Storage deduplication improves write latency, increases available space, and reduces the wear of storage media by eliminating redundant writes. The flash translation layer (FTL) of a flash solid state disk (SSD) easily enables deduplication in an SSD through the simple mapping of duplicated logical pages to the same physical page. Therefore, a few deduplicating FTLs have been proposed. However, the deduplication of partially duplicated files breaks the sequentiality of data storage at the flash page level, resulting in a significant degradation of the read performance. Although increasing available storage space, reducing flash write, and extending lifespan are barely perceptible to users, extended read latency is critical to user-perceived performance. In this paper, we propose a novel deduplication FTL called Dedup-for-Speed (DFS). The DFS FTL trades surplus capacity gained through inline deduplication for improved read performance by storing duplicated pages in fast flash modes, such as the pseudo-single-level-cell(pSLC) mode. The flash mode of a page is determined by its degree of deduplications. Duplicate pages are migrated to fast flash blocks during idle intervals to minimize interference with host-issued operations. Contrary to conventional deduplication schemes, DFS improves the read performance while maintaining the aforementioned benefits of deduplication. Our evaluation of six real-world traces showed that DFS improved the read latency by 16% on average and up to 34%. It also enhanced the write latency by 64% on average and up to 82%.

Recently, a so called orthogonal spatial multiplexing (OSM) scheme was presented which allows simple maximum likelihood decoding at the receiver with single phase feedback. In this paper, by serially concatenating this scheme by a linear precoder, a new closed-loop SM scheme is proposed for two transmit and two receive antennas. By computer simulation results, we show that the proposed scheme outperforms the conventional SM and OSM.

We study fault-tolerant multicasting in multistage interconnection networks (MINs) for constructing large-scale multicomputers. In addition to point-to-point routing among processor nodes, efficient multicasting is critical to the performance of multicomputers. This paper presents a new approach to provide fault-tolerant multicasting, which employs the restricted header encoding schemes. The proposed approach is based on a recursive scheme in order to send a multicast packet to the desired destinations detouring faulty element(s). In the proposed fault-tolerant multicasting, a multicast packet is routed to its own destinations in only two passes through the MIN having a number of faulty elements by exploiting its nonblocking property.

In this paper, we study multicasting in the self-routing multistage interconnection networks (MINs) for asynchronous transfer mode (ATM) switch architectures. Many B-ISDN applications require multicast connections in addition to conventional point-to-point connections. This paper presents a novel approach to support multicast connection, on the basis of a restricted address encoding scheme which constructs a short fixed-size multicast header and a recursive scheme that recycles a multicast packet one or more times through the network to send it to the desired destinations. The proposed two-phase multicast algorithm provides deadlock-free multiple multicast connections in MIN-based ATM switches. The emphasis is on analyzing the performance of an unbuffered MIN-based switch using the multicast algorithm in terms of network throughput. The proposed algorithm can be easily applied to buffered MIN-based ATM switches.

We discuss the multicast communication in the self-routing multistage interconnection network (MIN) for constructing the internal architecture of asynchronous transfer mode (ATM) switches. Many applications of ATM switches require multicast communications in addition to conventional point-to-point communications. This paper presents a novel approach to supporting multicast communication, on the basis of the recursive scheme that recycles a multicast packet one or more times through the network to reach at desired destinations. We also propose cost-effective multicast algorithms providing deadlock-freedom in MIN-based ATM switches. The proposed algorithms require a small and fixed number of recycling passes and a reasonable number of links used. The proposed algorithms can be easily applicable to buffered MIN-based ATM switches.