MIMO Receiver Interference Cancellation Using STC Signal Rearrangement
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Solution Overview
Problem
In Broadband Wireless Access (BWA) communication systems using Multiple Input Multiple Output (MIMO) technique, interference from neighboring cells degrades channel estimation and data recovery performance, especially for mobile stations at the edge of serving cells, due to larger channel matrices and mixed signals in the same subcarrier.
Innovation Solution
The implementation of a Space-Time Coding (STC) mode to increase signal dimensions by measuring channel correlations on the time/frequency axis, determining suitable block sizes, rearranging received signals, performing cross-correlation and auto-correlation, and calculating estimate weights for interpolation to detect and combine desired signals, thereby canceling interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If inter-cell frequency reuse factor of 1 is used to enhance frequency efficiency, then frequency efficiency is improved, but interference from neighboring cells increases
Solution Approach 1:
The patent converts the harmful interference from neighboring cells into a beneficial signal by applying interference cancellation techniques. The received signal model explicitly includes both desired signal and interference signal components, and the channel estimation process is designed to separate and cancel the interference, thereby transforming the harmful frequency reuse into a manageable parameter that can be compensated for through signal processing.
Solution Approach 2:
The patent introduces pilot signals as an intermediary element to facilitate channel estimation in the presence of interference. These known pilot signals serve as reference points that allow the receiver to estimate the channel response and distinguish between desired and interfering signals, acting as a mediator between the mixed received signals and the channel state information.
2Device complexity
If conventional channel estimation is used in MIMO systems, then system complexity is kept low, but channel estimation accuracy degrades due to interference
Solution Approach 1:
The patent segments the channel estimation process into distinct stages: interference signal modeling, pilot-based channel estimation, and data signal detection. By dividing the received signal into desired signal and interference signal components, and estimating channels separately for each, the method achieves improved accuracy without requiring excessively complex unified processing.
Solution Approach 2:
The patent exploits the spatial dimension introduced by MIMO multiple antennas to separate desired and interfering signals. By utilizing the different spatial channels provided by multiple transmit and receive antennas, the system can distinguish and estimate channels for signals arriving from different directions, thereby improving estimation accuracy through dimensional expansion.
3Object-generated harmful factors
If pilots are transmitted through antennas alternately in MIMO, then inter-antenna interference is avoided, but interference from neighboring cells still degrades performance
Solution Approach 1:
The patent converts the harmful neighboring cell interference into a characterizable signal component by developing an explicit interference signal model. This model allows the receiver to estimate interference channels and cancel the interference, transforming the harmful effect into a manageable parameter that can be compensated for through signal processing.
Solution Approach 2:
The patent performs preliminary interference cancellation by estimating and removing the interference signal component before final channel estimation and data detection. This preliminary action of subtracting the estimated interference from the received signal cleans up the signal environment, making subsequent channel estimation more accurate.
Data Source
AI summary
Provided are an apparatus and method for interference cancellation in a BWA communication system. In a receiving apparatus for the interference cancellation, a preamble correlation measurer measures a preamble correlation coefficient from a preamble of a signal received signal. A data rearranger determines a block size to divide the received signal from the preamble correlation coefficient, divides the signal according to the determined block size, and rearranges the divided signals in a Space-Time coding (STC) mode. An estimate weight calculator cross-correlates the output signals of the data rearranger, rearranges the cross-correlated signals, auto-correlates the rearranged signals, and calculates an estimate weight to perform an interpolation operation. An estimate signal decoding/combining unit detects desired signals from signals estimated by the estimate weight calculator and combines the detected signals.