Coordinated Multipoint Joint Transmission Backhaul Relaxation
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Solution Overview
Problem
Existing CoMP solutions in LTE-A systems face challenges with high backhaul requirements and strict latency, making inter-eNB CoMP JT impractical due to the need for fast and large data exchange over the X2 interface, which is not feasible with legacy topologies.
Innovation Solution
A method that reduces backhaul load and relaxes latency requirements by decoupling user plane data forwarding from control information, allowing for multi-hop, copper wire, or wireless point-to-point links, and using a CoMP management agent to select dominant interferers for joint transmission, thereby minimizing the data transferred within strict time frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CoMP joint transmission is implemented with fast and large data exchange over the X2 interface, then CoMP efficiency and system performance are improved, but backhaul requirements and latency become too strict to be feasible with legacy topologies
Solution Approach 1:
The patent applies preliminary action by having the serving eNB forward user plane data to transmitting eNBs in advance, before the actual CoMP transmission occurs. This allows transmitting eNBs to prepare their transmissions without requiring fast real-time data exchange, thereby reducing latency requirements on the X2 interface while maintaining CoMP efficiency
Solution Approach 2:
The patent segments the data exchange process into control information (forwarded in advance) and user plane data (forwarded preliminarily). This segmentation allows different types of information to be handled with different timing requirements, reducing the overall latency constraint on the backhaul link
2Reliability
If fast and large data exchange is required over the X2 interface for CoMP JT, then transmission quality is improved, but backhaul data rates and costs increase
Solution Approach 1:
The patent extracts the user plane data forwarding function from the real-time transmission path and places it in a preliminary forwarding stage. This extraction allows the main transmission path to operate with lower data rates while still achieving high transmission quality through coordinated multi-point transmission
Solution Approach 2:
By performing data forwarding in advance, the patent reduces the amount of data that needs to be transmitted over the X2 interface during the actual CoMP operation, thereby reducing backhaul data rate requirements and associated costs while maintaining transmission quality
3Productivity
If all base stations in a cooperating set exchange large amounts of data in real-time, then CoMP performance is improved, but the complexity of the backhaul network increases
Solution Approach 1:
The patent applies local quality by having each transmitting eNB receive and process only the specific user plane data relevant to its local transmission conditions and channel state. This localized data processing reduces the overall backhaul network complexity compared to a centralized approach where all data would be exchanged network-wide
Data Source
AI summary
A method for coordinated multipoint transmission includes collecting, in a serving CoMP-MA, channel state information, CSIs, reported by terminals served by eNBs within a cooperating set. The serving CoMP-MA selects dominant interferers as candidate transmitting eNBs for a terminal. CoMP joint transmission is initiated by forwarding, to the candidate transmitting eNBs, PDCP PDUs received from SGW and targeted to the selected terminal, and by setting the status of the terminal to joint transmission. High and low thresholds of PDCP buffers of the serving CoMP-MA are adjusted. As information required for air interface scheduling becomes available, the method includes extracting, in the serving CoMP-MA, radio resource allocations, RLC and MAC headers, references to user plane data, and precoding matrices from protocol entities, and forwarding them to the transmitting eNBs that have acknowledged PDCP PDUs, in order the transmitting CoMP-MA to prepare air interface for the terminal.