Fall Forum -- Keystone, Colorado USA -- November, 1999

H.324M: Overview & Update Marko Luomi, Senthil Sengodan Nokia

Fall Forum -- Keystone, Colorado USA -- November, 1999 Outline  H.324M Motivation & Requirement  H.324M Standard  Future Directions

Fall Forum -- Keystone, Colorado USA -- November, 1999 H.324M in ITU-T  H.324M has been developed in the ITU-T SG16 Q11 Mobile Group  The members of the group have been:  universities,  mobile network operators,  mobile terminal manufacturers as well as  PSTN H.324 vendors etc.

Fall Forum -- Keystone, Colorado USA -- November, 1999 Why H.324M?  H.324 is a bandwidth efficient solution for circuit- switched multimedia communications.  Increasing data rates enable the usage of H.324 in "2G mobile networks (such as GSM, IS-136, and IS-95), 3G mobile networks, DECT, etc."  However, other characteristics of the networks like bit error rate and delay differ from PSTN.  Therefore changes were required to adopt H.324 to mobile environment.

Fall Forum -- Keystone, Colorado USA -- November, 1999 What H.324M Is?  In terms of standards:  It is an extension to H.324.  Annex C of ITU-T Recommendation H.324: “Terminal for low bit rate multimedia communication”.  ITU-T Recommendation H Annex A: “Multiplexing protocol for low bit rate multimedia mobile communication over low error-prone channels”.  ITU-T Recommendation H Annex B: “Multiplexing protocol for low bit rate multimedia mobile communication over moderate error-prone channels”.  ITU-T Recommendation H Annex C: “Multiplexing protocol for low bit rate multimedia mobile communication over highly error-phone channels”.  ITU-T Recommendation H.223 — Annex D: “Optional multiplexing protocol for low bit rate multimedia communication over highly error-prone channels”.  The relevant parts of the ITU-T Recommendation H.245, version 3: “Control protocol for multimedia communication”.

Fall Forum -- Keystone, Colorado USA -- November, 1999 What H.324M Is?  H.324M is backward compatible with H.324.  In terms of functionalities:  H.324M provides a toolbox to enhance the error robustness of the H.223 multiplexer.  In the Annex A the HDLC flag used to delimit multiplex packets in H.223 is replaced with a longer flag and HDLC bit stuffing is not used.  In addition to previous, the multiplex header is more error robust and packet length field is introduced in Annex B.  In addition to previous, forward error correction is applied to the payload in the Annexes C and D.

Fall Forum -- Keystone, Colorado USA -- November, 1999 What H.324M Is?  At the beginning of the connection terminals select the highest common level.  Later the used level can be changed dynamically.  Addition to changes to the multiplexer a Control Channel Segmentation and Reassembly Layer (CCSRL) was introduced to ensure the faster transfer of control information in error prone environment.  Possibility to use codecs suitable for mobile environment like GSM AMR speech codec and MPEG4 visual.

Fall Forum -- Keystone, Colorado USA -- November, 1999 Related Activities  Co-operation with ITU-T SG16 Q15:  support error resilience improvements to the H.263 video codec, and  create a realistic simulation model for video error resilience experiments.  Interoperability experiments:  Interoperability group has tested all new main functionalities introduced by H.324M.  Initiative has been done to sift these tests under the IMTC H.324 test group.  3 rd Generation Partnership Project (3GPP) uses H.324M as a basis for circuit-switched multimedia telephony service.

Fall Forum -- Keystone, Colorado USA -- November, 1999 Current Status of Standards  Annex C of H.324, decided  Annexes A, B, and C of H.223, decided  Annex D of H.223, determined  H.245 version 5, determined

Fall Forum -- Keystone, Colorado USA -- November, 1999 Future Activities  Continue improvements to video quality in the mobile environment in coordination with ITU-T SG16 Q.15.  Work on new methods for unequal error protection strategies between systems and video.  Develop Mobile Multilink