Method and apparatus for storing and forwarding voice signals

• US 6,006,189 A
• Filed: 10/10/1997
• Issued: 12/21/1999
• Est. Priority Date: 10/10/1997
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Corporation
• Inventors: Strawczynski, Leo, Gage, Bill (W.A.)
• Primary Examiner(s): Dorvil, Richemond
• Application Number:
  US08/948,418
• Time in Patent Office: 802 Days
• Field of Search: 704/270, 704/500, 704/200, 704/201, 379/67, 379/88, 375/219
• US Class Current: 704/270
• CPC Class Codes: G10L 19/16 Vocoder architecture
• CPC Class Codes: H04M 3/40 Applications of speech amplifiers
• CPC Class Codes: H04M 3/533 Voice mail systems
• CPC Class Codes: H04M 7/1235 where one of the core networks is a wireless network
• CPC Class Codes: H04M 7/1275 Methods and means to improve the telephone service quality, e.g. reservation, prioritisation or admission control
• CPC Class Codes: H04W 4/12 Messaging; Mailboxes; Announcements
• CPC Class Codes: H04W 88/181 Transcoding devices; Rate adaptation devices

Abstract

In recent years, the telecommunications industry has witnessed the proliferation of a variety of digital vocoders in order to meet bandwidth demands of different wireline and wireless communication systems. The rapid growth in the diversity of networks and the number of users of such networks is increasing the number of instances where two vocoders are placed in tandem to serve a single connection. Such arrangements of low bit-rate codecs can degrade the quality of the transmitted speech. To overcome this problem in the specific situation involving store-and-forward systems (e.g. voicemail), the invention provides a novel method and apparatus including a plurality of different vocoders that can be selectively invoked to process the voice signal so as to reduce signal degradation. Also, the apparatus has the capability to bypass the vocoder bank when exchanging data with a remote signal processor capable of accepting data frames in compressed format.

Claims

1. A voice storage and forwarding device for use in a communication network, comprising:

an audio signal encoder;

a storage medium in a data communicative relationship with said audio signal encoder, said storage medium capable to store data frames of a signal that conveys audio information issued by said audio signal encoder during a message recording transaction;

an audio signal decoder;

a first data pathway connected to said storage medium for transporting data frames in compressed form from said storage medium toward a first termination point of the communication network at which a subscriber terminal connected to the communication network may potentially effect a message retrieval transaction;

a second data pathway for transporting data frames toward said audio signal decoder, said audio signal decoder being in a data communicative relationship with a second termination point of the communication network at which a subscriber terminal connected to the communication network may potentially effect a message retrieval transaction; and

controlling means operative to select either one of said first and second data pathways for delivery of data frames from said storage medium during a given message retrieval transaction in dependence of the termination point of the communication network at which the subscriber terminal, with which said given message retrieval transaction is effected, is connected.

2. A voice storage and forwarding device as defined in claim 1, wherein said first termination point is part of a cellular network.

3. A voice storage and forwarding device as defined in claim 2, wherein said second termination point is part of a Public Switched Telephone Network (PSTN).

4. A voice storage and forwarding device as defined in claim 3, comprising a vocoder that combines said audio signal decoder and said audio signal encoder.

5. A voice storage and forwarding device as defined in claim 4, comprising a data frame routing controller responsive to commands issued by said controlling means to direct data frames from said storage device toward either one of said first and second data pathways.

6. A voice storage and forwarding device as defined in claim 5, including an out-of-band signaling link between said controlling means and said data frame routing controller.

7. A voice storage and forwarding device as defined in claim 6, wherein said controlling means is remote from said data frame routing controller.

8. A voice storage and forwarding device as defined in claim 7, wherein said controlling means is part of a gateway mobile switching center.

9. A voice storage and forwarding device as defined in claim 4, wherein said vocoder is part of a gateway mobile switching center.

10. A voice storage and forwarding device as defined in claim 2, wherein said first data pathway permits transport of data frames in encoded format without decoding.

11. A communication system, comprising:

a cellular communication network including at least one base station, said base station capable of establishing a data transmission link with a mobile terminal;

a Public Switched Telephone Network (PSTN),

an interface between said cellular communication network and said PSTN network; and

a voice storage and forwarding device, including;

a) a storage medium capable of storing data frames of an encoded audio signal issued by an audio signal encoder during a message recording transaction;

b) a first data pathway permitting transport of data frames of an encoded audio signal from said storage device toward said cellular network;

c) a second data pathway permitting transport of data frames of an encoded audio signal from said storage device toward said PSTN network;

d) an audio signal decoder in said second data pathway for decoding the data frames issued by said storage device; and

e) a data frame routing controller for directing data frames from said storage device toward a selected one of said first and second data pathways in dependence as to whether a subscriber terminal effecting a message retrieval transaction with said voice storage and forwarding device is connected to said cellular network or said PSTN network.

12. A communication system as defined in claim 11, wherein said second data pathway passes through a gateway mobile switching center.

13. A communication system as defined in claim 12, wherein said audio signal decoder is located in said gateway mobile switching center.

14. A communication system as defined in claim 13, wherein said gateway mobile switching center includes an audio signal encoder for processing an audio signal to generate encoded data frames for storage on said storage means.

15. A communication system as defined in claim 14, including an out-of-band signaling link between said gateway mobile switching center and said data frame routing controller to command said data frame routing controller to direct data frames toward a selected one of said data pathways.

16. A method for storing and forwarding audio information, comprising the steps of:

providing a storage medium capable of storing data frames of an encoded audio signal tssued by an audio signal encoder during a message recording transaction; and

during a message retrieval transaction performing either one of the following steps;

a) delivering data frames to a subscriber terminal without decoding if the subscriber terminal has a data frame decoding capability; and

b) delivering data frames toward a subscriber terminal without data frame decoding capability and decoding the data frames at a point intermediate between said storage medium and the subscriber terminal without data frame decoding capability.

17. A voice storage and forwarding device for use in a communication network, comprising:

a) a storage medium capable to store data frames of a signal in compressed format, the signal conveying audio information issued during a message recording transaction;

b) a data frame routing controller coupled to said storage medium to route data frames from said storage medium toward a selected destination during a message retrieval transaction, said data frame routing controller being responsive to out-of-band signaling to;

i) direct data frames from said storage medium toward a first pathway leading to a subscriber terminal at which the given message retrieval transaction is effected, the first pathway including a decoder remote from the subscriber terminal to convert the data frames into a decompressed format, when the out-of-band signaling is indicative that the subscriber terminal lacks a capability to locally decompress the data frames;

ii) direct data frames from said storage medium toward a second pathway leading to a subscriber terminal at which the given message retrieval transaction is effected, the second pathway delivering data frames in a compressed format to the subscriber terminal connected to the second pathway, when the out-of-band signaling is indicative that the subscriber terminal is capable to locally decompress the data frames.