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Abstract: In this paper we address an aspect of the mutual influence between the PHY layer budding blocks (FEC Blocks) and the MAC level allocations in the Uplink and Downlink of IEEE 802.16e/WiMAX networks. In these networks it is possible to transmit MAC level frames, denoted MAC PDUs, such that a PDU contains an integral number of fixed size Data Blocks. PDUs are transmitted over PHY Bursts, which are divided into FEC Blocks. We suggest several algorithms to compute the best way to define PDUs in a Burst in order to maximize several performance criteria. We also give guidelines on how to choose the best Modulation/Coding Scheme (MCS) to use in the Burst, given the SNR of the channel and the performance criteria. [Copyright &y& Elsevier]

Abstract: Reliability and security of broadcasting is critical in Wireless Sensor Networks (WSNs). Since reliability and security compete for the same resources, we are interested in jointly solving for error control coding (to achieve reliability) and integrity for a broadcast scenario. We assume Byzantine attacks in which the adversary can compromise nodes and then drop (or modify) the legitimate packets or inject its own packets. For reliable and efficient multihop broadcasting, it is critical to reduce the energy consumption and latency. To prevent the adversary from consuming the scarce network resources by injecting bogus packets, each receiver node should make sure that packets it receives are authentic and it filters out malicious packets immediately. We build our authentication scheme, on top of a reliable and energy efficient broadcasting protocol called Collaborative Rateless Broadcast (CRBcast) to improve efficiency and reliability. On contrary to the previous schemes, our scheme is resilient with respect to Byzantine adversary as well as routing and flooding attacks and protocol exploits. Moreover, we compared our scheme with the previously proposed broadcast authentication schemes and showed that our scheme outperforms them in terms of efficiency and data availability. This is a crucial improvement over the previous schemes that ensure availability by flooding, introducing very large communication overhead and latency. [Copyright &y& Elsevier]

Abstract: Prefix scheme is popular to label XML tree. Unfortunately, the code length is rapidly increased with the depth increment. In order to overcome this defect, we propose a novel prefix encoding scheme based on layered structure. In our scheme, the XML document tree firstly is partitioned into some subtrees according to the segment granularity, whose roots are uniquely labeled by region codes. And then the nodes inside the subtrees are encoded by prefix codes. Finally, it is necessary to establish the linear table to link the root-of-subtree region codes and layered region prefix codes in upper rank subtrees, which can help to restore the layered codes to the complete one in the whole tree. Extensive theoretic analysis and experimental results show that the new labeling scheme has relatively smaller mean coding length, which is not increased with the increment of XML document, and shorter query response time for the smaller coding length. Therefore, we can conclude that this scheme is a better one which accelerates query process and saves the store space for the codes. [Copyright &y& Elsevier]