Random Access Diversity via Phase Rotation
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Solution Overview
Problem
Current wireless communication techniques face challenges in achieving reliable random access channel (RACH) performance, particularly in link-budget challenging environments like cell edges, due to phase misalignment and excessive delay in cyclic delay diversity (CDD) methods, which can compromise timing determination accuracy.
Innovation Solution
The use of transmit diversity schemes with relative phase rotation between signals from multiple antennas, allowing for constructive or destructive interference to align phase states and improve diversity performance without compromising timing accuracy, by retransmitting random access messages with different relative phase states if initial transmissions fail.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cyclic delay diversity (CDD) methods are used to improve RACH diversity performance, then reliability is improved, but timing determination accuracy deteriorates due to excessive delay
Solution Approach 1:
The patent changes the fundamental parameter of phase manipulation from time-domain delay (CDD) to frequency-domain phase rotation. By applying different phase rotations to signals from different antennas in the frequency domain, the system achieves diversity without introducing excessive delay that would compromise timing accuracy. This parameter change resolves the contradiction by decoupling diversity gain from timing error.
2Reliability
If phase rotation is applied to align phase states from multiple antennas, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent substitutes complex mechanical/time-based phase alignment mechanisms with simpler frequency-domain phase rotation operations. Instead of using complex time-domain signal processing or hardware-based phase shifters, the invention applies straightforward complex multiplication in the frequency domain, significantly reducing computational complexity while maintaining diversity benefits.
3Reliability
If retransmission with different phase states is implemented, then reliability is improved, but loss of time increases
Solution Approach 1:
The patent introduces dynamic phase rotation selection for retransmissions. Instead of static phase configurations, the system dynamically changes phase rotation values across retransmission attempts, adapting to channel conditions and improving the probability of successful access while managing time loss through intelligent phase diversity rather than brute-force retransmission.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances RACH diversity performance and reliability, ensuring successful network access and handover without disrupting ongoing communications, even in challenging environments, by aligning phase states and optimizing interference patterns.
Implementation Method 1
The UE transmits signals from a plurality of the M antennas with an initial relative phase state among the signals transmitted by the antennas... The relative phase state for transmission using more than one antenna encompasses relative phase rotation among the two or more transmitting antennas
Implementation Method 2
allowing for constructive or destructive interference to align phase states and improve diversity performance
Data Source
AI summary
Methods, systems, and devices for wireless communication are described. For a user equipment with a number of M greater than or equal to two antennas, a signal is transmitted from at least a first antenna and a second antenna at a first time with an initial relative phase state including a first relative phase rotation between the signals transmitted by the first and second antennas. In response to a determination that a response signal was not received at the user equipment, the signal is retransmitted from at least the first antenna and the second antenna with a subsequent relative phase state among the transmitting antennas, including a second different relative phase rotation, at a second time. The second time may be the next subsequent retransmission of the signal or may be a retransmission following one or more retransmissions using the first relative phase rotation.