[LENA] Question regarding allocation map creation inside the UL scheduler

[Vikram Chandrasekhar]

Hi NS3-Experts,

I noticed something odd inside the NS3 uplink scheduler which may be a possible bug.

Within each UL scheduler, I see the following lines:

if (nflows == 0)

{

    if (ret.m_dciList.size () > 0)

    {

        m_schedSapUser->SchedUlConfigInd (ret);

    }

   return; // no flows to be scheduled

}

Since the yellow highlighted region of the code causes the NS3 to exit the scheduler, therefore the parameter m_allocationMaps may not be created at all (if there are no LC flows to schedule in current subframe). This may be problematic if there are no new flows but HARQ retransmissions. To elaborate, prior to this section of the code, the UL-HARQ processing occurs. If we have a scenario where there are no new flows, but a HARQ retransmission, then the current code will not update the variable m_allocationMap at all. 

My question is whether this was done intentionally or whether the correct behavior would be the following fix (green highlighted):

if (nflows == 0)

{

    if (ret.m_dciList.size () > 0)

    {

        m_allocationMaps.insert (std::pair <uint16_t, std::vector <uint16_t> > (params.m_sfnSf, rbgAllocationMap));

        m_schedSapUser->SchedUlConfigInd (ret);

    }

   return; // no flows to be scheduled

}

Thank you in advance,

Vikram 

[Marco Miozzo]

Hi Vikram,

sorry for the late reply.

Definitely it seems a bug, I've made a couple of tests and it seems that your patch works.

I've modified the ns-3-dev code and pushed the changes in the main tree, see changeset:   10672:53870483ef76.

Many thanks for you help!

Regards,

marco.

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[Vikram Chandrasekhar]

Many thanks, Marco.

Best regards

Vikram

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