Adjusting Transmission Phasing in Point-to-Point Communication Links
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional point-to-point radio systems face limitations in maximizing gain due to obstructions within the Fresnel zone, particularly when using a single upper antenna for transmission and a lower receive-only antenna, which results in significant signal loss during unfavorable atmospheric conditions.
Innovation Solution
The system employs spatially diverse antennas for both transmission and reception, using OFDM signals with pilot tones to adjust the relative phases of signals transmitted from multiple antennas, allowing optimal combination at the receiver using a maximum ratio combiner, thereby enhancing system gain and reducing fade margin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single upper antenna is used for transmission and a lower receive-only antenna is used, then the system structure is simple and easy to implement, but signal loss occurs during unfavorable atmospheric conditions due to Fresnel zone obstructions
Solution Approach 1:
The patent combines transmit and receive functions into both upper and lower antennas, creating a full-duplex spatial diversity system. The lower antenna transitions from receive-only to dual functionality, merging transmission and reception capabilities across multiple spatial paths to overcome fading on any single path.
Solution Approach 2:
The patent introduces spatial dimensionality by utilizing both upper and lower antennas for transmission and reception. This vertical spatial separation creates multiple independent propagation paths through the Fresnel zone, adding a dimensional aspect to signal transmission that diversifies against atmospheric fading.
2Reliability
If the lower antenna is used for receive only to provide diversity, then an alternative signal path is available, but the path between lower antennas experiences significant obstructions to the Fresnel zone in normal atmospheric conditions
Solution Approach 1:
The patent merges the lower antenna into active transmission alongside the upper antenna. By transmitting from both upper and lower antennas simultaneously with coordinated phase relationships, the system creates multiple spatially diverse signal paths that combine at the receiver to overcome obstructions affecting any single path.
Solution Approach 2:
The patent changes the operational parameters of the lower antenna from receive-only mode to active transmit and receive mode. This parameter change enables the lower antenna to contribute constructively to the signal through phase-coherent combination, transforming it from a passive diversity element to an active signal source.
3Power
If two antennas are used for both transmission and reception to maximize gain, then system gain is significantly improved and signal loss is reduced, but the system complexity increases due to phase adjustment requirements
Solution Approach 1:
The patent implements feedback mechanisms through pilot tones that enable the receiver to measure channel conditions and communicate phase adjustment requirements back to the transmitter. This feedback loop allows automatic phase coordination between upper and lower antennas, reducing manual configuration complexity while maintaining optimal gain.
Solution Approach 2:
The patent dynamically adjusts phase parameters of the transmitted signals from upper and lower antennas based on measured channel conditions. By changing phase parameters in response to atmospheric conditions and obstruction levels, the system optimizes constructive interference at the receiver while adapting to varying environmental factors.
4Measurement precision
If pilot tones are inserted into the OFDM signal format for phase adjustment, then accurate phase estimation is achieved, but the signal processing complexity increases due to separate FFT transformation and maximum ratio combining
Solution Approach 1:
The patent segments the OFDM signal into data subcarriers and pilot subcarriers with distinct functions. Pilot tones are inserted at specific frequency locations separated from data carriers, allowing independent processing of phase reference information without interfering with data transmission. This segmentation enables precise phase measurement through dedicated pilot processing paths.
Solution Approach 2:
The patent uses pilot tones as intermediary reference signals that mediate between the transmitted signal and the channel characteristics. These pilot tones serve as known reference points that facilitate channel estimation and phase measurement without carrying user data, acting as intermediaries that enable accurate phase tracking through maximum ratio combining at the receiver.
Data Source
AI summary
An apparatus and method for adjusting transmission phasing in a point-to-point communication link is disclosed. The relative phases of the transmissions from each antenna are adjusted before transmission to give optimum gain when received by two or more antenna elements and a signal combining element. The signal includes a data component, consisting of a subset of the subcarriers modulated with the input data, which is common to transmissions from all antenna elements; and a phase reference component consisting of a subset of the subcarriers that are modulated with a predetermined phase. The signal combining element is operable to receive the components and extract phase information. A phase adjustment signaling device compares extracted phase information and signals the plurality of transmitting antenna elements to adjust the relative transmission phasing between the signals transmitted from a plurality of transmitting antenna elements to permit a receiver to receive the transmitted signals with a desired phase relationship.