LTE Redundant Communication Subframe Synchronization
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Solution Overview
Problem
Current redundant communication systems in LTE-based railway communications, while ensuring safety by duplicating hardware and communication paths, do not efficiently utilize bandwidth when one communication system fails, as they operate on different frequency bands and lack flexibility in resource allocation.
Innovation Solution
Synchronizing communication systems on a subframe level, using identical frequency ranges for both downlink and uplink radio frames, allowing one system to take over unused subframes of the failed system, thereby doubling available throughput in case of failure without altering bandwidth or other parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different frequency bands are assigned for each communication system, then communication reliability is maintained through redundancy, but bandwidth utilization efficiency deteriorates when one system fails
Solution Approach 1:
The patent merges both communication systems onto a single frequency band, allowing them to share the same spectral resources. This is achieved by synchronizing the two systems and assigning different time intervals (first and second time intervals within radio frames) for their respective transmissions, thereby eliminating the need for separate frequency bands while maintaining reliability through redundancy.
Solution Approach 2:
The patent segments the radio frame into different time intervals, assigning the first time interval to the first communication system and the second time interval to the second communication system. This temporal segmentation allows both systems to coexist on the same frequency band without interference, resolving the contradiction between shared bandwidth and maintained reliability.
2Device complexity
If communication systems operate independently on separate frequency bands, then system complexity is reduced, but adaptability to failure and resource sharing capability deteriorates
Solution Approach 1:
The patent introduces dynamic resource allocation where the operational communication system can adaptively use both its own allocated time interval and the time interval previously assigned to the failed system. This dynamic flexibility allows the system to maximize throughput following a failure without requiring complex reconfiguration, as the time interval allocation is predetermined but can be fully utilized when needed.
3Productivity
If both communication systems use the same frequency band simultaneously, then bandwidth utilization improves, but signal interference and collision risk increase
Solution Approach 1:
The patent segments the radio frame temporally into first and second time intervals, assigning each to different communication systems. This time-division multiplexing allows both systems to operate on the same frequency band without signal interference, as their transmissions occur in separate time slots within each radio frame.
Solution Approach 2:
The patent implements periodic alternating transmissions where the first communication system transmits during the first time interval and the second communication system transmits during the second time interval of each radio frame. This periodic alternation ensures that both systems share the frequency band equitably without simultaneous transmission conflicts or interference.
Data Source
Figure 1
Figure 2a~3
AI summary
The invention relates to a method and a system for redundant communication between a user terminal (4) and a central station (3), wherein a first and a second communication system (6, 7) are operated according to an LTE standard and are synchronised on a subframe level, wherein the first communication system (6) uses a first set (S1) of subframes (SF#n) for communication of traffic data and the second communication system (7) uses a non-overlapping second set (S2) of subframes (SF#n) for communication of traffic data, and wherein, in the case of a failure of one of the communication systems (6, 7), the respective other communication system (6, 7) uses the set (S1, S2) of subframes (SF#n) previously unused by said other communication system (6, 7) for communication of traffic data, too.