Energy-efficient link adaptation in frequency-selective channels

• Published in: IEEE transactions on communications Vol. 58; no. 2; pp. 545 - 554
• Main Authors: Miao, Guowang, Himayat, Nageen, Li, Geoffrey Ye
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.02.2010; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adaptation; Allocations; Applied sciences; Bandwidth; Battery charge measurement; Channels; Circuits; energy aware; Energy conservation; Energy efficiency; Energy measurement; Energy transmission; Exact sciences and technology; Frequency; frequency selective channel; Information, signal and communications theory; Iterative algorithms; link adaptation; Links; Multiplexing; OFDM; Optimization; Signal and communications theory; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Throughput; Transmission and modulation (techniques and equipments); Upper bound; Fading channels; Energy spectrum; OFDM; energy aware; Information rate; Iterative method; Multimedia communication; Algorithm; Power allocation; Information transmission; Energy savings; Upper bound; Frequency selection; Energetic efficiency; Optimal solution; Electric power consumption; Orthogonal frequency division multiplexing; frequency selective channel; Minimum energy; Metric; Energy efficiency; Form factor; link adaptation
• ISSN: 0090-6778; 1558-0857
• DOI: 10.1109/TCOMM.2010.02.080587

Energy efficiency is becoming increasingly important for small form factor mobile devices, as battery technology has not kept up with the growing requirements stemming from ubiquitous multimedia applications. This paper addresses link adaptive transmission for maximizing energy efficiency, as measured by the "throughput per Joule" metric. In contrast to the existing water-filling power allocation schemes that maximize throughput subject to a fixed overall transmit power constraint, our scheme maximizes energy efficiency by adapting both overall transmit power and its allocation, according to the channel states and the circuit power consumed. We demonstrate the existence of a unique globally optimal link adaptation solution and develop iterative algorithms to obtain it. We further consider the special case of flat-fading channels to develop an upper bound on energy efficiency and to characterize its variation with bandwidth, channel gain and circuit power. Our results for OFDM systems demonstrate improved energy savings with energy optimal link adaptation as well as illustrate the fundamental tradeoff between energy-efficient and spectrum-efficient transmission.