Performance of free space optical communication using M-array receivers at atmospheric conditions

Abstract: In free space optical (FSO) communication links, atmospheric parameters including absorption, scattering and turbulence have significant impacts on the quality of laser beams propagating through the atmosphere. Absorption and/or scattering, due to atmospheric particles result in optical losses, whereas turbulence contributes to the intensity scintillation that can severely impair the operation of FSO communications systems. In this paper, using a modified model we analyze the atmospheric effects on the signal-to-noise ratio (SNR) and the bit error rate (BER) of an FSO system. We show that there is an improvement in BER when using M-array receivers instead of one a single receiver

Efficient Entanglement Measure for Graph States

In this paper, we study the multipartite entanglement properties of graph states up to seven qubits. Our analysis shows that the generalized concurrence measure is more efficient than geometric entanglement measure for measuring entanglement quantity in the multi-qubit graph states.Comment: 10 pages, 4 table

Improving the efficiency of spam filtering through cache architecture

Blacklists (BLs), also called Domain Name Systembased Blackhole List (DNSBLs) are the databases of known internet addresses used by the spammers to send out the spam mails. Mail servers use these lists to filter out the e-mails coming from different spam sources. In contrary, Whitelists (WLs) are the explicit list of senders from whom e-mail can be accepted or delivered. Mail Transport Agent (MTA) is usually configured to reject, challenge or flag the messages which have been sent from the sources listed on one or more DNSBLs and to allow the messages from the sources listed on the WLs. In this paper, we are demonstrating how the bandwidth (the overall requests and responses that need to go over the network) performance is improved by using local caches for BLs and WLs. The actual sender\u27s IP addresses are extracted from the e-mail log. These are then compared with the list in the local caches to find out if they should be accepted or not, before they are checked against the global DNSBLs by running \u27DNSBL queries\u27 (if required). Around three quarters of the e-mail sources have been observed to be filtered locally through caches with this method. Provision of local control over the lists and lower search (filtering) time are the other related benefits. © 2008 IEEE