Bi-Directional Use of Spatial Resources and Effects of Spatial Correlation

Abstract

In multiple antenna systems, spatial fading correlation causes a significant degradation in performance. In this work, a method for reducing the sensitivity to spatial fading correlation through the bi-directional use of spatial resources is investigated. Firstly, the concept of bi-directional use of spatial resources is introduced and the fading characteristics of the proposed bi-directional multiple-input multiple-output (B-MIMO) system are investigated. The achievable rates of the B-MIMO system are then investigated and compared with those of conventional MIMO systems for beamforming and full rank transmission. Based on those results, conditions needed for the B-MIMO system to demonstrate a larger average achievable rate are evaluated. B-MIMO systems are found to efficiently reduce the sensitivity to spatial fading correlation, while supporting comparable achievable rates in spatially white environments.

Transmit antenna-switched receive diversity for bi-directional beamforming in two-way communications

“…5 compares the BER performance of the TAS-BBF scheme and conventional BF schemes with various modulation orders. Because the BBF scheme can achieve approximately 2 times the multiplexing gain of the TAS-BBF and UBF schemes [7], the modulation order must be decreased to keep the comparison fair. Therefore, we define the modulation order for the BBF scheme as QPSK and the modulation order for the UBF and TAS-BBF schemes as 16-QAM, as an example.…”

“…This transmit antenna switching scheme makes it possible to increase the number of independent channel gains that a symbol goes through. 1 Because each node knows its own data and the power of echo interference is large enough to estimate echo channel accurately, up to 70dB of echo interference can be deducted from the desired signal by separating the antennas into mutually exclusive transmit and receive antenna sets (see [7]- [11] and references therein). 2 shows the process associated with the TAS-BBF scheme.…”

“…However, it is possible to a achieve higher diversity order than N r in twoway communications. In the two-way communications scenarios where two nodes exchange data, Ju et al proposed a 'bidirectional BF (BBF) 'system where each link utilizes a subset of the spatial resource bi-directionally while simultaneously using the full bandwidth [7][8][9] [10]. When conventional BF is employed, on the other hand, we call the system a 'unidirectional BF (UBF)' system because all the spatial resources are used in a single transmission direction.…”

Bidirectional Full-Duplex Systems in a Multispectrum Environment

“…The bi-directional full-duplex (BFD) system is currently being investigated as a method for increasing spectrum efficiency in two-way networks [1]. In BFD systems, two nodes can simultaneously transmit and receive their signals by using the frequency resources, thus enabling them to achieve double the system capacity compared to conventional bi-directional half-duplex (BHD) systems [1]- [3].…”

Throughput maximization for full-duplex energy harvesting MIMO communications

“…bi-directional MIMO system with spatial fading correlation was presented in [11]. The maximization of the asymptotic ergodic mutual information for a MIMO bi-directional communication system with imperfect channel state information (CSI) assumptions was the focus of [12].…”