NS3 log Time precision

I am using NS3.20 to find the time stamps of packet being sent from a node to another node in a FAT-TREE topology using the command

NS_LOG= "*=level_info|prefix_func|prefix_time|prefix_node" ./waf --run scratch/fat-tree &> save-log.txt

After grepping few selected lines containing info about pkt 196.The output is of the form

Timestamp, Nodeid, Functioncalled, DevNo, pktid

Example lines are as follows

1.74547s 34 CsmaChannel:TransmitStart(): UID is 196)
1.74548s 34 CsmaChannel:TransmitEnd(): UID is 196)
1.74548s 23 Node:ReceiveFromDevice(): Node 23 ReceiveFromDevice:  dev 2 (type=ns3::CsmaNetDevice) Packet UID 196
1.74548s 23 BridgeNetDevice:ReceiveFromDevice(): UID is 196
1.74548s 23 CsmaChannel:TransmitStart(): UID is 196)
1.74548s 34 CsmaChannel:PropagationCompleteEvent(): UID is 196)
.
.
.

For my research I need the time stamps to be in nanoseconds. Is there a way to configure this? NB : I tried cout, and fout within the functions but it just prints time without the node_id which is useless for me.

Please help