HSDPA Receiver Window Stall Avoidance
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Solution Overview
Problem
In 3GPP HSDPA networks, transmission stalls can occur due to loss of radio coverage, leading to delayed detection of lost packet data units and inefficient retransmissions, especially in areas with limited coverage like tunnels, resulting in prolonged stall times and potential data loss.
Innovation Solution
Implementing an enhanced stall avoidance procedure that uses a receiver window of fixed size to maintain in-sequence delivery of packet data units from the MAC layer to the RLC layer, incorporating monitoring of channel quality and sequence numbers to manage reordering and retransmissions effectively, and employing accumulated quality parameters to trigger modified recovery procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional ARQ protocols are used for packet retransmission, then reliability of data delivery is improved, but transmission stall time increases when radio coverage is lost
Solution Approach 1:
The patent applies preliminary action by proactively detecting coverage loss through monitoring mechanisms (T310 timer, out-of-sync indications) before the traditional ARQ protocol can detect the problem through missing acknowledgments. This early detection allows the system to initiate recovery procedures ahead of time, reducing the stall time while maintaining reliable data delivery through coordinated retransmission handling between MAC-hs and RLC layers.
2Reliability
If in-sequence delivery is enforced from MAC-hs to RLC layer, then data integrity is improved, but transmission efficiency deteriorates due to waiting for missing packets
Solution Approach 1:
The patent applies segmentation by separating the detection function (monitoring coverage loss through T310 timer and out-of-sync indications) from the delivery function (in-sequence packet delivery at RLC layer). This allows the system to maintain in-sequence delivery for data integrity while the MAC-hs layer can independently handle retransmissions and the network can initiate early recovery, thus improving transmission efficiency without sacrificing data integrity.
Solution Approach 2:
The patent introduces an intermediary mechanism (the enhanced stall avoidance procedure with coordinated MAC-hs and RLC layers) that mediates between the in-sequence delivery requirement and transmission efficiency. The MAC-hs layer monitors coverage and triggers early recovery, while the RLC layer maintains in-sequence delivery, allowing the system to balance both requirements through this intermediary coordination layer.
3Stability of the object's composition
If receiver window is maintained for in-sequence delivery, then packet ordering is improved, but complexity of stall avoidance procedures increases
Solution Approach 1:
The patent applies merging by combining the stall avoidance functionality with the existing receiver window mechanism. Instead of implementing a separate complex stall avoidance system, the patent integrates coverage loss detection (through T310 timer and out-of-sync indications) and recovery procedures directly into the receiver window management at the RLC layer, thereby maintaining packet ordering stability while reducing overall system complexity.
Data Source
AI summary
A method and apparatus is provided for performing normal reordering or timer based stall avoidance or window based stall avoidance, for instance for a 3GPP HSPDA compliant user entity; the method furthermore comprising the steps of deriving an accumulated quality measure pertaining to the packet data being communicated from the transmitter entity to the receiver entity; comparing the accumulated quality measure with a predetermined threshold value; if the accumulated quality measure meets predefined criteria, moving the window corresponding to the highest received value forward to a position corresponding to the received sequence number; and setting the next expected value in the receiver window forward to a position corresponding to a rear position of the window determined by the window size.