Wireless Backhaul Transmission Coordination Guard Period Insertion
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Solution Overview
Problem
In wireless backhaul paths, especially in high-frequency LTE systems, Tx-to-Rx interferences and Tx-Tx overlaps occur due to propagation delays and asynchronous node synchronization, which hinder advanced features like Coordinated Multi-Point (COMP) and can lead to reduced transmit power or reference timing confusion.
Innovation Solution
A method and network node that determine subframe allocations and insert Guard Periods (GPs) into subframes to prevent interference and overlap, maintaining synchronization and allowing for advanced features like COMP, by transmitting instructions to downstream nodes to insert GPs based on subframe allocations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If TDM scheme is employed between access link and backhaul link of relay, then transmission coordination is simplified, but Tx-to-Rx interference occurs due to propagation delay
Solution Approach 1:
The patent applies preliminary action by having the relay node advance the transmission timing of upstream subframes before the actual transmission occurs. The relay calculates a timing advance value based on the detected timing offset and applies it in advance to ensure that upstream transmissions do not interfere with downstream receptions. This preemptive timing adjustment resolves the Tx-to-Rx interference issue while maintaining TDM coordination simplicity.
2Object-affected harmful factors
If reference timing is advanced to avoid Tx-to-Rx interference, then interference is reduced, but upstream transmission timing is advanced too much causing COMP feature loss
Solution Approach 1:
The patent applies local quality by differentiating the timing adjustment approach for different link directions. Downstream transmissions maintain their original timing relative to the eNB, while only upstream transmissions receive the timing advance adjustment. This selective local adjustment allows the relay to avoid interference on its receive side without disrupting the synchronized timing needed for COMP features on the downstream access link.
3Device complexity
If subframe allocation is fixed, then transmission coordination is simple, but Tx-Tx overlap occurs due to propagation delay
Solution Approach 1:
The patent applies dynamics by making the subframe transmission timing adjustable rather than fixed. The relay dynamically calculates timing advance values based on detected timing offsets and applies them to upstream subframe transmissions. This dynamic timing adjustment allows the system to adapt to propagation delays and avoid Tx-Tx overlap while maintaining a simple TDM-based subframe allocation framework.
Data Source
AI summary
The disclosure provides a method (400) for transmission coordination on a wireless backhaul path. The wireless backhaul path comprises at least a network node and its upstream node and downstream node. The method comprises, at the network node: determining (S410) a subframe allocation for transmissions to and from the network node; and transmitting (S420) to the downstream node an instruction to insert a Guard Period (GP) into a first subframe from the downstream node to the network node based on the determined subframe allocation, so as to avoid interference on the first subframe from a subframe immediately following the first subframe.