Doc.: IEEE 802.15-05-0013-01-004a Submission January 2005 Vern Brethour, Adrian Jennings (Time Domain) Slide 1 Project: IEEE P802.15 Working Group for

January 2005

Vern Brethour, Adrian Jennings (Time Domain)Slide 1

doc.: IEEE 802.15-05-0013-01-004a

Submission

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

Submission Title: [Time-Domain-CFP-Response]

Date Submitted: [4 January, 2005]

Source: [Vern Brethour, Adrian Jennings] Company: [Time Domain Corp.]Address: [7057 Old Madison Pike; Suite 250; Huntsville, Alabama 35806]Voice: [Vern: (256) 428-6331; Adrian: (256) 428-6326], E-Mail: [[email protected]; [email protected]]

Re: [802.15.4a CFP]

Abstract: [802.15.4a CFP response from Time Domain. An impulse radio nominally occupying 3 – 5 GHz with 4 ns chip times using 40 chips/symbol and 300 ns quiet time between symbols.]

Purpose: [Response to WPAN-802.15.4a CFP]

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 individuals or organization. The material in this document is subject to change in form and content after further study. The contributors reserve the right to add, amend or withdraw material contained herein.

Release: The contributors acknowledge and accept that this contribution becomes the property of IEEE and may be made publicly available by P802.15.

January 2005


doc.: IEEE 802.15-05-0013-01-004a

Submission

Time Domain Proposal:

Single Band UWB Alternate Physical Layer

for TG 802.15.4a

January 2005


doc.: IEEE 802.15-05-0013-01-004a

Submission

Proposal Contents

• General Overview

• Proposal Principles

• Regulatory Flexibility

• Performance

• Evaluation Matrix (in backup slides)

January 2005


doc.: IEEE 802.15-05-0013-01-004a

Submission

General Overview

• Impulse radio

• Single band nominally from 3 to 5 Ghz.

• 4 ns chip times

• 40 chips per symbol

• 300 ns quiet time between symbols

• Max symbol integration = 64 (data)

• Max symbol integration = 256 (acquisition)

January 2005


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Submission

Proposal Principles

• The most important part of a proposal is the signal as it appears on the air. For most signal definitions, there are many ways to build a radio, and as many corresponding performance results. However, as a standard, we can define a signal which will forever limit the systems ultimate performance. (For example, by not using all reasonably available bandwidth.)

January 2005


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Submission

The need for robust links

• There is already a 15.4a radio at 2.54GHz. We must be substantially better than that radio.

• This proposal provides the opportunity for maximum performance by occupying as much bandwidth as reasonable.

January 2005


doc.: IEEE 802.15-05-0013-01-004a

Submission

Regulatory Flexibility

• There are fundamentally two approaches to UWB regulatory flexibility: – 1) using multiple bands.– 2) longer chip times.

• Using long chip times allows for filters if needed and does little harm if not needed.

January 2005


doc.: IEEE 802.15-05-0013-01-004a

Submission

Regulatory Flexibility

• This proposal occupies all of the spectrum between the ISM bands and the UNII bands

• This proposal allows ample (4 ns) chip time to accommodate spectral shaping if necessary.

• This proposal also allows a future (optional) band between 6 and 10 GHz.

January 2005


doc.: IEEE 802.15-05-0013-01-004a

Submission

Support for positioning

• There are already radios which do the low data rate communications job without positioning.

• Excellent positioning performance will be the key differentiator for 15.4a.

• Use of as much bandwidth as reasonable gives the best positioning performance.

January 2005


doc.: IEEE 802.15-05-0013-01-004a

Submission

What about the “simple radio” approach?

• Vocabulary is important here. Words like “simplicity” imply virtue. Words like “crude” and “unsophisticated” might be used by others to describe the same radio.

• The critical issue is that there will be other users of the spectrum and the 4a standard must use spectrum and air time efficiently and effectively.

• A proposed standard which we think implies a “simple and virtuous” radio might be viewed by others as spectrally wasteful and unworthy of letter ballot approval.

January 2005


doc.: IEEE 802.15-05-0013-01-004a

Submission

What does “simple radio” mean?

• A “simple radio” to our customers doing system integration, is a radio with the lowest chip count, the least number of passives and the most forgiving antenna driver.

• The integration customer does not (and should not) care how hard we have to work to implement the design inside of our chip.

January 2005


doc.: IEEE 802.15-05-0013-01-004a

Submission

Performance: the optimistic story.

• A “marketing style” link budget looks very optimistic. Even for 250 KByte/sec links, at 100 meters the link budget shows over 6dB of margin.

Parameter Value Value

Information Data Rate 1 Kbps 250 Kbps

Average TX Power -12 dBm -12 dBm

Total Path Loss 84.5 dB

(@ 100 meters)

84.5 dB

(@ 100 meters)

Average RX Power -96.5 dBm -96.5 dBm

Noise Power Per Bit -144 dBm -120 dBm

CMOS RX Noise Figure 8 dB 8 dB

Total Noise Power -136 dBm -112 dBm

Required Eb/N0 2.25 dB 2.25 dB

Implementation Loss 6 dB 6 dB

Link Margin 31.25dB 7.25 dB

RX Sensitivity Level -128 dBm -104. dBm

Max. Range (AWGN) 3652 m 230 m

January 2005


doc.: IEEE 802.15-05-0013-01-004a

Submission

Link Performance: A realistic story.

• Performance predicted by the link budget is optimistic primarily due to the use of “2” for the path loss exponent.

• Links inside buildings with interior walls, will suffer path loss exponents more like “3”.

