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Salp Swarm Algorithm (SSA) is a novel swarm technique using to optimize design problems. SSA is inspired by the swarming behavior of salp observed in the deep area of sea. In spite of its application versatility, SSA suffers from mediocre convergence rate and limited exploratory capabilities. In this paper, a Fitness Dependent Salp Swarm Algorithm (FDSSA) is proposed. The novelties of the proposed approach are the definition of a fitness coefficient able to enhance the exploration, the introduction of a novel mathematical model to describe the trajectory of salps and a mutation mechanism to increase the convergence speed. The designed algorithm is tested on unimodal and multimodal benchmark functions and then compared with well-known heuristic algorithms. The results show the superiority of FDSSA with respect to the comparison algorithms in terms of optimization and convergence performances according to their computational complexity.

Let $\mathbb{Z}_{m}\overset{\text{def}}{=}\{0,1, \ldots, (m-1)\}$ be the m-ary alphabet, $m\in \mathbb{N}$ . This paper gives some new theory and efficient designs of $\mathbb{Z}_{m}$ linear error control codes based on the elementary symmetric functions of m-ary words. Here, a $\mathbb{Z}_{m}$ linear code is a sub-module of the module $(\mathbb{Z}_{m}^{n}, +\text{mod}\ m, \mathbb{Z}_{m}, \cdot \text{mod}\ m), n\in \mathbb{N}$ , and the errors are measured in the $L_{1}$ or Lee metric. In particular, given a field, K, of characteristic $p$ = char(K) = $2, 3,5, \ldots$ prime, and given $d, m=vp^{l}, v, l, n\in \mathbb{N}$ with $d\leq m/v=p^{l}$ and $n\leq\vert K\vert -1$ , we introduce a new class of (d-1) asymmetric error correcting $\mathbb{Z}_{m}$ linear codes, $\mathcal{C}_{d}$ , of length $n$ whose redundancy is only $\rho(\mathcal{C}_{d})=n-\log_{m}\vert\mathcal{C}_{d}\vert \leq(d-1)\log_{m}\vert K\vert$ . For these codes we give very efficient field based algebraic decoding algorithms to control $d - 1$ errors actually in the Lee distance. Also for the extended codes, we give new efficient field based decoding algorithms.

Swarm robotics carries the potential of solving complex tasks using simple devices. To do so, however, one must define distributed control algorithms capable of producing globally coordinated behaviours. We propose a methodology to address the problem of the spatial coverage of multiple tasks with a swarm of robots that must not lose global connectivity. Our methodology comprises two layers: (i) a distributed Robot Navigation Controller (RNC) is responsible for simultaneously guaranteeing connectivity and pursuit of multiple tasks; and (ii) a global Task Scheduling Controller approximates the optimal strategy for the RNC with minimal computational load. Our contributions include: (i) a qualitative analysis of the literature on connectivity assessment, (ii) our proposed methodology, (iii) simulations in a multi-physics environment, (iv) real-life robot experiments, and (v) the experimental validation of connectivity, coverage optimality, and fault-tolerance.

In many communication media, optical systems, and some VLSI systems, only one errors type, either 0 a#x2192; 1 or 1 a#x2192; 0, can occur in any data word and the decoder knows a priori the error type. These types of errors are called asymmetric errors. Asymmetric Varshamov channels could be used to model some physical systems such as multilevel flash memories where there is an exponential behavior in the real distance between the sent and received symbols and so, the number of errors between these symbols should be measured according to the L1 distance. In this paper, we introduce a Varshamov error model for the general m(a#x2273;2)-ary Z-Channel with taking into account the error magnitude, but with concerning to the asymmetric case. Also, we analyze the throughput performance for Type-I selective-repeat hybrid ARQ protocols using t-Error-Correcting/All Asymmetric Error Detecting (t-AEC/AAED) codes over a noticeable Varshamov error model for the general Z-Channel.

