Downlink resource allocation in multi-carrier systems: frequency-selective vs. equal power allocation

• Published in: IEEE transactions on wireless communications Vol. 7; no. 10; pp. 3738 - 3747
• Main Authors: LEE, Hyang-Won, CHONG, Song
• Format: Journal Article
• Language: English
• Published: Piscataway, NJ IEEE 01.10.2008; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Algorithms; Allocations; Applied sciences; Approximation; Asymptotic properties; Degradation; Downlink; Dynamic subcarrier and power allocation; equal power allocation; Exact sciences and technology; Information, signal and communications theory; Maximization; Multiplexing; network utility maximization; OFDM; OFDMA downlink; Optimization; Organization, operation and development plans; Policies; Radio spectrum management; Radiocommunications; Resource management; Scheduling algorithm; Signal and communications theory; Signal to noise ratio; Space technology; Studies; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Throughput; Transmission and modulation (techniques and equipments); Utilities; Utility programs; Performance evaluation; equal power allocation; Utility function; Resource allocation; Frequency division multiple access; Equity; Downlink; Dynamic subcarrier and power allocation; Subcarrier; Power allocation; Frequency selection; Multiple frequency; Gradient method; Fading channels; Multicarrier; Frequency allocation; Scheduling; Resource sharing; Algorithm; Carrier frequency; Simulation; OFDMA downlink; network utility maximization; Orthogonal frequency division multiplexing; Resource management; Signal to noise ratio
• ISSN: 1536-1276; 1558-2248
• DOI: 10.1109/T-WC.2008.061110

This paper revisits equal power allocation from the viewpoint of asymptotic network utility maximization (NUM) problem in multi-carrier systems. It is a well-known fact that the equal power allocation is near optimal to the sum capacity maximization problem in high SNR (signal-to-noise ratio) regime, i.e., optimal water-filling approximates to equal power allocation in that case. Due to this property together with its simplicity, the equal power allocation has been adopted in several researches, but its performance in other problems has not been clearly understood. We evaluate the suitability of equal power allocation in NUM problem which turns into various resource sharing policies according to utility functions. Namely, our conclusion is that in frequency selective channels, the equal power allocation is near optimal for efficiency-oriented resource sharing policy, but when fairness is emphasized, its performance is severely degraded and thus frequency-selective power allocation is necessary. For this, we develop a suboptimal subcarrier and frequency-selective power allocation algorithm for asymptotic NUM problem using the gradient-based scheduling theory and compare the performance of equal power allocation and the developed algorithm. Extensive simulation results are presented to verify our arguments.