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179
A RateAdaptive MAC Protocol for MultiHop Wireless Networks
, 2001
"... Wireless local area networks (WLANs) have become increasingly popular due to the recent availability of affordable devices that are capable of communicating at high data rates. These high rates are possible, in part, through new modulation schemes that are optimized for the channel conditions bring ..."
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Cited by 474 (5 self)
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Wireless local area networks (WLANs) have become increasingly popular due to the recent availability of affordable devices that are capable of communicating at high data rates. These high rates are possible, in part, through new modulation schemes that are optimized for the channel conditions bringing about a dramatic increase in bandwidth efficiency. Since the choice of which modulation scheme to use depends on the current state of the transmission channel, newer wireless devices often support multiple modulation schemes, and hence multiple data rates, with mechanisms to switch between them. Users are given the option to either select an operational data rate manually or to let the device automatically choose the appropriate modulation scheme (data rate) to match the prevailing conditions. Automatic rate selection protocols have been studied for cellular networks but there have been relatively few proposals for WLANs. In this paper we present a rate adaptive MAC protocol called the ReceiverBased AutoRate (RBAR) protocol. The novelty of RBAR is that its rate adaptation mechanism is in the receiver instead of in the sender. This is in contrast to existing schemes in devices like the WaveLAN II [15]. We show that RBAR is better because it results in a more efficient channel quality estimation which is then reected in a higher overall throughput Our protocol is based on the RTS/CTS mechanism and consequently it can be incorporated into many medium access control protocols including the widely popular IEEE 802.11 protocol. Simulation results of an implementation of RBAR inside IEEE 802.11 show that RBAR performs consistently well.
Efficient power control via pricing in wireless data networks
 IEEE Trans. on Commun
, 2002
"... Abstract—A major challenge in the operation of wireless communications systems is the efficient use of radio resources. One important component of radio resource management is power control, which has been studied extensively in the context of voice communications. With the increasing demand for wir ..."
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Cited by 331 (8 self)
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Abstract—A major challenge in the operation of wireless communications systems is the efficient use of radio resources. One important component of radio resource management is power control, which has been studied extensively in the context of voice communications. With the increasing demand for wireless data services, it is necessary to establish power control algorithms for information sources other than voice. We present a power control solution for wireless data in the analytical setting of a game theoretic framework. In this context, the quality of service (QoS) a wireless terminal receives is referred to as the utility and distributed power control is a noncooperative power control game where users maximize their utility. The outcome of the game results in a Nash equilibrium that is inefficient. We introduce pricing of transmit powers in order to obtain Pareto improvement of the noncooperative power control game, i.e., to obtain improvements in user utilities relative to the case with no pricing. Specifically, we consider a pricing function that is a linear function of the transmit power. The simplicity of the pricing function allows a distributed implementation where the price can be broadcast by the base station to all the terminals. We see that pricing is especially helpful in a heavily loaded system. Index Terms—Game theory, Pareto efficiency, power control, pricing, wireless data. I.
Crosslayer optimization for OFDM wireless network Part I: Theoretical framework
 IEEE TRANS. WIRELESS COMMUN
, 2005
"... In this paper, we provide a theoretical framework for crosslayer optimization for orthogonal frequency division multiplexing (OFDM) wireless networks. The utility is used in our study to build a bridge between the physical layer and the media access control (MAC) layer and to balance the efficien ..."
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Cited by 120 (3 self)
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In this paper, we provide a theoretical framework for crosslayer optimization for orthogonal frequency division multiplexing (OFDM) wireless networks. The utility is used in our study to build a bridge between the physical layer and the media access control (MAC) layer and to balance the efficiency and fairness of wireless resource allocation. We formulate the crosslayer optimization problem as one that maximizes the average utility of all active users subject to certain conditions, which are determined by adaptive resource allocation schemes. We present necessary and sufficient conditions for utilitybased optimal subcarrier assignment and power allocation and discuss the convergence properties of optimization. Numerical results demonstrate a significant performance gain for the crosslayer optimization and the gain increases with the number of active users in the networks.
