International telecommunication union
Examples of end-to-end connectivity over wireless and wireline networks
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- 13.2 Domestic Video Telephony
- 13.3 Telecommunication services for Emergency/Disaster Relief
13 Examples of end-to-end connectivity over wireless and wireline networksEditor’s note: This clause was originally indicated as an appendix in the draft output from the end-to-end QoS group.13.1 International Voice CallWhen devising SLA (service level agreements) of international voice calls for enterprise customers, international standards provide legal ground. The issue in this business is that the recommendation of 150ms delay (or latency) in one way (customer’s QoS requirements from mouth to ear connectivity) is enforced for an operator in concern for natural customer experience, and end user will suffer from longer delay than is acceptable. As indicated in Input Document I-011 submitted to the first Focus Group meeting, there are, however, two different relative standards for wireline and wireless networks respectively. ITU-T Recommendation Y.1541 specifies end-to-end delay to 100ms (excluding 50ms processing delays in both end terminals) for real-time voice application on QoS class 0 in wireline network as 3GPP TS 23.107 Rel.12 does so for conversational voice on QCI 1 in wireless network. The resulting delay of a voice call is likely to exceed the threshold of 150ms. When domestic wireless operator and an international wireline network operator maintain their QoS level at 90ms each, both of them have fulfilled their legal responsibility of SLA, but the end user will experience QoS of 180ms delay, which is not tolerable and is worse than the customer’s expectation (100ms). Since IMT-2020 network should consider some cases where services are provided over wireless and wireline networks of different operators, the current disparate standards on wireless and wireline networks are not suitable for providing customer QoS requirements. Therefore, a new standard applicable on both wireless and wireline networks is necessary for IMT-2020. 13.2 Domestic Video TelephonyWith the proliferation of smart devices and electronic devices, video telephony has become a common service for the public. Since smart devices are connected to the internet via WiFi and Cellular, and PC via wireline, integrated perspective (wireline & wireless) in domestic connectivity on QoS management is necessary for ensuring customer satisfaction of video telephony QoS. Video Telephony as used here implies a full-duplex system, carrying both video and audio intended for use in a conversational environment. As such, the same delay requirements as for conversational voice will apply in principle (i.e. no echo and minimal effect on conversational dynamics) with the added requirement that the audio and video must be synchronised within certain limits to provide "lip-synch". The quality of video must take into account the nature of human eye. Human eye is tolerant to some loss of information, so that some degree of packet loss is acceptable depending on the specific video coder and amount of error protection used. It is expected that the latest MPEG-4 video codecs will provide acceptable video quality with frame erasure rates up to about 1%. It should be noted that the QoS of video (in video telephony) may vary depending on compression ratio and application (i.e., real-time streaming, buffered streaming, real-time conversation, etc.), but the QoS threshold of voice should be 150ms as noted in 3.1. Regarding the QoS of video telephony, Input Document I-011 submitted to the first Focus Group meeting describes the definition by current standards. ITU-T Recommendation Y.1541 specifies end-to-end delay to 100ms (excluding 50ms processing delays in both end terminals) and 10-3 Packet Loss Ratio for real-time video telephony application on QoS class 0 in wireline network while 3GPP TS 23.107 Rel.12 does 150ms delay and 10-3 Packet Error Loss Rate for conversational video on QCI 2 in wireless network. The resulting delay of a voice call is likely to exceed the threshold of 150ms. When domestic service operator maintain their QoS level at 90ms for wireline and 120ms for wireless each, both of the networks have fulfilled their standard-based operation, but the end user will experience QoS of 210ms delay, which is not tolerable and is worse than the customer’s expectation (100ms). Since IMT-2020 network should consider the case where a service provided over wireless and wireline networks within a single operator, it is not suitable to apply current disparate standards within the operator. This calls for a new standard applicable on both wireless and wireline networks for IMT-2020. 13.3 Telecommunication services for Emergency/Disaster ReliefIn an emergency, available network resources are dramatically reduced and calls for a prioritization of communication requests. Some forms of communications, such as calls between disaster-related government agencies, have greater importance than others, or perform a more critical function than other forms of communication. Classifying priority classes and assigning relative priorities can help enhance efficient and timely use of network resources. In this case, however, a single standard encompassing wireless and wireline networks is necessary for ensuring consistent customer QoS requirement and enhancing operational efficiency in IMT-2020. In addition, some parts of the network (whether randomly located or concentrated) will be damaged and must be replaced by temporary measures during disaster. In this process, what used to be wireline network may be replaced by temporary wireless networks and the opposite may hold true. It is therefore essential to define the comprehensive (wireless & wireline) QoS requirements of disaster relief systems independent of the type of technologies/protocols across the network even during disasters. It should also be noted that communications during disaster take place in various forms such as voice, SMS/MMS and video streaming. These forms of communications need to satisfy very stringent QoS requirements; 1) exact location information of casualties, 2) relief instructions from control tower, 3) high-definition real-time video of the disaster site for first aid, etc. While cases similar to the ones presented in 3.1 and 3.2 will occur, communication may have to go through from a wireless network to wireline network in a single operator to another operator’s network. The worst case scenario will be going from an operator A’s wireless network to operator B’s wireless network via each operator’s wireline network. In this case, each operator and each network may maintain QoS level at 90ms, each fulfilling own legal responsibilities. Yet, the end users will perceive an overall delay of 360ms and it will be difficult to provide high-definition real-time forms of communications. Since current standards employ different QoS parameters (e.g., 3GPP defines the type of traffic, packet delay and packet loss while ITU-T Y.1541 defines IP packet delay, IP packet delay variation, IP packet loss and IP packet error), communication during disaster will increase complexity of operation and may lead to confusion of QoS management. In addition to a common QoS parameter, methods for QoS implementation (e.g., resource reservation and priority control) can also be matched. While cellular communications employ pre-emptive measures to guarantee QoS, wireline communications process priorities of individual packets. For consistent operation and management, it is recommended that a common QoS implementation method be applied over both wireline and wireless networks.
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