data radios show great potential for supporting current and future
Environmental and Biological Field Science.
2. In particular spread spectrum digital radios manufactured since
1990 - since FCC rules permitted their manufacture, sale, and use
- operating in the FCC Part 15 Bands, hold such potential that the
way is opened to revolutionary ways field data can be collected, transmitted,
acquired, and distributed world wide, not only to institutional research
scientists, but also to educational populations from grade school
through graduate school, and to any citizen in the world who has a
web browser and access to the Internet. Even low bandwidth access.
3. Several characteristics of both radios and attached devices - from
individual sensors and data loggers, computers, and networks - combine
to stimulate and reinforce this revolution.
a. Data loggers are now routinely and
very widely used to store locally connected data.
b. Increasingly the stored data is in
standard forms, which can be made interoperable.
c. The sensor industry has become quite
ubiquitous. They are capable of being integrated into data logger,
storage, or processing systems,
d. Low cost, processor driven, sensors
handle data in a wide range of forms - numeric, images, sounds, increasingly
stored as digital data.
e. Data radios can deliver data, error
free, over increasing distances, through hostile environments.
4. Current commercial satellite systems and services can readily be
interfaced, affordably, to digital wireless devices radiating out
from the base station, making data collection wirelessly possible
from virtually every place on earth, no matter how remote from urban
5. Defacto standardization which has spread since the Internet became
popular, - - RS232 serial, Ethernet, TCP-IP, 802.11b - makes it relatively
inexpensive and easy for technicians supporting science data networks
to assemble, interface, configure and deploy wireless data networks
from off-the shelf equipment, and connect up their data loggers and
sensors to data bases and to all researchers via the Internet.
6. Radios operating in the 902-928Mhz unlicensed range are superior
to radios using the 2.4ghz, or 5.8ghz frequencies for fetching field
data through vegetation and trees.
7. Current FCC power rules for the US (radios and their associated
amplifiers and antennas cannot exceed 36dBi), which do not differentiate
between Urban and Rural or Remote-area uses, do not adequately support
field science. While off the shelf data radios operating under current
FCC rules, can, using costly relay stations, be made to operate from
1 to 10 miles even through wooded areas, there is no reason from the
standpoint of 'interference' with other radios in remote areas where
very few, if any such radios are in use, why the FCC could not, or
should not, grant permanent increases in power (to at least 10watts
or 40dbi) for rural uses. While it is possible to seek waivers under
Part 5 FCC rules for 'Experimental Licenses' and there are costly
families of License-required radios, these should not be necessary.
8. Environmental and Biological Science Institutions/Universities
are almost oblivious to the role and importance of the FCC in enabling,
or inhibiting their uses of wireless for their field science. There
simply is very little 'wireless' expertise in these institutions.
Thus there is little knowledge of spectrum rules, how to find them
on the FCC web site, how to comment on FCC proposed rule changes,
or how, collectively influence FCC rulemaking, even though the process
is open and public and all involvement by universities or researchers
or their professional organizations can entirely be by email and web
access to FCC government nets.
9. Likewise American field science is not even on the radar screen
of the FCC as an important public constituency which should be served.
10. There is a need for universities which have substantial environmental
or biological science programs to add a wireless component to their
IT staffs. While individual Science Projects - such as the NSF funded
LTERs - or the work of the 150 Biological Science field stations can
recruit or subcontract with wireless experts to support a given project,
this is no long term solution for an institution. For deployed wireless
networks supporting long term ecological research projects will have
to be maintained, troubleshot, and/or modified long after temporary
wireless experts are gone. In four of the five LTERs worked with by
this NSF project, if the technicians who mastered this new field of
digital field wireless leave, there is little likelihood anyone will
replace them. Just as the use of personal computers, then modems,
then IP networks had to be learned over the last 20 years, both at
the individual user, and the institutional installer level, so will
wireless be gradually learned by all. But the art of making valid
technical site surveys, deploying wireless networks, troubleshooting
them, and interconnecting them over Internet works is not trivial.
