EP0648032A1
Expired / Lapsed
EP
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A signal quality detecting circuit and method for receivers in the GSM system
Assignee: Nokia Oyj
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Filing: 1994-10-11
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Granted: —
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Expires: 2014-10-11
Abstract
Abstract The invention provides an improved method and apparatus for identifying a bad GSM speech frame. Both the estimated signal-to-noise ratio (ESNR) of the received signal and the pseudo bit error rate (PBER) of a recoded speech signal are used to determine whether or not a speech frame is bad.
Inventors
- 👤 Ilkka Heikkila
- 👤 Harri Jokinen
- 👤 Jukka Ranta
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 10:56
CPC Classifications
H; H04; H04L; H04L1/00; H04L1/20; H04L1/201; H04L1/208
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
60 words
A decoder for a radio telephone, for providing a decoded signal from a signal transmitted in respective groups comprising: means for providing first and second quality measures for estimating the quality of each of the transmitted signal groups received; and means responsive to the first and second quality measures for desregarding signal groups failing to meet a chosen quality threshold.
Claim 2
Dependent Claim
24 words
A decoder according to claim 1 wherein the first and second quality measures are an estimated signal-to-noise ratio and a pseudo bit error rate.
Claim 3
Dependent Claim
22 words
A decoder according to claim 2 wherein the estimated signal-to-noise ratio comprises a vector indicative of the signal-to-noise ratio of a unit.
Claim 4
Dependent Claim
21 words
A decoder according to claim 2 wherein the estimated signal-to-noise ratio comprises a scalar defining the approximate signal to noise ratio.
Claim 5
Dependent Claim
30 words
A decoder according to any preceding claim wherein the means for determining comprises means for comparing a linear combination of the first and second quality measures with a threshold value.
Claim 6
Dependent Claim
51 words
A decoder according to any one of claims 1 to 4 wherein the means for determining comprises means for determining a threshold value based on one or both of the quality measures, and means for comparing a function of the other or both of the quality measures with the threshold value.
Claim 7
Dependent Claim
30 words
A decoder according to claim 6 wherein the threshold value is a function of the signal-to-noise ratio variance and the pseudo bit error rate is compared with the threshold value.
Claim 8
Independent Claim
58 words
A method for identifying a faulty signal group transmitted in a digital radio telephone system comprising: determining a first quality measure indicative of the quality of the signal group; determining a second quality measure indicative of the quality of the signal group; and disregarding a faulty signal group is faulty based on the first and second quality measures.
Claim 9
Independent Claim
97 words
A method for identifying a bad GSM speech frame in digital mobile phone systems, characterized in that the estimation of the quality of the received signal is carried out using - estimated signal-to-noise ratio ESNR so that the ESNR is a vector comprising the estimated signal-to-noise ratio of each received burst or a scalar describing their approximate signal-to-noise ratio, and - pseudo bit error rate PBER of the received and recoded speech frame, the ESNR and PBER being functionally related to a chosen threshold and a speech frame is removed if it fails to meet the threshold.
Claim 10
Dependent Claim
34 words
A method according to claim 9 wherein the speech frame is removed if f(ESNR, PBER) > T where f is a function of variables ESNR and PBER and T is a chosen threshold value.
Claim 11
Dependent Claim
27 words
A method according to Claim 9 or 10, wherein the function is so formed that the number of faulty decisions to remove speech frames can be minimized.
Claim 12
Dependent Claim
58 words
A method according to Claim 9 or 10 wherein f(a,b) = (C1 * a) + (C2 * b) is chosen for the function so that the speech frame is removed if (C1 * ESNR) + (C2 * PBER) > T where C1 and C2 are constants and the function is a linear combination of variables ESNR and PBER.
Claim 13
Dependent Claim
29 words
A method according to Claim 9, wherein the function is implemented in the form of a table so that the ESNR and PBER are indexed variables of the table.
Claim 14
Independent Claim
21 words
A method according to any one of Claims 9 to 13, wherein function f and threshold limit T are made adaptive.
Claim 15
Dependent Claim
72 words
A method according to Claim 10, wherein - the threshold value is calculated BFI_LIM = (SNR_VAR) - C1) * C2 + C3 where SNR_VAR is a variance of the values of the ESNR-vectors - the obtained result BFI_LIM is limited in the following way C4 ≦ BFI_LIM ≦ C5 so that the speech frame is removed if PBER > BFI_LIM where C1, C2, C3, C4 and C5 are constants defined by simulation.
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