Wideband MIMO measurements of outdoor NLOS channels

Abstract

ABSTRACT:The measurement results of the wideband wireless multiple-input multiple-output ( MIMO) INTRODUCTIONMultiple-input multiple-output (MIMO) communication systems with multiple antennas at both the transmitter (TX) and the receiver (RX) ends have shown the potential of increased capacity in wireless channels. Realistic MIMO channels, however, usually contain some degree of spatial correlation among the multiple transmitting and receiving antennas. Consequently, the practical capacity may be lower than that expected from theoretical considerations [1]. During the past few years, researchers have used different ways to measure MIMO channel features. For example, a narrowband MIMO channel sounder with 16 transmitting antennas and 16 receiving antennas was employed to measure the channel characteristics in Manhattan [2]. A 2 TX by 2 RX wideband orthogonal frequency division multiplexing (OFDM) channel sounder was used to measure channel-impulse responses in suburban Chicago [3]. An 8 TX by 8 RX virtual wideband MIMO channel sounder that used fast switches at both the TX and RX ends was utilized to probe the indoor MIMO channels in picocell environments [4]. This paper presents the results of wideband wireless MIMO channel measurements with a true array channel sounder. Wideband MIMO channel measurement poses a challenge due to the high-data-acquisition requirement. Our system uses spread spectrum to simultaneously transmit multiple pseudo-random signals. Multiple receivers then receive the transmitted signals simultaneously. Such a system can most faithfully capture the wideband MIMO channel features in a real environment. A series of field measurements under non-line-of-sight (NLOS) scenarios is conducted at the J. J. Pickle Research Campus, the University of Texas at Austin. From the raw channel data, power delay profiles are extracted based on the cross-correlation property between the transmitted and received signals. MIMO channel capacities are then calculated from the measured channel data and compared with the independent, identically distributed (iid) channel simulation. MEASUREMENT SETUPOur wideband channel sounder consists of four transmitters and eight receivers that operate at a carrier frequency of 1.8 GHz. Each transmitter transmits the shifted version of a pseudo-random signal with a bandwidth of 2.5 MHz. The data length of a period of the TX sequence is 752. The four TX data sequences are simultaneously converted into analog baseband signals via four digitalto-analog converters and a field-programmable grid array. They are then mixed with an intermediate frequency (IF) local oscillator signal, and upconverted into radio frequency (RF) signals at 1.8 GHz. In the RX testbed, the RF signals are first down-converted to IF signals at 138.625 MHz, and then demodulated into baseband signals. Eight pairs of in-phase and quadrature-phase baseband signals are sent to four National Instruments data acquisition cards (PCI-6115). The sampling rate of the analog-to-digital converter is 10 MHz. The baseban...

Modelling and simulation of channel power delay profile under indoor stair environment

“…Then, the capacity distributions of the measured data, proposed model, and model in [13] are calculated and shown in Fig. 6 c (SNR = 20 dB) [25]. The mean values of the capacities are 2.64, 2.65 and 3.05 bit/s/Hz, and their standard deviations are 0.36, 0.33 and 0.29 bit/s/Hz.…”

Delay Spread Characteristics of Wideband MIMO Channels Based on Outdoor Non-Line-of-Sight Measurements

“…The four transmitters transmit the probing signals at the same time and the eight Rx antennas receive the training signals simultaneously. Based on the measured data, an experimental investigation on wideband MIMO channel characteristics was reported in [9], and the realistic channel capacity, together with the comparison to ideal Rayleigh channel simulation, was reported in [10].…”