EXPERIMENTS

 

We have two sections of experiments. In the 1st section, we measured the UDP throughput in the indoor and outdoor environments with various distances and offsets. In the 2nd section, we propose our implemented hybrid WiFi-VLC system, which can be connected to Internet. Also, we present the experiments results of throughput and webpage loading time.

 

SECTION ONE

 

Indoor and Outdoor UDP Throughput Test


VLC Transceivers
Outdoor test
Indoor test

In our indoor and outdoor experiments, we measured the UDP throughput from client to server. We alternated the vertical distance bewteen the VLC front-ends and also the horizontal distance between the position of VLC receiver and the center of the light beams, to investigate the different network throughput in different scenarios.The indoor experiment was conducted in the range of 2-15 meters of vertical distance and the ourdoor experiment was conducted in the range of 2-10 meters of vertical distance.


Fig.1 represents the UDP throughput vs. the vertical distance. When the vertical distance is 2 meters, our VLC devices can achieve a raw UDP throughput up to 74 Mbps and the network throughput will drop to around 25 Mbps when the vertical distance increase to 5 meters. Note that the vertical distance will be in this range for most of the indoor applications. The throughtput results for the outdoor configurations are very close to those for the indoor settings. Note that the outdoor scenarios may represents the extreme situtations that can happen indoor, in which we have many open windows and extensive lighting. The results show that our VLC devices suit these extreme indoor conditions well.


Fig.2 show the UDP throughput variance when we change the horizontal distance between the position of VLC receiver and the center of light beams. At the edge of light cover area, the throughput drops drastically.


Fig.1:Throughput vs Distance Fig.2:Throughput vs Offset

SECTION TWO

 

 

We have also implemented a hybrid WiFi-VLC system that incorporated uplink WiFi and downlink VLC. We conducted two experiments to evaluate the different performance of WiFi only and hybrid VLC. In these two experiments, all the contending users were WiFi only users. We only changed the user as client from WiFi only configuration ot hybrid VLC and measure the throughput or webpage loading time only on the client.


We compared the performance of client connected to server through WiFi only and hybrid VLC. The results are shown in Fig.3. In hybrid VLC system, the UDP throughput of that client is almost the same (about 35 Mbps), regardless the number of contending users. However, in WiFi only system, the throughput decrease sharply with the number of other users increasing.


Fig.4 represents the webpage loading time experienced by users for different websites. The total numbers of users connected to the same access point are 10. The results show that the hybrid system can cut the delay by about 60-75% in a crowed wireless communication environment. These attractive results motivate us to propose our hybrid system.



Fig.3 Fig.4

 

The following video on Youtube will show how the hybrid WiFi-VLC system work and the throughput it can achieve.

 

 

The following video on Youtube will show the NLOS VLC experiment.