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THE INTEGRATED EVALUATION OF THE QUALITY OF PHONE CONVERSATION UNDER NEW PERSPECTIVE
COMMUNICATION SERVICES
Terekhov Alexey Nikolaevich,
Candidate of Technics sciences, Associate professor at the Department of the General Theory of Communication MTUCI Russia, Moscow, kant@srd-mtuci.ru
Keywords: intelligibility; quality of serves; quality of experience; integral estimation of the quality; phone speech conversation service; new telephone services introduction; communication between objective parameters and subjective perception; compound numerals.
The method allows obtaining the integral estimation of the quality of phone speech conversation service in the period of the telecommunication network upgrading and/or new telephone services introduction. While analyzing the information, the new factors that influence the quality of the stationary mode communication industry were explored. The scientific researches including terminal polling, simulation modeling and other evaluations helped to determine the factors that influence user's estimation of quality of the upgrade and/or new telephone services introduction. The analysis of human perception of different auditory stimuli (speech, sound pulses), affecting with a time delay has been made. It was taken into consideration that if the noise (signal) consists of both direct sounds and reflected (delayed) sounds, then this fact is recorded with a correction for the delayed signal (echo). The hardware and software designed to evaluate the parameters of networks providing mobile communications services was developed in this study.
The proposed complex includes: an option of the type of codec, a network parametric variation, a calculation of MOS rated soundtrack by PESQ; and preliminary calculation of the MOS evaluation using a E-type calculator. The calculation of the theoretical values of MOS assessment is made at the input and/or changing of the relevant parameters related to the transmission of IP-packets. The program of the report preparation uses the synthesis at the level of words. In the experiments, intelligibility of compound numerals allowing accurately rate the quality of speech, due to the lack of a logical possibility to recover the missing information out of context is used. The results obtained with the help of the method allow to regulate the subscribers communication between a new phone speech conversation service and new telephone services.
Для цитирования:
Терехов А.Н. Метод интегральной оценки качества телефонного общения при модернизации сетей и/или введении перспективных услуг связи // T-Comm: Телекоммуникации и транспорт. - 2016. - Том 10. - №4. - С. 67-72.
For citation:
Terekhov A.N. The integrated evaluation of the quality of phone conversation under new perspective communication services. T-Comm. 2016. Vol. 10. No.4, рр. 67-72.
The aim of the research isthe development of evaluation method of telecommunication service quality, which may he applied directly over modernization and/or perspective telephone service introduction. Transient, which allows development of communication networks, may cause decrease inthe quality of experience of provided services. The topicality of the research, which allows development of evaluation method of telecommunication service quality and improvement of service quality is base don the fact, that existing methods for evaluation of communication services quality and the operation of the network unable to evaluate quality of experience during the modernization process directly. Objective evaluation methods are used to receive numerical values of quality of experience for telecommunication services. The analysis of the foreign literature showed that investigations, concerning the quality of experience of communication services during the network modernization have not been studied at all. The foreign experience in developing the communication networks shows simultaneous and uniform modernization of telecommunications, which explains lack of the evaluating service quality method of phone services. Domestic researches on telecommunications modernization quality have been conducted at the "broadcasting and electro-acoustic" chair in MTUCI. Previous researches could not be expected to undertake specification of network modernization {year 2013), there fore, the development of evaluating method and means of improving the quality of experience for telecommunications has been performed.
Some changing parameters have been identified and taken into account with a view to ensuring the guaranteed quality of the serv ices and detecting allowed level of its loss as a result of communication network development Typical reasons for the decline in the quality of the telephone services, based on the Quality of Experience (QoE), are noise and interference impacts, as well as Network Performance <NP) and Quality of Service (QoS) effects. For the current subscribers QoE reduction aggravated by long running and varied modernization process.
