Evaluation of Two Fully Rugged Laptop Computers for the Forest Service, Page17

Evaluation of Two Fully Rugged Laptop Computers for the Forest Service

Appendix J—Wireless Networking Tests

Purpose

The WLAN (wireless local area network) tests determined the expected throughput of the WLAN devices in each laptop and compared the laptops' signal strengths when they were side by side. Both laptops used the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard for wireless networking, often called Wi-Fi.

In communication networks, throughput is the amount of digital data per unit of time that is delivered or passed through a network node. For example, it may be the amount of data that is delivered to a network terminal or host computer, or between two computers. The throughput is usually measured in bits per second (bit/s or bps), occasionally in data packets per second, or data packets per timeslot.

Equipment

Ixia IxChariot software was used to measure the throughput of laptops on a WLAN network. IxChariot is the industry's leading test tool for simulating real-world device and system performance under realistic load conditions. Endpoints are configured and different scripts can be run to simulate typical usage while measuring throughput rates. For these WLAN tests, five different scripts were run to measure throughput:

Throughput script: Endpoint 1 sends a 100,000-byte file to endpoint 2. Endpoint 2 sends an acknowledgment after receiving the file. This process is repeated 100 times and the throughput is averaged.
HTTPtext script: This script emulates the transfer of text files from an HTTP server. A 1,000-byte file is sent from endpoint 1 to endpoint 2. Endpoint 2 sends an acknowledgment after receiving the file. This process is repeated throughout the test.
HTTPgif script: This script emulates the transfer of graphic files from an HTTP server. A 10,000-byte file is sent from endpoint 1 to endpoint 2. Endpoint 2 sends an acknowledgment after receiving the file. This process is repeated throughout the test.
FTPPut script: This script simulates sending a file from endpoint 1 to endpoint 2 using the TCP/IP FTP application. The file size is 100,000 bytes. The script has three sections, each with its own connection:
- The first section emulates a user logging on from endpoint 1 to endpoint 2.
- The second, timed section emulates endpoint 1's request for, and the transfer of, a 100,000-byte file.
- The third section emulates a user logging off.
FTPGet script: This script is identical to the FTPPut script except that it emulates receiving a file from an FTP server.

PassMark WirelessMon 2.0 software was used to monitor the Wi-Fi signal strength while driving around a Wi-Fi access point. The PassMark software logs the signal strength and uses the time stamps to compare the signal strength of two laptops.

Procedure

Throughput tests: Three laptops were used for the throughput tests, two XR-1 laptops and a CF-30 laptop. All three laptops were connected to a secure WLAN router. IxChariot software was loaded on one XR-1 laptop and configured as endpoint 1. The other XR-1 laptop and the CF-30 laptop were configured as endpoints 2 and 3. All three laptops were placed side by side at three different locations, simulating different signal strengths (90 percent, 50 percent, and 15 percent). The five scripts described above were run at each of the locations measuring throughput between endpoints 1 and 2, and between endpoints 1 and 3.

Wi-Fi signal strength tests: An XR-1 and a CF-30 laptop were placed side by side on a vehicle dashboard at an unsecured Wi-Fi access point. PassMark WirelessMon 2.0 software was run and configured to log the signal strength and time on both laptops. The vehicle was driven around the parking lot to obtain different signal strengths.

Results

Throughput tests: Figures J–1 through J–3 show the results of the IxChariot throughput tests.

Graph of the IxChariot Throughput Tests (WiFi 90 Percent Signal Strength). The CF-30 and XR-1 were tested under the FTPGet, FTPPut, HTTPGif, HTTPText, and Throughput.
Figure J–1—This graph shows the results from the IxChariot throughput
tests using the internal WLAN at 90-percent signal strength. The
five tests represent typical Internet usage in a field situation.

Graph of the IxChariot Throughput Tests (WiFi 6 Percent Signal Strength). The CF-30 and XR-1 were tested under the FTPGet, FTPPut, HTTPGif, HTTPText, and Throughput.
Figure J–2—This graph shows the results from the IxChariot
throughput tests using the internal WLAN at 50-percent signal
strength. The five tests represent typical Internet usage in a field situation.

Graph of the IxChariot Throughput Tests (WiFi 15 Percent Signal Strength). The CF-30 and XR-1 were tested under the FTPGet, FTPPut, HTTPGif, HTTPText, and Throughput.
Figure J–3—This graph shows the results from the IxChariot
throughput tests using the internal WLAN at 15-percent
signal strength. The five tests represent typical Internet
usage in a field situation.

Wi-Fi signal strength tests: Figures J–4 and J–5 show the results of the roaming Wi-Fi tests. Figure J–6 is an example of the output from PassMark WirelessMon 2.0 software showing signal strength.

Graph of the WLAN Signal Strength Tests of the CF-30 and XR-1.
Figure J–4—Results of the WLAN tests for the CF-30 and XR-1 laptops.
The results are displayed in signal strength.

Graph of the WLAN Tests-Signal Strength of the CF-30 and XR-1.
Figure J–5—Results of the WLAN tests for the CF-30 and XR-1 laptops.
The results are displayed in –dB levels.

Screen shot of what the output looks like from the PassMark WirelessMon 2.0 software. The output shows the signal strength and available WLAN access points.
Figure J–6—Typical output from the PassMark WirelessMon 2.0 software
showing signal strength and available WLAN access points.

Conclusions

There is very little difference between the internal WLAN (802.11) devices on the CF-30 and XR-1 laptops. The results were almost identical when the two devices were side by side in a vehicle. There was no practical difference between the two laptops when throughput was measured at three different signal strengths.