Coarse carrier frequency offset estimation for CMMB mobile TV receiver

1. A method of estimating coarse frequency offset of received symbols based on a received frequency domain sample at a k th sub-carrier of a 53 rd Orthogonal Frequency Division Multiplexing (OFDM) data symbol in a j th time slot (TS) of a receiver in a China Multimedia Mobile Broadcasting (CMMB) mobile television network, said method comprising:

dividing a received sample, Y k j , into two sets of noise only tones and data plus noise tones D k j , wherein said two sets is given as: Y k j =

Y

k

j

=

{

Z

k

j

,

k

∈

α

1

D

k

j

+

Z

k

j

,

k

∈

α

2

,

wherein said α 1 represents a location of said noise only tones (Z k j ) and said α 2 represents a location of said data plus noise tones (D k j +Z k j );

obtaining a received sample only if there is a coarse frequency offset mismatch between a transmitter and said receiver, wherein said received sample is given as: Y k j =H k′ j *X k′ j +Z k j , wherein k′=k−Δf I ;

dividing a summation of a power of said data plus noise tones by a summation of a power of said noise only tones to obtain Λ k j , wherein said Λ k j is represented as:

Λ

k

j

=

∑

n

∈

α

2

⁢



Y

n

+

k

j



∑

n

∈

α

1

⁢



Y

n

+

k

j



;

and

and

estimating an integer coarse frequency offset estimate, Δ{circumflex over (f)} I j , of said received symbols based on a maximum value of said Λ k j , wherein said integer coarse frequency offset estimate, Δ{circumflex over (f)} I j , is given as:

Δ

⁢

⁢

f

^

I

j

=

argmax

k

∈

I

⁢

(

Λ

k

j

)

,

wherein I represents a search range and is given by a maximum frequency offset, [−Δf I,max , Δf I,max ].

2. The method of claim 1 , further comprising obtaining a received frequency domain sample, Y k j , wherein said Y k j is obtained as: Y k j =H k j *X k j +Z k j , wherein Y k j represents said received frequency domain sample at said k th sub-carrier of said 53 rd OFDM data symbol in said j th time slot (TS), wherein X k j represents said transmitted sample at said k th sub-carrier of said 53 rd OFDM data symbol in said j th time slot (TS), wherein H k j represents a channel frequency response at said k th sub-carrier of said 53 rd OFDM data symbol in said j th time slot (TS), and wherein Z k j represents an additive white Gaussian noise (AWGN) at said k th sub-carrier of said 53 rd OFDM data symbol in said j th time slot (TS).

3. The method of claim 1 , wherein said transmitted sample X k j is divided in a 111 samples length window based on a transmission location of said zeros tones.

4. The method of claim 1 , further comprising determining a spectral shift, Δf I , based on an energy difference between said zero tones at α 1 +Δf I and said non-zero tones at α 2 +Δf I .

5. The method of claim 1 , wherein said integer coarse frequency offset estimate, (Δ{circumflex over (f)} I j ), is given as:

Δ

⁢

⁢

f

⋀

I

j

=

argmin

k

∈

I

⁢

(

∑

p

=

j

-

q

j

⁢

Λ

k

p

)

to reduce false detection in said receiver.

6. A method of determining a coarse frequency offset of received symbols of a receiver in a China Multimedia Mobile Broadcasting (CMMB) mobile television network, said method comprising:

using a memory unit operatively connected to said receiver to store a computer program set of instructions;

using a processor for executing said program set of instructions, wherein said program set of instructions comprise:

dividing each received symbol into 128 pairs;

incrementing a counter corresponding to an index of a peak carrier within each pair;

determining a sparseness index from a power of a peak sub-carrier and a power of an odd sub-carrier of said each pair, wherein said index with maximum counts corresponds as a candidate coarse frequency offset;

shifting said each received symbol cyclically; and

obtaining a coarse frequency offset in said CMMB mobile television network using said sparseness index and the shifted symbol, wherein said coarse frequency offset results in a sparse channel estimate.

7. The method of claim 6 , wherein each of said 128 pairs comprise two sub-carriers, wherein a first sample comprises a location of a non-zero sub-carrier.

8. The method of claim 6 , wherein said sparseness index comprises a ratio of said power in said peak sub-carriers to said power in said odd sub-carrier of said pairs.

9. The method of claim 6 , wherein said power of peak sub-carrier in each said pair is accumulated into a first peak power accumulator, and wherein said power of said odd sub-carrier of said pair is accumulated into a second peak power accumulator.

10. The method of claim 6 , wherein said candidate coarse frequency offset lies within {+/−2*n, where n= . . . , −2, −1, 0, 1, 2 . . . } sub-carriers from said correct coarse frequency offset.

11. The method of claim 6 , wherein said coarse frequency offset results in said sparse channel estimate when said signal-to-noise ratio (SNR) is lower than a predefined threshold.

