Code division multiple access mobile communication system

• US 9,577,745 B2
• Filed: 08/12/2014
• Issued: 02/21/2017
• Est. Priority Date: 05/13/1998
• Status: Expired due to Fees

• Current Assignee: FIPA Frohwitter Intellectual Property AG
• Original Assignee: FIPA Frohwitter Intellectual Property AG
• Inventors: Suzuki, May, Doi, Nobukazu, Yano, Takashi
• Primary Examiner(s): Gidado, Rasheed
• Application Number:
  US14/457,503
• Publication Number:
  US 20140355571A1
• Time in Patent Office: 924 Days
• US Class Current: 1/1
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 1/708 Parallel implementation
• CPC Class Codes: H04B 7/2628 using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA] H04B7/2618 takes precedence
• CPC Class Codes: H04B 7/2668 Arrangements for Wireless Code-Division Multiple Access [CDMA] System Synchronisation, for code acquisition H04B1/7075, for code tracking H04B1/7085
• CPC Class Codes: H04W 72/23 in the downlink direction of a wireless link, i.e. towards a terminal

Abstract

In a mobile communication system using a code division multiple access (CDMA) method, spreading code detection and frame/slot timing synchronization (cell search) is conducted by using a long code masked symbol. The spreading factor of the long code masked symbol is set to a value lower than spreading factors of other ordinary symbols. As a result, it becomes possible to reduce the circuit scale and power dissipation of the mobile terminal and raise the speed of cell search.

Claims

1. A code division multiple access mobile communication system terminal, the terminal comprising:

a signal receiving antenna producing a received signal;

a cell searcher including a timing synchronization sub-part, a short code detection sub-part, and a long code detection sub-part;

a data signal receiver; and

a data signal transmitter,

wherein;

the timing synchronization sub-part comprising a first short code generator and a correlator, the timing synchronization sub-part being arranged to generate a first short code, to perform a correlation of a plurality of time instances of the generated first short code with the received signal in a long code masked symbol section of the received signal, and to identify a time instance having a maximum correlation, indicating a slot timing,

the short code detection sub-part comprising a second short code generator and a correlator, the short code detection sub-part being arranged to generate candidate second short codes, to perform a correlation of a stored version of the long code masked symbol section of the received signal with the candidate second short codes, and to identify a particular second short code of the received signal,

the long code detection sub-part comprising a long code generator, a multiplier and a correlator, the long code detection sub-part being arranged to generate candidate long codes, to multiply the candidate long codes by a third short code to generate code products, and to perform a correlation of each of the code products with the received signal to detect a long code of the received signal, and

the first and second short codes each have a length shorter than the third short code and the long code.

2. The terminal according to claim 1, wherein the correlator of the timing synchronization sub-part is a matched filter responsive to an input first short code for setting coefficients of the matched filter.

3. The terminal according to claim 1, wherein the timing synchronization sub-part further includes an accumulator and a peak detector, the timing synchronization sub-part being arranged to detect the slot timing by identifying a maximum accumulated correlation value.

4. The terminal according to claim 1, wherein the cell searcher is implemented within a digital signal processor.

5. The terminal according to claim 4, wherein the digital signal processor specifies the candidate short second codes are generated one after another.

6. The terminal according to claim 1, wherein the long code detection sub-part includes first and second long code detectors and where the long code detected by the first long code detector is passed to the second long code detector.

7. The terminal according to claim 6, wherein the identified second short code indicates a class of candidate long codes.

8. The terminal according to claim 7, wherein the long code detection sub-part is arranged to determine correlation values of differing long codes in parallel.

9. The terminal according to claim 8, wherein a probable long code is determined on the basis of a correlation value obtained over approximately ten symbols.

10. The terminal according to claim 1, wherein the first short code is a common short code that defines a mobile communication system of the terminal.

11. A method for cell searching in a terminal of a code division multiple access mobile communication system, the method comprising:

receiving a signal at an antenna to produce a received signal;

in a timing synchronization sub-part of a cell search circuit, generating a first short code, correlating a plurality of time instances of the generated first short code with the received signal in a long code masked symbol section of the received signal, and identifying a time instance having a maximum correlation, indicating a slot timing,

in a short code detection sub-part of the cell search circuit, generating candidate second short codes, correlating a stored version of the long code masked symbol section of the received signal with the candidate second short codes, and identifying a particular second short code of the received signal,

in a long code detection sub-part of the cell search circuit, generating candidate long codes, multiplying the candidate long codes by a third short code to generate code products, and correlating each of the code products with the received signal to detect a long code of the received signal,

wherein the first and second short codes each have a length shorter than the third short code and the long code.