行動網際網路電話之研製與實現
Outline 緒論 相關技術背景之探討 軟體實現行動網際網路電話系統 相關演算法探討 未來展望
緒論 寬頻網路 多媒體資料 封包交換 vs 電路交換
相關技術背景之探討
SIP RFC 2543, March 1999 RFC 3261, June 2002 Function Find Out IP Address(Location) of use Session Initiation Session Management
SIP Architecture
SIP Messages Request Messages TypeDescription REGISTERRegisters the user agent INVITEInitiates a call by inviting user to participate in session ACKConfirms that the client has received a final response to an INVITE request CANCELCancels a pending request BYEIndicates termination of the call OPTIONSUsed to query the capabilities of a server “ The SIP INFO Method ”, RFC 2976, October “ The Session Initiation Protocol (SIP) UPDATE Method ”, RFC 3311, September 2002.
SIP Response Messages Response Messages TypeDescription 1xxInformational Responses ex. 180 Ringing 2xxSuccessful Responses ex. 200 OK 3xxRedirection Responses ex. 302 Moved Temporarily 4xxRequest Failure Responses ex. 404 Not Found 5xxServer Failure Responses ex. 503 Service Unavailable 6xxGlobal Failures Responses ex. 600 Busy Everywhere
SIP Operation
RTP RFC 1889, January 1996 RFC 3550, July 2003 Function 傳送即時性的資料
RTP Packet Format
RTP Packet Format - A/V Profile PTEncoding Name Audio/Video (A/V) Clock Rate (Hz) Channels (Audio Only) 0PCMUA A G721A GSMA unassignedA DVI4A DVI4A LPCA PCMAA G722A80001
RTP Packet Format - Timestamp
RTP Packet Format - CSRC
RTP Packet Format - Extension
RTP Packet Format - Payload Data & Padding Counter
RTCP Packet Types Packet TypeDescriptionValue SRsender report200 RRreceiver report201 SDESsource description item202 BYEindicates end of participation203 APPapplication-specific functions204
RTCP Packet Format - SR
RTCP Packet Format – SR & Interarrival jitter D(i,j) = (Rj – Sj) – (Ri – Si) Ji = Ji-1 + ( | D(i-1,i)| – Ji-1)/16
RTCP Packet Format - RR
RTCP Packet Format - SDES
RTCP Packet Format – SDES ITEM Format & Type SDES TypeDescriptionValue ENDend of SDES item list0 CNAMEcanonical name1 NAMEuser name2 user ’ s electronic mail address 3 PHONE user ’ s phone number 4 LOCgeographic user location5 TOOLname of application or tool6 NOTEnotice about the source7 PRIVprivate extensions8
RTCP Packet Format – BYE
RTCP Packet Format – APP
軟體實現行動網際網路電話系統
Proxy Sever System
UA System
UA System - UUS
UA System - RRS
UA System - EDS
UA System - WSS
相關演算法探討 (a) PCM (b) ADPCM
相關演算法探討 Item DescriptionPCMADPCM 頻寬需求高約 PCM 的四分之一 語音品質佳差 演算法設計較易較難
相關演算法探討 Item Description 聽覺評估法傳輸率評估法 反應速度較快較慢 客觀性較主觀較客觀 演算法設計較易需額外的判斷
未來展望 更多種類的多媒體資料傳送 異質網路的整合 穿越防火牆 (Firewall) 與網路位址轉換 (NAT) 能力的 SIP