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Numrering	Referens	Omslagsbild	Hitta
1.	Angelakis, Vangelis, et al. (författare) A distributed, load-aware, power and frequency bargaining protocol for LTE-based networks 2012 Ingår i: 2012 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC). - Piscataway, NJ, USA : IEEE. - 9781457720529 - 9781457720512 ; , s. 6525-6529 Konferensbidrag (refereegranskat)abstract A distributed, load-aware, joint power and frequency allocation protocol is introduced for LTE-based cellular networks, and system-level simulations are performed. Our proposed scheme aims to cooperatively limit the impact of Fractional Frequency Reuse (FFR) on the center users throughput compared to the Reuse 1 scheme, while providing sufficient throughput for the edge users. This is achieved through an asynchronous, lightweight scheme of local message exchange between neighboring LTE eNodeBs. The proposed scheme facilitates a type of "bargain" where an overloaded sector requests permission to utilize its neighbors edge bands for its center users at a limited set of transmit power levels. Grants are generated at each neighbor by solving a small-scale optimization problem. Using an LTE simulator we evaluate our scheme on a network with 21 sectors of varying load patterns. The proposed schemes performance for center users is consistently improved with respect to FFR-3, while for edge users the performance degradation is controlled by a parameter we set in the optimization problems definitions; compared to Reuse 1 edge users still have gains. Specifically, we observed up to a 46% gain in the sectors center throughput with a cost below 9% at the edges when compared to the classic FFR scheme, while the overall system throughput goes up by up to 26% in heavily loaded scenarios.
2.	Arlitt, Martin, et al. (författare) Passive Crowd-based Monitoring of World Wide Web Infrastructure and its Performance 2012 Ingår i: Proc. IEEE International Conference on Communications (ICC 2012). - : IEEE. - 9781457720529 - 9781457720512 ; , s. 2689-2694 Konferensbidrag (refereegranskat)abstract The World Wide Web and the services it provides are continually evolving. Even for a single time instant, it is a complex task to methodologically determine the infrastructure over which these services are provided and the corresponding effect on user perceived performance. For such tasks, researchers typically rely on active measurements or large numbers of volunteer users. In this paper, we consider an alternative approach, which we refer to as passive crowd-based monitoring. More specifically, we use passively collected proxy logs from a global enterprise to observe differences in the quality of service (QoS) experienced by users on different continents. We also show how this technique can measure properties of the underlying infrastructures of different Web content providers. While some of these properties have been observed using active measurements, we are the first to show that many of these properties (such as location of servers) can be obtained using passive measurements of actual user activity. Passive crowd-based monitoring has the advantages that it does not add any overhead on Web infrastructure, it does not require any specific software on the clients, but still captures the performance and infrastructure observed by actual Web usage.
3.	Duong, Quang Trung, et al. (författare) Distributed Space-Time Coding in Two-Way Fixed Gain Relay Networks over Nakagami-m Fading 2012 Ingår i: Proceedings of the IEEE International Conference on Communicatons (ICC). - Ottawa : IEEE. - 9781457720512 - 9781457720529 ; , s. 3521-3525 Konferensbidrag (refereegranskat)abstract The distributed Alamouti space-time code in two-way fixed gain amplify-and-forward (AF) relay is proposed in this paper. In particular, closed-form expressions for approximated ergodic sum-rate and exact pairwise error probability (PWEP) are derived for Nakagami-m fading channels. To reveal further insights into array and diversity gains, an asymptotic PWEP is also obtained. Finally, numerical results are provided to corroborate the proposed theoretical analysis.
4.	Fowler, Scott, et al. (författare) Analysis of adjustable and fixed DRX mechanism for power saving in LTE/LTE-Advanced 2012 Ingår i: 2012 IEEE International Conference on Communications (ICC). - : IEEE. - 9781457720512 - 9781457720529 - 9781457720536 ; , s. 1964-1969 Konferensbidrag (refereegranskat)abstract The 4G standard Long Term Evolution (LTE) has been developed for high-bandwidth mobile access for today's data-heavy applications, consequently, a better experience for the end user. To extend the user equipment battery lifetime, plus further support various services and large amount of data transmissions, the 3GPP standards for LTE/LTE-Advanced has adopted discontinuous reception (DRX). However, there is a need to optimize the DRX parameters, so as to maximize power saving without incurring network re-entry and packet delays. In this paper, we take an overview of the fixed frame DRX cycle and compare it against an adjustable DRX cycle of the LTE/LTE-Advanced power saving mechanism, by modelling the system with bursty packet data traffic using a semi-Markov process. Based on the analytical model, we will show the trade-off relationship between the power saving and wake-up delay performance.
