Fast Fallback Mechanism for mmWave Link Recovery
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Solution Overview
Problem
Millimeter wave (mmWave) wireless access systems face challenges in maintaining efficient data communication and fast link recovery due to Line of Sight (LoS) to Non-Line of Sight (NLoS) transitions, leading to potential link failures and increased fallback times compared to legacy systems.
Innovation Solution
A method and apparatus for performing fast fallback in mmWave systems by establishing RRC connections with both mmWave and legacy base stations, detecting NLoS transitions, and transmitting fallback requests to legacy stations, including resource allocation information and security keys, to ensure continuous data transmission and rapid link recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If fast fallback is performed before link failure in mmWave systems, then link recovery time is reduced, but system complexity increases due to dual RRC connection management
Solution Approach 1:
The patent establishes RRC connections with both mmWave and legacy base stations before link failure occurs. The legacy RRC connection is maintained in a dormant state, ready for immediate activation. This preliminary setup allows the UE to switch to the legacy connection instantly when mmWave link degradation is detected, achieving fast fallback without going through connection establishment procedures.
Solution Approach 2:
The legacy base station serves multiple functions: it maintains a dormant RRC connection for potential fast fallback, provides resource allocation information in advance, and acts as a backup communication path. This multi-functionality allows the system to reduce link recovery time while managing complexity through the legacy BS's versatile role.
2Speed
If resource allocation information is pre-configured for fast fallback, then fallback execution speed is improved, but signaling overhead increases
Solution Approach 1:
The legacy base station pre-configures and transmits resource allocation information to the UE before fast fallback is needed. This includes allocating uplink resources for fallback indication messages and configuring parameters in advance. When fallback is triggered, the UE can immediately use these pre-allocated resources without waiting for resource allocation procedures, thus improving execution speed while minimizing additional signaling.
3Reliability
If dual RRC connections are maintained with mmWave and legacy BS, then link reliability is improved, but power consumption increases
Solution Approach 1:
The patent implements dynamic management of dual RRC connections where the legacy connection is maintained in a dormant state with minimal power consumption. The UE can quickly activate this dormant connection when needed for fast fallback, rather than maintaining both connections at full active state. This dynamic approach improves link reliability while controlling power consumption through selective activation.
Solution Approach 2:
Different quality states are applied to different connections: the mmWave connection is maintained in an active state for high-performance data transmission, while the legacy connection is kept in a dormant state with minimal resource allocation. This local quality differentiation allows the system to have reliable fallback capability without the power consumption penalty of maintaining both connections at full activity.
Data Source
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AI summary
The present invention relates to a wireless access system supporting a millimeter wave (mmWave), and provides methods for performing a fast fallback in order to avoid a link disconnection and devices supporting the same. As an embodiment of the present invention, a method for performing a fast fallback by a terminal in a wireless access system supporting a millimeter wave (mmWave) may comprise the steps of: establishing radio resource control (RRC) connections with a mmWave base station and a legacy base station, respectively; receiving downlink data transmitted from the mmWave base station; receiving, from the legacy base station, resource-related information associated with a resource to be allocated for a fast fallback; detecting whether a non-light of sight (NLoS) transition occurs in a mmWave link with the mmWave base station; and when the NLoS transition occurs, transmitting a fallback request message to the legacy base station in order to perform the fast fallback.