Rate adaptive modem

• US 20100329176A1
• Filed: 08/03/2007
• Published: 12/30/2010
• Est. Priority Date: 08/03/2007
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Miller, Mark, Agarwal, Anil
• Granted Patent: US 8,068,435 B2
• Time in Patent Office: Days
• US Class Current: 370/316
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0016 involving special memory structures, e.g. look-up tables

Abstract

A communication system transmitting signals over a network using a transmission waveform in which a plurality of data packets are transmitted in a payload field of a transmission frame, the system includes a transmitter, which has a transmitting portion that sends information including user data in the data packets and a user data rate portion that dynamically changes the data rate of the user data to the highest rate possible for current link conditions by changing the waveform. The communication system also includes a receiver, which has a receiving portion that receives the information data packets and a reconfiguration portion that reconfigures the receiving portion based on the waveform parameters.

Claims

1. A communication apparatus operative for at least one of transmission and reception of signals in a network via a transmission waveform using a transmission frame format and carrying control information as well as user data in data packets, comprising;

a source of a plurality of waveforms, at least two of said waveforms having different waveform parameters;

a user data rate selector that is operative to dynamically change a user data rate of the user data by selecting from said source one of said at least two waveforms with different waveform parameters.

2. The apparatus of claim 1, wherein the waveform parameters are least one of a type of modulation and a rate of coding.

3. The apparatus of claim 2, wherein the type of modulation is one of BPSK, QPSK, 8-PSK and 16-APSK and the rate of coding is one of ½

, ⅔

, ¾

, ⅞

, 19/20 and uncoded.

4. The apparatus of claim 2, wherein the selection of the waveform is based on at least one of a user selection and a transmission condition of transmitted signals.

5. The apparatus of claim 4, wherein the transmission condition is a signal quality of the transmitted signals corresponding to carrier to noise ratio, Es/No,

wherein the user data rate selector selects a waveform from said at least two waveforms based on the Es/No value.

6. The apparatus of claims 5, wherein the source is a look up table storing a plurality of waveforms, including said at least two waveforms, and the user data rate selector is operative to select a waveform from said look up table.

7. The apparatus of claim 5, wherein the user rate selector is configured to:

obtain a measured Es/No value;

calculate a carrier to noise ratio limit based on the measured Es/No value and a predetermined error margin;

compare a preferred carrier to noise ratio of the transmission waveform and the calculated carrier to noise ratio limit;

select a waveform with highest user data rate from among waveforms that have a preferred carrier to noise ratio that is less than or equal to the calculated carrier to noise ratio limit if the calculated carrier to noise ratio limit is less than the preferred carrier to noise ratio of the transmission waveform;

select a waveform with a higher user data rate if the calculated carrier to noise ratio limit is equal to or higher than the preferred carrier to noise ratio of the waveform with the higher user date rate by a predetermined hysteresis;

dynamically reconfigure the apparatus to use the selected waveform as the transmission waveform; and

dynamically modify the waveform parameters in the transmission frame to a type of modulation and a rate of coding corresponding to the selected waveform.

8. The apparatus of claim 1, further comprising:

a portion operative to form and communicate over an embedded channel, said embedded channel being adapted to carry embedded channel data transmitted by another apparatus communicating over the network.

9. The apparatus of claim 8, wherein the embedded channel comprises a protocol stack configured to use IP packets.

10. The apparatus of claim 9, wherein the embedded channel is formed within a point-to-point link between a first station and a second station.

11. The apparatus of claim 9, wherein the embedded channel is formed on a network allowing communication among a plurality of stations.

12. The apparatus of claim 9, wherein applications in the apparatus use at least one of UDP and TCP transport protocols in communications over the embedded channel.

13. The apparatus of claim 9, wherein the protocol stack uses one of a General Frame Protocol (GFP) and High-level Link Control (HDLC) protocol.

14. The apparatus of claim 8, wherein the selection of a waveform with different parameters is based on at least one of a user selection and a transmission condition of the transmitted signals.

15. The apparatus of claim 14, wherein the transmission condition is a signal quality of the transmitted signals corresponding to carrier to noise ratio, Es/No, measured by a device receiving the transmission waveform, and

wherein the user data rate selector selects the waveform from a plurality of waveforms based on the Es/No value.

16. The apparatus of claims 15, wherein the user data rate selector selects the waveform from a look up table in the apparatus.

17. The apparatus of claim 15, wherein the user rate selector is configured to:

obtain a measured Es/No value over the embedded channel;

calculate a carrier to noise ratio limit based on the measured Es/No value and a predetermined error margin;

compare a preferred carrier to noise ratio of the transmission waveform and the calculated carrier to noise ratio limit;

select a waveform with highest user data rate from among waveforms that have a preferred carrier to noise ratio that is less than or equal to the calculated carrier to noise ratio limit if the calculated carrier to noise ratio limit is less than the preferred carrier to noise ratio of the transmission waveform;

select a waveform with a higher user data rate if the calculated carrier to noise ratio limit is equal to or higher than the preferred carrier to noise ratio of the waveform with the higher user date rate by a predetermined hysteresis;

dynamically reconfigure the apparatus to use the selected waveform as the transmission waveform; and

dynamically modify the waveform parameters in the transmission frame to a type of modulation and a rate of coding corresponding to the selected waveform.

