HARQ Process Identity Linking for MIMO Rank Adaptation
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Solution Overview
Problem
In wireless communication systems, synchronous Hybrid Automatic Repeat Request (HARQ) protocols face limitations as retransmissions cannot be scheduled at optimal channel conditions, leading to inefficiencies due to predetermined timing, modulation, coding, and resource allocation, resulting in data loss when rank changes during retransmissions in MIMO systems.
Innovation Solution
The proposed solution involves linking and deriving Hybrid ARQ process identities between codewords to allow flexible scheduling of retransmissions when rank changes, using extended PID fields and additional bits to enable efficient retransmission management across different MIMO ranks, allowing for adaptive modulation, coding, and resource allocation based on current channel conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If synchronous HARQ protocol is used with predetermined timing, then control information transmission is simplified, but retransmissions cannot be scheduled at optimal channel conditions leading to data loss
Solution Approach 1:
The patent transitions from static predetermined retransmission timing in synchronous HARQ to dynamic adaptive timing in asynchronous HARQ, where retransmission timing, modulation, coding and resource format are adapted according to prevailing channel conditions at the time of retransmission
Solution Approach 2:
The patent changes the timing parameter from fixed to variable, allowing retransmission timing to be selected based on channel conditions. It also changes modulation and coding parameters adaptively to match current channel state, improving reliability while managing complexity through controlled parameter variation
2Reliability
If asynchronous HARQ protocol is used with adaptive timing, then retransmissions can be scheduled at optimal channel conditions, but control information needs to be sent along with all subpackets increasing complexity
Solution Approach 1:
The patent applies preliminary action by sending control information only with the first subpacket transmission, where retransmission timing and parameters are predetermined. This allows subsequent retransmissions to proceed without additional control information, reducing overall complexity while maintaining adaptive capabilities
3Device complexity
If HARQ process identity is not extended for rank changes, then process ID management is simple, but retransmission fails when rank changes from 2 to 1 causing data loss
Solution Approach 1:
The patent segments the process ID space by creating separate PID fields for different transmission ranks. Rank-2 transmissions use one PID field while rank-1 transmissions use another PID field, allowing independent management of process identities for each rank type and enabling successful retransmissions when rank changes occur
Solution Approach 2:
The patent adds a rank dimension to the process ID management system. By introducing rank-specific PID fields, it creates an additional dimension for identifying HARQ processes, allowing the system to distinguish between rank-1 and rank-2 processes and manage them separately, thus preventing data loss during rank transitions
Data Source
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AI summary
Methods and apparatus for transmitting Asynchronous Hybrid Automatic Repeat reQuest (ARQ) process identities in a wireless communication system. A linking scheme is established between at least two sets of process identities of two respective corresponding codewords. When a first process identity is selected from among a first set of process identities of a first codeword, a second process identity may be derived in dependence upon the first process identity and the established linking scheme. Finally, a first packet from the first codeword is transmitted using a first transmission channel indicated by the first process identity, and a second packet is transmitted from the second codeword using a second transmission channel indicated by the second process identity. In addition, a control message including only the first process identity is transmitted.