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74
The minimum range assignment problem on linear radio networks
, 2000
"... Given a set of radio stations located on a line and an integer, the MIN ASSIGNMENT problem consists in finding a range assignment of minimum power consumption provided that any pair of stations can communicate in at most hops. Previous positive results for this problem are only known when or in the ..."
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Cited by 25 (6 self)
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Given a set of radio stations located on a line and an integer, the MIN ASSIGNMENT problem consists in finding a range assignment of minimum power consumption provided that any pair of stations can communicate in at most hops. Previous positive results for this problem are only known when or in the uniform chain case (i.e. when the stations are equally spaced). As for the first case, Kirousis, Kranakis, Krizanc and Pelc (1997) provided a polynomialtime algorithm while, for the second case, they derive a polynomialtime approximation algorithm. This paper presents the first polynomialtime, approximation algorithm for the MIN ASSIGNMENT problem. The algorithm guarantees a 2 approximation ratio and runs in time. We also prove that, for fixed and for “well spaced ” instances (a broad generalization of the uniform chain case), the problem admits a polynomialtime approximation scheme (PTAS). This result significantly improves over the approximability result given by Kirousis et al. Both our approximation results are obtained via new algorithms that exactly solve two natural variants of the MIN ASSIGNMENT problem: the problem in which every station must reach a fixed one in at most hops and the problem in which the goal is to select a subset of bases such that all the other stations must
Distributed power control for time varying wireless networks: Optimality and convergence
 in Proceedings: Allerton Conference on Communications, Control, and Computing
, 2003
"... This paper presents a new distributed power control algorithm for adhoc wireless networks in random channel environments. Previous work in this area has focused on distributed power control for adhoc networks with fixed channels. We show that the algorithms resulting from such formulations do not ..."
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Cited by 19 (1 self)
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This paper presents a new distributed power control algorithm for adhoc wireless networks in random channel environments. Previous work in this area has focused on distributed power control for adhoc networks with fixed channels. We show that the algorithms resulting from such formulations do not accurately capture the dynamics of a timevarying channel. The performance of the network, in terms of power consumption and generated interference, can be severely degraded when a power control algorithm designed for a deterministic channel is applied to a random channel. In particular, some wellknown strong optimality results for such algorithms no longer hold. In order to address these problems we propose a new criterion for power optimality in adhoc wireless networks. We then show that the optimal power allocation for this new criterion can be found through an appropriate stochastic approximation algorithm. Ultimately, the iterations of the stochastic approximation algorithm can be decoupled to form an optimal fully distributed online power control algorithm for adhoc wireless networks with timevarying channels. 1
Models and Techniques for Communication in Dynamic Networks Christian
 In Proc. of the 19th Symp. on Theoretical Aspects of Computer Science (STACS
, 2001
"... In this paper we will present various models and techniques for communication in dynamic networks. Dynamic networks are networks of dynamically changing bandwidth or topology. Situations in which dynamic networks occur are, for example: faulty networks (links go up and down), the Internet (the bandw ..."
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Cited by 17 (2 self)
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In this paper we will present various models and techniques for communication in dynamic networks. Dynamic networks are networks of dynamically changing bandwidth or topology. Situations in which dynamic networks occur are, for example: faulty networks (links go up and down), the Internet (the bandwidth of connections may vary), and wireless networks (mobile units move around). We investigate the problem of how to ensure connectivity, how to route, and how to perform admission control in these networks. Some of these problems have already been partly solved, but many problems are still wide open. The aim of this paper is to give an overview of recent results in this area, to identify some of the most interesting open problems and to suggest models and techniques that allow us to study them.
Interference Avoidance for Wireless Systems
 In Vehicular Technology Conference
, 1999
"... Motivated by the emergence of programmable radios, we seek to understand a new class of communication system where pairs of transmitters and receivers can adapt their modulation/demodulation method in the presence of interference to achieve better performance. Using signal to interference ratio as a ..."
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Cited by 16 (9 self)
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Motivated by the emergence of programmable radios, we seek to understand a new class of communication system where pairs of transmitters and receivers can adapt their modulation/demodulation method in the presence of interference to achieve better performance. Using signal to interference ratio as a metric and a general signal space approach, we present a class of iterative distributed algorithms for synchronous systems which results in an ensemble of optimal waveforms for multiple users connected to a common receiver (or colocated independent receivers). That is, the waveform ensemble meets the Welch Bound with equality and therefore achieves minimum average interference over the ensemble of signature waveforms. We describe fixed points for a number of scenarios. 1 Introduction Wireless system designers have always had to contend with interference from both natural sources and other users of the medium. Thus, the classical wireless communications design cycle has consisted of measu...
A Power Control Game Based on Outage Probabilities for Multicell Wireless Data Networks
 in Proc. of American Control Conference (ACC) 2004
, 2004
"... We present a gametheoretic treatment of distributed power control in CDMA wireless systems using outage probabilities. We prove that the noncooperative power control game considered admits a unique Nash equilibrium (NE) for uniformly strictly convex pricing functions and under some technical assump ..."
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Cited by 16 (6 self)
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We present a gametheoretic treatment of distributed power control in CDMA wireless systems using outage probabilities. We prove that the noncooperative power control game considered admits a unique Nash equilibrium (NE) for uniformly strictly convex pricing functions and under some technical assumptions on the SIR threshold levels. We analyze global convergence of continuoustime as well as discretetime synchronous and asynchronous iterative power update algorithms to the unique NE of the game. Furthermore, a stochastic version of the discretetime update scheme, which models the uncertainty due to quantization and estimation errors, is shown to converge almost surely to the unique NE point. We further investigate and demonstrate the convergence and robustness properties of these update schemes through simulation studies.
