1. May 2003
doc.: IEEE /141r3
January 2004
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Coexistence of Multi-band OFDM and IEEE a: Interference Measurements]
Date Submitted: [12 January, 2004]
Source: [Dave Magee, Mike DiRenzo, Jaiganesh Balakrishnan, Anuj Batra] Company [Texas Instruments]
Address [12500 TI Blvd, MS 8649, Dallas, TX 75243]
Voice:[ ], FAX: [ ],
Re: []
Abstract: [This document describes the interference measurement study to investigate the coexistence of the multi-band OFDM system with IEEE a devices.]
Purpose: [For discussion by IEEE TG3a.]
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
Dave Magee et al., Texas Instruments
Jai Balakrishnan et al., Texas Instruments

2. January 2004
Coexistence of Multi-band OFDM and IEEE a: Interference Measurements
Dave Magee, Mike DiRenzo, Jaiganesh Balakrishnan and Anuj Batra
Texas Instruments TI Blvd, MS 8649 Dallas, TX
January 13, 2004
Dave Magee et al., Texas Instruments

3. January 2004
Motivation
Goal: To characterize the impact of Multi-band OFDM UWB interference on a broadband wireless system like IEEE a.
Note that mandatory mode of the Multi-band OFDM proposal does not occupy the U-NII band.
This study was initiated based on comments by members during the ABQ meeting.
Consider an example Multi-band OFDM UWB system that uses the U-NII band.
Dave Magee et al., Texas Instruments

4. Multi-band OFDM Interferer
January 2004
UWB Interferers
We consider two types of UWB interferers for this study.
(1) a MB OFDM interferer operating on 3 bands and with a zero prefix.
(2) an AWGN interferer.
Data was captured at the input of the adjustable gain stage.
During the measurements, both interferers were calibrated to have the same average power.
Multi-band OFDM Interferer
AWGN Interferer
Dave Magee et al., Texas Instruments

5. January 2004
Test Setup
Dave Magee et al., Texas Instruments

6. January 2004
Test Equipment
Dave Magee et al., Texas Instruments

7. Testing Procedure Test procedure:
January 2004
Testing Procedure
Test procedure:
Configure the IEEE a device with a data rate of 36 Mbps (16 QAM, R = ¾).
Calibrate the IEEE a to sensitivity (BER = 10-5) in the absence of interference.
The IEEE a power level was adjusted to different values above sensitivity.
At these power levels, we measured the maximum tolerable interference power level that can be tolerated by the IEEE a devices in order to maintain a BER of 10-5.
Definition: Maximum Tolerable Interference Power Level (MTIPL) is defined as the interference power level that can be tolerated by the IEEE a device and still maintain a BER of 10-5.
Dave Magee et al., Texas Instruments

8. Signal Power of 802.11a above sensitivity
January 2004
Measurement Data
The difference in MTIPL between the MB-OFDM and AWGN interferers are tabulated for various sensitivity levels and their corresponding I/N ratios.
Signal Power of a above sensitivity
I/N
Difference in MTIPL
10 dB
9.5 dB
0.5 dB
3 dB
0 dB
2 dB
-2.3 dB
1 dB
-5.9 dB
-9.1 dB
-1.5 dB*
* Note that it is challenging to accurately measure maximum tolerable interferer power at very small I/N ratios.
 The MB-OFDM and AWGN interferers have similar impact (within measurement errors) on IEEE a victim receiver.
Dave Magee et al., Texas Instruments

9. January 2004
Impact on AGC (1)
During the last meeting, questions were raised on the impact that interference may have on the AGC for IEEE a devices.
Assumption: IEEE a signal power is 3 dB above receiver sensitivity and the UWB interferer was transmitting at the maximum tolerable interferer power level.
SIFS
MB-OFDM Interferer
Packet Detected
AGC Locked
Start of Packet
AWGN Interferer
The performance of packet detection and AGC convergence is similar for both UWB interferers with the same average power.
Dave Magee et al., Texas Instruments

10. Impact on AGC (2) Assumption:
January 2004
Impact on AGC (2)
Assumption:
IEEE a device operating at 3 dB above sensitivity.
UWB interferer operating at 10 dB higher than the maximum tolerable interferer power level.
The figure illustrates the performance of the AGC algorithm in the presence of a UWB interferer.
AGC convergence and packet detection are not affected even when the UWB power level is higher than the maximum tolerable interferer power level.
SIFS
Packet Detected
MB-OFDM Interferer
Dave Magee et al., Texas Instruments

11. January 2004
Conclusions
We conducted interference measurements to study co-existence between an IEEE a system and a hypothetical Multi-band OFDM UWB system that occupies the U-NII band.
The Multi-band OFDM and AWGN interferers have a similar impact (within measurement error) on an IEEE a victim receiver.
The impulse nature of the Multi-band OFDM interference does not adversely affect the packet detection circuitry and AGC convergence of the IEEE a victim receiver.
Dave Magee et al., Texas Instruments

12. January 2004
Backup slides
Dave Magee et al., Texas Instruments

13. Measurement Results (1)
January 2004
Measurement Results (1)
The BER curves for the IEEE a system are shown below as a function of the UWB interference power and received signal power.
Dave Magee et al., Texas Instruments

14. Measurement Results (2)
January 2004
Measurement Results (2)
The BER curves for the IEEE a system are shown below as a function of the UWB interference power and received signal power.
Dave Magee et al., Texas Instruments

15. Measurement Results (3)
January 2004
Measurement Results (3)
The BER curves for the IEEE a system are shown below as a function of the UWB interference power and received signal power.
Dave Magee et al., Texas Instruments