Cell search method in CDMA capable of carrying out a cell search processing at a high speed

• US 20050025087A1
• Filed: 08/04/2004
• Published: 02/03/2005
• Est. Priority Date: 09/14/1999
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Tamura, Koichi
• Granted Patent: US 7,330,447 B2
• Time in Patent Office: Days
• US Class Current: 370/320
• CPC Class Codes: H04W 36/32 by location or mobility data, e.g. speed data
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 52/0232 according to average transmission signal activity
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

On ending communication, a timer is started in order to watch a communication stop time interval. On staring the next communication, a timer value of the timer is watched. If the timer value is less than a communication stop time interval threshold value, a cell search processing is carried out by using a cell search result on previous communication. By monitoring a communication stop time interval and by using a previous cell search result in the manner described above, a cell search circuit has an important function which realizes a high-speed cell search in the same sector (the same cell) on continuous communications and decreasing of a consumed power.

Claims

1. A cell search circuit for use in a code division multiple access (CDMA) system, comprising:

delay profile calculating means for, in a normal state, generating, by using known signal replicas for N codes, N delay profiles from a in-phase component signal and a quadrature component signal of a perch channel that are orthogonal detected and modulated, where N represents a positive integer which is not less than two, said delay profile calculating means producing a delay profile signal indicative of said N delay profiles;

spreading code and spreading timing detecting means, connected to said delay profile calculating means, for detecting, in response to said delay profile signal, a using spreading code and a using spreading timing by detecting a peak of power values in said delay profiles to produce a spreading code and spreading timing detected signal indicative of the using spreading code and the using spreading timing;

received data processing means, connected to said spreading code and spreading timing detecting means, for carrying out a demodulating processing on the in-phase component signal and the quadrature component signal to produce a demodulated output signal;

spreading code and spreading timing memory means, connected to said spreading code and spreading timing detecting means, for storing information of the using spreading code and the using spreading timing represented by said spreading code and spreading timing detected signal therein, said spreading code and spreading timing memory means producing a spreading code and spreading timing stored signal;

a timer for counting an elapsed time interval from an end of communication, said timer producing a timer value indicative of said elapsed time interval; and

known signal replica generating means connected to said timer, said spreading code and spreading timing detecting means, said spreading code and spreading timing memory means, and said delay profile calculating means, said known signal replica generating means supplying said known signal replicas for N codes to said delay profile calculating means to make a normal cell search processing carry out when said timer value is not less than a communication stop time interval threshold value on starting of re-communication, said known signal replica generating means making said delay profile calculating means generate a delay profile near to the spreading timing on a previous communication by using only one spreading code stored in said spreading code and spreading timing memory means when said timer value is less than the communication stop time interval threshold value on staring of the re-communication.

2. A cell search circuit for use in a code division multiple access (CDMA) system, comprising:

delay profile calculating means for, in a normal state, generating, by using known signal replicas for N codes, N delay profiles from a in-phase component signal and a quadrature component signal of a perch channel that are orthogonal detected and modulated, where N represents a positive integer which is not less than two, said delay profile calculating means producing a delay profile signal indicative of said N delay profiles;

spreading code and spreading timing detecting means, connected to said delay profile calculating means, for detecting, in response to said delay profile signal, a using spreading code and a using spreading timing by detecting a peak of power values in said delay profiles to produce a spreading code and spreading timing detected signal indicative of the using spreading code and the using spreading timing;

received data processing means, connected to said spreading code and spreading timing detecting means, for carrying out a demodulating processing on the in-phase component signal and the quadrature component signal to produce a demodulated output signal;

spreading code and spreading timing memory means, connected to said spreading code and spreading timing detecting means, for storing information of the using spreading code and the using spreading timing represented by said spreading code and spreading timing detected signal therein, said spreading code and spreading timing memory means producing a spreading code and spreading timing stored signal;

a timer for counting an elapsed time interval from an end of communication, said timer producing a timer value indicative of said elapsed time interval;

spreading timing controlling means, connected to said spreading code and spreading timing memory means, for generating spreading timings in consideration of the spreading timing stored in said spreading code and spreading timing memory means and a timing offset between sectors; and

known signal replica generating means connected to said timer, said spreading code and spreading timing detecting means, said spreading code and spreading timing memory means, and said delay profile calculating means, said known signal replica generating means making said delay profile calculating means generate a delay profile only near to the spreading timing stored in said spreading code and spreading timing memory means when said timer value is less than a first communication stop time interval threshold value on staring of a re-communication, said known signal replica generating means making said delay profile calculating means carry out a cell search processing near to the spreading timings generated by said spreading timing controlling means when said timer value is not less than said first communication stop time interval threshold value and is less than a second communication stop time interval threshold value on starting of the re-communication, said known signal replica generating means supplying said known signal replicas for N codes to said delay profile calculating means to make a normal cell search processing carry out when said timer value is not less than said second communication stop time interval threshold value on starting of the re-communication.