QoS and Fairness Constrained Convex Optimization of Resource Allocation for Wireless Cellular and Ad Hoc Networks
 in Proc. IEEE Infocom
, 2002
"... For wireless cellular and ad hoc networks with QoS constraints, we propose a suite of problem formulations that allocate network resources to optimize SIR, maximize throughput and minimize delay. The distinguishing characteristics of these resource allocation formulations is that, by using convex op ..."
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Cited by 85 (10 self)
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For wireless cellular and ad hoc networks with QoS constraints, we propose a suite of problem formulations that allocate network resources to optimize SIR, maximize throughput and minimize delay. The distinguishing characteristics of these resource allocation formulations is that, by using convex optimization, they accommodate a variety of realistic QoS and fairness constraints. Their globally optimal solutions can be computed efficiently through polynomial time interior point methods, even though they use nonlinear objectives and constraints.
Attainable Throughput of an InterferenceLimited MultipleInput MultipleOutput (MIMO) Cellular System
, 2001
"... We investigate the high spectral efficiency capabilities of a cellular data system that combines the following: 1) multiple transmit signals, each using a separately adaptive modulation; 2) adaptive array processing at the receiver; and 3) aggressive frequency reuse (reuse in every cell). We focus ..."
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Cited by 41 (0 self)
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We investigate the high spectral efficiency capabilities of a cellular data system that combines the following: 1) multiple transmit signals, each using a separately adaptive modulation; 2) adaptive array processing at the receiver; and 3) aggressive frequency reuse (reuse in every cell). We focus on the link capacity between one user and its serving base station, for both uncoded and ideally coded transmissions. System performance is measured in terms of average data throughput, where the average is over user location, shadow fading, and fast fading. We normalize this average by the total bandwidth, call it the mean spectral efficiency, and show why this metric is a useful representation of system capability. We then quantify it, using simulations, to characterize multipleinput multipleoutput systems performance for a wide variety of channel conditions and system design options.
Long Range Prediction of Fading Signals: Enabling Adaptive Transmission for Mobile Radio Channels
 IEEE SIGNAL PROCESSING MAGAZINE
, 2000
"... Recently it was proposed to adapt several transmission methods, including modulation, power control, channel coding and antenna diversity to rapidly time variant fading channel conditions. Prediction of the channel coefficients several tenstohundreds of symbols ahead is essential to realize these ..."
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Cited by 38 (3 self)
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Recently it was proposed to adapt several transmission methods, including modulation, power control, channel coding and antenna diversity to rapidly time variant fading channel conditions. Prediction of the channel coefficients several tenstohundreds of symbols ahead is essential to realize these methods in practice. We describe a novel adaptive long range fading channel prediction algorithm (LRP) and its utilization with adaptive transmission methods. This channel prediction algorithm computes the linear Minimum Mean Squared Error (MMSE) estimates of future fading coefficients based on past observations. This algorithm can forecast fading signals far into the future due to its significant memory span, achieved by using a sufficiently low sampling rate for a given fixed filter size. The LRP is validated for standard stationary fading models, and tested with measured data and with data produced by our novel realistic physical channel model. This model accounts for the variation of the amplitude, frequency and phase of each reflected component of the fading signal. Both numerical and simulation results show that long range prediction makes adaptive transmission techniques feasible for mobile radio channels.
Simultaneous routing and power allocation in CDMA wireless data networks
 IEEE Trans. on Communications
, 2003
"... Abstract — The optimal routing of data in a wireless network depends on the link capacities, which, in turn, are determined by the allocation of transmit powers across the network. Thus, the optimal network performance can only be achieved by simultaneous optimization of routing and power allocation ..."
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Cited by 35 (6 self)
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Abstract — The optimal routing of data in a wireless network depends on the link capacities, which, in turn, are determined by the allocation of transmit powers across the network. Thus, the optimal network performance can only be achieved by simultaneous optimization of routing and power allocation. In this paper, we study this joint optimization problem in CDMA data networks using convex optimization techniques. Although link capacity constraints of CDMA systems are not jointly convex in rates and powers, we show that coordinate projections or transformations allow the simultaneous routing and power allocation problem to be formulated as (in systems with interference cancellation) or approximated by (in systems without interference cancellation) a convex optimization problem which can be solved very efficiently. We also propose a heuristic linkremoval procedure based on the convex approximation to further improve the system performance. I.
