bssgp: Compute and transmit queue delay

The specification 28.018,  allows to transmit the average LLC downlink
queueing delay in FLOW CONTROL BVC messages (BVC Measurement IE, see
GSM 28.018, 10.4.4 and 11.3.7).

This commit extends gprs_bssgp_pcu.cpp to compute the average delay
time between two subsequent FLOW CONTROL BVC messages. The average is
implemented as an arithmetic average without any weighting.

Ticket: OW#1432
Sponsored-by: On-Waves ehf
3 files changed