Experimental analysis of single and multiple antenna units in uplink of radio-over-fiber distributed antenna system

Increasing the number of antennas either at the transmitter or receiver has been shown to improve system reliability without occupying additional spectrum. In this paper, we experimentally investigate the error vector magnitude (EVM) of single and multiple remote antenna units (RAU) focusing on uplink transmission. We demonstrate that for 64-QAM modulation, the EVM requirement of 6.5% could be achieved with multiple separated RAUs in situations where a single RAU fails to meet this requirement. The EVM result was obtained as the transmitting device was placed at different locations in a typical office environment with OFDM signals gathered through the RAUs and brought back to a central unit for processing. The EVM results show that using multiple RAUs and an efficient signal combining technique, here, maximal ratio combining (MRC), the EVM performance could reduce by approximately 2% when the distance between the RAUs was 0.3m and further reduced by 4% and 6% when the inter-RAU distance was 2m and 4m, respectively, compared to a single RAU

Radio over fiber transport of mm-wave 2×2 MIMO for spatial diversity and multiplexing

DWDM-RoF transport and photonic generation of millimeter-wave MIMO signals has been demonstrated. Generation and modulation of independent data streams over different wavelengths provides allocation flexibility and centralization. EVM results show that this low-cost technique provides antenna diversity/multiplexing gain for STBC-Alamouti and Zero-Forcing algorithms based OFDM-MIMO

Support of Multi-antenna and Multi-user Systems Using Radio Over Fiber

Analog radio-over-fiber can efficiently support multi-antenna and multi-user techniques for future mobile communications. Experimental results demonstrate that the wider antenna separation that can be provided enhances multi-antenna scheme performance

Demonstration of radio-over-fiber-supported 60 GHz MIMO using separate antenna-pair processing

Coverage at millimeter-wave (mmW) frequencies is a constraining bottleneck. Spatial diversity and spatial multiplexing multiple-input multiple-output (MIMO) improve performance over a spread of user locations and these can benefit from wider antenna spacing. Radio-over-Fiber (RoF) transport provides flexibility in deploying a number of widely-spaced Remote Antenna Units (RAUs) connected to the same Central Unit (CU). Hence, mmW systems with an integrated analog RoF fronthaul are strong candidates for use in future 5G networks. An approach to measure channel coefficients individually for MIMO processing has been demonstrated in a RoF transported 2×2 MIMO system at 60 GHz. Experimental results verify this approach through real 2×2 experiments

Performance analysis of commercial multiple-input-multiple-output access point in distributed antenna system

Abstract: In this paper, we experimentally investigate the throughput of IEEE 802.11n 2x2 multiple-input-multiple-output (MIMO) signals in a radio-over-fiber-based distributed antenna system (DAS) with different fiber lengths and power imbalance. Both a MIMO-supported access point (AP) and a spatial-diversity-supported AP were separately employed in the experiments. Throughput measurements were carried out with wireless users at different locations in a typical office environment. For the different fiber length effect, the results indicate that MIMO signals can maintain high throughput when the fiber length difference between the two remote antenna units (RAUs) is under 100 m and falls quickly when the length difference is greater. For the spatial diversity signals, high throughput can be maintained even when the difference is 150m. On the other hand, the separation of the MIMO antennas allows additional freedom in placing the antennas in strategic locations for overall improved system performance, although it may also lead to received power imbalance problems. The results show that the throughput performance drops in specific positions when the received power imbalance is above around 13dB. Hence, there is a trade-off between the extent of the wireless coverage for moderate bit-rates and the area over which peak bit-rates can be achieved