doc.: ieee 802.15-05-0021-00-004a submission january 2004 welborn, freescaleslide 1 project: ieee...

January 2004

Welborn, FreescaleSlide 1

doc.: IEEE 802.15-05-0021-00-004a

Submission

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)(WPANs)

Submission Title: [TG4a Proposal for Low Rate DS-UWB (DS-UWB-LR)]Date Submitted: [January 2004]Source: [Matt Welborn ] Company [Freescale Semiconductor, Inc]Address [8133 Leesburg Pike, Vienna VA 22182]Voice:[703-269-3000], FAX: [], E-Mail:[matt.welborn @ freescale.com]

Re: [Response to Call for Proposals]

Abstract: [This document describes a proposal for the TG4a baseline draft standard.]

Purpose: [Proposal Presentation for the IEEE802.15.4a standard.]

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(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) 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.

January 2004


doc.: IEEE 802.15-05-0021-00-004a

Submission

UWB for Low Rate Communications

• UWB has great potential for low power communications– Low fading margin can provide same range for lower

transmit power– Large (ultra-wide) bandwidth can provide fine time resolution

provides potential for accurate ranging

• Drawbacks due to regulations– Limited transmit power – how much is enough?

• Operation at long ranges is highly dependent on NLOS path loss characteristics

January 2004


doc.: IEEE 802.15-05-0021-00-004a

Submission

Proposal for TG4a Alternate PHY Layer

January 2004


doc.: IEEE 802.15-05-0021-00-004a

Submission

Overview of DS-UWB-LR TG4a Proposal• Based on higher rate DS-UWB proposal under consideration in TG3a, but

modified for low power and lower complexity– Variable-length code spreading with BPSK modulation of data– Chip rates are 1/3 the rates used in DS-UWB (so about 450 MHz) – Bandwidth is only ~500 MHz (instead of ~1500 M)– Lower complexity FEC convolutional code (constraint length k=4)

• Data rates of 30 kbps to 10 Mbps– Use spreading codes of length 24 to 6144– AWGN range of 15 to 75 meters (assuming n=3.5 PL at > 10m)

• Support for precise ranging– Very straight forward solutions using RTT measurements with corrections for non-

direct-path propagation effects • Flexible pulse shaping

– Allows many pulse generation, antenna and receiver architectures– Supports requirements for coexistence & regulatory constraints

• Will enable interoperation between higher rate DS-UWB devices and low rate, low complexity TG4a devices

– Support wider range of asymmetric applications– Enables active coexistence and coordination

January 2004


doc.: IEEE 802.15-05-0021-00-004a

Submission

Benefits of Low Rate DS-UWB

• Bandwidth & operating frequency– Transmit power, ranging, complexity & performance

• Pulse rate– Effects on efficiency & implementation

• Data Rate• Interoperability & Coexistence

January 2004


doc.: IEEE 802.15-05-0021-00-004a

Submission

Operating Frequency• Multiple operating channels with different center frequencies to provide

FDM operation for different networks– Three piconet bands at 3536, 4056, and 4576 MHz– Different performance due to 20 Log10(Fc) term in path loss

• Also uses CDM for sharing of each band by different piconets • Cost of generating the reference frequency depends on the specific

frequency – DS-UWB is based on low cost, high quality 26 MHz crystals (widely used in

cell phones)• Better frequency accuracy can relax other system constraints

– Acquisition at longer range requires longer integration and therefore more accurate reference frequency

– High accuracy clock can allow longer “sleep” time & better power management

– Precise ranging using TOA methods requires high precision time measurements over relatively long intervals (RTT) to determine small differences in signal propagation times

• Simplified and improved with good reference clock

January 2004


doc.: IEEE 802.15-05-0021-00-004a

Submission

Signal Operating Bands for Low Rate UWB

4576405635363100 5100

High rate DS-UWB Low Band with RRC

Pulse Shape

Possible Lower Rate Signaling Bands (500 MHz bandwidth)

Frequency (MHz)

0-3

-20

RelativePSD (dB)

• Ultra-wideband ~500+ MHz bands for each piconet– Code-division and Frequency-division multiplexing – Multiple piconets in each band using different codes

• Operation in close proximity, interference avoidance or coexistence• Three piconet bands at 3536, 4056, and 4576 MHz

FCC Mask

January 2004


doc.: IEEE 802.15-05-0021-00-004a

Submission

Low Rate DS-UWB Pulse Rate• “Impulse radio” (IR) originally meant low pulse rate (10’s of M

pulse/sec) using “time hopping” for multiple access and pulse position modulation (PPM)

• More generally, IR is just pulse-based spread spectrum with data modulation

– Many choices for modulation (BPSK, PPM, OOK, etc.)– One or more pulses per data symbol

• Low rate DS-UWB uses a chip rate that is designed to meet minimum 500 MHz bandwidth for simple BSK modulation

– Center frequency is always a multiple of 26 MHz– Chip rate is equal to center frequency divided by 9 (e.g. 4052 / 9 =

450.66MHz)– Spreading codes are based on 24-chip code– Longer spreading codes are derived from the basic code by further sreading

with PN sequence (e.g. length 192 code is a length 24 code spread by a length 8 PN code)

• Pulse rate does not fundamentally affect transmit power, signal bandwidth or system performance

• Pulse rate does affect energy per pulse and therefore peak power (and voltage)