5.	Hurtig, Per, 1980-, et al. (författare) Enhanced Metric Caching for Short TCP Flows 2012 Ingår i: Proceedings of the IEEE International Conference on Communications (ICC 2012). - : IEEE Press. - 9781457720512 - 9781457720529 ; , s. 1209-1213 Konferensbidrag (refereegranskat)abstract Internet-based applications that require low latency are becoming more common. Such applications typically generate traffic consisting of short, or bursty, TCP flows. As TCP, instead, is designed to optimize the throughput of long bulk flows there is an apparent mismatch. To overcome this, a lot of research has recently focused on optimizing TCP for short flows as well. In this paper, we identify a performance problem for short flows caused by the metric caching conducted by the TCP control block interdependence mechanisms. Using this metric caching, a single packet loss can potentially ruin the performance for all future flows to the same destination by making them start in congestion avoidance instead of slow-start. To solve this, we propose an enhanced selective caching mechanism for short flows. To illustrate the usefulness of our approach, we implement it in both Linux and FreeBSD and experimentally evaluate it in a real test-bed. The experiments show that the selective caching approach is able to reduce the average transmission time of short flows by up to 40%.
6.	Mohammed, Saif Khan, 1977-, et al. (författare) Power-Efficient Downlink Communication Using Large Antenna Arrays: The Doughnut Channel 2012 Ingår i: 2012 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC). - : IEEE. - 9781457720512 - 9781457720529 ; , s. 2145-2150 Konferensbidrag (refereegranskat)abstract Large antenna arrays at the base station can facilitate power efficient single user downlink communication due to the inherent array power gain, i.e., under an average only total transmit power constraint, for a fixed desired information rate, the required total transmit power can be reduced by increasing the number of base station antennas (e. g. with i.i.d. fading, the required total transmit power can be reduced by roughly 3 dB with every doubling in the number of base station antennas, i.e., an O(N) array power gain can be achieved with N antennas). However, in practice, building power efficient large antenna arrays would require power efficient amplifiers/analog RF components. With current technology, highly linear power amplifiers generally have low power efficiency, and therefore linearity constraints on power amplifiers must be relaxed. Under such relaxed linearity constraints, the transmit signal that suffers the least distortion is a signal with constant envelope (CE). In this paper, we consider a single user Gaussian multiple-input single-output (MISO) downlink channel where the signal transmitted from each antenna is constrained to have a constant envelope (i.e., for every channel-use the amplitude of the signal transmitted from each antenna is constant, irrespective of the channel realization). We show that under such a per-antenna CE constraint, the complex noise-free received signal lies in the interior of a "doughnut" shaped region in the complex plane. The per-antenna CE constrained MISO channel is therefore equivalent to a doughnut channel, i.e., a single-input single-output (SISO) AWGN channel where the channel input is constrained to lie inside a "doughnut" shaped region. Using this equivalence, we analytically compute a closed-form expression for an achievable information rate under the per-antenna CE constraint. We then show that, for a broad class of fading channels (i.i.d. and direct-line-of-sight (DLOS)), even under the more stringent per-antenna CE constraint (compared to the average only total power constraint), an O(N) array power gain can still be achieved with N base station antennas. We also show that with N >> 1, compared to the average only total transmit power constrained channel, the extra total transmit power required under the per-antenna CE constraint, to achieve a desired information rate is small and bounded for a broad class of fading channels (i.i.d. and DLOS). We also propose novel CE precoding algorithms. The analysis and algorithms presented are general and therefore applicable to conventional systems with a small number of antennas. Analytical results are supported with numerical results for the i.i.d. Rayleigh fading channel.
