Ringdown and ringback signalling for a computer-based multifunction personal communications system

• US 5,535,204 A
• Filed: 10/25/1993
• Issued: 07/09/1996
• Est. Priority Date: 01/08/1993
• Status: Expired due to Term

• Current Assignee: Multi-Tech Systems Incorporated
• Original Assignee: Multi-Tech Systems Incorporated
• Inventors: Li, Ping
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): Nguyen, Chau T.
• Application Number:
  US08/142,807
• Time in Patent Office: 988 Days
• Field of Search: 370/94.1, 370/24, 370/31, 370/79, 370/81, 370/80, 370/111, 370/112, 370/118, 370/69.1, 370/61, 370/110.1, 370/76, 370/29, 370/30, 375/214, 375/220, 375/222, 375/216, 379/88, 379/89, 379/67, 379/207, 379/235, 379/90, 379/93, 379/96-98, 379/110, 379/201, 381/29, 381/36, 381/38, 395/2, 395/2.2, 395/2.21, 395/2.28, 395/2.3
• US Class Current: 370/495
• CPC Class Codes: G10L 19/04 using predictive techniques
• CPC Class Codes: H04L 12/6418 Hybrid transport
• CPC Class Codes: H04L 2012/6424 Access arrangements
• CPC Class Codes: H04L 2012/6427 Subscriber Access Module; Concentrator; Group equipment
• CPC Class Codes: H04L 2012/6459 Multiplexing, e.g. TDMA, CDMA
• CPC Class Codes: H04L 2012/6475 N-ISDN, Public Switched Telephone Network [PSTN]
• CPC Class Codes: H04L 2012/6481 Speech, voice
• CPC Class Codes: H04L 2012/6491 Echo cancellation
• CPC Class Codes: H04L 2012/6494 Silence suppression
• CPC Class Codes: H04L 27/3416 in which the information is carried by both the individual signal points and the subset to which the individual points belong, e.g. using coset coding, lattice coding, or related schemes
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 69/04 Protocols for data compression, e.g. ROHC
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: H04M 1/247 Telephone sets including user guidance or feature selection means facilitating their use user interfaces specially adapted for cordless or mobile telephones H04M1/724
• CPC Class Codes: H04M 1/2473 Telephone terminals interfacing a personal computer, e.g. using an API (Application Programming Interface) details of API H04M7/0021
• CPC Class Codes: H04M 1/2477 for selecting a function from a menu display H04M1/2474 takes precedence
• CPC Class Codes: H04M 1/253 Telephone sets using digital voice transmission
• CPC Class Codes: H04M 1/57 Arrangements for indicating or recording the number of the calling subscriber at the called subscriber's set at the operator set in a manual exchange H04M5/20
• CPC Class Codes: H04M 1/6033 for providing handsfree use or a loudspeaker mode in telephone sets arrangements for preventing acoustic echo H04M9/08
• CPC Class Codes: H04M 1/6505 storing speech in digital form
• CPC Class Codes: H04M 1/663 : Preventing unauthorised calls to a telephone set
• CPC Class Codes: H04M 11/06 : Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
• CPC Class Codes: H04M 11/064 : Data transmission during pauses in telephone conversation
• CPC Class Codes: H04M 11/068 : using time division multiplex techniques; integrated services digital networks H04Q11/0428
• CPC Class Codes: H04M 2203/4509 : Unified messaging with single point of access to voicemail and other mail or messaging systems
• CPC Class Codes: H04M 3/002 : Applications of echo suppressors or cancellers in telephonic connections in two-way loud-speaking telephone systems H04M9/08, echo suppressors or cancellers per se H04B3/20
• CPC Class Codes: H04M 3/42 : Systems providing special services or facilities to subscribers specially adapted for wireless communication networks H04W4/00
• CPC Class Codes: H04M 3/436 : Arrangements for screening incoming calls , i.e. evaluating the characteristics of a call before deciding whether to answer it based on the calling party profile H04M3/42059; based on location H04M3/42348; based on presence H04M3/42365; diversion H04M3/54
• CPC Class Codes: H04M 3/5307 : for recording messages comprising any combination of audio and non-audio components
• CPC Class Codes: H04M 3/533 : Voice mail systems
• CPC Class Codes: H04M 3/567 : Multimedia conference systems
• CPC Class Codes: H04M 7/006 : Networks other than PSTN/ISDN providing telephone service, e.g. Voice over Internet Protocol (VoIP) , including next generation networks with a packet-switched transport layer H04L65/00 takes precedence; aspects not specific to the type of network H04M3/00; special services in those networks H04M3/42
• CPC Class Codes: H04M 7/1295 : Details of dual tone multiple frequency signalling
• CPC Class Codes: H04N 1/00204 : with a digital computer or a digital computer system, e.g. an internet server programmed control between transmitter and receiver or between image input and image output device H04N1/32561
• CPC Class Codes: H04N 1/00206 : Transmitting or receiving computer data via an image communication device, e.g. a facsimile transceiver H04N1/00236 takes precedence

Abstract

The voice over data component of a personal communications system enables the operator to simultaneously transmit voice and data communication to a remote site. This voice over data function dynamically allocates data bandwidth over the telephone line depending on the demands of the voice grade digitized signal. The user may enter voice over data mode from a data transfer mode by lifting the handset of the telephone connected to the modem. The off-hook condition is sensed and software sends a supervisory packet to the remote site to invoke voice-over-data mode. The remote telephone will simulate a ring to alert the remote user, and the local telephone will simulate a ringback to inform the caller that the remote unit is responding.