3. A cell search circuit for use in a code division multiple access (CDMA) system, comprising:

delay profile calculating means for, in a normal state, generating, by using known signal replicas for N codes, N delay profiles from a in-phase component signal and a quadrature component signal of a perch channel that are orthogonal detected and modulated, where N represents a positive integer which is not less than two, said delay profile calculating means producing a delay profile signal indicative of said N delay profiles;

spreading code and spreading timing detecting means, connected to said delay profile calculating means, for detecting, in response to said delay profile signal, a using spreading code and a using spreading timing by detecting a peak of power values in said delay profiles to produce a spreading code and spreading timing detected signal indicative of the using spreading code and the using spreading timing;

received data processing means, connected to said spreading code and spreading timing detecting means, for carrying out a demodulating processing on the in-phase component signal and the quadrature component signal to produce a demodulated output signal;

spreading code and spreading timing memory means, connected to said spreading code and spreading timing detecting means, for storing information of the using spreading code and the using spreading timing represented by said spreading code and spreading timing detected signal therein, said spreading code and spreading timing memory means producing a spreading code and spreading timing stored signal;

a timer for counting an elapsed time interval from an end of communication, said timer producing a timer value indicative of said elapsed time interval;

spreading timing controlling means, connected to said spreading code and spreading timing memory means, for generating spreading timings in consideration of the spreading timing stored in said spreading code and spreading timing memory means and a timing offset between sectors; and

known signal replica generating means connected to said timer, said spreading code and spreading timing detecting means, said spreading code and spreading timing memory means, and said delay profile calculating means, said known signal replica generating means making said delay profile calculating means carry out a cell search processing near to the spreading timings generated by said spreading timing controlling means when said timer value is not less than a communication stop time interval threshold value on starting of re-communication, said known signal replica generating means supplying said known signal replicas for N codes to said delay profile calculating means to make a normal cell search processing carry out when said timer value is not less than said communication stop time interval threshold value on starting of the re-communication.

4. A cell search circuit for use in a code division multiple access (CDMA) system, comprising:

a delay profile calculating circuit for, in a normal state, generating, by using known signal replicas for N codes, N delay profiles from a in-phase component signal and a quadrature component signal of a perch channel that are orthogonal detected and modulated, where N represents a positive integer which is not less than two, said delay profile calculating circuit producing a delay profile signal indicative of said N delay profiles;

a spreading code and spreading timing detecting circuit, connected to said delay profile calculating circuit, for detecting, in response to said delay profile signal, a using spreading code and a using spreading timing by detecting a peak of power values in said delay profiles to produce a spreading code and spreading timing detected signal indicative of the using spreading code and the using spreading timing;

a received data processing circuit, connected to said spreading code and spreading timing detecting circuit, for carrying out a demodulating processing on the in-phase component signal and the quadrature component signal to produce a demodulated output signal;

a spreading code and spreading timing memory circuit, connected to said spreading code and spreading timing detecting circuit, for storing information of the using spreading code and the using spreading timing represented by said spreading code and spreading timing detected signal therein, said spreading code and spreading timing memory circuit producing a spreading code and spreading timing stored signal;

a timer for counting an elapsed time interval from an end of communication, said timer producing a timer value indicative of said elapsed time interval; and

a known signal replica generating circuit connected to said timer, said spreading code and spreading timing detecting circuit, said spreading code and spreading timing memory circuit, and said delay profile calculating circuit, said known signal replica generating circuit supplying said known signal replicas for N codes to said delay profile calculating circuit to make a normal cell search processing carry out when said timer value is not less than a communication stop time interval threshold value on starting of re-communication, said known signal replica generating circuit making said delay profile calculating circuit generate a delay profile near to the spreading timing on a previous communication by using only one spreading code stored in said spreading code and spreading timing memory circuit when said timer value is less than the communication stop time interval threshold value on staring of the re-communication.