January 2004


doc.: IEEE 802.15-05-0021-00-004a

Submission

Higher Pulse Rate = Lower Peak Power

• Lower pulse rate requires higher “energy per pulse” and therefore higher peak power (and voltage) for same transmit power

• Process technology can limit available peak voltage that can be achieved without an external power amplifier ___

• If pulse rate is 100x slower, then peak voltage is 100 = 10x higher

Higher peak power & voltage for same average power

January 2004


doc.: IEEE 802.15-05-0021-00-004a

Submission

Data Rate Considerations• Lowest PHY data rate does not necessarily mean lowest energy

consumption• In fact, a fast radio can potentially be more energy efficient than a

slow radio. Example:– Compare a 1 Mbps radio at 100 mW versus 10 kbps radio at 10 mW– 32 kB @ 10 kbps = 0.256 mW*seconds– 32 kB @ 1 Mbps = 0.0256 mW*seconds – 1/10 of the energy per bit!

• Assumptions– Both radios achieve minimum range requirement for application – Minimum acquisition time is a function of SNR (range) not data rate – Requires fast wake-up and shut down of radio with aggressive power

management• Relative energy usage depends on packet size

– Fast radio advantage is higher for longer packets • Notice transmit power is a small fraction of the total power (<1%)

– The largest power use is turning on the radio and processing signal

January 2004


doc.: IEEE 802.15-05-0021-00-004a

Submission

Data Rate Considerations

Higher peak power but shorter transmission time for same payload

Preamble

Preamble

Lower radio power, but longertransmission time for data payload

• Total energy use from battery is the “area” under the power vs. time curves shown above • Relative efficiency depends on power & duration (payload size)

Power

Power

Time

Time

January 2004


doc.: IEEE 802.15-05-0021-00-004a

Submission

Low Rate DS-UWB Data Rates

• LR-DS-UWB data rates are designed to support relatively high rate operation at relatively small duty cycle

Spreading code Length

Symbol Rate

FEC Rate PHY Bit Rate

192 2.35 MHz 0.5 1.17 Mbps

768 587 kHz 0.5 293 kbps

6144 73 kHz 0.5 37 kbps

24 18.778 MHz 0.5 9.4 Mbps

January 2004


doc.: IEEE 802.15-05-0021-00-004a

Submission

Link Budget

Xo = 1.17 Mbps

X1 = 293 kbps

X1 = 36.7 kbps

X1 = 9390 kbps

FEC Rate 0.5 0.5 0.5 0.5Spreading Code Length 192.0 768.0 6144.0 24.0Data Rate (kbps) 1173.6 293.4 36.7 9388.9Transmit Power (dBm) -16.7 -16.7 -16.7 -16.7Path Loss (dB) at 1m with 1/R^2 (L1) 44.2 44.2 44.2 44.2Path loss from 1 m to 30 m (L2) 29.5 29.5 29.5 29.5Rx Antenna Gain (Gr) 0.0 0.0 0.0 0.0Received Power -90.5 -90.5 -90.5 -90.4Noise Power per Bit -113.3 -119.3 -128.4 -104.3Noise Figure 7.0 7.0 7.0 7.0Total Noise Power -106.3 -112.3 -121.4 -97.3Required Eb/No (@3.8e-5 BER) 5.2 5.2 5.2 5.2Implementation Loss 3.0 3.0 3.0 3.0Link Margin (@ d= 30 m) 7.6 13.6 22.7 -1.4Sensitivity (dBm) -98.1 -104.1 -113.2 -89.11/R^2 to d=30m, then 1/R^3.5 beyondResulting AWGN Range (m) 49.6 73.6 133.4 27.4

January 2004


doc.: IEEE 802.15-05-0021-00-004a

Submission

Link Budget Notes

• Assumptions– Chipping rate = 450.66 MHz

– Includes 1.9 dB Tx power reduction for spectral ripple in certification testing

– Assumes 3.8e-5 BEr to achieve 1% Per with 32 octet data packet

January 2004


doc.: IEEE 802.15-05-0021-00-004a

Submission

Interoperability & Coexistence

• All of the specific co-existing systems in the Slection Requirements are out-of-band to LR-DS-UWB– Robustness against in-band interference is provided by the UWB

bandwidth of the LR-DS-UWB system (large processing gain) • Many types of other UWB systems and waveforms will share

the UWB bands– Interoperability between TG4a & higher rate systems could enable

improved coexistence • Interoperation with higher rate systems could increase the utility

of the TG4a standard– Interoperability of low cost sensor/RFID devices with nearby UWB

CE devices– Interoperability with DS-UWB could be quite simple if correct

parameters are chose for TG4a• Common reference frequency, codes & operating bands

January 2004


doc.: IEEE 802.15-05-0021-00-004a

Submission

Technical Feasibility

• The Low rate DS-UWB solution for TG3a has a high level of manufacturability– Based on existing DS-UWB technology– Can be implemented in low-cost CMOS technology

• Time to Market– Time to market is quite reasonable. Compliant PHY

implementations could be available for integration in 2005.

• Regulatory Impact– DS-UWB technology is know to be compliant with FCC UWB rules– Other regulatory administrations are using FCC rules as a basis for

initial discussions– Many mechanisms exist to ensure compliance for other regions that

adopt other regulations

January 2004


doc.: IEEE 802.15-05-0021-00-004a

Submission

System Performance

• System and SOP simulations are underway – results TBD

doc.: ieee 802.15-05-0021-00-004a submission january 2004 welborn, freescaleslide 1 project: ieee...

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