Method of establishing search window size for a mobile station in a cellular system

• US 6,445,728 B1
• Filed: 06/25/1999
• Issued: 09/03/2002
• Est. Priority Date: 06/25/1998
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Byun, Sung-il
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Ha, Dac V.
• Application Number:
  US09/344,584
• Time in Patent Office: 1,166 Days
• Field of Search: 375/142, 375/144, 375/148, 375/150, 375/343, 375/367, 370/320, 370/335, 370/342, 370/441, 370/515
• US Class Current: 375/142
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information

Abstract

A method of establishing a search window size for a mobile station in a cellular system is disclosed. For the mobile station searching for a pilot signal of base transceiver station (BTS), the information of maximum index being outputted from the mobile station is gathered, wherein the maximum index is an index number at which the strongest signal is detected within a predetermined window size. For the gathered maximum indexes, confidence level is established and mean value is calculated and then confidence interval is calculated for the gathered maximum indexes using the established confidence level and calculated mean value. A maximum offset of the search window to be applied to the present radio morphology of the cellular system is calculated from the calculated confidence interval and a search window to be applied to the present radio morphology is estimated by increasing the maximum offset by two times. Therefore, the present invention is applicable to the characteristic of the mobile station and radio morphology of the cellular system by estimating the search window using the search result data gathered from the mobile station.

Claims

1. A method of establishing a search window size for a mobile station in a cellular system having a present radio morphology, said mobile station being provided with communication services from a plurality of base transceiver stations (BTSs), each of said plurality of BTSs having an inherent pilot signal, said mobile station searching for said pilot signal at each searcher position having a constant time interval within a search window on a time-axis, said method comprising the steps of:

finding a correlation energy value at each searcher position by which a searcher of said mobile station searches for pilot signals received from said plurality of BTSs at each searcher position within a predetermined first search window and outputting a result of the searching;

gathering said result of the searching outputted from said searcher of said mobile station using a diagnostic monitor (DM) connected to said mobile station; and

estimating the size of a second search window to be applied to the present radio morphology based on the gathered result of the searching and applying the second search window size to said mobile station,

wherein said step of gathering said result of the searching repeatedly gathers a maximum index samples, said maximum index samples including information denoting the location of a particular searcher position from the center of the first search window, and wherein the particular searcher position has the highest correlation energy value within the first search window.

2. The method as recited in claim 1, wherein said step of estimating the size of said second search window and applying the second search window size to said mobile station comprises the steps of:

considering a distribution of the gathered maximum index samples to find a maximum allowable offest value from the maximum index samples from a center of said first search window; and

finding the second search window size by increasing the maximum allowable offset by two times and applying the second search window size to said mobile station.

3. The method as set forth in claim 2, wherein said step of considering a distribution of the gathered maximun index samples to find the maximum allowable offset comprises the steps of:

converting the distribution of the gathered maximum index samples to a log-normal distribution;

establishing an allowable confidence level value for the maximum index samples converted to the log-normal distribution;

finding a confidence interval for the maximum index samples from the established allowable confidence level value; and

finding the maximum allowable offset from the found confidence interval.

4. A method of establishing a search window size of a mobile station in a cellular system having a present radio morphology, said mobile station being provided with communication services from a plurality of base transceiver stations (BTSs), each of said plurality of BTSs having an inherent pilot signal, said mobile station searching for said pilot signal at each searcher position having a constant time interval within a search window on a time-axis, said method comprising the steps of:

finding a correlation energy value at each searcher position by which a searcher of said mobile station searches for pilot signals received from said plurality of BTSs at each searcher position within a predetermined first search window;

gathering maximum index samples from said searcher of said mobile station using a diagnostic monitor (DM) connected to the mobile station, said maximum index samples including information which denotes the location of a searcher position from a center of the first search window, the searcher position having the highest correlation energy value within the first search window;

establishing a confidence level value, p, for the gathered maximun index samples;

calculating a mean value, m, and a standard deviation, σ

, for the gathered maximum index samples;

calculating a confidence interval for the gathered maximum index samples using the established confidence level value, p, the calculated mean value, m and the standard deviation, σ

; and

estimating the size of a second search window to be applied to the present radio morphology using the calculated confidence interval and applying the estimated second search window size to said mobile station.

5. The method as recited in claim 4, wherein said step of calculating said confidence interval comprises the steps of:

converting a distribution of the gathered maximum index samples to a normalized log-normal distribution;

finding a value of k satisfying 1−

2Q(k)=p where Q(k) is a Q-function for any variable, k; and

determining an interval as said confidence interval according to the values of m, k and, σ

, said interval being greater than or equal to a value of m−

kσ and

being less than or equal to a value of m+kσ

.

6. The method as recited in claim 5, wherein said step of estimating the size of a second search window and applying the estimated second search window size to said mobile station comprising the steps of:

finding a maximum offset value from the maximum index samples from the center of said first search window according to the determined confidence interval; and

finding said second search window size by increasing the maximum offset value by two times.

7. The method as recited in claim 6, wherein said step of finding a maximum offset value determines a value of S′

as the maximum offset value, said value of S′

being determined by S′

=|m|+MAX(|m−

kσ

|,|m+kσ

|).