Mixed Space Time Frequency Block Coding for LTE Resource Utilization
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Solution Overview
Problem
In LTE systems, semi-open-loop transmission with SFBC for high mobility UEs results in inefficient resource utilization due to 'orphan' resource elements, leading to wasted resources and restricted precoding flexibility, especially when CSI-RS or DMRS ports are configured.
Innovation Solution
Implementing a mixed space time and space frequency block coding method, where precoded modulation symbols are mapped to resource elements in a frequency-first manner in one subset of OFDM symbols and a time-first manner in another subset, ensuring no resource elements are unused and allowing flexible precoding across resource blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SFBC is used for semi-open-loop transmission in LTE, then transmission robustness for high mobility UEs is improved, but resource element utilization efficiency deteriorates due to orphan resource elements
Solution Approach 1:
The patent dynamically switches between SFBC and STBC coding schemes based on whether CSI-RS or DMRS ports are configured. When CSI-RS/DMRS ports are configured, STBC is used to eliminate orphan resource elements; when not configured, SFBC is used for robust transmission. This dynamic adaptation resolves the contradiction between transmission robustness and resource utilization efficiency.
Solution Approach 2:
The patent changes the block coding parameter (from SFBC to STBC) based on the configuration of reference signal ports. This parameter change allows the system to adapt to different resource element patterns, ensuring that all resource elements are utilized efficiently while maintaining transmission robustness for high mobility UEs.
2Reliability
If SFBC is used with CSI-RS or DMRS ports configured, then transmission diversity is provided, but precoding flexibility is restricted due to orphan resource elements
Solution Approach 1:
The patent introduces dynamic switching between SFBC and STBC based on reference signal configuration. When CSI-RS/DMRS ports are configured, STBC is applied which allows flexible precoding across all resource elements without the orphan element constraint, thus maintaining both transmission diversity and precoding flexibility.
Solution Approach 2:
By changing the block coding scheme parameter from SFBC to STBC when reference signals are configured, the patent enables flexible precoding while maintaining transmission diversity. The parameter change adapts the system to the resource element pattern created by CSI-RS/DMRS ports.
3Ease of operation
If frequency-first mapping is used in all OFDM symbols, then resource element allocation is simplified, but transmission efficiency deteriorates due to unused orphan resource elements
Solution Approach 1:
The patent segments the OFDM symbols into two groups: those containing CSI-RS/DMRS ports and those that do not. For the first group, time-first mapping (STBC) is used to eliminate orphan elements; for the second group, frequency-first mapping (SFBC) is used for simplicity. This segmentation resolves the contradiction between allocation simplicity and transmission efficiency.
Solution Approach 2:
The patent applies different mapping strategies (frequency-first vs. time-first) to different local regions (groups of OFDM symbols) based on their reference signal configuration. This local quality approach ensures that each region uses the most appropriate mapping method, maximizing overall transmission efficiency while maintaining simplicity where applicable.
Data Source
AI summary
Systems and methods for mixed space time and space frequency block coding are provided. In some embodiments, a method of operating a first node in a wireless communication network for providing time and frequency diversity includes precoding modulation symbols intended for a second node according to two antenna ports on which they are to be transmitted. In a first subset of Orthogonal Frequency-Division Multiplexing (OFDM) symbols, mapping the precoded modulation symbols to resource elements starting first with indices corresponds to frequency. In a different subset of OFDM symbols, mapping the precoded modulation symbols to resource elements in any two adjacent OFDM symbols starting first with indices corresponds to time. In this way, transmission efficiency may be increased by not having any resource elements unused. Additional flexibility for precoding may also be provided when there is no symbol pair mapped to resource elements across two resource blocks.