Controlling QoS by Integrated Power Control and Link Adaptation in Broadband Wireless Networks
, 1999
"... . We propose and analyze the performance of an algorithm for integrated power control and adaptive modulation/coding to achieve a specified range of packet error rate for realtime applications in broadband wireless packetswitched networks. The algorithm applies the Kalmanfilter method [1] for p ..."
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Cited by 16 (5 self)
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. We propose and analyze the performance of an algorithm for integrated power control and adaptive modulation/coding to achieve a specified range of packet error rate for realtime applications in broadband wireless packetswitched networks. The algorithm applies the Kalmanfilter method [1] for power control, and adapts packet transmission to an appropriate modulation level, according to the packet error requirement, and the radio and interference conditions. A new criterion for maintaining stable transmission power is derived. Based on the criterion, the proposed technique performs the link adaptation and adjusts transmission power to achieve the specified packet error rate. The effectiveness of the proposed method is demonstrated by several numerical examples. 1 INTRODUCTION Customers' demand for broadband network services has been growing significantly as telecommuting and Internet access become increasingly popular. In the very near future, broadband services are also exp...
Control of Mobile Communications with Time Varying Channels in Heavy Traffic
 IEEE Trans. Automat. Control
, 2001
"... Consider a system with a xed number (K) of remote units and a single base transmitter with time varying (and perhaps correlated) connecting channels. Data to be transmitted to the remote units arrives according to some random process and is queued according to its destination. The forward link is tr ..."
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Cited by 16 (1 self)
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Consider a system with a xed number (K) of remote units and a single base transmitter with time varying (and perhaps correlated) connecting channels. Data to be transmitted to the remote units arrives according to some random process and is queued according to its destination. The forward link is treated. Power is to be allocated to the K channels in a queue and channel state dependent way to minimize some cost criterion. The modeling and control problem can be quite difficult. The channel time variations (fading) are fast and the bandwidth and data arrival rates are high. Owing to the complexity of the physical problem and the high speed of both the fading and arrival and service rates, an asymptotic or averaging method is promising. A heavy traffic analysis is done. By heavy traffic, we mean that on the average there is little server idle time and little spare power over the "average" requirements. Heavy traffic analysis has been very helpful in simplifying analysis of both controlled and uncontrolled problems in queueing and communications networks. It tends to eliminate unessential detail and focus on the fundamental issues of scaling and parametric dependencies. To illustrate the scope of the method, a variety of models are considered. The basic model assumes that the channel state is known or can be well estimated and that given the channel state there is a well defined rate of transmission per unit power. Then convergence of the controlled scaled queue lengths is shown. The scaling is different from the usual in heavy traffic work, and the limit Wiener process depends only on the channel state process and not on the...
Power Control in TwoTier Femtocell Networks
, 2008
"... Two tier cellular networks, comprising of a central macrocell underlaid with short range femtocell hotspots offer an economical way to improve cellular capacity. With shared spectrum and lack of coordination between tiers, crosstier interference limits overall capacity. To quantify nearfar effects ..."
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Cited by 15 (3 self)
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Two tier cellular networks, comprising of a central macrocell underlaid with short range femtocell hotspots offer an economical way to improve cellular capacity. With shared spectrum and lack of coordination between tiers, crosstier interference limits overall capacity. To quantify nearfar effects with universal frequency reuse, this paper derives a fundamental relation providing the largest feasible macrocell SignaltoInterferencePlusNoise Ratio (SINR), given any set of feasible femtocell SINRs. A distributed utilitybased SINR adaptation at femtocells is proposed in order to alleviate crosstier interference at the macrocell from overlaid femtocell infrastructure. The FoschiniMiljanic (FM) algorithm is a special case of the adaptation. Each femtocell maximizes its individual utility consisting of a SINR based reward less an incurred cost (interference to the macrocell). Numerical results show greater than 30 % improvement in mean femtocell SINRs relative to FM. In the event that crosstier interference prevents a macrouser from obtaining its SINR target, an algorithm is proposed that adaptively curtails transmission powers of the strongest femtocell interferers. The algorithm ensures that a macrouser achieves its SINR target even with 100 femtocells/cellsite, and requires a worst case SINR reduction of only 16 % at femtocells. These results motivate design of power control schemes requiring minimal network overhead in twotier networks with shared spectrum.
A KalmanFilter Method for Power Control in Broadband Wireless Networks
 Proc. of IEEE Infocom’99
, 1998
"... : A Kalmanfilter method for power control is proposed for broadband, packetswitched TDMA wireless networks. By observing the temporal correlation of cochannel interference when transmitters can send data contiguously, a Kalman filter is used to predict interfence power in the future. Based on the ..."
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Cited by 14 (9 self)
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: A Kalmanfilter method for power control is proposed for broadband, packetswitched TDMA wireless networks. By observing the temporal correlation of cochannel interference when transmitters can send data contiguously, a Kalman filter is used to predict interfence power in the future. Based on the predicted interference and estimated path gain between the transmitter and receiver, transmission power is determined to achieve a desired signaltointerferenceplusnoise ratio (SINR). Performance results reveal that the Kalmanfilter method for power control provides a significant performance improvement. Specifically, when a message consists of 10 packets on average, the 90 and 95 percentile of the SINR by the new method are 3.94 and 5.53 dB above those when no power control is in use, and lie just 0.73 and 1.04dB below the upperbound performance of the optimal power control, respectively, in a system with 4sector cells and an interleaved frequency assignment of a reuse factor of 2/8 ...