DIARY # 13

Wireless and the Big Buoy

The Trout Lake LTER was able, through a supplemental grant last year, to acquire and ready an advanced technology RUSS Buoy (Remote Underwater Sampling Station) made by the Apprise Technologies. The project involving the launching and use of RUSS at, and on, Trout Lake, called by the staff the "Big Buoy," is a Paul Hanson project.

From Apprise Technologies, an advertising schematic of the whole system, with anchoring system.

As delivered from the company, the RUSS Buoy has an integrated cell phone, data collection system. This of course limits the use of its data communications to (1) water bodies where cell phones can reach and (2) about 9,600 baud of bandwidth over the cell phone modem.

Paul Hanson, working from the Madison Campus, acquired an Aironet BR100 Access Point spread spectrum, no-licence (Part 15 FCC Rules) data Radio and a Aironet PCMIA Card radio, both capable of 10mbps. Then he and a team of undergraduates fabricated and programmed what he called a 'Microcontroller' which is capable of accepting the PCMIA card Aironet Radio, and then interfacing with the data collection system of the Big Buoy, and can be installed on the Buoy, and can operate independently of the cell phone system. They then use a short (12 inches or so) 2.4Ghz omni antenna, perhaps 4db gain, on the Buoy. In the following picture, the microcontroller, before being put in a cavity below the solar panels, is in the small white box on the right, and the antenna is hanging down in the center of the picture.

Back at the Trout Lake Station the Aironet Access Point is in a room next to a Linux system computer, and the wall Ethernet ports, which gives access to the University Internet service. Up on the roof is a larger omni antenna, with 6db of gain, and being on the north end of the building, with a quite open, line of sight view of Trout Lake. It is the smaller vertical antenna in the following view.

Here is the Big Buoy just before launching on July 6th, showing the main float, moved out onto the water, and the cylinders which are suspended beneath the float, with sophisticated depth-control mechanisms, using compressed air. So that the cylinders can remain at exact depths while the sensors do their data collecting work, even while the float bobs around. And the depth can be varied remotely, by wireless commands. The cylinder can descend to 300 feet.

 

 

 

It took two boats, and at least 6 men to manhandle and ready the electronics, connectors, batteries, solar panels, floats, anchors, globular floats, cylinders, cables to launch.

And here is the entire rig being towed about a half mile out on the lake over a 'big hole' in the lake bottom.

Data Flow Data Bases from Big Buoy

Two student programmers, Ryan Ludwig and Nick Offerman, paid half by Paul Hanson's portion of the LTER budget, and half by our project, are in the midst of creating a data-flow, database, web presentation of the data from over 12 separate sensors carried on the Big Buoy.

The programming concept, is for Nick Offerman to create, under Linux, a Relational Data base for the periodic fetching, wirelessly, at fast Aironet speed, and permanent storage of the Data which is being collected constantly and stored in the 'Profiler' data logger on the Big Buoy.

The Data Base then resides anywhere on the Internet, in this case at Trout Lake Station in a dedicated computer system. Both the Aironet 10mbps Access Point, and the Linux Data base system, as well as the Microcontroller on the Big Buoy are linked by 10baseT Ethernet, and all have IP numbers in them.

Then Ryan Ludwig is programming an HTML Web Interface, where outsiders can see the data via a web browser over the Internet. So the connection and data flow between the Profiler on the Big Buoy, and the Data Base is isolated from outside access, while the Web is the only interface to remote researchers.

The priority of work for the two programmers is to first handle the data coming from the sensors on the Big Buoy, then to adapt it to the Sparkling Lake Raft data collection system. Then finally to adapt it to the multiple 'small buoys' data collection. In other words, to store the data being collected from the Trout Lake LTER data loggers, in a relational data base, and push it into a Web Paged system, where the data can be made available to all researchers, over the Internet.

One advantage of the Aironet 10mbps Radios for this use is that they support 10baseT ethernet connections, protocols, and speed. If a low speed serial radio were being used, such as the Freewaves, there would have to be ethernet to serial interfaces employed.

Need for Speed?

In meetings held during my trip I raised the issue of the need for the Aironet Radios to communicate between the Big Buoy and the Trout Lake Center. My concerns were that

(1) Aironet Class Radios - 10mbps, at 2.4-2.4835Ghz frequencies, and the normal 100 milliwatt power - are considerably more costly than serial speed (9.6 to 115Kbps) radios. Aironet BR500s, which can act as point to multi-point (up to 1000+) Access Point, Relay, or client end radios list at $2,400 each. 4 client (controlled by controlling the number of Ethernet Mac Addresses possible) Aironets are in the $1,500 range. Single client radios can cost up to $1,000. And even the PCMIA card Aironets cost over $200 each, and must be supplemented by either dedicating a PC to the remote task, or, as was done in this case, building a Microcontroller device into which the PCMIA card can fit, and then the requirement to purchase a 'pigtail' connector cable which can connect the PCMIA card to an external antenna, with its required cables. So the question arises whether using such advanced, fast, radios at corresponding costs can 'scale' when a Biological Science are has scores of data logging points.

(2) Radios which operate at only 100 Mwatts of power, in the 2.4Ghz frequency range are severely limited in how much vegetation they can punch through, in comparison with 915Mhz radios (the lower the frequency the more penetration), operating at 1 full watt - the maximum authorized by the FCC - of power. This can be offset somewhat by buying an Amplifier that can bring an Aironet from 100 milliwatts to one half, or even 1 full watt of power, But at a price - from $750 to $1,000 more for the radio plus amplifier. And still, the penetration will not match that of the 915Mhz radios in forested country.

(3) Even though the Apprise Technologies RUSS system, at over $80,000 in cost is capable of supporting a large number of underwater sensory devices, the total data flow rarely exceeds the need for over 9,600 baud of bandwidth. So, for accessing the Big Buoy in its design mode, the faster radios are not needed.

On the other hand, if there is, or will be, a requirement for higher bandwidth devices, such as video cameras on the float, which demand much more bandwidth than serial radios can usually deliver, then the faster radios may be needed, and are justified. More on that later in this Trip Report.

 

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