System and method for implementing an end-to-end error-correcting protocol in a voice band data relay system

• US 6,865,220 B2
• Filed: 02/09/2001
• Issued: 03/08/2005
• Est. Priority Date: 02/11/2000
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: LSI Logic Corporation (Broadcom, Inc.)
• Inventors: Abrishami, Mehrdad
• Primary Examiner(s): Fan, Chieh M.
• Assistant Examiner(s): Perilla, Jason M.
• Application Number:
  US09/779,530
• Publication Number:
  US 20010046259A1
• Time in Patent Office: 1,488 Days
• Field of Search: 370/229, 370/230, 370231-235, 370/230.1, 370/401, 375/222, 709/230, 709/234, 709/235, 709/238
• US Class Current: 375/220
• CPC Class Codes: H04L 12/6418 Hybrid transport

Abstract

A system and method to establish an end-to-end error correcting protocol between two voice band data modems over a network including voice band data relay gateways, where part of the end-to-end connection is via low data rate narrowband network. Using a partial implementation of V.42 LAPM protocol within the data relay gateways, the system allows the independent selection of modulation schemes at each gateway as well as increased user data throughput by removing non-informational data. Flow control of the user data to match the channel rate of the narrowband network may also be provided.

Claims

1. A method of data transmission between first and second modems over a network comprising a narrowband network, the method comprising:

providing first and second gateways, the first gateway connected to the first modem, the second gateway connected to the second modem, and the first and second gateways connected via the narrowband network;

transmitting modulated signals from the first modem to the first gateway;

demodulating the signals at the first gateway to obtain demodulated data;

transmitting the demodulated data over the narrowband network;

receiving the demodulated data at the second gateway;

re-modulating the demodulated data at the second gateway;

transmitting the re-modulated signals from the second gateway to the second modem;

establishing an end-to-end error correcting protocol between the first and second modems;

monitoring at the first gateway the demodulated data to be transmitted over the narrowband network;

determining if an amount of demodulated data waiting in a transmit buffer transmitted over the narrowband network exceeds a first value and if so, generating a valid receive not ready (RNR) frame, modulating the RNR frame at the first gateway, and transmitting the RNR frame to the first modem, thereby suspending the transmission of signals from the first modem; and

determining if the amount of demodulated data waiting in the transmit buffer transmitted over the narrowband network is less than a second value and, if so, generating a valid receive ready (RR) frame, modulating the RR frame at the first gateway, and transmitting the RR frame to the first modem, thereby resuming the transmission of signals from the first modem, wherein transmitting the demodulated data over the narrowband network comprises;

removing first non-informational data from the demodulated data at the first gateway to provide modified demodulated data;

transmitting the modified demodulated data without the first non-informational data over the narrowband network to the second gateway;

generating second non-informational data at the second gateway; and

combining the second non-informational data and the modified demodulated data.

2. The method according to claim 1, wherein monitoring the demodulated data further comprises:

comparing the amount of the demodulated data stored in the transmit buffer to a third value to determine if the transmission of the modulated signals from the first modem should be suspended.

3. The method according to claim 1, further comprising:

maintaining at the first gateway a first value indicating a current flow control state of the first modem;

receiving at the first gateway a supervisory frame from the narrowband network, the supervisory frame for control of flow of data between the modems, the supervisory frame including a second value indicating a flow control state;

comparing the first and second values;

modifying the supervisory frame from a RR frame to a valid RNR frame if the first value does not match the second value; and

transmitting the RNR frame to the first modem.

4. The method according to claim 1, wherein removing first non-informational data from the demodulated data comprises:

storing the demodulated data in the transmit buffer at the first gateway; and

removing first non-informational data from the transmit buffer;

and wherein combining the second non-informational data and the modified demodulated data comprises;

storing the modified demodulated data in a receive buffer at the second gateway; and

inserting the second non-informational data into the receive buffer after a last received frame of the modified demodulated data.

5. The method according to claim 4, wherein the non-informational data comprises interframe fill flags.

6. The method according to claim 1, further comprising:

discriminating at the first gateway between voice and voice band modulated data signals; and

switching at the first gateway to an alternate mode of signal processing to process voice band data as modem tones and modulated signals instead of voice.

7. The method according to claim 1, wherein the first gateway comprises a codec, a voice band data modem, and a fax modem, the method further comprising:

discriminating voice, voice band modulated data signals, and fax modulated data signals from the first modem;

processing the voice signals using the codec;

processing the voice band modulated data signals using the voice band data modem; and

processing the fax modulated data signals using the fax modem.

