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29
Energy-constrained modulation optimization
- IEEE Transactions on Wireless Communications
, 2005
"... Abstract — We consider wireless systems where the nodes operate on batteries so that energy consumption must be minimized while satisfying given throughput and delay requirements. In this context, we analyze the best modulation strategy to minimize the total energy consumption required to send a giv ..."
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Cited by 159 (8 self)
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Abstract — We consider wireless systems where the nodes operate on batteries so that energy consumption must be minimized while satisfying given throughput and delay requirements. In this context, we analyze the best modulation strategy to minimize the total energy consumption required to send a given number of bits. The total energy consumption includes both the transmission energy and the circuit energy consumption. For uncoded systems, by optimizing the transmission time and the modulation parameters we show that up to 80 % energy savings is achievable over non-optimized systems. For coded systems, we show that the benefit of coding varies with the transmission distance and the underlying modulation schemes. Index Terms — Energy efficiency, modulation optimization, MQAM, MFSK.
Optimal packet scheduling on an energy harvesting broadcast link
- IEEE J. Sel. Areas Commun
, 2011
"... The minimization of transmission completion time for a given number of bits per user in an energy harvesting communication system, where energy harvesting instants are known in an offline manner is considered. An achievable rate region with structural properties satisfied by the 2-user AWGN Broadcas ..."
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Cited by 54 (1 self)
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The minimization of transmission completion time for a given number of bits per user in an energy harvesting communication system, where energy harvesting instants are known in an offline manner is considered. An achievable rate region with structural properties satisfied by the 2-user AWGN Broadcast Channel capacity region is assumed. It is shown that even though all data are available at the beginning, a non-negative amount of energy from each energy harvest is deferred for later use such that the transmit power starts at its lowest value and rises as time progresses. The optimal scheduler ends the transmission to both users at the same time. Exploiting the special structure in the problem, the iterative offline algorithm, FlowRight, from earlier literature, is adapted and proved to solve this problem. The solution has polynomial complexity in the number of harvests used, and is observed to converge quickly on numerical examples. Index Terms Packet scheduling, energy harvesting, AWGN broadcast channel, flowright, energy-efficient scheduling.
Gamal, “On adaptive transmission for energy efficiency in wireless data networks
- IEEE Transactions on Information Theory
, 2004
"... Abstract—This paper investigates the problem of energy-efficient transmission of data packets in a wireless network by jointly adapting to backlog and channel condition. Specifically, we consider minimum-energy scheduling problems over multiple-access channels, broadcast channels, and channels with ..."
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Cited by 47 (3 self)
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Abstract—This paper investigates the problem of energy-efficient transmission of data packets in a wireless network by jointly adapting to backlog and channel condition. Specifically, we consider minimum-energy scheduling problems over multiple-access channels, broadcast channels, and channels with fading, when packets of all users need to be transmitted before a deadline. Earlier work has considered a similar setup and demonstrated significant transmission energy saving by adapting to backlog for channels that are time invariant and when transmission is restricted to time-division. For concreteness, throughout the paper, rates and powers corresponding to optimal coding over discrete-time additive white Gaussian noise (AWGN) channels are assumed. The results, however, hold for more general channels and coding schemes where the total transmitted power is convex in the transmission rates. The offline scheduling problems for all the channels considered are shown to reduce to convex optimization problems with linear constraints. An iterative algorithm, referred to as FlowRight, that finds optimal offline schedules is presented. A heuristic online algorithm that we call look-ahead water-filling, which jointly adapts to both channel fading state and backlog is described. By the use of a small buffer which introduces an almost fixed delay, this algorithm achieves a considerable reduction in energy relative to water filling solely on channel states. Index Terms—Adaptive transmission, broadcast, energy-efficient transmission, iterative algorithm, multiple-access, power
Cross-layer optimization for energy-efficient wireless communications: a survey,” to be published
"... Abstract—Since battery technology has not progressed as rapidly as semiconductor technology, power efficiency has be-come increasingly important in wireless networking, in addition to the traditional quality and performance measures, such as bandwidth, throughput, and fairness. Energy-efficient desi ..."
