Coarse frequency offset estimation for digital multimedia broadcasting
View Patent ↗A method of estimating a coarse frequency offset of Digital Multimedia Broadcasting (DMB) transmission frames includes receiving the DMB transmission frames including a synchronization channel having a phase reference symbol, circularly shifting the phase reference symbol by applying a circular shift to the phase reference symbol, numerically correlating the circularly shifted phase reference symbol with a known correct phase reference symbol to obtain a highest peak and a side peaks of the numeric correlation, and computing a phase reference symbol angle based on a multiplication of the peak and a carrier spacing of the DMB transmission frames. The peak is determined when the circularly shifted phase reference symbol is equal to the known correct phase reference symbol. The peak and side peaks corresponding to the peak are operated in a range of a maximum value of the circular shift.
1. An apparatus for estimating a coarse frequency offset in Digital Multimedia Broadcasting (DMB) transmission frames, said apparatus comprising:
a receiver that receives a phase reference symbol;
a memory unit operatively connected to said receiver and comprising a programmable set of instructions;
a display unit operatively connected to said memory unit;
a buffer operatively connected to said memory unit, wherein said buffer comprises data fields for a peak of a correlator output, a frequency offset of said DMB frames, a counter, and a change flag; and
a processor that processes said programmable set of instructions comprising:
receiving said DMB transmission frames comprising a synchronization channel comprising a phase reference symbol;
circularly shifting said phase reference symbol by applying a circular shift to said phase reference symbol;
numerically correlating the circularly shifted phase reference symbol with a known correct phase reference symbol to obtain a highest peak and a side peaks of the numeric correlation;
computing a phase reference symbol angle based on a multiplication of said peak and a carrier spacing of said DMB transmission frames;
summing said phase reference symbol angle for all of sub carriers within said phase reference symbol;
computing an average of said highest peak over said DMB transmission frames to reduce effects of said side peaks if a frequency offset exists in said buffer;
updating said change flag;
incrementing said counter; and
determining a buffer entry if said buffer entry with said counter is greater than or equal to a predefined parameter.
2. The apparatus of claim 1 , wherein said peak is obtained when said shifted phase reference symbol is equal to said correct phase reference symbol.
3. The apparatus of claim 1 , wherein a lowest peak is selected and replaced in said buffer if said frequency offset does not exist in said buffer.
4. The apparatus of claim 3 , wherein said change flag is periodically updated and said counter is set to 1.
5. The apparatus of claim 1 , wherein said buffer entry is stored in a decision buffer if said buffer entry is greater than or equal to said predefined parameter, and wherein said decision buffer comprises said peak and said frequency offset.
6. The apparatus of claim 1 , wherein the peak in said decision buffer is selected and a corresponding frequency offset is returned as said coarse frequency offset.
7. The apparatus of claim 6 , wherein all unchanged buffer entries are decayed in said buffer and said decision buffer.
8. The apparatus of claim 1 , wherein said buffer entry is determined if said peak terminates.
9. A method of estimating a coarse frequency offset of Digital Multimedia Broadcasting (DMB) transmission frames, said method comprising:
receiving a phase reference symbol;
providing a buffer comprising data fields for a peak of a correlator output, a frequency offset of said DMB frames, a counter, and a change flag;
receiving said DMB transmission frames comprising a synchronization channel comprising a phase reference symbol;
circularly shifting said phase reference symbol by applying a circular shift to said phase reference symbol;
numerically correlating the circularly shifted phase reference symbol with a known correct phase reference symbol to obtain a highest peak and side peaks of the numeric correlation;
computing a phase reference symbol angle based on a multiplication of said peak and a carrier spacing of said DMB transmission frames;
summing said phase reference symbol angle for all of sub carriers within said phase reference symbol;
computing an average of said highest peak over said DMB transmission frames to reduce effects of said side peaks if a frequency offset exists in said buffer;
updating said change flag;
incrementing said counter; and
determining a buffer entry if said buffer entry with said counter is greater than or equal to a predefined parameter.
10. The method of claim 9 , wherein said peak is obtained when said shifted phase reference symbol is equal to said correct phase reference symbol.
11. The method of claim 9 , wherein a lowest peak is selected and replaced in said buffer if said frequency offset does not exist in said buffer.
12. The method of claim 11 , wherein said change flag is periodically updated and said counter is set to 1.
13. The method of claim 9 , wherein said buffer entry is stored in a decision buffer if said buffer entry is greater than or equal to said predefined parameter, and wherein said decision buffer comprises said peak and said frequency offset.
14. The method of claim 9 , wherein the peak in said decision buffer is selected and a corresponding frequency offset is returned as said coarse frequency offset.
15. The method of claim 14 , wherein all unchanged buffer entries are decayed in said buffer and said decision buffer.
16. The method of claim 9 , wherein said buffer entry is determined if said peak terminates.
17. A system for estimating a coarse frequency offset of Digital Multimedia Broadcasting (DMB) transmission frames, said system comprising:
means for receiving a phase reference symbol;
a buffer comprising data fields for a peak of a correlator output, a frequency offset of said DMB frames, a counter, and a change flag;
means for receiving said DMB transmission frames comprising a synchronization channel comprising a phase reference symbol;
means for circularly shifting said phase reference symbol by applying a circular shift to said phase reference symbol;
means for numerically correlating the circularly shifted phase reference symbol with a known correct phase reference symbol to obtain a highest peak and side peaks of the numeric correlation;
means for computing a phase reference symbol angle based on a multiplication of said peak and a carrier spacing of said DMB transmission frames;
means for summing said phase reference symbol angle for all of sub carriers within said phase reference symbol;
means for computing an average of said highest peak over said DMB transmission frames to reduce effects of said side peaks if a frequency offset exists in said buffer;
means for updating said change flag;
means for incrementing said counter; and
means for determining a buffer entry if said buffer entry with said counter is greater than or equal to a predefined parameter.
18. The system of claim 17 , wherein said peak is obtained when said shifted phase reference symbol is equal to said correct phase reference symbol.
19. The system of claim 17 , wherein a lowest peak is selected and replaced in said buffer if said frequency offset does not exist in said buffer.
20. The system of claim 17 , wherein said buffer entry is determined if said peak terminates.