Cell searcher and cell searching method

• US 20040043746A1
• Filed: 03/27/2003
• Published: 03/04/2004
• Est. Priority Date: 08/07/2001
• Status: Active Grant

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Hiramatsu, Katsuhiko
• Granted Patent: US 7,013,135 B2
• Time in Patent Office: Days
• US Class Current: 455/334
• 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 apparatus, comprising:

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

a peak detector that detects a first peak timing based on a result of the correlation calculation in said first correlator;

a second correlator that performs the correlation calculation of a second synchronization channel on a predetermined time interval;

a second synchronization channel identifier that compares results of the correlation calculation in said second correlator at a plurality of timings and identifies the second synchronization channel from the timings that give largest correlation calculation results; and

a timing controller that gives instruction to said second synchronization channel identifier on the plurality of timings to perform the correlation calculation.

2. The cell search apparatus according to claim 1,

wherein the second channel identifier detects a second peak timing, said second peak timing being the timing that gives the largest correlation calculation result among the plurality of timings;

and

wherein, based on the first peak timing and the second peak timing, the timing controller sets the plurality of timings that said second synchronization channel identifier is instructed on.

3. The cell search apparatus according to claim 1, wherein the second timing controller instructs the second channel identifier on the plurality of timings from within a predetermined time range centering around a standard timing that is one frame time after the first or the second peak timing.

4. The cell search apparatus according to claim 1, wherein the second synchronization channel identifier detects a second peak timing through comparison of sums of correlation values of a plurality of the second synchronization channels identified at the timings instructed by the timing controller.

5. The cell search apparatus according to claim 1, 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 in such a way that corrects said frequency difference.

6. 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 based on a result of the correlation calculation in said first correlator;

a second correlator that performs the correlation calculation of a second synchronization channel on a predetermined time interval;

a second synchronization channel identifier that compares results of the correlation calculation in said second correlator at a plurality of timings and identifies the second synchronization channel from the timings that give largest correlation calculation results; and

a timing controller that gives instruction to said second synchronization channel identifier on the plurality of timings to perform the correlation calculation.

7. A cell search method comprising:

a first step, wherein a correlation calculation of a first synchronization channel is performed so as to detect a first peak timing that gives a largest correlation value as a slot timing;

a second step, wherein correlation calculations of all second synchronization channels are performed and a code group assigned to a cell where an apparatus implementing the method lies is identified, so as to detect a timing of a frame top; and

a third step, wherein the correlation calculation of a mid-amble belonging to the identified code group is performed, so as to identify the mid-amble and a scrambling code assigned to the cell where the apparatus lies,

wherein, in the second step, results of the correlation calculations at a plurality of timings are compared so as to identify the second synchronization channels from those corresponding to the timings that give largest correlation calculation results.

8. A cell search method, wherein the third step is performed such that a difference of a frame time relative to the frame time measured in a base station apparatus of a communication partner is calculated and converted to a frequency difference, and an oscillator frequency in such a way that said frequency difference is corrected.