Power Efficient Pilot Symbol Power Allocation under Time-Variant Channels

Current Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) based systems for wireless communications enable to adjust power radiated at the pilot symbols. Under time-invariant channels, a power increase at the pilot symbols results in improved quality of the channel estimate. However, under time-variant channels, this is not necessarily the case. Due to the decreased temporal channel correlation, the channel estimation performance becomes saturated. If under time-variant channels more power is assigned to the data symbols, such approach increases inter layer interference due to the imperfect channel knowledge at the receiver. In this paper, we show how to distribute power among data and pilot symbols in a power efficient way. Using our proposed method, up to 50% of the transmit power can be saved in a 4x4 Long Term Evolution (LTE) downlink transmission at a Signal to Noise Ratio (SNR) of 20 dB.