Design and Implementation of an Efficient Wake-Up Synchronization Scheme Based on History in a 5G Software Modem

5G adopts Discontinuous Reception (DRX) technology, which enables the User Equipment (UE) to repeat sleep and wake-up cycles for power-saving. To minimize power consumption, the UE needs to re-synchronize to a downlink signal transmitted from a serving gNodeB (gNB) for each DRX occasion. To have a synchronization technique suitable to DRX occasions, we design and implement a history-based synchronization scheme that can effectively manage the window of synchronization signal detection. The proposed scheme primarily considers the statistics of previously detected timing offsets when configuring the window of synchronization. The history information is formatted appropriately for calculating the drift of the timing offset on each DRX occasion. The proposed scheme also monitors multi-path environments and extends the detection window to the timing offset of the second path based on the probabilistic model. To demonstrate its performance, the proposed scheme is implemented on a software modem so that it can be processed in real-time. The experimental results demonstrate that the proposed scheme can reduce computational complexity and achieve more precise synchronization in a low Signal to Noise Ratio (SNR) regime.