Abstract
We consider a multi-user (MU) multiple-input-single-output (MISO) downlink system with M single-antenna users and N transmit antennas with a nonlinear power amplifier (PA) at each antenna. Instead of emitting constant envelope (CE) signals from the antennas to have highly power efficient PAs, we relax the CE constraint and allow the transmit signals to have instantaneous power less than or equal to the available power at each PA. The PA power efficiency decreases but simulation results show that the same performance in terms of bit-error-ratio (BER) can be achieved with less transmitted power and less PA power consumption. We propose a linear and a nonlinear precoder design to mitigate the multi-user interference (MUI) under the constraint of a maximal instantaneous per-antenna peak power.
Highlights
Power efficiency is a big concern in future communication systems
The performance metrics are on the one hand the uncoded bit-error-ratio (BER) and on the other hand the following characteristic powers that we aim to minimize:
Radiated power Pr in Fig. 3: the effective radio frequency (RF) power transmitted (E[ xPA 22]) that might act as interference for other systems operating in the same frequency band
Summary
Power efficiency is a big concern in future communication systems. As the power amplifier (PA) typically accounts for more than half of the power consumption in a base station (BS) [1], [2], it is desirable in terms of high power efficiency to run the PA in the saturation region. To this end, and based on the above, we relax the CE constraint and let the instantaneous power at each antenna be less than or equal to the maximal available power for each antenna and consider the required system power needed to achieve a certain BER value. Based on the above, we relax the CE constraint and let the instantaneous power at each antenna be less than or equal to the maximal available power for each antenna and consider the required system power needed to achieve a certain BER value In this case, the PA operating region is not restricted to the saturation region but is extended to a linear region and a saturation region. The vector el represents a zero vector with 1 in the l-th position. diag(A) denotes a diagonal matrix containing only the diagonal elements of A
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