November 2001
IEEE P802.15-01/522r0
IEEE P802.15
Wireless Personal Area Networks
Project
IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)
Title
802.15.4 CCA Method
Date
Submitted
November 14, 2001
Source
[Pat Kinney]
[Invensys]
[1501 Ardmore Blvd]
[Pittsburgh, PA]
Voice:
Fax:
E-mail:
[724-425-7952]
[]
[pat.Kinney@ieee.org]
Re:
Abstract
Description of CCA for the 802.15.4 Physical Layer
Purpose
To support the motion to change the 802.15.4 CCA method
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(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 P802.15.
Submission
Page 1
Pat Kinney, Invensys
November 2001
IEEE P802.15-01/522r0
The 802.15.4 PHY shall provide the capability to perform CCA according to at least one
of the following five methods:
 CCA Mode 1: Energy above threshold. CCA shall report a busy medium upon
detecting any energy above the ED threshold.
 CCA Mode 2: Carrier sense only. CCA shall report a busy medium only upon the
detection of a DSSS signal. This signal may be above or below the ED threshold.
 CCA Mode 3: Carrier sense with energy above threshold. CCA shall report a
busy medium upon the detection of a DSSS signal with energy above the ED
threshold.
 CCA Mode 4: Carrier sense with timer. CCA shall start a timer whose duration is
TBD ms and report a busy medium only upon the detection of a High Rate PHY
signal. CCA shall report an IDLE medium after the timer expires and no High
Rate PHY signal is detected. The TBD ms timeout is the duration of the longest
possible PSDU.
 CCA Mode 5: A combination of carrier sense and energy above threshold. CCA
shall report busy at least while a High Rate PPDU with energy above the ED
threshold is being received at the antenna.
The energy detection status shall be given by the PMD primitive, PMD_ED. The carrier
sense status shall be given by PMD_CS. The status of PMD_ED and PMD_CS is used
in the PLCP convergence procedure to indicate activity to the MAC through the PHY
interface primitive PHY-CCA.indicate.
A busy channel shall be indicated by PHY-CCA.indicate of class BUSY.
Clear channel shall be indicated by PHY-CCA.indicate of class IDLE.
The PHY PIB attribute aCCAModeSuprt shall indicate the appropriate operation modes.
The PHY shall be configured through the PHY MIB attribute aCurrentCCAMode. The
CCA shall be TRUE if there is no energy detect or carrier sense. The CCA parameters
are subject to the following criteria:
a) The energy detection threshold shall be less than or equal to TBD dBm.
b) With a valid signal (according to the CCA mode of operation) present at the receiver
antenna within TBD ms of the start of a MAC slot boundary, the CCA indicator shall
report channel busy before the end of the slot time. This implies that the CCA signal is
available as an exposed test point.
c) In the event that a correct PLCP Header is received, the PHY shall hold the CCA
signal inactive (channel busy) for the full duration as indicated by the LENGTH field.
Should a loss of carrier sense occur in the middle of reception, the CCA shall indicate a
busy medium for the intended duration of the transmitted packet.
Conformance to PHY CCA shall be demonstrated by applying a compliant signal, above
the appropriate ED threshold (a), such that all conditions described in b) and c) above
are demonstrated.
Submission
Page 2
Pat Kinney, Invensys