3 research outputs found
Rate Analysis of Two-Receiver MISO Broadcast Channel with Finite Rate Feedback: A Rate-Splitting Approach
To enhance the multiplexing gain of two-receiver Multiple-Input-Single-Output
Broadcast Channel with imperfect channel state information at the transmitter
(CSIT), a class of Rate-Splitting (RS) approaches has been proposed recently,
which divides one receiver's message into a common and a private part, and
superposes the common message on top of Zero-Forcing precoded private messages.
In this paper, with quantized CSIT, we study the ergodic sum rate of two
schemes, namely RS-S and RS-ST, where the common message(s) are transmitted via
a space and space-time design, respectively. Firstly, we upper-bound the sum
rate loss incurred by each scheme relative to Zero-Forcing Beamforming (ZFBF)
with perfect CSIT. Secondly, we show that, to maintain a constant sum rate
loss, RS-S scheme enables a feedback overhead reduction over ZFBF with
quantized CSIT. Such reduction scales logarithmically with the constant rate
loss at high Signal-to-Noise-Ratio (SNR). We also find that, compared to RS-S
scheme, RS-ST scheme offers a further feedback overhead reduction that scales
with the discrepancy between the feedback overhead employed by the two
receivers when there are alternating receiver-specific feedback qualities.
Finally, simulation results show that both schemes offer a significant SNR gain
over conventional single-user/multiuser mode switching when the feedback
overhead is fixed.Comment: accepted to IEEE Transactions on Communication
SNR maximization and modulo loss reduction for Tomlinson-Harashima precoding
Compared to linear precoding, Tomlinson-Harashima precoding (THP) requires less transmit power to eliminate the
spatial interference in a multi-user downlink scenario involving a multi-antenna transmitter and geographically
separated receivers. However, THP gives rise to certain performance losses, referred to as modulo loss and power loss.
Based on the observation that part of the users can omit the modulo operation at the receiver during an entire frame,
we present an alternative detector, which reduces the modulo loss compared to the conventional detector. In
addition, this contribution compares several existing and novel algorithms for selecting the user ordering and the
rotation of the constellations at the transmitter, to increase the SNR at the detector and decrease the modulo loss for
the alternative detector. Compared to the better of linear precoding and THP with conventional detector, the
optimized alternative detector achieves significant gains (up to about 4 dB) for terrestrial wireless communication,
whereas smaller gains (up to about 1 dB) are obtained for multi-beam satellite communication