Twisted light beams such as optical angular momentum (OAM) with numerous possible orthogonal states have drawn the prodigious contemplation of researchers. OAM multiplexing is a futuristic multi-access technique that has not been scrutinized for optical satellite communication (OSC) systems thus far, and it opens up a new window for ultra-high-capacity systems. This paper presents the 4.8 Tbps (5 wavelengths × 3 OAM beams × 320 Gbps) ultra-high capacity OSC system by incorporating polarization division multiplexed (PDM) 256-Quadrature amplitude modulation (256-QAM) and OAM beams. To realize OAM multiplexing, Laguerre Gaussian (LG) transverse mode profiles such as LG00, LG140, and LG400 were used in the proposed study. The effects of the receiver’s digital signal processing (DSP) module were also investigated, and performance improvement was observed using DSP for its potential to compensate for the effects of dispersion, phase errors, and nonlinear effects using the blind phase search (BPS), Viterbi phase estimation (VPE), and the constant modulus algorithm (CMA). The results revealed that the proposed OAM-OSC system successfully covered the 22,000 km OSC link distance and, out of three OAM beams, fundamental mode LG00 offered excellent performance. Further, a detailed comparison of the proposed system and reported state-of-the-art schemes was performed.
We address the problem of incorporating message-based priority classes in random access protocols. The organization of these classes is based on the different packet delay requirements of higherlayer applications. In this paper, a novel node partitioning mechanism to restrict contention only t o higher priority packets is introduced. We describe node partitioning carrier sense multiple access (NP-CSMA), a protocol that uses CSMA [1,21 as its base access mechanism, and incorporates three priority mechanisms that influence different aspects of the channel access. These are node partitioning, priority queueing a t station buffers, and prioritized persistence. A detailed simulation model i s described. Simulation studies that demonstrate the effect of these mechanisms, separately and in concert, on the throughput and delay of the various priority classes are presented. We show how desired performance can be achieved by suitable variation of protocol parameters.-A large number of local computer networks are based on a broadcast bus topology, which allows full connectivity between nodes a t a relatively low cost. This topology is ideally suited for the bursty traffic typically generated in a local network with many interactive applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.