In this paper we present a novel experimental platform for network management able to dynamically optimize the energy consumption of backbone IP networks operating with OSPF. The idea is to efficiently adjust link weights to put to sleep idle devices. The framework relies on multiple precomputed sets of link weights that are applied to the considered network domain according to real time measurements on the link utilization. The management module exploits the Simple Network Management Protocol (SNMP) to collect the load measurements and modify the link weights. The pre-computed link weights are calculated by running a state-of-the-art algorithm for off-line energy-aware traffic engineering based on predicted traffic matrices. The modules of the platforms have been implemented for Linux based environments and tested using emulated networks of virtual machines. Experimental results showed a significant reduction in terms of network resources required to route traffic demands, demonstrating how, in average, 20% of nodes and 40% of links, can be put to sleep without compromising network performance and stability.

In recent years, there has been a remarkable growth of the Internet energy consumption, which is expected to persist in the future at an even higher pace. At the same time the network access capacity of individual subscribers is rapidly reaching values high enough to move the traffic bottleneck from the access network to the core network in most scenarios. This will soon make the elastic nature of traffic an important aspect of network resource management and will require a redesign of the energy-aware traffic engineering techniques so far based on inelastic traffic demands. We propose a novel optimization approach to select a routing path for each elastic traffic demand and decide which routers and links to put to sleep so as to maximize a network utility measure depending on the traffic demand rates, while satisfying a constraint on the total energy consumption. Bandwidth is allocated to each elastic demand according to the Max-Min Fairness (MMF) paradigm, which approximates the resource allocation of the transport layer.

A new efficient coding scheme is given for second-order spectral-null (2-OSN) codes. The new method applies the Knuth's optimal parallel decoding scheme for balanced (i.e., 1-OSN) codes to the random walk method introduced by Tallini and Bose to design 2-OSN codes. If k ∈ IN is the length of a 1-OSN code then the new 2-OSN coding scheme has length n = k+r ∈ IN with an extra redundancy of r ≳ 2 log2 k + (1/2) log2 log2 k - 0.674 check bits. The whole coding process requires O(n log n) bit operations and 0(n) bit memory elements.

The general theory on partially asymmetric (t, t+)-EC/(d-, d+)-ED m-ary codes for the L1 distance is developed. In this metric, such codes are capable of correcting t- or less negative errors, detecting d or less negative errors, correcting t+ or less positive errors, and simultaneously detecting d+ or less positive errors. Based on the elementary symmetric function, a wide class of these codes with efficient decoding algorithms are given. Let S(m, n, w, D) be the set of all the m-ary words of length n with real sum of their components being equal to w mod D. Any subset of S(m, n, w, D) is called m-ary constrained weight (CW) code of length n and is known to be a (D - 1)-UED code. Given a field, K, of prime characteristic p, some m-ary CW codes of length n ≤ |K| - 1 are defined. Such codes are (t-, t+)-EC/(d-, d+)-ED and have a redundancy of ρ(c) = n - logm |C| ≤ ρ {S(m, n, w, d + 1)) + t logm |K|, with t = min{t_ + d+, d_ + t+}, d = max{t_ + d+, d_ + t+} and w ∈ IN. In particular, for t ≤ p-1, a class of essentially linear and systematic (hence, easy to encode) m-ary (t_, t+)-EC/(d_, d+)-ED CW σ-codes with length n

ReRAM has been considered as one of the potential technologies for the next-generation nonvolatile memory, given its fast access speed, high reliability, and multi-level capability. Multiple-layered architectures have been used for several megabit test-chips and memory macros [1-3]. This paper presents a MeOx-based 32Gb ReRAM test chip developed in 24nm technology.

A robust multi-period model is proposed to minimize the energy consumption of IP networks, while guaranteeing the satisfaction of uncertain traffic demands. Energy savings are achieved by putting into sleep mode cards and chassis. The study of the solution robustness shows that there is a trade-off between energy consumption and the solutions conservatism degree. The model allows this trade-off to be tuned by simply modifying a single parameter per link. The multi-period optimization is constrained by inter-period limitations necessary to guarantee network stability. Both, exact and heuristic methods are proposed. Results show that up to 60% of the energy savings can be achieved for realistic test scenarios in networks operated with flow-based routing protocols (i.e. MPLS) and with a good level of robustness to traffic variations.

