Method macComputeUtilization

GPRS/MAC.cpp:2097–2126

Compute a measure of GPRS channel utilization so we can decide when we need more bandwidth. For now we will compute only downlink bandwidth and ignore uplink. You cant just count how many RLC blocks are in TBFs, because the associated MS could be stalled and the TBF may not be using any bandwidth. The utilization is the approximate number of TBFs that are waiting to send blocks now, so 1.0 means t

// probably fully utilize two channels, at least at this instant.
// Return the utilization.
float L2MAC::macComputeUtilization()
{
	ScopedLock lock(macLock);	// This function called from CLI.
	int numReady = 0;
	float utilization = 0.0;	// Desired downlink utilization at this moment.
	TBF *tbf;
	RN_MAC_FOR_ALL_TBF(tbf) {
		switch (tbf->mtGetState()) {
			case TBFState::DataReadyToConnect:
			case TBFState::DataWaiting1:
			case TBFState::DataWaiting2:
				numReady++;		// These TBFs are waiting to send a message.
				continue;
			case TBFState::DataTransmit:
			case TBFState::DataReassign:
			//case TBFState::DataStalled:
				utilization += tbf->engineDesiredUtilization();
				continue;
			default: continue;
		}
	}
	utilization += numReady;

	// We want to average the utilization over some timespan.
	// This number should be picked to match the delay we use before closing
	// GPRS chanels, whatever that will be.
	const unsigned NumFramesToAverage = 48*5;	// roughly 5 seconds worth of RLC blocks.
	return macDownlinkUtilization =
		(utilization + macDownlinkUtilization * (NumFramesToAverage-1)) / NumFramesToAverage;
}

void L2MAC::macCheckChannels()
{