Note: This article has been updated for 2025 to reflect the latest advancements in handoff technology and its impact on modern wireless and mobile communication networks, including 5G and beyond. We’ve included detailed comparisons, new handoff types, and their applications in today’s telecommunications landscape.
Seamless connectivity is crucial in wireless and mobile communication, especially when users move between network coverage areas. Handoff (or handover) ensures uninterrupted service by smoothly transferring an ongoing call or data session between cell towers. Without effective handoff techniques, users may experience dropped calls, network disruptions, or slow data transmission.
To understand how handoff works in mobile networks, check out our guide on the architecture of a mobile communication system. In this article, we’ll break down:
- What is handoff in mobile communication?
- The different types of handoff (soft, hard, forced, delayed, etc.)
- Handoff process and techniques used in cellular networks
- Advantages and disadvantages of each handoff type
With 5G and upcoming 6G technologies, handoff mechanisms have evolved significantly, leveraging AI, machine learning, and network slicing for better efficiency. In this article, we’ll explore different types of handoffs, from traditional GSM/CDMA techniques to AI-powered predictive handoffs in 5G and future networks.
Contents
The Need for Handoff in Wireless Communication
- One of the building blocks of cellular communication is mobility, which refers to providing users with the freedom of movement while they still are connected to the network.
- Handoffs play a major role in allowing users to move across cells without the fear of being disconnected.
- It is also to be noted that a handoff may also be triggered when the number of subscribers in a particular cell has already reached the cell’s maximum limit, keeping the network safe from the threat of being congested and overloaded.
- It can be assumed to be an example of “make before break” as a standby connection is supposed to be present before the switch is done.
Types of Handoffs in Mobile Networks
There are various types of handoffs as listed below, each of which are used in different scenarios.
- Soft handoff
- Hard handoff
- Forced handoff
- Delayed handoff
- Mobile-Assisted handoff
- Intersystem handoff
- Intercell handoff
- Intracell handoff
Next, we will have a look at the above types of handoffs, their advantages and disadvantages, and where they are used. First, we will see inter-MSC handoffs, which are the ones that occur when the user moves from one MSC to another.
| Handoff Type | Used In | Best For | Key Benefit |
| Soft Handoff | CDMA (outdated) | Legacy networks | Reduced call drops |
| Hard Handoff | GSM, LTE, 5G | Modern cellular networks | Efficient frequency use |
| AI-Assisted Handoff | 5G, 6G | Smart mobility | Predictive & seamless transitions |
| Mobile-Assisted Handoff | GSM, LTE | High mobility areas | Faster switching |
| Intersystem Handoff | LTE, 5G, Satellite | Roaming & hybrid networks | Connectivity across different networks |
Soft Handoff in Mobile Communication
Soft Handoff is a feature where a cellular device gets connected to two or more cell BTS (or cell sectors) at the same time. If all the sectors to which the MS is connected to are from the same cell, then it is referred to as a Softer Handoff.
Advantages of Soft Handoff
- It provides better Quality Assurance as a channel is always on stand by in case of power loss in any other channel.
- More than one repeater can send and receive signals to transmit signals to and from mobiles, increasing transfer speed.
- Delay is very low
- Soft Handoffs lead to an increase in the signal to interference ratio, without performance loss. This is known as the Soft Handover Gain.
Disadvantages of Soft Handoff
- Only supported for phones that employ CDMA/ WCDMA, and cannot be implemented in LTE, 5G, or GSM.
- Costlier to implement than Hard Handoff as a channel is always wasted by being the backup.
Where is Soft Handoff Used?
Soft Handoffs are generally used in MS that employ Code Division Multiple Access (CDMA) or Wideband CDMA (WCDMA), and its associated services, and also in applications that require a continuous connection throughout, possibly for security purposes.
Hard Handoff in Mobile Networks
Hard Handoff is a technique that requires the user’s connection to be broken before connecting to another while switching between two BTS and hence is equivalent to “breaking before making”. It is generally implemented in Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA) based devices and is implemented when the subscriber/user is being connected to a base station with a different radio frequency than the current base station. The following image shows the difference between Soft and Hard Handovers.
Advantages of Hard Handoff
- Hard Handovers are cheaper as they require only one channel to be active at a time.
- Hard Handoffs are generally implemented more than Soft Handoffs thanks to their efficiency.
- More efficient in LTE, 5G, and Wi-Fi networks.
Disadvantages of Hard Handoff
- A delay is often experienced while switching, but it generally is quite small such that the user does not experience it. 5G beamforming minimizes this issue.
Where is Hard Handoff Used?
Apart from being implemented in FDMA and TDMA devices, Hard Handoffs are also used in applications that can afford slight delays, such as VoIP, Internet, and WiMAX.
