“…9. Step 1, 8, 11, 12 are the messages of vertical handoff processes [35][36][37][38][39][40][41][42][43] through Vertical_Handoff REQ and Vertical_Handoff RSP. Besides, Step 13,14,15,16 are the key procedures of QoS Transparency Guarantees [44][45][46][47][48][49][50]. Users can extend QoS classes through the messages of QoS_Transparency_REQ and QoS_Transparency_RSP.…”