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This paper proposes a modified subcarrier design of the orthogonal frequency-division multiplexing (OFDM) scheme for supporting the concept of partially overlapped channels (POC) in wireless local area networks. Our proposed scheme, named as “channel-overlapped OFDM (CO-OFDM)”, enables the POC in OFDM by reconfiguring its subcarrier alignment and creating subcarrier subsets that allow clear transmission between nodes by using different non-orthogonal channels. This makes the nodes maintain connectivity with each other through beaconing even though they use adjacent channels. In addition, simultaneous data transmission can be achieved via channel switching and MIMO-based data transmission, thereby increasing the overall throughput of the network. Further, we integrate our CO-OFDM into IEEE 802.11a/g/n/ac-based wireless networks and analyse its superiority over existing protocols through mathematical modelling. Evaluation results show that the proposed CO-OFDM guarantees over 300% performance increase in network capacity.

The research presented in this paper proposes methods for enhancing the energy efficiency and quality of service (QoS) for WLAN-based Device-to-Device communications. We focus specifically on the research related to Wi-Fi Direct technology in order to provide better services for a wider range of Wi-Fi D2D applications. Although Wi-Fi Direct defines two power management schemes for providing energy efficiency in P2P devices, neither is sufficient for meeting the power efficiency and reliability requirements for various services. In order to alleviate this problem, the proposed scheme, which is referred to as Dynamically Synchronized Power Management (DSPM), proposes a method for synchronizing the active time slots with the data transmission intervals and adjusts the sleep and active cycles accordingly. Furthermore, transmission time slots are adjusted dynamically depending on the status of data transmission in order to further enhance the energy efficiency of D2D services while maintaining their service quality. Mathematical analysis and simulations are used to compare the proposed scheme with the existing power schemes for Wi-Fi Direct and analyze its effectiveness.

We present a patient with phakomatosis pigmentovascularis (PPV) type IIb accompanied with venous hypoplasia, from the inferior vena cava to the superficial femoral vein. Although it is not obvious whether this vascular anomaly, which is probably congenital, is coincidental or not, it is possible that the 2 diseases have some relationship each other, because PPV is thought to result from abnormal vasomotor activity during the embryonic period. In the diagnosis of type II PPV, careful examination and several studies are required to determine systemic involvement that may include large vessel changes.