8. The method according to claim 1, further comprising:

implementing at the first gateway, first modem training between the first modem and the first gateway;

implementing at the second gateway, second modem training between the second modem and the second gateway;

adjusting a duration of the first modem training based on progress of the second modem training; and

adjusting a duration of the second modem training based on progress of the first modem training.

9. The method according to claim 1, wherein the first gateway has a first memory having a memory size, the method further comprising:

modifying at the first gateway supervisory data so that a maximum message length transmitted between the first and second modems is less than a predetermined limit based on the size of the first memory.

10. The method according to claim 1, wherein

the narrowband network comprises a digital network;

and

the modulated signals from the first modem comprise pulse code modulated signals.

11. The method according to claim 1, wherein the narrowband network comprises a satellite network.

12. The method according to claim 1, wherein the narrowband network has a channel rate, the method further comprising:

selecting at each of the first and second gateways a modulation and demodulation scheme based on capabilities of the first and second modems and the channel rate.

13. The method according to claim 12, wherein the first and second modems comprise V.34 modems, and the capabilities of the first and second modems are determined by decoding a V.8 answer sequence generated by the first and second modems.

14. The method according to claim 12, wherein the first modem comprises a modem selected from the group consisting of a V.32 modem, a V.32 bis modem, a V.34 modem operating in auto-mode, and a V.90 modem operating in auto-mode, and wherein the selection of the modulation and demodulation scheme comprises detection of an 1800 Hz tone from the first modem.

15. The method according to claim 12, wherein the modulation and demodulation scheme and a rate of modulation and demodulation at the first and second gateways are different.

16. The method according to claim 15, wherein the modulation and demodulation scheme at the first gateway is V.32 at 4800 bps, and the modulation and demodulation scheme at the second gateway is V.22 bis at 2400 bps.

17. The method according to claim 15, wherein the modulation and demodulation scheme at the first gateway is V.32 at 9600 bps, and the modulation and demodulation scheme at the second gateway is V.32 at 4800 bps.

18. The method according to claim 15, wherein the modulation and demodulation scheme at the first gateway is V.32 bis at 14,400 bps or 12,000 bps or 9600 bps or 7200 bps or 4800 bps, and the modulation and demodulation scheme at the second gateway is V.32 bis at 14,400 bps or 12,000 bps or 9600 bps or 7200 bps or 4800 bps.

19. The method according to claim 1, wherein the end-to-end error correcting protocol is detected by the first gateway by decoding a V.8 sequence transmitted by the first and second modems.

20. The method according to claim 1, wherein the error correcting protocol is selected from a group consisting of V.42 LAPM and an error correcting protocol as defined in V.42 Annex A.

21. A method of data transmission between first and second modems over a network comprising a narrowband network, the method comprising:

providing first and second gateways, the first gateway connected to the first modem, the second gateway connected to the second modem, the first and second gateways connected via the narrowband network;

transmitting a first signal from the first modem to the first gateway;

demodulating the first signal at the first gateway to generate demodulated data;

modifying the demodulated data to remove first non-informational data;

transmitting the modified demodulated data over the narrowband network;

receiving the modified demodulated data at the second gateway;

regenerating the demodulated data by inserting second non-informational data into the modified demodulated data;

modulating the regenerated demodulated data at the second gateway to generate a second signal;

transmitting the second signal from the second gateway to the second modem; and

establishing an end-to-end protocol between the first and second modems, the protocol selected from a group consisting of an error correcting protocol or an asynchronous protocol.

22. The method according to claim 21, wherein modifying the demodulated data comprises:

storing the demodulated data in a transmit buffer at the first gateway; and

removing first non-informational data from the transmit buffer; and

wherein regenerating the demodulated data comprises;

storing the modified demodulated data in a receive buffer at the second gateway; and

inserting second non-informational data into the receive buffer after a last received frame of the modified demodulated data.

23. The method according to claim 22, wherein the non-informational data comprises interframe fill flags.

24. The method according to claim 21, wherein the first gateway has a first memory having a memory size, the method further comprising:

modifying at the first gateway supervisory data so that a maximum message length transmitted between the first and second modems is less than a predetermined limit based on the size of the first memory.

25. The method according to claim 21, wherein

the narrowband network comprises a digital network;

and

the first and second signals comprise pulse code modulated signals.

