14.3.6.1 Overview

A CCA measurement is used to detect a clear channel. Four CCA modes are specified by IEEE 802.15.4-2006:

Table 14-28. CCA Mode Overview
CCA ModeDescription
1

Energy above threshold.

CCA shall report a busy medium upon detecting any energy above the ED threshold.

2

Carrier sense only.

CCA shall report a busy medium only upon the detection of a signal with the modulation and spreading characteristics of an IEEE 802.15.4 compliant signal. The signal strength may be above or below the ED threshold.

0, 3

Carrier sense with energy above threshold.

CCA shall report a busy medium using a logical combination of

  • Detection of a signal with the modulation and spreading characteristics of this standard and
  • Energy above the ED threshold.

Where the logical operator may be configured as either OR (mode 0) or AND (mode 3).