Re: [Contiki-developers] RPL Objective Function Metrics Doubts

[Pablo C. P. <pau...@gm...>]

Hi Mahtab,

Thank you very much for your answer! I did not take a look at that function
and now those things are clear.

Do you know anything about the "energy_est" parameter? According to RFC
6551, it depends on the type of power source. If the mote is battery
powered, it should be the ratio of desired max power to actual power or if
the energy in the battery can be estimated together with the lifetime, then
the energy estimation could be E_E = E_bat / [E_0 (T-t)/T].

However, I do not find anywhere in the code if the energy_est is computed
that way or not. Does anyone know about how it is calculated?

Best Regards,
Pablo Corbalán


2014-08-28 18:20 GMT+01:00 Mahtab Hossain <mah...@ya...>:

> Hi Pablo:
>
> For the Link Metric value (assuming the default ETX), you may look inside:
> ../core/net/rpl/rpl-mrhof.c file. Everytime, a link layer receives an ACK
> or time-out event (after few restransmission), the function inside this
> file (neighbor_link_callback) is fired. ETX is computed as the moving
> average with some formula like:
>
> new_etx = recorded_etx (so far) * 0.9 + packet_etx (current packet
> success/failure including retransmission) * 0.1
>
> link_metric is the ETX to the parent, and path_metric is the total ETX
> towards the sink if you choose that neighbor as parent.
>
> --- Mahtab
>
>
>
>   On Thursday, August 28, 2014 1:08 PM, Pablo Corbalán Pelegrín <
> pau...@gm...> wrote:
>
>
> Hi,
>
> I am working on creating a modified version of MRHOF for RPL. However, I
> have some doubts about the metrics used, i.e., link_metric and energy_est.
>
> Can anyone tell me how the link_metric value and energy_est are calculated?
>
> I have seen in rpl-icmp6.c that:
> dio.mc.obj.energy.energy_est = buffer[i + 7];
>
> And in rpl-dag.c that:
> p->link_metric = RPL_INIT_LINK_METRIC * RPL_DAG_MC_ETX_DIVISOR;
>
> However, I do not really understand the meaning of those values and I do
> not know what energy_est contains.
>
> So, is the link_metric just a value to define the cost to the parent? And
> is the path_metric the cost from the best parent to the RPL root or it also
> contains the link_metric to the parent?
>
> Thanks in advance.
>
> Best Regards,
> Pablo Corbalán
>
>
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-- 
Saludos,
Pablo Corbalán Pelegrín