Biblio

Skyrmion racetrack memory (Sk-RM) is a new storage technology in which skyrmions are used to represent data bits to provide high storage density. During the reading procedure, the skyrmion is driven by a current and sensed by a fixed read head. However, synchronization errors may happen if the skyrmion does not pass the read head on time. In this paper, a polar coding scheme is proposed to correct the synchronization errors in the Sk-RM. Firstly, we build two error correction models for the reading operation of Sk-RM. By connecting polar codes with the marker codes, the number of deletion errors can be determined. We also redesign the decoding algorithm to recover the information bits from the readout sequence, where a tighter bound of the segmented deletion errors is derived and a novel parity check strategy is designed for better decoding performance. Simulation results show that the proposed coding scheme can efficiently improve the decoding performance.

Wireless Sensor Networks (WSNs) are attracted great attention in the past decade due to the unlimited number of applications they support. However, security has always been a serious concern for these networks due to the insecure communication links they exploit. In order to mitigate the possible security threats, sophisticated key management schemes must be employed to ensure the generating, distributing and revocation of the cryptographic keys that are needed to implement variety of security measures. In this paper, we propose a novel decentralized key management scheme for hierarchical grid organized WSNs. The main goal of our scheme is to reduce the total number of cryptographic keys stored in sensor nodes while maintaining the desired network connectivity. The performance analysis shows the efficiency of the proposed protocol in terms of communication overhead, storage cost and network connectivity.