Emerging applications involving low-cost wireless sensor networks motivate well optimization of orthogonal frequency-division multiplexing (OFDM) in the power-limited regime. To this end, the present paper develops loading algorithms to minimize transmit-power under rate and error probability constraints, using three types of channel state information at the transmitter (CSIT): deterministic (per channel realization) for slow fading links, statistical (channel mean) for fast fading links, and quantized (Q), whereby a limited number of bits are fed back from the transmitter to the receiver. Along with optimal bit and power loading schemes, quantizer designs and reduced complexity alternatives with low feedback overhead are developed to obtain a suite of Q-CSIT-based OFDM transceivers with desirable complexity versus power-consumption tradeoffs. Numerical examples corroborate the analytical claims and reveal that significant power savings result even with a few bits of Q-CSIT.
Bibliographical noteFunding Information:
Manuscript received September 19, 2005; revised April 15, 2006. The work of A. G. Marqués was supported in part by the Spanish Government under Grant TEC2005-06766-C03-01/TCM. This work was supported in part by the USDoD ARO under Grant W911NF-05-1-0283.
- Frequency-selective channels
- Interpolation techniques
- Low-power systems
- Optimization methods
- Orthogonal frequency-division multiplexing (OFDM)
- Quantization techniques