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In this paper, we propose a combined method of GCR Block Ack and Unsolicited Retry for binary data lossless groupcast over wireless LANs. The two mechanisms are standardized as IEEE 802.11aa GCR for audiovisual transmission. In the proposed method, the sender transmits each frame twice without acknowledgment as Unsolicited Retry under lossy wireless link conditions. After transmitting twice, the sender enters the Block Ack sequence. In addition, we apply TXOP-Bursting, which allows a terminal to send frames sequentially with high priority during the TXOP limit, to the combined method. To show the proposal's effectiveness, we carry out a computer simulation. We assume binary data transmission of about 40MB and assess the time of complete reception at all the receivers. From the result, we find that the proposed method can shorten the received time against the conventional Block Ack method.
Effects of electron beam irradiation at 15 keV on graphene are investigated by optical and electron characterization using Raman and two-terminal resistance measurement and photoconductivity measurement. In Raman spectra, increase of defects in D-peak to G-peak ratio by increase of electron irradiation by 70 mC/cm2 was found. Resistance of graphene showed an increase after the irradiation. Rather sensitive change was found in photoconductivity of irradiated graphene under ultra-violet (UV) illumination, suggesting irradiation induced defects affect a photoconductivity properties of the graphene.