Voice roaming fallback refers to the process and mechanisms implemented in mobile networks to ensure that a subscriber can maintain voice communication when the primary network service is unavailable or of poor quality. This is particularly crucial in areas with weak network coverage or when transitioning between different networks. This article will delve into the concept of voice roaming fallback, its importance, the technologies involved, and practical examples.
Introduction to Voice Roaming
Voice roaming occurs when a mobile subscriber uses their mobile phone outside the coverage area of their home network. This can happen for various reasons, such as traveling or living in a region with limited network coverage. When voice roaming is enabled, the subscriber’s call is routed through a foreign network provider, often resulting in additional charges.
Importance of Voice Roaming Fallback
The primary goal of voice roaming fallback is to ensure that subscribers can continue making and receiving calls even when the primary network is not available. This is particularly important for emergency calls, business communications, and personal connections. Without voice roaming fallback, subscribers would be left without a means of communication in areas with poor network coverage.
Technologies Involved in Voice Roaming Fallback
1. Handover Technology
Handover technology is essential for voice roaming fallback. It enables a mobile device to switch from one network to another seamlessly, without dropping the call. There are several types of handover technologies:
- Hard Handover: The old connection is terminated before the new one is established.
- Soft Handover: The new connection is established while the old one is still active, minimizing call interruption.
- Hybrid Handover: A combination of hard and soft handover techniques.
2. Signaling Protocols
Signaling protocols are used to exchange information between mobile devices and network elements. Common signaling protocols for voice roaming fallback include:
- Mobile Switching Center (MSC): Coordinates call routing and switching in a mobile network.
- Home Location Register (HLR): Stores subscriber information, such as location and subscription details.
- ** Visitor Location Register (VLR)**: Contains temporary information about subscribers visiting a foreign network.
3. Inter-System Handover (ISHO)
Inter-system handover (ISHO) is a handover process between different radio access technologies (RATs), such as 2G and 3G or 3G and 4G. ISHO is crucial for voice roaming fallback, as it allows subscribers to maintain voice calls when transitioning between different technologies.
Practical Examples
Example 1: 4G to 3G Roaming Fallback
When a subscriber is using a 4G network and moves to an area with poor 4G coverage, their device automatically switches to the 3G network. The handover process is seamless, and the subscriber can continue making voice calls without interruption.
Handover Process:
1. The subscriber's device detects poor 4G coverage.
2. The device initiates a soft handover to the 3G network.
3. The network establishes a new connection on the 3G network.
4. The call continues without interruption.
Example 2: 2G to 3G Roaming Fallback
In some regions, 2G networks are still in use. When a subscriber moves from a 2G-covered area to a 3G-covered area, their device switches to the 3G network to maintain voice communication.
Handover Process:
1. The subscriber's device detects the transition from 2G to 3G coverage.
2. The device initiates an ISHO to the 3G network.
3. The network establishes a new connection on the 3G network.
4. The call continues without interruption.
Conclusion
Voice roaming fallback is a critical component of mobile network infrastructure, ensuring that subscribers can maintain voice communication even in areas with poor network coverage. By utilizing handover technologies, signaling protocols, and inter-system handover, mobile networks can provide seamless voice roaming experiences for their subscribers.