1. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANS)
Submission Title: [General Atomics – Interference Analysis of IEEE a on UWB Systems]
Date Submitted: [November 2002]
Revised: []
Source: [Naiel Askar, Ph.D.; Roberto Aiello, Ph.D.] Company [General Atomics Inc.] Address [General Atomics Photonics Division- Advanced Wireless Group, Flanders Ct, San Diego, CA ] Voice [(858) ], Fax [(858) ], [Roberto Aiello]
Re: [Interference Analysis]
Abstract: [Tutorial]
Purpose: [IEEE SGa Tutorial November 12, 2002]
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 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 P
<author>, <company>

2. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
November 2002
Interference Analysis
of IEEE a on UWB Systems
General Atomics-Naiel Askar & Roberto Aiello
<author>, <company>

3. We will see today… Interference definitions and policies
November 2002
We will see today…
Interference definitions and policies
Potential interference issue between IEEE a and UWB due to overlap in frequency
New policies on interference and co-existence are being developed by regulatory agencies (FCC) and the IEEE-SA
Interference analysis is based on principles drawn from the current selection criteria
Two UWB examples considered: high PRF, single band system and low PRF, multi-band system
Conclusions and recommendations
Both UWB system examples are affected by a emission
Spectrum regulators will demand that new standards and incumbents “equally bear the responsibility” via two-way dialog to “promote coexistence”
Technical collaboration between15.3a and a groups need to be established while the15.3a standard is being developed
General Atomics-Naiel Askar & Roberto Aiello

4. Potential interference- UWB & 802.11a overlap frequencies
November 2002
Potential interference- UWB & a overlap frequencies
*Source: FCC 02-48, UWB Report & Order
*Source: IEEE P802.11a Standard
General Atomics-Naiel Askar & Roberto Aiello

5. November 2002
[IEEE objective is to] maximize the use of the spectrum and promote co-existence1
Both FCC and IEEE-SA’s missions include public good, global needs and interoperability and co-existence
The FCC requires that devices “…may not cause…” and “…must accept harmful interference” [47 C.F.R. Sec. 15.5(b)]
“The [Federal Communication] Commission may, consistent with the public interest…make reasonable regulations … governing the interference potential of devices which in their operation are capable of emitting radio frequency energy…[US Comm. Act of 1934, Sec ]
“The IEEE-SA provides a standard program that serves the global needs of industry, government and the public. [IEEE-SA Website]
“It is in the best interest of users and the industry to strive for a level of coexistence with other wireless systems, especially those in similar market spaces”. [ a PAR]
1 P.Nikolich, C. Stevenson, “Comments of IEEE 802 in response to the commission’s spectrum policy task force inquiry”, July 13, 2002
General Atomics-Naiel Askar & Roberto Aiello

6. November 2002
The challenge is to find equitable new rules that improve overall efficiency
FCC and IEEE-SA are currently reviewing policies on interference, sharing and co-existence to update all assumptions for new technologies
FCC currently reviewing spectrum’s policy to improve spectrum’s scarcity due to current spectrum management policies: “Chairman Powell has formed a Spectrum Policy Task Force charged with conducting a systemic evaluation of existing spectrum policies and with making recommendations as to possible improvements” [FCC Docket ]
IEEE Coexistence TAG: “… will develop and maintain policies defining the responsibilities of 802 standards developers to address issues of coexistence with existing standards and other standards under development”. “The informal definition shall be “the ability of one system to perform a task in a given shared environment in which other systems have an ability to perform their tasks and may or may not be using the same set of rules” [IEEE COEX 02/023r0]
General Atomics-Naiel Askar & Roberto Aiello

7. November 2002
802.11a and UWB interference needs to be reciprocally evaluated to define scenario of maximum efficiency
Both FCC’s and IEEE’s goal is to increase global efficiency
Maximize network capacity
Maximize spectral efficiency
Maximize economic efficiency
“New users and incumbent users should equally bear the responsibility for adopting technologies designed to maximize the use of the spectrum and promote coexistence” [Nikolich, 2002]
“Rather than simply saying your transmitter cannot exceed a certain power, we instead would utilize receiver standards and new technologies to ensure that communication occurs without interference, and that the spectrum resource is fully utilized.” [Powell, Oct 30, 2002]
Therefore the complex question of a and UWB interference should be addressed by both sides
General Atomics-Naiel Askar & Roberto Aiello

8. Interference metric: Signal to Interference Ratio Margin (MSIR)
November 2002
Interference metric: Signal to Interference Ratio Margin (MSIR)
MSIR is the excess signal power at the receiver over what is required for a given performance
MSIR (dB) = UWB Tx Power a Tx Power (UWB path loss - 11a path loss) Required SIR
General Atomics-Naiel Askar & Roberto Aiello

9. STEP1 : UWB peak Tx power, system dependent (1 of 3)
November 2002
STEP1 : UWB peak Tx power, system dependent (1 of 3)
Peak Tx power (dBm) = FCC Limit + 10*log(BW^2/PRF)1
2 example architectures will be considered
Example1
Example2
Duty Cycle, PRF
High
Low
Frequency Bands
One
Multiple
Processing Gain
(per band)
Multiple pulses per bit
One or more bits per pulse
PRF (per band)
Raw bit rate*pulses per bit
Raw bit rate/bits per pulse / no. of bands
1 See backup slide for more details
General Atomics-Naiel Askar & Roberto Aiello