Analysis of chosen references and requirements documents, adapted to the evaluation of the quality of phone conversation under development and/or introduction of new perspective communication services, showed absence of: methods, which enable integrated evaluation of the provided phone services quality, based on modem communication networks. Developing of evaluating method and means of improving the quality of experience is aimed to provide guaranteed quality of experience directly during the modernization ofthe telecommunication network.
The novelty ofthe research is that during the process:
- It has been done the development of the integrated evaluation method of the telecommunication service quality, offering accounting the customer's perception of telecommunication network modernization process and/or perspective telephone service introduction and providing articulation of the requirements of a "Customer's in format i anal support during the period of the telecommunication network modernization and/or perspective telephone service introduction" service;
- quality of experience evaluation algorithm for phone service customers, which accounts subjective component of effective dial attempt rate and specific to Russian language during the compound numerals transmission over packet switched networks, have been made and implemented on PC [7, 9];
- it has been developed the procedure for assessing the probability of listing subscribers to notify about the telecommuniea-
tion network modernization process and/or perspective telephone serv ice introduction, guaranteeing the quality of experience;
- it has been developed the communication network perception criteria for notifying subscribers during the telecommunication network modernization process and/or perspective telephone service introduction, that allows termination threshold determination for subscriber's notification, considering environment parameters of data transmission.
In the course of research, an analysis had been undertaken to determine the main methods and tools for assessing the quality of telephone communication services. An analysis of results revealed that modern evaluation of phone services quality method is based on the quality of experience (QoE). QoE assessment of telephone service should provide: voice transmission; provisioning; network operation; user service; channels etc.
Phone service QoE components are proposed and grounded. It is revealed that time-consuming process of accessing information is the defining for the phone service QoE evaluation.
It was suggested to use compound numerals (during the phone number change), as the speech units most sensitive to the jitter and IP-packet latency, for the speech intelligibility detection, carried by IP-networks. Following indicators have been proposed for the evaluation ofthe phone service quality and discomfort appearing threshold: intelligibility; speech recognition and naturalness in various acoustic environments; phone number length; effects of channel parameters, recordings and coding methods; duration of customer's not i ileal ion period; storage volality and safety of transmitting in formation; subscriber's psychophysiology.
There have been made opinion polls among subscribers to identify the part of different factors and weight ratio, depending on QoE. Questions percentage ratio, defined as priority ones by the respondents, offer provisional weight ratio (table 1) for the main component of QoE [4,5].
Opinion polls provided assessment of customer's satisfaction and detect problem areas of services. Accuracy and reliability of information is confirmed by the representative selection and closeness of subject and polling questions. Total number in units and parts to the total percentage number of polled is the results ofthe polling. According to the social polling results, a simulation and software product, which allow the quality of speech transmission evaluation, have been made in order to inform subscribers about telephone number change.
For the evaluation of speech intelligibility it is used either relative or percentage amount of correctly received speech units by specially trained listeners from the total number of transmitted ones. Numeric intelligibility, that accurately evaluate the quality of the transmitting speech, by eliminating the logical ability to recover missed information from the context, is used in the experiment. It is concerned, that during the soundtrack synthesis, reliable pause perception for voice signal should last 150-200 ms [6, 7].
Integral performance index is calculated by formula:
{QoS)=K
tVA INT IW,). 0)
Integral performance index is calculated by formula:
^ECA ttft ~ ^ECA QoS^ECA QoE^rtp JMt ' (")
where KKA ^ - effective call attempt ratio, defined by [61; Krep ,,„ - adjusting factor, without perception of subscribers response; KB t lM - effective call attempt ratio, concerning subjective factors.
