Explain the difference between Cell Reselection and Handover in 2G network?
In 2G, 3G and 4G cellular networks, Cell reselection and handover are both mechanisms used to maintain a seamless connection for mobile devices as they move between different cell sites. However, in 3G and 4G there are some advanced features and difference in how the techniques, processes are implemented and managed.
a) Cell Reselection:
- Purpose: Cell reselection is primarily used when a mobile device detects that the signal strength or quality from the current serving cell is deteriorating, possibly due to the user moving away from that cell or interference.
- Trigger: It is triggered by the mobile device itself based on predefined criteria such as signal strength thresholds. When these criteria are met, the device autonomously searches for and selects a better cell to connect to.
- Network Involvement: The network is not actively involved in the reselection process initiated by the mobile device. The device independently scans neighboring cells and decides which one to reselect.
Cell reselection is different from handover in that it doesn’t involve transferring an ongoing call or data session from one cell to another. Instead, it’s about the device choosing a better cell for initial or continued communication.
b) Handover:
- Purpose: Handover (also known as handoff) is used to transfer an ongoing call or data session from one cell to another without interrupting the connection.
- Trigger: Handovers are typically initiated by the network when it detects that a mobile device is moving out of the coverage area of its current serving cell or when the quality of the connection becomes poor.
- Network Involvement: Unlike cell reselection, handover involves active participation from the network infrastructure. The network manages the handover process, including coordinating with the source and target cells to ensure a seamless transition for the ongoing communication.
- Timing: Handovers are typically performed during an active call or data session to ensure continuity of service as the mobile device moves across different cells.
So generally, cell reselection is about a mobile device autonomously selecting a better cell based on signal criteria, while handover is a network-managed process to transfer ongoing communication sessions between cells to maintain connectivity as a device moves.
In 2G networks, cell reselection and handover are basic mechanisms for maintaining mobile connectivity. Cell reselection allows devices to autonomously switch to better cells based on signal strength, while handover transfers ongoing calls or data sessions between cells as devices move.