Synchronizing a modem and vocoder of a mobile station

• US 20060285557A1
• Filed: 06/15/2005
• Published: 12/21/2006
• Est. Priority Date: 06/15/2005
• Status: Active Grant

• Current Assignee: ST-Ericcson SA (Telefonaktiebolaget LM Ericsson)
• Original Assignee: ST Wireless SA
• Inventors: Anderton, David O., Yiin, Jeffrey L.
• Granted Patent: US 7,512,157 B2
• Time in Patent Office: Days
• US Class Current: 370/503
• CPC Class Codes: H04J 3/0632 Synchronisation of packets and cells, e.g. transmission of voice via a packet network, circuit emulation service [CES] queuing arrangements in packet switching elements H04L49/90; synchronising systems for the synchronous transmission of a pulse code modulated video signal with one or more other pulse code modulated signals H04N7/56

Abstract

In one embodiment, the present invention includes a method for determining a level of a buffer that stores data samples. The level may be determined at a predetermined position of a data frame sequence. Based on the level of the buffer at this position, a vocoder and modem of a mobile station may be synchronized. One or both of the vocoder and modem may be adjusted to attain the synchronization. Thus a rate mismatch between the vocoder and modem may be resolved.

Claims

1. A method comprising:

determining a level of a first buffer that stores data samples at a predetermined position of a data frame sequence; and

synchronizing a vocoder and a modem of a mobile station based on the level of the first buffer.

2. The method of claim 1, further comprising pre-filling the first buffer with pre-loaded signal samples corresponding to a preselected depth of the first buffer.

3. The method of claim 2, further comprising:

comparing the level of the first buffer to the preselected depth; and

measuring a differential between the level of the first buffer and the preselected depth.

4. The method of claim 3, further comprising comparing the differential to a threshold value.

5. The method of claim 4, wherein synchronizing the vocoder and the modem comprises adjusting a timing of the vocoder if the differential is greater than the threshold value.

6. The method of claim 1, further comprising adjusting a timing of the vocoder to synchronize the vocoder and the modem, wherein the modem is operating at an adjusted rate corresponding to an adjusted oscillator frequency of the mobile station based on movement of the mobile station with respect to a base station with which the mobile station is communicating.

7. The method of claim 1, wherein synchronizing the vocoder and the modem comprises interpolating a block of the data samples in the vocoder by adding or dropping one data sample from the block.

8. An apparatus comprising:

a first buffer to store a speech block;

a vocoder coupled to the buffer to encode the speech block; and

a modem coupled to the vocoder to modulate the encoded speech block, wherein at least the vocoder is controlled to maintain the modem and the vocoder in substantial synchronization.

9. The apparatus of claim 8, wherein the apparatus comprises a digital signal processor including the modem and the vocoder.

10. The apparatus of claim 9, wherein at least one of the modem and the vocoder comprises a software routine executed on the digital signal processor.

11. The apparatus of claim 8, further comprising logic to determine a level of the first buffer and to compare the level of the first buffer to a predetermined buffer level.

12. The apparatus of claim 11, wherein the logic is to increment a count if the level of the first buffer is different than the predetermined buffer level.

13. The apparatus of claim 12, wherein the apparatus is to adjust the vocoder if the count is greater than a threshold count.

14. The apparatus of claim 13, wherein the adjustment comprises an interpolation of the speech block.

15. An article comprising a machine-accessible storage medium containing instructions that cause a system to:

compare an actual level of a first buffer at a selected time within a data structure to a predetermined level;

analyze whether a differential exists between the actual level and the predetermined level; and

determine whether to adjust a vocoder coupled to the first buffer based on the differential.

16. The article of claim 15, further comprising instructions that cause the system to adjust the vocoder immediately if the differential is above a first threshold.

17. The article of claim 15, further comprising instructions that cause the system to increment a count if the differential is below a first threshold but greater than a second threshold.

18. The article of claim 17, further comprising instructions that cause the system to adjust the vocoder if the count is greater than a third threshold.

19. The article of claim 15, further comprising instructions that cause the system to interpolate a speech block in the vocoder to thereby adjust the vocoder.

20. A mobile station comprising:

an input device to receive voice information from a user and convert the voice information to an analog signal;

an analog-to-digital converter (ADC) coupled to the input device to convert the analog signal into digitized speech data;

a first buffer coupled to ADC to store the digitized speech data;

a digital signal processor (DSP) coupled to the first buffer to encode the digitized speech data into encoded digitized speech data and modulate the encoded digitized speech data into modulated encoded digitized speech data, wherein the DSP is to synchronize the encoding and the modulation based on a level of the first buffer;

radio frequency (RF) circuitry coupled to the DSP; and

an antenna coupled to the RF circuitry.

21. The mobile station of claim 20, wherein the first buffer is integrated within the DSP.

22. The mobile station of claim 20, wherein the DSP and the RF circuitry are at least in part integrated within the same integrated circuit.

23. The mobile station of claim 20, wherein the DSP is to:

determine if a differential exists between the level of the first buffer at a predetermined position in a data sequence to a predetermined level for the first buffer; and

adjust a timing of the encoding if the differential is greater than a first threshold.

24. The mobile station of claim 23, wherein the DSP is to immediately adjust the timing of the encoding via adding or dropping a plurality of samples of the digitized speech data.

25. The mobile station of claim 23, wherein the DSP is to:

increment a count of data sequences if the differential is less than the first threshold but greater than a second threshold

compare the count to a third threshold; and

adjust the timing of the encoding if the differential is greater than the third threshold.

26. The mobile station of claim 25, wherein the DSP is to adjust the timing of the encoding via linear interpolation of a block of the digitized speech data.