Uplink Control Information Sequence Indicator for HARQ Out-of-Sequence
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Solution Overview
Problem
In wireless communications systems, scheduling and control information transmitted over shared channels can become out-of-sequence due to the Hybrid Automatic Repeat Request (HARQ) mechanism, leading to incorrect scheduling by the network, especially when this information is piggybacked onto data packets without a related sequence number.
Innovation Solution
A 2-bit or 3-bit sequence number indicator is added to the scheduling information (SI) being piggybacked on data packets to help the network scheduler identify out-of-sequence deliveries and ensure correct ordering, with the option to discard or apply out-of-sequence SI as needed, and limiting SI transmission triggers to prevent expired information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If piggybacking scheduling information on data packets is used to reduce signaling overhead, then signaling efficiency is improved, but the scheduling information may be received out-of-sequence due to HARQ parallel channels
Solution Approach 1:
A sequence indicator field is introduced as an intermediary element within the piggybacked scheduling information to mediate the sequencing problem. This indicator explicitly carries sequence information that allows the network side to correctly order the scheduling information even when packets arrive out-of-sequence due to HARQ parallel channel processing
Solution Approach 2:
The scheduling information is segmented into multiple packets transmitted over parallel HARQ channels, with each segment containing a sequence indicator. This segmentation allows independent transmission of different parts of the scheduling information while maintaining the ability to reassemble them in the correct sequence at the receiver
2Productivity
If rapid sequential SI transmissions are allowed to respond to buffer status changes, then scheduling responsiveness is improved, but the risk of applying expired or incorrect SI increases
Solution Approach 1:
Sequence indicators are preliminarily assigned to scheduling information packets before transmission. This preliminary sequencing allows the network side to pre-validate the order and validity of received scheduling information, preventing the application of expired or incorrect SI even when rapid sequential transmissions occur
Solution Approach 2:
The sequence indicator provides a feedback mechanism that allows the network side to verify the correctness and validity of received scheduling information. By checking the sequence indicator, the network can determine whether the SI is current and valid before applying it to scheduling decisions
Data Source
AI summary
Mobile station applications (419) may include an SI unit (409) for piggy backing SI onto data stored in data buffer (421) and also for adding an indicator to the SI information. The scheduling information and/or incremental control information (501) is piggy backed onto a data PDU and also has a sequence number (503) and an indicator field (505) which is added by the SI unit, such as SI unit (409), in accordance with the embodiments. The indicator may be a bit map having four bit positions. A bit position having a binary “1” value may be utilized to indicate that a previous SN of SI information remains valid. For example, “0100” of the bit map sequence may indicate that SN #3 is still valid. The base station or controller may then determine whether to implement or discard an SI information having the indicated SN.