Cell searcher and cell searching method

• US 7,013,135 B2
• Filed: 07/25/2002
• Issued: 03/14/2006
• Est. Priority Date: 08/07/2001
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Hiramatsu, Katsuhiko
• Primary Examiner(s): Deane, Jr., William J.
• Application Number:
  US10/381,697
• Publication Number:
  US 20040043746A1
• Time in Patent Office: 1,328 Days
• Field of Search: 455/423, 455/422.1, 455/456, 455/502, 455436-443, 455/500, 455/501, 455/456.1
• US Class Current: 455/423
• CPC Class Codes: H04B 1/70735 Code identification H04B1/7083 takes precedence
• CPC Class Codes: H04B 1/7083 Cell search, e.g. using a three-step approach
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects

Abstract

Peak detector 104 detects the first peak timing where the correlation value of the first synchronization channel is the greatest. SSCH identifier 108 identifies the second synchronization channels by adding the correlation values of the second synchronization channels at a number of timings, and detects the timing where the sum of the correlation values of the identified second synchronization channels is the largest as a second peak timing. Based on the first and second peak timings, timing controller 105 instructs SSCH identifier 108 on the timing to perform correlation calculation. Likewise, based on the first and second peak timings, frequency corrector 110 calculates the error in a frame time measured by a base station, and converts this into a frequency difference, and changes the frequency of an oscillator in RF receiver 102 in such a way that corrects the frequency difference. By this means second synchronization channels and mid-ambles are accurately identified even when a base station gives a different measurement of a frame time.

Claims

1. A cell search method of a wireless communication terminal apparatus, said method comprising:

(a) performing a correlation calculation of a first synchronization channel whereupon a first peak timing that gives a largest correlation value is detected as a slot timing;

(b) performing correlation calculations of all second synchronization channels so as to identify a code group assigned to a cell where the apparatus is located, and detect a timing of a frame top; and

(c) performing a correlation calculation of a mid-amble belonging to the identified code group, so as to identify the mid-amble and a scrambling code assigned to the cell where the apparatus is located;

wherein step (b) comprises;

identifying a second synchronization channel at an initial standard timing that is one frame time after the first peak timing;

detecting the timing where the correlation value of the identified second synchronization channel is the largest among a plurality of timings within a predetermined time range centering around the standard timing; and

setting a second and later standard timing at the timing that is one frame time after a most currently detected second peak timing, and repeating the second synchronization channel identification and second peak timing detection by new standard timings.

2. The cell search method according to claim 1, wherein step (c) performed after steps (a) and (b) comprises:

calculating a difference of a frame time measured by the apparatus implementing the cell search method relative to the frame time measured by a base station apparatus of a communication partner based on the first and second peak timings, and converting the difference to a frequency difference;

changing an oscillator frequency in such a way that corrects said frequency; and

identifying the mid-amble and the scrambling code assigned to the cell the apparatus is in.

9. The cell search method according to claim 1, wherein step (c) performed after steps (a) and (b) comprises:

calculating a difference of a frame time measured by the apparatus implementing the cell search method relative to the frame time measured by a base station apparatus of a communication partner based on the first and second peak timings, and converting the difference to a frequency difference;

changing an oscillator frequency in such a way that corrects said frequency difference; and

identifying the mid-amble and the scrambling code assigned to the cell in which the apparatus is located.

3. A cell search apparatus comprising:

a first correlator that performs a correlation calculation of a first synchronization channel;

a peak detector that detects a first peak timing where the first correlator gives a largest correlation calculation result;

a second correlator that performs said correlation calculation of all second synchronization channels;

a timing controller that sets an initial standard timing one frame time after the first peak timing and sets a plurality of timings within a predetermined time range around said initial standard timing; and

a second synchronization channel identifier that compares correlation calculation results in the second correlator at the initial standard timing and identifies the second synchronization channels, and detects a second peak timing among said plurality of timings set by the timing controller where the identified second synchronization channels give a largest correlation value,

wherein the timing controller sets a second and later standard timing one frame time after a most currently detected second peak timing.

4. The cell search apparatus according to claim 3, wherein the timing controller sets a standard timing, a timing a predetermined time before said standard timing, and a timing a predetermined time after said standard timing.

5. The cell search apparatus according to claim 3, wherein the second synchronization channel identifier identifies a plurality of second synchronization channels, adds correlation values of said plurality of second synchronization channels at each timing set by the timing controller, and detects the second peak timing at a timing that gives a largest sum of said correlation values.

6. The cell search apparatus according to claim 3, further comprising a frequency corrector that, with reference to the first and second peak timings, calculates a difference of a frame time measured by said cell search apparatus relative to the frame time measured by a base station apparatus of a communication partner, converts said difference to a frequency difference, and changes an oscillator frequency to correct said frequency difference.

7. A wireless communication terminal apparatus comprising a cell search apparatus, said cell search apparatus comprising:

a first correlator that performs a correlation calculation of a first synchronization channel;

a peak detector that detects a first peak timing where the first correlator gives a largest correlation calculation result;

a second correlator that performs said correlation calculation of all second synchronization channels;

a timing controller that sets an initial standard timing one frame time after the first peak timing and sets a plurality of timings within a predetermined time range around said initial standard timing; and

a second synchronization channel identifier that compares correlation calculation results in the second correlator at the initial standard timing and identifies the second synchronization channels, and detects a second peak timing among said plurality of timings set by the timing controller where the identified second synchronization channels give a largest correlation value,

wherein the timing controller sets a second and later standard timing one frame time after a most currently detected second peak timing.

8. A cell search method comprising:

(a) performing a correlation calculation of a first synchronization channel whereupon a first peak timing that gives a largest correlation value is detected as a slot timing;

(b) performing correlation calculations of all second synchronization channels so as to identify a code group assigned to a cell where the apparatus is in, and detect a timing of a frame top; and

(c) performing correlation calculation of a mid-able belonging to the identified code group, so as to identify the mid-amble and a scrambling code assigned to the cell where the apparatus is located;

wherein the step (b) comprises;

identifying a second synchronization channel at an initial standard timing that is one frame time after the first peak timing;

detecting the timing where the correlation value of the identified second synchronization channel is the largest among a plurality of timings within a predetermined timing centering around the standard timing; and

setting a second and later standard timing at the timing that is one frame time after a most currently detected second peak timing, and repeating the second synchronization channel identification and second peak timing detection by new standard timings.