T-Comm Том 10. #4-2016
Table 1
Criteria and factors of Quality of experience (QoE) in communication services
Component stress factor _xim/ Absolute (relative) component stress factor — ""'"у / threshold Interconnection rate щ t* ; (л.-:
Duration of changing parameters1 notifica-lion period, months 0 (0) 3 (1,78) 6 (2,44) 12 (2,87) more than 12 (2,89) 0,28 0,325
Phrase intelligibility, % less than 35 (0,044) 25-40 (0,22) 40-56 (2) 56-80 (2.4) 80-100 (2,88) 0,24 0,182
Number of QMC before answer, pes. more than 12 (0,021) 9-12 (0,023) 6-9 (1,1) 3-6 (1,88) less than 3 (2,33) 0,18 0,011
Phone number variations 5 (0,020) 4 (0,024) 3 (1,04) 2 (1,55) 1 (1,66) 0,14 0,05
Required quality of information transfer 1 (0,019) 2 (0,025) 3 (0.11) 4 (Ml) 5 (1,4) 0,075 0,015
Background noise level, dBA more than 75 (0) 65-75 (0,018) 55-65 (0,026) 45-55 (0,29) less than 45 (1,33) 0,07 0,028
Signal / noise ratio, dB lessthan 6 (0) 6-15 (0,020) 15-25 (0,024) 25-35 (0,066) more than 35 (0,22) 0 0
Private indicator weight ratio ((,)x) 0.2 0,4 0,6 0.8 1,0
Assessment of the difficulties very strong strong medium easy not felt
Point-based assessment 1 2 3 4 5
Percent age assessment 20 40 60 80 100
MOS-tvaluation of perceived information < 1,7 1,7-2,5 2,5-3,0 3,0-4,0 4,0-4,5
Subscriber's service quality unacceptable unsatisfactory satisfactory good excelent
K,,C1 ^ - effective call at tempts ratio, defined by [GD 45.056-20001 0,99999
KHI ,m, - effective call attempts ratio, considering subjective subscriber's perception of objective network parameters (simulation) 0,536
K uj, - factor, which consider calls on changed numbers with LMI installed (if all numbers are changed K' = 0,5, for no changes Krep u„=!) 0.5- I
Ktot mr = kecj&sKe.cA&£K«p. mi ~ effective call at tempts integrated ratio 0,268 -0,536
KFCA tii& - effective call attempts ratio, considering subjective subscriber's perception of objective network parameters (Natural experiment) 0,571
Relative error of simulations and natural experiment 6.5 %
rnM1 - factor current value
x^mj - factor perception threes hold at the level of research errors (45 answers or 3%)
During the post modernization period, factors, defining quality of experience, may chan«e.
^ECA y../, £(JW ) ^ 2 ( OiiF. ) > m M
(3)
where NCDNgi>E — amount of correctly dialed phone numbers; iV„(f(/„f;- total amount of numbers dialed by each expert; m - number of experts.
N
eng colis j
'N»
calb ^
(4)
where N„
amount of calls to changed number; N,n, cMt -
total amount of calls. In the process of weight coefficient assignation, expert regressive method of weight coefficients determination against which and expression for the K£Ci¡^, determined
in the (2, 3,4), formula 1 will be as follows:
" j Vvv I /
/fK
M™-
(5)
к
where N^.^ - Amount of correctly dialed phone numbers; NtMjQag - total amount of numbers dialed by each expert; m — number of experts, N — — amount of changed numbers, Nl0l nullllJ - total amount of numbers [7],
Krip im is influenced by encoding methods, used in notification. Results, shown in the figure 1, describe the method for evaluation of speech transmission quality, made by subjective methods for encoding and information recording methods [1, 2], used during notifications about the telecommunication network modernization and/or perspective telephone service introduction.
Kn/I ,,„ is also influenced by phrase intelligibility of compound numerals, which is defined by the pause duration between its elements.
Figure 2 presents the dependence of phrase intelligibility of compound numerals on the duration of pauses [7, 10], which was revealed in the course of the research.
T-Comm Vol.10. #4-2016
service. Introduction to the new service requirements will provide guaranteed quality of service under modernization and/or perspective telephone service introduction.
