50 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
A Tutorial on Interference Exploitation via Symbol-Level Precoding: Overview, State-of-the-Art and Future Directions
IEEE Interference is traditionally viewed as a performance limiting factor in wireless communication systems, which is to be minimized or mitigated. Nevertheless, a recent line of work has shown that by manipulating the interfering signals such that they add up constructively at the receiver side, known interference can be made beneficial and further improve the system performance in a variety of wireless scenarios, achieved by symbol-level precoding (SLP). This paper aims to provide a tutorial on interference exploitation techniques from the perspective of precoding design in a multi-antenna wireless communication system, by beginning with the classification of constructive interference (CI) and destructive interference (DI). The definition for CI is presented and the corresponding mathematical characterization is formulated for popular modulation types, based on which optimization-based precoding techniques are discussed. In addition, the extension of CI precoding to other application scenarios as well as for hardware efficiency is also described. Proof-of-concept testbeds are demonstrated for the potential practical implementation of CI precoding, and finally a list of open problems and practical challenges are presented to inspire and motivate further research directions in this area
Interference Exploitation via Symbol-Level Precoding: Overview, State-of-the-Art and Future Directions
Interference is traditionally viewed as a performance limiting factor in wireless communication systems, which is to be minimized or mitigated. Nevertheless, a recent line of work has shown that by manipulating the interfering signals such that they add up constructively at the receiver side, known interference can be made beneficial and further improve the system performance in a variety of wireless scenarios, achieved by symbol-level precoding (SLP). This paper aims to provide a tutorial on interference exploitation techniques from the perspective of precoding design in a multi-antenna wireless communication system, by beginning with the classification of constructive interference (CI) and destructive interference (DI). The definition for CI is presented and the corresponding mathematical characterization is formulated for popular modulation types, based on which optimization-based precoding techniques are discussed. In addition, the extension of CI precoding to other application scenarios as well as for hardware efficiency is also described. Proof-of-concept testbeds are demonstrated for the potential practical implementation of CI precoding, and finally a list of open problems and practical challenges are presented to inspire and motivate further research directions in this area
Capacity Achieving by Diagonal Permutation for MU-MIMO channels
Dirty Paper Coding (DPC) is considered as the optimal precoding which
achieves capacity for the Gaussian Multiple-Input Multiple-Output (MIMO)
broadcast channel (BC). However, to find the optimal precoding order, it needs
to repeat N! times for N users as there are N! possible precoding orders. This
extremely high complexity limits its practical use in modern wireless networks.
In this paper, we show the equivalence of DPC and the recently proposed Higher
Order Mercer's Theorem (HOGMT) precoding[1][2] in 2-D (spatial) case, which
provides an alternate implementation for DPC. Furthermore, we show that the
proposed implementation method is linear over the permutation operator when
permuting over multi-user channels. Therefore, we present a low complexity
algorithm that optimizes the precoding order for DPC with beamforming,
eliminating repeated computation of DPC for each precoding order. Simulations
show that our method can achieve the same result as conventional DPC with about
20 dB lower complexity for N = 5 users