Understanding Soft Handover

Oct 13, 2025 by talynt.org 110 views

Introduction

Soft handover is an algorithm used to move User Equipment (UE) from one eNodeB to another when the Reference Signal Received Power (RSRP) signal from the eNodeB that serves is weakening due to increasing distances with the movement of the UE. This algorithm applies the concept of "Make-Before-Break", which means the UE will be connected first to the new eNodeB before deciding the connection with the old eNodeB. With this advantage, Soft Handover offers better service quality than the hard handover algorithm, so it is very possible to be applied in the Time Division Duplex Long Term Evolution (TDD-LTE) system to maintain Quality of Service (QoS).

Understanding Soft Handover

Soft handover is a critical component of the TDD-LTE system, as it ensures that UE remains connected to a strong signal when moving from one eNodeB to another. The algorithm works by continuously monitoring the RSRP signal from the serving eNodeB and the neighboring eNodeBs. When the RSRP signal from the serving eNodeB weakens, the algorithm initiates a handover process, where the UE is connected to a stronger eNodeB. This process is known as "Make-Before-Break", where the UE is connected to the new eNodeB before deciding the connection with the old eNodeB.

Performance Evaluation of Soft Handover

The performance of the Soft Handover algorithm is influenced by several main components, namely the value of margin threshold and margin hysteresis. Both of these parameters have a significant effect on three main aspects: the average measure of active set, outage probability ratio, and the number of handovers that occur.

Margin Threshold and Margin Hysteresis

The margin threshold and margin hysteresis are two critical parameters that affect the performance of the Soft Handover algorithm. The margin threshold is the minimum RSRP signal strength required for a UE to remain connected to a particular eNodeB. The margin hysteresis, on the other hand, is the difference between the RSRP signal strength of the serving eNodeB and the neighboring eNodeBs.

When the margin of threshold and hysteresis are increased, the average active set size tends to increase, which shows that more eNodeBs are involved in the handover process. This can help ensure that the UE remains connected to a strong signal when moving from one eNodeB to another.

Outage Probability Ratio

Further analysis shows that the outage probability ratio reaches the highest value at -90 dBm for a distance of 611 meters and 1611 meters, with a value of 0.8813 and 0.455 respectively. This value shows the potential for termination of services due to radio link failure, which occurs when the RSRP value received by the UE is below the specified threshold value. This situation can result in loss of connections and poor service quality for users.

Number of Handovers

However, the number of handovers that occur tends to be constant, with an average handover for each application of hysteresis and threshold margin values. This shows that although the signal quality is reduced, the algorithm continues to handover efficiently without significantly increasing handover frequencies.

Conclusion

Overall, the evaluation of the performance of the Soft Handover algorithm in the TDD-LTE system shows that by adjusting the proper margin threshold and hysteresis, better and more stable performance can be achieved. Efforts to improve this setting are very important to increase QoS and provide better user experience in the cellular communication system. The combination of this algorithm with other advanced technology can be an effective solution to deal with challenges in UE movements in complex environments.

Recommendations

Based on the evaluation of the Soft Handover algorithm, the following recommendations are made:

Optimize Margin Threshold and Margin Hysteresis: The margin threshold and margin hysteresis should be optimized to ensure that the UE remains connected to a strong signal when moving from one eNodeB to another.
Implement Advanced Handover Techniques: Advanced handover techniques, such as "Make-Before-Break", should be implemented to ensure that the UE is connected to a stronger eNodeB before deciding the connection with the old eNodeB.
Combine with Other Advanced Technologies: The Soft Handover algorithm should be combined with other advanced technologies, such as beamforming and massive MIMO, to improve the performance of the TDD-LTE system.

