US 5,471,463 AGranted

Radio communication systems

AssigneeRoke Manor Research Limited

InventorAnthony P. Hulbert

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Abstract

CDMA (Code Division Multiple Access) can be used in cellular mobile radio systems to provide good spectral efficiency through averaging the interference wherever the number of users per carrier is large (several tens). This is readily practicable for voice users whose data rate requirements are modest but requires large spreading factors for ISDN data service users. This invention proposes an approach in which a multiplicity of CDMA carriers each with relatively low bandwidth are used for the voice services and overlayed with wide bandwidth CDMA carriers whose bandwidth occupies the whole (or most) of the band occupied by all of the narrowband CDMA carriers in order to service the data users. This allows the same RF band to service a relatively small number of data service users with wideband (and therefore higher cost) terminals without affecting the cost of terminals for the majority of voice users.

Claims4

Dependent claims

A radio communication system comprising a base station which is arranged in communication with a plurality of mobile stations for the transmission of speech using a first set of channels and for the transmission of data using a second set of channels, the channels of the first set each having substantially the same bandwidth and comprising a plurality of groups of channels wherein each group of channels is arranged to operate using a different frequency, and wherein all channels within a group are arranged to operate on a same carrier frequency, and wherein the data and speech in the respective channels of each group are transmitted using CDMA (Code Division Multiple Access), each channel of a group being distinguished from every other channel of that group by a unique CDMA code, the channels of the second set being transmitted each on the same carrier frequency using CDMA for mutual discrimination, the frequency bandwidth used for the channels of the second set being arranged to correspond within the bandwidth occupied by at least some of the groups of the first set.

Dependencies are inferred from the claim text.