Method and apparatus for cell search for W-CDMA with effect of clock offset
AssigneeAccton Technology Corporation
InventorsJan Shin Ho, Wern Ho Sheen
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Abstract
The invention discloses a cell search method for a CDMA system for a three-stage cell search procedure. The cell search method have the steps of matching incoming signals; over-sampling the incoming signals N times against a chip rate; down-sampling the incoming signals and outputting N over-samples (Y1(k), Y2(k), YN(k)) to N parallel signal paths; choosing randomly a sample of the N over-samples; and transmitting the sample chosen randomly from the N over-samples into a first stage process, a second stage process and a third stage process to accomplish a trial. The invention significantly reduces the effect of clock offset so as to accomplish fast cell search.
Claims28
A cell search method for a CDMA system for a three-stage cell search procedure, comprising the steps of:
- matching incoming signals;
- over-sampling the incoming signals N times against a chip rate;
- down-sampling the incoming signals and outputting N over-samples (Y1(k), Y2(k), YN(k)) to N parallel signal paths;
- choosing randomly a sample of the N over-samples;
- transmitting the sample chosen randomly from the N over-samples into a first stage process,
- a second stage process and a third stage process to accomplish a trial;
- achieving a slot synchronization of the incoming signal in the first stage process;
- achieving a code group and frame synchronization of the incoming signal in the second stage process;
- selecting a scrambling code of the incoming signal in the third stage process;
- and
- testing the scrambling code against a threshold η0 by a first verification;
- wherein if the threshold is not exceeded, then the trial is considered to be failure and a new trial will be restarted without penalty;
- or
- the selected scrambling code goes for a second verification unit;
- wherein if the scrambling code passes the second verification, then the trial succeeds, otherwise the a new trial will be restarted with a penalty time TP (ms) and an initial sampling point at a matched filter output is assumed to be random.
A cell search apparatus for a CDMA system for a three-stage cell search procedure, comprising:
- a chip matched filter, used for matching incoming signals;
- a sampling device connected to the chip matched filter, used for over-sampling the incoming signals by N times against a chip rate;
- a down-sample device connected to the sampling device, used for down-sampling the incoming signals and outputting N over-samples (Y1(k), Y2(k), YN(k)) N parallel signal paths;
- an incoming signal selector connected to the down-sample device, used for choosing randomly one of the N over-samples;
- and to go through the succeeding stages;
- a first stage detector connected to the incoming signal selector, used for achieving slot synchronization;
- a second stage detector connected to the incoming signal selector, used for achieving frame boundary and code group synchronization;
- a third stage detector connected to the incoming signal selector, used for achieving a scrambling code;
- and
- an identification unit connected to the third stage detector, used for determining a trial succeed or not, wherein the identification unit further comprises:
- a comparator connected to the third stage detector, used for testing the output of the third stage detector against a thresholdη0;
- a first decision device connected to the comparator, used for determining the scrambling code;
- wherein if the threshold is exceeded, then the selected scrambling code goes for a synchronization verification unit, otherwise the trial is considered to be failure, and a new trial will be restarted without penalty;
- and
- the synchronization verification unit connected to the first decision device, used for verifying the scrambling code;
- and
- a second decision device connected to the synchronization verification unit, used for determining the acceptance of the scrambling code;
- wherein if the scrambling code passes the second decision device, then the trial succeeds, otherwise the a new trial will be restarted with a penalty time TP (ms) and;
- an initial sampling point at the matched filter is assumed uniformly distributed.
Dependencies are inferred from the claim text.