Electrical computers and digital processing systems: multicomput – Computer network managing – Computer network monitoring
Reexamination Certificate
2000-07-10
2004-06-08
Barot, Bharat (Department: 2154)
Electrical computers and digital processing systems: multicomput
Computer network managing
Computer network monitoring
C709S223000, C709S236000, C370S241000, C370S401000
Reexamination Certificate
active
06748433
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and a system for controlling quality of service over a network, and in particular—over a packet switched data network, such as over IP (Internet Protocol).
BACKGROUND OF THE INVENTION
It is widely known, that modem telecommunication networks comprise different interconnected domains, for example a PSTN (Public Switched Telephone Network) which was originally designed for handling voice calls, and a packet switched network which, by its nature, is data oriented. Nowadays, all kinds of services or transmission types (e.g., voice, fax or data) are transmitted through the combined networks and are inevitably subjected to many factors which affect the quality of service expected by a particular subscriber. The above-mentioned factors stem not only from the nature of a particular network domain, but also (and to the great extent) from the growing traffic load in the modem telecommunication networks.
In packet switched networks, real time services such as voice, fax, real-time video conference (e.g., packetized voice signals of Voice over IP), are mixed with data signals and, as a result, suffer from degradation that is not encountered in the regular circuit-switched networks (e.g., PSTN). The degradation may occur due to such known packet networks' problems, as packet loss, packet delay and packet delay variation (so-called jitter) which are known as specific criteria of data transmission quality.
While in the PSTN the voice channels are assigned to a constant, assured bandwidth, in packet switched networks the bandwidth varies dynamically, depending on data and voice traffic in the network. In order to ensure a given quality of the voice signal, a service provider in the packet switched network must assure both a minimum bandwidth at all times, and keep the three criteria mentioned above within given limits. For example, it becomes difficult to carry on a voice conversation if the packet delay exceeds 200 ms.
While for data traffic control in the packet switched networks it may be enough to monitor some performance criteria such as the packet delay, in the case of voice traffic various parameters combine in an infinite number of possible combinations so that, there is no simple correlation between these parameters and the actual voice quality heard by the caller.
Voice networks have traditionally been tested by injection of test sentences at one (transmitting) end, and having this sentence heard and its clarity subjectively graded by a group of people at the other (receiving) end of the path. The test result is called a Mean Opinion Score (MOS) and ranges from 1 (poor) to 5 (excellent).
To convert this obviously subjective method to an objective one, real measurements of quality should serve the basis for conclusions. To this end, two main approaches were proposed. The first one can be classified as an intrusive approach, which is based on comparison of a transmitted signal to the same received signal, and examining the difference. There are a number of models enabling to arrive to the MOS results using the above comparison, for example PSQM model (described in the International ITUT standard Q862) and PAMS model developed by British Telecom (BT). It should be noted, that PAMS is the only model which takes into account problems in the quality of service which may be brought to data networks by phenomena such as packet delay, packet loss, jitter, etc. The second approach is a non-intrusive approach based on measuring physical parameters such as noise, delay, echo etc., and improving thereof up to a satisfactory level. A number of models exist, for example E-model of ITUT standard body and a CCI (Call Clarity Index) developed in BT. Presently, there is no such a non-intrusive model, which would take into account problems of quality degradation due to data networks.
Nowadays, voice services providers which utilize packet switching in their networks, cannot assure the desired voice quality to their customers in advance, since the voice quality of service is not monitored in the networks to the extent allowing that.
On the other hand, fully loaded networks suffer from shortage of lines, and very often the quality of service (with respect to voice, fax and data) is reduced due to low connectivity in the network and low availability of destination points.
None of the relevant methods and systems known to the Applicant describes or suggests any combined Quality of Service estimation mechanism for a network, which would enable integral monitoring of the quality of service, and control of the quality of service to be provided.
SUMMARY OF THE INVENTION
It is therefore the object of the present invention to provide a method of determining quality of the telecommunication service over a telecommunication network based on a novel, combined estimation of quality of service for this network. A further object of the invention is to provide a method, a system and an equipment for monitoring and controlling the quality of service in the network, based on the combined estimation thereof. The invention is most effectively applicable to modem telecommunication networks including packet switched networks.
The above main object can be achieved by a method of determining quality of telecommunication service over a telecommunication network, the method including the following steps:
a) obtaining data on quality of service over a number of routes in the network by determining, for each route, N of parameters p
i
, each of said parameters p
i
reflecting either a quality of transmission of a particular service (transmission type) through said route or a statistical characteristics of said route's availability to a subscriber,
b) building an objective quality score (OQS) for each of said routes, the OQS being a multi-profile quality estimation equation presenting a sum of N said parameters p
i
taken with respective weight functions W
i
(p
i
) thereof.
It is further proposed, that the weight functions W
i
(p
i
) reflect a preferred profile of the quality of service in said network and are presented as positive numbers in the range 0≦W
i
(p
i
)≦1 selected so that M values of said weight functions W
i
(p
i
) are more than 0, (M≦N), and the sum of the selected values of the W
i
(p
i
) is equal to 1.
Preferably, the method also comprises step (c):
c) selecting one or more routes having the OQS value not lower than a predetermined OQS value for further routing the telecommunication services there-through.
It should be mentioned, that for effecting control of the service quality, an additional step is to be effected, i.e. the step of routing the telecommunication services over said one or more selected routes.
It is understood, that said particular service (transmission type) is one of components in a non-limiting list comprising voice, fax and data.
The mentioned equation can be presented in the following form:
OQS
=
∑
i
=
1
N
W
i
(
p
i
)
p
i
1
wherein:
OQS—is the objective quality score estimation
pi—a value of a parameter “i” in a particular route in the network
W
i
(p
i
)—weight function of the parameter “i” (in one simple particular case W
i
(p
i
) may be a constant coefficient of the parameter “i”)
N—is the number of parameters defined for the network.
The above-mentioned parameters preferably comprise at least the following five (N=6) characteristics of the quality of service for particular transmission types and the network of interest:
p
1
—is a voice Quality of Service parameter QoS which can be estimated using at least one of the following methods known in the prior art: CCI (Call Clarity Index), PAMS (Perceptual Analysis Measurement System), PSQM (as defined in the international ITUT standard Q-862), E-model, etc.,
P
2
—is a Fax Quality of Service parameter estimated, for example, according to a statistically obtained ratio between a number of errors during a fax transmission and a number of pages in the fax, or other methods, for example based on checking a coded message enclosed in a particul
Barot Bharat
Ectel Ltd.
Nath & Associates
Novick Harold L.
LandOfFree
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