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Wireless Communications, IEEE Transactions on

Issue 12 • Date December 2012

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Displaying Results 1 - 25 of 36
  • Table of contents

    Publication Year: 2012 , Page(s): c1 - c4
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  • Staff list

    Publication Year: 2012 , Page(s): c2
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  • Power Loading Algorithms for OFDM-Based Cognitive Radio Systems with Imperfect Sensing

    Publication Year: 2012 , Page(s): 4225 - 4230
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (205 KB) |  | HTML iconHTML  

    In this letter, we investigate power allocation schemes for OFDM-based cognitive radio (CR) systems while taking errors due to imperfect sensing of primary user (PU) into account. The interference is introduced into PU band by CR user not only because of co-existence in side-by-side bands but also by missed detection due to imperfect sensing. We propose an optimal scheme such that the transmission capacity of CR users is maximized while keeping the total interference within a prescribed threshold and keeping the total power within a budget. As the optimal scheme can have a high complexity, low complexity suboptimal schemes have also been proposed. The performance of the proposed schemes is compared to the schemes that do not take sensing errors into consideration. Presented numerical results demonstrate the strength of our proposed schemes. View full abstract»

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  • Estimation of Rician K-Factors from Block-Averaged Channel Measurements

    Publication Year: 2012 , Page(s): 4231 - 4236
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1430 KB) |  | HTML iconHTML  

    Using simulated data with varying Rician K-factor, averaging block length (N), and sample size (P), this letter proposes and validates two new moment-based, unbiased estimators for block-averaged Rician data and presents a model for their standard errors. One estimator, K̑1,2, has standard error that varies linearly with K and requires iterative calculation. The other estimator K̑2,4, has standard error that can be orders of magnitude larger than the estimates, but has a closed-form solution. K̑2,4 can, however, be recommended when (N ≤ 16, P ≥ 100) if real-time constraints require it. K̑1,2 is recommended otherwise. View full abstract»

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  • Performance Analysis of Two-Step Bi-Directional Relaying with Multiple Antennas

    Publication Year: 2012 , Page(s): 4237 - 4242
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (225 KB) |  | HTML iconHTML  

    In this paper we study decode-and-forward multi-antenna relay systems that achieve bi-directional communication in two time slots. We investigate different downlink broadcast schemes which employ binary or analog network coding at the relay. We also analyze and compare their performances in terms of diversity order and symbol error probability. It is shown that if exact downlink channel state information is available at the relay, using analog network coding in the form of multi-antenna maximal-ratio transmit beamforming to precode the information vectors at the relay gives the best performance. Then, we propose a Max-Min antenna selection with binary network coding scheme that can approach this performance with only partial channel state information. View full abstract»

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  • Graph-Based Soft Channel Estimation for Fast Fading Channels

    Publication Year: 2012 , Page(s): 4243 - 4251
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (475 KB) |  | HTML iconHTML  

    In this paper, a graph-based soft iterative receiver (GSIR) for fast fading channels is investigated. Soft channel estimation as well as soft-output data detection are jointly accomplished via Bayesian inference over a general factor graph. The key feature is a transfer node which enables information flow from one channel node to adjacent channel nodes. The performance characteristics of this receiver is investigated via an EXIT chart analysis and simulation results. Particular emphasis is on a proper channel code design. The algorithm is universally applicable to arbitrary (bijective and non-bijective) modulation formats and can easily be extended to multi-dimensional channel estimation. View full abstract»

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  • Impact of Cognition and Cooperation on MAC Layer Performance Metrics, Part I: Maximum Stable Throughput

    Publication Year: 2012 , Page(s): 4252 - 4263
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB) |  | HTML iconHTML  

    In this paper, we consider a broadband secondary transmitter-receiver pair which interferes with N narrowband primary users and study the effect of cognition and cooperation on the maximum stable throughput. In our study we focus on four transmission protocols as well as two channel types, i.e., flat fading and frequency selective fading. In the cooperative protocols, the broadband transmitter relays the packets of the primary users which have not correctly decoded at the primary receiver. The analysis includes random packet arrivals at the transmitters which may impact on the maximum stable throughput. Moreover, sensing errors at the secondary user are considered. In this paper, we derive the exact stability region for non-cooperative protocols and inner bounds for cooperative ones. The results reveal that depending on the channel states, the cooperative protocols may provide significant performance gains over non-cooperative protocols. Numerical results indicate that in the frequency selective channel, independent and simultaneous parallel transmissions in the available subbands are preferred, while in the flat fading channel, a non-parallel transmission in the total available bandwidth is recommended. In part II of our paper, we investigate the impact of cognition and cooperation on the delay performance of the protocols introduced in this paper. View full abstract»

