(ví dụ, phương tiện truyền thông mã hóa) - € "proï ¬ le cho dữ liệu âm thanh và video có thể được tìm thấy trong đồng RFC3551 [27], định dạng tải trọng speciï ¬ cation tài liệu, mà dei ¬ ne một tải trọng đặc biệt, chẳng hạn như âm thanh hoặc mã hóa video được thực hiện trong RTP . | 118 Multimedia Control Protocols for Wireless Networks m audio 0 RTP AVP 98 a control trackID 5 a 3GPP-QoE-Metrics Corruption Duration rate 20 The session level QoE field indicates that the initial buffering and the rebuffering duration should be monitored and reported once at the end of the session. The video specific metrics decoded bytes will be reported every 15 seconds until 40 seconds of NPT time. Finally audio specific metrics corruption duration will be reported every 20 seconds during all the session. A QoE aware client that receives a SDP description with QoE metrics fields may continue the negotiation with a SETUP request that includes a 3GPP-QoE-Metrics. This header allows the client to propose QoE metrics modifications. The value of the header can contain session and media metrics separated with the session-level and media-level URLs 3GPP-QoE-Metrics url rtsp trackID 3 metrics Decoded Bytes rate 10 range npt 0-4 0 url rtsp metrics Rebuffering_Duration rate End The server can accept the modifications of the client echoing them in the SETUP response or the server can deny modifications continuing the re-negotiation until the PLAY request. QoE metrics reports can be disabled by the server using SET_PARAMETER requests with the 3GPP-QoE-Metrics header containing Off . To send QoE metrics feedback the client will issue SET_PARAMETER requests with the 3GPP-QoE-Feedback header 3GPP-QoE-Feedback url rtsp trackID 5 Corruption_Duration 200 1300 Research Challenges and Opportunities As the user might have noticed the work in control protocols for multimedia communications is far from complete. In particular during the last few years with the advent of wireless and mobile networks a lot of new modifications and enhancements are being engineered to fulfill the wide range of new requirements that these networks are bringing up. In addition future 4G wireless networks consisting of IP core networks to