12. A China Multimedia Mobile Broadcasting (CMMB) television (TV) receiver to estimate a coarse frequency offset of received symbols based on a received frequency domain sample at a k th sub-carrier of a 53 rd Orthogonal Frequency Division Multiplexing (OFDM) data symbol in a j th time slot (TS) of the receiver, wherein said CMMB TV receiver comprises:

a memory unit comprising a computer program set of instructions;

a display unit operatively connected to said memory unit; and

a processor adapted to execute said computer program set of instructions, wherein said processor is adapted to:

divide a transmitted sample, X k j , into two sets of noise only tones and data plus noise tones D k j , wherein said two sets is given as:

X

k

j

=

{

0

,

k

∈

α

1

D

k

j

,

k

∈

α

2

.

wherein said α 1 represents a location of said zero tones (0) and said α 2 represents a location of said non-zero tones (D k j );

obtain a received sample only if there is a coarse frequency offset mismatch between a transmitter and said receiver, wherein said received sample is given as: Y k j =H k′ j *X k′ j +Z k j , wherein k′=k−Δf I ;

divide a summation of a power of said non-zero tones by a summation of a power of said zero-tones to obtain Λ k j , wherein said Λ k j is represented as:

Λ

k

j

=

∑

n

∈

α

2

⁢



Y

n

+

k

j



∑

n

∈

α

1

⁢



Y

n

+

k

j



;

and

estimate an integer coarse frequency offset estimate, Δ{circumflex over (f)} I j , of said received symbols when said Λ k j is a maximum.

13. The CMMB TV receiver of claim 12 , wherein said processor is adapted to obtain a received frequency domain sample, Y k j , wherein said Y k j is obtained as: Y k j =H k j *X k j +Z k j , wherein Y k j represents said received frequency domain sample at said k th sub-carrier of said 53 rd OFDM data symbol in said j th time slot (TS), wherein X k j represents said transmitted sample at said k th sub-carrier of said 53 rd OFDM data symbol in said j th time slot (TS), wherein H k j represents a channel frequency response at said k th sub-carrier of said 53 rd OFDM data symbol in said j th time slot (TS), and wherein Z k j represents an additive white Gaussian noise (AWGN) at said k th sub-carrier of said 53 rd OFDM data symbol in said j th time slot (TS).

14. The CMMB TV receiver of claim 12 , wherein said transmitted sample X k j is divided in a 111 samples length window based on a transmission location of said zeros tones.

15. The CMMB TV receiver of claim 12 , wherein said processor is adapted to determine spectral shift, Δf I , based on an energy difference between said zero tones at α 1 +Δf I and said non-zero tones at α 2 +Δf I .

16. The CMMB TV receiver of claim 12 , wherein said integer coarse frequency offset estimate, Δ{circumflex over (f)} I j , is given as:

Δ

⁢

⁢

f

⋀

I

j

=

argmin

k

∈

I

⁢

(

∑

p

=

j

-

q

j

⁢

Λ

k

p

)

wherein I represents a search range and is given by a maximum frequency offset, [−Δf I,max , Δf I,max ], and said integer coarse frequency offset estimate, (Δ{circumflex over (f)} I j ), is given as:

Δ

⁢

f

^

I

j

=

argmax

k

∈

I

(

∑

p

=

j

-

q

j

⁢

⁢

Λ

k

p

)

to reduce false detection in said receiver.

17. A mobile television (TV) receiver to estimate a coarse frequency offset in a China Multimedia Mobile Broadcasting (CMMB) mobile television network, said mobile TV receiver comprising:

a memory unit to store a received frequency domain sample;

a display unit operatively connected to said memory unit; and

a processor adapted to:

divide each received symbol into 128 pairs;

increment a counter corresponding to an index of a peak carrier within each pair;

determine a sparseness index from a power of a peak sub-carrier and a power of an odd sub-carrier of said each pair, wherein said index with maximum counts corresponds as a candidate coarse frequency offset;

shift said each received symbol cyclically; and

obtain a coarse frequency offset in said CMMB mobile television network using said sparseness index and the shifted symbol, wherein said coarse frequency offset results in a sparse channel estimate.

18. The mobile TV receiver of claim 17 , wherein each of said 128 pairs comprise two sub-carriers, wherein a first sample comprises a location of a non-zero sub-carrier.

19. The mobile TV receiver of claim 17 , wherein said sparseness index comprises a ratio of said power in said peak sub-carriers to said power in said odd sub-carrier of said pairs.

20. The mobile TV receiver of claim 17 , wherein said power of peak sub-carrier in each said pair is accumulated into a first peak power accumulator, and wherein said power of said odd sub-carrier of said pair is accumulated into a second peak power accumulator.

21. The mobile TV receiver of claim 17 , wherein said candidate coarse frequency offset lies within {+/−2*n, where n= . . . , −2, −1, 0, 1, 2 . . . } sub-carriers from said correct coarse frequency offset.

22. The mobile TV receiver of claim 17 , wherein said coarse frequency offset results in said sparse channel estimate when said signal-to-noise ratio (SNR) is lower than a predefined threshold.