[as I happen to have 802.15.4-2015 open, here are suitable references
to it...]
Suresh Krishnan writes:
> Section 3:
>
> CCA: Clear Channel Assessment.
>
> - Can you provide a description or a reference? This is not in the
> terminology document. Is this the same CCA as WiFi?
CCA for TSCH is to help it work with other radio networks in same
band, it is ineffective against other nodes in TSCH network.
This is described in the 802.15.4-2015 section 6.2.5.2 TSCH CCA
algorithm:
6.2.5.2 TSCH CCA algorithm
When a device is operating in TSCH mode as described in 6.3.6,
CCA may be used to promote coexistence with other users of the
radio channel. For other devices in the same network, the
start time of transmissions, macTsTxOffset, is closely aligned
making intra-network collision avoidance using CCA
ineffective. TSCH devices also use channel hopping so there is
no backoff period used when CCA prevents a transmission.
...
> Section 5
>
> - When preparing the security header, the Absolute Sequence Number
> (ASN) MUST be written into the Nonce in most significant byte first
> (MSB) format as indicated in the IEEE 802.15.4 specification
> [IEEE802154-2015]
>
> Please provide a section reference into the 802.15.4 document
Nonce generation in 802.15.4-2015 is described in the section "9.3.2.2
CCM* nonce for TSCH mode".
Byte order is specified in the section "9.3.1 Integer and octet
representation", which then referes to the B.2, and B.2.2. tells
crypto uses MSB order (most of the other things in 802.15.4 is in
LSB).
--
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