U.S. Philips Corporation

Kar B Chan

Hendrik Ten Pierick

Cornelis C Schuur

Roelof J De Haas

Steven J Koelewijn

A digital radio communication system (1) is known, for example based on the DECT standard, in which radio communication of digital speech or data between primary (BS1) and secondary (MS1) stations takes place via duplex FDMA/TDMA connection. Channel allocation therein is dynamic. If necessary because of the receiving conditions, the secondary station (MS1) can initiate a so-called handover by searching for a free channel offering better receiving conditions. In accordance with the invention, this handover is seamless. Digital speech bursts are exchanged via different time slots (ts) during a number of frames (fr), these being digital speech data and copy digital speech data. After verification that the copy data is valid, i.e. that communication has been established via a free channel, handover takes place. The original data and the copy data are stored in a cyclic buffer (SB5) so that the phase shift (d) between the original data and the copy data is eliminated. Subsequently, the channel via which the original data was transported is released. In one embodiment a speech pointer (SPP) for reading speech freely progresses along the cyclic buffer (SB5) and a radio pointer (RFP), progressing along the buffer (SB5) and controlling the writing of speech bursts, is adapted during handover to the phase shift (d) between time slots involved in the handover.

Digital radio communication system and primary and secondary station for

Circuit arrangement including a parabolic generator for supplying a periodic, substantially parabolic signal to an output terminal during a trace time and an arcuate signal generator for supplying an arcuate signal, which has the shape of, for example, a half sine wave, during a retrace time. At the start of the retrace time, the arcuate signal and its derivatives are given values which are substantially equal to the corresponding values of the parabolic signal at the end of the trace time. The arcuate signal generator is adapted to generate the arcuate signal in a time-discrete manner under the control of switching pulses supplied by a pulse circuit. The pulse circuit is adapted to supply a constant number of switching pulses for generating the arcuate signal in spite of variations in the retrace time, so that the arcuate signal and its derivative assume values which are substantially equal to the corresponding values of the parabolic signal at the start of the trace time.

Growing community of inventors

Eindhoven, Netherlands

Kar B Chan