International telecommunication union
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- Selecting QoS Parameters from different standards
- ITU-T Y.1540, Y.1541
- 3GPP TS 23.107, 3GPP TS 23.203, 3GPP TS 23.401
- Approach for defining new parameters
QoE parametersVarious IMT-2020 standards differ in terms of parameters employed to evaluate QoS. Since QoS parameters are the basic building block of QoS framework, it is necessary to define QoS parameters for IMT-2020. In this context, this section proposes two methodologies for defining QoS parameters of IMT-2020 to build the fundamentals of common end-to-end QoS framework for IMT-2020.
To select relevant QoS parameters from existing standards, it is necessary to identify the QoS parameters employed by existing standards. This section will therefore review the parameters of wireline standard from ITU-T and wireless standard from 3GPP.
ITU-T recommendation Y.1540 defines different QoS parameters and Y.1541 selects four major parameters to classify QoS classes: IPTD (IP Packet Transfer Delay), IPLR (IP Packet Loss Ratio), IPER (IP Packet Error Ratio) and IPDV (IP Packet Delay Variation). IPTD is the time between the occurrences of two corresponding IP packet reference events. IPTD in this context denotes mean IP packet transfer delay performance parameter, which is the arithmetic average of IP packet transfer delays for the population of interest. IPLR is the ratio of total lost IP packet outcomes to total transmitted IP packets in a population of interest. In other words, it describes how many packets were lost relative to number of packets transmitted. IPER is the ratio of total errored IP packet outcomes to the total of successful IP packet transfer outcomes plus errored IP outcomes in a population of interest. In other words, it describes how many packets faced error out of all packets that were transferred. IPDV is the packet delay variation in the two-point interval experienced relative to the reference IP packet transfer delay (it is the absolute IP packet transfer delay experienced by a selected IP packet between the two points). Please note that the parameters on end-to-end interval are derived from their counterparts in segments of the network and the method is described in Y.1541.
3GPP, as noted in previous input documents, defines QoS with the concept of bearer. Bearer is a link between two end-points defined by a certain set of characteristics (on layers 1 to 2/2.5). The QoS is then controlled by two major parameters: QCI (QoS Class Identifier) and ARP (Allocation and Retention Priority). Holistically, ARP is the standard for prioritizing bearer establishment and QCI is the standard for prioritizing packet transfer. ARP will consist of the priority level and parameters related to “pre-emption” of resources. QCI, on the other hand, provides detailed QoS information for types of bearers. Firstly, bearers are defined either as GBR (Guaranteed Bit Rate) or MBR (Maximum Bit Rate) where the former serves to guarantee the throughput. Secondly, bearers possess thresholds of parameters such as packet delay and packet error loss rates to ensure QoS. Packet delay is an upper bound for the time that a packet may be delayed between the UE (user equipment) and PCEF (Policy and Charging Enforcement Function). It is, in other words, a maximum delay with a confidence level of 98 percent. Packet error loss rate is an upper bound for the rate of SDUs (Service Data Unit; e.g., IP packets) that have been processed by the sender of a link layer protocol but that are not successfully delivered by the corresponding receiver to the upper layer. In other words, it defines an upper bound for a rate of non-congestion related packet losses. (3GPP TS 23.203)
This section proposes to utilize the framework by ITU-T Recommendation I.350 in defining new parameters. Recommendation I.350 defines 3x3 matrix for QoS parameters with each row representing one of the three basic and distinct communication functions (access21, user information transfer22 and disengagement23) and each column representing one of the three mutually exclusive outcomes possible when a function is attempted (speed24, accuracy25 and dependability26). Table 2 shows the defined 3x3 matrix for QoS parameters. The parameters are then mapped onto the matrix with outage thresholds defined. Table 4. 3 x 3 matrix approach for QoS parameters
The 3x3 performance matrix may be extended to address QoS and NP of IMT-2020. The performance criterion might be supplemented with criteria such as ease-of-use. The communications functions might be supplemented with information storage, information translation, and brokerage functions. Such addition of functions and criteria is possible, but the functions should be quantifiable. Identification of each affordable parameter is for further study. Editor’s Note #1: Figure1/G.1000 shows the extended matrix between criteria and function to facilitate identification of communications QoS criteria. Editor’s Note #2: The parameters should take into account the characteristics of IMT-2020 specific applications such as remote surgical operation, autonomous driving and virtual reality. The details are for further study Editor’s Note #3: In addition, for Device-to-Device and Device-to-Network cases with very low delay (1ms), definition of Measurement Point and Monitoring Methodology is critical. The details are for further study.
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