Impact of deployment size on the asymptotic capacity for wireless ad hoc networks under Gaussian channel model

We study the throughput capacity and transport capacity for both random and arbitrary wireless networks under Gaussian Channel model when all wireless nodes have the same constant transmission power P and the transmission rate is determined by Signal to Interference plus Noise Ratio (SINR). We consider networks with n wireless nodes \(\{v_1,v_2,\ldots,v_n\}\) (randomly or arbitrarily) distributed in a square region B _a with a side-length a. We randomly choose n _s node as the source nodes of n _s multicast sessions. For each source node v _i , we randomly select k points and the closest k nodes to these points as destination nodes of this multicast session. We derive achievable lower bounds and some upper bounds on both throughput capacity and transport capacity for both unicast sessions and multicast sessions. We found that the asymptotic capacity depends on the size a of the deployment region, and it often has three regimes.     

Capacity of large hybrid erasure networks with random node distribution

The Gupta–Kumar’s nearest-neighbor multihop routing with/without infrastructure support achieves the optimal capacity scaling in a large erasure network in which n wireless nodes and m relay stations are regularly placed. In this paper, a capacity scaling law is completely characterized for an infrastructure-supported erasure network where n wireless nodes are randomly distributed, which is a more feasible scenario. We use two fundamental path-loss attenuation models (i.e., exponential and polynomial power-laws) to suitably model an erasure probability. To show our achievability result, the multihop routing via percolation highway is used and the corresponding lower bounds on the total capacity scaling are derived. Cut-set upper bounds on the capacity scaling are also derived. Our result indicates that, under the random erasure network model with infrastructure support, the achievable scheme based on the percolation highway routing is order-optimal within a polylogarithmic factor of n for all values of m.     

Efficient Multicast Association to Improve the Throughput in IEEE 802.11 WLAN

This paper deals with the problem of optimal association of stations (S T A s) to access points (A P s) for mulicast services in IEEE 802.11 WLAN. In a multicast session, all the subscribed S T A s receive the multicast data packet at the same data rate (R _{m i n} ) from their respective serving A P s. A higher value of R _{m i n} improves the multicast throughput by completing the ongoing multicast session in lesser time. This also improves the unicast throughput as the cycle duration is shared by the unicast and multicast sessions. To provide multicast services to the S T A s, we need to select a minimum cardinality subset of A P s as the system message overhead depends on this cardinality. However, such a minimum cardinality subset of A P s may not be possible to activate simultaneously due to the limited number of available orthogonal frequency channels. In this paper, we develop a combined greedy algorithm that selects a subset of A P s with minimum cardinality for which a conflict-free frequency assignment exists and finds an association between the S T A s and the selected A P s that maximizes the R _{m i n} value. Through simulation we have shown that the proposed algorithm selects significantly less number of A P s for different R _{m i n} values in comparison to the well-known metrics for multicast association like RSSI, minimum hop-distance, normalized-cost and in-range STA number.     

Secure Relay Selection of Cognitive Two-Way Denoise-and-Forward Relaying Networks

In this paper, secrecy performance of a cognitive two-way denoise-and-forward relaying network consisting of two primary user (PT and PD) nodes, two secondary source (SA and SB) nodes, multiple secondary relay (\({\textit{SR}}_i\)) nodes and an eavesdropper (E) node is considered, where SA and SB exchange their messages with the help of one of the relays using a two-way relaying scheme. The eavesdropper tries to wiretap the information transmitted between SA and SB. To improve secrecy performance of the network, two relay selection schemes called maximum sum rate and maximum secrecy capacity based relay selection (MSRRS and MSCRS) are proposed and analyzed in terms of intercept probability. It is proved that the MSRRS and MSCRS schemes have the same secrecy performance. Two parameters called average number gain and average cost gain are proposed to show the performance of the proposed relay selection schemes. Numerical results demonstrated that with 10 relay nodes, the proposed relay selection schemes can achieve, respectively, 3.7 dB and 1.9 dB’s improvements in terms of the reduced intercept probability and the enhanced secrecy capacity compared to the traditional round-robin scheme.     

