Transmitting/receiving apparatus and method for cell search in a broadband wireless communications system

• US 20070041348A1
• Filed: 07/26/2006
• Published: 02/22/2007
• Est. Priority Date: 08/19/2005
• Status: Abandoned Application

• Current Assignee: Industry Academic Cooperation Foundation, Samsung Electronics Co. Ltd.
• Original Assignee: Industry-Academic Cooperation Foundation Yonsei University, Samsung Electronics Co. Ltd.
• Inventors: Hong, Daesik, Yu, Hyun-Kyu, Kim, Eung-Sun, Lee, Jong-Hyeuk, Cho, Myeon-Kyun, Kwun, Jong-Hyung
• Application Number:
  US11/493,449
• Publication Number:
  US 20070041348A1
• Time in Patent Office: Days
• US Class Current: 370/335
• CPC Class Codes: H04B 1/70735 Code identification H04B1/7083 takes precedence
• CPC Class Codes: H04J 11/0069 Cell search, i.e. determining cell identity [cell-ID] design of multiplexing codes H04J13/00; processing access restriction or access information H04W48/16; discovery of network devices for network data management H04W8/005; sounding signals for channel estimation H04L25/0226; structure of reference signals in multicarrier modulation systems H04L27/2613; frame, time or carrier synchronisation in multicarrier modulation systems H04L27/2655
• CPC Class Codes: H04L 25/03866 using scrambling
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 5/0017 in which a distinct code is applied, as a temporal sequence, to each frequency
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver

Abstract

Disclosed is transmitting/receiving apparatus and method for efficient cell search in a broadband wireless communication system using multiple carriers. The apparatus includes a BS generating an SCH signal by mapping predetermined symbols to predetermined subcarriers according to a code group to which the BS belongs, code-multiplexing a TCH signal and a pilot channel signal mapped to a predetermined time-frequency area and scrambling the code-multiplexed signal with a predetermined scrambling code identifying the BS along a time axis first, time-multiplexing the SCH signal with the scrambled signal, OFDM-modulating the time-multiplexed signal, and transmitting the OFDM-modulated signal.

Claims

1. A transmitting apparatus in a wireless communication system, comprising:

a synchronization channel (SCH) generator for generating an SCH signal by mapping predetermined symbols to predetermined subcarriers according to a code group to which the transmitting apparatus belongs;

a traffic channel (TCH) generator for generating a TCH signal;

a selector for selecting the SCH signal during a preamble period and selecting the TCH signal during a TCH period; and

a transmitter for orthogonal frequency division multiplexing (OFDM)-modulating a signal received from the selector and transmitting the OFDM-modulated signal to a receiving apparatus.

2. The transmitting apparatus of claim 1, wherein the TCH generator comprises:

an encoder for encoding transmission data;

a modulator for modulating coded data received from the encoder; and

a spreader for spreading modulated data received from the modulator with a channelization code.

3. The transmitting apparatus of claim 1, wherein the SCH includes two successive first and second same OFDM symbols.

4. The transmitting apparatus of claim 3, wherein the receiving apparatus acquires frame synchronization using the first and second OFDM symbols of the SCH and identifies a code group according to the positions of the subcarriers to which the predetermined symbols are mapped.

5. The transmitting apparatus of claim 1, wherein the predetermined symbols are mapped to the predetermined subcarriers spaced at a predetermined interval determined according to the number of code groups.

6. A transmitting apparatus in a wireless communication system, comprising:

a pilot channel generator for generating a pilot channel signal mapped to a predetermined time-frequency area;

a scrambler for scrambling the pilot channel signal with a predetermined scrambling code identifying the transmitting apparatus along a time axis first; and

a transmitter for orthogonal frequency division multiplexing (OFDM)-modulating the scrambled signal and transmitting the OFDM-modulated signal.

7. The transmitting apparatus of claim 6, wherein the pilot channel generator comprises:

a generator for generating predetermined modulation symbols; and

a spreader for spreading the modulation symbol with a predetermined spreading code.

8. The transmitting apparatus of claim 6, wherein the pilot channel signal is code-multiplexed with a traffic channel signal, for transmission.

9. The transmitting apparatus of claim 6, wherein the scrambling code is a pseudo noise (PN) code.

10. The transmitting apparatus of claim 6, wherein a phase offset of the PN code is used to identify base station.

11. The transmitting apparatus of claim 9, wherein the scrambling code maintains PN code features in time and frequency.

12. A transmitting apparatus in a wireless communication system, comprising:

a synchronization channel (SCH) generator for generating an SCH signal by mapping predetermined symbols to predetermined subcarriers according to a code group to which the transmitting apparatus belongs;

a traffic channel (TCH) generator for generating a TCH signal mapped to a predetermined time-frequency area;

a pilot channel generator for generating a pilot channel signal;

an adder for adding the TCH signal and the pilot channel signal;

a scrambler for scrambling a signal received from the adder with a predetermined scrambling code along a time axis first;

a selector for selecting the SCH signal during a preamble period and selecting the scrambled signal during a TCH period; and

a transmitter for orthogonal frequency division multiplexing (OFDM)-modulating a signal received from the selector and transmitting the OFDM-modulated signal to a receiving apparatus.

