Method and apparatus for transmitting synchronization signals in an OFDM based cellular communications system

1. A method for communication, the method comprising:

identifying a primary synchronization sequence;

identifying a secondary synchronization sequence and another secondary synchronization sequence that is different from the secondary synchronization sequence, and the secondary synchronization sequence and the another secondary synchronization sequence are associated with a cell identifier;

transmitting the primary synchronization sequence in center subcarriers in a first Orthogonal Frequency Division Multiplexing (OFDM) symbol;

transmitting the secondary synchronization sequence in the center subcarriers in a second OFDM symbol, the second OFDM symbol being adjacent to the first OFDM symbol;

transmitting the primary synchronization sequence in a third OFDM symbol; and

transmitting the another secondary synchronization sequence in a fourth OFDM symbol,

wherein one of the first and second OFDM symbols in the frame is adjacent to one of the third and fourth OFDM symbols in the frame, and

wherein the center subcarriers are part of a system bandwidth, a part of the center subcarriers in the first OFDM symbol is not used for transmission of the primary synchronization sequence, and a part of the center subcarriers in the second OFDM symbol is not used for transmission of the secondary synchronization sequence.

2. The method of claim 1 , wherein at least one subcarrier other than the center subcarriers is used for signal transmission other than the primary synchronization sequence and the secondary synchronization sequence.

3. The method of claim 1 , wherein the secondary synchronization sequence is associated with a cell specific scrambling sequence.

4. An apparatus for communication, the apparatus comprising:

a generator configured to identify a primary synchronization sequence, and to identify a secondary synchronization sequence and another secondary synchronization sequence that is different from the secondary synchronization sequence, and the secondary synchronization sequence and the another secondary synchronization sequence are associated with a cell identifier; and

a transmitter configured to transmit the primary synchronization sequence in center subcarriers in a first Orthogonal Frequency Division Multiplexing (OFDM) symbol, to transmit the secondary synchronization sequence in the center subcarriers in a second OFDM symbol, the second OFDM symbol being adjacent to the first OFDM symbol, to transmit the primary synchronization sequence in a third OFDM symbol, and to transmit the another secondary synchronization sequence in a fourth OFDM symbol,

wherein one of the first and second OFDM symbols in the frame is adjacent to one of the third and fourth OFDM symbols in the frame, and

wherein the center subcarriers are part of a system bandwidth, a part of the center subcarriers in the first OFDM symbol is not used for transmission of the primary synchronization sequence, and a part of the center subcarriers in the second OFDM symbol is not used for transmission of the secondary synchronization sequence.

5. The apparatus of claim 4 , wherein at least one subcarrier other than the center subcarriers is used for signal transmission other than the primary synchronization sequence and the secondary synchronization sequence.

6. The apparatus of claim 4 , wherein the secondary synchronization sequence is associated with a cell specific scrambling sequence.

7. A method for communication, the method comprising:

receiving a first Orthogonal Frequency Division Multiplexing (OFDM) symbol of a frame, the first OFDM symbol including a primary synchronization sequence;

receiving a second OFDM symbol in the frame, the second OFDM symbol including a secondary synchronization sequence associated with a cell identifier;

receiving a third OFDM symbol in the frame, the third OFDM symbol including the primary synchronization sequence;

receiving a fourth OFDM symbol in the frame, the fourth OFDM symbol including another secondary synchronization sequence, which is different from the secondary synchronization sequence and associated with a cell identifier, and

performing the cell search based on at least one of the received first OFDM symbol and the received second OFDM symbol and at least one of the received third OFDM symbol and the received fourth OFDM symbol,

wherein the primary synchronization sequence is received in center subcarriers in the first OFDM symbol and the secondary synchronization sequence is received in the center subcarriers in a second OFDM symbol, the second OFDM symbol being adjacent to the first OFDM symbol,

wherein the center subcarriers are part of a system bandwidth, a part of the center subcarriers in the first OFDM symbol is not used for transmission of the primary synchronization sequence, and a part of the center subcarriers in the second OFDM symbol is not used for transmission of the secondary synchronization sequence,

wherein the primary synchronization sequence is received in the center subcarriers in the third OFDM symbol and the another secondary synchronization sequence is received in the center subcarriers in the fourth OFDM symbol, and

wherein one of the first and second OFDM symbols in the frame is adjacent to one of the third and fourth OFDM symbols in the frame.

8. The method of claim 7 , wherein at least one subcarrier other than the center subcarriers is used for signal reception other than the primary synchronization sequence and the secondary synchronization sequence.

9. The method of claim 7 , wherein the secondary synchronization sequence is associated with a cell specific scrambling sequence.

10. An apparatus for communication, the apparatus comprising:

a receiver configured to receive a first Orthogonal Frequency Division Multiplexing (OFDM)symbol of a frame, the first OFDM symbol including a primary synchronization sequence, to receive a second OFDM symbol in the frame, the second OFDM symbol including a secondary synchronization sequence associated with a cell identifier, to receive a third OFDM symbol in the frame, the third OFDM symbol including the primary synchronization sequence, and to receive a fourth OFDM symbol in the frame, the fourth OFDM symbol including another secondary synchronization sequence, which is different from the secondary synchronization sequence, and

a controller configured to perform the cell search based on at least one of the received first OFDM symbol and the received second OFDM symbol and at least one of the received third OFDM symbol and the received fourth OFDM symbol,

wherein the primary synchronization sequence is received in center subcarriers in the first OFDM symbol and the secondary synchronization sequence is received in the center subcarriers in a second OFDM symbol, the second OFDM symbol being adjacent to the first OFDM symbol,

wherein the center subcarriers are part of a system bandwidth, a part of the center subcarriers in the first OFDM symbol is not used for transmission of the primary synchronization sequence, and a part of the center subcarriers in the second OFDM symbol is not used for transmission of the secondary synchronization sequence,

wherein the primary synchronization sequence is received in the center subcarriers in the third OFDM symbol and the another secondary synchronization sequence is received in the center subcarriers in the fourth OFDM symbol, and

wherein one of the first and second OFDM symbols in the frame is adjacent to one of the third and fourth symbols in the frame.

11. The apparatus of claim 10 , wherein at least one subcarrier other than the center subcarriers is used for signal reception other than the primary synchronization sequence and the secondary synchronization sequence.

12. The apparatus of claim 10 , wherein the secondary synchronization sequence is associated with a cell specific scrambling sequence.