doc.: IEEE 802.15-<doc#> <month year> doc.: IEEE 802.15-<doc#> 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. <author>, <company>

doc.: IEEE 802.15-<doc#> <month year> doc.: IEEE 802.15-<doc#> November 2002 Interference Analysis of IEEE 802.11a on UWB Systems General Atomics-Naiel Askar & Roberto Aiello <author>, <company>

We will see today… Interference definitions and policies November 2002 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

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

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. 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

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 02-135] IEEE 802.19 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

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 802.11a and UWB interference should be addressed by both sides General Atomics-Naiel Askar & Roberto Aiello

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 - 11a Tx Power - (UWB path loss - 11a path loss) - Required SIR General Atomics-Naiel Askar & Roberto Aiello

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

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

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

Utilize the 5.25-5.35 GHz band parameters November 2002 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

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

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

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

Possible remedy: Avoid 802.11a November 2002 Possible remedy: Avoid 802.11a Single-band System Multi-band System Limit spectrum below 802.11a (3.1 - 5 GHz) May not achieve enough processing gain Select from above and below Limit spectrum above 802.11a (6 -10.7 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

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

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 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

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 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

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

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

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