Reference Symbol Structure for Multi-Antenna Transmission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In OFDM-based communication systems, especially in LTE, there is a need to transmit both common and user-specific reference symbols to support closed-loop multi-antenna transmission technologies like beam-shaping, which requires a structured approach to integrate these symbols effectively into the downlink subframe.
Innovation Solution
A method and system that configure and transmit both common and user-specific reference symbols within the downlink subframe based on the number of deployed antennae, using a uniform reference symbol structure, with the transmitting end inserting these symbols and providing indication information for the receiving end to obtain them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If only common reference symbols are transmitted in the downlink subframe, then the system structure is simple and easy to implement, but closed-loop multi-antenna transmission technologies like beam-shaping cannot be supported
Solution Approach 1:
The reference symbols are segmented into two distinct types: common reference symbols (CRS) and user-specific reference symbols (UE-RS). CRS are transmitted on all resource blocks for general channel estimation, while UE-RS are transmitted only on resource blocks allocated to specific users for beam-shaping and closed-loop multi-antenna transmission. This segmentation allows the system to support advanced antenna technologies without requiring complete restructuring of the reference symbol framework.
Solution Approach 2:
User-specific reference symbols are introduced in the time domain by allocating them to specific OFDM symbols within the subframe structure. The UE-RS are positioned in the 4th and 11th OFDM symbols of each slot, creating a temporal dimension for reference symbol transmission that complements the frequency-domain resource block allocation. This dimensional approach enables support for beam-shaping without conflicting with common reference symbol transmission.
2Adaptability or versatility
If both common and user-specific reference symbols are transmitted, then advanced antenna technologies are supported, but the reference symbol structure becomes more complex requiring coordinated allocation
Solution Approach 1:
The reference symbol structure is pre-configured and indicated to user equipment through higher-layer signaling (RRC configuration) before data transmission begins. The base station informs the UE about the presence and locations of both common and user-specific reference symbols in advance, allowing the UE to prepare appropriate receiving and processing procedures. This preliminary indication simplifies the operational complexity during actual transmission.
Solution Approach 2:
Higher-layer signaling (RRC - Radio Resource Control) acts as an intermediary between the base station and user equipment to convey reference symbol configuration information. The RRC signaling carries parameters such as the number of antenna ports, reference symbol positions, and resource block allocations, mediating the complex coordination between transmitter and receiver without requiring direct real-time interaction during data transmission.
3Measurement precision
If reference symbols are densely allocated to support multiple antenna ports, then channel quality measurement accuracy improves, but resource overhead increases
Solution Approach 1:
Different reference symbol allocation densities are applied to different resource blocks based on local requirements. Common reference symbols are transmitted across all resource blocks to provide baseline channel quality measurement, while user-specific reference symbols are allocated only in resource blocks where users are scheduled and where beam-shaping is applied. This local quality approach ensures measurement accuracy where needed while reducing overall reference symbol overhead.
Solution Approach 2:
The common reference symbols serve multiple functions: they provide channel estimation for non-beamformed transmissions, enable cell-specific reference signal operations, and support user equipment that does not require beam-shaping. This multi-functionality reduces the need for dedicated user-specific reference symbols in all resource blocks, thereby reducing overall reference symbol overhead while maintaining measurement precision for users who require it.
Data Source
AI summary
A method, system, base station and User Equipment for processing reference symbols is provided to support the transmission of both common reference symbols and user-specific reference symbols. In the present invention, a transmitting end configures the reference symbol structure for a downlink subframe according to the number of the used antenna; the transmitting end inserts the common reference symbols and the user-specific reference symbols to be transmitted into the downlink subframe according to the reference symbol structure and transmits them. With the user of the present invention, both the common reference symbols and the user-specific reference symbols can be transmitted.