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Cited by 45 (7 self)
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Abstract—Since battery technology has not progressed as rapidly as semiconductor technology, power efficiency has be-come increasingly important in wireless networking, in addition to the traditional quality and performance measures, such as bandwidth, throughput, and fairness. Energy-efficient design requires a cross layer approach as power consumption is affected by all aspects of system design, ranging from silicon to applica-tions. This article presents a comprehensive overview of recent advances in cross-layer design for energy-efficient wireless com-munications. We particularly focus on a system-based approaches towards energy optimal transmission and resource management across time, frequency, and spatial domains. Details related to energy-efficient hardware implementations are also covered. Index Terms – energy efficiency, cross-layer, wireless commu-nications, energy aware I.
A Calculus Approach to Energy-Efficient Data Transmission with Quality-of-Service Constraints
"... Transmission rate adaptation in wireless devices provides a unique opportunity to trade-off data service rate with energy consumption. In this paper, we study optimal ratecontrol to minimize the transmission energy expenditure subject to strict deadline or other quality-of-service (QoS) constraints ..."
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Cited by 40 (1 self)
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Transmission rate adaptation in wireless devices provides a unique opportunity to trade-off data service rate with energy consumption. In this paper, we study optimal ratecontrol to minimize the transmission energy expenditure subject to strict deadline or other quality-of-service (QoS) constraints. Specifically, the system consists of a wireless transmitter with controllable transmission rate and with strict QoS constraints on data transmission. The goal is to obtain a rate control policy that minimizes the total transmission energy expenditure while ensuring that the QoS constraints are met. Using a novel formulation based on cumulative curves methodology, we obtain the optimal transmission policy and show that it has a simple and appealing graphical visualization. Utilizing the optimal “offline” results, we then develop an online transmission policy for an arbitrary stream of packet arrivals and deadline constraints, and show, via simulations, that it is significantly more energy efficient than a simple head-of-line drain policy. Finally, we generalize the optimal policy results to the case of time-varying power-rate functions.
Delay-constrained Scheduling: Power Efficiency, Filter Design, and Bounds
- IEEE INFOCOM, Hong Kong
, 2004
"... In this paper, packet scheduling with maximum delay constraints is considered with the objective to minimize average transmit power over Gaussian channels. The main emphasis is on deriving robust schedulers which do not rely on the knowledge of the source arrival process. Towards that end, we first ..."
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Cited by 32 (2 self)
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In this paper, packet scheduling with maximum delay constraints is considered with the objective to minimize average transmit power over Gaussian channels. The main emphasis is on deriving robust schedulers which do not rely on the knowledge of the source arrival process. Towards that end, we first show that all schedulers (robust or otherwise) which guarantee a maximum queuing delay for each packet are equivalent to a time-varying linear filter. Using the connection between filtering and scheduling, we study the design of optimal power minimizing robust schedulers. Two cases, motivated by filtering connection, are studied in detail. First, a time-invariant robust scheduler is presented and its performance is completely characterized. Second, we present the optimal time-varying robust scheduler, and show that it has a very intuitive time water-filling structure. We also present upper and lower bounds on the performance of power-minimizing schedulers as a function of delay constraints. The new results form an important step towards understanding of the packet time-scale interactions between physical layer metric of power and network layer metric of delay.
A Power Saving MAC Protocol for Wireless Networks
- in Proceedings of Infocom
, 2002
"... This paper presents a protocol which improves on the power saving mechanism in the IEEE 802.11 Distributed Coordination Function (DCF). In the power saving mechanism (PSM) for DCF, all nodes are synchronized by beacons. In each beacon interval, there is a fixed time interval called the ATIM window w ..."
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Cited by 15 (1 self)
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This paper presents a protocol which improves on the power saving mechanism in the IEEE 802.11 Distributed Coordination Function (DCF). In the power saving mechanism (PSM) for DCF, all nodes are synchronized by beacons. In each beacon interval, there is a fixed time interval called the ATIM window where every node has to be awake. During the ATIM window, a source node informs a destination node about a pending packet by transmitting an ATIM frame. When the destination node receives an ATIM frame, it replies with an ATIM-ACK. Both the source and destination nodes stay awake for the remaining beacon interval. The source can transmit data after the ATIM window finishes. A node that does not have traffic to send or receive can enter the doze state after its ATIM window finishes. During the ATIM window in PSM, no data transmission is allowed. Thus, the available bandwidth in PSM is reduced according to the ATIM window size. Also, energy is consumed in transmitting and receiving ATIM and ATIM-ACK frames. This paper proposes a protocol that removes the overhead of the ATIM window and uses the bandwidth for data transmission. Simulation results show that removing the ATIM window gives better aggregate throughput and energy saving.
