Optimal Subcarrier Power Allocation Research Articles

Power Allocation for OFDM Wireless Network Localization Under Expectation and Robustness Constraints

In location-aware wireless networks, mobile nodes (agents) can obtain their positions using range measurements to other nodes with known positions (anchors). Optimal subcarrier power allocation at the anchors reduces positioning error and improves network lifetime and throughput. We present an optimization framework for subcarrier power allocations in network localization with the imperfect knowledge of network parameters based on the fundamental statistical limits. Power allocations with expectation and robustness constraints are obtained using semidefinite optimization problems in non-iterative and iterative forms with both unicast and multicast transmissions. Results show that the allocations provide more accurate localization than non-robust designs under channel and agents positions uncertainty.

Optimal Subcarrier Power Allocation for OFDM with Low Precision ADC at Receiver

Motivated by the need to reduce power consumption in the receiver analog-to-digital converter (ADC) in multi-Gbps communication systems, in this paper, we study subcarrier power allocation based on channel side information (CSI) at the transmitter. We derive a fixed point equation for subcarrier power allocation that minimizes uncoded symbol error rate (SER) when a finite precision ADC is used at the receiver. We study the sensitivity of the optimal power allocation with respect to a parameter that depends on the ADC precision. Based on this, we propose a simple analytical approximation for the optimal power allocation, which performs within 0.5 dB of the exact case over a wide range of signal-to-noise ratio (SNR). The proposed power allocation leads to only a small increase in the peak-to-average power ratio (PAPR) (< 0.3 dB) for channel models suggested in IEEE 802.15.3c. Further, for a 16-QAM input, 7/8 rate low density parity check (LDPC) code and 3-bit precision ADC, it attains a coded bit error rate (BER) of 10^{-5} at a SNR of 23.5 dB, which compares favorably with the 25 dB required by a traditional system with equal power allocation across the subcarriers and infinite sampling precision. We also show the robustness of the performance gain to channel estimation errors.