2. it has been made the development of evaluation method of telecommunication service quality, which may be applied directly over modernization and/or perspective telephone service introduction on the packet-switched networks.
3. Algorithm for simulation modeling of evaluation of telecommunication service quality, taking into consideration communication network parameters, have been developed and implemented on PC. it has been adapted the modernization method for calculation of effective call attempt coefficient, based 011 quality of service perception for the process of network modernization and/or during the perspective telephone service introduction. Simulation results show, that dependencies of necessary number of notification about modernization process and/or perspective telephone service introduction on different factors have been obtained.
4. Reasons for the decrease in quality of experience of communication services during the network modernization and/or perspective telephone service introduction have been discovered. A possibility of application the recommendation concerning the international organizations for standardization the QoK and QoS to provide the numerical evaluation of decrease has been discovered;
5. Criteria of perception of quality, evaluations ofquality related to them, their permissible range and the algorithm for detecting Hie probability of cessation the notifications about the modernization process and/or perspective telephone service introduction have been developed;
6. Encoding methods and ways of recording speech for the data messaging synthesis, considering the specifics of perception of compound numeral, used in network modernization and/or perspective telephone service introduction have been analyzed.
7. The received results of the research have been introduced in the Moscow city telephone network as a devices for notification about the process of network modernization and/or perspective telephone service introduction, and implemented in section concerning the quality of phone service perception, which were suggested by OJSC "Rostelecom" in 2012, of the research project "Development of Quality of Experience (QoE) methods for multiple-system services on parameters of Quality of Service and the concept of automatic continuous control of phone transmission quality "end-to-end"".
The results of the research w ere obtained using elements of probability theory methods and theory of mass service. In order to assess the quality of voice transmission and intelligibility some subjective (paired comparison, score) and objective (intrusive, n on intrusive, simulated) methods have been used, as well as computer modeling, with experimentally confirmed results. The implementation of the evaluation method of telecommunication service quality and means of it's improving in the period of the modernization process and/or perspective telephone service introduction, as well as experimental testing of the developed methods, models and hardware and software development tools have been made. Achieved results arc strongly suggested to be used by telecom operators, planning and research organizations in order to assess the quality of current and planned telecommunication services, even during modernization of the networks. The research can serve as a basis for further evaluation of the service quality, provided by the packet-switched systems.
Conclusions
1. Analysis of present legal proceedings, adapted to the evaluation of the telecommunication voice services quality, on the period of modernization process and/or perspective telephone service introduction has shown an absence of methods for integrated evaluation of quality of experience (QoE), taking into account subscriber's reaction.
2. One of the possible options for the Quality of Experience assessment and its correlation with objective parameters (QoS) of communication netw orks may be suggested method for detection of effective call attempt ratio.
3. Developed method includes algorithm and software for effective call attempt ratio evaluation of one of the main QoS indicators based on subjective reaction of subscriber,
4. During the integrated evaluation of the quality of the phone conversation should be considered such aspects as influence of channel interference, including ones, that appear during IP transmission; volume of acoustic noise; encoding methods, used in telecommunication networks and audio-information services for the data message synthesis with specifics of transmitted compound numerals permission taken into account.
