RBS Out-of-Sequence Frame Reordering for Hetnet Reliability
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Solution Overview
Problem
In wireless communication networks, particularly in Heterogeneous Networks, data packets transmitted over IP-based solutions often arrive Out Of Sequence (OOS) at Radio Base Stations, leading to errors and unnecessary retransmissions, which can cause congestion and erroneous flow control decisions due to the lack of sequence ordering in the 3GPP RLC protocol, especially in Unacknowledged Mode.
Innovation Solution
The Radio Base Station implements a method to detect out-of-sequence frames by using timers to store frames and reassemble them in the correct order before forwarding, and in case of persistent OOS, notifies higher layers, allowing the UE to handle missing frames and reducing the load on the transport network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If IP-based transport solutions are used in Hetnet deployments, then ease of operation and adaptability are improved, but packet delivery sequence reliability deteriorates due to OOS arrivals
Solution Approach 1:
The RBS performs preliminary reordering of packets before they are delivered to higher layers. When packets arrive out of sequence, the RBS stores them temporarily and retransmits them in the correct sequence order, preventing OOS delivery to the UE and eliminating the need for higher layer reordering mechanisms.
2Device complexity
If packets are delivered out of sequence to higher layers, then device complexity is reduced, but productivity deteriorates due to unnecessary retransmissions and erroneous flow control decisions
Solution Approach 1:
The RBS performs preliminary reordering of packets before they are delivered to higher layers. When packets arrive out of sequence, the RBS stores them temporarily and retransmits them in the correct sequence order, preventing OOS delivery to the UE and eliminating the need for higher layer reordering mechanisms.
Data Source
Figure 1a
Figure 1b~1c
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AI summary
An RBS and a method performed by the RBS for transmitting data to a UE, the RBS receiving frames from a network node by means of an RLC protocol mode are provided. The method comprises receiving (110) a frame F1 from the network node, the frame having a sequence number, N. If the last received frame F0, prior to the received frame F1, has a sequence number lower than N-1, then the method comprises starting (120) a first timer T1 having a predefined length in time and temporarily storing (130) the received frame F1. If a subsequent frame F2 having a sequence number lower than N and higher than the sequence number of frame F0 is received (140), then the received frame F2 is stored (150). When all frames having sequence number between the sequence number of frame F0 and N have been received during the predefined length of the first timer T1, then the method comprises forwarding 160 the stored frames and/or received frames to the UE in the order of the sequence numbers.