Table 2.

Traffic steering modes in the proposed mmWave HetNet.

Types	Modes	Motivations
Inter-network traffic steering	LTE → LTE-LAA	LTE resource limitation.
	LTE → WiFi	Megabit-level or even lower data rate requirement.
	WiFi → LTE	Overcrowded traffic in WiFi network.
	WiFi → LTE-LAA	High QoS requirements.
	LTE-LAA → LTE	LTE-LAA resource limitation.
	LTE-LAA → WiFi	QoS requirement changes.
	mmWave → LTE-LAA	High propagation loss and easy-to-block channels.
	mmWave → LTE	High user mobility.
	mmWave → WiFi	Energy saving.
	LTE → mmWave	Gigabit-level data rate requirement.
	LTE-LAA → mmWave	Stable user movement.
	WiFi → mmWave	High user density.
Intra-network traffic steering	LTE-LAA → LTE-LAA	Overcrowded traffic in one LTE-LAA cell.
	WiFi → WiFi	The collision probability of one WiFi cell is too high.
	mmWave → mmWave	Overcrowded in one mmWave cell. Small mmWave coverage. Energy saving.