1 / 27

Event-based Radio Communication Signaling using the Session Initiation Protocol

Event-based Radio Communication Signaling using the Session Initiation Protocol. Klaus Darilion. Radio Communication. like walkie talkies transmit a radio message press the “push-to-talk” button (PTT) incoming radio message squelch indicator (SQU)  2 signals PTT SQU.

myard
Download Presentation

Event-based Radio Communication Signaling using the Session Initiation Protocol

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Event-based Radio Communication Signaling using the Session Initiation Protocol Klaus Darilion

  2. Radio Communication • like walkie talkies • transmit a radio message • press the “push-to-talk” button (PTT) • incoming radio message • squelch indicator (SQU) •  2 signals • PTT • SQU

  3. Radio Communication Properties • radio devices • usually amplitude modulated radios • shared medium (collisions) • listen before talk • half-duplex • “push-to-talk” powers up the transmitter • squelch indicates incoming radio messages • area of application • air traffic control • public safety

  4. Split Audio from Radio Part • transmitter • receiver wired connection audio + PTT/SQU • loudspeaker • microphone • PTT button

  5. e.g. Air Traffic Control wired circuit switched network phones gateways operator positions

  6. Push-To-Talk/Squelch Signaling SQU PTT operator positions

  7. IP based Voice Communication System ATC Center wired network • wired IP network • LAN: switched Fast Ethernet • WAN: depends on the service provider • SIP for session signaling • RTP for voice transmission gateways operator positions

  8. What is it not this work does not … • … change the radio communication • radio link is still based on existing analogue radios •  no IP/SIP over the radio link this work is similar to ... • … push-to-talk over cellular (PoC) for 3GPP • … but different requirements

  9. Radio Architecture • radio senders and receivers • radio gateways • radio servers • operator positions Air Traffic Control Center Radio Gateway + Radio IP Operator Position Operator Position 4-wire Radio Gateway Operator Position Radio Radio Server

  10. Radio Architecture Components • radio senders and receivers • typically on remote sites • one voice channel per radio • the bandwidth of the connection between the remote site and the ATC centre is dimensioned for one voice stream per radio. • radio gateway • translates the SIP signaling to radio control lines • translates RTP audio packets to analogue audio • radio server in the LAN • manages the access to the radios (shared resource) • distributes the received radio messages

  11. Interconnecting • transparent interconnecting via IP WAN connections • sharing of remote resources (radios, data services…)

  12. PTT/SQU Signaling • event based • send signal on status changes • signals the beginning and the end of a radio message • delivery must be reliable • continuous • current status will be signaled continuous in small periodic intervals • reliable transport not required

  13. PTT/SQU Signaling • event based – out-band signaling • SIP • independent from audio stream • reliable • RTCP • unreliable  retransmission mechanism • APP packets (like PoC) • continuous – in-band signaling • RTP • extension header • increased traffic (WAN) • setting up an audio stream is necessary

  14. SIP-based Event Notification • RFC 3265 – SIP-Specific Event Notification • framework for event subscription and notification • PTT/SQU event package for radio communication

  15. 2b. NOTIFY operator@pc12.atc-center.org SIP/2.0 SIP/2.0 200 OK Radio Server SIP-based Event Notification • subscription traverses proxies • notifications will be sent directly 2a. NOTIFY operator@pc11.atc-center.org SIP/2.0 Operator Position SIP Proxy SIP/2.0 200 OK 1. NOTIFY operator@pc12.atc-center.org SIP/2.0 SIP/2.0 200 OK Operator Position Radio Gateway

  16. Squelch Notification NOTIFY sip:operator12@pc44.atc-center.org SIP/2.0 Via: SIP/2.0/UDP 128.131.80.6:5062 From: “radio34" <sip:radio34@atc-center.org>;tag=F68 To: “operator12" <sip:operator12@atc-center.org>;tag=1ec23337 Contact: “radio34" <sip:radio34@128.131.80.6:5062;transport=udp> Call-ID: 3c9196445d5240bfb7b660a16ee6d390@128.131.80.223 CSeq: 522 NOTIFY Event: PTT/SQU Content-Type: text/plain Content-Length: 76 radio=sip:radio34@atc-center.org sector=sip:f100@atc-center.org status=SQU-on

  17. Combined Services • define services on top of existing services • using existing protocols

  18. Sector Subscription Model • Status state • only status information about this channel without any voice • SUBSCRIBE • Rx state • status information • passive listener to the channel • INVITE, a=recvonly • Tx+Rx state • status information • listener to the radio channel • transmit radio messages • INVITE, a=sendrecv • every state transition corresponds with a SIP transaction

  19. Push-To-Talk Signaling • radio server • grants access to sector • distributes PTT signal

  20. Implementation • Linux based prototype • SIP-stack • dissipate2 (kphone) • 2.5ms for every NOTIFY transaction • RTP-stack • jrtplib

  21. Conclusion • maximum 25 ms for PTT signaling • easy to achieve for operator – gateway signaling • hard to achieve for operator – operator signaling • hard to compare – existing requirements are trimmed for circuit switched systems • SIP: one protocol for phone and radio communication • compatibility with devices which do not support all SIP extensions (e.g. SIP phones) • open standard guarantees interoperability between different vendors and extensibility of ATC services • transparent interconnecting of ATC centers via IP WAN connection

  22. Future Work • WAN measurements • additional PTT signaling delay • fast and reliable transport of the voice packets • especially bandwidth reservation for WANs • interaction of QoS mechanisms with SIP • high priority calls may disrupt normal calls • enhanced radio services • coupling, coverage

  23. Converged Services • e.g. weather data  synthesized radio message

  24. Thank You! • slides at: • http://www.ict.tuwien.ac.at/darilion/sip04.zip • email: • darilion@ict.tuwien.ac.at

  25. Comparison with PoC AM (real collision domain) GPRS/UMTS PoC server (virtual collision domain) wired

  26. Measurements: PTT Signaling • operator presses PTT • operator position signals PTT to radio server • NOTIFY, body: status=PTT-on • radio server forwards event to • the radio gateway • all subscribed operators

  27. Measurements: PTT Signaling processing between timemessages tOK – receiving PTT notification 6.4 ms 1 – 2 tforw – PTT forwarding (tgen + treceive) 9.5 ms 1 – 3a tsend – repetitive notification sending 2.5 ms 3a – 3b n = 3  tPTT = 24 ms

More Related