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  • Network-Compressive Coding for Wireless Sensors with Correlated Data

    Publication Year: 2012 , Page(s): 4264 - 4274
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (450 KB) |  | HTML iconHTML  

    A network-compressive transmission protocol is developed in which correlated sensor observations belonging to a finite alphabet are linearly combined as they traverse the network on their way to a sink node. Statistical dependencies are modeled using factor graphs. The sum-product algorithm is run under different modeling assumptions to estimate the maximum a posteriori set of observations given the compressed measurements at the sink node. Error exponents are derived for cyclic and acyclic factor graphs using the method of types, showing that observations can be recovered with arbitrarily low probability of error as the network size grows. Simulated tests corroborate the theoretical claims. View full abstract»

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  • Performance Analysis and Energy Efficiency of Random Network Coding in LTE-Advanced

    Publication Year: 2012 , Page(s): 4275 - 4285
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1082 KB) |  | HTML iconHTML  

    Recent trends witness the shift of the 3GPP Long Term Evolution - Advanced (LTE-A) radio access network (RAN) architecture from a traditional macro-cellular layout towards smaller base stations moving closer to end users. The evolved LTE-A RAN offers rich environment for multi-point and multi-hop cooperation and coordination resulting in increased capacity and more predictable channel conditions between heterogeneous base stations and end users. While these opportunities are recently well investigated at the physical layer through various cooperative multi-point (CoMP) schemes, upper layer protocols preserve the design proposed for macro-cellular single-hop data delivery. In this paper, we address this issue by proposing and investigating in detail a cooperative RAN-wide MAC layer protocol based on random network coding (RNC) that is designed specifically for reliable and flexible data delivery over the evolved LTE-A RAN. The proposed RNC-based MAC protocol (MAC-RNC) is evaluated and compared with the existing HARQ-based (MAC-HARQ) protocol in various LTE-A RAN layouts using a customized packet-based link-level simulator based on Finite-State Markov Chain (FSMC) channel models. Our results show that the MAC-RNC protocol introduces simplicity and flexibility required for future LTE-A RANs, while preserving or improving the performance of the MAC-HARQ protocol in traditional single-point single-hop macro-cellular scenarios. View full abstract»

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  • Modulation and SNR Optimization for Achieving Energy-Efficient Communications over Short-Range Fading Channels

    Publication Year: 2012 , Page(s): 4286 - 4295
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (492 KB) |  | HTML iconHTML  

    It is commonly assumed that the energy consumption of wireless communications is minimized when low-order modulations such as BPSK are used. Nevertheless, the literature provides some evidence that low-order modulations are suboptimal for short transmission distances. No complete analysis on how the modulation size and transmission power must be chosen in order to achieve energy-efficient communications over fading channels has been reported so far. In this paper we provide this analysis by presenting a model that determines the energy consumed per payload bit transferred without error over fading channels of various statistics. We find that each modulation scheme has a single optimal signal-to-noise ratio (SNR) at which the energy consumption is minimized. The optimal SNR and the minimal energy consumption are larger for channels with less favorable error statistics. We also find that, if each modulations is operated at its optimal SNR, BPSK and QPSK are the optimal choices for long transmission distances, but as the transmission distance shortens the optimal modulation size grows to 16-QAM and even to 64-QAM. This result leads to showing that for short-range communications the lifetime of a typical low-power transceiver can be up to 500% longer by selecting the optimal constellation instead of BPSK. View full abstract»

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  • Experiment-Driven Characterization of Full-Duplex Wireless Systems

    Publication Year: 2012 , Page(s): 4296 - 4307
    Cited by:  Papers (47)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (881 KB) |  | HTML iconHTML  