7.	Yu, Kan, 1982-, et al. (författare) Adaptive Forward Error Correction for Best Effort Wireless Sensor Networks 2012 Ingår i: 2012 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC). - 9781457720512 - 9781457720529 ; , s. 7104-7109 Konferensbidrag (refereegranskat)abstract In this work we propose an Adaptive Forward Error Correction (AFEC) algorithm for best effort Wireless Sensor Networks. The switching model is described in terms of a ﬁnite-state Markov model and it is based on the channel behavior,observed via Packet Delivery Ratio in the recent past. We compare the performance of AFEC with static FEC, as well as uncoded transmissions. The results demonstrate a gain in PDR achieved by introducing FEC coding in uncoded IEEE 802.15.4 transmissions, as well as the advantages over static FEC schemes,namely increased throughput and reduced energy consumption.The proposed solution is IEEE 802.15.4-compliant and requires no additional feedback channels.
8.	Cavdar, Cicek, et al. (författare) Design of green optical networks with signal quality guarantee 2012 Ingår i: IEEE International Conference on Communications. - : IEEE. - 9781457720529 ; , s. 3025-3030 Konferensbidrag (refereegranskat)abstract Energy consumption of communication networks is growing very fast due to the rapidly increasing traffic demand. Consequently, design of green communication networks gained a lot of attention. In this paper we focus on optical Wavelength Division Multiplexing (WDM) networks, able to support this growing traffic demand. Several energy-aware routing and wavelength assignment (EA-RWA) techniques have been proposed for WDM networks in order to minimize their operational cost. These techniques aim at minimizing the number of active links by packing the traffic as much as possible, thus avoiding the use of lightly loaded links. As a result, EA-RWA techniques may lead to longer routes and to a high utilization on some specific links. This has a detrimental effect on the signal quality of the optical connections, i.e., lightpaths. In this study we quantify the impact of power consumption minimization on the optical signal quality. and address this problem by proposing a combined impairment and energy-aware RWA (IEA-RWA) approach. Towards this goal we developed a complete mathematical model that incorporates both linear and non-linear physical impairments together with an energy efficiency objective. The IEA-RWA problem is formulized as a Mixed Integer Linear Programming (MILP) model where both energy efficiency and signal quality considerations are jointly optimized. By comparing the proposed IEA-RWA approach with existing RWA (IA-RWA and EA-RWA) schemes, we demonstrate that our solution allows for a reduction of energy consumption close to the one obtained by EA-RWA approaches, while still guaranteeing a sufficient level of the optical signal quality.
9.	Dixit, A., et al. (författare) Efficient protection schemes for hybrid WDM/TDM Passive Optical Networks 2012 Ingår i: Communications (ICC), 2012 IEEE International Conference on. - : IEEE. - 9781457720529 ; , s. 6220-6224 Konferensbidrag (refereegranskat)abstract Hybrid WDM/TDM Passive Optical Network (PON) is a promising candidate for next-generation optical access (NGOA) solutions as it is able to offer a high splitting ratio and consequently achieves a relatively low cost and power consumption on a per-user basis compared with other NGOA architectures. On the other hand, the end users require a certain level of connection availability while the operators need to reduce the failure impact (i.e. to avoid a huge number of end users being affected by any single failure). Therefore, by evaluating the connection availability and failure impact robustness we identify the most efficient parts to provide resilience in a hybrid WDM/TDM PON from an operator and an end-user perspective. Then, we select the appropriate protection schemes to construct some novel reliable architectures and analyze their reliability performance in urban and rural scenarios. In this way, this paper provides a comprehensive insight into the most relevant protection mechanisms for hybrid WDM/TDM PONs.
10.	Dössel, Leefke, et al. (författare) Anytime reliability of systematic LDPC convolutional codes 2012 Ingår i: Communications (ICC), 2012 IEEE International Conference on. - : IEEE. - 9781457720529 ; , s. 2171-2175 Konferensbidrag (refereegranskat)abstract We propose a LDPC Convolutional Code ensemble together with an expanding-window message-passing decoder that asymptotically have anytime properties when used for streaming transmission on the binary erasure channel. We show analytically that the decoding erasure probability of these codes decays exponentially over decoding delay and determine the corresponding anytime exponents.
