direct Detection?

    Publication Year: 2008 , Page(s): 4445 - 4448
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (237 KB) |  | HTML iconHTML  

    In this letter, the authors investigate spatial diversity techniques for free-space optical (FSO) links with intensity modulation and direct detection (IM/DD) over log-normal atmospheric turbulence-induced fading channels. We restrict our attention to the deployment of orthogonal space-time block codes (OSTBCs) and repetition codes both of which have been recently proposed for FSO links. Our performance analysis demonstrates that, although both schemes are able to extract full diversity, repetition codes outperform OSTBCs. The performance gap increases with the increasing number of transmit apertures. Our findings clearly point out that deployment of OSTBCs is not necessary for a FSO IM/DD link. View full abstract»

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  • Adaptive Modulation Based on Finite-Rate Feedback in Broadcast Channels

    Publication Year: 2008 , Page(s): 4449 - 4454
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB) |  | HTML iconHTML  

    In a single-input single-output (SISO) downlink with multiple users, to obtain the multiuser diversity gain, the full channel state information (CSI) of all users is required for selecting the desired user and transmission mode. However, feedback channels are often capable of carrying only a limited number of bits. With such rate limited feedback links, we intend to maximize the average throughput of each user by designing transmit power levels, signal constellations and feedback thresholds jointly. Both un-coded adaptive M-ary quadrature amplitude modulation (MQAM) and adaptive trellis-coded modulation (TCM) are investigated. A nested iterative algorithm is proposed to obtain a finite number of transmission modes and thresholds. Optimization in the heterogeneous network is also considered. Simulation results demonstrate a small number of feedback bits make the throughput approach to that with perfect CSI. As the number of users increases, the multiuser diversity gain is achieved and the average feedback load of each user is reduced. View full abstract»

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  • Distributed Space-Time Continuous Phase Modulation Code Design

    Publication Year: 2008 , Page(s): 4455 - 4461
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (285 KB) |  | HTML iconHTML  

    In this paper, distributed space-time (ST) codes for continuous-phase modulation (CPM) are introduced. The distributed ST codes are designed to operate in wireless networks containing a large set of nodes N, of which only a small a priori unknown subset S sub N will be active at any time. Under the proposed scheme, a relay node transmits a signal which is the product of a diagonal block-based ST code (optimized specifically for ST-CPM transmission) and a signature vector of length Nc uniquely assigned to each node in the network. An efficient method is presented for the design and optimization of appropriate signature vector sets, assuming a quasi-static, frequency nonselective fading channel model. If a properly designed signature vector set is employed it is shown that a diversity order of d = min{Ns,Nc} can be achieved, where Ns is the number of active relay nodes. The decoding complexity of the proposed scheme is shown to be independent of the number of active relay nodes, and non-coherent receiver implementations, which do not require channel estimation, are applicable. Compared to distributed ST transmission with linear modulation, distributed ST-CPM can considerably reduce the energy consumption at the transmitter due to the constant envelope of the transmit signal. At the same time, the additional energy consumption due to more complex receiver processing can be kept low. Therefore, the proposed distributed ST-CPM scheme is particularly apt for energy-efficient cooperative transmission in wireless networks. View full abstract»

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  • On the Ergodic Capacity of Wireless Relaying Systems over Rayleigh Fading Channels

    Publication Year: 2008 , Page(s): 4462 - 4467
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB) |  | HTML iconHTML  

    The ergodic capacities in Rayleigh fading of various wireless relaying systems with an arbitrary number of half duplex relays are analyzed, assuming channel state information is only known at the receivers. Closed-form analytical expressions for calculation of the ergodic capacities of these systems are derived. It is shown that systems with nonregenerative fixed gain relays achieve higher ergodic capacities than the corresponding systems with nonregenerative variable gain relays. A modified fixed gain relay, which incorporates the power constraint at the relays, is proposed. It is shown that systems with modified fixed gain relays slightly outperform the corresponding systems with nonregenerative variable gain relays and fixed gain relays at small signal-to-noise ratios, but attain almost the same ergodic capacities as systems with nonregenerative variable gain relays as the signal-to-noise ratio increases. In addition, the ergodic capacity of a hybrid system with both regenerative and nonregenerative relays is studied. Systems with regenerative relays employing decode-and-forward relaying offer higher ergodic capacities than the corresponding systems with any classes of nonregenerative relays or hybrid relays. View full abstract»

