Coordinated Multi-Point Transmission Using MBSFN Subframes
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Solution Overview
Problem
Current LTE networks face challenges in achieving high spectral efficiency and data rates due to limitations in downlink MIMO transmission, particularly at cell edges, where inter-cell interference and resource conflicts hinder efficient demodulation reference signal (DRS) configuration and CoMP transmission.
Innovation Solution
The implementation of Coordinated Multiple Point (CoMP) transmission using multi-broadcast single frequency network (MBSFN) subframes, where DRS from different transmission points are configured in the same time/frequency resources, and non-codebook based precoding is employed to enhance channel estimation and data demodulation, reducing resource conflicts and increasing network flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional downlink MIMO transmission is used, then system capacity is increased, but inter-cell interference and resource conflicts increase at cell edges
Solution Approach 1:
The patent merges multiple transmission points (eNBs) into a coordinated CoMP transmission system that operates as a unified virtual cell. Multiple eNBs coordinate their downlink transmissions to serve cell-edge UEs simultaneously, combining their signal strengths constructively while sharing the same time-frequency resources, thereby increasing system capacity without proportionally increasing inter-cell interference.
Solution Approach 2:
The patent introduces a coordinated control mechanism as an intermediary between multiple eNBs and cell-edge UEs. This coordination framework manages resource allocation and transmission scheduling across multiple transmission points, enabling efficient resource sharing and reducing conflicts that would otherwise occur in conventional independent MIMO transmissions.
2Measurement precision
If DRS are transmitted from multiple transmission points, then channel estimation accuracy is improved, but resource conflicts and overhead increase
Solution Approach 1:
The patent makes the DRS transmission pattern universal across all CoMP transmission points by configuring them to transmit DRS in the same time-frequency resources with identical patterns. This multi-functional approach allows a single DRS configuration to serve all transmission points simultaneously, improving channel estimation accuracy while avoiding resource conflicts through standardized, coordinated transmission.
Solution Approach 2:
The patent changes the transmission parameters of DRS by enabling multiple transmission points to use identical time-frequency resource allocation and transmission patterns. This parameter standardization across CoMP transmission points allows accurate channel estimation from multiple points without creating resource conflicts, as all points operate with matched parameters.
3Productivity
If CoMP transmission with MBSFN subframes is used, then spectral efficiency is improved, but network coordination complexity increases
Solution Approach 1:
The patent segments the downlink transmission into distinct MBSFN subframes dedicated to CoMP transmissions. By separating CoMP transmission time from conventional transmission time, the system can efficiently coordinate multiple eNBs in specific time slots without interfering with normal operations, thereby improving spectral efficiency while managing coordination complexity through temporal segmentation.
Solution Approach 2:
The patent applies CoMP transmission with MBSFN subframes selectively to specific service areas and user groups rather than network-wide. This partial application allows the system to achieve high spectral efficiency improvements in cell-edge regions where CoMP is most beneficial, while avoiding the full coordination complexity burden across the entire network.
Data Source
AI summary
Coordinated multi-point (CoMP) transmissions in a cellular network is performed using multi-broadcast single frequency network (MBSFN) subframes. During CoMP transmission, demodulation reference signals (DRS) are placed in the one portion the MDSFN subframe, while cell-specific reference signals (CRS) are placed in a separate portion of the MDSFN subframe. Therefore, no CRS-DRS collision will occur during CoMP transmission.