The mobile-to-mobile communication is important for mobile ad-hoc networks or where the mobile phone acts as a relay point. Here we measured the data transfer capability which is important for data centric applications (e.g. Web, Email,…) . As we have also been interested in how the N770 works in different terrain scenarios, we have realized our measurements both in ideal LOS conditions and with different obstacles such as people on the train, trees, bushes, parking cars, opened window and closed window. We have used iperf [22] on both sides to measure the TCP throughput.
Table 6 shows the results of these measurements.
|
Description |
Average bandwidth (Mbit/s) |
Minimal bandwidth (Mbit/s) |
Maximal bandwidth (Mbit/s) |
|
Through 5 parking cars |
2,75 |
1,13 |
4,48 |
|
Train stop (20 people) ~ 15 m |
4,1 |
4,07 |
4,61 |
|
Train stop with trains ~ 25 m |
2,72 |
1,91 |
3,18 |
|
Train stop without trains ~ 50 m |
3,14 |
2,97 |
3,97 |
|
Square with 3 bushes and two trees in the LOS (~30m) |
4,24 |
3,90 |
4,72 |
|
Inside a saturated train (~20 m) |
4,65 |
4,48 |
4,72 |
|
Between two saturated trains (~ 40 m) |
3,05 |
2,8 |
3,32 |
|
Communication trough opened window |
4,49 |
4,01 |
4,75 |
|
Communication trough closed window |
4,5 |
3,66 |
4,74 |
Table 6
The mobile devices have formed an ad-hoc network. The power level has been set to 20 dBm. It seems that the Nokia770 supports only the 802.b channels in the ad-hoc mode. From the results we can conclude that in open air and partial LOS the devices can provide a useable communication channel.
In the case of the second measurement we have been interested in the distance/data-rate ratio with full LOS. We have used two Nokia770 with 20dBm power level in Ad-Hoc mode. As we have already mentioned, in this mode only 802.11b is supported. We have used iperf for measuring the TCP throughput.
|
Distance (m) |
Min (Mbit/s) |
Max (Mbit/s) |
Average (Mbit/s) |
|
1 |
3,700 |
3,830 |
3,770 |
|
10 |
3,710 |
3,900 |
3,790 |
|
20 |
3,670 |
3,820 |
3,734 |
|
50 |
3,600 |
3,780 |
3,710 |
|
75 |
3,690 |
3,810 |
3,734 |
|
100 |
3,610 |
3,720 |
3,680 |
|
200 |
2,460 |
3,780 |
3,442 |
|
250 |
2,470 |
3,670 |
3,408 |
|
400 |
0,358 |
2,310 |
1,417 |
|
450 |
0,098 |
0,682 |
0,497 |
|
500 |
0,000 |
0,000 |
0,000 |
Table 1
Based on our indoor experience we have been surprised to be able to communicate from 450 m distance on such a small device. Despite of the large distance the bandwidth provided by the devices has been more than enough for a VoIP (16-5kbit/s) communication channel.
From these measurements we can conclude that the radio interface of the Nokia770 makes it suitable for open-door use. If there is LOS or partial LOS, the distance at which they are able to communicate can be as long as 450m. We have concluded that fine tuning the data-rate of the communication channels this value can be extended. This ability makes this device suitable to act as a participating node in an Ad-Hoc or WMN network.