Adaptation, Coordination and Distributed Resource Allocation in InterferenceLimited Wireless Networks
"... A sensible design of wireless networks involves striking a good balance between an aggressive reuse of the spectral resource throughout the network and managing the resulting cochannel interference. Traditionally this problem has been tackled using a “divide and conquer” approach. The latter consis ..."
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Cited by 35 (3 self)
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A sensible design of wireless networks involves striking a good balance between an aggressive reuse of the spectral resource throughout the network and managing the resulting cochannel interference. Traditionally this problem has been tackled using a “divide and conquer” approach. The latter consists in deploying the network with a static or semidynamic pattern of resource reutilization. The chosen reuse factor, while sacrificing a substantial amount of efficiency, brings the interference to a tolerable level. The resource can then be managed in each cell so as to optimize the per cell capacity using an advanced air interface design. In this paper we focus our attention on the overall network capacity as a measure of system performance. We consider the problem of resource allocation and adaptive transmission in multicell scenarios. As a key instance, the problem of joint scheduling and power control simultaneously in multiple transmitreceive links, which employ capacityachieving adaptive codes, is studied. In principle, the solution of such an optimization hinges on tough issues such as the computational complexity and the requirement for heavy receivertotransmitter feedback and, for cellular networks, celltocell channel state information (CSI) signaling. We give asymptotic properties pertaining to ratemaximizing power control and scheduling in multicell networks. We then present some promising leads for substantial complexity and signaling reduction via the use of newly developed distributed and game theoretic techniques.
Dynamic Frequency Allocation in Fractional Frequency Reused OFDMA Networks”, to appear at the 4
 th IEEE Workshop on Broadband Wireless Access
, 2008
"... Abstract—This paper proposes a dynamic fractional frequency reused cell architecture that simplifies the problem of subcarrier allocation with frequency reuse in multicell OFDMA networks. The architecture divides the cell surface into two overlapping geographical regions and orthogonally allocates s ..."
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Cited by 33 (0 self)
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Abstract—This paper proposes a dynamic fractional frequency reused cell architecture that simplifies the problem of subcarrier allocation with frequency reuse in multicell OFDMA networks. The architecture divides the cell surface into two overlapping geographical regions and orthogonally allocates subcarriers, which are called super and regular group of subcarriers, to the regions. The proposed architecture allows a frequency reuse factor of 1 with reduced intercell interference and increased trunking gain, while satisfying minimum data rate requirements. We also propose an efficient hierarchical solution to realize the proposed architecture. The solution first allocates subcarriers to the groups so that long term performance is maximized and next opportunistically schedules subcarriers to the users. The opportunistic scheduling is performed at the base stations considering the fairness requirements of the users. Simulation results illustrate the performance improvements of the proposed solution in comparison to the traditional frequency allocation schemes. Index Terms—Wireless communication, mobile communication systems, cellular networks, 3G, crosslayer adaptation, opportunistic scheduling, data networks. I.
Optimal power allocation and scheduling for twocell capacity maximization
 in Proceedings of the IEEE RAWNET (WiOpt
, 2006
"... Abstract — We consider the problem of optimally allocating the base station transmit power in two neighboring cells for a TDMA wireless cellular system, to maximize the total system throughput under interference and noise impairments. Employing dynamic reuse of spectral resources, we impose a peak p ..."
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Cited by 30 (7 self)
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Abstract — We consider the problem of optimally allocating the base station transmit power in two neighboring cells for a TDMA wireless cellular system, to maximize the total system throughput under interference and noise impairments. Employing dynamic reuse of spectral resources, we impose a peak power constraint at each base station and allow for coordination between the base stations. By an analytical derivation we find that the optimal power allocation then has a remarkably simple nature: Depending on the noise and channel gains, transmit at full power only at base station 1 or base station 2, or both. Utilizing the optimal power allocation we study optimal link adaptation, and compare to adaptive transmission without power control. Results show that allowing for power control significantly increases the overall capacity for an average user pair, in addition to considerable power savings. Furthermore, we investigate power adaptation in combination with scheduling of users in a time slotted system. Specifically, the capacityoptimal singlecell scheduler [1] is generalized to the twocell case. Thus, both power allocation and multiuser diversity are exploited to give substantial network capacity gains. I.