PDCP_FIFO NETLINK limited bandwidth in noS1 mode

Description

In noS1 mode, IP packets are read by PDCP layer using Netlink connexion with the nas_mesh driver. A netlink read transaction is composed of two socket reads (first descriptor, second data which contains the IP frame to be send). Due to a implementation bug, only one socket read was done every 1ms (PDCP scheduling opportunity given by the mac layer). Then 2 ms were required to get one IP frame form the nas_mesh driver resulting in limited bandwidth.

Correction

check if there are still message to read in the socket before leaving PDCP layer. Limitation : this is a quick fix and flow control is not handle. To prevent OAI stack overflow from iperf UDP, a limitation of 3 IP frames (int rlc_data_req_flag = 3;) is implemented.

Detected in version : v1B0.6

Impact : both UE and eNB.

Results:

On v1B0.7 with correction we can achieve 14Mbps in downlink (iperf UDP mode) with the following configuration : noS1 band7 5MHz mcs 28 UM mode