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Satelitt kommunikasjon

Kapittel 13 Tord I. R. Satelitt kommunikasjon. Overview. Satellite overview + Iridium Digital Video Broadcasting Forward link (MPEG-2 Transport stream) Return link (Channel Access) QoS. References. Ganz A. Et al., Multimedia Wireless Networks ETSI EN 301 790 v1.3.1

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Satelitt kommunikasjon

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  1. Kapittel 13 Tord I. R. Satelitt kommunikasjon

  2. Overview • Satellite overview + Iridium • Digital Video Broadcasting • Forward link (MPEG-2 Transport stream) • Return link (Channel Access) • QoS

  3. References • Ganz A. Et al., Multimedia Wireless Networks • ETSI EN 301 790 v1.3.1 • ETSI TR 101 790 v1.2.1 • http://www.abo.fi/~jbjorkqv/digitv/lect4.pdfThe DVB transport stream • http://www2.sis.pitt.edu/~jkabara/tele-2100/iridium/iridium_final.htmlIridium tutorial

  4. Orbits • GEO Geosyncronous Earth Orbit (36000 km)Thuyara, Inmarsat. • MEO Middle Earth Orbit (10000 km)ICO • LEO Low Earth Orbit (ca 700-1600km)Large: Iridium, GlobalstarSmall: Orbcomm, Teledesic. • Propagation delay (one way) 2.6 – 167 ms. • Ku band (10-17 GHz) • Ka band (18-31 GHz)

  5. Iridium • 66 satellites, 700 km orbit, costs $62 mill. 700 kg. Each sattellite covers 4350 km diameter with 48 beams. • 12 gateways located around the world. • Phone to satellite 1616 – 1626.5MHz, 2.4 kbps. • Satellite to satellite/gateway 23GHz, 19GHz downlik, 29GHz uplink. • Iridium follows the GSM architecture.

  6. Digital Video Broadcasting (DVB) • Multimedia Wireless Networks focuses only on DVB. • ETSI EN 301 790 • ETSI TR 101 790 • Dish size: 0.6 to 1.2m. • Up link (Return link) 150kbps-380kbps-2Mbps. • Down link (Forward link) 38Mbps.

  7. DVB Return channel system

  8. NCC-Satellite-RCST • NCC – Network core controll • RCST – Return Channel Satellite Terminal

  9. Forward link / Broadcast channel • MPEG-2 Transport Stream • Several transport streams are multiplexed on MPEG-2 TS • DVB data piping • DVB data streaming • DVB multiprotocol encapsulation • DVB data carousel • DVB object carousel

  10. Return Link • All RCST transmissions are controlled by the NCC. • The NCC broadcasts a Terninal Burst Time Plan (TBTP) for each superframe, indicating when each RCST can send data. The RCST are identified by channel id. • The TBTP is based on demand and QoS requirements. • A time slot is identified with superframe id, superframe counter, frame number and timeslot number. • Data are sent with fixed- or dynamic-slot MF-TDMA

  11. MF-TDMA

  12. QoS • All transmissions are controlled by the NCC • Capacity requests are categorized into 5 categories: • Continuous rate assignment (CRA) Fixed min. Bandw. (constant bit rate applications). • Rate-based dynamic capacity (RBDC) dynamic per superframe. (variable bit rate applications). • Volume-based dynamic capacity (VBDC) cumulateive requests (variable bit rate, delay tolerant applications). • Absolute volume-based dynamic capacity (AVBDC) none-cumulative VBDC. • Free Capacity Assignment (FCA) (best effort)

  13. QoS • Signaling method for capacity requests: • Satellite access control (SAC) field. A SYNC contains an optional SAC field. • Data unit labeling method (DULM). Piggybacked on the assigned periods of TRF traffic. • Mini-slot method. Logged-on units that use less than the full traffic slots. • Contention-based mini slot method. Accessed mini-slot on a contention basis, uses slotted aloha for back off.

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