Physical-Layer Midamble Phase Shifting to Mitigate Spectral Lines
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Solution Overview
Problem
The insertion of midambles in physical layer packets leads to undesired spectral lines in the power spectrum, which complicates the fulfillment of spectrum masks and frequency requirements.
Innovation Solution
Applying a sequence of random or pseudo-random phase shifts to each midamble of the physical layer packet, which are then counteracted at the receiver, mitigates the spectral lines by randomizing the midamble symbols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If midambles are inserted in physical layer packets to support channel estimation in varying channels, then channel estimation accuracy is improved, but spectral lines appear in the power spectrum complicating fulfillment of spectrum masks
Solution Approach 1:
The patent applies random or pseudo-random phase shifts to midamble symbols, changing the phase parameter of the midamble sequence. This transforms the deterministic spectral lines into randomized spectral distributions, allowing the signal to meet spectrum mask requirements while preserving channel estimation functionality.
Solution Approach 2:
The patent introduces dynamic phase shifting where the phase shift applied to each midamble varies according to a random or pseudo-random sequence. This dynamic modification prevents the formation of fixed spectral lines while maintaining the midamble's channel estimation capability across different transmission instances.
2Object-generated harmful factors
If conventional transmission filters are used to meet spectrum requirements with midambles, then spectrum mask compliance is achieved, but transmission filter requirements become stringent and complex
Solution Approach 1:
The patent applies phase shifts to midambles before transmission as a preliminary action. This pre-processing step randomizes the spectral characteristics of midambles in advance, reducing the burden on subsequent transmission filters and allowing for simpler, less stringent filter designs while still meeting spectrum mask requirements.
3Power
If output power is increased to improve transmission performance, then signal strength is improved, but interference with other users increases
Solution Approach 1:
By randomizing the phase of midamble symbols, the patent transforms concentrated spectral lines into dispersed spectral energy. This allows the system to transmit at higher output power levels because the interferential energy is distributed across the spectrum rather than concentrated at specific frequencies, thereby reducing peak interference with other users while maintaining overall signal strength.
Data Source
AI summary
A method is disclosed of a transmitter configured to transmit a physical layer packet having a plurality of midambles. The method comprises applying a respective phase shift for each midamble of the physical layer packet, and transmitting the physical layer packet. The respective phase shift is applied to at least a portion of symbols of the midamble.A method is also disclosed of a receiver configured to receive a physical layer packet having a plurality of midambles. The method comprises receiving the physical layer packet, and counteracting a respective phase shift for each midamble of the physical layer packet. Counteracting the respective phase shift comprises applying an opposite of the respective phase shift to at least a portion of symbols of the midamble or compensating the respective phase shift for at least a portion of symbols of the midamble.