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Spectral Allocation

Explore the evolution of wireless systems, including cellular, WLANs, and technology enhancements like better hardware and dynamic resource allocation.

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Spectral Allocation

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  1. Spectral Allocation

  2. Evolution of Current Systems • Wireless systems today • 2G + 2.5G Cellular: ~30-70 Kb/s. • WLANs: ~10 Mb/s. • Next Generation • 2.75G + 3G Cellular: ~300 Kb/s. • WLANs: ~70 Mb/s. • Technology Enhancements • Hardware: Better batteries. Better circuits/processors. Co-optimization with transmission schemes. • Link: Antennas, modulation, coding, adaptivity, DSP, BW. • Network: Dynamic resource allocation, Mobility support.

  3. 2.5G – Upgrade options • GSM • High Speed Circuit Switched Data (HSCSD) • General Packet Radio Service (GPRS) • Enhanced Data rate for GSM Evolution (EDGE) • IS-95 • IS-95A provides data rates up to 14.4 kbps • IS-95B provides rates up to 64 kbps (2.5G)

  4. 3G Vision • Universal global roaming • Multimedia (voice, data & video) • Increased data rates • 384 kbps while moving • 2 Mbps when stationary at specific locations • Increased capacity (more spectrally efficient) • IP architecture • Problems • No killer application for wireless data as yet • Vendor-driven

  5. Migration To 3G

  6. CDMA2000 Pros and Cons • Evolution from original Qualcomm CDMA • Now known as cdmaOne or IS-95 • Better migration story from 2G to 3G • cdmaOne operators don’t need additional spectrum • 1xEVD0 promises higher data rates than UMTS, i.e. W-CDMA • Better spectral efficiency than W-CDMA(?) • Arguable (and argued!) • CDMA2000 core network less mature • cdmaOne interfaces were vendor-specific • Hopefully CDMA2000 vendors will comply w/ 3GPP2

  7. W-CDMA (UMTS) Pros and Cons • Wideband CDMA • Standard for Universal Mobile Telephone Service (UMTS) • Committed standard for Europe and likely migration path for other GSM operators • Leverages GSM’s dominant position • Requires substantial new spectrum • 5 MHz each way (symmetric) • Legally mandated in Europe and elsewhere • Sales of new spectrum completed in Europe • At prices that now seem exorbitant

  8. TD-SCDMA • Time division duplex (TDD) • Chinese development • Will be deployed in China • Good match for asymmetrical traffic! • Single spectral band (1.6 MHz) possible • Costs relatively low • Handset smaller and may cost less • Power consumption lower • TDD has the highest spectrum efficiency • Power amplifiers must be very linear • Relatively hard to meet specifications

  9. Current Wireless Systems • Cellular Systems • Wireless LANs (802.11a/b/g, Wi-Fi) • Satellite Systems • Paging Systems • Bluetooth • Ultrawideband radios (UWB) • Zigbee/802.15.4 radios • WiMAX (802.16)

  10. 1011 0101 01011011 Internet Access Point Wireless Local Area Networks (WLANs) • WLANs connect “local” computers (~100 m range) • Breaks data into packets • Channel access is shared (random access) • Backbone Internet provides best-effort service • Poor performance in some app’s (e.g. video)

  11. In future all WLAN cards will have all 3 standards... Wireless LAN Standards (Wi-Fi) • 802.11b (Current Generation) • Standard for 2.4GHz ISM band (bw 80 MHz) • Frequency hopped spread spectrum • 1.6-10 Mbps, 500 ft range • 802.11a (Emerging Generation) • Standard for 5GHz NII band (bw 300 MHz) • OFDM with time division • 20-70 Mbps, variable range • Similar to HiperLAN in Europe • 802.11g (New Standard) • Standard in both 2.4 GHz and 5 GHz bands • OFDM (multicarrier modulation) • Speeds up to 54 Mbps

  12. HIPERLAN • Types 1-4 for different user types - Frequency bands: 5.15-5.3 GHz, 17.1- 17.3 GHz • Type 1 - 5.15-5.3 GHz band - 23 Mbps, 20 MHz Channels - 150 foot range (local access only) - Protocol support similar to 802.11 - Peer to peer architecture - ALOHA channel access • Types 2-3 - Wireless ATM - Local access and wide area services - Standard under development - Two components: access and mobility support 8C32810.63a-Cimini-7/98

  13. Satellite Systems • Cover very large areas • Different orbit heights • GEOs (39000 Km) via MEOs to LEOs (2000 Km) • Trade-off between coverage, rate, and power budget! • Optimized for one-way transmission: • Radio (e.g. DAB) and movie (SatTV) broadcasting • Most two-way systems struggling or bankrupt... • (Too) expensive alternative to terrestrial systems • (But: a few ambitious systems on the horizon)

  14. Satellite networks: GEO Japan Singapore GEO Gateway Gateway Control station Control station Public networks Public networks

  15. Satellite networks: LEO Japan Singapore LEO LEO Inter-satellite link Gateway Gateway Control station Control station Public networks Public networks

  16. Paging towers PSTN Paging Control center Paging towers Paging Systems • Simplex • Limited to worldwide coverage possible • Broadcast / simulcast • Reliable  large Txd. Power, Low data rate

  17. Other Wireless Systems • Cordless telephone systems • Dedicated Base Station • Limited coverage • No handoff support PSTN Fixed Base Station

  18. A general WLL setup

  19. Bluetooth • A new global standard for data and voice Cable replacement RF technology • Short range (10 meters) • 2.4 GHz band • 1 Data (700 Kbps) and 3 Voice channels • Supported by over 200 telecommunications and computer companies • Goodbye Cables !

