Method and apparatus for telecommunications using internet protocol
View Patent ↗In a wireless packet switching telecommunications network, voice services are provided by having a compressor/decompressor in each mobile station to provide each voice packet with a compressed header. Voice data and signalling data are sent separately and in different data formats to the air interface. The compressed header may be an M bit and a cyclically reset timeclick_number, which is decompressed by use of a wallclock which counts reset cycles to reinstate the voice packet headers. Alternatively, RTP agents are provided at the compression and decompression points, and voice packets are sent without headers over a “high quality” network such as a frame relay or ATM network. Compression state of a voice packet header can be established by sending call setup information over an out-of-band channel between compression points in a mobile station and in the network.
1. A method of compressing and decompressing headers for a packet switching network comprises providing in each compressed header a cyclically-reset timeclick_number representing the sampling time of the packet payload; increasing the timeclick_number by 1 for each sample duration time, counting the reset cycles, and from the count of reset cycles and a received timeclick_number, providing a sequence number and timestamp for providing a decompressed header.
2. A method according to claim 1 further comprising including in each compressed header an M bit; and decompressing a header when no M bit is received by increasing the packet sequence number of the decompressed header by the difference of the timeclick_numbers between the packet for which no M bit is received and the last previously received packet having an M bit.