IEEE 802.11n defines two schemes of frames aggregation aimed at maximize utilizing WLAN PHY efficiency at MAC level, through sharing headers and timings overheads. Despite their efficiencies in enhancing the MAC throughput, the schemes are characterized with yet other overheads due to the aggregation. Moreover, none of the two schemes is optimal in every condition: Both should work together to achieve this. In this paper, in order to optimize channel's bandwidth utilization, we proposed an enhanced A-MSDU with minimal headers overhead, and an efficient two-level aggregation scheme utilizing the enhanced A-MSDU. Results from the simulation show superiority of the proposed two-level aggregation in respect of throughput and overall channel utilization.

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Field exponentiation and scalar multiplication are the pillars of and the most computationally expensive operations in the public key cryptosystems. Optimizing the operation is the key to the efficiency of the systems. Analogous to the optimization is solving addition chain problem. In this study, we survey from the onset of the addition chain problem to the state-of-the-art heuristics for optimizing it, with the view to identifying fundamental issues that when addressed renders the heuristics most optimal mean of minimizing the two operations in various public key cryptosystems. Thus, our emphasis is specifically on the heuristics: Their various constraints and implementations efficiencies. We present possible ways forwards toward the optimal solution for the addition chain problem that can be efficiently applied for optimal implementation of the public key cryptosystems.

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