Cellular communication network with vocoder sharing feature

• US 6,138,022 A
• Filed: 07/23/1997
• Issued: 10/24/2000
• Est. Priority Date: 07/23/1997
• Status: Expired due to Term

• Current Assignee: Blackberry Limited
• Original Assignee: Nortel Networks Corporation
• Inventors: Strawczynski, Leo, Gage, Bill W. A., Rabipour, Rafi
• Primary Examiner(s): Bost, Dwayne D.
• Assistant Examiner(s): Persino, Raymond B.
• Application Number:
  US08/898,867
• Time in Patent Office: 1,189 Days
• Field of Search: 455/445, 455/422, 455/436, 455/67.4, 455/11.1, 455/561, 455/560, 375/242, 370/238
• US Class Current: 455/445
• CPC Class Codes: H04W 88/181 Transcoding devices; Rate adaptation devices

Abstract

The present invention provides a novel system and a method for improving the voice quality of wireless-to-wireless calls or wireless-to-fixed terminal calls, while permitting a more efficient utilization of network resources. In a first aspect, the invention provides a communication system including a plurality of base stations connected to one another through a digital network (such as TDM, frame relay or ATM). Also, a plurality of vocoder channels, separate from the individual base stations, provide a data flow path from the base stations to wireline terminals first through the digital network via a Mobile Switching Center and finally through a landline network. In a wireless-to-wireless call, the compressed audio signal travels from one base station to another without undergoing any de-compression/compression. This avoids undesirable vocoder tandeming known to degrade voice quality. If the call is identified as being of a wireless-to-wireline terminal nature, the data is directed to a vocoder channel for decompression into PCM samples. The samples are then transmitted to the fixed terminal through the landline network. The main advantage of this network architecture is that fewer vocoders are required by comparison to prior art systems, therefore fewer costs are incurred. In addition, voice quality is improved.

Claims

1. A communication network, comprising:

a group of base stations, each base station being operative to establish an RF communication with a wireless terminal over an air interface, each base station being capable of exchanging with a respective wireless terminal data packets of compressed audio information, each base station being free of a vocoder;

a group of vocoders for selectively encoding or decoding audio information from either one of said base stations, said group of vocoders including less vocoders than base stations in said group of base stations;

a digital network interconnecting said group of base stations and said group of vocoders, said digital network being operative to establish a first pathway to allow at least two base stations of said group of base stations to exchange data packets of compressed audio information, said pathway being free of vocoders, said digital network being further operative to establish a second pathway between a base station and a vocoder to allow a base station of said group of base stations to exchange data packets of compressed audio information with a vocoder of said group of vocoders.

2. A communication network as defined in claim 1, comprising a control system operatively connected to said digital network to control routing of data packets of compressed audio information, said control system being capable of selectively directing data packets toward a given base station.

3. A communication network as defined in claim 1, further comprising a branch connected to said digital network to establish a pathway from said digital network toward a landline network, said branch including a vocoder of said group of vocoders capable of decoding a data packet of compressed audion information directed through said branch.

4. A communication network as defined in claim 3, wherein said landline network is the PSTN.

5. A communication network as defined in claim 3, wherein said landline network is the ISDN.

6. A communication network as defined in claim 3, wherein said landline network is the Internet.

7. A communication network as defined in claim 3, wherein a vocoder of said group of vocoders comprises:

an encoder for converting a speech signal in non-compressed format to compressed format;

a decoder for converting a speech signal in compressed format to non-compressed format.

8. A communication network as defined in claim 7, wherein a vocoder of said group of vocoders includes an input for receiving a data packet of compressed audio information and an output for generating a packet of PCM samples.

9. A communication network as defined in claim 3, wherein said branch includes an echo canceller.

10. A communication network as defined in claim 3, wherein said network includes a plurality of branches, each said branch including a vocoder of said group of vocoders.

11. A communication network as defined in claim 3, wherein said control system utilizes out-of-band signaling to route the data packet of compressed audio information through either one of said digital network and said branch.

12. A communication network as defined in claim 11, wherein said branch includes a mobile switching center.

13. A communication network as defined in claim 1, wherein said digital network includes frame relays.

14. A communication network as defined in claim 1, wherein said digital network is an Asynchronous Transfer Mode network.

15. A communication network as defined in claim 1, further comprising a data communication channel including a first end and a second end, said first end being connected to said digital network, and said second end being capable of being connected to a landline network, said data communication channel comprising a certain vocoder of said group of vocoders between said first end and said second end, said certain vocoder being capable of decompressing a data packet of compressed audio information.

16. A communication network as defined in claim 15, wherein said certain vocoder is further capable of compressing a data packet of audio information that is received from the landline network.

17. A communication network as defined in claim 16, wherein said data communication channel includes an echo canceller.