Compact Downlink Control Information Messages for URLLC
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Solution Overview
Problem
In wireless communication systems like LTE and NR, the large size of downlink control information (DCI) messages leads to performance and efficiency issues, particularly in ultra-reliable, low-latency communication (URLLC) scenarios where reliability and low error rates are critical.
Innovation Solution
The proposed solution involves generating compact DCI messages by reducing the number of bits in fields such as the redundancy version (RV) field, modulation and coding scheme (MCS) field, and hybrid automatic repeat request (HARQ) process field, allowing for more efficient channel coding and improved reliability of the control channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the DCI message includes complete fields for MCS, RV, and HARQ process with standard bit lengths, then the control information is comprehensive and supports general communication scenarios, but the DCI message size becomes large leading to reduced reliability and increased overhead in URLLC scenarios
Solution Approach 1:
The patent extracts and removes unnecessary or redundant fields from the DCI message structure. Specifically, it omits the RV field when single-redundancy-version mode is configured, and reduces the HARQ process field from 4 bits to a smaller size when fewer HARQ processes are active. This extraction of unnecessary elements directly reduces the DCI message size while maintaining essential control information for URLLC reliability.
Solution Approach 2:
The patent implements dynamic DCI message formatting where the structure and bit allocation of DCI fields are adapted based on operational conditions. The network configures different DCI formats dynamically depending on whether single or multiple RVs are used, and adjusts the HARQ process field size based on the number of active HARQ processes. This dynamic adaptation allows the DCI message to be compact for URLLC while maintaining flexibility for different communication scenarios.
2Reliability
If the DCI message uses a larger number of bits for HARQ process field (4 bits for 16 processes), then all HARQ processes can be addressed, but the control channel overhead increases and reliability decreases for URLLC with shorter TTIs
Solution Approach 1:
The patent changes the parameter of the HARQ process field from a fixed 4-bit representation to a variable-length representation. When the network determines that fewer than 16 HARQ processes are active, it configures a reduced bit width for this field (e.g., 2 or 3 bits). This parameter change reduces the control signaling overhead and improves channel coding efficiency without losing the ability to address all necessary HARQ processes for the current TTI configuration.
3Productivity
If the MCS field uses 5 bits to indicate all possible modulation and coding schemes, then full flexibility is available, but the DCI message size increases and channel coding efficiency decreases
Solution Approach 1:
The patent applies local quality by making the MCS field bit width adaptive to the specific URLLC service requirements. Instead of uniformly using 5 bits for all scenarios, the network configures the appropriate number of bits based on the required code rates and modulation orders for the specific URLLC traffic. This localized optimization improves channel coding efficiency for URLLC while maintaining the ability to select appropriate MCS values for the given service requirements.
Data Source
AI summary
A method, network node and wireless device are disclosed. According to one aspect, a network node is configured to select between a first mode of operation and a second mode of operation. The first mode of operation includes generating a first downlink control information (DCI) message having a first number of bits. The second mode of operation includes selecting or generating a second DCI message having a second number of bits less that the first number of bits in at least one of the following fields: a redundancy version (RV) field, a modulation and coding scheme (MCS) field and a hybrid automatic repeat request (HARQ) process field.