10. STEP1 : UWB examples shown in frequency and time (2 of 3)
November 2002
STEP1 : UWB examples shown in frequency and time (2 of 3)
General Atomics-Naiel Askar & Roberto Aiello

11. STEP 1: UWB TX power- Assumptions (3 of 3)
November 2002
STEP 1: UWB TX power- Assumptions (3 of 3)
Example1
Example2
Raw Bit Rate (Mbps)
150
BW (GHz) (per band) 3
0.5
No of bands 1 6
Pulses per bit (per band) 15
PRF(per band) (MHz)
2250 25
Tx Peak Power (dBm) -5
-1 (per band)
General Atomics-Naiel Askar & Roberto Aiello

12. Utilize the 5.25-5.35 GHz band parameters
November 2002
STEP 2: a Tx power
Utilize the GHz band parameters
Total Tx power is 23 dBm
Out of band emissions – 41 dBm/ MHz
For and GHz bands, apply correction factors to MSIR of +7 and -6 dB respectively
General Atomics-Naiel Askar & Roberto Aiello

13. STEP 3: Difference in path loss
November 2002
STEP 3: Difference in path loss
Depends on relative distance
Some applications need < 1 ft. separation
Performance will depend on relative distance
Adapted Selection Criteria numbers to reflect our example
Selection Criteria
Example Value
Correction Factor
11a Tx Power
+15 dBm
+23 dBm
-8 dB
UWB Rx Level
-6 dB
UWB/11a distance ratio
10:1 (required) 33:1(desired)
1:1
20 dB (required)
Path Loss Difference (dB) +6
Path loss difference equivalent to dSIG :dINT of 2:1
Assume line of sight propagation loss
Path loss of both systems will be frequency independent
The UWB antenna gain will compensate for differences in path loss
General Atomics-Naiel Askar & Roberto Aiello

14. STEP 4: Required SIR at the receiver
November 2002
STEP 4: Required SIR at the receiver
SIR value is system / application dependent
Acceptable throughput/BER
UWB modulation
Receiver implementation
Received signal level
For Example 1 assume
SIR (dB) = 6 - Processing gain
For Example 2 assume
For the band with interference SIR (dB) = 6 dB
For other bands SIR (dB) = 6 dB - 30dB (depends on filtering rejection)
General Atomics-Naiel Askar & Roberto Aiello

15. Calculated SIR Margin: From the two examples
November 2002
Calculated SIR Margin: From the two examples
Example 1
Example 2
Interferer
In-band
Out-of-band
MSIR
-23.5
-38 -8
Conclusions
A challenge for engineering ingenuity
The Example 1 single-band system is more resistant to interference than Example 2 multi-band system when interference is in band
The Example 2 system is more resistant when interference is out-of-band
General Atomics-Naiel Askar & Roberto Aiello

16. Possible remedy: Avoid 802.11a
November 2002
Possible remedy: Avoid a
Single-band System
Multi-band System
Limit spectrum below a ( GHz)
May not achieve enough processing gain
Select from above and below
Limit spectrum above a ( GHz)
May be difficult in current technology
Adaptive band selection
Reduce bandwidth when interference is present
Select bands based on interference
General Atomics-Naiel Askar & Roberto Aiello

17. Another remedy: RF notch filters
November 2002
Another remedy: RF notch filters
General Atomics-Naiel Askar & Roberto Aiello

18. Interference canceling in the digital domain
November 2002
Interference canceling in the digital domain
Approaches such as Minimum Mean Square Error (MMSE) have been successfully utilized in CDMA for interference cancellation up to 30 dB
Needs bits extra in ADC dynamic range
Digital processing at high frequencies > 1 GHz
Cost and power consumption will be an issue
General Atomics-Naiel Askar & Roberto Aiello

19. Conclusions and recommendation
November 2002
Conclusions and recommendation
PHY performance analysis performed according to principle on current selection criteria
802.11a interference with UWB will not be trivial to resolve
Mitigation of interference from a devices should be designed in from day 1
We have considered interference avoidance, RF notch filters, digital approaches
Effects of UWB on a remain to be investigated
Spectrum regulators will demand that new standards and incumbents “equally bear the responsibility” via two-way dialog to “promote coexistence”
Technical collaboration between a and a groups need to be established while the a standard is being developed
Opportunities
Promote transmitter power control on all a devices
Joint IEEE a & work effort to address UWB interference and co-existence for long term
General Atomics-Naiel Askar & Roberto Aiello

20. Additional Material for Backup
November 2002
Additional Material for Backup
General Atomics-Naiel Askar & Roberto Aiello

21. Spreadsheet Calculations
November 2002
Spreadsheet Calculations
General Atomics-Naiel Askar & Roberto Aiello

22. Tx peak power calculation
November 2002
Tx peak power calculation
Tx peak power = FCC limit * BW / Duty Cycle
Duty Cycle = PRF * Pulse width
BW ~= 1/Pulse width
Tx Peak power = FCC Limit *BW^2/ PRF
General Atomics-Naiel Askar & Roberto Aiello