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Wild about Wireless at the VCR/LTER

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Issue: 
Fall 2002

- Tom Williams, Old Colorado City Communications

- John Porter and Phil Smith, Virginia Coast Reserve (VCR)

Introduction

Among the technologies with the biggest potential to change the way we do business as ecologists are the new advances in wireless communications. Although ecologists have been using licensed VHF radios for data transfer for decades, the lower costs, higher speeds and easier use of spread spectrum technologies has opened the door for whole new classes of uses. With LAN-level speed, data flows can go beyond numbers to include images and sound, or arrays of sensors that have extraordinarily high data rates. We are on the cusp of advances that will allow us to deploy arrays of low-cost, lightweight wireless sensors for monitoring micro- as well as macro sites. However, our focus here is on the task of providing low-cost wireless connections to our remote field site.

Our goals for the VCR/LTER wireless project were ambitious and threefold:

  1. To allow transmission of meteorological and other digital data sources from our island study sites back to our researchers
  2. To provide access to real-time weather radar and other web-based information sources for researchers and technicians in our study areas
  3. To support video-teleconferencing for use with classes and real-time interactions between researchers, students and technicians located at both island and mainland locations

We were extremely fortunate in three respects. First and foremost, we received huge amounts of help (and even equipment) from Dave Hughes and Tom Williams of the NSF-funded Biological Sciences by Wireless Project (http://wireless.oldcolo.com/ ; note: this site has a wealth of practical information on wireless). Second, our site is well-suited to line-of-sight communications – with little topography or tall vegetation to block radio signals. Finally, we had access to lookout towers located at both ends of Hog Island (a principal VCR/LTER research site). With the help of Dave and (especially) Tom, we were able to achieve all our goals, with development of an 11MBS wireless LAN on Hog Island, linked to the mainland at E1 (2 MBS) speeds. So far, this has allowed us to deploy WWWcams to monitor research sites (http://www.VCRLTER.virginia.edu/wwwcam), receive real-time meteorological data, conduct prototype videoconferencing sessions from the island and to establish working LAN connections on our boats.

As part of their project, Tom Williams made diary entries tracking the progress of the system development. Here are some excerpts (the full diary with technical details and photos is available at: http://wireless.oldcolo.com/biology/OysterMenu.htm). Editors comments will be in []s:

Diary #38 [The first step was to prove the feasibility of a wireless link to the island using a 0.115 MBS serial Freewave radio]

During the previous week they [the VCR/LTER Staff] had purchased equipment, ladders, safety gear, tomato stakes, and everything else they could think of for work on an 80-foot tall unused fire Tower on Hog Island, where we hope to create a radio relay/hub….. The link we attempted is some 14 miles, mostly over Hog Island Bay. At that distance there is no guarantee of success, especially with the unknowns of reflection and absorption presented by saltwater, sandbars, and a small stand of trees…..The LTER staff didn't like the idea of this writer [Tom Williams] climbing a rusty old fire tower, so I stayed at the farmhouse and operated a radio with laptop and a 9 dB Yagi antenna, pointed towards the tower. Due to the steep pitch of the roof we also decided to make the first test from the lower-but-flatter porch roof/balcony (some 20 feet shy of the farmhouse's pinnacle). We kept an extension ladder handy in case we could not get a connection at that height…..While we wanted to use a Yagi -- directional antenna -- at the farmhouse, the preference for Broadwater Tower was/is to use an omnidirectional antenna, make the tower accessible from anywhere on the island as needed to extend the link. Phil Smith thus took both a 9 dB Yagi and a 6 dB omni to the top of the tower, as well as a radio, battery, and loopback plug…. Around 5 PM,during final preparation to start the test, we noticed that the farmhouse radio already had its green light on, indicating more-or-less workable connection -- and that with the Yagi lying on the porch roof/balcony floor. It was intermittent, but it was green. A more deliberate aiming of the farmhouse Yagi yielded a solid connection to the omnidirectional antenna on Broadwater Tower…. We thus determined that we could easily establish a reliable fourteen mile link between the VCR/LTER headquarters and Broadwater Tower, using one watt, 900 MHz, 115,000 bit per second serial-port-only FreeWave radios and a 9 dBi Yagi antenna at the farmhouse and either another Yagi or a 6 dBi omni on Broadwater Tower.

Diary #39 [The next step was to try some radios that support full networking (e.g., IP, LAN) as compared to a serial link]

