A Design of Parity Check Matrix for Iterative Detection and Decoding of Implicitly Concatenated Channel Code in Bluetooth Low Energy

摘要

This paper designs parity check matrix of iterative detection and decoding (IDD) for an implicitly concatenated channel code structure in Bluetooth low energy (BLE) systems. Non-coded BLE transmission modes do not have any channel code. However, we focus on trellis structures of Gaussian frequency shift keying (GFSK) modulation and 24-bit redundancy check (CRC-24) encoder as a concatenated channel code. On the basis of trellis structure, maximum a-posteriori probability (MAP) detector and sum-product algorithm (SPA) decoder is carried out for GFSK and CRC-24, respectively. For the decoding of the concatenated code, we apply IDD that exchanges log-likelihood ratios (LLRs) between GFSK detector and CRC-24 decoder for obtaining the iterative gain. However, a simple IDD scheme is subject to an ill convergence problem in iterative behavior. To solve this issue, the parity check matrix is designed and updated in each iteration step. Simulation results demonstrate the validity of the designed parity check matrix and proposed IDD structure, especially in the very short message packet. As a result, the proposed method can obtain 5.76 [dB] coding and iterative gain at a maximum, in comparison with conventional detection scheme. Furthermore, impacts of channel estimation errors are characterized.