doc.: ieee 802.15-05-0021-00-004a submission january 2004 welborn, freescaleslide 1 project: ieee...
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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
Welborn, FreescaleSlide 2
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
Welborn, FreescaleSlide 3
doc.: IEEE 802.15-05-0021-00-004a
Submission
Proposal for TG4a Alternate PHY Layer
January 2004
Welborn, FreescaleSlide 4
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
Welborn, FreescaleSlide 5
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
Welborn, FreescaleSlide 6
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
Welborn, FreescaleSlide 7
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
Welborn, FreescaleSlide 8
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
Welborn, FreescaleSlide 9
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
Welborn, FreescaleSlide 10
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
Welborn, FreescaleSlide 11
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
Welborn, FreescaleSlide 12
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
Welborn, FreescaleSlide 13
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
Welborn, FreescaleSlide 14
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
Welborn, FreescaleSlide 15
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
Welborn, FreescaleSlide 16
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
Welborn, FreescaleSlide 17
doc.: IEEE 802.15-05-0021-00-004a
Submission
System Performance
• System and SOP simulations are underway – results TBD
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