Lecture#10 Quality of service The Bonch-Bruevich Saint-Petersburg State University of Telecommunications Series of lectures “Telecommunication networks” Instructor: Prof. Nikolay Sokolov,

Definitions In the Recommendation E.800 and in a number of other ITU-T documents several similar definitions of the term "Quality of service" are formulated: 1. Totality of characteristics of a telecommunications service that bear on its ability to satisfy stated and implied of the user of the service (E.800). 2. The collective effect of service performance which determine the degree of satisfaction of a user of a service. It is characterised by the combined aspects of performance factors applicable to all services, such as; - Service operability performance; - Service accessibility performance; - Service retain ability performance; - Service integrity performance; and - Other factors specific to each service (Q.1741). 3. The collective effect of service performances which determine the degree of satisfaction of a user of the service (Y.101). 4. The collective effect of service performance which determine the degree of satisfaction of a user of a service. It is characterized by the combined aspects of performance factors applicable to all services, such as bandwidth, latency, jitter, traffic loss, etc (Q.1703).

Dynamics of speech quality

Recommendation ITU-T E.800 (1)

Recommendation ITU-T E.800 (2)

Recommendation ITU-T E.800 (3)

Recommendation ITU-T E.800 (4)

Recommendation ITU-T E.800 (5)

Recommendation ITU-T E.800 (6)

Main terms (1) 1. Quality. The totality of characteristics of an entity that bear on its ability to satisfy stated and implied needs. Note – The characteristics should be observable an/or measurable. When the characteristics are defined, they become parameters and are expressed by metrics. 2. Service. A set of functions offered to a user by an organization constitutes a service. 3. Item (entity; element). Any part, device, subsystem, functional unit, equipment or system that can be individually considered. 4. User. A person or entity external to the network, which utilizes connections through the network for communication. 5. Customer. A user who is responsible for payment for the service.

Main terms (2) 6. Service accessibility performance. The ability of a service to be obtained, within specified tolerances and other given conditions, when requested by the user. 7. Service integrity performance. The degree to which a service is provided without excessive impairments, once obtained. 8. Network performance. The ability of a network or network portion to provide the functions related to communications between users. 9. Trafficability performance. The ability of an item to meet a traffic demand of a given size and other characteristics, under given internal conditions. 10. Dependability. Performance criterion that describes the degree of certainty (or surety) with which the functions is performed regardless of speed or accuracy, but within a given observation interval.

Main terms (3) 11. Service integrity performance. The degree to which a service is provided without excessive impairments, once obtained. 12. Network performance. The ability of a network or network portion to provide the functions related to communications between users. 13. Trafficability performance. The ability of an item to meet a traffic demand of a given size and other characteristics, under given internal conditions. 14. Availability. The ability of an item to be in a state to perform a required function at a given instant of time or at any instant of time within a given time interval, assuming that the external resources, if required, are provided. 15. Reliability performance. The ability of an item to perform a required function under given conditions for a given time interval.

Main terms (4) 16. Transmission performance. An indication of a communication signal at the egress of network compared to its performance at the ingress to the network. The indication of performance is expressed by a choice of pertinent parameters for the application or service in question. 17. Propagation performance. The ability of a propagation medium, in which a wave propagates without artificial guide, to transmit a signal within the given tolerances. 18. End-to-end quality. Quality related to the performance of a communication system, including all terminal equipment. 19. End-to-end IP network. The set of exchange link and network section that provide the transport of IP packets transmitted from source host to destination host. 20. End-to-end IP network performance. Measurable relative to any given unidirectional end-to-end IP service.

Service Level Agreement (SLA) For some subscribers, the quality of service determines business processes to a great extent. According to USA financial institutes’ data, the losses due to inaccessibility of the telecommunication services during one hour (downtime cost) of 25% of American companies do not exceed 50 thousand dollars, of another 25% — 100 thousand dollars, and of the rest half of the companies — more than 100 thousand dollars. For the American brokerage firms, the value of that index is assessed at 6 million dollars. SLA is considered as a part of a service contract where some indices have been defined. SLA is an individual negotiation between two parties: ROA and customer. It records the common understanding about services, priorities, responsibilities, guarantee, etc. with the main purpose to agree on the level of service. For example, it may specify the levels of availability, serviceability, performance, operation or other attributes of the service like billing and even penalties in the case of violation of the SLA.

QoS and NGN (1)

QoS and NGN (2)

QoS and NGN (3)

QoS and NGN (4)

Problem of the transition to NGN PSTN Operators should find viable strategy of the transition to NGN, which provides protection of investments in circuit- switched technology. Source: B. Jacobs. Economics of NGN deployment scenarios: discussions of migration strategies for voice carriers. – It is necessary to combine PSTN’s quality of service and IP technologies’ economic efficiency!

QoS aspect: time irreversibility Speech quality impairment compensation in networks with circuit switching: Elaboration of the new speech signal processing algorithms; Signal amplification (when necessary). Speech quality impairment compensation in IP networks under condition of the excessive packet transfer delay: Impossible in principle!!!

QoS support

Recommendation ITU-T G.107 (1)

Recommendation ITU-T G.107 (2) send loudness rating (SLR) receive loudness rating (RLR) overall loudness rating (OLR) weighted listener echo path loss (WEPL) sidetone masking rating (STMR) listener sidetone rating (LSTR) talker echo loudness rating (TELR) D-Value of telephone, receive side (Dr) D-Value of telephone, send side (Ds)

Recommendation ITU-T G.107 (3)

Recommendation ITU-T G.107 (4)

Recommendation ITU-T G.107 (5)

Instructor: Prof. Nikolay Sokolov, Questions? Quality of service