Q-R Decomposition for Interference Cancellation in MIMO Systems
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Solution Overview
Problem
In mobile communication systems, the fading phenomenon causes distortion in signal amplitude and phase, leading to interference between orthogonal coded signals transmitted via multiple antennas, which deteriorates reception quality and makes it challenging to apply reception diversity schemes effectively, especially in downlink environments where terminal size constraints limit antenna spacing.
Innovation Solution
An apparatus and method that include a receiving unit, channel estimation unit, Q-R decomposition unit, and signal determination unit to generate a received vector, estimate channel state, perform Q-R decomposition, and determine a signal with decreased interference from orthogonal coded signals, using a transmitter with multiple antennas to cancel interferences by generating a decision statistic vector and subtracting interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If orthogonal coded signals are transmitted via multiple antennas to increase data transmission capacity, then the served amount of data increases, but interference between signals occurs due to fading phenomenon, deteriorating reception quality
Solution Approach 1:
The patent extracts and removes the interference component from the received signal through interference cancellation processing. The receiving apparatus separates the desired signal from the interfering signals transmitted by multiple antennas, effectively taking out the harmful interference to improve reception quality while maintaining high data transmission capacity
Solution Approach 2:
The patent changes the processing parameters by applying Q-R decomposition to the channel state information and adjusting the reception processing based on the decomposition results. This parameter transformation enables the system to maintain signal orthogonality and cancel interference, resolving the contradiction between high data capacity and reception quality
2Reliability
If reception diversity scheme is applied to overcome fading phenomenon, then signal reception reliability improves, but terminal size constraints limit antenna spacing, making it difficult to apply in downlink
Solution Approach 1:
Instead of applying reception diversity at the terminal (which is constrained by size), the patent inverts the approach by implementing transmission diversity at the base station with multiple antennas. The receiving apparatus then processes the transmitted diversity signals through interference cancellation, achieving diversity gain without requiring large terminal antenna arrays
Solution Approach 2:
The patent introduces channel state information and Q-R decomposition as intermediary processing elements. These intermediaries enable the receiving apparatus to process multiple transmitted signals effectively, achieving diversity reception without requiring physically spaced antennas at the terminal
3Productivity
If multiple data streams are transmitted using orthogonal coding, then transmission efficiency increases, but orthogonality between signals is lost due to fading, causing interference
Solution Approach 1:
The patent employs feedback by using channel state information obtained from the wireless channel to adjust the reception processing. The receiving apparatus continuously monitors the channel conditions and uses this feedback to perform Q-R decomposition and interference cancellation, maintaining signal orthogonality despite fading effects and ensuring stable multi-stream transmission
Data Source
AI summary
Apparatuses and methods for cancelling interferences between signals are provided. The apparatuses includes: a receiving unit that receives an orthogonal coded signal from a transmitter and generates a received vector; a channel estimation unit that estimates a state of a wireless channel from the transmitter to the apparatus where the cancelling of the interference between signals is performed and generates a channel state matrix; a Q-R decomposition unit that performs Q-R decomposition with respect to the generated channel state matrix and generates a Q matrix and an R matrix, and generates a decision statistic vector based on the generated Q matrix and the received vector; and a signal determination unit that determines a received signal with interference from the orthogonal coded signal being decreased based on the generated decision statistics vector.