HVE-mobicast: a hierarchical-variant-egg-based mobicast routing protocol for wireless sensornets

In this paper, we propose a new mobicast routing protocol, called the HVE-mobicast (hierarchical-variant-egg-based mobicast) routing protocol, in wireless sensor networks (WSNs). Existing protocols for a spatiotemporal variant of the multicast protocol called a “mobicast” were designed to support a forwarding zone that moves at a constant velocity, \(\stackrel{\rightarrow}{v}\), through sensornets. The spatiotemporal characteristic of a mobicast is to forward a mobicast message to all sensor nodes that are present at time t in some geographic zone (called the forwarding zone) Z, where both the location and shape of the forwarding zone are a function of time over some interval (t _start ,t _end ). Mobicast routing protocol aims to provide reliable and just-in-time message delivery for a mobile sink node. To consider the mobile entity with the different moving speed, a new mobicast routing protocol is investigated in this work by utilizing the cluster-based approach. The message delivery of nodes in the forwarding zone of the HVE-mobicast routing protocol is transmitted by two phases; cluster-to-cluster and cluster-to-node phases. In the cluster-to-cluster phase, the cluster-head and relay nodes are distributively notified to wake them up. In the cluster-to-node phase, all member nodes are then notified to wake up by cluster-head nodes according to the estimated arrival time of the delivery zone. The key contribution of the HVE-mobicast routing protocol is that it is more power efficient than existing mobicast routing protocols, especially by considering different moving speeds and directions. Finally, simulation results illustrate performance enhancements in message overhead, power consumption, needlessly woken-up nodes, and successful woken-up ratio, compared to existing mobicast routing protocols.     

Performance assessment of multicast node placement for multicast routing in WDM networks with sparse light splitting

This article examines all-optical multicast routing for wavelength-routed optical networks with sparse Multicast Capable (MC) nodes in two phases. The first phase is MC node placement and use of a simple and straightforward Maximum Path Count First (MPCF) algorithm to obtain candidates for MC nodes. The second phase is multicast routing with MC-based schemes that minimizes the number of wavelength channels with minimum transmission delay as required by a given multicast session, in that a light-tree is first constructed to connect MC nodes in a multicast group by using two algorithms, namely, the Pre-computing Minimum Cost (PMC) tree algorithm and the Pre-computing Shortest Path (PSP) tree algorithm. System performance of the proposed MPCF MC node placement algorithm is compared with that of the Normalized Cuts (NC) MC node placement algorithm for both PMC and PSP multicast routing. Furthermore, simulation results compare PMC and PSP multicast routing based on MPCF and NC node placement with Re-route-to-Source (RTS), Re-route-to-Any (RTA), Member-First (MF), and Member-Only (MO) multicast routing based on a light forest for a given multicast session in terms of average number of wavelengths needed, average blocking probability, and mean maximum transmission delay.

On routing with guaranteed delivery in three-dimensional ad hoc wireless networks

We study the problem of routing in three-dimensional ad hoc networks. We are interested in routing algorithms that guarantee delivery and are k-local, i.e., each intermediate node v’s routing decision only depends on knowledge of the labels of the source and destination nodes, of the subgraph induced by nodes within distance k of v, and of the neighbour of v from which the message was received. We model a three-dimensional ad hoc network by a unit ball graph, where nodes are points in three-dimensional space, and for each node v, there is an edge between v and every node u contained in the unit-radius ball centred at v. The question of whether there is a simple local routing algorithm that guarantees delivery in unit ball graphs has been open for some time. In this paper, we answer this question in the negative: we show that for any fixed k, there can be no k-local routing algorithm that guarantees delivery on all unit ball graphs. This result is in contrast with the two-dimensional case, where 1-local routing algorithms that guarantee delivery are known. Specifically, we show that guaranteed delivery is possible if the nodes of the unit ball graph are contained in a slab of thickness \(1/\sqrt{2}.\) However, there is no k-local routing algorithm that guarantees delivery for the class of unit ball graphs contained in thicker slabs, i.e., slabs of thickness \(1/\sqrt{2} + \epsilon\) for some \( \epsilon > 0.\) The algorithm for routing in thin slabs derives from a transformation of unit ball graphs contained in thin slabs into quasi unit disc graphs, which yields a 2-local routing algorithm. We also show several results that further elaborate on the relationship between these two classes of graphs.     

Quantum Gates with Spin States in Continuous Microwave Field

The physical basis of the method of implementing quantum logical operations in a continuous microwave field in a system of two electrons with different g-factors and a constant exchange interaction is developed. A small variable additive ΔB(t) to the magnetic field is proposed as a control action. It is obtained that a simple functional dependence ΔB(t), based on harmonic functions, allows us to perform elementary quantum logical operations and their sequences. This method is adapted to the experimental conditions.     