In this paper we consider the problem of minimizing the energy consumption of IP networks, exploiting the traffic variations over a set of time intervals, while guaranteeing the network QoS and survivability. Energy savings are achieved by putting into sleep mode cards and chassis, when they are not necessary. Network survivability is based on a dedicated protection scheme, wherein a dedicated backup path is assigned to each demand. The multi-period optimization is constrained by inter-period limitations necessary for guaranteeing network stability. Both exact and heuristic methods are proposed. Results obtained with realistic networks operated with flow-based routing protocols (i.e. MPLS) show that up to 60% of the energy savings can be achieved without negatively affecting network resiliency.

This paper gives some new theory and design of codes capable of correcting/detecting errors measured under the Lee distance defined over m-ary words, m Є IN. Based on the elementary symmetric functions (instead of the power sums), a key equation is derived which can be used to design new symmetric (or, asymmetric) error control algorithms for some new and already known error control codes for the Lee metric. In particular, it is shown that if K is any field with characteristic char(K) = p, p odd, and u, h, n, m = uph, t Є IN are such that n ≤ (|K| − 1)/2 and t ≤ (ph − 1)/2 then there exist m-ary codes C of length n and cardinality |C| ≥ mn/|Κ|t which are capable of, say, correcting t symmetric errors (i. e., the minimum Lee distance of C is d Lee (C) ≥ 2t + 1) with t steps of the Extended Euclidean Algorithm. Furthermore, if t ≤ (p − 1)/2 then some of these codes are (essentially) linear and, hence, easy to encode.

Based on the elementary symmetric functions, this paper gives a new wide class of Goppa like codes capable of correcting/detecting errors measured under the (symmetric) L\ distance defined over the m-ary words, 2 ≤ m ≤ +∞. All these codes can be efficiently decoded by algebraic means with the Extended Euclidean Algorithm (EEA). In particular it is shown that if K is any field with characteristic char(K) ≠ 2, m Є IN U {+∞} and n, t Є IN then there exist m-ary codes C of length n ≤ (|K|− 1)/2 and cardinality |C| ≥ mn/|K|t which are capable of, say, correcting t errors (i. e., the minimum L 1 distance of C is d L1 (C) ≥ 2t + 1) with t steps of EEA. Also, if K is a finite field and 2t + 1 ≤ char(K) ≠ 2 then some of these codes are (essentially) linear and, hence, easy to encode.

This paper gives some theory and design of efficient codes capable of controlling (i. e., correcting/detecting/correcting erasure) errors measured under the L 1 distance defined over m-ary words, 2 ≤ m ≤ +∞. We give the combinatorial characterizations of such codes, some general code designs and the efficient decoding algorithms. Then, we give a class of linear and systematic m-ary codes, m = sp with s∈IN and p a prime, which are capable of controlling d ≤ p−1 errors. If n and k∈IN are respectively the length and dimension of a BCH code over GF(p) with minimum Hamming distance d + 1 then the new codes have length n and k′ = k + r log m s information digits.

The error types in some VLSI systems and some communication media is of asymmetrie in nature. In this paper, for selective-repeat ARQ protocol over m(≥2)-ary asymmetrie channel, some analysis of the throughput when using All Asymmetric Error Detecting (AAED) codes are given. For these codes, the number of retransmissions needed to receive all codewords correctly is derived. As a special case, the number of retransmissions needed to receive all codewords correctly is derived for the Z-channel.

