Modem signaling using speech components over a voice channel of a wireless communication system

1. A method of communicating with a modem via a voice channel of a wireless communication system, comprising the steps of:

generating a composite carrier comprising a speech component together with a single-frequency signaling tone, wherein the generating step further comprises generating the composite carrier such that the power ratio of the speech component to the single-frequency signaling tone is under zero decibels; and

sending the composite carrier including the speech component and the single-frequency signaling tone to a modem across a voice channel of a wireless communication system.

2. The method set forth in claim 1 , wherein the generating step further comprises generating the composite carrier such that the power ratio of the speech component to the single-frequency signaling tone is less than −12 dB.

3. The method set forth in claim 2 , wherein the generating step further comprises generating the composite carrier such that the power ratio of the speech component to the single-frequency signaling tone is greater than −20 dB.

4. The method set forth in claim 1 , wherein the speech component comprises multiple spectral components in the audio frequency range that each vary over time in amplitude or frequency, or both.

5. The method set forth in claim 4 , wherein the speech component comprises human speech.

6. The method set forth in claim 4 , wherein the speech component comprises synthesized speech.

7. The method set forth in claim 1 , wherein the single-frequency signaling tone is continuous and the speech component is intermittent.

8. A method of communicating data between a vehicle and call center via a voice channel of a wireless communication system, comprising the steps of:

establishing a voice channel connection between a vehicle telematics unit and a call center via a wireless cellular network;

generating a modem signaling carrier comprising a single frequency tone together with a speech component, wherein the modem signaling carrier has a power ratio of speech component to single frequency tone that is less than zero decibels (dB);

sending the modem signaling carrier over the voice channel connection using an EVRC-B vocoder;

establishing a data communication session over the voice channel connection in response to the modem signaling carrier; and thereafter

carrying out data communications between the vehicle telematics unit and call center during the data communication session.

9. The method set forth in claim 8 , wherein the generating step further comprises generating the modem signaling carrier such that the power ratio of the speech component to the tone is less than −12 dB.

10. The method set forth in claim 9 , wherein the generating step further comprises generating the modem signaling carrier such that the power ratio of the speech component to the tone is greater than −20 dB.

11. The method set forth in claim 8 , wherein the speech component comprises multiple spectral components in the audio frequency range that each vary over time in amplitude or frequency, or both.

12. The method set forth in claim 11 , wherein the speech component comprises human speech.

13. The method set forth in claim 11 , wherein the speech component comprises synthesized speech.

14. The method set forth in claim 8 , wherein the tone is continuous and the speech component is intermittent.