1. July, 2002
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Propagation notes to P SG3a from IEEE Tutorial]
Date Submitted: [17 July, 2002]
Source: [Kai Siwiak]
Company: [Time Domain Corporation]
Address: [7057 Old Madison Pike, Huntsville, AL 35806]
Voice: [ ]
[ ]
Re: [Response to the Call for Contributions on UWB Channel Models (IEEE P /208r1-SG3a).]
Abstract: [This contribution shows that a fundamental system gain limit in UWB places a constraint on maximum data rate versus bandwidth.]
Purpose: [This contribution shows a fundamental system limit in UWB which is relevant to path loss and defines the fundamental limitations to range at a specific data rate in free space propagation. It is recommended that this fundamental limit be used to represent the performance of UWB systems instead of models representing tough RF environments which might be interpreted to conclude that UWB physical layer submissions for a high-rate extension to IEEE would not work. The models need be concerned with selection criteria rather than with system design efforts. System designers will consider operating environments and other factors in designing and delivering robust implementations.]
Notice: This document has been prepared to assist the IEEE P 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 P
Time Domain Corporation

2. UWB Propagation notes to P802.15 SG3a
July, 2002
UWB Propagation notes to P SG3a
A Fundamental System Gain Limit (Limit) for UWB can be defined in terms of:
regulatory emission limits
frequency band
ideal modulation performance
Implementations then degrade performance from this fundamental limit
This limit provides a sanity check on UWB capabilities and should be used to describe the UWB median path loss for P SG3a activities. This propagation model along with multipath models being developed should then be used as selection criteria in SG3a
Time Domain Corporation

3. UWB FCC Emission Limit for Hand-held Systems
<month year>
doc.: IEEE <doc#>
July, 2002
UWB FCC Emission Limit for Hand-held Systems
0.96
1.61
1.99
3.1
10.6
GPS Band
Source:
Time Domain Corporation
<author>, <company>

4. Fundamental Limit: 173.3 dB/Hz System Gain
<month year>
doc.: IEEE <doc#>
July, 2002
Fundamental Limit: dB/Hz System Gain
-41.3 dBm/MHz
-41.3 dBm / MHz
+10 log(7.5x103) MHz
-2.5 dBm EIRP
7,500 MHz
-2.5 dBm EIRP
-(-1.59) dB SNR
-( ) dBm/Hz
System Gain = dBm/Hz
dBm/Hz
-1.59 dB
-1.59dB
3.1 GHz
10.6 GHz
Bounded by FCC, Shannon, Boltzmann (thermal noise)
Time Domain Corporation
<author>, <company>

5. July, 2002
Limit and Parameters
Limit means 1 b/s has available dB path loss – nearly 2,000 km range between unity gain antennas!
Practical implementations mean additional limits
Desired data rates (much higher than 1 b/s!)
EIRP further limited by FCC PSD masks corners, margin, and antenna implementations
Practical modulations need further margin
Noise figure and losses further limit performance
Time Domain Corporation

6. Example: UWB at a High Data Rate
<month year>
doc.: IEEE <doc#>
July, 2002
Example: UWB at a High Data Rate
Consider: 200 Mb/s system, Antipodal modulation: 10-3 BER, 9 dB noise figure + losses, GHz, 0 dBi antennas
System Gain
10 log(data bandwidth)
SNR required by modulation
System losses, (noise figure, implementation loss, ...)
10 log(“3dB” PSD BW / 7.5 GHz)
Antenna gain or loss
Path attenuation
System Gain Limit dB
-10 log(200x106) = dB
-SNR= (- 1.59) = dB
-System losses = dB
10 log(1.2 / 7.5) = dB
Antenna: = dBi
Left for Path attenuation: 64.9 dB
0.75 MAC and error correction factor brings link capacity to 150 Mb/s
1 m path loss = 44 dB,
leaves 20+ dB for range:
10+ m in free space
Time Domain Corporation
<author>, <company>

7. Link Capacity vs. Range July, 2002 Limited by 2GHz bandwidth
Fundamental limit with log2(1+S/N) in 3.1 to 10.6 GHz
Fundamental limit
106
Example link,
nominal path loss,
0.75 factor for MAC and error correction
105
104
103
Link Capacity, Mb/s
100
Example link, with 17dB additional loss 10 1
0.1
0.01 1 10
100
Nominal path loss from [4] 02/301r3 with d1=12 and g=3
Range, meters
Time Domain Corporation

8. What limits UWB performance?
July, 2002
System Gain Summary
What limits UWB performance?
Noise, bandwidth, emission limits, implementation efficiency
What is the fundamental system gain limit?
173.3 dB/Hz
How about a Practical limit?
173.3 – 8.4 – 9 – 8 »148 dB/Hz
Time Domain Corporation

9. July, 2002
System Performance
200 Mb/s allows conservative error correction coding, ample MAC overhead for 110 Mb/s delivered at 10 m [2]: fits in space and SG3a PAR [3]
Noise figure and losses of 9 dB aggressive but realistic
EIRP bandwidth respects 3.1 GHz 20 dB corner and UNII coexistence: again realistic
Short range free space propagation between unity gain antennas assumed; seems justifiable as “total power” [4] propagation and in some LOS cases
However, robust guaranteed-delivery system designs in the most difficult RF environments need as much as dB more margin [5]!!
Time Domain Corporation

10. July, 2002
Implications to (SG3a)
UWB Range limited by FCC masks and by practical implementations
Propagation committee formed to study a channel model to realistically compare UWB solutions in multipath (and can provide important guidance to system designers)
Practical 110 Mb/s at 10 m possible with realistic assumptions
Additional margin is needed for robustness in the toughest and most demanding environments
Implementers must consider operating environments and required performance in designing UWB solutions
Time Domain Corporation

11. July, 2002
Conclusions
Channel model (path loss + multipath) can serve many purposes
Compare systems in a selection process
Design robust guaranteed-performance systems
Highlight especially challenging RF environments
Robust guaranteed performance implies ~17 dB additional margin in tough RF environments – but lets not fix Guillotines!
This margin is constant across systems
Irrelevant to the SG3a selection criteria
SG3a should follow the free space path loss model recommendation in [5] to 10 m, along with an accurate multipath component to depict system performance for selection process
Time Domain Corporation

12. July, 2002
References
[1] Kai Siwiak and Debra Culver, “UWB Radio Technology in Wireless PANs,” IEEE Vehicular Technology Conference, Birmingham, AL, May 6, 2002
[2] IEEEP (SG3a), “Technical Requirements Document,” 02104r10P802-15_SG3a-Technical-Requirements.doc, 17 June 2002
[3] IEEEP (SG3a), “IEEE P SG3a Alt-PHY Study Group PAR and 5 Criteria,” 02103r6P802-15_SG3a-PAR-5Criteria.doc, 24 June 2002
[4] K. Siwiak, “UWB Propagation Phenomena,” 02301r3P802-15_SG3a-UWB-Propagation-Phenomena.ppt, IEEEP (SG3a) document, July 2002
[5] Jeff Foerster, “SG3a Update of UWB Channel Modeling Sub-committee,” 02327r0P802-15_SG3a-Channel_model_update.ppt , IEEEP (SG3a) document, 11 July 2002
Time Domain Corporation