David A. Burgess's Presentation at eComm 2009


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  • David A. Burgess's Presentation at eComm 2009

    1. 1. OpenBTS (demo) David A. Burgess, Kestrel Signal Processing, Inc.
    2. 2. What You are About to See • Hybrid GSM/SIP wireless access point. • AP looks like a GSM network to GSM handsets. • AP looks like Asterisk to IP network. • Handsets treated as SIP endpoints. • Bigger picture? Other aspects? • http://www.kestrelsp.com/OpenBTS • http://openbts.blogspot.com • http://gnuradio.org/trac/wiki/OpenBTS • Find us at the conference: • David A. Burgess • Harvind S. Samra
    3. 3. “Phase 2” GSM Core Network (GSM 03.02 version 7.1.0 Release 1998) 18 ETSI TS 100 522 V7.1.0 (2000-02) • From GSM 03.01. • The key pieces: • MS - Mobile station. • BTS - Base transceiver subsystem (Um L1/L2). • BSC - Basestation controller (L3 RR) • MSC - Mobile switching center (L3 CC). • HLR/VLR - Location registers (L3 MM). • Must have all 5!
    4. 4. OpenBTS Core Network • Peer-to-peer APs. PSTN SS7 • No BSCs, no MSCs, gateway VoIP Carrier no hair-pinning. SIP • Network interface is Provisioning mostly Asterisk. SQL packet-switced network Database (distributed) • Network can be as SIP SIP small as a single SQL SIP SQL SQL node, but with a OpenBTS OpenBTS AP AP range of 35 km. Hybrid OpenBTS GSM/SIP AP Access Point air interface, Um MS Any GSM Handset
    5. 5. Advantages of Peering • Core network is commodity IP switching equipment. • Minimum viable network is a single AP. • Low cost of entry for a small operator. • “Bare dirt” infrastructure. • Low power; solar/wind. • Any IP backhaul; low bit rates with GSM codecs. • Very robust. • Every AP or collection of APs is service area. • “Islands” continue to function locally. • “Islands” continue to function globally if they can route enough packets to the public internet.
    6. 6. Proposed Applications • Big vision: “Base of the Pyramid”. • Rural WLL at the lowest possible cost. • Our target is US$1/mo with US$5 handset. • Near-term markets to fund the work. • Isolated facilities (oil rigs, cruise ships, airliners, etc.) • Disaster relief (rapid deployment, scant infrastructure) • Test equipment (network simulation, handset testing) • Femtocells • GPL alternative to Vanu • Can replace hybrid L3 with A-over-IP interface. • Avoid vendor lock with open source.
    7. 7. OpenBTS AP Architecture • Local RR. • Map MM GSM GSM Handset GSM Handset GSM and CC in Handset quot;Umquot;, Handsets Analog the GSM RF USRP RF Gear Air Interface L3. • Handsets time-tagged USB pckets are SIP Software GMSK endpoints. Radiomodem • 10k lines SQL time-tagged SQL GSM bursts Private of C++ in or Public IP Network SIP, highlighted IAX, etc. Hybrid GSM/SIP soft GSM Stack box. SIP Control Layer Abis (L1, L2) (L3)
    8. 8. Demo particulars. • Operating in GSM900 band to avoid contention. • MCC=901, MNC=55 • ARFCN 29 (940.8 MHz down, 895.8 MHz up) • No BTS tx antenna, just leakage, <30 mW. • Did your quad-band phone get a text? Well, that’s your fault. • Handsets are unmodified refurbs. • Mostly old Nokias with AT&T SIMs. • Some have real DID E.164’s in Solano County, California and Amsterdam. • Volunteers? • Thanks to Lee Dryburgh, John Gilmore, GNU Radio.
    9. 9. The Perfect Test Site • Black Rock City, the 5th largest city in Nevada, has no cellular coverage. • But 50,000 people bring their phones.
    10. 10. Camp WD9XKN @ 3:15 & G, BRC • What it looks Preamps Uplink like when you Duplexer Filter Power Amp PAP2 Adapter and build a BTS Test Equipment Host Laptop Wired Phone for on Ice Pack Testing USRP from eBay and Home Depot. • Going again in 2009 with better SW, better HW and SMS.