At this time it is still specialized work. This is not to say that
technicians in the LTERs supported by this Wireless Project have not
learned a lot by observation and working besides this PI and colleagues,
but none of them are yet at the larger scale, institutional-level
of wireless technical expertise, management, or policy making.
11. Reliable delivery of power to radios in the field - through all
seasons - is the largest obstacle in the use of wireless devices.
A large proportion of data loggers are emplaced in valleys, woods,
and low land places - exactly the places which solar panels deliver
the least efficient power to storage batteries. In cold regions or
where winters are cold, it can cost more for solar or wind power generation
and battery storage, than complete radio systems. Much development
needs to be done to overcome this problem. Harvesting power from the
field, fuel cell technology are among the most promising technologies
which need to be explored.
12. Since wireless has proven its ability to serve Data Loggers, but
also since data logger systems can be costly - at least $3,000 per
site, and off the shelf radios with their associated power and battery
storage systems can add another $2,000, such $5,000 complete systems
do not 'scale' well. Repeatedly PI's wished that wireless could be
used to deploy many more systems to monitor the environment. The answer
lies in the development of totally new small radios, singular sensors,
rechargeable batteries, which can operate in a mesh network (fields
of sensors), and the decreased use of more costly data logger plus
radio installations (except for key location meteorological stations
with many sensors)
13. It is more costly in energy to 'communicate' than to 'process'
data collected. Paralleling the development and use of smaller, short
range, networking radios, is the need for development of very small
processors to connect individual sensors and the radios. So that data
collected can be processed and perhaps reduced to the least amount
of significant data, and only that small amount communicated wirelessly.
Conserving power over long periods. The typical combination used in
this project of off the shelf radios, standard large capacity data
loggers, and complete power systems - which can last at least 6 months
untended in severe climates - is not necessary, and from a dollar
cost standpoint, undesirable. Larger numbers of smaller data collectors
better serves field science while remaining the most cost effective.
14. There is an accelerating rate of change and development in wireless
data radios. Between the beginning of this project in 1999 and its
end three years later, there has been explosive development of new
radios, new amplifiers, new antennas, 'smart' radios, and more complex
signal processing methods. Costs have plummeted for some radios (802.11b)
are reasonable for some new ones (5.8ghz spread spectrum, UNII band
radios), but the industry is stagnant - in pricing and development
of radios operating in the best frequency ranges - 902-928mhz - for
field science. Again, this is because manufacturers do not see field
science as a market (even though one Data Logger company, Campbell
Scientific has a growing market and is profitable for its support
of field science.) The Environmental Science community is not defining
what it wants in wireless and communicating to manufacturers. Unfortunately
it is taking whatever industry gives it.
15. The vast majority of collected field environmental data collected
from sensors requires low data rates to communicate efficiently. It
is rare than wireless data speeds need to be over 9,600 baud. Even
though one of the best radios for data collection - the Freewave serial
port radio - can operate at 115kbps, none of those deployed by this
project had to operate above 9,600 baud. Thus the high bandwidth radios
- such as 802.11b 11mbps (half duplex) devices - have limited utility
for field data collection. And such radios, which operate at 2.4ghz
or 5.8ghz cannot penetrate vegetation nearly as well as slower data
rate, frequency hopping 902-928Mhz radios. The only exception to this
finding, is in the case of deploying video cameras for continuous
broadcast over wireless nets in some field science locations. Then
higher data rate radios are useful.
16. The most important task which has to be performed before a wireless
network supporting field research is designed and deployed, is the
technical Site Survey, in which either Spectrum Analyzers are used
to determine link requirements and robustness of signal, or actual
radios are used, with a variety of antennas. This aspect is the least
appreciated or practiced except by professional installers. With experience
technical staffs can make installations without owning or using costly
spectrum analyzers. But a sound site survey is vital in all cases.
Especially this is true if a network is to be set up, which might
be later expanded. The basic layout has to be right, to permit such
expansion without unnecessary reconfiguration of existing radios,
antennas, or their mountings.
