Adaptive modulation scheme with simultaneous voice and data transmission

• US 6,304,593 B1
• Filed: 10/06/1998
• Issued: 10/16/2001
• Est. Priority Date: 10/06/1997
• Status: Expired due to Fees

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Goldsmith, Andrea, Alouini, Mohamed-Slim, Tang, Xiaoyi
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US09/167,406
• Time in Patent Office: 1,106 Days
• Field of Search: 375/216, 375/222, 375/377, 375/268, 375/300, 375/295, 375/279, 375/280, 455/522, 455/69, 332/149, 370/462, 370/468, 370/444
• US Class Current: 375/216
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 27/3461 in order to transmit a subchannel
• CPC Class Codes: H04L 5/12 the signals being represented by different phase modulations of a single carrier

Abstract

An adaptive modulation scheme for two streams of information that have different characteristics; preferably voice and data. The voice and data are transmitted on two quadrature channels, the I and Q channels. The amount of power in the channels is adaptively varied. The voice is given all the power it needs for reliable communication over a binary phase shift keying system. The data can have higher data rates, using an M-ary amplitude modulation scheme. The data uses whatever variable amount of power is left after transmitting the voice. The data rate is changed by changing the constellation size, so that a higher bit rate is transmitted, but requiring higher power.

Claims

1. A system for adaptively modulating voice and data on a channel, comprising:

a first voice channel, modulated according to a first characteristic;

a second data channel, maintained separate from said first voice channel and having characteristics which are modulated according to a second characteristic different than the first characteristic; and

an allocator, operating to determine a power required by voice transmission, to determine if enough power exists to transmit voice reliably over said channel and if not declaring a voice outage, and if enough power exists to transmit voice, then transmitting said voice using said enough power and determining if enough power exists to transmit data reliably over said channel, and if enough power exists to transmit data then using whatever power is left after said transmitting said voice to transmit said data at a variable rate which is determined by the amount of power that exists.

2. A system as in claim 1 wherein first and second data channels are modulated in quadrature relative to one another.

3. A method of transmitting voice and data over a channel with a varying signal to noise ratio, comprising:

forming a first stream representing voice information and a second stream representing data information;

determining a maximum power available for transmission over the channel;

determining a variable amount of power which will be needed to transmit voice without causing delay in a received voice signal, and allocating that amount of power to transmission of voice;

determining an amount of power left by subtracting said voice power from said total power and allocating that amount of power to data transmission; and

separately encoding said voice and data using different encoding systems, and transmitting said voice and data over the channel.

4. A system as in claim 3 wherein said voice is transmitted using binary phase shift keying, and said data is transmitted using adaptive M-ary amplitude modulation.

5. A system as in claim 3 wherein voice is transmitted using a first modulation phase and data is transmitted using a second modulation phase which is in quadrature relative to said first modulation phase.

6. A system as in claim 5 further comprising estimating an amount of noise in the channel, and determining said powers based on said noise estimate.

7. A method of transmitting voice and data over a single channel, comprising:

forming two independent information streams, each of which is different in its bit error sensitivity and delay characteristics;

determining a total amount of power which can be transmitted;

assigning a first kind of information to one of said data streams which has a better delay characteristic and assigning a second kind of information to the other of the information streams which has a better bit error sensitivity characteristic and more tolerance to delay;

determining a power which will be necessary to transmit said first kind of information without delay and using that amount of power to transmit the first kind of information and using a remainder of the power, which is a variable amount, to transmit the second kind of information; and

combining said streams and transmitting said streams over a channel.

8. A method as in claim 7 further comprising determining an estimate of channel signal to noise ratio;

and

dynamically assigning amounts of said powers depending on said channel signal to noise estimate.

9. A method as in claim 8 wherein said second information is data, and a power of transmitted data is changed by changing a constellation size representing a total number of available states to represent the data.

10. A method as in claim 9 wherein said constellation size is changed by changing a number of bits in the data symbol.

11. A method of adaptively transmitting both voice and data over a channel that has a varying signal to noise ratio, comprising:

estimating a signal to noise ration of the channel;

determining an amount of power which will be necessary to transmit a first kind of information, that is sensitive to delays in reception, over said channel without interruption or delay;

determining if a total available power that can be transmitted over the channel is sufficient to allow said first kind of information to be transmitted;

transmitting said first kind of information if the power is sufficient; and

using remaining variable amount of power to transmit a second kind of information that is less sensitive to said interruption or delay.

12. A method as in claim 11 further comprising determining if an amount of power left after said first kind of information is transmitted is sufficient to allow transmitting data, and establishing an outage if not, transmitting said second kind of information if so at a variable rate commensurate with a signal to noise ratio of the channel.

13. A method as in claim 11 wherein said first kind of information is voice, and said second kind of information is data.

14. A method as in claim 13 further comprising changing an amount of data power which is used by changing a constellation size of the data.

15. A method as in claim 14 wherein said changing a constellation size comprises changing a number of bits of the data symbol.

16. A method as in claim 13 further comprising establishing a voice outage when the power necessary to transmit voice is greater than a total available power for the channel.

17. A method of adaptively transmitting voice and data over a channel, comprising:

obtaining a voice stream and a data stream;

modulating said voice stream in a separate way from said data stream and adaptively separately controlling the powers of said voice stream and said data stream, said adaptively controlling being carried out in such a way that a probability of outage for voice is in all cases less than a probability of outage for data; and

wherein said adaptively controlling comprises first determining an amount of power which will be necessary to reliably transmit voice, and transmitting said voice with said amount of power, while transmitting data only with whatever variable power is left, whether or not that is sufficient for reliable transmission of data.

18. A method as in claim 17 wherein said transmitting of data comprises Gray coding the data using a constellation size and adaptively varying said constellation size depending on an available power and channel characteristic.