JPL's Wireless Communication Reference Website

Chapter: Analog and Digital Transmission. Section: Multi-Carrier Modulation

OFDM as a possible modulation technique for multimedia applications in the range of mm waves

Contributed by Dusan Matic

The 60 GHz band

The scarcity of spectrum and the new technical possibilities in recent years have drawn attention all over the world to the millimeter band. It has become a hot topic as a research area for broadband communications.

The low mm wave band from 20-60 GHz, which is nearly unused and allows for large bandwidth applications, combines the advantages of infrared (enough free bandwidth and UHF (good coverage). Use of the area around 60 GHz is encouraged for the following reasons.

A major drawback of this frequency region is the fact that the technology for the transceivers will be expensive in the early stages. If used indoor, the mm wave radio channel shows adverse frequency selective multipath characteristics due to the highly reflective indoor environment, which results in severe signal dispersion and limits the maximum usable symbol rate. It is worth mentioning that no definitive evidence of any hazards has been shown to date to the general public arising from the prolonged exposure in fields of less than 10 mW/cm2 in the mm waves.

There is a lot of fundamental investigation needed in this area, e.g. propagation modeling for 60 GHz, effects of antenna diversity, technology development, etc.

For the final choice between OFDM and single-carrier modulation, one needs knowing the channel properties at 60 GHz. Measurements and models can hardly be found in the literature. These properties have to be built in the simulation model, which could then be used for evaluating modulation technique candidates for the mobile multimedia communication.

JPL's Wireless Communication Reference Website Dusan Matic, 1999