Improved Handover Through Dual Connectivity in 5G mmWave Mobile Networks (1611.04748v3)

Abstract: The millimeter wave (mmWave) bands offer the possibility of orders of magnitude greater throughput for fifth generation (5G) cellular systems. However, since mmWave signals are highly susceptible to blockage, channel quality on any one mmWave link can be extremely intermittent. This paper implements a novel dual connectivity protocol that enables mobile user equipment (UE) devices to maintain physical layer connections to 4G and 5G cells simultaneously. A novel uplink control signaling system combined with a local coordinator enables rapid path switching in the event of failures on any one link. This paper provides the first comprehensive end-to-end evaluation of handover mechanisms in mmWave cellular systems. The simulation framework includes detailed measurement-based channel models to realistically capture spatial dynamics of blocking events, as well as the full details of MAC, RLC and transport protocols. Compared to conventional handover mechanisms, the study reveals significant benefits of the proposed method under several metrics.

• The paper introduces a dual connectivity architecture that minimizes handover latency by maintaining simultaneous 4G and 5G connections.
• It employs an uplink-based measurement framework with dynamic Time-to-Trigger to achieve precise beam alignment and prompt switching.
• Simulation results demonstrate increased throughput, improved stability, and reduced packet loss compared to traditional handover methods.

Improved Handover Through Dual Connectivity in 5G mmWave Mobile Networks

The paper entitled "Improved Handover Through Dual Connectivity in 5G mmWave Mobile Networks" tackles a significant challenge in deploying fifth-generation (5G) mobile systems utilizing millimeter wave (mmWave) bands. Specifically, it proposes a novel methodology for enhancing the reliability of handovers in 5G networks. Leveraging dual connectivity (DC), the research delineates a procedure allowing user equipment (UE) to maintain concurrent connections with both 4G LTE and 5G mmWave cells, thereby mitigating issues intrinsic to mmWave communications, such as link intermittency due to environmental obstacles.

Key Challenges and Proposed Solutions

Millimeter wave frequencies offer enhanced throughput and massive bandwidth enabling high-speed data transfer necessary for future mobile networks. However, mmWave signals are prone to blockages by common materials and are highly susceptible to directional misalignment, leading to communication outages. The conventional handover mechanisms employed in sub-6 GHz systems are insufficient to address the fast-changing dynamics of mmWave channels—necessitating alternative solutions.

This work provides two distinct contributions to address these challenges:

1. Dual Connectivity Architecture: The authors propose a DC framework that allows for fast switching between mmWave and LTE links without experiencing full handover latency. This leverages an uplink-based measurement framework that dynamically tracks the quality of multiple communication paths, facilitating swift handover or switch decisions.
2. Secondary Cell Handover (SCH) and Dynamic Time-to-Trigger (TTT): By implementing a localized PDCP layer, the framework reduces latency associated with path switching and enhances beam alignment precision. The introduction of a dynamic TTT for SCH encounters enables more timely decisions regarding handover initiation in rapidly changing channel conditions.

Simulation and Evaluation

An intricate ns-3-based simulation framework is utilized to evaluate the proposed system against a baseline conventional handover scheme across various performance metrics. The paper reflects that dual connectivity drastically improves network robustness in several aspects:

• Reduced Latency: DC mechanisms considerably lower switching delay compared to the traditional standalone hard handover, thus minimizing service interruption.
• Increased Throughput and Stability: Maintaining simultaneous connections allows prompt rectification of link failures, enhancing throughput consistency and reducing packet loss.
• Efficient Handover Management: Fast switching capabilities and dynamic beam tracking enable more precise and frequent handover decisions, maintaining an optimal communication link state.

Implications and Future Prospects

The implications of this research are multifold. From a practical standpoint, it outlines a path towards realizing reliable mmWave communication in urban landscapes, addressing critical barriers to deployment. Theoretically, it broadens understanding of multi-connectivity in heterogeneous networks, paving the way for scalable and flexible network architecture adaptations across diverse spatial environments.

Looking forward, further investigation could leverage machine learning techniques to predict channel obstructions and optimize handover timings dynamically. Additionally, extending the dual connectivity approach to integrate seamlessly with other emerging technologies, such as device-to-device communication and network slicing, could significantly bolster the versatility and efficiency of future 5G networks.

In summary, the paper provides an exhaustive examination of the mmWave handover challenges while presenting tangible solutions that significantly enhance mobility management in next-generation mobile networks.