HARQ Encoding Scheme for WLAN Data Transmission

The transmitting STA performs preliminary encoding at a lower code rate than needed for the final transmission. This preliminary encoded data is stored and later combined with additional parity bits generated specifically for retransmission. This preliminary action allows the system to prepare error correction capabilities in advance while maintaining flexibility for adaptive retransmission strategies.

The encoding process is segmented into two distinct phases: initial encoding at a lower code rate that produces base encoded data, and subsequent generation of additional parity bits for retransmission. This segmentation allows the system to separate the error correction preparation from the actual transmission optimization, enabling HARQ IR to combine both benefits.

The system dynamically adjusts the effective code rate through HARQ IR operations. The initial transmission uses a lower code rate for better error correction, and upon successful reception or partial decoding, the system can adaptively combine this with additional parity bits from retransmissions. This dynamic adjustment allows the effective code rate to be optimized based on channel conditions and reception outcomes, rather than being fixed.

The system changes the encoding parameter (code rate) adaptively through the HARQ process. The initial encoding uses a lower code rate, but the effective code rate improves as additional parity bits are received and combined in subsequent HARQ iterations. This parameter change is achieved not by re-encoding but by accumulating parity information, which effectively increases the code rate while maintaining error correction capabilities.

The system uses the previously generated encoded data as a base and creates additional parity bits that are essentially copies or extensions of the encoding process. Rather than implementing a completely new encoding scheme, the system copies the fundamental LDPC encoding structure and applies it iteratively to generate additional parity bits. This copying approach reduces complexity by reusing existing encoding logic.

The LDPC encoding mechanism serves multiple functions: it performs initial encoding for the first transmission, generates additional parity bits for HARQ retransmissions, and supports both incremental redundancy and chase combining modes. This multi-functionality reduces device complexity by using a single versatile encoding mechanism rather than requiring separate specialized encoders for different HARQ operations.