RACH-less Handover for Millimeter Wave Wireless Systems
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Solution Overview
Problem
Millimeter wave (mmW) wireless communication systems face substantial overhead in handover procedures due to reliance on mobility management entities and random access channels (RACH), which increase latency and complexity.
Innovation Solution
Implementing localized, RACH-less handover schemes where user equipment (UE) initiates handovers based on relative location, signal strength, or predetermined times, transmitting handover messages directly to the new base station without using RACH, thereby reducing overhead and latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional handover procedures using RACH are implemented, then connectivity parameters can be determined, but handover latency and overhead increase substantially
Solution Approach 1:
The UE determines connectivity parameters for the target base station in advance, before the actual handover execution. The UE identifies suitable beams and prepares handover configuration information ahead of time, allowing the handover to be executed quickly without waiting for RACH procedures at the moment of handover.
Solution Approach 2:
The patent extracts and eliminates the RACH transmission step from the handover procedure. By using pre-determined connectivity parameters and direct handover messaging between UE and base stations, the RACH-based random access process is completely removed, significantly reducing handover latency and overhead.
2Reliability
If MME facilitates handover procedures, then handover coordination is achieved, but system complexity and overhead increase
Solution Approach 1:
The UE autonomously determines connectivity parameters and initiates handover decisions based on signal measurements and pre-configured criteria. The base stations directly exchange handover configuration information without MME intervention, allowing the handover process to be self-managed by the access network entities themselves.
Solution Approach 2:
The handover procedure is segmented into independent phases: UE autonomous decision-making, direct base station communication for configuration exchange, and execution. This segmentation removes the need for centralized MME coordination, distributing the handover management function across the involved entities.
3Reliability
If RACH transmissions are used for handover, then connectivity parameters are established, but overhead increases substantially
Solution Approach 1:
Connectivity parameters including beam identification and configuration information are determined in advance by the UE before handover execution. This preliminary determination eliminates the need for extensive RACH signaling exchanges during the actual handover, reducing the quantity of signals required.
Solution Approach 2:
The RACH transmission mechanism is completely extracted and removed from the handover procedure. Instead of using RACH for random access and parameter negotiation, the patent employs direct handover messaging that carries all necessary connectivity information, eliminating RACH-related overhead entirely.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A user equipment (UE) may initiate handover from one base station to another. The handover procedure may not include random access channel (RACH) transmissions, and thus may be a localized RACH-less handover. The UE may initiate handover to a new base station based on the relative location of the UE and the new base station, some predetermined time, or based on the characteristics of the signals from each base station.