JPL's Wireless Communication Reference Website

Chapter: Network Concepts and Standards

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 applications.

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 cellular telephone band, and the suitability of low-cost silicon VLSI chip implementations for this band allow the design of products with mass-produced components.

Applications

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.

Electromagnetic Compatibility

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 radiators).
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.

Defacto Standards

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.

European Situation

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.



JPL's Wireless Communication Reference Website 1993, 1995.

Source Credit:
This page includes extended quotes from the presentation by David Bantz of IBM Watson Research Center, entitled "The 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.