Future Work

Future work should focus on the following areas:

Further Optimization of Margin Threshold and Margin Hysteresis: Further optimization of the margin threshold and margin hysteresis is necessary to ensure that the UE remains connected to a strong signal when moving from one eNodeB to another.
Implementation of Advanced Handover Techniques: Advanced handover techniques, such as "Make-Before-Break", should be implemented to ensure that the UE is connected to a stronger eNodeB before deciding the connection with the old eNodeB.
Combination with Other Advanced Technologies: The Soft Handover algorithm should be combined with other advanced technologies, such as beamforming and massive MIMO, to improve the performance of the TDD-LTE system.
Frequently Asked Questions (FAQs) about the Soft Handover Algorithm on the TDD-LTE System =====================================================================================

Q: What is Soft Handover?

A: Soft handover is an algorithm used to move User Equipment (UE) from one eNodeB to another when the Reference Signal Received Power (RSRP) signal from the eNodeB that serves is weakening due to increasing distances with the movement of the UE.

Q: What is the concept of "Make-Before-Break" in Soft Handover?

A: The concept of "Make-Before-Break" in Soft Handover means that the UE will be connected first to the new eNodeB before deciding the connection with the old eNodeB.

Q: What are the main components that affect the performance of the Soft Handover algorithm?

A: The main components that affect the performance of the Soft Handover algorithm are the value of margin threshold and margin hysteresis.

Q: What is the effect of increasing the margin threshold and margin hysteresis on the average active set size?

A: When the margin of threshold and hysteresis are increased, the average active set size tends to increase, which shows that more eNodeBs are involved in the handover process.

Q: What is the outage probability ratio, and how does it affect the performance of the Soft Handover algorithm?

A: The outage probability ratio is the probability of termination of services due to radio link failure, which occurs when the RSRP value received by the UE is below the specified threshold value. This situation can result in loss of connections and poor service quality for users.

Q: How does the number of handovers affect the performance of the Soft Handover algorithm?

A: The number of handovers that occur tends to be constant, with an average handover for each application of hysteresis and threshold margin values. This shows that although the signal quality is reduced, the algorithm continues to handover efficiently without significantly increasing handover frequencies.

Q: What are the recommendations for improving the performance of the Soft Handover algorithm?

A: The recommendations for improving the performance of the Soft Handover algorithm are:

Optimize Margin Threshold and Margin Hysteresis: The margin threshold and margin hysteresis should be optimized to ensure that the UE remains connected to a strong signal when moving from one eNodeB to another.
Implement Advanced Handover Techniques: Advanced handover techniques, such as "Make-Before-Break", should be implemented to ensure that the UE is connected to a stronger eNodeB before deciding the connection with the old eNodeB.
Combine with Other Advanced Technologies: The Soft Handover algorithm should be combined with other advanced technologies, such as beamforming and massive MIMO, to improve the performance of the TDD-LTE system.

Q: What are the future work areas for improving the performance of the Soft Handover algorithm?

A: The future work areas for improving the performance of the Soft Handover algorithm are:

Further Optimization of Margin Threshold and Margin Hysteresis: Further optimization of the margin threshold and margin hysteresis is necessary to ensure that the UE remains connected to a strong signal when moving from one eNodeB to another.
Implementation of Advanced Handover Techniques: Advanced handover techniques, such as "Make-Before-Break", should be implemented to ensure that the UE is connected to a stronger eNodeB before deciding the connection with the old eNodeB.
Combination with Other Advanced Technologies: The Soft Handover algorithm should be combined with other advanced technologies, such as beamforming and massive MIMO, to improve the performance of the TDD-LTE system.

Q: What are the benefits of using the Soft Handover algorithm on the TDD-LTE system?

A: The benefits of using the Soft Handover algorithm on the TDD-LTE system are:

Improved QoS: The Soft Handover algorithm ensures that the UE remains connected to a strong signal when moving from one eNodeB to another, resulting in improved QoS.
Reduced Handover Frequencies: The Soft Handover algorithm reduces handover frequencies, resulting in improved network performance.
Improved User Experience: The Soft Handover algorithm provides a better user experience by ensuring that the UE remains connected to a strong signal when moving from one eNodeB to another.