11.	Feyzmahdavian, Hamid Reza, et al. (författare) Contractive interference functions and rates of convergence of distributed power control laws 2012 Ingår i: IEEE International Conference on Communications (ICC), Ottawa, Canada.. - : IEEE. - 9781457720512 ; , s. 4395-4399 Konferensbidrag (refereegranskat)abstract The standard interference functions introduced by Yates have been very influential on the analysis and design of distributed power control laws. While powerful and versatile, the framework has some drawbacks: the existence of fixed-points has to be established separately, and no guarantees are given on the rate of convergence of the iterates. This paper introduces contractive interference functions, a slight reformulation of the standard interference functions that guarantees existence and uniqueness of fixed-points and geometric convergence rates. We show that many power control laws from the literature are contractive and derive, sometimes for the first time, convergence rate estimates for these algorithms. Finally, we show that although standard interference functions are not contractive, they are paracontractions with respect to a certain metric space. Extensions to two-sided scalable interference functions are also discussed.
12.	Gabry, Frédéric, et al. (författare) Cooperation for Secure Broadcasting in Cognitive Radio Networks 2012 Ingår i: Communications (ICC), 2012 IEEE International Conference on. - : IEEE. - 9781457720529 ; , s. 5613-5618 Konferensbidrag (refereegranskat)abstract This paper explores the trade-off between cooperation and secrecy in cognitive radio networks. We consider a scenario consisting of a primary and a secondary system. In the simplest case, each system is represented by a pair of transmitter and receiver. We assume a secrecy constraint on the transmission in the sense that the message of the primary transmitter has to be concealed from the secondary receiver. Both situations where the secondary transmitter is aware and unaware of the primary message are investigated and compared. In the first case, the secondary transmitter helps by allocating power for jamming, which increases the secrecy of the first message. In the latter case, it can also act as a relay for the primary message, thus improving the reliability of the primary transmission. Furthermore, we extend our results to the scenario where the secondary system comprises multiple receivers. For each case we present achievable rate regions. We then provide numerical illustrations for these rate regions. Our main result is that, in spite of the secrecy constraint, cooperation is beneficial in terms of the achievable rates. In particular, the secondary system can achieve a significant rate without decreasing the primary rate below the benchmark rate achievable without the help of the secondary transmitter. Finally, we investigate the influence of the distances between users on the system's performance.
13.	Jónsson, Kristján Valur, et al. (författare) Secure distributed top-k aggregation 2012 Ingår i: Communications (ICC), 2012 IEEE International Conference on. - : IEEE. - 9781457720529 ; , s. 804-809 Konferensbidrag (refereegranskat)abstract In-network aggregation is an efficient and scalable distributed approach to global state approximation. However, security remains an open problem in such systems, especially when we consider dynamic network effects, such as mobility, packet loss and churn. In this paper, we consider the reseilience of the top-k aggregate to manipulation by active insider adversaries. Unfortunately, this versatile aggregation function is inherently insecure. We propose a simple, low-overhead solution to the problem of preserving aggregate integrity which leverages the principles of trusted systems. The solution we propose is generally applicable, even to the challenging problem of securing distributed aggregation in a dynamic network.
14.	Kempf, James, et al. (författare) Scalable fault management for OpenFlow 2012 Ingår i: IEEE International Conference on Communications. - 9781457720529 ; , s. 6606-6610 Konferensbidrag (refereegranskat)abstract In the OpenFlow based split architecture, data-plane forwarding is separated from control and management functions. Forwarding elements make only simple forwarding decisions based on flow table entries populated by the controller. While OpenFlow does not specify how topology monitoring is performed, the centralized controller can use Link-Layer Discovery Protocol (LLDP) messages to discover link and node failures and trigger restoration actions. This monitoring and recovery model has serious scalability limitations because the controller has to be involved in the processing of all of the LLDP monitoring messages. For fast recovery, monitoring messages must be sent with millisecond interval over each link in the network. This poses a significant load on the controller. In this paper we propose to implement a monitoring function on OpenFlow switches, which can emit monitoring messages without posing a processing load on the controller. We describe how the OpenFlow 1.1 protocol should be extended to support the monitoring function. Our experimental results show that data plane fault recovery can be achieved in a scalable way within 50 milliseconds using this function.