    We present an experiment-based characterization of passive suppression and active self-interference cancellation mechanisms in full-duplex wireless communication systems. In particular, we consider passive suppression due to antenna separation at the same node, and active cancellation in analog and/or digital domain. First, we show that the average amount of cancellation increases for active cancellation techniques as the received self-interference power increases. Our characterization of the average cancellation as a function of the self-interference power allows us to show that for a constant signal-to-interference ratio at the receiver antenna (before any active cancellation is applied), the rate of a full-duplex link increases as the self-interference power increases. Second, we show that applying digital cancellation after analog cancellation can sometimes increase the self-interference, and thus digital cancellation is more effective when applied selectively based on measured suppression values. Third, we complete our study of the impact of self-interference cancellation mechanisms by characterizing the probability distribution of the self-interference channel before and after cancellation. View full abstract»

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  • Capacity and Coding for Two Common Wireless Erasure Relay Networks with Optimal Bandwidth Allocation

    Publication Year: 2012 , Page(s): 4308 - 4317
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (505 KB) |  | HTML iconHTML  

    This paper considers two simple wireless network configurations - the multiple access relay channel (MARC) and the multiple relay channel (MRC) - in which the links making up the network time-share the medium and the assumed loss mechanisms are memoryless packet erasures. The capacity region of the MARC and the capacity of the MRC are derived as functions of the link erasure rates. This is done assuming (i) optimal sharing of bandwidth among the transmitters, and (ii) perfect knowledge at the destination of erasure patterns on all the links. Moreover, it is shown that easily-implemented capacity-approaching codes for the binary erasure channel, such as LDPC or Tornado codes, can be used to attain any achievable rate(s). Finally, these capacity results are unchanged in the presence of feedback of erasure location information to all nodes. For the erasure MARC, the results imply a simple strategy, viz., that the relay should help only those sources that have a weaker direct channel to the destination than the relay itself - regardless of the quality of the source-to-relay channels. For the erasure MRC, the solution has a more complex, inductive structure: the participation of a relay r in the optimal strategy depends on the best throughput that can be achieved using only those relays with a better link to the destination than r. View full abstract»

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  • General Decode-and-Forward Cooperative Relaying with Co-Channel Interference in Shadowed Nakagami Fading Channels

    Publication Year: 2012 , Page(s): 4318 - 4327
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (341 KB) |  | HTML iconHTML  

    General multi-branch multi-hop (MBMH) cooperative diversity systems with selection decode-and-forward (DF) relays are investigated on non-identical shadowed Nakagami-m fading channels in the presence of an arbitrary number of non-identical co-channel interferers. This paper presents closed-form expressions for the outage probability, the average symbol error probability, and the probability density function of signal-to-interference-plus-noise ratio of the selection DF MBMH cooperative relaying system. The results of the paper show that outage and error performance improvements against shadowing stem from the number of branches rather than the number of hops for a fixed number of relays. The results also show that the performance of the selection DF MBMH cooperative relaying system is more vulnerable when co-channel interferers are closer to the destination than when they are closer to the relays. This analysis is verified by Monte Carlo simulations. View full abstract»

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  • An Indirect-Reciprocity Reputation Game for Cooperation in Dynamic Spectrum Access Networks

    Publication Year: 2012 , Page(s): 4328 - 4341
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (641 KB) |  | HTML iconHTML  

    Cooperation is a promising approach to simultaneously achieve efficient utilization of spectrum resource and improve the quality of service of primary users in dynamic spectrum access networks. However, due to the selfish nature, secondary users may not act as cooperatively as primary users have expected. Therefore, how to stimulate the secondary users to play cooperatively is an important issue. In this paper, we propose a reputation-based spectrum access framework, where the cooperation stimulation problem is modeled as an indirect reciprocity game. In the proposed game, secondary users choose how to help primary users relay information and gain reputations, based on which they can access a certain amount of vacant licensed channels in the future. By formulating a secondary user's decision making as a Markov decision process, we obtain the optimal action rule, according to which the secondary user will use maximal power to help primary user relay data if the channel is not in an outage, and thus greatly improve the primary user's quality of service as well as the spectrum utilization efficiency. Moreover, we prove the uniqueness of stationary reputation distribution and theoretically derive the condition under which the optimal action rule is evolutionarily stable. Finally, simulation results are shown to verify the effectiveness of the proposed scheme. View full abstract»

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  • Time Domain Blind I/Q Imbalance Compensation Based on Real-Valued Filter

    Publication Year: 2012 , Page(s): 4342 - 4350
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (322 KB) |  | HTML iconHTML  