Throughput and delay analysis for hybrid radio-frequency and free-space-optical (RF/FSO) networks

In this paper the per-node throughput and end-to-end delay of randomly deployed (i.e. ad-hoc) hybrid radio frequency - free space optics (RF/FSO) networks are studied. The hybrid RF/FSO network consists of an RF ad hoc network of n nodes, f(n) of them, termed ‘super nodes’, are equipped with an additional FSO transceiver with transmission range s(n). Every RF and FSO transceiver is able to transmit at a maximum data rate of W ₁ and W ₂ bits/sec, respectively. An upper bound on the per node throughput capacity is derived. In order to prove that this upper bound is achievable, a hybrid routing scheme is designed whereby the data traffic is divided into two classes and assigned different forwarding strategies. The capacity improvement with the support of FSO nodes is evaluated and compared against the corresponding results for pure RF wireless networks. Under optimal throughput scaling, the scaling of average end-to-end delay is derived. A significant gain in throughput capacity and a notable reduction in delay will be achieved if \(f(n) = \Upomega\left(\frac{1}{s(n)}\sqrt{\frac{n}{\log n}}\cdot \frac{W_1}{W_2} \right)\). Furthermore, it is found that for fixed W ₁, f(n) and n where f(n) < n, there is no capacity incentive to increase the FSO data rate beyond a critical value. In addition, both throughput and delay can achieve linear scaling by properly adjusting the FSO transmission range and the number of FSO nodes.     

Leakage-Resilient Cryptography from Minimal Assumptions

We present new constructions of leakage-resilient cryptosystems, which remain provably secure even if the attacker learns some arbitrary partial information about their internal secret-key. For any polynomial \(\ell \), we can instantiate these schemes so as to tolerate up to \(\ell \) bits of leakage. While there has been much prior work constructing such leakage-resilient cryptosystems under concrete number-theoretic and algebraic assumptions, we present the first schemes under general and minimal assumptions. In particular, we construct:

• Leakage-resilient public-key encryption from any standard public-key encryption.
• Leakage-resilient weak pseudorandom functions, symmetric-key encryption, and message-authentication codes from any one-way function.

These are the first constructions of leakage-resilient symmetric-key primitives that do not rely on public-key assumptions. We also get the first constructions of leakage-resilient public-key encryption from “search assumptions,” such as the hardness of factoring or CDH. Although our schemes can tolerate arbitrarily large amounts of leakage, the tolerated rate of leakage (defined as the ratio of leakage amount to key size) is rather poor in comparison with prior results under specific assumptions. As a building block of independent interest, we study a notion of weak hash-proof systems in the public-key and symmetric-key settings. While these inherit some of the interesting security properties of standard hash-proof systems, we can instantiate them under general assumptions.

     

MDP based link scheduling in wireless networks to maximize the reliability

This paper considers wireless networks where communication links are unstable and link interference is a challenge to design high performance scheduling algorithms. Wireless links are time varying and are modeled by Markov stochastic processes. The problem of designing an optimal link scheduling algorithm to maximize the expected reliability of the network is formulated into a Markov Decision Process first. The optimal solution can be obtained by the finite backward induction algorithm. However, the time complexity is very high. Thus, we develop an approximate link scheduling algorithm with an approximate ratio of \(2(N - 1)(r_{M}\Delta - r_{m} \delta ),\) where N is the number of decision epochs, r _M is the maximum link reliability, r _m is the minimum link reliability, Δ is the number of links in the largest maximal independent set and δ is the number of links in the smallest maximal independent set. Simulations are conducted in different scenarios under different network topologies.     

Address Remapping Techniques for Enhancing Fabrication Yield of Embedded Memories

Error correction code (ECC) and built-in self-repair (BISR) techniques have been widely used for improving the yield and reliability of embedded memories. The targets of these two schemes are transient faults and hard faults, respectively. Recently, ECC is also considered as a promising solution for correcting hard error to further enhance the fabrication yield of memories. However, if the number of faulty bits within a codeword is greater than the protection capability of the adopted ECC scheme, the protection will become void. In order to cure this drawback, efficient logical to physical address remapping techniques are proposed in this paper. The goal is to reconstruct the constituent cells of codewords such that faulty cells can be evenly distributed into different codewords. A heuristic algorithm suitable for built-in implementation is presented for address remapping analysis. The corresponding built-in remapping analysis circuit is then derived. It can be easily integrated into the conventional built-in self-repair (BISR) module. A simulator is developed to evaluate the hardware overhead and repair rate. According to experimental results, the repair rate can be improved significantly with negligible hardware overhead.     

