Radio Head Feed-Forward Clock Sync for Phase-Aligned Transmission
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Solution Overview
Problem
Distributed radio systems face challenges in achieving time- and phase-aligned signals across multiple radio heads due to inherent frequency offsets, leading to significant phase drift and signal degradation, particularly in millimeter-wave communication systems, which existing solutions like crystal oscillators and synthesizer corrections are inadequate.
Innovation Solution
Implementing a feed-forward correction method using Digital-to-Time Converter (DTC) phase-correction and base-band phase-correction to align phase without altering the local reference sources or synthesizers, specifically through Digital Transmitter (DTx) and Base-Band (BB) phase-correction techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If distributed radio systems use multiple independent frequency sources in each radio head, then flexibility in RF interface placement and millimeter-wave communication are enabled, but phase drift and signal misalignment occur due to inherent frequency offsets
Solution Approach 1:
The patent implements a feedback mechanism where the base band subsystem continuously monitors phase differences between multiple radio heads and dynamically generates phase correction signals. These correction signals are fed back to the affected radio heads to compensate for phase drift in real-time, thereby maintaining reliable phase alignment while preserving the flexibility of distributed architecture
Solution Approach 2:
The base band subsystem acts as an intermediary that coordinates between multiple independent radio heads. It receives frequency offset information from each radio head, processes this information to determine appropriate phase corrections, and distributes correction signals back to the radio heads, thereby mediating the phase alignment issue without requiring direct modification of the radio heads' independent frequency sources
2Reliability
If existing solutions like crystal oscillators and synthesizer corrections are used, then frequency stability is improved, but they are inadequate for preventing significant phase drift in millimeter-wave communication systems
Solution Approach 1:
The patent replaces traditional mechanical/electronic phase correction methods (crystal oscillators, synthesizer corrections) with a digital signal processing approach. The base band subsystem uses digital algorithms to calculate and apply phase correction signals, providing superior phase alignment accuracy specifically tailored for millimeter-wave communication requirements where traditional methods prove inadequate
3Reliability
If phase correction is applied by altering local reference sources or synthesizers, then phase alignment is achieved, but the integrity of original frequency sources is compromised
Solution Approach 1:
The patent segments the phase correction function into a separate base band subsystem rather than modifying the radio heads' reference sources directly. This separation allows phase correction to be applied independently through digital signal processing in the base band domain, achieving phase alignment while preserving the stability and integrity of the original frequency sources in each radio head
Data Source
AI summary
A radio-head apparatus can comprise synchronization circuitry to receive transmission data and a phase correction signal. The synchronization circuitry can process the transmission data and the phase correction signal to generate digital transmitter (DTX) codes. The radio-head can further include transmission circuitry to combine the phase correction signal with transmission data codes to be provided to the DTX for transmission over an air interface. Other systems and apparatuses are described.