    This paper proposes a novel time domain blind compensation for frequency-independent and frequency-dependent I/Q imbalance in direct-conversion receivers. Analysis of a difference filter representing the frequency-dependent I/Q imbalance shows that the filter taps are tightly constrained by analog front-end image attenuation (IA). For practical front-ends with reasonable IA, it is proved that the difference filter is minimum phase. We also show that the magnitude response of the difference filter can be obtained from the branch signal autocorrelations. Then, the magnitude response can be used to determine the corresponding minimum phase response. Subsequently, from the cross-correlation of the branch signals, we can estimate the frequency-independent phase imbalance. Since the proposed method has an analytical solution, it can be easily implemented. Simulations of various scenarios confirm its validity and its superior compensation performance. View full abstract»

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  • The Affecting Factors in Resource Optimization for Cooperative Communications: A Case Study

    Publication Year: 2012 , Page(s): 4351 - 4361
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (511 KB) |  | HTML iconHTML  

    Cooperative networks provide enhanced system performance by exploiting spatial diversity in a distributed manner. Optimum resource allocation can help improve the performance of cooperative networks and increase the efficiency of resource usage. In the literature, various system performance and optimization results have been reported for different systems and with different optimization metrics. However, there lacks a unifying framework delineating the effects of different factors on resource optimization and the resultant benefit. In this paper, we investigate the relative effects of optimization metric (error rate versus outage probability), modulation type (coherent versus differential) and relaying protocol (amplify-and-forward (AF) versus decode-and-forward (DF)). To facilitate such a case study, we provide a comprehensive set of system performance for four commonly adopted cooperative systems: coherent amplify-and-forward (CAF), coherent decode-and-forward (CDF), differential amplify-and-forward (DAF), and differential decode-and-forward (DDF). A resource optimization problem that minimizes the total transmit energy is formulated. Since energy optimization has been intensively studied in the literature, location optimization will be investigated. The analyses and simulations suggest that: i) The error rate and outage probability metrics yield similar optimization results for AF relaying systems; ii) The relaying protocol determines the optimization results while the modulation type has no effect; and iii) The difference between different relaying protocols diminishes when the number of relays increases. View full abstract»

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  • Enabling Code Diversity for Mobile Radio Channels using Long-Range Fading Prediction

    Publication Year: 2012 , Page(s): 4362 - 4371
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (976 KB) |  | HTML iconHTML  

    Code diversity integrates space-time coding with beamforming by using a small number of feedback bits to select from a family of space-time codes. Different codes lead to different induced channels at the receiver, where Channel State Information (CSI) is used to instruct the transmitter how to choose the code. Feedback can be combined with sub-optimal low complexity decoding of the component codes to match Maximum-Likelihood (ML) decoding performance of any individual code in the family. It can also be combined with ML decoding of the component codes to improve performance beyond ML decoding performance of any individual code. Prior analysis of code diversity did not take into account the effect of the mobile speed and the delay in the feedback channel. This paper demonstrates the practicality of code diversity in space-time coded systems by showing that performance gains based on instantaneous feedback are largely preserved when long-range prediction of time-varying correlated fading channels is employed to compensate for the effect of the feedback delay. To maintain prediction accuracy for realistic SNR, noise reduction that employs oversampled pilots is used prior to fading prediction. We also propose a robust low pilot rate method that utilizes interleaving to improve the spectral efficiency. Simulations are presented for two channel models: the conventional Jakes model and a realistic physical channel model where the parameters associated with the reflectors vary in time and the arrival rays have different strengths and asymmetric arrival angles. View full abstract»

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  • Joint Spectrum-Sensing Design and Power Control in Cognitive Radio Networks: A Stochastic Approach

    Publication Year: 2012 , Page(s): 4372 - 4380
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (428 KB) |  | HTML iconHTML  

    Efficient design of spectrum-sensing and power control plays a key role in maximizing the throughput of a cognitive radio (CR) network while protecting the PUs from undue interference. In this paper, we consider the problem of joint spectrum-sensing-duration design and power control in a point-to-point CR link. The objective of the proposed solution is to maximize the CR achievable throughput while keeping the CR interference to the primary user (PU) at or below a preset interference threshold. The joint spectrum-sensing design and power control is a non-convex optimization problem, hence, obtaining the optimal solution may not be always feasible. In this paper, we formulate the joint sensing-duration design and power control problem as a two-stage stochastic program with recourse. Afterward, we derive the formulas for the achievable throughput as a function of the sensing duration. Moreover, we investigate the effect of different levels of knowledge of the interference channel state information (CSI) on the achievable throughput and the optimal sensing duration. View full abstract»