13. The transmitting apparatus of claim 12, wherein the SCH includes two successive first and second same OFDM symbols.

14. The transmitting apparatus of claim 12, wherein the predetermined symbols are mapped to the subcarriers equidistantly spaced at a predetermined interval determined according to the number of code groups.

15. The transmitting apparatus of claim 12, wherein the pilot channel signal is code-multiplexed with the TCH signal, for transmission.

16. The transmitting apparatus of claim 12, wherein the scrambling code is a pseudo noise (PN) code.

17. The transmitting apparatus of claim 16, wherein the scrambling code maintains PN code features in time and frequency.

18. A receiving apparatus in a wireless communication system, comprising:

a symbol synchronization acquirer for acquiring orthogonal frequency division multiplexing (OFDM) symbol synchronization using a cyclic prefix (CP);

a code group acquirer for;

acquiring frame synchronization using two successive same OFDM symbols forming a synchronization channel (SCH), after the OFDM symbol synchronization acquisition; and

detecting a code group to which a base station belongs by detecting the positions of subcarriers to which predetermined modulation symbols are mapped on the SCH; and

a cell detector for;

acquiring a scrambling code identifying the base station by descrambling a pilot channel signal mapped to a predetermined time-frequency area with a predetermined scrambling code for base station identification, determined by the detected code group along a time axis first, after the code group detection.

19. The receiving apparatus of claim 18, wherein the code group acquirer comprises:

a group distributor for extracting subcarrier values for each code group from a fast Fourier transform (FFT) signal and outputting the subcarrier values to a predetermined group correlator;

a plurality of group correlators for correlating subcarrier values received from the group distributor on a two OFDM symbol basis; and

a decider for detecting a maximum value from correlations received from the group correlators and deciding a number of a group correlator having the maximum value as a number of the code group of the base station.

20. The receiving apparatus of claim 19, further comprising a code group corrector for estimating a frequency offset by a correlation corresponding to the maximum value by an exponential function and correcting the code group number using the estimated frequency offset.

21. The receiving apparatus of claim 18, wherein the cell detector comprises:

a buffer for buffering subcarrier values after performing a fast Fourier transform (FFT);

a pilot channel recoverer for despreading the buffered subcarrier values with a spreading code used for a pilot channel, demodulating the despread pilot channel signal, and outputting pilot data;

a code generator for generating pseudo noise (PN) codes with different phase offsets for different code groups; and

a decider for descrambling the pilot data in the predetermined time-frequency area with the PN codes received from the code generator, detecting a peak, and identifying the base station using a PN code having the peak.

22. A transmitting method for a base station in a wireless communication system, comprising the steps of:

generating a synchronization channel (SCH) signal by mapping predetermined symbols to predetermined subcarriers according to a code group to which the base station belongs;

code-multiplexing a traffic channel (TCH) signal and a pilot channel signal, the TCH signal and pilot channel signal being mapped to a predetermined time-frequency area;

scrambling the code-multiplexed signal with a predetermined scrambling code identifying the base station along a time axis first;

time-multiplexing the SCH signal with the scrambled signal; and

orthogonal frequency division multiplexing (OFDM)-modulating the time-multiplexed signal and transmitting the OFDM-modulated signal to a receiver.

23. The transmitting method of claim 22, wherein the SCH includes two successive first and second same OFDM symbols.

24. The transmitting method of claim 22, wherein the predetermined symbols are mapped to the subcarriers equidistantly spaced at a predetermined interval determined according to the number of code groups.

25. The transmitting method of claim 22, wherein the receiver acquires frame synchronization using the first and second OFDM symbols of the SCH and identifies a code group according to the positions of the subcarriers to which the predetermined symbols are mapped.

26. The transmitting method of claim 22, wherein the scrambling code is a pseudo noise (PN) code.

27. The transmitting method of claim 26, wherein the scrambling code maintains PN code features in time and frequency.

28. A cell search method for a receiver in a wireless communication system, comprising the steps of:

acquiring orthogonal frequency division multiplexing (OFDM) symbol synchronization using a cyclic prefix (CP);

acquiring frame synchronization using two successive first and second same OFDM symbols forming a synchronization channel (SCH), after the OFDM symbol synchronization acquisition, and detecting a code group to which a base station belongs by detecting the positions of subcarriers to which predetermined modulation symbols are mapped on the SCH; and

acquiring a scrambling code identifying the base station by descrambling a pilot channel signal mapped to a predetermined time-frequency area with a predetermined scrambling code for base station identification, determined by the detected code group along a time axis first, after the code group detection.

29. The cell search method of claim 28, wherein the code group detection step comprises the steps of:

extracting subcarrier values for each code group from a fast Fourier transform (FFT) signal;

correlating the extracted subcarrier values on a two OFDM symbol basis, for each of the code groups; and

detecting a maximum value from correlations received from the group correlators; and

deciding the number of a group correlator having the maximum value as the number of the code group of the base station.

30. The cell search method of claim 28, wherein the scrambling code acquisition step comprises the steps of:

recovering pilot data by despreading subcarrier values after performing an FFT with a spreading code used for a pilot channel and demodulating the despread pilot channel signal;

generating pseudo noise (PN) codes with different phase offsets for different code groups;

descrambling the pilot data in the predetermined time-frequency area with the PN codes received from the code generator and detecting a peak; and

identifying the base station using a PN code having the peak.