• Journal of Communications and Networks
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• v.18 no.3
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• pp.364-374
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• 2016

With vast amounts of spectrum available in the millimeter wave (mmWave) band, small cells at mmWave frequencies densely deployed underlying the conventional homogeneous macrocell network have gained considerable interest from academia, industry, and standards bodies. Due to high propagation loss at higher frequencies, mmWave communications are inherently directional, and concurrent transmissions (spatial reuse) under low inter-link interference can be enabled to significantly improve network capacity. On the other hand, mmWave links are easily blocked by obstacles such as human body and furniture. In this paper, we develop a multi-hop relaying transmission (MHRT) scheme to steer blocked flows around obstacles by establishing multi-hop relay paths. In MHRT, a relay path selection algorithm is proposed to establish relay paths for blocked flows for better use of concurrent transmissions. After relay path selection, we use a multi-hop transmission scheduling algorithm to compute near-optimal schedules by fully exploiting the spatial reuse. Through extensive simulations under various traffic patterns and channel conditions, we demonstrate MHRT achieves superior performance in terms of network throughput and connection robustness compared with other existing protocols, especially under serious blockage conditions. The performance ofMHRT with different hop limitations is also simulated and analyzed for a better choice of the maximum hop number in practice.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1726-1731
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• 2003

The firewall is generally used to protect the internal information system from intruders and hackers who attack through the Internet. However, it is very difficult for a user to verify the performance of the firewall as well as the difference of the performance for the operating mode such as Bridge Mode and Gateway Mode. In this paper, the performance of a firewall on the operating systems or windows 2000, Linux, and FreeBSD is compared. Finally, The performance of a firewall on the FreeBSD is compared at different operating modes and the effect of the number of rules by testing throughput of a firewall is analyzed.