References
1. Terekhov A.N, Relative method of express - evaluation of voice quality in audio information systems. Proceedings of the International Joint school and conference «Young Scientists in Electronics: Science, Technology and Education». «Young scientists - 2006», Pan !. Moscow. Energoatomizdai. MtREA. December5-9. 2006. Pp. 175-179. (inRussian)
2. Terekhov A.N., Orlov V.G. Evaluation of speech quality in the PSTN audio information devices, fundamental problems Of radio engineering and device construction. Proceedings of the International Scientific and Technical Conference «Intermatic - 2008». Part 5. Moscow. Energoatomizdat. MIREA. October 21-23, 2008, Pp. 272-277. (inRussian)
3. Terekhov A.N. Improving the reliability of establishing a telephone connection with audio information dcvices / T-Comm. 2011. No.2, pp. 44-46. (in Russian)
4. Terekhov A.N.. Rysin Y.S. Algorithm for assessing the impact of negative factors on the quality of telephone communication / T-Comm, 2012, No. 10, pp. %-9S. (in Russian)
5. Terekhov A.N. The draft methodology for calculating the optimum amount of audio information devices required to inform subscribers of the PSTN telephone numbering change / T-Comm. 2012. No. 4. Pp. 79-82. (inRussian}
6. Terekhov A.N., Rysin Y.S, Effect of breaks in transmission compound numerals on IP-communication networks upon a factor of effective call attempts. International scientific and technical conference. Fundamental problems of radio engineering and device construction. Proceedings of the International Scientific and Technical Conference «Intermatic - 2012», Part 5. Moscow, Energoatomizdat MIREA. December 3-7. 2012. Pp. 98-103. (in Russian)
7. Terekhov A.N. Project method of calculating the optimum number of answering machines, necessary to inform the PSTN subscribers to amend the phone numbers / T-Comm. 2012. No. 10. Pp. I 12-¡16. (in Russian)
8. Terekhov A.N., Rysin Y.S., Venediktov M.D. Hardware-software complex for estimating parameters of networks, allowing phone communication services / T-Comm. 2013. Vol. 7. N0,8. Pp. 39-43. (in Russian)
9. Terekhov A.N. Analysis of the possibility of estimation of quality of voice PBX, based on cloud technologies. International scientific and technical conference, fundamental problems of radio engineering and device construction. Proceedings of the International Scientific and Technical Conference «Intermatic - 2014». Part 5. Moscow. Energoatomizdat. MIREA. December 1-5. 2014. Pp. 255-257. (in Russian)
10. Terekhov A.N.. Rysin Yu.S. Some perception thresholds of delayed acoustic signals (echoes) / T-Comm. 2015. Vol. 9, No.4, Pp. 51-53. (in Russian)
PUBLICATIONS IN ENGLISH
МЕТОД ИНТЕГРАЛЬНОЙ ОЦЕНКИ КАЧЕСТВА ТЕЛЕФОННОГО ОБЩЕНИЯ ПРИ МОДЕРНИЗАЦИИ СЕТЕЙ И/ИЛИ ВВЕДЕНИИ ПЕРСПЕКТИВНЫХ УСЛУГ СВЯЗИ
Терехов Алексей Николаевич,
к.т.н., доцент кафедры ОТС МТУСИ, kant@srd-mtuci.ru
Аннотация
Представленный метод позволяет получить интегральную оценку качества речевых телекоммуникационных услуг, предоставляемых абонентам в период модернизации телекоммуникационных сетей и/или введения перспективных услуг связи. Анализ нормативной базы выявил основные факторы, влияющие на качество услуг связи, оказываемых при функционировании телекоммуникационных сетей в стационарном режиме. Проведенные исследования, выполненные с позиции абонентов, включающие: репрезентативные опросы; результаты имитационного моделирования; оценки, полученные в ходе натурного эксперимента, определили доминирующие показатели, влияющие на абонентскую оценку качества при модернизации сетей и/или введении перспективных услуг связи. Приведён краткий анализ восприятия человеком различных звуковых раздражителей (речи, звуковых импульсов, постоянных и не постоянных шумов, тональных шумов) действующих на него с временной задержкой. Учтено, что если шум (сигнал) состоит как из прямых звуков, так и отражённых (запаздывающих) звуков, то этот факт учитывается с помощью поправки на запаздывающий сигнал. В работе разработано аппаратное и программное обеспечение, предназначенное для оценки параметров сетей, предоставляющих услуги мобильной связи. Предлагаемый комплекс предусматривает: возможность выбора типа кодека; изменение сетевых параметров; расчет MOS оценки фонограммы методом PESQ; предварительный расчет MOS-оценки при помощи калькулятора E-модели. Расчет теоретических значений MOS-оценки производится при вводе и/или изменении соответствующих параметров, относящихся к передаче IP-пакетов. В программе для формирования сообщений использован синтез на уровне слов. В эксперименте использована разборчивость сложносоставных числительных, позволяющая точно оценить качество передаваемой речи, за счет отсутствия логической возможности восстановить пропущенную информацию из контекста. Результаты, полученные с использованием данного метода, и учитывающие взаимосвязь между объективными параметрами телефонного общения и субъективными показателями их восприятия, способны регламентировать отношения между операторами, предоставляющими новые услуги связи, и их потребителями
- абонентами, в том числе и при модернизации телекоммуникационных сетей.