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  • Tight Approximation of the Bit Error Rate for BICM(-ID) Assuming Imperfect CSI

    Publication Year: 2008 , Page(s): 4468 - 4473
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (247 KB) |  | HTML iconHTML  

    In this correspondence, we analytically derive the bit error rate (BER) for bit-interleaved coded modulation (BICM) under the assumption of a temporally correlated flat Rayleigh fading channel. We assume the channel state information (CSI) to be unknown at receiver side and consider a linear minimum mean-squared error (LMMSE) channel estimator that relies on periodically inserted pilot symbols. We give asymptotic results for both non-iterative BICM and BICM with iterative decoding (BICM-ID). Furthermore, we show that the interpretation of the channel estimation error as an SNR degradation holds true in these cases. View full abstract»

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  • Performance Analysis of MIMO System with Linear MMSE Receiver

    Publication Year: 2008 , Page(s): 4474 - 4478
    Cited by:  Papers (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (282 KB) |  | HTML iconHTML  

    This paper considers the uncoded multiple-input multiple-output (MIMO) system with linear minimum mean square error (MMSE) detection under ideal fast fading. The distribution of SINR at the output of the MMSE detection is derived for a small number of transmit and receive antennas. We present new approximation for the Gaussian Q-function driven by numerical simulation. Based on the SINR distribution and new approximation for Q-function, we analyze the performance of linear MMSE detection under ideal fast fading environment. By comparing the analytical results and Monte Carlo simulated results, we validate the analytical results. View full abstract»

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  • Coordination in a Multi-Cell Multi-Antenna Multi-User W-CDMA System: A Beamforming Approach

    Publication Year: 2008 , Page(s): 4479 - 4485
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB) |  | HTML iconHTML  

    The problem of designing joint power control and optimal beamforming (JPCOB) algorithms for the downlink of a coordinated multi-cell WCDMA system is considered throughout this paper. In this case, the JPCOB design is formulated as the problem of minimizing the total transmitted power in the coordinated multi-cell system, subject to a certain quality of service requirement for each user. In this paper, the performance of two JPCOB algorithms based on different beamforming approaches is compared over the coordinated multi-cell system. The first one, obtains local beamformers by means of the well-known virtual uplink-downlink duality. In contrast, the second algorithm implements multi-base beamformers, taking into account match filter equalizers at the receivers. Moreover, realistic system parameters, such as per-base station power constraints or the asynchronous nature of the signals arriving at the receivers, are taken into account. Simulation results show that the algorithm based on multi-base beamforming presents attractive properties, such as an inherent multi-base scheduling technique or a decreasing total transmitted power as the degree of coordination between base stations is increased. View full abstract»

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  • Semi-Blind Adaptive Spatial Equalization for MIMO Systems with High-Order QAM Signalling

    Publication Year: 2008 , Page(s): 4486 - 4491
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (499 KB) |  | HTML iconHTML  

    This contribution investigates semi-blind adaptive spatial filtering or equalisation for multiple-input multiple-output (MIMO) systems that employ high-throughput quadrature amplitude modulation (QAM) signalling. A minimum number of training symbols, equal to the number of receivers (we assume that the number of transmitters is no more than that of receivers), are first utilized to provide a rough least squares channel estimate of the system is MIMO channel matrix for the initialization of the spatial equalizer is weight vectors. A constant modulus algorithm aided soft decision-directed blind algorithm, originally derived for blind equalization of single-input single-output and single-input multiple-output systems employing high-order QAM signalling, is then extended to adapt the spatial equalizers for MIMO systems. This semi-blind scheme has a low computational complexity, and our simulation results demonstrate that it converges fast to the minimum mean-square-error spatial equalization solution. View full abstract»

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  • Buffering in a Three-Node Relay Network

    Publication Year: 2008 , Page(s): 4492 - 4496
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (229 KB)  