AI-Assisted Handoff (Used in 5G and Future 6G Networks)
Modern AI-powered handoffs predict signal strength fluctuations based on user movement, optimizing the transfer process.
Advantages of AI-Assisted Handoff
- Uses Machine Learning (ML) to predict optimal handoff timing
- Reduces latency and improves suer experience.
- Enhances connectivity in autonomous vehicles and smart cities.
Disadvantages of AI-Assisted Handoff
- Requires advanced AI infrastructure, increasing implementation costs.
Where is AI-Powered Handoff Used?
AI-Powered Handoff is used in 5G, 6G, smart cities, autonomous vehicles.
Forced Handoff in Mobile Communication
A Forced Handoff can occur in two ways, either by forcing a handoff to occur or forcibly preventing a handoff that was supposed to happen from not happening. This could be done when the number of users exceeds the capacity of the network.
Advantages of Forced Handoff
- Helps in mobility management by controlling which devices are to remain connected.
- Prevents the network from the threat of being down due to congestion.
Disadvantages of Forced Handoff
- Increased chances of high latency and dropped calls.
Where is Forced Handoff Used?
Forced Handoffs are generally used for security and surveillance purposes, and also to manage network traffic better.
Delayed Handoff in Wireless Communication
A delayed handoff occurs when no BTS is available to accept the transfer. In such a case, the call generally continues until the signal strength reaches a certain threshold. If it goes below the threshold, the call is dropped.
Advantages of Delayed Handoff
- Help in handling the call more adequately.
Disadvantages of Delayed Handoff
- The quality of the call could go for a toss.
- Chances of calls being dropped are very high.
Where is Delayed Handoff Used?
Delayed handoffs are generally used when users are somewhere where dead spots (areas where there is no network coverage) are quite common.
Mobile-Assisted Handoff in Cellular Networks
A mobile-assisted handoff (MAHO) is a process used specifically in GSM networks where a mobile phone assists or helps the BTS to transfer a call to another BTS, with stronger signal strength and improved connectivity.
Advantages of Mobile-Assisted Handoff
- Reduced handoff time as the device is responsible for facilitating the handoff.
- Reduced traffic at the BSC/ MSC as the decision to switch is taken by the MS.
- Suitable when handoffs are frequent.
Disadvantages of Mobile-Assisted Handoff
- Added load on the processor of the MS in comparing signal strength of nearby BTS.
Where is Mobile-Assisted Handoff Used?
They are primarily used in GSM devices, which is based on the TDMA technique.
Intersystem Handoff in Mobile Communication
Intersystem Handoffs come into play when the user moves from one network that is under the jurisdiction of an MSC to another. During this handoff, the call is transferred to the destination MSC, which further tries to allocate a specific bandwidth at the cell site where the user is at present.
Advantages of Intersystem Handoff
- Facilitates roaming and preserves the mobility promise of cellular networks.
Disadvantages of Intersystem Handoff
- This is only possible if the two MSCs are compatible and have the necessary software that can facilitate these handoffs.
Where is Intersystem Handoff Used?
Intersystem Handoffs are used when the user moves from one system to another.
The handoffs that we just saw are those that happen between two MSCs. Handoffs also happen between two BTSs or cells as well, which we will have a look at in this section.
Intercell Handoffs in Wireless Networks
An intercell handoff occurs when an MS is transferred from one BTS to the other, mostly to balance the load on the network. It is generally the BSC that takes control here and acts as the switching agent.
Intracell Handoffs in Wireless Networks
Intracell Handoffs are those that occur between two physical channels within the same cell. The frequency of the channel is changed generally due to interference or similar reasons. Here, the MS remains connected to the same BTS throughout the process.
Handoff is a critical process in mobile networks, enabling users to maintain seamless connectivity as they move between different cell towers or coverage areas. Understanding the various types of handoff, from soft to intersystem, equips engineers and mobile users alike with the knowledge to appreciate the technical efforts that go into ensuring uninterrupted service.
As the mobile communication landscape continues to evolve with technologies like 5G, efficient handoff mechanisms will only grow in importance, especially in ensuring robust, high-speed connectivity in increasingly complex network environments.
If you found this topic interesting and want to dive deeper into how mobile networks efficiently manage communication traffic, you might want to explore Multiple Access Schemes for Wireless Communication. These schemes play an essential role in determining how multiple users can access the same network resources without interference, complementing the functionality of handoff systems. By understanding these schemes, you’ll gain further insights into the foundations of wireless communication and its optimization.
Image Credits: Prof. W.-G. Teng, “Wireless & Mobile Networks”, NCKU ES
