Re: [6tisch] cell rules in MSF

["Pascal Thubert (pthubert)" <[e-mail]>]

Hello Tengfei

The text below:

whether there is any incoming frame on those cells
could be understood like it is a unicast frame to this node.
In fact the text should describe promiscuous listening of traffic between arbitrary nodes.
I’m OK to use carrier sense since an interference is only interesting if it is TSCH.

I would suggest



   As a consequence of randomly cell selection, there is a non-zero

   chance that nodes in the vicinity installed cells with same

   slotOffset and channelOffset.  An implementer MAY implement a

   strategy to monitor the candidate cells before adding them in

   CellList to avoid collision.  For example, a node MAY maintain a

   candidate cell pool for the CellList.  The candidate cells in the

   pool are pre-configured as Rx cells to promiscuously listen to

   detect transmissions on those cells.  If IEEE802.15.4 transmissions

   are observed on one cell over multiple iterations of the schedule,

   that cell is probably used by a TSCH neighbor. It is

   moved out from the pool and a new cell is selected as a candidate

   cell.  The cells in CellList are picked from the candidate pool
   directly when required.


All the best,

Pascal

From: 6tisch <[e-mail]> On Behalf Of Tengfei Chang
Sent: vendredi 23 août 2019 14:11
To: 6tisch <[e-mail]>
Subject: [6tisch] cell rules in MSF

Hi all,

As we discussed in IETF 105, we may need some way to monitor the candidate cells to schedule before adding them.

Hence the following paragraph is added in version 06:


 As a consequence of randomly cell selection, there is a non-zero

   chance that nodes in the vicinity installed cells with same

   slotOffset and channelOffset.  An implementer MAY implement a

   strategy to monitor the candidate cells before adding them in

   CellList to avoid collision.  For example, a node MAY maintain a

   candidate cell pool for the CellList.  The candidate cells in the

   pool are pre-configured as Rx cells to listen whether there is any

   incoming frame on those cells.  If any IEEE802.15.4 frames are

   received within a pre-defined duration on one cell, that cell will be

   moved out from the pool and a new cell is selected as a candidate

   cell.  The cells in CellList are picked from the candidate pool
   directly when required.

Please let me know if you have any comments on this fix. Thanks!

Tengfei

--
Chang Tengfei,
Postdoctoral Research Engineer, Inria