Industrial Scientific and
Medical (ISM) Bands
In 1985, the Federal Communications Commission issued rules
permitting "intentional radiators" to use of the "Industrial Scientific and
Medical" (ISM) bands (902-928, 2400-2483.5, 5725-5850 MHz) at power levels up
to one Watt without end-user licenses. Originally these bands had been
reserved for unwanted, but unavoidable emissions from industrial and other
processes, but they also supported a few (often military) communication users.
The new rules led to the development of a large number of consumer and
professional products and is considered to be
an important step towards the development of wireless computing or multimedia
With many technical problems at transmission and protocol level still
unresolved, the availability of ISM bands for communication applications has
provided valuable insight into the needs of end users, especially at the lower
end of the acceptable cost curve. Personal mobility with infrastructure access
seems to be emerging as a common theme. This is illustrated by wireless
headphones, controllers and speakers in the home. Of course, cordless
telephones are a prime example, but the new FCC rules permit building them
with enhanced security, digital transmission, and much longer range. In the
middle of the cost curve, we find the wireless PBX, again an example of access
to an infrastructure. And in systems where performance is a primary
consideration, the wireless LAN is an example of an application with both
intra-system and infrastructure access.
The ability to conceive radio-based communications systems is no longer
constrained mainly by technology, but by our understanding of the needs of
users. This understanding is still very imperfect and incomplete. This
effectively precludes our ability to execute a formal, thorough design
process, and may also bear on our ability to formulate valid standards. The
exciting, disorderly, energetic exploitation of the FCC part 15 rules for the
ISM bands contributes to a growth of understanding, and to our future ability
to offer more cooperative communications systems with the necessary
capabilities. This approach is typical for the US-dominated computer
industry, and differs radically from the orderly top-down policy approach in
the European evolution.
The interest in using these bands has been stimulated by several factors that
differ substantially for the European approach of conscientious, but time-
consuming standardization. Most importantly, there is almost a complete
absence of user restrictions - no registration procedure, no qualification of
end users, no restrictions as to where the products can be used. The absence
of license fees also contributes to the economic attractiveness of products.
The proximity of the 902-928 MHz ISM band to the US 800 MHz AMPS
telephone band, and the suitability of low-cost silicon VLSI chip
implementations for this band allow the design of products with mass-produced
The enthusiastic American pursuit of product and market opportunities offered
by the ISM rules is partly caused by this advent of a means by which users
can build low-cost mobile data systems. Applications include wireless
LANs, short range links for Advanced Traveller Information and Management
Systems (e.g. electronic toll collection), garage door openers, home audio
distribution, cordless phones, private point-to-point links, remote control,
wireless telemetric systems (e.g. electrical power consumption metering). A
promising future application appears to be wireless access to the Internet or
other multi-media computer networks.
A drawback of the ISM band is the lack of any protection against interference.
In particular, micr wave ovens limit the useful range of such communication
devices. To ensure some coexistence between new communication users and users
already occupying the band, spread-spectrum transmission is mandatory, except
for extremely low power applications. Spread spectrum offers some protection
both for the licensed narrowband users of the bands (since the average
spectral power density of the new users is low in their existing channels)
and also protect new users (since the processing gain of spread-spectrum
systems mitigate interference from existing intentional and non-intentional
Some critics argue that technically it is a harder problem to
protect a wanted signal from only a few interferers than to separate it from
many weak interferers. Direct Sequence Spread spectrum transmission typically spreads all
signals over the entire ISM band, so it also makes it likely that more users
interfere than in narrowband scenarios. Frequency Hopping appears an interesting solution.
The present use of the ISM band is characterized by proprietary systems.
Associated with this are
One interpretation of the industrial interest in these bands, voiced
both by established computer manufacturers and by small new companies is that
the ISM rules have permitted rapacious entrepreneurs to exploit a short-term
opportunity, without any thought to the longer-term implications when these
bands will become intolerably crowded and unusable. Another view is that the
rules are a useful experiment in spectrum allocation: a recognition of the
incredible waste of our spectral resource due to exclusive licensing, and an
attempt to improve this situation through demand-assignment. Another,
somewhat less radical approach to this problem is being pursued in the
technical development of the dynamically-assigned spectrum "etiquette" now
pursued for the newly-allocated bands for unlicensed PCS in the US.
- little standards activity, except for the wireless-LAN standardization work in the European Telecommunications Standardization Institute (ETSI) and IEEE 802.11.
- little or no emphasis on interoperability
- great diversity in products, and in the traffic they generate
- interference-limited (as opposed to noise-limited) system design
- little focus on coexistence
In Europe ISM-type regulations exist in similar bands, except that the
900 MHz frequencies are part of the GSM allocation.
This implies that 900 MHz ISM equipment (illegally) imported from the U.S., Asia
or South Africa cause and suffers substantial interference.
CEPT recommendation TR/01-04 allows low powered
(ERP < 10 mW)
devices to operate in the 433.05 - 434.79 MHz band. Manufacturors are free to
select their own modulation method, carrier frequency and transmit bandwidth.
Type approval using ETSI norm ETS 300 220 is required.
This page includes extended quotes from the presentation by David Bantz of IBM Watson
Research Center, entitled
Use of the Industrial-Scientific-Medical Bands for Wireless Communication: An
IBM Perspective", Proc. ICCC Symposium on Wireless Computer Networks, The
Hague, Sep. 19-23, 1994.