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

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANS) Submission Title: [General Atomics – Interference Analysis of IEEE 802.11a 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, 10240 Flanders Ct, San Diego, CA 92121-2901] Voice [(858) 457-8700], Fax [(858) 457-8746], E-mail [naiel.askar@ga.com], [Roberto Aiello] E-mail [Aiello@IEEE.org] Re: [Interference Analysis] Abstract: [Tutorial] Purpose: [IEEE 802.15.3SGa Tutorial November 12, 2002] 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 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 P802.15.

2. Interference Analysis of IEEE 802.11a on UWB Systems General Atomics-Naiel Askar & Roberto Aiello

3. We will see today… • Interference definitions and policies • Potential interference issue between IEEE 802.11a 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 802.11a 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 802.11a 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 *Source: IEEE P802.11a Standard *Source: FCC 02-48, UWB Report & Order General Atomics-Naiel Askar & Roberto Aiello

5. [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. 5.302] • “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”. [802.15.3a 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. 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 02-135] • IEEE 802.19 Coexistence TAG: “… will develop and maintain policies defining the responsibilities of 802 standards developers to address issues of coexistencewith 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. 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 802.11a and UWB interference should be addressed by both sides General Atomics-Naiel Askar & Roberto Aiello

8. 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 - 11a 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) • Peak Tx power (dBm) = FCC Limit + 10*log(BW^2/PRF)1 • 2 example architectures will be considered 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) General Atomics-Naiel Askar & Roberto Aiello

11. STEP 1: UWB TX power- Assumptions (3 of 3) General Atomics-Naiel Askar & Roberto Aiello

12. STEP 2: 802.11a Tx power • Utilize the 5.25-5.35 GHz band parameters • Total Tx power is 23 dBm • Out of band emissions – 41 dBm/ MHz • For 5.15 - 5.25 and 5.725 - 5.825 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 • Depends on relative distance • Some applications need < 1 ft. separation • Performance will depend on relative distance • Adapted Selection Criteria numbers to reflect our example • 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 • 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 • 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 General Atomics-Naiel Askar & Roberto Aiello

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

18. 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 4 - 7 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 • 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 802.11a devices should be designed in from day 1 • We have considered interference avoidance, RF notch filters, digital approaches • Effects of UWB on 802.11a 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 802.15.3a and 802.11a groups need to be established while the 802.15.3a standard is being developed • Opportunities • Promote transmitter power control on all 802.11a devices • Joint IEEE 802.15.3a & 802.19 work effort to address UWB interference and co-existence for long term General Atomics-Naiel Askar & Roberto Aiello

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

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

22. 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