Practical lazy scheduling in sensor networks
- in Proceedings of ACM Conference on Embedded Sensor Systems
, 2003
"... ABSTRACT Experience has shown that the power consumption of sensors andother wireless computational devices is often dominated by their communication patterns. We present a practical realization of lazypacket scheduling that attempts to minimize the total transmission energy in a broadcast network b ..."
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Cited by 12 (2 self)
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ABSTRACT Experience has shown that the power consumption of sensors andother wireless computational devices is often dominated by their communication patterns. We present a practical realization of lazypacket scheduling that attempts to minimize the total transmission energy in a broadcast network by dynamically adjusting each node'stransmission power and rate on a per-packet basis. Lazy packet scheduling leverages the fact that many channel coding schemesare more efficient at lower transmission rates; that is, the energy required to send a fixed amount of data can be reduced by transmit-ting the data at a lower bit rate and transmission power. The optimal per-packet transmission rate in a multi-node net-work is governed in practice by the available bit rates of the given transceiver(s), the nodes ' delay tolerance, and the offered load atevery node contending for the shared broadcast channel. We propose an extension to the traditional CSMA/CA MAC scheme calledL-CSMA/CA that allows individual nodes to continually estimate the current demand for a broadcast channel and adjust their trans-mission schedules accordingly. Our simulation results show that L-CSMA/CA can provide improved energy efficiency in a single-hop, broadcast network (20-25 % with more than 10 nodes, and up to 99 % for four nodes with a standard power function) for bothPoisson and bursty arrivals with only minor degradation the capacity of the channel. 1.
Energy-Efficient Wireless Packet Scheduling with Quality of Service Control
, 2007
"... In this paper, we study the problem of packet scheduling in a wireless environment with the objective of minimizing the average transmission energy expenditure under individual packet delay constraints. Most past studies assumed that the input arrivals followed a Poisson process or were statistical ..."
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Cited by 12 (3 self)
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In this paper, we study the problem of packet scheduling in a wireless environment with the objective of minimizing the average transmission energy expenditure under individual packet delay constraints. Most past studies assumed that the input arrivals followed a Poisson process or were statistically independent. However, traffic from a real source typically has strong time correlation. We model a packet scheduling and queuing system for a general input process in linear time-invariant systems. We propose an energy-efficient packet scheduling policy that takes the correlation into account. Meanwhile, a slower transmission rate implies that packets stay in the transmitter for a longer time, which may result in unexpected transmitter overload and buffer overflow. We derive the upper bounds of the maximum transmission rate under an overload probability and the upper bounds of the required buffer size under a packet drop rate. Simulation results show that the proposed scheduler improves up to 15 percent in energy savings compared with the policies that assume statistically independent input. Evaluation of the bounds in providing QoS control shows that both deadline misses and packet drops can be effectively bounded by a predefined constraint.
Continuous-time Optimal Rate Control for Delay Constrained Data Transmission
- 43rd Annual Allerton Conference on Communication, Control and Computing
, 2005
"... We consider optimal rate control for delay constrained data transmission, over time varying channels, with the objective of minimizing the transmission energy expenditure. Energy efficiency is achieved by spreading the data transmission over time to exploit the convexity of the power-rate functions ..."
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Cited by 8 (5 self)
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We consider optimal rate control for delay constrained data transmission, over time varying channels, with the objective of minimizing the transmission energy expenditure. Energy efficiency is achieved by spreading the data transmission over time to exploit the convexity of the power-rate functions and further, by opportunistically adapting the transmission rate to the channel variations. Our system model consists of a buffer with B units of data that must be transmitted by a finite deadline T with minimum energy over a time-varying channel. Using a continuous-time stochastic control formulation, we obtain simple closed form expressions for the optimal transmission rate that minimizes the energy expenditure and meets the deadline constraint. Finally, simulation results compare the gains achieved by the optimal rate adaptation with non-adaptive policies.