15.	Kouyoumdjieva, Sylvia, et al. (författare) Evaluating an Energy-efficient Radio Architecture for Opportunistic Communication 2012 Ingår i: Communications (ICC), 2012 IEEE International Conference on. - : IEEE. - 9781457720529 ; , s. 5751-5756 Konferensbidrag (refereegranskat)abstract A major challenge for wireless networks is to minimize the energy consumption in the mobile devices. This work evaluates potential performance gains of a dual-radio architecture in which a low power radio is used to wake up the primary high power radio. Our targeted domain is opportunistic communication directly between devices. We show that it can significantly reduce the energy consumption at a price of slightly decreased goodput. We also examine the effect of the MAC protocol on the performance of the dual-radio system and we point out that in dense scenarios MAC layer protocols, such as of 802.15.4, do not perform well. We observe that information on device density of an environment can be used to address this shortcoming.
16.	Krikidis, I., et al. (författare) Opportunistic relay selection for cooperative networks with buffers 2012 Ingår i: Communications (ICC), 2012 IEEE International Conference on. - : IEEE. - 9781457720529 ; , s. 5578-5582 Konferensbidrag (refereegranskat)abstract In this paper, a relay selection policy is proposed that fully exploits the flexibility offered by the buffering ability of the relay nodes in order to maximize the achieved diversity gain. The suggested scheme incorporates the instantaneous strength of the wireless links as well as the status of the finite relay buffers and the relay selection decision is based on the strongest available link. Hence the switching occurs dynamically between relay reception and transmission. We show that the proposed relay selection scheme significantly outperforms conventional relay selection policies for all cases and ensures a diversity gain equal to two times the number of relays for large buffer sizes.
17.	Liu, Lingjia, et al. (författare) Energy-Efficient Scheduling for Downlink Multi-User MIMO 2012 Ingår i: IEEE International Conference on Communications (ICC) 2012. - : IEEE conference proceedings. - 9781457720512 ; , s. 4390-4394 Konferensbidrag (refereegranskat)abstract Multi-user MIMO is the enabling technology forLTE-Advanced systems to meet IMT-Advanced targets. The gainof multi-user MIMO is achieved partially through advanced usergrouping,user-scheduling, and precoding. Traditionally, multiuserMIMO scheduling focuses solely on spectral-efficiency [1].That is, the scheduler will strike to balance the cell-edge userspectral-efficiency as well as the cell-average spectral-efficiency.Similar to spectral-efficiency, energy-efficiency is becoming increasinglyimportant for wireless communications. The energyefficiency is measured by a classical measure, “throughput perJoule”, while both RF transmit power and device electronic circuitpower consumptions are considered. In this paper, an energyefficientproportional-fair scheduling is proposed for downlinkmulti-user MIMO systems. To specific, the scheduling algorithmis proposed to balance cell-edge energy-efficiency and the cellaverageenergy-efficiency. The energy-efficient proportional-fairmetric is defined and the optimal power allocation maximizingthe performance measure is identified. System level evaluationsuggests that multi-user MIMO could improve the energyefficiencyof a wireless communication system significantly.
18.	Matthaiou, Michail, 1981, et al. (författare) Sum rate analysis of ZF receivers in distributed MIMO systems with Rayleigh/Lognormal fading 2012 Ingår i: IEEE International Conference on Communications. - 1550-3607. - 9781457720529 ; , s. 3857-3861 Konferensbidrag (refereegranskat)abstract This paper presents a detailed sum rate characterization of distributed multiple-input multiple-output systems operating over composite fading channels and employing linear zero-forcing receivers. We consider the Rayleigh/Lognormal fading model and also take into account the effects of path-loss and spatial correlation at the transmit side. New closed-form upper and lower bounds on the achievable sum rate are proposed that apply for arbitrary numbers of antennas. Moreover, we investigate the concept of large-scale multiple-antenna systems when the number of receive antennas grow large. In this asymptotic regime, it is shown that the effects of Rayleigh fading are averaged out and the channel is dominated by the much more slowly varying shadowing. An interesting observation from our results is that in order to maximize capacity, the radio ports should be placed at unequal distances to the base station when they experience the same level of shadowing.
