January 11, 2006

SDSU's Santa Margarita Ecological Reserve backbone receives substantial facelift

The San Diego State University Biological Field Station Programs' Santa Margarita Ecological Reserve connected to HPWREN in 2001 at 45 megabits per second performance, and immediately began augmenting the interconnection with a reserve-wide wireless data infrastructure. The Intra-SMER network utilized Lucent 802.11b Ethernet radios, based on prior use of the same technology by HPWREN for access links to its backbone network. At that time SMER had been using dial-up phone modems and a Starband satellite ISP access for web and email use. The peak performance with this equipment was 28kbps and 150kbps, respectively, and the 1-3 Mbps that the then new Lucent radios provided made a substantial difference.

Over the years, due to the increased density of sensors on the reserve, including 13 network cameras, 3 hydro stations, 23 weather stations, an eddy co-variance tower, and coupled with a much larger human demand as the SMER staff and visitors needs grew, the Lucent gear was not able to handle our increasing networking needs. This resulted in a need for upgrading the network backbone, which was completed towards the end of 2005.

SMER currently supports thirteen nodes on the Intra-SMER network (seven of which are solar powered, and six are line powered) but the portion of the network that was being taxed the heaviest was the segment considered as the local backbone, i.e., the nodes, called TeleCommunications Sites, that create the link from the SMER North Station (and its HPWREN connection), via multiple hops to the South Station offices, which is at an over three miles distance at the other end of the reserve.

SMER North Station
The high-speed Intra-SMER backbone originates at the North Station, alongside various slower-speed 2.4GHz equipment, as well as sensors and cameras

The backbone consists of three hops across four nodes, with the two in the middle (TCS3 and TCS4) being solar powered. Repeated tests of the backbone throughput using iperf from either end of this segment showed that we typically operated at only about 900kbps. We chose the Trango 5.3-5.8GHz Atlas 45Mbps-class Ethernet radios for the upgrade, based on prior experience via collaborative activities on HPWREN where such radios had been used already. Some of the key benefits of the Trango radios: they consume less than 15 Watt, have a wide input voltage range of 10.5-24VDC, a compact design with an integrated antenna, and are in an affordable price range. However, this still required an upgrade of the solar power systems at TCS3 and TCS4 by adding another 100Ah battery and two additional 80 Watt solar panels each. The systems now have six solar panels and a 500Ah battery bank. The original design of the solar power system for the Lucent nodes was done by HPWREN and had the capacity to power two bridges with four radios cards and power injectors for an about 30 Watt total. One of the Lucent bridges and two of the Lucent radios were kept at TCS3 and TCS4 for use on other links, and as wireless access points. After the upgrade was completed, the network segment was again with a resulting throughput of about 10Mbps.

The TCS3 SMER TeleCommunications Site now has increased solar power and battery capacity, and supports two SMER high-performance backbone links, and well as slower-speed links, sensors, and a digital camera

These enhancements to the SMER infrastructure will allow for further growth of research projects throughout the about 4500 acre ecological reserve.

Pablo Bryant
Research Technology
San Diego State University Field Station Programs

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