In this paper, we propose a new wireless communication transmission technique called Silent Antenna Hopping (SAH) transmission technique, to enhance physical layer security. SAH consists of a conventional phased-array transmitter followed by antennas with an on-off switching circuit. The proposed solution maintains the objective of scrambling the constellation points in both amplitude and phase in undesired directions, while preserving a clear constellation in the target direction. SAH is different from the previously-used work in the following ways:(1) SAH is not restricted to the use of phase modulation, and can accept any modulation type including QAM, (2) it does not need to modulate the signal in the RF domain, where the conventional phased-array transmitter circuits remain unchanged, (3) in the far-field, SAH scrambles the signal constellation by randomly switching-off only one of the transmitting antennas, (4) SAH can easily integrated with the current infrastructure of phased-array transmitters, and (5) SAH breaks up the correlation between the data rates and the switching speed. We analysed the SAH performance and derived an exact expression of the bit error probability, and we derived the secrecy capacity in a closed form. The results show that SAH is a simple and very efficient solution to improve the physical layer security of mm-wave communication.
This paper proposes a novel periodic optical encoder for centralized fault monitoring of fiber-to-the home (FTTH) passive optical networks (PONs). The encoder exploits a fiber ring to produce a periodic code. This reduces the cost of monitoring system while maintains good performance and high capacity. We evaluate the performance of this encoding system in terms of signal to noise ratio (SNR). We obtain an SNR of 12.5 dB for a 32 customers network in one shot measurement. We also show that capacity of 64, 128 and 256 could be accommodated in expense of larger but acceptable measurement time.
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