    This paper explores two buffering relay models to improve the capacity of relay networks in slow fading environments. Throughput, average packet delay, and information loss are considered as functions of buffer size and signal-to-noise ratio (SNR). It is shown that, for any fading statistics, both a fixed buffering relay model and a dynamic buffering relay model offer significant performance advantages in terms of capacity over existing methods at the expense of increased delay. It is also seen that, of the two models, dynamic buffering provides a smaller average delay. View full abstract»

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  • Maximum Likelihood Multiple Access Timing Synchronization for UWB Communications

    Publication Year: 2008 , Page(s): 4497 - 4501
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB) |  | HTML iconHTML  

    Rapid and reliable timing synchronization is a demanding task in the receiver design for ultra-wideband (UWB) communication systems, especially when concurrent multiple access is called for. This paper derives a maximum likelihood based timing synchronization scheme for UWB multiple access. Relying on a set of user-specific training sequences, the novel concept of weighted average template is introduced, leading to a multiple access timing synchronizer that works in the absence of any channel knowledge and is resilient to both multiple access interference and noise. Simulation runs testify the effectiveness of the proposed scheme in terms of mean square timing estimation errors and bit-error-rate detection performance when operating in multiple access and dense multipath scenarios. View full abstract»

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  • Soft Combination and Detection for Cooperative Spectrum Sensing in Cognitive Radio Networks

    Publication Year: 2008 , Page(s): 4502 - 4507
    Cited by:  Papers (150)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (235 KB) |  | HTML iconHTML  

    In this letter, we consider cooperative spectrum sensing based on energy detection in cognitive radio networks. Soft combination of the observed energies from different cognitive radio users is investigated. Based on the Neyman-Pearson criterion, we obtain an optimal soft combination scheme that maximizes the detection probability for a given false alarm probability. Encouraged by the performance gain of soft combination, we further propose a new softened hard combination scheme with two-bit overhead for each user and achieve a good tradeoff between detection performance and complexity. View full abstract»

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  • A Distributed Downlink Scheduling Method for Multi-user Communication with Zero-Forcing Beamforming

    Publication Year: 2008 , Page(s): 4508 - 4521
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (638 KB) |  | HTML iconHTML  

    A distributed scheduling approach to multi-user beamforming at a base-station (BS) is proposed. The scheme assumes the BS is equipped with multiple antennas and uses zero-forcing beamforming to schedule multiple users on the same time-frequency uplink/downlink channels. The optimal user set that the BS can schedule is the one that maximizes the sum-rate for the communication channel. The computational complexity of finding the optimal user set becomes intractable as the number of users exceeds 20-30. Sub-optimal schemes for maximizing the sum-rate generally require large control overhead. We propose an effective sum-rate performance metric that accounts for the control overhead required by the scheduling method. We also propose a user scheduling method that has both low complexity and low overhead. The complexity and overhead are reduced by adding one user at a time and distributing the computation of the scheduling problem across the users. Each user calculates the sum-rate that would result if they were added to the existing user set using their own channel and knowledge of the channels of existing users that is broadcast by the BS. The user with greatest sum-rate increase is scheduled. We use simulations to show that this approach can achieve significantly higher effective sum rates than previously proposed sub-optimal schemes. We also derive an approximate expression for the expected sum-rate with our distributed scheduling method and demonstrate its accuracy with simulations. View full abstract»

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  • Using Parasitic Elements for Implementing the Rotating Antenna for MIMO Receivers

    Publication Year: 2008 , Page(s): 4522 - 4533
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (482 KB)  

    We consider a new concept of a multiple-input-multiple-output (MIMO) receiver which uses one active receiving antenna and multiple parasitic elements. The parasitic elements give the possibility of creating a directive antenna beam which is rotated 360 degrees around within the duration of a symbol period. The received signal which is accessed at the antenna connector of the active antenna is expanded in frequency bandwidth compared to the transmitted signal. We show that each sub-band of the received signal consists of linearly independent combinations of the transmitted signals, and thus we have obtained a MIMO receiver. We give a few examples on how to implement this receiver and also explain the effects of sampling the wave-field at discrete angular directions. View full abstract»

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  • Resource Allocation for OFDMA System with Orthogonal Relay using Rateless Code

    Publication Year: 2008 , Page(s): 4534 - 4540
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (402 KB) |  | HTML iconHTML  

