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31
Analysis of energy efficiency in fading channel under QoS constrains
- IEEE Global Communications Conference (GLOBECOM
, 2008
"... Abstract — 1 Energy efficiency in fading channels in the pres-ence of QoS constraints is studied. Effective capacity, which provides the maximum constant arrival rate that a given process can support while satisfying statistical delay constraints, is considered. Spectral efficiency–bit energy tradeo ..."
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Cited by 18 (11 self)
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Abstract — 1 Energy efficiency in fading channels in the pres-ence of QoS constraints is studied. Effective capacity, which provides the maximum constant arrival rate that a given process can support while satisfying statistical delay constraints, is considered. Spectral efficiency–bit energy tradeoff is analyzed in the low-power and wideband regimes by employing the effective capacity formulation, rather than the Shannon capacity, and energy requirements under QoS constraints are identified. The analysis is conducted for the case in which perfect channel side information (CSI) is available at the receiver and also for the case in which perfect CSI is available at both the receiver and transmitter. In particular, it is shown in the low-power regime that the minimum bit energy required in the presence of QoS constraints is the same as that attained when there are no such limitations. However, this performance is achieved as
Queuing Analysis in Multichannel Cognitive Spectrum Access: A Large Deviation Approach
"... Abstract—The queueing performance of a (secondary) cognitive user is investigated for a hierarchical network where there are N independent and identical primary users. Each primary user employs a slotted transmission protocol, and its channel usage forms a two-state (busy,idle) discrete-time Markov ..."
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Cited by 13 (2 self)
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Abstract—The queueing performance of a (secondary) cognitive user is investigated for a hierarchical network where there are N independent and identical primary users. Each primary user employs a slotted transmission protocol, and its channel usage forms a two-state (busy,idle) discrete-time Markov chain. The cognitive user employs the optimal policy to select which channel to sense (and use if found idle) at each slot. In the framework of effective bandwidths, the stationary queue tail distribution of the cognitive user is estimated using a large deviation approach for which closed-form expressions are obtained when N =2. Upper and lower bounds are obtained for the general N primary user network. For positively correlated primary transmissions, the bounds are shown to be asymptotically tight. Monte Carlo simulations using importance sampling techniques are used to validate the obtained large deviation estimates. Index terms—Effective bandwidth, Queueing analysis, Cognitive radio and Dynamic spectrum access.
Queueing Analysis of a Butterfly Network for Comparing Network Coding to Classical Routing
- IEEE Transactions on Information Theory
, 2010
"... Abstract—Network coding has gained significant attention in re-cent years as a means to improve throughput, especially in mul-ticast scenarios. These capacity gains are achieved by combining packets algebraically at various points in the network, thereby al-leviating local congestion at the nodes. T ..."
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Cited by 9 (0 self)
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Abstract—Network coding has gained significant attention in re-cent years as a means to improve throughput, especially in mul-ticast scenarios. These capacity gains are achieved by combining packets algebraically at various points in the network, thereby al-leviating local congestion at the nodes. The benefits of network coding are greatest when the network is heavily utilized or, equiva-lently, when the sources are saturated so that there is data to send at every scheduling opportunity. Yet, when a network supports delay-sensitive applications, traffic is often bursty and congestion becomes undesirable. The lighter loads typical of real-time traffic with variable sources tend to reduce the returns of network coding. This work seeks to identify the potential benefits of network coding in the context of delay-sensitive applications. As a secondary objec-tive, this paper also studies the cost of establishing network coding in wireless environments. For a network topology to be suitable for coding, links need to possess a proper structure. The cost of es-tablishing this structure may require excessive radio resources in terms of bandwidth and transmit power. Bursty traffic together with structural cost tend to decrease the potential benefits of net-work coding. This paper describes how, for real-time applications over wireless networks, there exist network topologies for which it may be best not to establish a network structure tailored to net-work coding. Index Terms—Butterfly network, communication system, delay, quality of service (QoS), network coding, routing, tail asymptotics, tandem queues, wireless networks, wireless systems. I.
The impact of QoS constraints on the energy efficiency of fixed-rate wireless transmissions,” submitted to the
- IEEE International Conference on Communications (ICC
, 2009
"... Transmission over wireless fading channels under quality of service (QoS) constraints is studied when only the receiver has channel side information. Being unaware of the channel conditions, transmitter is assumed to send the information at a fixed rate. Under these assumptions, a two-state (ON-OFF) ..."