January 2005


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Submission

Link Performance

• A more realistic idea of performance is available by scaling the results of the simulations done for 802.15.3a to longer ranges and lower data rates.

• The 802.15.3a DS proposal uses signaling similar to this proposal, so I will scale from simulations reported in 802.15.04.0483r5 (McLaughlin, November 2004).

January 2005


doc.: IEEE 802.15-05-0013-01-004a

Submission

Scaling the DS results:

• The 3a DS radio is simulating an 11.8 meter link in CM4 at 110 Mbit/sec with a 90% packet success rate.

• Going from a link distance of 11.8 meters to 100 meters would seem to require less than 20 dB of additional processing gain. BUT that’s with a path loss exponent of 2.

• A path loss exponent of 3 requires 28 dB of processing gain.

January 2005


doc.: IEEE 802.15-05-0013-01-004a

Submission

How much integration is needed for 28 dB of processing gain?

• Each time we double the integration, we get another 3dB of processing gain.

• For 28 dB, we need to do 10 doublings, or an integration rate of 1024.

• Integration rate 1024 will take the 110 Mbit/sec rate down to 107 Kbit/sec.

January 2005


doc.: IEEE 802.15-05-0013-01-004a

Submission

Noticeable difference:

Data rate Predicted range

Link Budget with Path Loss

exponent 2250 Kbit/sec 245 meters

Scaled Simulation with

Path Loss exponent 3

107 Kbit/sec 118 meters

January 2005


doc.: IEEE 802.15-05-0013-01-004a

Submission

Even the Scaled Simulation is a very optimistic result:

• The DS radio that this prediction rests on is a very fancy radio:– 16 Rake taps– 31 tap decision feedback equalizer– Constraint length 6 convolutional code with

Viturbi decoder– RF front end with 6.6 dB noise figure

January 2005


doc.: IEEE 802.15-05-0013-01-004a

Submission

Link budgets do not address acquisition.

• Acquisition will usually be the performance limiter at long range.

• The Acquisition decision needs an additional 6 dB of processing gain over data demodulation.

January 2005


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Submission

We must acquire without benefit of a trained equalizer.

• Equalizers are fine, but only after they have been trained.

• If the spacing between symbols is too short, the resulting inter symbol interference makes trouble for acquisition.

• This proposal uses a relatively long (300 ns) distance between symbols to handle large channel delay spreads without an equalizer.

January 2005


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Submission

Applications need robust links.

• The applications can stand low data rates, so this proposal uses data symbol integration of 64 and acquisition symbol integration 256.

• The long acquisition integration puts a burden on crystal tolerance (2 ppm) that not all vendors will want to deal with, so shorter integration modes will also be supported.

January 2005


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Submission

Clear Channel Assessment

• This is a hard problem for all UWB approaches.

• We should not ignore it. • Detection of energy at the chipping rate (as in

the 15.3a DS proposal) is doable, but not reliable.

• We may need relief from the MAC.

January 2005


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Submission

Simultaneously Operating Piconets

• The long symbol (40 chips) enables good orthagonality between piocnets.

• Different piconets use slightly different chipping rates like the 15.3a DS proposal.

• Bits are modulated onto symbols using only BPSK so all of the symbol orthogonality is used for piconet isolation.

January 2005


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Submission

Power control is the key to compatibility with 15.3a

• This proposal is set up for 100 meter links.

• Many applications will have shorter links.

• For shorter links, we turn down the Tx power.

• Power control gives superior compatibility with all services.

January 2005


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Submission

Proposal Summary

• Impulse radio

• Single band nominally from 3 to 5 Ghz.

• 4 ns chip times

• 40 chips per symbol

• 300 ns quiet time between symbols

• Max symbol integration = 64 (data)

• Max symbol integration = 256 (acquisition)

January 2005


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Submission

Backup Slides

January 2005


doc.: IEEE 802.15-05-0013-01-004a

Submission

Evaluation Matrix

January 2005


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Submission

Self Evaluation – General Solution Criteria

CRITERIA Evaluation

Unit Manufacturing Cost (UMC) +(no need for an equalizer)

Signal Robustness Interference +(due to power control)

Signal Robustness Susceptibility +(due to using max bandwidth)

Coexistence +(due to power control)

Technical Feasibility Manufacturability +(due to low peak Tx amplitudes)

Time To Market +

Regulatory Impact + (due to long chip times)

Scalability +

Location Awareness +(due to using max bandwidth)

January 2005


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Submission

Self Evaluation – PHY Protocol Criteria

CRITERIA Evaluation

Size and Form Factor +

Payload Bit Rate +

Packet Overhead +

PHY-SAP Throughput +

Simultaneously Operation Piconets +(due to the long 40 chip symbol)

Signal Acquisition +(due to long symbol integration)

System Performance +

Link Budget +(due to using max bandwidth)

Sensitivity +

Power Management Modes +

Power Consumption +

Antenna Practicality +

January 2005


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Submission

Example of a chip waveform

January 2005


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Submission

…………………………

1 2 3 39 40

160 ns

…………………………...

Quiet time

4 5 6 7 8 38

Non-inverted pulses are blue,Nulled pulses are orange,Inverted pulses are green.

Multiple chips make a symbol:

January 2005


doc.: IEEE 802.15-05-0013-01-004a

Submission

Allow plenty quiet time between symbols

160 ns

…………………………………………….

300 ns

Documents

Doc.: IEEE 802.15-05-0013-01-004a Submission January 2005 Vern Brethour, Adrian Jennings (Time Domain) Slide 1 Project: IEEE P802.15 Working Group for