Spatial Diversity Scheme for mmWave Beamforming Reliability
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Solution Overview
Problem
Millimeter Wave (mmWave) beamforming systems face reliability and performance issues due to unreliable TX/RX paths, random radio link failure, and service interruptions, particularly in mobility scenarios, as they rely heavily on directional transmissions and are vulnerable to channel characteristics and beamforming challenges in small cells.
Innovation Solution
A spatial diversity scheme is proposed that uses multiple different beams for data and control communication, allowing for duplicate or incremental transmission and reception, enhancing mobility robustness and critical data delivery without retransmission, by combining physical-layer resources with other protocol layer resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If directional beamforming transmissions are used in mmWave systems, then data rate and beamforming gain are improved, but reliability and coverage are degraded due to vulnerable TX/RX paths and intermittent links
Solution Approach 1:
The transmission path is segmented into multiple beam segments (first beam from source to intermediate point, second beam from intermediate point to destination). Each beam segment is independently established and maintained, allowing the system to achieve high directional gain in each segment while providing alternative paths if one segment fails, thus resolving the contradiction between directional beamforming gain and link reliability.
2Reliability
If multiple beams and beam switching are implemented, then spatial diversity and coverage are improved, but system complexity and decision-making complexity increase
Solution Approach 1:
An intermediate communication device is introduced as a mediator that receives data from the source device via a first beam and forwards it to the target device via a second beam. This intermediary simplifies the beam management complexity by breaking down the complex multi-beam switching problem into simpler point-to-point beam connections, while still providing spatial diversity through multiple beam paths.
3Reliability
If handover is performed too late or too early, then connection failure occurs, but handover timing optimization increases system complexity
Solution Approach 1:
The system establishes a relay connection through an intermediate device before the direct link fails, performing preliminary action to maintain connectivity. By pre-configuring alternative beam paths through intermediaries, the system avoids the complexity of real-time handover timing decisions while ensuring connection reliability, as the alternative path is already in place when needed.
Data Source
AI summary
A method of providing spatial diversity for critical data delivery in a beamformed mmWave smallcell is proposed. The proposed spatial diversity scheme offers duplicate or incremental data/signal transmission and reception by using multiple different beams for the same source and destination. The proposed spatial diversity scheme can be combined with other diversity schemes in time, frequency, and code, etc. for the same purpose. In addition, the proposed spatial diversity scheme combines the physical-layer resources associated with the beams with other resources of the same or different protocol layers. By spatial signaling repetition to avoid Radio Link Failure (RLF) and Handover Failure (HOF), mobility robustness can be enhanced. Mission-critical and/or time-critical data delivery can also be achieved without relying on retransmission.