18. The apparatus of claim 6, further comprising:

a table configuration portion operable to create the look up table by modifying an initial table of waveforms, the initial table of waveforms comprising at least one waveform with a modulation of BPSK, QPSK, 8-PSK and 16-APSK and at least one waveform with a coding of ½

, ⅔

, ¾

, ⅞

, 19/20 and uncoded,

wherein the table configuration portion is configured to modify the initial table by performing the following;

delete waveform entries with modulation and coding values that are disallowed,

delete waveform entries that violate baseband interface rates of at least one of the apparatus and a station communicating with the apparatus,

sort remaining waveform entries in descending order of preferred Es/No values, and

delete waveform entries with an information bits per symbol value that is lower than or equal to that of a waveform entered lower on the table.

19. The apparatus of claim 1, wherein said apparatus comprises a transmitter for transmitting said transmission waveform to another apparatus over said network.

20. The apparatus of claim 1, wherein said apparatus comprises a receiver for receiving said transmission waveform from another apparatus over said network.

21. A communication system transmitting signals, said system comprising:

a plurality of communication apparatus, as recited in claim 1, at least one of said apparatus being operative to at least transmit signals and at least one of said apparatus being operative to at least receive signals; and

at least one link coupling said plurality of apparatus.

22. The system of claim 21, wherein the waveform parameters comprise at least one of a type of modulation and a rate of coding.

23. The system of claim 22, wherein the type of modulation is one of BPSK, QPSK, 8-PSK and 16-APSK and the rate of coding is one of ½

, ⅔

, ¾

, ⅞

, 19/20 and uncoded.

24. The system of claim 21, wherein said apparatus operative to transmit signals and said apparatus operative to receive signals respectively comprise a portion operative to form and communicate over an embedded channel.

25. The system of claim 24, wherein the embedded channel comprises a protocol stack configured to use IP packets.

26. The system of claim 25, wherein the embedded channel is formed within a point-to-point link.

27. The system of claim 25, wherein the embedded channel is formed on a network allowing communication among a plurality of stations.

28. The system of claim 27, wherein applications in at least one apparatus use at least one of UDP and TCP transport protocols in communications over the embedded channel.

29. The system of claim 25, wherein applications in at least one apparatus use one of a General Frame Protocol (GFP) and High-level Link Control (HDLC) protocol.

30. The system of claim 24, wherein said apparatus operable to receive signals further comprises:

a signal value portion operable to obtain a measured signal value of the received transmission waveform.

31. The system of claim 30, wherein the measured signal value comprises a carrier to noise ratio, Es/No, of the received transmission waveform.

32. The system of claim 31, wherein said apparatus operable to receive signals further comprises:

a user data rate selector that determines a type of modulation and a rate of coding to be used on the transmission waveform based on the Es/No value.

33. The system of claim 32, wherein the user data rate selector selects the waveform by using a look up table in said apparatus operable to receive signals.

34. The system of claim 32, wherein the user rate selector is configured to:

calculate a carrier to noise ratio limit based on the Es/No value and a predetermined error margin;

compare a preferred carrier to noise ratio of the transmission waveform and the calculated carrier to noise ratio limit;

select a waveform with highest user data rate from among waveforms that have a preferred carrier to noise ratio that is less than or equal to the calculated carrier to noise ratio limit if the calculated carrier to noise ratio limit is less than the preferred carrier to noise ratio of the transmission waveform;

select a waveform with a higher user data rate if the calculated carrier to noise ratio limit is equal to or higher than the preferred carrier to noise ratio of the waveform with the higher user date rate by a predetermined hysteresis; and

transmit the selected waveform to the transmitter using the respective embedded channels.

35. The system of claim 31, wherein the Es/No value is transmitted to said apparatus operable to transmit signals over the embedded channel.

36. The system of claim 24, wherein said apparatus operable to receive signals is configured with a first predetermined IP address identifying said apparatus operable to receive signals and a second predetermined address for identifying said apparatus operable to transmit signals, and

wherein said apparatus operable to transmit signals is configured with the first predetermined IP address identifying said apparatus operable to transmit signals and the second predetermined address for identifying said apparatus operable to receive signals.

37. The system of claim 36, wherein said apparatus operable to receive signals and said apparatus operable to transmit signals respectively comprise an application comprising a protocol stack with an IP adaptation layer that switches a source IP address and a destination IP address in messages received over the embedded channel.

38. The system of claim 33, wherein said apparatus operable to receive signals further comprises:

a table configuration portion is operable to create the look up table by modifying an initial table of waveforms, the initial table of waveforms comprising at least one waveform with a modulation of BPSK, QPSK, 8-PSK and 16-APSK and at least one waveform with a coding of ½

, ⅔

, ¾

, ⅞

, 19/20 and uncoded,

wherein the table configuration portion is configured to modify the initial table by performing the following;

delete waveform entries with modulation and coding values that are disallowed,

delete waveform entries that violate baseband interface rates of at least one of said apparatus operable to receive signals and said apparatus operable to transmit signals,

sort remaining waveform entries in descending order of preferred Es/No values, and

delete waveform entries with an information bits per symbol value that is lower than or equal to that of a waveform entered lower on the table.

39. A method of transmission and reception of signals in a network via a transmission waveform using a transmission frame format and carrying control information as well as user data in data packets, the method comprising:

including the payload field in the transmission frame and subdividing the payload field into a plurality of subframes, each subframe comprising a predetermined number of information bits;

multiplexing the plurality of data packets into each of the subframes;

including in the transmission frame a sync field comprising a unique word; and

including in the transmission frame a header field comprising a waveform ID field,

wherein each subframe comprises;

a subheader field comprising multiplexer control information;

an overhead channel field comprising overhead channel data; and

a user channel field comprising user channel data.