Claims

1. In a multi-function communications system, a method of switching from data only communication to simultaneous voice and data communication, comprising the steps of:

invoking a data only communication connection between a local site equipped with a local modem and a remote site equipped with a remote modem;

alerting the local modem of a desire to switch from data only mode to simultaneous voice and data mode by an action by a local user;

sending a ringdown packet from the local modem to the remote modem;

receiving the ringdown packet at the remote modem and sending in response thereto a ringback packet from the remote modem to the local modem; and

enabling a simultaneous voice and data connection between the local modem and the remote modem in response to the receipt of the ringback packet by the local modem.

3. The method according to claim 1 wherein the step of invoking a data communication connection further comprises the step of sending CCITT V.42 standard modem data packets and wherein the step of sending a ringdown data packet further comprises the step of preparing a supervisory packet constructed as the CCITT V.42 modem standard data packet using bits in a header which are undefined by the CCITT V.42 standard.

4. The method according to claim 1 wherein the step of enabling a simultaneous voice and data connection further includes the steps of:

creating a plurality of outgoing data packets containing computer digital data;

creating a plurality of outgoing voice packets containing digital voice data;

detecting substantially silent periods having absence of voice information in the digital voice data and producing in response thereto a silence flag;

transmitting only the plurality of outgoing data packets when the silence flag indicates the absence of voice information; and

transmitting both the plurality of outgoing voice packets and the plurality of outgoing data packets when the silence flag indicates the presence of voice information.

5. The method according to claim 4 wherein the step of enabling a simultaneous voice and data connection further includes the steps of:

receiving local voice signals from a local user;

digitizing the local voice signals to produce the digital voice data;

compressing the digital voice data into compressed digital voice data; and

placing the compressed digital voice data into the plurality of outgoing voice packets.

6. The method according to claim 1 wherein the step of invoking a data communication connection further includes the steps of establishing a data connection over a telephone line which includes as at least part of the connection a cellular telephone link and periodically transmitting a cellular supervisory packet to maintain the connection as long as the remote site receives the cellular supervisory packet within a predetermined period of time, and terminating the data communication connection if the cellular supervisory packet is not received at the remote site within the predetermined period of time.

2. An apparatus for full-duplex transmission of voice and data information for use with a personal computer and for switching between data only transmission and simultaneous voice and data transmission, comprising:

data interface means connected for transferring data to and from the personal computer;

telephone line interface means for connection to a telephone line;

telephone handset means for receiving local voice signals from a local user and for conveying remote voice signals from a remote user to the local user;

full-duplex conversion means connected to the telephone handset means for converting the local voice signals into outgoing digital voice data and for converting incoming digital voice data into the remote voice signals;

voice compression means connected to the full-duplex conversion means for compressing the outgoing digital voice data into compressed outgoing digital voice data and for decompressing compressed incoming digital voice data packets into the incoming digital voice data;

main control means connected for

receiving the compressed outgoing digital voice data packets from the voice compression means,

receiving outgoing computer digital data from the personal computer through the data interface means,

placing the outgoing computer digital data into outgoing computer digital data packets,

sending the outgoing computer digital data packets to the telephone line interface means for transmission to a remote site through the telephone line,

sending to and receiving supervisory packets from the remote site indicating the desire to switch between data only transmission and simultaneous voice and data transmission; and

multiplexing and transmitting compressed outgoing digital voice data and outgoing computer digital data.

7. The apparatus according to claim 2 wherein the main control means is further operable for detecting silent periods in the outgoing digital voice data and for producing in response thereto a silence flag and wherein the main control means is further operable for transmitting outgoing computer digital data on the telephone line when the silence flag indicates the absence of voice information and wherein the main control means is further operable for multiplexing and transmitting both the compressed outgoing digital voice data and the outgoing computer digital data on the telephone line when the silence flag indicates the presence of voice information.

8. The apparatus according to claim 2 wherein the main control means is further operable for periodically transmitting a cellular supervisory packet on the telephone line and for maintaining an active connection to the remote site over the telephone line if the remote site acknowledges receipt of the cellular supervisory packet within a predetermined period of time and for dropping the active connection to the remote site over the telephone line if the remote site fails to acknowledge receipt of the cellular supervisory packet within a predetermined period of time.

9. The apparatus according to claim 2 wherein the voice compression means is further operable for compressing the outgoing digital voice data into compressed outgoing digital voice data by performing the steps of:

a.) removing any DC bias in the outgoing digital voice data to produce a normalized outgoing digital voice signal;

b.) pre-emphasizing the normalized outgoing digital voice signal to produce a pre-emphasized outgoing digital voice signal;

c.) dividing the pre-emphasized outgoing digital voice signal into segments to produce a current speech segment and a past speech segment;

d.) predicting the pitch of the current speech segment to form a pitch prediction;

e.) calculating the gain of the pitch of the current speech segment to form a prediction gain;

f.) reconstructing the past speech segment from a compressed past segment to produce a reconstructed past segment;

g.) finding the innovation in the current speech segment by comparing the pitch prediction to the reconstructed past segment to produce an error signal;

h.) determining the maximum amplitude in the current speech segment;

i.) quantizing the error signal using a code book generated from a representative set of speakers and environments to produce a minimum mean squared error matching the form of an index into the code book; and

j.) recording the pitch prediction, the prediction gain, the maximum amplitude and the index into the code book in a packet as the compressed outgoing digital voice data.