Patent EP1487230A1 successfully refreshed from Google Patents.
EP1487230A1
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Method and apparatus for merging pilot neighbor lists in a mobile telephone system
Assignee: Qualcomm Inc
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Filing: 1998-02-13
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Granted: —
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Expires: 2018-02-13
Abstract
Abstract A method and apparatus for merging pilot neighbor lists to account for false indications of signal strength due to topography in a code division multiple access (CDMA) communication system. The merged list is arrived at by first measuring pilot signal strengths and phase delays received by the mobile station and reporting this information to the mobile telephone switching office (60). A neighbor list union is generated (60) as the union of all predetermined neighbor lists corresponding to said received pilot signals. Each member, or base station, in the neighbor list union is operated on by a weighting function (75) which takes into account how often each member is included in each received pilot's predetermined neighbor list and the signal strength of such pilots. The relative weights are then sorted (95) and the highest ranking members form a Neighbor List Update Message (105), up to a predetermined number of members.
Inventors
- 👤 Walid M. Hamdy
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 16:26
CPC Classifications
H; H04; H04W; H04W36/00; H04W36/0005; H04W36/0055; H04W36/0061
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
133 words
An apparatus for controlling handoff of a mobile station
from a first base station to a second base station by monitoring the strength
of pilot signals received by the mobile station from a plurality of base
stations including the first and second base stations, the apparatus
comprising: means for receiving data from the mobile station representing the
strength and phase of the pilot signals received by the mobile station and
identifying active and candidate base stations including the first and
second base stations; and means for determining a ranked list of neighboring base stations to
the mobile station, the ranked list depending on the strength of each pilot
signal received by the mobile station and the number of times that a base
station is found as a neighbor of each pilot signal received.
Claim 2
Dependent Claim
183 words
The apparatus of claim 1, wherein the means for determining (30) further
comprise: means for retrieving from a memory unit, a fixed, predetermined neighbor list
for each of said pilot signals that said mobile station is presently communicating with
and whose corresponding round trip delay time does not exceed a predetermined
threshold; means for generating the union of neighboring base stations from fixed,
predetermined neighbor lists; means for removing from said union any member of said union which is a
member of an Active or Candidate Set; means for identifying for each member of said union, said received pilot
signals which include said member in their respective fixed, predetermined neighbor
lists; means for calculating for each of said members, a relative signal strength
based upon the number and signal strength of said received pilot signals which
include said member in their respective fixed, predetermined neighbor lists; means for sorting said members based upon said relative signal strength; and means for selecting said members with the highest relative signal strengths to
be included in a Neighbor List Update Message provided to said mobile station.
Claim 3
Dependent Claim
103 words
The apparatus of claim 2 wherein the means for calculating relative signal
strength for each of said members operate in accordance with the equation: where Pj is equal to the signal strength of said received pilot j, f(Pj) is a function of
the signal strength of said received pilot j, RTDj is the round trip delay of said pilot j,
Wk is the relative signal strength of member k in said union, RTD_MAX is a pre-determined
maximum round trip delay threshold, and {j} is the set of received pilots
which include member k in their respective unique, predetermined list of neighboring
base stations.
Claim 4
Dependent Claim
40 words
The apparatus of claim 3 wherein the means for calculating the function f(Pj)
operate in accordance with the equation: f(Pj)=max(Pj-T_BASE,0); f(Pj)>0 where Pj is the signal strength of received pilot j and T.sub.-- BASE is a
predetermined minimum power threshold.
Claim 5
Dependent Claim
30 words
The apparatus of claim 3 wherein the means for calculating the function f(Pj)
operate in accordance with the equation: f(Pj)=10 (Pj/10) where Pj is the signal strength of pilot j.
Claim 6
Dependent Claim
54 words
The apparatus of claim 2 wherein the selecting means further comprise: means for removing from said union any of said members whose respective
relative signal strength is not greater than a predetermined minimal threshold; and means for removing from said union members with the lowest relative signal
strength, leaving a predetermined number of members.
Claim 7
Dependent Claim
17 words
The apparatus of claim 6 wherein said predetermined number of members is
equal to at most twenty.
Claim 8
Independent Claim
114 words
A method of controlling handoff of a mobile station from a
first base station to a second base station, the method comprising: monitoring the strength of pilot signals received by the mobile
station from a plurality of base stations including the first and second base
stations; receiving data from the mobile station representing the strength
and phase of the pilot signals received by the mobile station; and creating a ranked list of neighboring base stations to the mobile
station, the ranked list depending on the strength of each pilot signal
received by the mobile station and the number of times that a base station
is found as a neighbor of each pilot signal received.
Claim 9
Dependent Claim
181 words
The method of claim 8 wherein the creating step further comprises the steps
of: retrieving, from a memory unit, a fixed, predetermined neighbor list for each of
said pilot signals that said mobile station (18) is presently communicating with and
whose corresponding round trip delay time does not exceed a predetermined
threshold; generating (60) an union of neighboring base stations from said fixed,
predetermined neighbor lists; removing (65) from said union any member of said union which is a member
of an Active or Candidate Set; identifying (70), for each member of said union, said received pilot signals
which include said member in their respective fixed, predetermined neighbor lists ; calculating (75), for each of said members, a relative signal strength based
upon the number and signal strength of said received pilot signals which include said
member in their respective fixed, predetermined neighbor lists; sorting (95) said members based upon said relative signal strength; and selecting (100, 105) said members with the highest relative signal strengths to
be included in said Neighbor List Update Message provided to said mobile station
(18).
Claim 10
Dependent Claim
105 words
The method of claim 9 wherein the step of calculating relative signal strength for
each of said members is done in accordance with the equation: where Pj is equal to the signal strength of said received pilot j, f(Pj) is a
function of the signal strength of said received pilot j, RTDj is the round trip delay of
said pilot j, W k is the relative signal strength of member k in said union, RTD_MAX is
a pre-determined maximum round trip delay threshold, and {j} is the set of received
pilots which include member k in their respective unique, predetermined list of
neighboring base stations.
Claim 11
Dependent Claim
36 words
The method of claim 10 wherein the function f(Pj) is calculated in accordance
with the equation: f(Pj)=max(Pj-T_BASE,0); f(Pj)>0 where Pj is the signal strength of received pilot j and T_BASE is a pre-determined
minimum power threshold.
Claim 12
Dependent Claim
27 words
The method of claim 10 wherein the function f(Pj) is calculated in accordance
with the equation: f(Pj)=10 (Pj/10) where Pj is the signal strength of pilot j.
Claim 13
Dependent Claim
55 words
The method of claim 9 wherein the selecting step further comprises the steps of: removing from said union any of said members whose respective relative
signal strength is not greater than a predetermined minimal threshold (100); and removing from said union members with the lowest relative signal strength,
leaving a predetermined number of members (105).
Claim 14
Dependent Claim
18 words
The method of claim 13 wherein said predetermined number of members is equal
to at most twenty (105).
References Cited (Backward Citations)
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