Northern Telecom Limited

Bce Telecom International, Inc.

Bell Canada International Inc.

Sorin Cohn-Sfetcu

Mahshad Koohgoli

John D Lockton

David G Agnew

Daniel J Doyle

Jackylene K Hood

The call set-up technique of this invention is characterized by the use of channel information from both base station and subscriber terminal in determining the radio traffic channel upon which to set-up a new call. Communication between the base station and subscriber terminal is carried out on a signalling channel until the traffic channel is chosen. Calls are set-up so that they proceed on the radio channel which, of a set of channels under consideration by the subscriber terminal, contains the least amount of interference as measured at the subscriber terminal. The set of channels under consideration by the subscriber terminal is a subset of the entire set of channels allocated to the service. This subset is comprised of those channels having little interference, as measured by the base station, and which, additionally, are not reserved exclusively for stationary, fixed-allocation services in the geographic location of the base station. The call set-up technique thereby assures that calls proceed on channels containing little interference from the viewpoints of both base station and subscriber terminal. The technique also facilitates sharing of the radio spectrum with stationary, fixed-allocation services because there is no need to program each subscriber terminal to avoid the spectrum allocated to the fixed service.

Call set-up and spectrum sharing in radio communication on systems with

The call set-up technique of this invention is characterized by the use of channel information from both base station and subscriber terminal in determining the radio traffic channel upon which to set-up a new call. Communication between the base station and subscriber terminal is carried out on a signalling channel until the traffic channel is chosen. Calls are set-up so that they proceed on the radio channel which, of a set of channels under consideration by the subscriber terminal, contains the least amount of interference as measured at the subscriber terminal. The set of channels under consideration by the subscriber terminal is a subset of the entire set of channels allocated to the service. This subset is made up of those channels having little interference, as measured by the base station, and which, additionally, are not reserved exclusively for stationary, fixed-allocation services in the geographic location of the base station. The call set-up technique thereby assures that calls proceed on channels containing little interference from the viewpoints of both base station and subscriber terminal. The technique also facilitates sharing of the radio spectrum with stationary, fixed-allocation services because there is no need to program each subscriber terminal to avoid the spectrum allocated to the fixed service.

A tone detector in the form of a digital correlator is disclosed in which PCM signal samples are delayed in a RAM for the correlation period. Using PROMs, the products of the current and delayed samples with samples of a sine signal at the frequency to be detected are produced, and their difference is cumulatively summed to produce a first accumulated signal. A second accumulated signal is similarly produced using samples of a cosine signal at the frequency to be detected, and an output signal indicating the presence or absence of the tone is produced from the sum of the squares of the two accumulated signals. The use of memories enables the detector to be readily multiplexed for detection of a plurality of tones on each of a plurality of channels.

Detection of tones in sampled signals

A digital signalling receiver translates pulse code modulated (PCM) tone signalling into a signal format compatible with a controller in an associated time division multiplex (TDM) telephone switching facility. In the receiver, steering signals are generated in synchronism with the operation of the switching facility to direct the operation of a time shared filter. The filter performs a plurality of filter functions with a series of PCM signals received from the TDM switching facility and generates therefrom series of filter signals relative each of the filter functions. A translator identifies two filter signals having larger amplitudes than the others and if the two signals persist substantially uninterrupted (a) through a predetermined period of time, (b) within a predetermined relative amplitude range and (c) one of the two signals having at least a predetermined signal to noise ratio relative another filter signal corresponding to an allpass filter function, the translator indicates the receipt of multifrequency signalling by generating the appropriate signals in the required signal format.

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Ottawa, Canada

Sorin Cohn-Sfetcu