Code division multiple access mobile communication system

• US 8,837,436 B2
• Filed: 11/20/2012
• Issued: 09/16/2014
• Est. Priority Date: 05/13/1998
• Status: Expired due to Fees

• Current Assignee: FIPA Frohwitter International Property AG
• Original Assignee: FIPA Frohwitter International Property AG
• Inventors: Suzuki, May, Doi, Nobukazu, Yano, Takashi
• Primary Examiner(s): Gidado, Rasheed
• Application Number:
  US13/681,458
• Publication Number:
  US 20130077602A1
• Time in Patent Office: 665 Days
• Field of Search: 370/335, 370/342
• US Class Current: 370/335
• 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 mobile terminal for use in a code division multiple access (CDMA) mobile communication system, in which a base station transmits a control signal formed such that a long code assigned to said base station and a short code are mapped in a first section of said control signal and a first short period code and a second short period code are mapped in a second, long code masked section of said control signal, said mobile terminal comprising:

a timing synchronizer to receive a baseband signal obtained by frequency down-converting a radio frequency (RF) signal and calculate a correlation value for said baseband signal by using said first short period code to establish slot timing synchronization, wherein a symbol length of said first short period code has a smaller value than a symbol length of said short code, and

a group code detector to detect said second short period code by generating candidate short period codes and for each generated candidate short period code determining a correlation value of that candidate short period code and said second, long code masked section and determining the candidate short code for which the correlation has a maximum value, the second short period code corresponding to a classification of the long code mapped in said first section.

2. A mobile terminal for use in a code division multiple access (CDMA) mobile communication system, the mobile terminal comprising:

an antenna which receives a received signal; and

a cell search circuit which receives, as an input signal, a baseband control channel signal included in the received signal, the control channel signal including a data symbol section of one slot spread by a short code and a long code and a long code masked section of said one slot, a first search code and a second search code being provided in said long code masked section of said one slot,

wherein the cell search circuit includes a timing synchronizer, a second search code detector and a long code detector,

the timing synchronizer including a first search code generator arranged to generate the first search code and a correlator for determining a correlation value between said long code masked section of said received signal and the generated first search code,

the second search code detector arranged to generate successive candidate second search codes and to determining which of the candidate second search codes corresponds to the second search code of the base station by analyzing correlation values of the candidate second search code and the received signal within the long code masked symbol section, and

the long code detector including a code generator arranged to generate candidate long codes and a code generator arranged to generate the first short code and to determine which of the candidate long codes corresponds to the long code by analyzing correlation values of the candidate long code multiplied by the first short code and the received signal within the data symbol section, and

wherein one of said first search code and said second search code has a length shorter than the short code and the other of said first search code and said second search code has a length equal to the short code.

3. The mobile terminal according to claim 2, wherein the terminal is arranged to detect the long code by searching using all long codes belonging to a group associated with the detected second search code.