19.	Nasir, Ali Arshad, et al. (författare) Estimation of Synchronization Parameters in AF Cooperative Networks 2012 Ingår i: IEEE International Conference on Communications. - 1550-3607. - 9781457720529 ; , s. 3713-3717 Konferensbidrag (refereegranskat)abstract In cooperative networks, multiple carrier frequencyoffsets (MCFOs) and multiple timing offsets (MTOs) originate due to multiple distributed nodes. In this paper, algorithms for joint estimation of these parameters and channels in amplify-and-forward (AF) relaying networks are proposed. A new training model and transceiver structure at the relays for achieving synchronization throughout the network is devised. New exact closed-form expressions for the Cram´er-Rao lower bounds (CRLBs) for the multi-parameter estimation problem are derived. An estimation method is proposed for jointly estimating MCFOs, MTOs, and channel gains at the destination based on space-alternating generalized expectation maximization (SAGE) and compared to a computationally-intensiveleast squares (LS) approach. The proposed estimator’s performance is shown to be close to the CRLB at mid-to-high signal-to-noise ratio (SNR) resulting in significant cooperative performance gains in the presence of practical impairments.
20.	Papadimitratos, Panagiotis, et al. (författare) Stealthy pre-attacks against random key pre-distribution security 2012 Ingår i: Communications (ICC), 2012 IEEE International Conference on. - : IEEE. - 9781457720529 ; , s. 955-959 Konferensbidrag (refereegranskat)abstract Random key pre-distribution (RKPD) has been investigated for large wireless sensor networks, in order to achieve efficient security and robustness against limited node compromise. While it is possible that an adversary obtains a subset of the symmetric keys in use, it has been unclear how to use those to compromise specific secure links. We investigate how the adversary could do this practically. We term this the Stealthy Pre-Attack (SPA), because the adversarial nodes leverage benign behavior to guide their attack. The contribution of this paper is the identification of this adversarial behavior, the evaluation of its benefits for the attacker, which can then much more effectively compromise security, and the proposal of counter-measures to mitigate it.
21.	Shen, Wei, et al. (författare) Distributed Data Gathering Scheduling Protocol for Wireless Sensor Actor and Actuator Networks 2012 Ingår i: Communications<em> (ICC), 2012 IEEE International Conference on</em>. - : IEEE Communications Society. - 9781457720512 ; , s. 7120-7125 Konferensbidrag (refereegranskat)abstract This paper presents a cross-layer distributed scheduling protocol for sensor data gathering transmission inwireless sensor actor and actuator networks. We propose the parent-dominant decision scheduling with collision free (PDDS-CF) algorithm to adapt the dynamics of links in a realistic low-power wireless network. In addition, the protocol has a light-weight mechanism to maintain the conflict links. We have evaluated the protocol andimplementation in TinyOS and Telosb hardware. The experiment shows that our protocol has robustness to the topology changes and it has significant improvements to reduce the traffic load in realistic wireless networks.
22.	Sköldström, Pontus, et al. (författare) Network virtualization and resource allocation in OpenFlow-based wide area networks 2012 Ingår i: IEEE International Conference on Communications. - 9781457720529 ; , s. 6622-6626, s. 6622-6626 Konferensbidrag (refereegranskat)abstract In this paper we investigate a number of network virtualization models for OpenFlow networks. Specifically, we investigate three sub-modules of the system - the control channel and the software and hardware parts of an OpenFlow switch. We propose a number of extensions to the OpenFlow specification for this purpose and present a model of a full solution that compared to existing systems provides stricter isolation between different virtual networks while at the same time providing more flexibility.
23.	Stathakis, Efthymios, 1984-, et al. (författare) On combined beamforming and OSTBC over the cognitive radio Z-channel with partial CSI 2012 Ingår i: Communications (ICC), 2012 IEEE International Conference on. - : IEEE. - 9781457720529 ; , s. 2380-2384 Konferensbidrag (refereegranskat)abstract We consider a pair of secondary nodes (SU) coupled, in Z-topology, with multiple pairs of primary nodes (PU). The secondary (cognitive) transmitter is combining beamforming with orthogonal space-time block coding (BOSTBC) and operates under Quality-of-Service (QoS) constraints that must be guaranteed for the primary receivers (PURx). The cognitive link is designed assuming imperfect channel state information (CSI) for all links, available at the SU transmitter (SUTx). Under this premise we characterize the optimal design in terms of CSI quality and interference and evaluate their impact on the performance of BOSTBC transmission in underlay cognitive networks.