5. A cell search circuit for use in a code division multiple access (CDMA) system, comprising:

a delay profile calculating circuit for, in a normal state, generating, by using known signal replicas for N codes, N delay profiles from a in-phase component signal and a quadrature component signal of a perch channel that are orthogonal detected and modulated, where N represents a positive integer which is not less than two, said delay profile calculating circuit producing a delay profile signal indicative of said N delay profiles;

a spreading code and spreading timing detecting circuit, connected to said delay profile calculating circuit, for detecting, in response to said delay profile signal, a using spreading code and a using spreading timing by detecting a peak of power values in said delay profiles to produce a spreading code and spreading timing detected signal indicative of the using spreading code and the using spreading timing;

a received data processing circuit, connected to said spreading code and spreading timing detecting circuit, for carrying out a demodulating processing on the in-phase component signal and the quadrature component signal to produce a demodulated output signal;

a spreading code and spreading timing memory circuit, connected to said spreading code and spreading timing detecting circuit, for storing information of the using spreading code and the using spreading timing represented by said spreading code and spreading timing detected signal therein, said spreading code and spreading timing memory circuit producing a spreading code and spreading timing stored signal;

a timer for counting an elapsed time interval from an end of communication, said timer producing a timer value indicative of said elapsed time interval;

a spreading timing controlling circuit, connected to said spreading code and spreading timing memory circuit, for generating spreading timings in consideration of the spreading timing stored in said spreading code and spreading timing memory circuit and a timing offset between sectors; and

a known signal replica generating circuit connected to said timer, said spreading code and spreading timing detecting circuit, said spreading code and spreading timing memory circuit, and said delay profile calculating circuit, said known signal replica generating circuit making said delay profile calculating circuit generate a delay profile only near to the spreading timing stored in said spreading code and spreading timing memory circuit when said timer value is less than a first communication stop time interval threshold value on staring of a re-communication, said known signal replica generating circuit making said delay profile calculating circuit carry out a cell search processing near to the spreading timings generated by said spreading timing controlling circuit when said timer value is not less than said first communication stop time interval threshold value and is less than a second communication stop time interval threshold value on starting of the re-communication, said known signal replica generating circuit supplying said known signal replicas for N codes to said delay profile calculating circuit to make a normal cell search processing carry out when said timer value is not less than said second communication stop time interval threshold value on starting of the re-communication.

6. A cell search circuit for use in a code division multiple access (CDMA) system, comprising:

a delay profile calculating circuit for, in a normal state, generating, by using known signal replicas for N codes, N delay profiles from a in-phase component signal and a quadrature component signal of a perch channel that are orthogonal detected and modulated, where N represents a positive integer which is not less than two, said delay profile calculating circuit producing a delay profile signal indicative of said N delay profiles;

a spreading code and spreading timing detecting circuit, connected to said delay profile calculating circuit, for detecting, in response to said delay profile signal, a using spreading code and a using spreading timing by detecting a peak of power values in said delay profiles to produce a spreading code and spreading timing detected signal indicative of the using spreading code and the using spreading timing;

a received data processing circuit, connected to said spreading code and spreading timing detecting circuit, for carrying out a demodulating processing on the in-phase component signal and the quadrature component signal to produce a demodulated output signal;

a spreading code and spreading timing memory circuit, connected to said spreading code and spreading timing detecting circuit, for storing information of the using spreading code and the using spreading timing represented by said spreading code and spreading timing detected signal therein, said spreading code and spreading timing memory circuit producing a spreading code and spreading timing stored signal;

a timer for counting an elapsed time interval from an end of communication, said timer producing a timer value indicative of said elapsed time interval;

a spreading timing controlling circuit, connected to said spreading code and spreading timing memory circuit, for generating spreading timings in consideration of the spreading timing stored in said spreading code and spreading timing memory circuit and a timing offset between sectors; and

a known signal replica generating circuit connected to said timer, said spreading code and spreading timing detecting circuit, said spreading code and spreading timing memory circuit, and said delay profile calculating circuit, said known signal replica generating circuit making said delay profile calculating circuit carry out a cell search processing near to the spreading timings generated by said spreading timing controlling circuit when said timer value is not less than a communication stop time interval threshold value on starting of re-communication, said known signal replica generating circuit supplying said known signal replicas for N codes to said delay profile calculating circuit to make a normal cell search processing carry out when said timer value is not less than said communication stop time interval threshold value on starting of the re-communication.