ITU-T H.362 PDF

There are various wireless networks including 2G/3G/4G mobile networks, wireless LANs, and mobile WiMAX networks. On the other hand, there are various multi-rate codecs including G.729.1, G.722.2, and H.264, which can provide variable bit rates and adaptability in the dynamic environment where the network status may change over time.

Networks are being evolved toward the converged network where heterogeneous wired/wireless access networks are converged using the IP-based core network. Fixed Mobile Convergence (FMC) and Fixed Mobile Substitution (FMS) are some examples. In such an environment, many of QoS control mechanisms are employed in the core/access networks to manage QoS resources efficiently. However, this type of QoS control may not be sufficient to meet the end users' expectation from the end-to-end QoS perspective because QoS control at the application level is not involved. To provide more complete end-to-end QoS, the application level QoS support can be useful. This is particularly important when the network is not able to support QoS. One of the possible application level QoS mechanisms is codec-based QoS control which adjusts encoding parameters such as codec bit rate or codec mode according to the network status, e.g., wireless channel status.

Various codec-based QoS mechanisms were proposed to control the codec bit rate and call capacity using the wireless channel information in diverse wireless networks. However, in the heterogeneous network environment, it is difficult to control QoS in a unified way and to achieve the desirable service quality. Therefore, it is useful to design a common framework to control the codec mode adaptively according to the channel status in wireless networks and reflect users' perceived quality. For achieving the objective, this Recommendation describes a framework for adaptive end-to-end QoS control using variable bit-rate codecs in wireless networks. Specifically, this Recommendation describes a reference network architecture, functional entities, references points, a terminal architecture, and signalling flows between functional entities. The stability of control loop and delayed feedback in the control path which may affect the service quality is important in such adaptive QoS control, however it is out of scope of this Recommendation.