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Introduction to Wireless

Introduction to Wireless. CS 477. Technologies. Transmission Techniques. Distributed/Hierarchical FDMA/TDMA/CDMA TDD/FDD. Network Types. Distributed Network: Users interface with each other Ad Hoc Network: Self-creating

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Introduction to Wireless

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  1. Introduction to Wireless CS 477

  2. Technologies

  3. Transmission Techniques Distributed/Hierarchical FDMA/TDMA/CDMA TDD/FDD

  4. Network Types • Distributed Network: Users interface with each other • Ad Hoc Network: Self-creating • Hierarchical network: Users interface with Base Station or Access Point • Polled: Master-Slave MT MT MT MT

  5. Hierarchical Networks Base Station Uplink Downlink Terminal Equipment

  6. Time Division Duplex (TDD) • Base Station & Terminal Equipment alternate transmissions • Good when amount of downlink data > amount of uplink data

  7. Frequency Division Multiple AccessFrequency Division Duplex (FDD) Example: First Generation Cellular

  8. Time Division Multiple Access TDMA - FDD

  9. Time Division Multiple Access • Channels allocated by Frequency & Timeslot • A Multiframe defines who & what transmits during a timeslot (E.g.:) • Broadcast / Paging / Synchronization Channel • Random Access Channel • Signaling Channels • Traffic Channel

  10. Frequency Hopped Spread Spectrum (FHSS)

  11. EDGE Technology

  12. EDGE Technology • Finds Optimal Bit Rate • Selects modulation & coding scheme based on environment • Uses Link Quality Control • Varies Modulation Scheme • GMSK, 8-PSK • Code Rate varies form .37 to 1.0

  13. EDGE Modulation & Coding

  14. Direct Sequence Spread Spectrum (DSSS) 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0

  15. Code Division Multiple Access (CDMA) • Each bit is transmitted multiple times at different frequencies, called ... • Direct Sequence Spread Spectrum • Fast Frequency Hopping • Message x spreading signal • Pseudo-noise code sequence @ chip rate • Codewords are orthogonal to each other • Interference Limited

  16. Multi-Carrier vs. Direct Sequence CDMA 2000 Technology Multi-Carrier Direct Sequence

  17. CDMA Enhancements CDMA2000: • Chip rates of N=1, 3, 6, 9, 12 • Reduced spreading • Turbo codes: 10-6 vs 10-3 • QPSK on Forward (v) Link • BPSK on Reverse (^)

  18. Spatial Diversity Multiple Access SDMA or Smart Antennas • Forms a focused beam • Allows channels to be reused within a cell • Multibeam Type • Multiple fixed beams with a narrow focus • Adaptive Array • Uses Spatial & Angle Diversity • Separates signal from its path

  19. SDMA

  20. Varied Cell Sizes megacell macrocell microcell picocell Diameter 0 100 m 2 km 70 km 200-1000km

  21. Frequency Allocations Licensed: Cellular, Satellite, WLL Unlicensed: WLAN, WPAN

  22. Licensed, Cellular Frequencies .824 - .894 US-DC, IS-95 .890 - .960 ETACS / NMT / GSM 1.71-1.88 DCS 1800 1.85-1.99 US-DC, IS-95 1.92-2.17 UMTS - W-CDMA

  23. Wireless Cable

  24. Wireless LAN / PAN IEEE 802.11B BLUETOOTH

  25. Wireless LAN • Unlicensed Frequencies • Low Maximum Transmit Power • Possible Contention Problems • Frequencies Used: • Industrial, Scientific, Manuf. (ISM): 2.4 GHz • Unlicenced Nat. Info. Infrastructure (UNII): • 5.2 GHz 300 MHz • 5.725 - 5.825 GHz

  26. IEEE 802.11B 192 us 1 Mbps Data: 1 of 4 rates Uses multiple subcarriers Header Training Data

  27. IEEE 802.11 Hidden Terminal Simultaneous Transmissions Possible

  28. CSMA/CA MT C MT A MT B RTS CTS Data ACK

  29. IEEE 802.11 Protocol S I F S P I F S D IFS

  30. IEEE 802.11 Protocol • Possible Simultaneous TX • CSMA/CA • RTS/CTS notifies all in area of TX • SIFS: Short delay before ack. • PIFS: Poll time-sensitive data • Point Coordinator polls for high priority • DIFS: Anyone may contend to TX