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Cited by 9 (7 self)
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Transmission over wireless fading channels under quality of service (QoS) constraints is studied when only the receiver has channel side information. Being unaware of the channel conditions, transmitter is assumed to send the information at a fixed rate. Under these assumptions, a two-state (ON-OFF) transmission model is adopted, where information is transmitted reliably at a fixed rate in the ON state while no reliable transmission occurs in the OFF state. QoS limitations are imposed as constraints on buffer violation probabilities, and effective capacity formulation is used to identify the maximum throughput that a wireless channel can sustain while satisfying statistical QoS constraints. Energy efficiency is investigated by obtaining the bit energy required at zero spectral efficiency and the wideband slope in both wideband and low-power regimes assuming that the receiver has perfect channel side information (CSI). In the wideband regime, it is shown that the bit energy required at zero spectral efficiency is the minimum bit energy. A similar result is shown for a certain class of fading distributions in the low-power regime. In both wideband and lowpower regimes, the increased energy requirements due to the presence of QoS constraints are quantified. Comparisons with variable-rate/fixed-power and variable-rate/variable-power cases are given. Energy efficiency is further analyzed in the presence of channel uncertainties. The scenario in which a priori unknown fading coefficients are estimated at the receiver via minimum mean-square-error (MMSE) estimation with the aid of training symbols, is considered. The optimal fraction of power allocated to training is identified under QoS constraints. It is proven that the minimum bit energy in the low-power regime is attained at a certain nonzero power level below which bit energy increases without bound with vanishing power. Hence, it is shown that it is extremely energy inefficient to operate at very low power levels when the channel is only imperfectly known.
MIMO wireless communications under statistical queuing constraints
- IEEE Trans. Inform. Theory
, 2011
"... ar ..."
Effective Capacity of a Correlated Rayleigh Fading Channel
"... The next generation wireless networks call for quality of service (QoS) support. The effective capacity (EC) proposed by Wu and Negi provides a powerful tool for the design of QoS provisioning mechanisms. In their previous work, Wu and Negi derived a formula for effective capacity of a Rayleigh fadi ..."
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Cited by 6 (1 self)
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The next generation wireless networks call for quality of service (QoS) support. The effective capacity (EC) proposed by Wu and Negi provides a powerful tool for the design of QoS provisioning mechanisms. In their previous work, Wu and Negi derived a formula for effective capacity of a Rayleigh fading channel with arbitrary Doppler spectrum. However, their paper did not provide simulation results to verify the accuracy of the EC formula derived in their paper. This is due to difficulty in simulating a Rayleigh fading channel with a Doppler spectrum of continuous frequency, required by the EC formula. To address this difficulty, we develop a verification methodology based on a new discrete-frequency EC formula; different from the EC formula developed by Wu and Negi, our new discrete-frequency EC formula can be used in practice. Through simulation, we verify that the EC formula developed by Wu and Negi is accurate. Furthermore, to facilitate the application of the EC theory to the design of practical QoS provisioning mechanisms in wireless networks, we propose a spectral-estimation-based algorithm to estimate the EC function, given channel measurements; we also analyze the effect of spectral estimation error on the accuracy of EC estimation. Simulation results show that our proposed spectral-estimation-based EC estimation algorithm is accurate, indicating the excellent practicality of our algorithm.
Value-aware resource allocation for service guarantees in networks,”
- in Proceedings of INFOCOM,
, 2010
"... Abstract-The traditional formulation of the total value of information transfer is a multi-commodity flow problem. Each data source is seen as generating a commodity along a fixed route, and the objective is to maximize the total system throughput under some concept of fairness, subject to capacity ..."
