1. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
August 2001
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Proposed change to CCA specification]
Date Submitted: [25 July 2001]
Source: [Keith Holt] Company [Intel Corporation]
Address [9750 Goethe Road, M/S LOC 3/8, Sacramento, CA 95827]
Voice:[(916) ], FAX: [(916) ],
Re: []
Abstract: [This contribution presents a proposed change to the CCA specification.]
Purpose: [For information only.]
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
Keith Holt, Intel Corporation
<author>, <company>

2. August 2001
Current Wording
Paragraph Receiver CCA Performance currently reads:
“A compliant receiver provides CCA capability by performing energy detection in the received signal bandwidth. The receiver CCA shall report a busy medium upon detecting energy above the energy detect (ED) threshold in a 16 symbol window in the current receive channel. The 16 symbol interval corresponds to the length of a single CAZAC sequency, and is approximately 1.45 usec based on the 11 Msymbol/s symbol rate. The ED threshold shall be equal to –70 dBm integrated over a 16 symbol interval.”
Keith Holt, Intel Corporation

3. August 2001
Issues
Does not indicate by what time relative to the beginning of a transmission when CCA must declare medium busy – only the measurement interval is defined.
11a specifies within 4 usec
11b specifies within 15 usec
It is possible to be able to receive a packet which can be successfully demodulated and yet CCA still declares the medium to be clear.
CCA will declare medium busy with interference from non devices (e.g., Bluetooth)
Absolute power measurement requires some level of calibration
Keith Holt, Intel Corporation

4. August 2001
Proposed Change
Modify paragraph Receiver CCA Performance to read:
“The start of a valid preamble sequence at a receive level equal to or greater than the minimum sensitivity for the QPSK base rate (-75 dBm) shall cause CCA to indicate medium busy with a probability of >90% within four CAZAC periods (approx 5.8 usec). The receiver CCA function shall in all circumstances report medium busy with any signal 20dB above the minimum sensitivity for the QPSK base rate.”
Keith Holt, Intel Corporation

5. Justification Must specify time by which CCA must respond
August 2001
Justification
Must specify time by which CCA must respond
Proposed scheme provides better performance
CCA algorithm should not defer to other devices that are not
CCA algorithm should defer to the greatest extent possible devices which are known to be
Measurement of absolute power is unnecessarily difficult - SNR measurement is simpler to implement
Keith Holt, Intel Corporation