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  • Full-Duplex Relay Selection for Amplify-and-Forward Cooperative Networks

    Publication Year: 2012 , Page(s): 4381 - 4393
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (757 KB) |  | HTML iconHTML  

    This paper focuses on the relay selection problem in amplify-and-forward (AF) cooperative communication with full-duplex (FD) operation. Different relay selection schemes assuming the availability of different instantaneous information are studied. We consider optimal relay selection that maximizes the instantaneous FD channel capacity and requires global channel state information (CSI) as well as several sub-optimal relay selection policies that utilize partial CSI knowledge such as a) source-relay and relay-destination links b) loop interference c) source-relay links and loop interference. To facilitate comparison, exact outage probability expressions and asymptotic approximations of these policies that show a zero diversity order are derived. In addition, an optimal relay selection procedure that incorporates a hybrid relaying strategy, which dynamically switches between FD and half-duplex relaying according to the instantaneous CSI, is also investigated. View full abstract»

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  • Performance Analysis of Dual-User Macrodiversity MIMO Systems with Linear Receivers in Flat Rayleigh Fading

    Publication Year: 2012 , Page(s): 4394 - 4404
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (793 KB) |  | HTML iconHTML  

    The performance of linear receivers in the presence of co-channel interference in Rayleigh channels is a fundamental problem in wireless communications. Performance evaluation for these systems is well-known for receive arrays where the antennas are close enough to experience equal average SNRs from a source. In contrast, almost no analytical results are available for macrodiversity systems where both the sources and receive antennas are widely separated. Here, receive antennas experience unequal average SNRs from a source and a single receive antenna receives a different average SNR from each source. Although this is an extremely difficult problem, progress is possible for the two-user scenario. In this paper, we derive closed form results for the probability density function (pdf) and cumulative distribution function (cdf) of the output signal to interference plus noise ratio (SINR) and signal to noise ratio (SNR) of minimum mean squared error (MMSE) and zero forcing (ZF) receivers in independent Rayleigh channels with arbitrary numbers of receive antennas. The results are verified by Monte Carlo simulations and approximations and high SNR analysis are also derived. The results enable further system analysis such as the evaluation of outage probability, bit error rate (BER) and capacity. View full abstract»

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  • Greening Effect of Spatio-Temporal Power Sharing Policies in Cellular Networks with Energy Constraints

    Publication Year: 2012 , Page(s): 4405 - 4415
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (846 KB) |  | HTML iconHTML  

    Greening effect in interference management (IM), a way of enhancing spectrum sharing via intelligent transmit power control, can be achieved by the fact that as BSs moderately reduce their transmit powers, the performance degradation decreases slower than linearly, yet a considerable overall energy saving is expected due to transmit powers' exerting influence on operational power. This paper investigates the impact of different spatial and/or temporal power sharing policies for a given system-wide power budget in IM schemes. We develop an optimization-theoretic IM framework on cellular network greening, from which we first develop four IM schemes governed by different power sharing: no sharing, only temporal sharing, only spatial sharing, and both spatial and temporal sharing. Through extensive simulations, including a real BS deployment in Manchester city, United Kingdom, we obtain the following interesting observations: (i) the gains both from performance and power saving are obtained by adopting the spatial and/or temporal power sharing policies, (ii) tighter greening regulation (i.e., smaller total power budget) leads to higher spatio-temporal power sharing gain than IM gain, (iii) spatial power sharing significantly excels temporal one in terms of power saving, and (iv) higher greening efficiency can be achieved as the cell size becomes smaller. View full abstract»

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  • Maximum Outage Capacity in Dense Indoor Femtocell Networks with Joint Energy and Spectrum Utilization

    Publication Year: 2012 , Page(s): 4416 - 4425
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (403 KB) |  | HTML iconHTML  

