OFDM power loading using limited feedback

• Published in: IEEE transactions on vehicular technology Vol. 54; no. 5; pp. 1773 - 1780
• Main Authors: Love, D.J., Heath, R.W.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.09.2005; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Allocations; Applied sciences; Channels; Error analysis; Exact sciences and technology; Fading; Feedback; Frequency conversion; Frequency division multiplexing; Frequency estimation; Information, signal and communications theory; Limited feedback; Materials science and technology; Mathematical analysis; Multiplexing; OFDM; Orthogonal Frequency Division Multiplexing; power loading; Radio spectrum management; Receivers; Signal and communications theory; Symbols; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmission and modulation (techniques and equipments); Transmitters; Vectors (mathematics); Wireless networks; Fading channels; power loading; Simulation; Wireless telecommunication; Resource allocation; Orthogonal frequency division multiplexing; Feedback regulation; Limited feedback; Multipath channels; Optimization
• ISSN: 0018-9545; 1939-9359
• DOI: 10.1109/TVT.2005.853473

Orthogonal frequency division multiplexing (OFDM) is a practical broadband signaling technique for use in multipath fading channels. Over the past ten years, research has shown that power loading, where the power allocations on the OFDM frequency tones are jointly optimized, can improve error rate or capacity performance. The implementation of power loading, however, is dependent on the presence of complete forward link channel knowledge at the transmitter. In systems using frequency division duplexing (FDD), this assumption is unrealistic. In this paper, we propose power loading for OFDM symbols using a limited number of feedback bits sent from the receiver to the transmitter. The power loading vector is designed at the receiver, which is assumed to have perfect knowledge of the forward link channel, and conveyed back to the transmitter over a limited rate feedback channel. To allow for the vector to be represented by a small number of bits, the power loading vector is restricted to lie in a finite set, or codebook, of power loading vectors. This codebook is designed offline and known a priori to both the transmitter and receiver. We present two power allocation selection algorithms that optimize the probability of symbol error and capacity, respectively. Simulation results show that the proposed limited feedback techniques provide performance close to full channel knowledge power loading.