Differential Spatial Multiplexing MIMO Signal Transmission
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Solution Overview
Problem
Conventional MIMO mobile communication systems face limitations in symbol transmission rates and modulation schemes, especially in fast fading channel environments, where CSI estimation is necessary, leading to performance losses and restricted modulation options.
Innovation Solution
A differential Spatial Multiplexing (SM) scheme is employed in a MIMO mobile communication system, which generates unitary space-time matrices using a Gram-Schmidt scheme, allowing for unrestricted symbol transmission rates and modulation schemes without requiring CSI estimation at the receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a differential space-time block coding scheme is used in a MIMO mobile communication system, then the system can operate in fast fading channel environments without CSI estimation, but the symbol transmission rate is limited to a maximum rate of 1 for real number signals or 3/4 for complex number signals
Solution Approach 1:
The patent changes the fundamental parameter of the coding scheme from differential space-time block coding to differential spatial multiplexing. This parameter change allows the system to achieve both high reliability in fast fading channels and high symbol transmission rates by using multiple independent data streams transmitted through multiple antennas simultaneously, breaking the rate limitation of traditional differential coding schemes
Solution Approach 2:
The patent transitions from a single-stream differential coding approach to a multi-stream spatial multiplexing approach. By adding the spatial dimension with multiple independent data streams transmitted through multiple antennas, the system achieves both reliability and high transmission rates that were mutually exclusive in conventional single-stream differential coding
2Device complexity
If conventional differential space-time block coding is used, then CSI estimation complexity is avoided, but modulation schemes are limited to PSK-based schemes due to average transmit power constraints
Solution Approach 1:
The patent changes the power normalization parameter by applying specific normalization factors to the transmitted signals. This parameter change allows the use of high-order modulation schemes like 16-QAM and 64-QAM in differential spatial multiplexing, removing the restriction to only PSK-based schemes while maintaining the advantage of avoiding CSI estimation complexity
Solution Approach 2:
The patent creates a universal differential spatial multiplexing framework that can accommodate multiple modulation schemes (BPSK, QPSK, 16-QAM, 64-QAM, etc.) within a single system architecture. This multi-functional approach eliminates the need for separate differential coding schemes for different modulation types, providing versatility while maintaining simplicity
3Reliability
If space-time block coding scheme is used, then superior performance is achieved through simple decoding process in slow fading channel environments, but the scheme is not suitable for fast fading channel environments where receiver-side must estimate CSI
Solution Approach 1:
The patent inverts the conventional approach by using differential encoding at the transmitter without requiring CSI estimation at the receiver. Instead of the receiver estimating channel conditions and compensating for fading, the transmitter embeds channel information in the differential encoding process, eliminating the need for complex CSI estimation while maintaining error rate performance in fast fading environments
Data Source
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AI summary
Disclosed is a mobile communication system using a Multiple Input Multiple Output (MIMO) scheme. A transmitter of the mobile communication system, generates a unitary space-time matrix to correspond to a codeword if the codeword to be transmitted in a first time interval is input, multiplies the unitary space-time matrix by a first final transmission matrix denoting signals transmitted in a second time interval before the first time interval, thereby generating a second final transmission matrix denoting signals to be transmitted in the second time interval, and transmits signals corresponding to the second final transmission matrix through a plurality of transmit antennas in the second time interval.