Method and system for increasing the accuracy of frequency offset estimation in multiple frequency hypothesis testing in an E-UTRA/LTE UE receiver
A mobile device receives a radio frequency (RF) signal comprising a primary synchronization sequence (PSS) and a secondary synchronization sequence (SSS). The mobile device performs multiple frequency hypothesis (MFH) testing via multiple MFH branches. A PSS correlation process is performed for each MFH branch. Frequency offset for receiving data is estimated using resulting correlation data. A desired offset is placed in each MFH branch. A baseband signal is frequency offset per MFH branch according to the desired frequency offset before the PSS correlation process. A received PSS is detected based on a maximum PSS correlation over the entire set of MFH branches. A frequency offset is estimated for the MFH branch associated with the detected PSS by combining an associated residual frequency with a corresponding desired offset. The frequency offset estimate is used for baseband signal processing and/or adjusting a reference oscillator frequency at the mobile device.
1. A method for communication, comprising:
receiving a radio frequency (RF) signal comprising a primary synchronization sequence (PSS) and a secondary synchronization sequence (SSS);
generating PSS correlation data for each multiple frequency hypothesis (MFH) branch of a set of MFH branches;
determining a maximum PSS correlation peak in said PSS correlation data;
estimating a residual frequency offset for said RF signal a MFH branch producing said maximum PSS correlation peak; and
estimating a frequency offset for said RF signal by combining said estimated residual frequency offset with a frequency offset associated with said MFH branch producing said maximum PSS correlation peak.
2. The method according to claim 1 , further comprising:
determining a desired offset for each MFH branch of said set of MFH branches.
3. The method according to claim 2 , further comprising:
frequency offsetting a baseband signal of said RF signal for each MFH branch of said set of MFH branches based on said determined desired offset.
4. The method according to claim 3 , further comprising:
generating said PSS correlation data after said frequency offsetting said baseband signal.
5. The method according to claim 4 , further comprising:
selecting a candidate PSS for each MFH branch of said set of MFH branches based on identifying a maximum branch PSS correlation peak in each MFH branch.
6. The method according to claim 5 , further comprising detecting a received PSS of said received RF signal, from said candidate PSS of each MFH branch, by determining a maximum candidate PSS, wherein said maximum candidate PSS contains said maximum PSS correlation peak.
7. The method according to claim 1 , further comprising:
baseband processing said RF signal using said estimated frequency offset.
8. The method according to claim 1 , further comprising:
adjusting a local reference oscillator frequency of a mobile device based on said estimated frequency offset.
9. A system for communication, comprising:
an input port configured to receive a radio frequency (RF) signal comprising a primary synchronization sequence (PSS) and a secondary synchronization sequence (SSS);
a plurality of multiple frequency hypothesis (MFH) branches coupled to said input port, wherein each MFH branch is configured to:
generate PSS correlation data,
estimate a residual frequency offset for said RF signal, and
estimate a frequency offset for said received RF signal by combining said estimated residual frequency offset with a desired frequency offset; and
a peak detector coupled to said MFH branches, wherein said peak detector is configured to determine a detected PSS by determining a maximum PSS correlation peak in said PSS correlation data from each MFH branch.
10. The system according to claim 9 , further comprising:
a mixing frequency generator coupled to said MFH branches, wherein said mixing frequency generator is configured to place the desired frequency offset in said MFH branches.
11. The system according to claim 10 , wherein said MFH branches are further configured to frequency offset a baseband signal of said RF signal based on said desired frequency offset.
12. The system according to claim 11 , wherein said MFH branches are further configured to generate said PSS correlation data after said frequency offsetting said baseband signal.
13. The system according to claim 12 , wherein said MFH branches are further configured to select a candidate PSS based on identifying a maximum branch PSS correlation peak in each MFH branch.
14. The system according to claim 9 , wherein said peak detector is further configured to communicate said detected PSS to baseband signal processing circuitry.
15. The system according to claim 9 , wherein said peak detector is further configured to initiate an adjustment of a local reference oscillator frequency based on said estimated frequency offset.
16. A method for communication, comprising:
receiving a radio frequency (RF) signal comprising a primary synchronization sequence (PSS) and a secondary synchronization sequence (SSS);
generating PSS correlation data for each multiple frequency hypothesis (MFH) branch of a set of MFH branches;
determining a maximum PSS correlation peak in said PSS correlation data;
estimating a residual frequency offset for said RF signal in a MFH branch producing said maximum PSS correlation peak;
estimating a frequency offset for said RF signal by combining said estimated residual frequency offset with a frequency offset associated with said MFH branch producing said maximum PSS correlation peak; and
initiating an adjustment of a reference oscillator of a communications device based on said frequency offset.
17. The method of claim 16 , further comprising:
determining a desired offset for each MFH branch of said set of MFH branches.
18. The method of claim 17 , further comprising frequency offsetting a baseband signal of said RF signal for each MFH branch of said set of MFH branches based on said determined desired offset.
19. The method of claim 18 , further comprising selecting a candidate PSS for each MFH branch of said set of MFH branches based on identifying a maximum branch PSS correlation peak in each MFH branch.
20. The method of claim 19 , further comprising detecting a received PSS of said received RF signal, from said candidate PSS of each MFH branch, by determining a maximum candidate PSS, wherein said maximum candidate PSS contains said maximum PSS correlation peak.