  20. Ultimate Headset

  21. Cordless Computer

  22. Automatic Synchronization In the Office At Home

  23. Bluetooth Specifications

  24. UltraWideband Radio (UWB) • Impulse radio: sends pulses of tens of picoseconds (10-12) to nanoseconds (10-9) - duty cycle of only a fraction of a percent • Uses a lot of bandwidth (order of GHz) • Low probability of detection by others + beneficial interference properties: low transmit power (density) spread over wide bandwidth • This also results in short range. • But : Excellent positioning (ranging) capability + potential of high data rates • Multipath highly resolvable: both good and bad • Can use e.g. OFDM or equalization to get around multipath problem.

  25. Why is UWB interesting? • Unique Location and Positioning properties • 1 cm accuracy possible • Low Power CMOS transmitters • 100 times lower than Bluetooth for same range/data rate • Very high data rates possible (although low spectral efficiency) - 500 Mbps at ~10 feet range under current regulations • 7.5 Ghz of “free spectrum” in the U.S. • FCC (Federal Communications Commission) recently legalized UWB for commercial use in the US • Spectrum allocation overlays existing users, but allowed power level is very low, to minimize interference • “Moore’s Law Radio” • Data rate scales with the shorter pulse widths made possible with ever faster CMOS circuits

  26. IEEE 802.15.4/ZigBee radios • Low-Rate WPAN (Wireless Personal Area Network) - for communications < 30 meters. • Data rates of 20, 40, 250 kbps • Star topology or peer-to-peer operation, up to 255 devices/nodes per network • Support for low-latency devices • CSMA-CA (carrier sense multiple access with collision avoidance) channel access • Very low power consumption: targets sensor networks (battery-driven nodes, lifetime maximization) • Frequency of operation in ISM bands

  27. WiMAX: Worldwide Interoperability for Microwave Access • Standards-based (PHY layer: IEEE 802.16 Wireless MAN family/ETSI HiperMAN) technology, enabling delivery of ”last mile” (outdoor) wireless broadband access, as an alternative to cable and DSL (MAN = Metropolitan Area Network). Several bands possible. • OFDM-based adaptive modulation, 256 subchannels. TDM(A)-based. Antenna diversity/MIMO capability. Advanced coding + HARQ. • Fixed, nomadic, portable, and mobile wireless broadband connectivity without the need for direct line-of-sight (LOS) to base station. • In a typical cell radius deployment of 3 to 10 kms, expected to deliver capacities of up to 40 Mbps per channel, for fixed and portable access. • Mobile network deployments are expected to provide up to 15 Mbps of capacity within a typical cell radius deployment of up to 3 kms. • WiMAX technology already has been incorporated in some notebook computers and PDAs. Potentially important part of 4G?

  28. 100 Mbit/sec UWB 802.11g 802.11a 802.11b 10 Mbit/sec 1 Mbit/sec 3G Bluetooth 100 kbits/sec ZigBee ZigBee UWB 10 kbits/sec 0 GHz 1GHz 2 GHz 3 GHz 4 GHz 5 GHz 6 GHz Frequencies occupied Data rate

  29. 10 km 3G 1 km 100 m 802.11a 802.11b,g Bluetooth 10 m ZigBee ZigBee UWB UWB 1 m 0 GHz 1GHz 2 GHz 3 GHz 4 GHz 5 GHz 6 GHz Range

  30. 10 W 802.11a 802.11bg 3G 1 W 100 mW Bluetooth UWB ZigBee 10 mW ZigBee UWB 1 mW 0 GHz 1GHz 2 GHz 3 GHz 4 GHz 5 GHz 6 GHz Power Dissipation

  31. Emerging Systems • Ad hoc wireless networks • Sensor networks • Distributed control networks

  32. Ad-Hoc Networks • Peer-to-peer communications. • No backbone infrastructure (no base stations). • i.e. “Truly wireless”! • Routing can be multihop. • Topology is dynamic in time; networks self-organize. • No centralized cooordination. • Fully connected, even with different link SINRs (signal-to-interference plus noise ratios)

  33. Nodes typically powered by nonrechargeable batteries. Data (sensor measurements) flow to one centralized location (sink node, data fusion center). Low per-node rates - but up to 100,000 nodes. Sensor data highly correlated in time and space. Nodes can cooperate in transmission, reception, compression, and signal processing. Sensor NetworksEnergy is the driving constraint

  34. Energy-Constrained Nodes • Each node can only send a finite number of bits. • Transmit energy minimized by maximizing bit time • Circuit energy consumption increases with bit time • Introduces a delay versus energy tradeoff for each bit! • Short-range networks must consider transmit, circuit, and processing energy - jointly. • Most sophisticated transmission techniques not necessarily most energy-efficient! • Sleep modes save energy - but complicate networking. • Changes everything about the network design: • Bit allocation must be optimized across all protocols. • Delay vs. throughput vs. node/network lifetime tradeoffs. • Optimization of node cooperation.

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