Ключевые слова: разборчивость; качество оказания услуги; качество обслуживания; интегральная оценка качества; телекоммуникационные услуги; введение новых услуг и качество их предоставления; связь между объективными параметрами и субъективным восприятием; сложносоставные числительные.
Литература
1. Терехов А.Н. Относительная методика экспресс-оценки качества передачи речи в аудиоинформационных системах. Международная научно-техническая школа-конференция "Молодые учёные - 2006". Материалы конференции, Часть 1. М.: МИРЭА, 5-9 декабря 2006. С. 175-179.
2. Терехов А.Н., Орлов В.Г. Оценка качества речи в аудиоинформационных устройствах для телефонных сетей общего пользования. Международная научно-техническая конференция. Фундаментальные проблемы радиоэлектронного приборостроения "Интерматик
- 2008". Материалы конференции. М.: Энергоатомиздат, 21-23 октября 2008. С. 272-277.
3. Терехов А.Н. Повышение надёжности установления телефонного соединения за счёт использования аудиоинформационных устройств // Т-Comm: Телекоммуникации и транспорт, №2, 2011. С. 44-46.
4. Терехов А.Н., Рысин Ю.С. Алгоритм оценки влияния негативных факторов на качество телефонного общения // T-Comm: Телекоммуникации и транспорт, №10, 2012. С. 96-98.
5. Терехов А.Н. Проект методики расчёта оптимального количества аудиоинформаци-онных устройств, необходимого для информирования абонентов ТфОП об изменении телефонной нумерации // T-Comm: Телекоммуникации и транспорт, №4, 2012. С. 79-82.
6. Терехов А.Н., Рысин Ю.С. Влияние пауз при передаче сложносоставных числи-тельных по IP-сетям связи на коэффициент эффективных попыток вызова. Международная научно-техническая конференция. Фундаментальные проблемы радиоэлектронного приборостроения "Интерматик - 2012". Материалы конференции, Часть 5. М.: Энергоатомиздат, 3-7 декабря 2012. С. 98-103.
7. Терехов А.Н. Проект методики интегральной оценки качества телефонного общения при модернизации сетей и/или введении новых услуг связи // T-Comm: Телекоммуникации и транспорт, №10, 2012. С. 112-116.
8. Терехов А.Н., Рысин Ю.С., Венедиктов М.Д. Программно аппаратный комплекс для оценки параметров сетей, обеспечивающих телефонные услуги связи // Т-Comm: Телекоммуникации и транспорт, Т.7., №8, 2013. С. 39-43.
9. Терехов А.Н. Анализ возможности применения методов оценки качества передачи речи для АТС, выполненных на базе облачных технологий. Международная научно-техническая конференция. Фундаментальные проблемы радиоэлектронного приборостроения "Интерматик - 2014". Материалы конференции, Часть 5. М.: Энергоатомиздат, 1-5 декабря 2014. С. 255-257.
10. Терехов А.Н., Рысин Ю.С. Некоторые пороги восприятия запаздывающих акусти-ческих сигналов (эхо-сигналов) // Т-Comm: Телекоммуникации и транспорт, № 4, 2015. С. 51-53.