TECHNICAL PROJECT FINDINGS
1. The serial
port, Freewave DRG series of radios operating at 902-928Mhz and using
unlicensed spread spectrum Frequency Hopping protocols remain the
best radios for establishing wireless links to and from data loggers
in the field. In particular to and from the Campbell Scientific CRX
series - which are the most favored data loggers by environmental
scientists. These radios have the best receiver sensitivity, configurability,
robustness, range, reliability, and tree and vegetation penetrating
capability of any 915mhz radios tested.
2. 2.4 or 5.8ghz radios, from 100mw 11mbps 802.11b, either end user
or access point radios from a wide variety of vendors, and at very
low cost (under $100 for individual radio, or $150 for multi-user
access points) are the least useful in gathering field data from data
3. 802.11b 11mb radios do have a useful role connecting up video or
sound capture systems short ranges with clear line of sight, to long-haul
radios or networks. Their interoperability and point to multi-point
abilities permit them to be used in heterogeneous networks. They can
be used the 'last half mile' by researchers carrying laptop computers
to connect to the Internet, provided there is a long haul connection,
wireless or wired, from the nearest access points.
4. 5.8ghz spread spectrum or UNII band radios, operating from 11mbps
to 100mbps are primarily useful for back haul from field sites, tower
or high point to highpoint, in the support of field research.
5. The severe power limitations put on unlicensed data radios by the
FCC, even in the most remote field locations where 'interference'
as experienced in urban or building complex setting is virtually nonexistent,
severely cripples the ability of Environmental and Biological Research
Scientist to do their field work supported by wireless networks they
can set up.
6. The latency - from 500ms upwards of bi-directional satellite Internet
services, and the power requirements of field ground stations - limits
their utility to be used as a remote-area 'base station' for radiating
out to the range limits of other wireless devices. This is particularly
true for efforts to communicate over the Internet directly to the
Campbell Data loggers - since the program time-out code in the Data
loggers do not take into account long latency of connection to PC208W
software running on remote PCs. This can be handled in the case of
custom programs other than PC208W software designed to fetch data
from the data loggers and store it in data bases.
7. Campbell Scientific has brought out their own unlicensed radios
configured to best interface with their data loggers - such as interfacing
with the modified Serial protocols called CSIO, and power - from the
data logger. However these radios are modeled after 2.4ghz radios,
have very low power (100mw or less) and because of the combination
of their frequency and power must be used in pure 'line of sight'
configurations. Which is rare in field deployment of most data loggers.
8. In spite of the explosion of sale and use of 'Wi-fi' (802.11b)
radios which operate in the 2.4-2.483ghz bands in the general economy
(reported as more than 1.5 million now sold a month) with corresponding
lowering of price through competition to below $100 a radio there
has not been a corresponding increase in the manufacture or sales
of radios which operate in the 902-928Mhz range, even though such
radios are far and away the best suited for field science data networks.
Accordingly 903-915Mhz radios still cost in the $1,000 or higher range.
Thus there is a problem of 'scale' in the use of these costlier radios
for field science.
9. In most cases - the off-the-shelf radios, either 915Mhz or 2.4Ghz
types, are 'overkill' for most field science needs. They consume too
much power, are capable of data rates higher than needed, have too
many features, and cost too much. For such real world needs as linking
44 light sensors, costing $20 each, 150 meters to a data logger or
back haul point, as one Puerto Rican research project needs, deploying
all that is required to power and maintain $1,000 radios is not sensible.
There is a great need for smaller, cheaper - in the $100 range complete
with processor and power supply - shorter range radios that can link
individual or a small group of sensors to the net, using 'mesh' networking
techniques. It is hoped that later NSF funded Wireless Projects will
research and prototype such useful digital radios.
10. Because of power requirements to keep field radios 'always on,'
a technical strategy of either having a device, such as the programmable
data logger to which it is attached, turn on and turn off the radio
periodically to conserve power - or the addition of substantial, with
ample margin, solar panels and 12 volt Marine quality gel cell batteries
11. The most useful radios for field science work can operate on 12volts,
DC, because that is the most readily available in portable, battery
with long amp hour storage form. And such radios can be powered from
cigarette lighters in vehicles - which are needed in particular during
'site surveys' prior to selecting the places and configurations of