Measurement-Based Performance Evaluation of MIMO Spatial Multiplexing in a Multipath-Rich Indoor Environment

Abstract

Abstract-Multiple-input multiple-output (MIMO) spatial multiplexing that needs to separate and detect transmitted signal streams by using processing at the receiver end can increase the data rates of transmissions on independent and identically distributed (i.i.d.) channels. Such channels have been considered to exist in nonline-of-sight (NLOS) environments. However, actual communications may also be conducted in line-of-sight (LOS) environments. While an LOS component can increase the received power level, it may also cause correlated channels that make it difficult to detect the transmitted streams. In this paper, we describe the performance of 4 4 MIMO spatial multiplexing based on LOS and NLOS channel measurements in an indoor environment. For eight configurations of uniform linear arrays (four antenna spacings and two array orientations), we evaluated the cumulative distribution function (CDF) of the channel capacity and bit error rate performance versus transmit power, and we analyzed them in terms of antenna pattern, fading correlation, CDFs of MIMO channel elements, and CDFs of eigenvalues. Results show that, despite higher fading correlations and non i.i.d. channel characteristics, the performance of MIMO spatial multiplexing in the LOS environment is better than that in the NLOS one. However, the performance in the measured LOS environment largely depends on the MIMO configuration.Index Terms-Array element pattern, bit error rate (BER), channel capacity, channel element distribution, eigenvalue distribution, fading correlation, indoor channel measurement, multiple-input multiple-output (MIMO), mutual coupling, spatial multiplexing.

Measurement-Based Performance Evaluation of Coded MIMO-OFDM Spatial Multiplexing with MMSE Spatial Filtering in an Indoor Line-of-Sight Environment

“…In addition to the coded case, we demonstrate the performance without coding for comparison. The uncoded case shows almost the same tendency as the narrowband case reported in [6]- [8]. From the results of the uncoded case, we can see that the LOS condition provides better BER performance compared with the NLOS condition.…”

“…(The number of antenna pairs in a four-element array is six). Details on the correlations are discussed in [7], [8]. Here the normalized total TX power denotes the total TX power yielding average E s /N 0 of 0 dB in the case of single-antenna OFDM transmission in an anechoic chamber with the same measurement setup.…”

“…In the LOS condition there was no obstructing object between the TX and RX tables, and in the NLOS condition a metal partition was located between them. The estimated K-factor in the LOS condition was 1.66 dB in single-antenna measurement without mutual coupling effect [8]. By changing TX and RX array positions, we obtained 7 × 7 = 49 spatially different data while keeping the distance of 4 m between the TX and RX tables, where an interval between adjacent array positions was λ/4 (1.5 cm) [7]- [9].…”

“…Details on the measurement setup are presented in [6]- [9]. Also, details on the K-factor estimation and characteristics of the measured channel data, e.g., CDFs of channel amplitudes, etc., are reported mainly in [8].…”

“…Therefore, it has been widely investigated, and some standardization groups have planned to incorporate it or have already determined to do so [3]- [5]. So far, the authors have conducted MIMO channel measurement campaigns and studied the performance of narrowband MIMO spatial multiplexing in indoor environments [6]- [8]. It was found that the uncoded performance of spatial multiplexing in line-of-sight (LOS) environments generally outperforms that in non-LOS (NLOS) ones under the same transmit power condition even though the existence of direct wave increases fading correlations in LOS environments.…”