QUALITY OF SERVICE DURING VERTICAL HANDOVER IN 3G/4G WIRELESS NETWORKS

Sammanfattning: Handover means transferring an on going call or data sessions one cell to another. Handovers occur due to the movement of the mobile user from one area to another area. Handovers are used to prevent an on going call to be disconnected. If we don’t use handovers then whenever a user leaves the area of a particular cell then its on going call is immediately disconnected. The process of handovers requires a number of parameters e.g. what is the handover scheme we are using, how many channels are free. In the handover process we should also keep the QoS up to the standard. Vertical handover may be referred to a process of transferring call connected to a network/data session from one channel connected in a cell to the core network of another. A suitably equipped device may be able to use both technologies at a time, the high speed Wireless LAN and cellular technology. Wireless LAN connections generally provide higher bandwidth but smaller coverage area as compared cellular networks which have lower bandwidth and wide coverage. Thus the user can use a Wireless LAN connection whenever it’s available, while when it isn’t available can switch to a cellular connection as an alternative. Vertical handover refers to automatic switching the communication/data session from one technology to the other. So, it’s different from a horizontal handover among various wireless access points using the same technology. In this thesis we’ll try to find out reason behind the quality degradation during vertical handover and try to suggest improvements to maintain a minimum standard of quality during handover.