This paper gives the theory and design of efficient codes capable of correcting errors caused by the insertion and deletion of a repeated symbol in the information sequence. Two efficient methods are described. For any fixed t + , t − ∈ IN, one method gives a fixed length scheme to encode k information bits into a systematic code of length n = k + r, with r = (t + + t − ) log 2 k + O(log log k), capable of correcting the insertion of t + repeated symbols and, simultaneously, correcting the deletion of t − repeated symbols in every codeword. The second method is a systematic variable length scheme which on average doubles the number of information bits k compared to the first method. The time complexity of the entire coding process for both schemes is T = O (k + (1+min{t − , t + })t) multiplication operations over a finite field containing k elements. The space complexity is S = O(k+t) field memory elements. The generalization to the m-ary case, m ≥ 2, is also given.

In an unordered code no codeword is contained in any other codeword. Unordered codes are All Unidirectional Error Detecting (AUED) codes. In the binary case, it is well known that among all systematic codes with k information bits, Berger codes are optimal unordered codes with r = ⌈log 2 (k+1)⌉ check bits. This paper gives some new theory on variable length unordered codes and introduces a new class of systematic unordered codes with variable length check symbols. The average redundancy of these new codes is r ≈ (1/2) log 2 (πek/2) = (1/2) log 2 k + 1.047, where k∈IN is the number of information bits. It is also shown that such codes are optimal in the class of systematic unordered codes with fixed length information symbols and variable length check symbols. The generalization to the non-binary case is also given.

A general key equation based on elementary symmetric functions is developed for decoding some binary error control codes. Here, the syndrome is obtained by computing the elementary symmetric functions (instead of the power-sums) of the received word. A new class of codes is introduced in this paper which can correct up to t0 0 rarr 1 errors and, simultaneously, up to t1 1 rarr 0 errors. The new key equation can be used to decode this new class of codes and some known codes such as some t-asymmetric error correcting (t-AEC) codes, the t-symmetric error correcting (t-SEC) BCH codes and Goppa codes. Some generalizations to the non binary case are also given.

A symbol permutation invariant balanced (SPI-balanced) code over the alphabet ZZm = {0, 1,....,m - 1} is a block code over ZZ m such that each alphabet symbol occurs as many times as any other symbol in every codeword. For this reason every permutation among the symbols of the alphabet changes a SPI-balanced code into a SPI-balanced code. This means that SPI-balanced words are "the most balanced" among all possible m-ary balanced word types, and this property makes them very attractive from the application perspective. In particular, they can be used to achieve m-ary DC-free communication, to detect/correct asymmetric/unidirectional errors on the m-ary asymmetric/unidirectional channel, to achieve delay-insensitive communication, to maintain data integrity in digital optical disks, and so on. The paper gives some efficient methods to convert (encode) m-ary information sequences into m-ary SPI-balanced codes whose redundancy is equal to roughly double the minimum possible redundancy rmin sime [(m - 1)/2] logm n - (1/2)[1 $(1/log2pi m)] m - (1/log2pim) for SPI-balanced code with k information digits and length n = k + r. For example, the first method given in the paper encodes k information digits into a SPI-balanced code of length n = k + r, with r = (m - 1) logm k + O(m logm k). A second method is a recursive method, which uses the first as base code, and encodes k digits into a SPI-balanced code of length n = k + r, with r sime (m - 1) logm n $logm[(m - 1)!]

A 3.3 V, 512 Mb PROM uses a transistorless memory cell containing an antifuse and diode. A bit area of 1.4F/sup 2/ including all overhead is achieved by stacking cells 8 high above the 0.25 /spl mu/m CMOS substrate. Read bandwidth is 1 MB/s and write bandwidth is 0.5 MB/s. A 72 b Hamming code provides fault tolerance.

Matsuzawa and Fujiwara (1988) have proposed a novel scheme to mask line faults of bus line circuits (such as address buses) due to short circuit defects between adjacent lines. We propose the fundamental theory and then present some efficient designs of these codes. Some lower and upper bounds for the optimal codes are also given.

In a constant weight w code of length n, each code word has w 1s and n-w 0s. If the ratio w/n is low, the code is referred to as a low constant weight (LCW) code. In this paper, some simple designs of LCW codes are presented. Further, the speed performance of these codes is derived and then it is shown that these codes have much better performance than the dual-rail codes, when used in asynchronous buses.