    This paper considers the resource allocation problem in the wireless OFDMA system with a relay node. We consider orthogonal relay in which the relay node cannot transmit and receive simultaneously on the same frequency. As a result, the use of relay node may enhance or degrade the achievable transmission rate depending on the instantaneous channel states between the source and the relay, the relay and the destination as well as the source and the destination. Hence, it is very important to dynamically adjust the resources (subbands) allocated to the relay node so that the relay is used only at the right time according to the instantaneous channel states. Conventional approaches dynamically schedule the usage of the relay node in a centralized manner in which full knowledge of the channel states between any two nodes in the network is required. However, perfect knowledge of the channel states at various nodes is very difficult to obtain. In this paper, we shall propose a resource allocation algorithm, which iteratively allocates resource to the source and relay, and converge to the close-to-optimal allocation. Asymptotic achievable rate of the proposed algorithm is derived. We show that the system achieves significant improvement of the achievable rate compared to the point-to-point baseline system without relay as well as the baseline system with random subband allocation. View full abstract»

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  • TAMMAC: An Adaptive Multi-Channel MAC Protocol for MANETs

    Publication Year: 2008 , Page(s): 4541 - 4545
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (626 KB) |  | HTML iconHTML  

    The use of multiple channels in wireless networks could provide performance advantages in reducing collisions and enabling more concurrent transmissions. So et al. proposed a multi-channel MAC protocol, which uses a single transceiver and divides the beacon interval into two parts: channel negotiation and data transmission. However, the fixed length of channel negotiation interval limits the channel utilization. We propose a new single transceiver MAC protocol, named traffic aware multichannel medium access control (TAMMAC), that can exploit multiple channels with smart window increase and decrease rules to adjust the contention window size dynamically and properly. The simulation results show that the proposed protocol achieves higher aggregate network throughput than other schemes under various traffic loads. View full abstract»

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  • Downlink Transmission of Broadband OFCDM Systems-Part V: Code Assignment

    Publication Year: 2008 , Page(s): 4546 - 4557
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (594 KB)  

    To provide high speed mobile services, orthogonal multi-code transmission is employed in the orthogonal frequency and code division multiplexing (OFCDM) system. However, in a wireless frequency selective channel either with or without Doppler shift, code orthogonality is distorted and multi-code interference (MCI) is caused. The variance of the MCI is dependent on which codes to be used. This paper investigates the code assignment in the OFCDM system, aiming to mitigate the MCI. The code assignment can be explored in terms of the code distance defined in this paper. Generally, the codes with large code distances to each other should be assigned with high priority. Moreover, to avoid large interference from the powerful code-multiplexed pilot channel, the time spreading code adjacent to the pilot code in the code tree (Adachi et al., 1998) is suggested not be used when the time domain spreading factor is large. The performance of the proposed non-sequential code assignment scheme is analytically evaluated. It has been shown that the system performance can be improved significantly by the non-sequential scheme under various channel conditions, especially when a low to medium system load is assumed. View full abstract»

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  • LDPC Code Design for Half-Duplex Cooperative Relay

    Publication Year: 2008 , Page(s): 4558 - 4567
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (481 KB) |  | HTML iconHTML  

    The authors consider the design of LDPC codes for cooperative relay systems in the half-duplex mode. The capacity of halfduplex relay channels has been studied previously but the design of good channel codes for such channels remains a challenging problem. Employing an efficient relay protocol, we transform the half-duplex relay code design problem into a problem of ratecompatible LDPC code design where different code segments experience different SNRs. The density evolution with conventional Gaussian approximation for single user channels, which assumes invariant SNR within one codeword, is not capable of accurately predicting the code performance for this system. Here we develop a density evolution with a modified Gaussian approximation that takes into account the SNR variation in one received codeword as well as the rate-compatibility constraint. We then optimize the code ensemble using a modified differential evolution procedure. Extensive simulations are carried out to demonstrate that the proposed algorithm offers more accurate prediction of code performance in half-duplex relay channels than the conventional methods, and the optimized codes achieve a significant gain over existing codes. View full abstract»

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  • On the Study of Network Coded AF Transmission Protocol for Wireless Multiple Access Channels

