Experimental Validation of SIMO-TR

The proposed SIMO-TR is experimentally validated using two antennas at the receiver side in a reverberation chamber, which is an ideal test environment present inside the IETR laboratory, with the dimensions of 8.7 m×3.7m×2.9 m.

2.8.2.1 Experimental Setup

An experimental setup similar to the one shown in Fig. 2.32 is established in the RC. The only difference is that only one antenna is used at the transmitting end.

A log-periodic antenna is used at the transmitting end and two identical CMAs are used at the receiving end. The radiation patterns of both antennas are uniform in the azimuth plane and are vertically polarized with a separation of 10 cm. The distance between the transmitter and the receiver is 6m and the antennas are kept 1m above the ground.

A very narrow pulse is generated with an AWG, which has a maximum sampling rate of 5 GS/s to measure the channel response. At the receiver end, the received signal is captured by a DSO with a maximum sampling rate of 40GS/s. The DSO is operated in the average mode so that 256 samples of the received signals are recorded

and averaged together to reduce the noise. Once the channel responses of both chan-nels are measured, the MCRs are truncated for 85% of the energy, reversed in time, added together, normalized to the equal power and then re-transmitted by using the AWG in the same channel. A very high quality signal is received at both of the receiving antennas.

Fig. 2.38 shows the PDP of the received signals at two antennas normalized to the maximum peak power of the SISO-TR scheme. As expected, the power of the peak is lesser than the peak power of the SISO-TR. It is the multiplexing gain and not the diversity gain which increases the capacity of the proposed transmission approach.

The two signals have signal to side lobe ratio (SSR) of 7.5 dB which is better than the SSR of the SISO-TR (in the order of 5 dB) which suggests that the SIMO-TR will perform better in high data rate applications where SSR is of great importance.

1.1999 1.2 1.2001 1.2002 x 10⁴ 0

0.2 0.4 0.6 0.8 1

Time (ns)

Normalized PDP

SISO−TR R_x1 SIMO R_x2 SIMO

Figure 2.38: Power delay profile of the received signal with SISO-TR and two indi-vidual signals with SIMO-TR

2.9 Conclusion

In this chapter, we presented the validation procedure of the TR scheme. The valida-tion of the TR scheme in the laboratory is performed to study different TR parameters using simulation, semi-measurement and measurement approaches.

In the simulation approach, existing channel models for UWB are used for the val-idation of the TR scheme. PDP of the pulsed UWB and the TR UWB are compared in different types of indoor environments i.e. residential, office and industrial environ-ments. The received signal of the TR scheme is compressed in time. Furthermore, TR validation is carried out by using TD-TLM simulations in a metallic environment with

in the direction where absorbing boundary is placed.

In the semi-measurement approach, the channel response of a typical indoor en-vironment is measured by using the frequency domain instrument (VNA). Thereafter TR communication is simulated and spatial focusing of the TR scheme is analyzed.

It is shown that in a typical indoor environment, the received peak power decreases by 10dB for only 10 cmmovement of the receiver. It is also studied that how differ-ent bandwidths affect the performance and the spatial focusing of the TR scheme by measuring the channel response over a rectangular surface in a reverberation chamber (RC). The results suggest that the dimension of the spatial focusing zone is controlled by the lower frequency of the bandwidth.

TR validation, followed by the parametric analysis of the TR scheme, is performed by using time domain instruments (AWG and DSO). Different TR properties such as normalized peak power (NPP), focusing gain (FG), signal to side-lobe ration (SSR), increased average power (IAP) and RMS delay spread are compared for different configurations with combinations of different environments (LOS and NLOS) and dif-ferent antenna orientations (co-polar and cross-polar). LOS co-polar configuration has the largest received peak power but the lowest SSR, whereas NLOS cross-polar configuration has the lowest received peak power and the highest SSR. For a given channel environment, LOS cross-polar configuration can be a good compromise with larger received power compared to NLOS configurations and equally good perfor-mance. Experiments are also performed in the RC and it is shown that the RC is a very favorable environment for TR.

TR validation is also performed with different bandwidths and it has been found that transmitted signals with higher bandwidths achieve better performance than the signal with lower bandwidths. Experiments are also performed for the TR scheme with different types of antennas. The results suggest that an omni-directional antenna performs better in the environments with a constant multi-path floor or where the direction of arrival for majority of the multi-paths is uniformly spread, whereas a directive antenna is expected to perform significantly better than the omni-directional antenna if the direction of arrival for most of the multi-paths matches with the main lobe of the radiation pattern of the antenna.

TR validation is also preformed with different multi-antenna configurations. It has been found that with multi antenna configurations, a significantly better TR peak performance is achieved with all other properties remain comparable to the SISO-TR scheme. In the end, a multiplexing scheme is described using SIMO-TR scheme, where a multiplexing gain proportional to the number of receiving antennas is achieved and thus capacity of the TR scheme is ameliorated. A comparison of the capacity of the SIMO-TR and MISO-TR schemes is carried out and the results suggest that SIMO-TR scheme attains significantly higher capacity than MISO-TR scheme.