Operating System Based Perceptual Evaluation of Call Quality in Radio Telecommunications Networks. Development of call quality assessment at mobile terminals using the Symbian operating system, comparison with traditional approaches and proposals for a tariff regime relating call charging to perceived speech quality.

摘要

Call quality has been crucial from the inception of telecommunication networks.udOperators need to monitor call quality from the end-user¿s perspective, in order to retainudsubscribers and reduce subscriber ¿churn¿. Operators worry not only about call quality andudinterconnect revenue loss, but also about network connectivity issues in areas where mobileudnetwork gateways are prevalent. Bandwidth quality as experienced by the end-user is equallyudimportant in helping operators to reduce churn.udThe parameters that network operators use to improve call quality are mainly from theudend-user¿s perspective. These parameters are usually ASR (answer seizure ratio), PDD (postdialuddelay), NER (network efficiency ratio), the number of calls for which these parametersudhave been analyzed and successful calls. Operators use these parameters to evaluate andudoptimize the network to meet their quality requirements.udAnalysis of speech quality is a major arena for research. Traditionally, users¿ perceptionudof speech quality has been measured offline using subjective listening tests. Such tests are,udhowever, slow, tedious and costly. An alternative method is therefore needed; one that can beudautomatically computed on the subscriber¿s handset, be available to the operator as well as toudsubscribers and, at the same time, provide results that are comparable with conventionaludsubjective scores. QMeter® ¿ a set of tools for signal and bandwidth measurement that haveudbeen developed bearing in mind all the parameters that influence call and bandwidth qualityudexperienced by the end-user ¿ addresses these issues and, additionally, facilitates dynamic tariffudpropositions which enhance the credibility of the operator.udThis research focuses on call quality parameters from the end-user¿s perspective. Theudcall parameters used in the research are signal strength, successful call rate, normal drop calludrate, and hand-over drop rate. Signal strength is measured for every five milliseconds of anudactive call and average signal strength is calculated for each successful call. The successful calludrate, normal drop rate and hand-over drop rate are used to achieve a measurement of the overalludcall quality. Call quality with respect to bundles of 10 calls is proposed.udAn attempt is made to visualize these parameters for better understanding of where theudquality is bad, good and excellent. This will help operators, as well as user groups, to measureudquality and coverage.udOperators boast about their bandwidth but in reality, to know the locations where speedudhas to be improved, they need a tool that can effectively measure speed from the end-user¿sudperspective. BM (bandwidth meter), a tool developed as a part of this research, measures theudaverage speed of data sessions and stores the information for analysis at different locations.udTo address issues of quality in the subscriber segment, this research proposes theudvarying of tariffs based on call and bandwidth quality. Call charging based on call quality asudperceived by the end-user is proposed, both to satisfy subscribers and help operators to improveudcustomer satisfaction and increase average revenue per user. Tariff redemption procedures areudput forward for bundles of 10 calls and 10 data sessions. In addition to the varying of tariffs,udquality escalation processes are proposed. Deploying such tools on selected or random samplesudof users will result in substantial improvement in user loyalty which, in turn, will bringudoperational and economic advantages.