24.	Tran, Le-Nam, et al. (författare) On the optimality of beamformer design for zero-forcing DPC with QR decomposition 2012 Ingår i: Communications (ICC), 2012 IEEE International Conference on. - : IEEE. - 9781457720529 ; , s. 2536-2541 Konferensbidrag (refereegranskat)abstract We consider the beamformer design for zero-forcing dirty paper coding (ZF-DPC), a suboptimal transmission technique for MISO broadcast channels (MISO BCs). Beamformers for ZF-DPC are designed to maximize a performance measure, subject to some power constraints and zero-interference constraints. For the sum rate maximization problem under a total power constraint, the existing beamformer designs in the literature are based on the QR decomposition (QRD), which is used to satisfy the ZF constraints. However, the optimality of the QRD-based design is still unknown. First, we prove that the QRD-based design is indeed optimal for ZF-DPC for any performance measure under a sum power constraint. For the per-antenna power constraints, the QRD-based designs become suboptimal, and we propose an optimal design, using a convex optimization framework. Low-complexity suboptimal designs are also presented.
25.	Tran, Le-Nam, et al. (författare) Successive zero-forcing DPC with per-antenna power constraint : Optimal and suboptimal designs 2012 Ingår i: Communications (ICC), 2012 IEEE International Conference on. - : IEEE. - 9781457720529 ; , s. 3746-3751 Konferensbidrag (refereegranskat)abstract This paper considers the precoder designs for successive zero-forcing dirty paper coding (SZF-DPC), a suboptimal transmission technique for MIMO broadcast channels (MIMO BCs). Existing precoder designs for SZF-DPC often consider a sum power constraint. In this paper, we address the precoder design for SZF-DPC with per-antenna power constraints (PAPCs), which has not been well studied. First, we formulate the precoder design as a rank-constrained optimization problem, which is generally difficult to handle. To solve this problem, we follow a relaxation approach, and prove that the optimal solution of the relaxed problem is also optimal for the original problem. Considering the relaxed problem, we propose a numerically efficient algorithm to find the optimal solution, which exhibits a fast convergence rate. Suboptimal precoder designs, with lower computational complexity, are also presented, and compared with the optimal ones in terms of achievable sum rate and computational complexity.
26.	Tran, Le-Nam, et al. (författare) Successive zero-forcing DPC with sum power constraint : Low-complexity optimal designs 2012 Ingår i: Communications (ICC), 2012 IEEE International Conference on. - : IEEE. - 9781457720529 ; , s. 4857-4861 Konferensbidrag (refereegranskat)abstract Successive zero-forcing dirty paper coding (SZF-DPC) is a simplified alternative to DPC for MIMO broadcast channels (MIMO BCs). In the SZF-DPC scheme, the noncausally-known interference is canceled by DPC, while the residual interference is suppressed by the ZF technique. Due to the ZF constraints, the precoders are constrained to lie in the null space of a matrix. For the sum rate maximization problem under a sum power constraint, the existing precoder designs naturally rely on the singular value decomposition (SVD). The SVD-based design is optimal but needs high computational complexity. Herein, we propose two low-complexity optimal precoder designs for SZF-DPC, all based on the QR decomposition (QRD), which requires lower complexity than SVD. The first design method is an iterative algorithm to find an orthonormal basis of the null space of a matrix that has a recursive structure. The second proposed method, which will be shown to require the lowest complexity, results from applying a single QRD to the matrix comprising all users' channel matrices. We analytically and numerically show that the two proposed precoder designs are optimal.
27.	Yu, Kan, et al. (författare) Adaptive Forward Error Correction for Industrial Wireless Sensor Networks 2012 Ingår i: Proceedings. - Ottawa, Canada : IEEE Communications Society. - 9781457720529 ; , s. 7104-7109 Konferensbidrag (refereegranskat)

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