MIMO Reference Signal Transmission Overhead Reduction
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Solution Overview
Problem
In MIMO communication systems, especially in LTE-A, there is a challenge in minimizing reference signal (RS) overhead while ensuring compatibility with existing LTE UE systems and maintaining efficient transmission of data streams, particularly with the addition of new antennas which increases complexity and interference.
Innovation Solution
The method involves configuring Common Reference Signals (CRS) and Dedicated Reference Signals (DRS) to be transmitted at specific cycles and in specific regions of the radio frame, allowing for efficient transmission of reference signals to both existing and new UEs, with CRS transmitted at a low duty cycle and DRS used for each UE in every subframe, minimizing additional overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If Common Reference Signals (CRS) are transmitted at a low duty cycle to minimize overhead, then reference signal overhead is reduced, but channel estimation accuracy may deteriorate
Solution Approach 1:
The patent implements periodic transmission of CRS at specific cycles (e.g., every 5ms or 10ms) rather than continuous transmission. This periodic action reduces the overall overhead of reference signals while maintaining sufficient channel estimation accuracy by capturing channel variations at representative intervals, thus resolving the contradiction between minimizing overhead and maintaining estimation precision.
Solution Approach 2:
The patent segments the reference signal transmission by dividing it into different types (CRS and DRS) with different transmission cycles and purposes. CRS is transmitted periodically for general channel estimation, while DRS is transmitted more frequently for specific UE-specific estimation. This segmentation allows the system to minimize overall overhead while maintaining accuracy where needed.
2Measurement precision
If Dedicated Reference Signals (DRS) are transmitted for each UE in every subframe to ensure accurate channel estimation, then channel estimation accuracy is improved, but reference signal overhead increases
Solution Approach 1:
The patent applies different reference signal transmission strategies to different UEs based on their specific needs. DRS is transmitted for UEs requiring precise channel estimation (e.g., those with high data rates or poor channel conditions), while other UEs may rely on CRS alone. This local quality approach ensures accurate channel estimation for critical UEs without unnecessarily increasing overhead for all UEs.
3Productivity
If multiple antennas are added to increase MIMO capacity, then data transmission rate is improved, but system complexity and interference increase
Solution Approach 1:
The patent segments the reference signal resources by antenna port, assigning specific time-frequency resources to each antenna port's CRS and DRS transmissions. This segmentation allows the system to support multiple antennas and high data transmission rates while managing complexity through structured resource allocation and reducing interference through orthogonal resource assignment.
Data Source
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AI summary
The present invention relates to a method for transmitting a reference signal (RS) for measuring a channel in a downlink MIMO (Multi Input Multi Output) system that supports: a first user device supporting N base station transmission antennas out of a total of M base station transmission antennas and a second user device supporting M (M > N) base station transmission antennas. The method comprises the steps of: grouping a certain number of subframes or a resource block (RB) to transmit a common reference signal (CRS) for M transmission antennas from the base station; and transmitting the subframes or the resource block to the second user device. The grouped subframes or the resource block are transmitted to the second user terminal in a specific time period, and in the subframes or the resource block, the common reference signal is mapped to different transmission antennas ports corresponding to a quotient which is obtained by dividing M by a specific number.