Delay Tolerant eNodeB for Satellite LTE Networks
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Solution Overview
Problem
LTE networks experience communication breakdowns due to excessive round-trip delays exceeding 0.66 ms, particularly in scenarios where the distance between eNodeB and UE is greater than 100 km, leading to issues with HARQ, Random Access Procedure, Uplink Time Synchronization, and Handover Procedure.
Innovation Solution
A delay-tolerant eNodeB system that pre-acknowledges packets, continuously transmits Random Access Response messages, uses MAC control elements for timing adjustments, and employs a contention-free handover procedure to maintain reliable connections despite high channel latencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If LTE technology is used with distance between eNodeB and UE greater than 100km, then coverage area is improved, but round-trip delay exceeds 0.66ms causing communication breakdown
Solution Approach 1:
The eNodeB performs preliminary actions by pre-acknowledging packets before receiving them, and continuously transmitting Random Access Response messages before the UE sends PRACH messages. This anticipatory approach compensates for the extended propagation delay in satellite scenarios, ensuring that acknowledgment and response signals are already prepared and transmitted in advance, thereby maintaining reliable communication over distances exceeding 100km.
Solution Approach 2:
The patent implements continuous transmission of Random Access Response messages and maintains persistent acknowledgment mechanisms. The eNodeB continuously sends RAR messages without interruption, and maintains HARQ processes with extended timing, ensuring that the communication channel remains active and reliable throughout the extended round-trip delay period, thus preventing communication breakdown in satellite-based LTE networks.
2Reliability
If HARQ retransmission protocol is used with expected acknowledgment time of 4ms, then error correction is improved, but communication fails when RTT exceeds 4ms
Solution Approach 1:
The eNodeB sends pre-acknowledgment signals before the actual packet reception is complete. By anticipating the need for acknowledgment and transmitting it in advance based on expected timing, the system compensates for extended RTT conditions. This preliminary acknowledgment action ensures that the UE receives acknowledgment within the expected 4ms window even when physical propagation delay exceeds this duration.
Solution Approach 2:
The patent dynamically adjusts HARQ timing parameters based on the detected RTT conditions. The eNodeB modifies acknowledgment timing, retransmission schedules, and timing advance commands to adapt to the actual propagation delay in satellite scenarios. This dynamic adaptation maintains HARQ functionality and error correction capability regardless of whether RTT exceeds the standard 4ms expectation.
3Ease of operation
If Random Access Procedure uses maximum response time of 10ms, then connection establishment is improved, but connection fails when RTT exceeds 10ms
Solution Approach 1:
The eNodeB continuously transmits Random Access Response messages in advance of when the UE is expected to send PRACH messages. By preparing and transmitting RAR signals beforehand based on predicted timing, the system ensures that the UE receives responses within the 10ms window even when propagation delay is extended. This preliminary response transmission maintains connection establishment capability in satellite scenarios.
Solution Approach 2:
The patent implements continuous transmission of Random Access Response messages without interruption. The eNodeB maintains persistent RAR signaling to ensure that at least one response message is transmitted within the 10ms window regardless of propagation delay variations. This continuous action ensures reliable connection establishment even when RTT approaches or exceeds the maximum expected 10ms duration.
4Speed
If Uplink Time Synchronization uses timing advance command, then transmission timing is improved, but synchronization fails when RTT exceeds expected delay
Solution Approach 1:
The eNodeB calculates and transmits timing advance commands in advance, before the UE sends its uplink transmissions. By preparing timing adjustment signals beforehand and accounting for extended propagation delay in the calculation, the system ensures that timing synchronization is established correctly even when RTT exceeds standard expectations. This preliminary timing setup maintains uplink synchronization reliability in satellite scenarios.
Data Source
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AI summary
A Long-Term Evolution (LTE) E-UTRAN Node B (eNodeB) for use in satellite markets. The LTE eNodeB supports extreme channel latencies without the need for any User Equipment (UE) (e.g., mobile handsets) modifications, independent of the UE release or the technology used by the network operator. The system supports high channel latencies in LTE, though can also be used for other wireless technologies such as GSM, 5G New Radio (NR) or any other technologies with similar procedures to those used in LTE.