A System for Logical Design of Custom CMOS VLSI Functional Blocks with Reduced Power Consumption

We describe a CMOSLD system to automate the design of irregular logic circuits of CMOS library elements. The main criteria of circuits optimization are the area and the power consumption. This system is integrated with software packages Questa Sim, LeonardoSpectrum, and Accusim II (Mentor Graphics). This makes it possible to perform efficiently logical simulation, synthesis, resynthesis and estimation of energy consumption based on logical and circuit simulation.     

Weighted dominating set based routing for ad hoc communications in emergency and rescue scenarios

Disasters create emergency situations and the services provided must be coordinated quickly via a communication network. Mobile adhoc networks (MANETs) are suited for ubiquitous communication during emergency rescue operations, since they do not rely on infrastructure. The route discovery process of on-demand routing protocols consumes too much bandwidth due to high routing overhead. Frequent route changes also results in frequent route computation process. Energy efficiency, quick response time, and scalability are equally important for routing in emergency MANETs. In this paper, we propose an energy efficient reactive protocol named Weighted-CDSR for routing in such situations. This protocol selects a subset of network nodes named Maximum Weighted Minimum Connected Dominating Set (MWMCDS) based on weight, which consists of link stability, mobility and energy. The MWMCDS provides the overall network control and data forwarding support. In this protocol, for every two nodes u and v in the network there exists a path between u and v such that all intermediate nodes belong to MWMCDS. Incorporating route stability into routing reduces the frequency of route failures and sustains network operations over an extended period of time. With fewer nodes providing overall network control and data forwarding support, the proposed protocol creates less interference and consumes less energy. The simulation results show that the proposed protocol is superior to other protocols in terms of packet delivery ratio, control message overhead, transmission delay and energy consumption.     

Link scheduling for throughput maximization in multihop wireless networks under physical interference

We consider the problem of link scheduling for throughput maximization in multihop wireless networks. Majority of previous methods are restricted to graph-based interference models. In this paper we study the link scheduling problem using a more realistic physical interference model. Through some key observations about this model, we develop efficient link scheduling algorithms by exploiting the intrinsic connections between the physical interference model and the graph-based interference model. For one variant of the problem where each node can dynamically adjust its transmission power, we design a scheduling method with O(g(E)) approximation to the optimal throughput capacity where g(E) denotes length diversity. For the other variant where each node has a fixed but possible different transmission powers for different nodes, we design a method with O(g(E))-approximation ratio when the transmission powers of all nodes are within a constant factor of each other, and in general with an approximation ratio of \(O(g(E)\log \rho )\) where \(\log \rho\) is power diversity. We further prove that our algorithm for fixed transmission power case retains O(g(E)) approximation for any length-monotone, sub-linear fixed power setting. Furthermore, all these approximation factors are independent of network size .     

PAPR reduction in CO-OFDM systems using IPTS and modified clipping and filtering

Aiming at the problem of the peak to average power ratio (PAPR) in coherent optical orthogonal frequency division multiplexing (CO-OFDM), a hybrid PAPR reduction technique of the CO-OFDM system by combining iterative partial transmit sequence (IPTS) scheme with modified clipping and filtering (MCF) is proposed. The simulation results show that at the complementary cumulative distribution function (CCDF) of 10^-4, the PAPR of proposed scheme is optimized by 1.86 dB and 2.13 dB compared with those of IPTS and CF schemes, respectively. Meanwhile, when the bit error rate (BER) is 10^-3, the optical signal to noise ratio (OSNR) are optimized by 1.57 dB and 0.66 dB compared with those of CF and IPTS-CF schemes, respectively.     

