Method and mobile device for joint cell identity detection and cell measurement for an LTE system

1. A method for communication, the method comprising:

in a mobile device:

receiving a first OFDM symbol containing a first received cell-specific reference subcarrier;

extracting the first received cell-specific reference subcarrier of the first OFDM symbol;

receiving a second OFDM symbol containing a second received cell-specific reference subcarrier;

extracting the second received cell-specific reference subcarrier of the second OFDM symbol;

generating a pair of received subcarriers by computing a scalar product of the first received cell-specific reference subcarrier and a conjugate of the second received cell-specific reference subcarrier;

providing a reference sequence, the reference sequence containing pairs of reference subcarriers for multiple combinations of cell-IDs, wherein a pair of reference subcarriers is a scalar product of a first cell-specific reference subcarrier and the conjugate of a second cell-specific reference subcarrier at a same resource element in a time-frequency grid as the first and second received cell-specific subcarriers respectively;

correlating the pair of received subcarriers with each pair of reference subcarriers of the reference sequence to generate a cell-specific correlation value associated with each cell-ID of a plurality of cell-specific correlation values; and

determining the cell-ID of a strongest cell by searching for a highest correlation value within the plurality of cell-specific correlation values and assigning the cell-ID associated with the highest correlation value to the cell-ID of the strongest cell.

2. The method according to claim 1 , wherein a sequence of pairs of received subcarriers is generated for a specific number of a plurality of cell-specific reference subcarriers contained within the first and the second OFDM symbol, wherein a correlation value associated with each cell-ID is generated for each of the pairs of received subcarriers within the sequence, and wherein a single correlation value associated with each cell-ID of the plurality of cell-specific correlation values is generated by summing up the correlation values of each of the pairs of received subcarriers over a frequency axis of the LTE time-frequency grid.

3. The method according to claim 2 , wherein a single correlation value associated with each cell-ID of the plurality of cell-specific correlation values is generated by summing up the correlation value of each of the pairs of received subcarriers over a time axis and frequency axis.

4. The method according to claim 1 , wherein the reference sequence contains pairs of reference subcarriers for all possible combination of cell-IDs and length of cyclic prefix.

5. The method according to claim 1 , wherein the first OFDM symbol and the second OFDM symbol are three or six OFDM symbols apart from one another on the LTE time-frequency grid.

6. The method according to claim 1 , wherein the pair of received subcarriers is generated by computing the scalar product of two cell-specific reference subcarriers of a same frequency bin or an adjacent frequency bin of the LTE time-frequency grid.

7. The method according to claim 1 , wherein generating a pair of received subcarriers involves averaging the scalar product over a plurality of radio frames.

8. The method according to claim 1 , wherein the plurality of cell-specific correlation values is sorted in a descending manner, and on the plurality of cell-specific correlation values an interference cancellation is performed for determining the cell-IDs of remaining interfering cells.

9. The method according to claim 8 , wherein on a pre-defined number N of highest correlation values COR i a successive interference cancellation is performed, starting with the highest correlation value COR 0 =COR 0 , according to:

COR

_

i

=

COR

i

-

∑

m

=

0

i

-

1

⁢

COR

_

m

⁢

RCC

i

,

m

⁢

⁢

i

=

1

⁢

⁢

…

⁢

⁢

N

-

1

;

wherein RCC i,m is a cross correlation between cell-specific reference subcarrier i and cell-specific reference subcarrier m.

10. The method according to claim 9 , wherein on the remaining N . . . M−1 correlation values an interference cancellation is performed according to:

COR

_

i

=

COR

i

-

∑

m

=

0

N

-

1

⁢

COR

_

m

⁢

RCC

i

,

m

⁢

⁢

i

=

N

⁢

⁢

…

⁢

⁢

M

-

1

wherein M is the maximum number of cell-specific correlation values of the plurality of cell-specific correlation values.

11. The method according to claim 1 , wherein the reference sequence is provided by brute force evaluation or a while list.

12. The method according to claim 1 , wherein at least two further OFDM symbols are used for generating pairs of received cell-specific reference subcarriers.

13. The method according to claim 1 , wherein a channel estimation is performed using the plurality of cell-specific correlation values, and wherein a transmitted symbol is reconstructed and cancelled from the received cell-specific reference subcarriers.

14. A mobile device comprising

means for receiving a first OFDM symbol containing a first received cell-specific reference subcarrier;

means for extracting the first received cell-specific reference subcarrier of the first OFDM symbol;

means for receiving a second OFDM symbol containing a second received cell-specific reference subcarrier;

means for extracting the second received cell-specific reference subcarrier of the second OFDM symbol;

means for generating a pair of received subcarriers by computing a scalar product of the first received cell-specific reference subcarrier and a conjugate of the second received cell-specific reference subcarrier;

means for providing a reference sequence, the reference sequence containing pairs of reference subcarriers for multiple combinations of cell-IDs and length of cyclic prefix, wherein a pair of reference subcarriers is a scalar product of a first cell-specific reference subcarrier and the conjugate of a second cell-specific reference subcarrier;

means for correlating the pair of received subcarriers with each pair of reference subcarriers of the reference sequence to generate a plurality of cell-specific correlation values; and

means for determining the cell-ID of a strongest cell by searching for a highest correlation value within the plurality of cell-specific correlation values and assigning the cell-ID associated with the highest correlation value to the cell-ID of the strongest cell.