Transcript Slide 1
Ultra WideBand Paul Solecki History of UWB 1962 – Study in time-domain electromagnetics (Ross) 1968 - Short Pulse Radar and Communications Systems conceived 1973 – First UWB patent issued 1978 – Developed SPR and CS 1984 – LPI/D developed 1989 – DoD refers to it as UWB 1994 to present – Most work done without classified government restriction Ultra WideBand Also referred to as impulse, baseband or zero-carrier technology Pulses instead of continuous waves Pulse length on order of sub-nanoseconds in time domain Result is that it uses a wide swath of bandwidth in frequency domain B 2 f h fl Fractional Bandwidth: B f > 20% , but not less than 500 MHz Fc f h fl Pulse vs. Continuous Wave Benefits 100-500+ Mbps rate Ideal for short range WPANs , < 10m Virtually NO Multi-path interference Very low power emission • UWB radio – 75nW/GHz , .26mW aggregate • 802.11b radio - 30 – 100mW • Bluetooth radio – 1mW-1W Shannons equation becomes linear with respect to Bandwidth and Power Simplified architecture, nearly all digital Small silicon space usage UWB – Disadvantages Bad for > 10 Gbps • Due to FCC limit of power emission UWB - Applications Wireless Networks – WPANs Wireless home systems • Computer • Entertainment center Covert communication Radar • fine resolution • Automotive • Ground penetrating Streaming A/V for • PDAs • Digital camera • MP3 players Electronic measuring devices Electronic positioning devices • See through walls etc. UWB Standard IEEE 802.15.3a Task Force FCC set aside 7500MHz of spectrum for unlicensed use 3.1 GHz - 10.6 GHz 100/200/400 Mbps at 10/4/2m OFDM vs. DS-CDMA TI/Intel vs. Motorola/XtremeSpectrum 4.8 GHz is perceived to be the upper band due to current CMOS technology UWB FCC spectral mask • UWB signals must not exceed threshold of spectral mask UWB vs. WiFi 802.15.3a Debate Sept. 2003 – IEEE conference results in 60% approval for OFDM OFDM vs. DS-CDMA TI/Intel vs. Motorola/XtremeSpectrum 75% needed for acceptance Compatibility issues UWB-OFDM Multiple Bands in 3.1 GHz – 4.8 GHz 500 MHz slices Interleave signals UWB-OFDM Advantages Cost Power consumption Complexity of device Proven in 802.11a UWB – OFDM Disadvantages Interference Time synchronization needed UWB – DS-CDMA Direct Sequence Spread Spectrum In a direct sequence system, the transmitted baseband signal is multiplied by a pseudonoise code digital stream. UWB - DS-CDMA UWB – DS-CDMA Advantages Very low interference along ENTIRE spectrum Avoids potential cross-border interference UWB – DS-CDMA Disadvantages Complexity of device Power use Cost UWB vs. Competing Technologies UWB – Bi-phase Radio system All Digital !! No Power Amplifier needed