Influence of overhead on LTE downlink performance: a comprehensive model

Overhead resource elements (REs) in Long Term Evolution (LTE) networks are used for some control, signaling and synchronization tasks at both the Physical level and Media Access Control sub-level. Accurately computing all the overhead REs is necessary to achieve an efficient system design, which is difficult because LTE is a complex standard that contains a large number of implementation flexibilities and system configurations. The number of such REs depends on both the system configurations and services demanded. Aiming at exploring the influence of overhead on LTE downlink performance, we first parametrize each system configuration—including parameters corresponding to enhancement techniques such as Adaptive Modulation and Coding and Multi-Antenna Transmissions techniques—and those of the resource allocation mechanisms (which depend on users’ services). Second, using such parametrization, we model all overheads for synchronization, controlling and signaling operations in LTE Physical Downlink Shared/Control Channels. This allows for dynamically computing the useful REs (by subtracting the overhead REs from the total ones), both per Transmission Time Interval (TTI) and per frame (and hence, the corresponding bit rates). Our data rate-based performance model is able to accurately compute: (1) the real, exact system data rate or “throughput” (instead of approximations); and (2) the maximum number of simultaneous multi-service users per TTI that is able to support (called here “capacity”). Aiming at understanding the impact of each overhead mechanism, we have carried out a variety of simulations, including different service provision scenarios, such as multi-user with multi-application. The simulation results prove our starting hypothesis that the influence of overhead on LTE performance should not be neglected. The parametrized and dynamic model quantifies to what extent throughput and capacity are modified by overhead—under a combination of system configurations and services, and may provide these performance metrics, throughput and capacity, as inputs to planning, dimensioning and optimization specialized tools.     

Computationally Efficient Motion Estimation Algorithm for HEVC

In this paper, we present a novel computationally efficient motion estimation (ME) algorithm for high-efficiency video coding (HEVC). The proposed algorithm searches in the hexagonal pattern with a fixed number of search points at each grid. It utilizes the correlation between contiguous pixels within the frame. In order to reduce the computational complexity, the proposed algorithm utilizes pixel truncation, adaptive search range, sub-sampling and avoids some of the asymmetrical prediction unit techniques. Simulation results are obtained by using the reference software HM (e n c o d e r_l o w d e l a y_P_m a i n and e n c o d e r_r a n d o m a c c e s s_m a i n profile) and shows 55.49% improvement on search points with approximately the same PSNR and around 1% increment in bit rate as compared to the Test Zonal Search (TZS) ME algorithm. By utilizing the proposed algorithm, the BD-PSNR loss for the video sequences like B a s k e t b a l l P a s s_416 × 240@50 and J o h n n y_1280 × 720@60 is 0.0804 dB and 0.0392 dB respectively as compared to the HM reference software with the e n c o d e r_l o w d e l a y_P_m a i n profile.     

Signature Schemes Secure Against Hard-to-Invert Leakage

Side-channel attacks allow the adversary to gain partial knowledge of the secret key when cryptographic protocols are implemented in real-world hardware. The goal of leakage resilient cryptography is to design cryptosystems that withstand such attacks. In the auxiliary input model, an adversary is allowed to see a computationally hard-to-invert function of the secret key. The auxiliary input model weakens the bounded leakage assumption commonly made in leakage resilient cryptography as the hard-to-invert function may information-theoretically reveal the entire secret key. In this work, we propose the first constructions of digital signature schemes that are secure in the auxiliary input model. Our main contribution is a digital signature scheme that is secure against chosen message attacks when given any exponentially hard-to-invert function of the secret key. As a second contribution, we construct a signature scheme that achieves security for random messages assuming that the adversary is given a polynomial-time hard-to-invert function (where both the challenge as well as the signatures seen prior to that are computed on random messages). Here, polynomial hardness is required even when given the entire public key. We further show that such signature schemes readily give us auxiliary input secure identification schemes.     

Multi-layer based multi-path routing algorithm for maximizing spectrum availability

Last 2 decades have witnessed the spectrum resources scarcity which is caused by wireless networks’ ubiquitous applications. To utilize the rare spectrum resources more efficiently, Cognitive Radio (CR) technology has been developed as a promising scheme. However, in CR networks, a novel NP-Hard disjoint multi-path routing problem has been encountered due to the Primary Users’ (PUs’) random movements. To settle this problem, we present a Spectrum History Matrix mechanism to define long-term spectrum sensing information on time-spectrum level such that spectrum availability and communication efficiency can be quantized in CR networks. To lessen the possibility for an active PU to interrupt all paths simultaneously, a sub-optimal Multi-layer based Multi-path Routing Algorithm (MMRA) is provided to determine how to route multiple paths which are not under the same PUs’ interference ranges. Through theoretical and simulation analyses, MMRA can not only settle the disjoint multi-path routing problem in polynomial time complexity, but also maximize communication efficiency.