26. A gateway for voice band data transmission over a network comprising a first modem connected to the gateway, a second modem connected to a second gateway, and a narrowband network connecting the gateway and the second gateway, the gateway comprising:

a voice band data modem for demodulating signals received from a first user modem to generate demodulated data for transmission over the narrowband network, and for modulating data received from the narrowband network;

a voice band data protocol for inter-networking of the first and second modems;

a memory having a memory size; and

a partial V.42 protocol for;

detecting establishment of an end-to-end error correcting protocol between the first and second modems,

monitoring at the first gateway the demodulated data,

suspending transmission of the signals from the first modem if a transmission rate of the demodulated data to be transmitted over the narrowband network exceeds a first value,

resuming transmission of the signals from the first modem if the transmission rate is less than a second value, and

modifying supervisory data received from the narrowband network so that a maximum message length transmitted between the first and the second modems is less than a predetermined limit based on the size of the memory.

27. The gateway according to claim 26 comprising:

a receive buffer for storing the data received from the narrowband network; and

a transmit buffer for storing the demodulated data to be transmitted over the narrowband network;

and wherein the partial V.42 protocol compares an amount of the demodulated data stored in the transmit buffer to a third value to determine if transmission of the signals from the first modem should be suspended.

28. The gateway according to claim 27 wherein the suspension of transmission of signals from the first modem comprises:

generating a valid RNR frame;

modulating the RNR frame; and

transmitting the RNR frame to the first modem.

29. The gateway according to claim 28 wherein the resumption of transmission of signals from the first modem comprises:

generating a valid RR frame;

modulating the RR frame; and

transmitting the RR frame to the first modem.

30. The gateway according to claim 27, wherein the partial V.42 protocol further comprises logic for:

removing first non-informational data from the transmit buffer; and

inserting second non-informational data into the receive buffer after a last received frame of the data received from the narrowband network.

31. A method of data transmission between first and second modems over a network comprising a narrowband network, the method comprising:

providing first and second gateways, the first gateway connected to the first modem, the second gateway connected to the second modem, and the first and second gateways connected via the narrowband network;

transmitting modulated signals from the first modem to the first gateway;

demodulating the signals at the first gateway to obtain demodulated data;

transmitting the demodulated data over the narrowband network;

receiving the demodulated data at the second gateway;

re-modulating the demodulated data at the second gateway;

transmitting the re-modulated signals from the second gateway to the second modem;

establishing an end-to-end error correcting protocol between the first and second modems;

monitoring at the first gateway the demodulated data to be transmitted over the narrowband network;

determining if an amount of demodulated data waiting in a buffer to be transmitted over the narrowband network exceeds a first value and if so, generating a valid receive not ready (RNR) frame, modulating the RNR frame at the first gateway, and transmitting the RNR frame to the first modem, thereby suspending the transmission of signals from the first modem; and

determining if the amount of demodulated data waiting in the buffer to be transmitted over the narrowband network is less than a second value and, if so, generating a valid receive ready (RR) frame, modulating the RR frame at the first gateway, and transmitting the RR frame to the first modem, thereby resuming the transmission of signals from the first modem, further comprising;

implementing at the first gateway, first modem training between the first modem and the first gateway;

implementing at the second gateway, second modem training between the second modem and the second gateway;

adjusting a duration of the first modem training based on progress of the second modem training; and

adjusting a duration of the second modem training based on progress of the first modem training.

32. A method of data transmission between first and second modems over a network comprising a narrowband network, the method comprising:

providing first and second gateways, the first gateway connected to the first modem, the second gateway connected to the second modem, and the first and second gateways connected via the narrowband network;

transmitting modulated signals from the first modem to the first gateway;

demodulating the signals at the first gateway to obtain demodulated data;

transmitting the demodulated data over the narrowband network;

receiving the demodulated data at the second gateway;

re-modulating the demodulated data at the second gateway;

transmitting the re-modulated signals from the second gateway to the second modem;

establishing an end-to-end error correcting protocol between the first and second modems;

monitoring at the first gateway the demodulated data to be transmitted over the narrowband network;

determining if an amount of demodulated data waiting in a buffer to be transmitted over the narrowband network exceeds a first value and if so, generating a valid receive not ready (RNR) frame, modulating the RNR frame at the first gateway, and transmitting the RNR frame to the first modem, thereby suspending the transmission of signals from the first modem; and

determining if the amount of demodulated data waiting in the buffer to be transmitted over the narrowband network is less than a second value and, if so, generating a valid receive ready (RR) frame, modulating the RR frame at the first gateway, and transmitting the RR frame to the first modem, thereby resuming the transmission of signals from the first modem, wherein the first gateway has a first memory having a memory size, the method further comprising;

modifying at the first gateway supervisory data so that a maximum message length transmitted between the first and second modems is less than a predetermined limit based on the size of the first memory.