  31. Bluetooth Personal Area Network Radio-based cable replacement • Low-cost, low-power • Created by IBM, Intel, Ericsson, Nokia, Toshiba in Feb. ‘98 • Joined by Motorola, Lucent, Microsoft, 3COM Features • Piconet: Swaps data at up to 10 meters • Data Rate: 721 kbps to 1 Mbps, or 3 Voice @ 64 kbps

  32. Bluetooth Applications • Cordless desktop with peripherals • Cordless phone • LAN Access - Internet bridge • File Transfer: PDA synchronization with PC • Headset / Intercom / Dial up network • Home entertainment, lighting, security

  33. Bluetooth Protocol • IEEE 802.15 Standard defines layers 1 & 2 • ISM Band: 2.4 GHz • Spread spectrum: FHSS • 1 Master polls up to 7 Slaves • Auto-initiation of updates

  34. Cellular Systems

  35. Functions of 2G Network • Cell Search • Location Update • Speech Calls • Mobile Originated Call • Paging: Mobile Terminated Call • Handover • Hard Handover • Soft Handover • Short Message Service

  36. Features of 3G Cellular • Bit rates to 2 Mbps • Variable Bit Rate • Multiple services multiplexed on single connection: voice, video, packet data • Real time and Best Effort traffic • FER: 10% to 10-6 • Handovers between 2G & 3G systems • Asymmetric uplink and downlink

  37. Services

  38. Network Architecture Universal Mobile Telecommunications System (UMTS)

  39. Control Plane: Radio Resource Control Mobility Mgmt Call Control User Plane: Speech Circuit-Switched Data Packet-Switched Data Vocabulary

  40. High Level System Architecture Uu Iu User Equipment (UE) UMTS Terrestrial Radio Access Network (UTRAN) Core Network (CN)

  41. User Equipment Uu Iu UMTS Terrestrial Radio Access Network (UTRAN) Core Network (CN) Mobile Equip. USIM Subscriber Identity Module

  42. Radio Interface Protocols Control Plane Protocols User Plane Protocols Radio Link Control Logical Channels Medium Access Control Transport Channels Physical Layer

  43. Logical Channels Control Channels: • Broadcast Control (BCCH): Downlink broadcasts system information • Paging Control (PCCH): Downlink incoming call info. • Dedicated Control (DCCH): Bidirectional control info (inside call) • Common Control (CCCH): Bidirectional control info (outside call)

  44. Logical Channels Traffic Channels: • Dedicated Traffic (DTCH): Bidirectional point-to-point dedicated channel • Common Traffic (CTCH): Downlink point-to-multipoint channel

  45. Radio Link Control Layer 2: • Transparent: No protocol • Unacknowledged Mode • Acknowledged Mode

  46. UTRAN Uu Iu Core Network (CN) Node B Mobile Equip. RNC Node B Node B USIM Subscriber Identity Module RNC Node B

  47. UTRAN Protocols Uses ATM base: • ATM AAL5: Control • ATM AAL2: Speech • RANAP: Radio Access Network Application Protocol

  48. Core Network Uu Iu PSTN Node B GMSC MSC/ VLR Mobile Equip. RNC Node B HLR Node B USIM Subscriber Identity Module RNC Internet SGSN GGSN Node B

  49. Core Network Nodes • Circuit-Switched: • Mobile Switching Center (MSC): switches PCM speech • Packet-Switched: • Serving GPRS Support Node (SGSN) • Gateway Support Node (GGSN): Interface to global Internet • Common • Home Location Register (HLR): Permanent source of subscription information • Visitor Location Register (VLR): Local source for user subscription options

  50. GPRS Network Architecture Serving GPRS Support Node (SGSN) • Interfaces with MS via BS • Performs security, mobility / VLR functions Gateway GPRS Support Node (GGSN) • Interfaces to Internet • Learns MS location via HLR • Routes data to the SGSN using IP Network is evolving as 3G/4G progresses

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