Open-Loop MIMO Phase-Shifting for Broadcast Diversity
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Solution Overview
Problem
Existing radio communication systems, particularly cellular networks, face challenges in optimizing Point to Multi-Point (PTMP) communication services due to non-ideal communication channel conditions, which are not well addressed by current closed-loop feedback schemes, limiting throughput and diversity in broadcast services.
Innovation Solution
The implementation of an open-loop MIMO communication system that phase-shifts data symbols to create multiple streams, which are then broadcast across multiple cells without requiring closed-loop feedback, using phase-shifting and interleaving techniques to enhance diversity and improve data reception across different mobile stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If closed-loop feedback schemes are used to optimize communication, then communication reliability can be improved through adaptive modulation and coding, but the system complexity increases and the scheme becomes less amenable to broadcast services
Solution Approach 1:
The patent extracts the feedback mechanism from the communication system, transitioning from closed-loop to open-loop operation. By removing the feedback path, the system eliminates the complexity of adaptive modulation and coding while maintaining broadcast capability. The diversity gain is achieved through transmitter-side processing rather than receiver feedback.
Solution Approach 2:
The patent segments the communication approach by separating the diversity creation function from the feedback loop. Instead of using feedback to adapt the entire communication scheme, the patent segments the problem into: (1) fixed modulation and coding, and (2) diversity introduction through phase-shifting and interleaving at the transmitter.
2Reliability
If conservative modulation and coding schemes are selected to ensure best communication to mobile stations, then communication reliability is improved, but throughput rates are limited
Solution Approach 1:
The patent applies preliminary action by pre-processing the data through phase-shifting and interleaving before transmission. This preliminary diversity creation allows the system to use higher-order modulation and coding schemes without requiring feedback-based adaptation, thereby achieving both high throughput and reliability through predetermined diversity mechanisms.
Solution Approach 2:
The patent changes the parameter of signal diversity through phase-shifting operations. By modifying the phase parameters of transmitted signals across multiple antennas or time slots, the system creates diversity without changing the modulation and coding parameters, enabling higher throughput while maintaining reliability.
3Reliability
If phase-shifting is applied to create multiple data streams for diversity, then diversity gain is improved, but the device complexity increases
Solution Approach 1:
The patent uses copying by creating multiple copies of the same data stream with different phase shifts. Instead of processing entirely different data through complex algorithms, the system copies the input data and applies simple phase-shift operations, achieving diversity gain with minimal processing complexity.
4Reliability
If multiple base stations broadcast the same data with phase-shifting to increase diversity, then coverage and reliability are improved, but the system complexity and coordination requirements increase
Solution Approach 1:
The patent applies local quality by allowing each base station to independently apply phase-shifting and interleaving to the broadcast data without requiring network-wide coordination. Each base station processes the data locally with the same algorithm, achieving network-wide diversity through identical local operations rather than complex inter-station coordination.
Data Source
AI summary
Apparatus, and an associated method, for providing transmit diversity to an open-loop MIMO communication scheme, such as a point to multipoint broadcast service in a cellular system. Multiple data streams of the broadcast data are broadcast by way of transmit diversity antennas of a sending station. The data symbols of the separate data streams are phase-shifted to be offset in phase from one another. The data streams, once the data symbols thereof are selectably phase-shifted by a phase shifter, are applied by an applier to sending nodes of the respective cells.