    We consider a multiple femtocell deployment in a small area which shares spectrum with the underlaid macrocell. We design a joint energy and radio spectrum scheme which aims not only for co-existence with the macrocell, but also for an energy-efficient implementation of the multi-femtocells. Particularly, aggregate energy usage on dense femtocell channels is formulated taking into account the cost of both the spectrum and energy usage. We investigate an energy-and-spectral efficient approach to balance between the two costs by varying the number of active sub-channels and their energy. The proposed scheme is addressed by deriving closed-form expressions for the interference towards the macrocell and the outage capacity. Analytically, discrete regions under which the most promising outage capacity is achieved by the same size of active sub-channels are introduced. Through a joint optimization of the sub-channels and their energy, properties can be found for the maximum outage capacity under realistic constraints. Using asymptotic and numerical analysis, it can be noticed that in a dense femtocell deployment, the optimum utilization of the energy and the spectrum to maximize the outage capacity converges towards a round-robin scheduling approach for a very small outage threshold. This is the inverse of the traditional greedy approach. View full abstract»

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  • Zero-Forcing Based MIMO Two-Way Relay with Relay Antenna Selection: Transmission Scheme and Diversity Analysis

    Publication Year: 2012 , Page(s): 4426 - 4437
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (756 KB) |  | HTML iconHTML  

    Combining of physical-layer network coding (PNC) and multiple-input multiple-output (MIMO) can significantly improve the performance of the wireless two-way relay network (TWRN). This paper proposes novel Max-Min optimization based relay antenna selection (RAS) schemes for zero-forcing (ZF) based MIMO-PNC transmission. RAS relaxes ZF's constraints on the number of antennas and extends the applications of ZF based MIMO-PNC to more practical scenarios, where the dedicated relay has more antennas than the end node. Moreover, RAS also brings diversity advantages to TWRN and the achievable diversity gains of the proposed schemes are theoretically analyzed. In particular, an equivalence relation is carefully built for the diversity gains obtained by 1) RAS for ZF based MIMO-PNC and 2) transmit antenna selection (TAS) for MIMO broadcasting (BC) with ZF receivers. This equivalence transforms the original problem to a more tractable form which eventually allows explicit analytical results. It is interesting to see that Max-Min RAS keeps the network diversity gain of ZF based MIMO-PNC to be the same as the diversity gain of the point-to-point link within the TWRN. This insight extends the understanding on the behaviors of ZF transceivers with antenna selection (AS) to relatively complicated MIMO-TWRN/BC scenarios. View full abstract»

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  • Correlation-Aware Resource Allocation in Multi-Cell Networks

    Publication Year: 2012 , Page(s): 4438 - 4445
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (908 KB) |  | HTML iconHTML  

    We propose a cross-layer strategy for resource allocation between spatially correlated sources in the uplink of multi-cell FDMA networks. Our objective is to find the optimum power and channel allocation to the different sources, in order to minimize the maximum distortion achieved in decoding any source data in the network. This problem is NP-hard and finding the optimal solution is not computationally feasible. We propose a three-step algorithm to be performed separately in each cell, which finds cross-layer resource allocation in simple steps. This method separates the problem into inter-cell resource management, grouping of sources for joint decoding, and intra-cell channel assignment. For each of these steps we propose methods that satisfy different design constraints and analyze them by simulations. We show that, while using correlation in compression and joint decoding can achieve 25% distortion reduction over independent decoding, the improvement grows to 37% when correlation is also utilized in resource allocation. This significant distortion reduction motivates further work in correlation-aware resource allocation. Overall, our solution is able to achieve a 60% decrease in 5 percentile distortion compared to independent allocation methods. View full abstract»

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  • Performance Modeling and Stability of Semi-Persistent Scheduling with Initial Random Access in LTE

    Publication Year: 2012 , Page(s): 4446 - 4456
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB) |  | HTML iconHTML  

    In this paper we examine the feasibility of semi-persistent scheduling (SPS) for voice over IP (VoIP) by random access and evaluate its performance in terms of throughput of random access and traffic channels, and random access delay. We further investigate system stability issues and present methods to stabilize the system. To see the VoIP capacity gain, we show the maximum number of acceptable VoIP terminals without exceeding some front-end packet dropping (i.e., voice clipping) probability. In addition, we examine the effect of the parameter called implicit release after in the LTE standard on the system performance, which is used for silence period detection. Our performance evaluation model based on Equilibrium Point Analysis is compared to simulations. View full abstract»

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

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