초록 ▼

A method and apparatus for achieving tandem free operation (TFO) including bypass transcoding and cross transcoding in a communication system. The present invention provides communication of compressed voice signals, or voice signals compressed in a common format, between wireless mobile stations ac

A method and apparatus for achieving tandem free operation (TFO) including bypass transcoding and cross transcoding in a communication system. The present invention provides communication of compressed voice signals, or voice signals compressed in a common format, between wireless mobile stations across a PSTN by bypassing vocoders residing in the MSC/BSC of the communication system, or between network elements of an ATM network. In a wireless network, a capability signal, preferably being a low frequency tone, is transmitted by the terminating MSC/BSC to the originating MSC/BSC to indicate that the terminating element is capable of transcoding or transcoding and cross transcoding. The originating element responsively generates an optional LF tone and a 2100 Hz tone to disable network cancellers between the originating element and the terminating element in the forward direction. The terminating element, then, responsively generates a 2100 Hz tone to disable network echo cancellers between the terminating element and the originating element in the backward direction, whereby the vocoders of the network are bypassed. Compression and decompression of voice signals is only provided by the vocoders integrated into the terminating wireless mobile stations.

대표청구항 ▼

[ We claim:] [1.] In a voice communication system which includes an originating unit having a first vocoder, a first base station in wireless communication with and serving the originating unit, a first BSC/MSC having a vocoder in the first base station, a terminating unit having a second vocoder, a

[ We claim:] [1.] In a voice communication system which includes an originating unit having a first vocoder, a first base station in wireless communication with and serving the originating unit, a first BSC/MSC having a vocoder in the first base station, a terminating unit having a second vocoder, a second base station in wireless communication with and serving the terminating unit, a second BSC/MSC having a vocoder in the second base station, the base stations being interconnectable via a voice channel, the units each containing an A/D-D/A converter, apparatus for achieving TFO of the system wherein the vocoders in both BSC/MSCs are bypassed, which apparatus comprises:signaling means in the second base station responsive to the receipt of a call initiation signal sent by the originating unit via the first BSC/MSC and the channel for sending a short duration, low frequency signal via the channel to the first base station, the frequency of the signal indicating the type and capabilities of the vocoder in the terminating unit and having a frequency which is significantly less than the rolloff frequency of the A/D-D/A converters;analyzing means in the first base station for analyzing the received low frequency signal and determining whether digital signals from the first vocoder are compatible with the second vocoder; andcontrol means in the base stations(a) for directing digital voice signals between the units around, and bypassing, both BSC/MSC vocoders in the base stations if the second vocoder is compatible with the digital signals from the first vocoder, and(b) for directing digital voice signals between the vocoders of the units through the BSC/MSC vocoders in a tandem mode if the second vocoder is not compatible with the digital signals from the first vocoder.