A hard handover is a type of mobile handover (specifically, a horizontal handover) where the connection with the current access point (AP) or base station is completely broken before a new connection is established with the target AP. In essence, the mobile node (MN) communicates with only one AP at any given time.
Key Characteristics of Hard Handover:
- Break-Before-Make: This is the defining characteristic. The connection with the source AP is terminated before the connection to the target AP is established. This contrasts with soft handover, where both connections exist simultaneously for a short period.
- Interruption in Service: Due to the "break-before-make" nature, hard handover typically results in a brief interruption in service or connectivity. This interruption can be noticeable to the user, depending on the implementation and network conditions.
- Simpler Implementation: Compared to soft handover, hard handover is generally simpler to implement from a network perspective, as it requires less coordination between access points.
- Suitable for Certain Technologies: Hard handover is commonly used in technologies like GSM (Global System for Mobile Communications) and older versions of UMTS (Universal Mobile Telecommunications System) where the complexities of soft handover are not warranted or supported.
Example Scenario:
Imagine you are on a phone call while driving and moving from one cell tower's coverage area to another. With hard handover:
- Your phone disconnects from the first cell tower.
- There's a brief period where you have no signal.
- Your phone then connects to the second cell tower, and your call resumes (hopefully!).
Advantages and Disadvantages:
| Feature | Hard Handover |
|---|---|
| Complexity | Simpler to implement |
| Service Interruption | Yes, brief interruption expected |
| Coordination | Less coordination required between APs |
| Resource Usage | Lower resource usage |
| Network Types | GSM, Older UMTS |
When is Hard Handover Used?
Hard handover is typically used in scenarios where:
- The network technology doesn't easily support simultaneous connections to multiple access points.
- The cost and complexity of implementing soft handover outweigh the benefits.
- A short interruption in service is acceptable.
In more modern cellular technologies like LTE (Long-Term Evolution) and 5G, other handover techniques, including soft handover variants, are often preferred to minimize service interruptions and improve user experience. However, hard handover may still be used in specific situations within these networks.
