Carrier Aggregation Receiver Chains for Interference-Limited OFDM
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current OFDM/OFDMA-based communication systems face challenges in maximizing system capacity while minimizing noise and interference, particularly in non-ideal channels, where existing receiver and transmitter techniques are insufficient to effectively handle Inter-Symbol Interference (ISI), Adjacent Channel Interference (ACI), and Cross Polarization Interference (CPI).
Innovation Solution
The method involves transforming data vectors using Fourier transforms or Butler matrices, inserting pilot symbols, and transmitting these transformed vectors across multiple sub-carriers, allowing for channel estimation and signal processing to mitigate interference, and using spatial matched filters and rake receivers to optimize signal reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OFDM/OFDMA-based communication systems use conventional transmitter and receiver techniques, then system implementation is straightforward, but system capacity cannot be maximized and interference (ISI, ACI, CPI) cannot be effectively minimized in non-ideal channels
Solution Approach 1:
The communication system is divided into multiple independent carriers (sub-carriers) that can be processed separately. Each carrier handles a portion of the data stream, allowing parallel processing and reducing the complexity of handling the entire signal at once. This segmentation enables the system to achieve higher capacity through carrier aggregation while keeping individual receiver processing manageable.
Solution Approach 2:
The patent introduces spatial dimension processing through multiple antennas and spatial matched filters. By adding the spatial dimension to the traditional frequency-domain OFDM processing, the system can separate and mitigate interference from different spatial directions, thereby reducing ACI and CPI while maximizing system capacity through spatial diversity.
2Reliability
If conventional receiver techniques are used, then receiver implementation is simple, but Inter-Symbol Interference (ISI), Adjacent Channel Interference (ACI), and Cross Polarization Interference (CPI) cannot be effectively handled
Solution Approach 1:
Pilot symbols are introduced as intermediary reference signals that facilitate channel estimation and interference characterization. These pilot symbols serve as mediators between the transmitted signal and the received signal, enabling the receiver to accurately estimate channel conditions and compensate for ISI, ACI, and CPI without requiring complex blind detection algorithms.
Solution Approach 2:
The patent replaces traditional time-domain equalization methods with frequency-domain processing and spatial filtering techniques. By transforming the equalization problem from the time domain to the frequency domain through FFT operations, and by using spatial matched filters instead of complex adaptive equalizers, the system achieves better interference mitigation with reduced computational complexity.
3Productivity
If bandwidth is increased to improve capacity, then communication capacity increases, but noise and interference levels also increase
Solution Approach 1:
The wide bandwidth is segmented into multiple narrower sub-carriers, each experiencing less noise and interference. By processing data across multiple segmented frequency channels rather than a single wide channel, the system achieves high aggregate capacity while each individual sub-carrier operates at lower noise levels, improving overall signal quality.
Solution Approach 2:
Multiple carriers with individually lower noise and interference levels are merged through coherent combining at the receiver. The spatial matched filters and rake receivers combine signals from multiple carriers and spatial paths, achieving signal addition while noise and interference average out, thereby improving the signal-to-noise ratio while maintaining high capacity.
Data Source
AI summary
Various embodiments of carrier aggregation are provided that increase communications capacity and throughput. According to some embodiments, a receiver may be configured with a plurality of receiver chains and, responsive to an aggregate bandwidth of an overall signal that is to be received by the receiver, a plurality of components of the overall signal, each comprising a bandwidth that is less than a frequency span of the overall signal, are received by a respective plurality of receiver chains. Accordingly, each component of the plurality of components of the overall signal may be received by a respective receiver chain of the plurality of receiver chains of the receiver thus avoiding bandwidth limitations associated with receiver elements.