WiFi "ui-rise" Network Specs.
Network Info:
- AP: Linksys WRT-54G(S)
- SSID: ui-rise
- Encryption: None
- Mode: WDS Connected Access Points
- Rate: 54mbps
- Routers: 3
- IP's:
- 192.168.2.10-19 (RED)
- 192.168.2.20-29 (YELLOW)
- 192.168.2.30-39 (GREEN)
- MAC's (for WDS):
- RED: …
- YELLOW: …
- GREEN: …
Permanent Clients/Services:
- RED (192.168.2.1)
- GPSd - Port 2947
- DHCP - Automatic
- NTP - Automatic
- YELLOW (192.168.2.2)
- DHCP - Automatic
- GPSd - Port 2947
- NTP - Automatic
- GREEN (192.168.2.3)
- DHCP - Automatic
- GPSd - Port 2947
- NTP - Automatic
What is Each Service?
- GPSd RED, YELLOW, GREEN
- This is the application run on each router to distribute GPS data from the internal or external GPS units.
- DHCP RED, YELLOW, GREEN
- This is the Dynamic Host Configuration Protocol server that runs on each router. This allows each router to assign a unique IP address to wireless and ethernet connected clients.
- NTP RED, YELLOW, GREEN
- This is the Network Time Protocol server that runs on each router. We set the time on each router based on received GPS time data, and have configured the network to respond to (nearly) all time requests with the host router's own NTP server - even if a client wanted a different time server. We get the time data from the GPS two different ways…we run a script after a GPS lock is achieved to set the system clock, and then we run NTPd to compare the stability of the system clock to the GPS time and make modifications as needed every 16 seconds. This way accurate time can be provided to clients requesting it.
Benchmarks (via Test.html on RED):
- 0 Node Hop Results (direct connection)
- Throughput - 1200 KB/sec
- Latency - 1ms
- Packet Loss - ~0%
- 1 Node Hop Results
- Throughput - 150 KB/sec
- Latency - Not Measured
- Packet Loss - Not Measured
- 2 Node Hop Results
- Throughput - Not Measured
- Latency - Not Measured
- Packet Loss - Not Measured
Network Comments:
The router takes up to 30 seconds to boot, and can take up to 5 minutes to get a GPS lock and synchronize accurate time data. We would like better boot-times, but it likely isn't possible. Decreasing the amount of time needed to get a GPS lock is useful in case the router is soft-reset - which also power-cycles the GPS. We want to add a battery backup to the GPS to keep it 'on' during soft-resets to eliminate the GPS lock time. Once we do that we want to measure the time needed from a soft-reset until GPSd starts providing good GPS data to see the amount of improvement.
