457,574 research outputs found
Probabilistic Handshake in All-to-all Broadcast Coded Slotted ALOHA
We propose a probabilistic handshake mechanism for all-to-all broadcast coded
slotted ALOHA. We consider a fully connected network where each user acts as
both transmitter and receiver in a half-duplex mode. Users attempt to exchange
messages with each other and to establish one-to-one handshakes, in the sense
that each user decides whether its packet was successfully received by the
other users: After performing decoding, each user estimates in which slots the
resolved users transmitted their packets and, based on that, decides if these
users successfully received its packet. The simulation results show that the
proposed handshake algorithm allows the users to reliably perform the
handshake. The paper also provides some analytical bounds on the performance of
the proposed algorithm which are in good agreement with the simulation results
All-to-all Broadcast for Vehicular Networks Based on Coded Slotted ALOHA
We propose an uncoordinated all-to-all broadcast protocol for periodic
messages in vehicular networks based on coded slotted ALOHA (CSA). Unlike
classical CSA, each user acts as both transmitter and receiver in a half-duplex
mode. As in CSA, each user transmits its packet several times. The half-duplex
mode gives rise to an interesting design trade-off: the more the user repeats
its packet, the higher the probability that this packet is decoded by other
users, but the lower the probability for this user to decode packets from
others. We compare the proposed protocol with carrier sense multiple access
with collision avoidance, currently adopted as a multiple access protocol for
vehicular networks. The results show that the proposed protocol greatly
increases the number of users in the network that reliably communicate with
each other. We also provide analytical tools to predict the performance of the
proposed protocol.Comment: v2: small typos fixe
Fault tolerant all-to-all broadcast in general interconnection networks
With respect to scalability and arbitrary topologies of the underlying networks in multiprogramming and multithread environments, fault tolerance in acknowledged ATAB and concurrent communications become a challenge to reliable general wormhole routing multicomputers with arbitrary topologies. In this paper, the virtual ring tree (VRT) is proposed to deal with the challenge. A single startup is needed in the two proposed algorithms by a simple virtual node space, which also reduces the complexity of routing at intermediate steps of ATAB algorithms and re-beginning an ATAB, by cacheable virtual channels. The proposed algorithm can automatically handle static faults in networks.published_or_final_versio
RSS based CERN Alerter. Information broadcast to all CERN offices.
Nearly every large organization uses a tool to broadcast messages and information across the internal campus (messages like alerts announcing interruption in services or just information about upcoming events). These tools typically allow administrators (operators) to send "targeted" messages which are sent only to specific groups of users or computers, e/g only those located in a specified building or connected to a particular computing service. CERN has a long history of such tools: CERNVMSĂ‚Ă‚s SPM_quotMESSAGE command, Zephyr and the most recent the NICE Alerter based on the NNTP protocol. The NICE Alerter used on all Windows-based computers had to be phased out as a consequence of phasing out NNTP at CERN. The new solution to broadcast information messages on the CERN campus continues to provide the service based on cross-platform technologies, hence minimizing custom developments and relying on commercial software as much as possible. The new system, called CERN Alerter, is based on RSS (Really Simple Syndication) for the transport protocol and uses Microsoft SharePoint as the backend for database and posting interface. The windows-based client relies on Internet Explorer 7.0 with custom code to trigger the window pop-ups and the notifications for new events. Linux and Mac OS X clients could also rely on any RSS readers to subscribe to targeted notifications. The paper covers the architecture and implementation aspe cts of the new system
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