UE Multipoint Aggregation for Inter-NodeB HSDPA Skew
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Solution Overview
Problem
In high-speed wireless networks like UMTS, Inter-NodeB HSDPA multipoint transmission leads to out-of-order delivery (skew) between MAC entities, causing data loss issues that are indistinguishable from actual data loss, affecting user equipment (UE) communication.
Innovation Solution
The user equipment (UE) employs a multipoint aggregation component to detect sequence number gaps, delay negative acknowledgments (NAKs) using a NAK delay timer, and adapt the timer based on skew duration, distinguishing skew from data loss by tracking sequence numbers from each MAC entity and transmitting NAKs only when the gap is not filled during the delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If data packets are transmitted through multiple MAC entities in inter-NodeB MP TX, then data throughput is improved, but out-of-order delivery (skew) occurs causing data loss issues that cannot be distinguished from actual data loss
Solution Approach 1:
The system performs preliminary actions by maintaining a buffer to store received data packets and implementing a reordering mechanism that rearranges packets based on sequence numbers before delivery. This preliminary reordering prevents out-of-order packets from being misidentified as lost data, thereby maintaining data delivery accuracy while allowing parallel transmission through multiple MAC entities
Solution Approach 2:
The system implements feedback mechanisms through acknowledgments (ACKs) and negative acknowledgments (NAKs) that provide information about packet reception status. The NAK is sent only when a gap in sequence numbers is detected and cannot be explained by skew, allowing the transmitter to retransmit only genuinely lost packets rather than all packets, thus maintaining reliability while enabling high-speed parallel transmission
2Reliability
If NAK is transmitted immediately upon detecting sequence number gaps, then data loss is quickly addressed, but feedback overhead increases and skew cannot be distinguished from data loss
Solution Approach 1:
Before transmitting a NAK, the system performs preliminary verification by checking whether the detected sequence number gap can be explained by skew from multiple MAC entities. The buffer stores recent packets and allows the system to verify if out-of-order packets are merely delayed rather than lost, preventing premature NAK transmission and reducing unnecessary feedback overhead
Solution Approach 2:
The system applies partial action by sending NAKs only for gaps that cannot be explained by skew, rather than sending NAKs for all sequence number gaps. This selective approach reduces feedback overhead while still addressing actual data loss, as the system partially verifies the cause of gaps before triggering retransmission requests
Data Source
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AI summary
In aspects of the present disclosure, a user equipment receives inter-NodeB multi-point transmissions, and a multipoint aggregation component detects a gap in the sequence numbers, delays transmitting a not acknowledged signal (NAK) by starting a NAK delay timer, and transmits, by a transceiver, NAK for the gap in sequence numbers in response to the NAK delay timer expiring and detecting that the gap has not been filled during the delaying. If the Medium Access Control (MAC) entity as the respective NodeB identifies itself to the Radio Link Control (RLC), out-of-order delivery (skew) can eventually be distinguished from genuine data loss before the NAK delay timer expires based upon tracking the highest sequence numbers received. Adaptive NAK delay timer can be performed by monitoring skew duration.