    Publication Year: 2008 , Page(s): 4568 - 4574
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB) |  | HTML iconHTML  

    In this paper, the performance of the network coded amplify-forward cooperative protocol is studied. The use of network coding can suppress the bandwidth resource consumed by relay transmission, and hence increase the spectral efficiency of cooperative diversity. A distributed strategy of relay selection is applied to the cooperative scheme, which can reduce system overhead and also facilitate the development of the explicit expressions of information metrics, such as outage probability and ergodic capacity. Both analytical and numerical results demonstrate that the proposed protocol can achieve large ergodic capacity and full diversity gain simultaneously. View full abstract»

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  • A Measurement-Based Fading Model for Wireless Personal Area Networks

    Publication Year: 2008 , Page(s): 4575 - 4585
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (589 KB) |  | HTML iconHTML  

    Personal area networks (PANs) are wireless communications systems with high data rates but small coverage area. PAN propagation channels differ from the well-explored propagation channels of wide-area networks due to several reasons: (i) the distances are typically very small, (ii) the antenna arrangements can be quite different, and (iii) the influence from human presence in the environment is different. The current paper presents results of a channel measurement campaign, where measurements are conducted over distances of 1-10 m using several multi-antenna devices, combined to create different PAN scenarios. For each measured Tx-Rx separation, channel realizations are obtained by small spatial movements of the antenna devices, and by rotating the persons holding the devices. From the results, we draw two main conclusions: (i) The small scale amplitude statistics, analyzed as the variations over a small sampling area and frequency subchannels, cannot be described in a satisfactory way using only the Rayleigh or Ricean distribution, rather a mixed distribution, the generalized gamma distribution, is more suitable; (ii) it is advantageous to distinguish between two types of large-scale fading: body shadowing (due to the orientation of the person holding the device) and shadowing due to surrounding objects (lateral movement). We also define and parameterize a complete statistical model for all fading. View full abstract»

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  • Optimizing Joint Erasure- and Error-Correction Coding for Wireless Packet Transmissions

    Publication Year: 2008 , Page(s): 4586 - 4595
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (593 KB) |  | HTML iconHTML  

    To achieve reliable packet transmission over a wireless link without feedback, we propose a layered coding approach that uses error-correction coding within each packet and erasure-correction coding across the packets. This layered approach is also applicable to an end-to-end data transport over a network where a wireless link is the performance bottleneck. We investigate how to optimally combine the strengths of error- and erasure-correction coding to optimize the system performance with a given resource constraint, or to maximize the resource utilization efficiency subject to a prescribed performance. Our results determine the optimum tradeoff in splitting redundancy between error-correction coding and erasure-correction codes, which depends on the fading statistics and the average signal to noise ratio (SNR) of the wireless channel. For severe fading channels, such as Rayleigh fading channels, the tradeoff leans towards more redundancy on erasure-correction coding across packets, and less so on error-correction coding within each packet. For channels with better fading conditions, more redundancy can be spent on error-correction coding. The analysis has been extended to a limiting case with a large number of packets, and a scenario where only discrete rates are available via a finite number of transmission modes. View full abstract»

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  • MAC/PHY Cross-Layer Design of MIMO Ad Hoc Networks with Layered Multiuser Detection

    Publication Year: 2008 , Page(s): 4596 - 4607
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (393 KB) |  | HTML iconHTML  

    In this paper, we present a novel MAC approach for ad hoc networks in which Multiple Input-Multiple Output (MIMO) techniques are used at the physical level (PHY). The use of MIMO in PHY point-to-point as well as multiuser communications has been extensively studied in the recent literature. Here we go one step further, extending the approach to also include protocol design for decentralized and infrastructureless ad hoc networks. First, we study the impact of MIMO on packet transmission in an ad hoc network setting. Then, following a crossiquestlayer design paradigm, we deploy a distributed access control protocol and characterize its performance, with the aim to improve spatial reuse and convey more information on a single ad hoc link. We also explore the interaction between the Medium Access Control (MAC) and PHY layers, and use this knowledge to implement proper policies for distributed traffic control and robustness against interference. Important tradeoffs that arise when managing radio resources are highlighted, and extensive simulation results are presented and discussed. 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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Meet Our Editors

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