On November 20 we tested two IP-ready radios -- the NovaRoam 900 and the WiLan Hopper Plus model 22-09…..We tested both radios over the 14 mile distance between the VCR/LTER headquarters in the 'Farmhouse', across Hog Island Bay to the Broadwater Tower, using the same antennas as we had previously used to test FreeWave radios (see Diary 38): 9 dBi Yagi antennas at both sites, plus a 6dBi omnidirectional antenna on Broadwater Tower…..The Wi-Lan radios failed to link up, even Yagi-to-Yagi. The only encouraging indication was with the unit on Broadwater Tower, on which a lone orange light showed that the tower radio was receiving data from its partner. No such result at the LTER headquarters, however. The 500 mW radios could not both span the distance….The NovaRoam radios did link up, when set for lower speed of 159kbps, the recommended setting for over 10 miles. Although the Yagi-to-omni link would not work, Yagi-to-Yagi did -- particularly when the antennas were horizontally polarized….. Even though the NovaRoam radios passed the test that the WiLan units failed, we decided to give the WiLan radios a second chance due to the desire higher bandwidth that would be needed if we were to run any live video applications. This decision was reinforced by telephone consultation with John Kinghorn of Wi-Lan's Technical Support department, who informed us that (1) the orange light at Broadwater Tower indicated that a link had been half-established, and (2) a higher-gain Yagi antenna would likely solve the problem. We were, in short, very close to a robust link…..On December 7, Tom Williams went back to Oyster, and everyone performed another test of the WiLan radios, this time using 13 dBi Yagi antennas made by Cushcraft. As we had hoped, the extra 4 dB gain at each end paid off nicely with a solid link between the farmhouse (headquarters) and Broadwater Tower.

Diary #45 [Our link to the mainland proven feasible, the next step was to install and tune it and start working on establishing 802.11b (Wi-FI) links within the island]

On April 2, 2002, we installed two radios at Broadwater Tower; first the Wi-Lan 900 MHz backhaul, and then the first of Hog Island's two Zcomax 802.11b access points….

The 900 MHz Wi-Lan backhaul was set up using 13 dBi directional (Yagi) antennas detailed in Diary 39. The connection is robust, at least in terms of signal strength. So far there have been no reports of downtime due to signal interference by weather. However wind, which is fairly constant at the top of Broadwater Tower, caused the Yagi to oscillate like an accordion reed, bouncing up and down about 6 times per second….

We not-too-coincidentally experienced about 20% dropped packets. The antenna oscillation was stopped by running thin rope from the antenna diagonally to the railing, thus dampening the vibration and solving the dropped packet problem……Having gotten both the backhaul and the initial 802.11b connection to work, we sent out a celebratory e-mail to other participants and returned to the boat. Unfortunately, the tide had gone out and we were stranded a few hundred feet off Hog Island for an additional three hours. To help redeem the time, we used a laptop computer to watch (and listen in stereo to) streaming video of a rock concert by the alternative group Indigenous, which was streamed via RealPlayer at a sustained data rate of 300 kilobits per second.

Diary #46 [Linking to the tower on the north end of Hog Island]

On April 4, 2002 we began the extension the network to Machipongo Station at the north end of Hog Island using 802.11b radios for both cloud and uplink….. Since it was going to be an unamplified link, we used a 24 dBi Radiall/Larsen 0.6 meter solid dish to make the 9 kilometer link back to Broadwater Tower….. In retrospect, we could probably have used a less expensive (and less expansive) antenna for the uplink to Broadwater Tower; tests showed that you could make the link acceptably using a 14 dBi panel antenna costing $60 (versus almost $400 for the 0.6 meter dish).

Diary #47 [Getting LTER boats on the Internet]

On August 9 we set up one of the LTER's boats for mobile high-speed Internet access. Anticipated uses include: Instantaneous tide information, Weather reports, correspondence/reporting back to the lab, Videoconferencing with the lab or with others; and Entertainment while stuck at low tide (see Diary 45)…. The next day we performed a range survey from the boat. When one does this from a car, driving around town looking for unsecured 802.11b access points and logging their locations and signal strengths, it is called "War Driving." Indeed, we used classic war driving tool for this survey: a program called Net Stumbler which, in addition to recording signal strength, noise level, access point name, and just about every other datum that is broadcast by an access point, also has the very nice feature of working with a GPS unit. As a result, once we had the GPS unit connected and the laptop appropriately aware of its location (serial port 1, 9600 bits per second, and so on) all we had to do was drive around the island…. As a result, we gathered some 50,000 data points.…. Machipongo Station's signal is visible from nearly everywhere, while the signal from Broadwater Tower is sporadic and often quite weak. The conclusion we drew is that for this application the stronger Orinoco Access Point is a significantly better bet.

Diary #48 [Linking to Meteorological Station]

We decided to connect a meteorological ("met") site near Machipongo Station at the north end of Hog Island. Since Hog Island has an 802.11b network, we sought an alternative to the Campbell NL-100, the Ethernet-to-CSIO converter which we had used for bridging between the Internet and the wireless networks in Alaska and Wisconsin…. Our aim this time was to convert a CSIO (serial) connection directly to 802.11b radio at the met station… Most "solutions" to serial-over-802.11b are kludges, consisting of a single port terminal server (which converts serial to Ethernet) connected to a separate Ethernet-to-802.11b converter, selling for the combined cost of the two modules plus an extra 50% for the "added value." Orinoco, on the other hand, offered a single unit (the EC-S that combines both functions, and at a significantly lower cost than the competition. The EC-S has a DCE serial connection, meaning it is designed to connect to a PC or laptop (or other DTE equipment) using a straight-through DB9 serial cable….. We connected the EC-S to a Campbell data logger via Campbell's SC929 cable, which is designed to provide a direct connection between a laptop or other PC and a Campbell CSIO port…. the installation was successful. From anywhere on the Internet, it was now possible to access the Machipongo meteorological station.