Broadcasting

As the number of tablets and smart phones grows, telecom operators vie for access to new frequency bands, but the traditional methods of adjudicating the spectrum are facing limitations.

Keep in mind that the spectrum is used for radio and television broadcasts, for satellite communications, for airplane traffic control, for geolocation (Global Positioning Systems – GPS), as well as for military, police and other governmental purposes. Traditionally, the demand for additional spectrum has been met due to the advances in electronics that have permitted the use of higher frequencies at an affordable cost. Higher frequencies are well suited for high speed transmissions, but they have a limited range and are highly attenuated by walls and other obstacles as well as by rain.

This is exemplified by comparing the coverage of an AM radio broadcasting station to that of an FM station: the great range of the AM station is due to its use of lower frequencies. On the other hand, FM stations can make use of higher bandwidths and as consequence can offer greater audio quality at the expense of a more limited range.

Accordingly, TV broadcasting frequencies are coveted by cellular telephone providers: using lower frequencies means they will need fewer base stations, with corresponding savings in deployment, operation and maintenance. This is why these frequencies are commonly referred as “beach front property”.

The greatest impact of advanced modulation and coding methods for more efficient spectrum use has been the availability of more bits/s per Hz of bandwidth. This advance was made economically possible by great strides in integrated circuit manufacture.

According to calculations performed in 1948 by Claude Shannon, the father of modern telecommunications, a typical telephone line can, in theory, carry up 30 Kbit/s. But this rate was achieved only in the 1990s with the invention of integrated circuits that could implement the required techniques.

Connexion