UWB at the Other End of the Spectrum: Low Bit Rate, Low Power Systems

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANS) Submission Title: [Discrete Time Communications – UWB at the other end of the spectrum: low bit rate, low power systems] Date Submitted: [November 2002] Revised: [12 November 2002] Source: [Roberto Aiello, Larry Taylor] Company [Discrete Time Communications] E-mail [Roberto@DiscreteTime.com], [Larry@DiscreteTime.com] Re: [UWB for low bit rate, low power systems] Abstract: [This presentation is an introduction to UWB for low bit rates, low cost systems with very long battery life.] Purpose: [Tutorial contribution] Notice:This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual or organization. The material in this document is subject to change in form and content after further study. The contributor reserves the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15.

2. UWB at the other end of the spectrum:low bit rate, low power systems Roberto Aiello (Roberto@DiscreteTime.com) Larry Taylor (Larry@DiscreteTime.com) Discrete Time Communications Discrete Time Communications, Aiello -Taylor

3. Summary • New definition of UWB • Consequences of new definition on UWB system design • UWB features for low power systems • Link budget example • Interoperability and co-existence • Power consumption and cost considerations Discrete Time Communications, Aiello -Taylor

4. UWB’s Indoor’s Spectral Mask Discrete Time Communications, Aiello -Taylor

5. UWB definitions* • 7,500MHz available spectrum for unlicensed use • US operating frequency: 3,100 – 10,600 MHz • Emission limit: -41.3dBm/MHz EIRP • Indoor and handheld systems • Other restrictions and measurement procedures in Report & Order • UWB device defined as • Fractional bandwidth greater than 20% • Occupies more than 500 MHz • UWB device NOT defined as • Modulation or pulsed modulation • Carrierless • Impulse radio *Source: FCC 02-48, UWB Report & Order, released 22 April 02 Discrete Time Communications, Aiello -Taylor

6. Examples of UWB signal, according to FCC ruling • Anything shorter than this will be wider than that • Lots of time and frequency available for exploitation Discrete Time Communications, Aiello -Taylor

7. IEEE 802.15.4 operating frequencies 868MHz/ 915MHz PHY Channels 1-10 Channel 0 2 MHz 868.3 MHz 902 MHz 928 MHz 2.4 GHz PHY Channels 11-26 5 MHz 2.4 GHz 2.4835 GHz Discrete Time Communications, Aiello -Taylor

8. IEEE 802.15.4 modulation/spreading 2.4 GHz PHY • 250 kbps (4 bits/symbol, 62.5 kBaud) • Data modulation is 16-ary orthogonal modulation • 16 symbols are ~orthogonal set of 32-chip PN codes • Chip modulation is MSK at 2.0 Mchips/s 868MHz/915MHz PHY • 20 kbps (1 bit/symbol, 20 kBaud) • Data modulation is BPSK with differential encoding • Spreading code is a 15-chip m-sequence • Chip modulation is BPSK at 0.3 Mchips/s Discrete Time Communications, Aiello -Taylor

9. Example link budget Discrete Time Communications, Aiello -Taylor

10. Link budget comments • 1MHz signaling rate • Modulation order can be kept low • Room for processing gain at 1Mchips/s • 0.2% signaling duty cycle • 30mW average transmit power • +12dBm transmit signal peak power • Low probability of collision with other systems • Large enough range for required applications Discrete Time Communications, Aiello -Taylor

11. Channelization opportunities • Previous example’s parameters • 0.2% signaling duty cycle • bit rate over the air: 1Mbps for 1 bit/symbol encoding • 195ft range in free space • Consequences • Low probability of collision • Margin for processing gain • Channelization can leverage a combination of time, frequency and code channels • A lot of bandwidth available • Low duty cycle • Higher bit rate leaves room for processing gain Discrete Time Communications, Aiello -Taylor

12. UWB satisfies TG4 low power and cost requirements • Very low signaling duty cycle • nanoseconds long signal at microseconds rate • very low transmit signal’s average power • Transmit signal’s average power < 40mW in the link budget example • Advanced power management strategy can be supported • Fast wakeup also supports minimum power consumption • Antennas • printed antennas available • “smaller” UWB bandwidth relaxes some antenna’s requirements • No need for high-Q components allows CMOS implementation Discrete Time Communications, Aiello -Taylor

13. Location information opportunities • Location awareness, even without mobility, is useful to • Reduce expenses in installations, maintenance, etc. • Reduce overall system complexity • Angle or phase measurements difficult in multipath environment • Time of flight measurements, typical of UWB, may provide value in multipath environment Discrete Time Communications, Aiello -Taylor

14. Other considerations • Very low power spectral density allows TG4 devices to co-exist with all other wireless services • Selectively avoid troublesome co-located signal (see 02441r1P802-15-SG3a) • Inherent immunity to multipath fading reduces radio cost and complexity • Ranging information for location determination can be provided Discrete Time Communications, Aiello -Taylor

15. Conclusions • UWB PHYs can extend TG4’s capabilities and exceed its power and cost objectives • Definition of UWB has changed allowing features for low power systems • Other considerations that make UWB appealing include • multipath immunity • location capabilities • UWB may address TG4’s evolutionary requirements now emerging Discrete Time Communications, Aiello -Taylor