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Cited by 6 (1 self)
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Abstract-The traditional formulation of the total value of information transfer is a multi-commodity flow problem. Each data source is seen as generating a commodity along a fixed route, and the objective is to maximize the total system throughput under some concept of fairness, subject to capacity constraints of the links used. This problem is well studied under the framework of network utility maximization and has led to several different distributed congestion control schemes. However, this view of value does not capture the fact that flows may associate value, not just with throughput, but with link-quality metrics such as packet delay and jitter. In this work, the congestion control problem is redefined to include individual source preferences. It is assumed that degradation in link quality seen by a flow adds up on the links it traverses, and the total utility is maximized in such a way that the end-to-end quality degradation seen by each source is bounded by a value that it declares. Decoupling sourcedissatisfaction and link-degradation through an effective capacity variable, a distributed and provably optimal resource allocation algorithm is designed to maximize system utility subject to these quality constraints. The applicability of the controller in different situations is supported by numerical simulations, and a protocol developed using the controller is simulated on ns-2 to illustrate its performance.
Effective Capacity of a Correlated Nakagami-m Fading Channel
"... The grail of next-generation wireless networks is providing real-time services for delay-sensitive applications, which require that the wireless networks provide QoS guarantees. The effective capacity (EC) proposed by Wu and Negi provides a powerful tool for design of QoS provisioning mechanisms. In ..."
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Cited by 4 (1 self)
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The grail of next-generation wireless networks is providing real-time services for delay-sensitive applications, which require that the wireless networks provide QoS guarantees. The effective capacity (EC) proposed by Wu and Negi provides a powerful tool for design of QoS provisioning mechanisms. In this paper, we intend to generalize their formula for the effective capacity of a correlated Rayleigh fading channel; specifically, we derive a closed form approximate EC formula for a special correlated Nakagami-m fading channel, for which the inverse of the correlation coefficient matrix is tridiagonal. To verify its accuracy via simulation, we develop a Green-matrix based approach, which allows us to analytically obtain the effective capacity (given the joint probability density function of a correlated Nakagami-m fading channel) while being able to simulate the corresponding channel gain process. Simulation results show that our EC formula is accurate. Furthermore, to facilitate the application of the EC theory to the design of practical QoS provisioning mechanisms, we propose a simple algorithm for estimating the EC of an arbitrary correlated Nakagami-m fading channel, given channel measurements; simulation results demonstrate the accuracy of our proposed EC estimation algorithm, showing its suitability in practice.
Energy Efficiency of Fixed-Rate Wireless Transmissions under Queueing Constraints and Channel Uncertainty
, 901
"... Energy efficiency of fixed-rate transmissions is studied in the presence of queueing constraints and channel uncertainty. It is assumed that neither the transmitter nor the receiver has channel side information prior to transmission. The channel coefficients are estimated at the receiver via minimum ..."
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Cited by 4 (2 self)
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Energy efficiency of fixed-rate transmissions is studied in the presence of queueing constraints and channel uncertainty. It is assumed that neither the transmitter nor the receiver has channel side information prior to transmission. The channel coefficients are estimated at the receiver via minimum mean-square-error (MMSE) estimation with the aid of training symbols. It is further assumed that the system operates under statistical queueing constraints in the form of limitations on buffer violation probabilities. The optimal fraction of of power allocated to training is identified. Spectral efficiency–bit energy tradeoff is analyzed in the low-power and wideband regimes by employing the effective capacity formulation. In particular, it is shown that the bit energy increases without bound in the lowpower regime as the average power vanishes. On the other hand, it is proven that the bit energy diminishes to its minimum value in the wideband regime as the available bandwidth increases. For this case, expressions for the minimum bit energy and wideband slope are derived. Overall, energy costs of channel uncertainty and queueing constraints are identified. Abstract — 1 I.
On the Queueing Behavior of Random Codes over a Gilbert-Elliot Erasure Channel
- IN: IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY PROCEEDINGS (ISIT), 2010
, 2010
"... This paper considers the queueing performance of a system that transmits coded data over a time-varying erasure channel. In our model, the queue length and channel state together form a Markov chain that depends on the system parameters. This gives a framework that allows a rigorous analysis of the ..."
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Cited by 3 (2 self)
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This paper considers the queueing performance of a system that transmits coded data over a time-varying erasure channel. In our model, the queue length and channel state together form a Markov chain that depends on the system parameters. This gives a framework that allows a rigorous analysis of the queue as a function of the code rate. Most prior work in this area either ignores block-length (e.g., fluid models) or assumes error-free communication using finite codes. This work enables one to determine when such assumptions provide good, or bad, approximations of true behavior. Moreover, it offers a new approach to optimize parameters and evaluate performance. This can be valuable for delay-sensitive systems that employ short block lengths.
