Hybrid Coupler MIMO Signal Cross-Coupling in Distributed Antenna Systems
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Solution Overview
Problem
Current distributed antenna systems (DAS) cannot effectively utilize Multiple-Input/Multiple-Output (MIMO) technology, leading to signal degradation and bandwidth constraints due to the lack of multi-element antennas and simultaneous communication from multiple remote units, which results in performance impairments and limited coverage redundancy.
Innovation Solution
The integration of a hybrid coupler, specifically a 90° 3dB hybrid coupler, between MIMO base stations and master units, allows for the cross-coupling and phase-shifting of MIMO signals to all remote units, enabling simultaneous transmission of MIMO and SISO signals, thereby enhancing coverage and equalizing received power levels, and supporting dynamic switching between SISO and MIMO modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional SISO base stations are used in distributed antenna systems, then system simplicity and ease of operation are maintained, but MIMO capability and system capacity are lost
Solution Approach 1:
The distributed antenna system is designed to support both SISO and MIMO operating modes through the same infrastructure. The system can dynamically adapt between single-input single-output and multiple-input multiple-output configurations, allowing one system to serve multiple functions and different operational requirements without requiring separate dedicated systems for each mode.
Solution Approach 2:
The system enables dynamic switching between SISO and MIMO modes based on operational needs. The distributed antenna units can be configured to transmit either single or multiple spatial streams, and the system can adapt the number of active remote units and signal configurations in real-time to optimize performance for different service conditions and traffic loads.
2Productivity
If only one remote unit communicates with a wireless device, then signal interference and collisions are avoided, but data bandwidth and communication capacity are constrained
Solution Approach 1:
The system segments the communication function across multiple distributed remote units, each capable of independent signal transmission. Instead of relying on a single remote unit, the system divides the communication task among multiple spatially distributed units, allowing parallel data streams to be transmitted simultaneously through different remote units to the same wireless device, thereby increasing overall capacity while maintaining signal quality through spatial diversity.
3Reliability
If multiple remote units transmit simultaneous MIMO signals, then system capacity and coverage redundancy are improved, but signal power imbalance and the 'near-far problem' occur
Solution Approach 1:
The system dynamically adjusts signal parameters including power levels, amplitude, and phase for each remote unit based on its distance from the wireless device and channel conditions. By changing these parameters adaptively, the system compensates for the near-far effect where closer units would otherwise dominate the signal, ensuring that all contributing remote units provide balanced signal contributions to achieve optimal combining performance and maintain proper power levels at the receiver.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution addresses the 'near-far problem' by ensuring balanced received power levels and enabling MIMO operation within existing SISO infrastructure, improving data throughput and system reliability by equalizing performance between parallel data streams and supporting advanced wireless standards like LTE and WiMAX.
Implementation Method 1
The integration of a hybrid coupler, specifically a 90° 3dB hybrid coupler, between MIMO base stations and master units, allows for the cross-coupling and phase-shifting of MIMO signals to all remote units
Data Source
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Figure 2B
AI summary
A distributed antenna system (DAS) 40 includes a multiple-input and multiple- output ("MIMO") base station configured 58 to output at least a first 62 and second signal 64, and a hybrid coupler 52, 58 coupled thereto, the coupler 52, 58 configured to receive the first 62 and second signal 64 from the MIMO base station 58 on respective first and second ports and provide an output signal 68, 70 on at least one output port, the output signal 68, 70 including at least a portion of the first signal 62 and at least a portion of the second signal 64. The DAS 40 further includes a master unit 46 communicating with the coupler 52, 58 and configured to receive at least the output signal 68, 72, and at least one remote unit 42 communicating with the master unit 46 and configured to communicate the output signal 68, 72 to a device.