We will review some of the major results in random graphs and some of the more challenging open problems. We will cover algorithmic and structural questions. We will touch on newer models, including those related to the WWW.

Random graphs

It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >

On the capacity of a cellular CDMA system

The objective of this paper is to give a comprehensive introduction to applied cryptography with an engineer or computer scientist in mind. The emphasis is on the knowledge needed to create practical systems which supports integrity, confidentiality, or authenticity. Topics covered includes an introduction to the concepts in cryptography, attacks against cryptographic systems, key use and handling, random bit generation, encryption modes, and message authentication codes. Recommendations on algorithms and further reading is given in the end of the paper. This paper should make the reader able to build, understand and evaluate system descriptions and designs based on the cryptographic components described in the paper.

[서평]「Applied Cryptography」

IoT security: Review, blockchain solutions, and open challenges

The problem of error control and concealment in video communication is becoming increasingly important because of the growing interest in video delivery over unreliable channels such as wireless networks and the Internet. This paper reviews the techniques that have been developed for error control and concealment. These techniques are described in three categories according to the roles that the encoder and decoder play in the underlying approaches. Forward error concealment includes methods that add redundancy at the source end to enhance error resilience of the coded bit streams. Error concealment by postprocessing refers to operations at the decoder to recover the damaged areas based on characteristics of image and video signals. Last, interactive error concealment covers techniques that are dependent on a dialogue between the source and destination. Both current research activities and practice in international standards are covered.

/pdf/error-control-and-concealment-for-video-communication-a-3tm7c48xjc.pdf

Error control and concealment for video communication: a review

Step counting based dead-reckoning has been widely accepted as a cheap and effective solution for indoor pedestrian tracking using hand held device equipped with motion sensors. To calibrate the accumulating error in a dead-reckoning tracking system, extra techniques are always fused to form a hybrid system. Currently various particle filter based map filtering algorithms have been proposed in the literature. However, more improvement can be achieved by using map information. In this paper, a map matching involved step counting algorithm is proposed. It is shown that by applying map matching in an indoor environment with corridors, not only can the estimated location be calibrated, but also the estimated sensor's orientation and the walking direction, which reduces the error in the ensuing location update process. The computational complexity is also less than the particle filter. Experimental results show that map matching algorithm returns more accurate results than the particle filter given the same map information. Further experiments indicate that when incomplete map information is given, the particle filter is much easier in returning a drifted path compared to map matching. This indicates that less map information is required by map matching to achieve a robust performance. This reduced reliance on accurate map information implies less labour cost and error in map maintenance.

An indoor dead-reckoning algorithm with map matching

Privacy-preserving routing protocols in wireless networks frequently utilize additional artificial traffic to hide the identities of communicating source-destination pairs. Usually, the addition of artificial traffic is done heuristically with no guarantees that the transmission cost, latency, and so on, are optimized in every network topology. In this paper, we explicitly examine the privacy-utility tradeoff problem for wireless networks and develop a novel privacy-preserving routing algorithm called optimal privacy enhancing routing algorithm (OPERA). OPERA uses a statistical decision-making framework to optimize the privacy of the routing protocol given a utility (or cost) constraint. We consider global adversaries with both lossless and lossy observations that use the Bayesian maximum-a-posteriori (MAP) estimation strategy. We formulate the privacy-utility tradeoff problem as a linear program, which can be efficiently solved. Our simulation results demonstrate that OPERA reduces the adversary’s detection probability by up to 50% compared to the random Uniform and Greedy heuristics, and up to five times compared to a baseline scheme. In addition, OPERA also outperforms the conventional information-theoretic mutual information approach.

https://oar.a-star.edu.sg/jspui/bitstream/123456789/2131/1/2017-TIFS-OPERA-KLPNW-Preprint.pdf

Optimal Privacy-Preserving Probabilistic Routing for Wireless Networks

The author studies the performance of a high capacity metropolitan microcellular radio network using computer simulation Packet reservation multiple access carriers are dynamically assigned or released depending on current teletraffic loading conditions Significant performance improvements are obtained using a 2-stage costing strategy which attempts to balance call blocking probabilities against packet dropping rate, thereby leading to more efficient utilisation of channel resources The author achieves 40 to 50% improvements over a fixed allocation scheme in terms of the blocking probability performance, by soft assigning carriers to the microcells and performing a 2-stage dynamic carrier allocation procedure based on a simple costing algorithm which attempts to pack co-carrier cells as closely as possible >

https://ieeexplore.ieee.org/iel1/25/6590/00260775.pdf

Dynamic allocation of packet reservation multiple access carriers

Dynamic spectrum access has gained traction in wireless sensor networks (WSNs) because of the scarcity in spectrum caused by the proliferation of wireless devices and services, and it provides spectrum efficient communication for the WSNs. However, the communication between nodes in a cognitive radio sensor network (CRSN) is affected by the transmission power, fading, and interference with licensed users, and these factors hinder the data transmission between the energy constrained cognitive radio sensor nodes. Therefore, there is a need for an adaptive energy-efficient optimization scheme which takes into account the varying environment conditions. Since packet length plays a pivotal role in determining the performance of the network, packet size adaptation that is aware of the channel characteristics may bring about performance improvement. Furthermore, existing packet size optimization or channel selection schemes devised for WSNs and CR networks are not appropriate for the CRSN framework. In this paper, we devise a dynamic packet size optimization and channel selection scheme (DyPSOCS) for CRSNs. We employ a constrained Markov decision process (CMDP) to solve the optimization problem with quality of service (QoS) constraints. Simulation results show improvement in QoS performance as well as energy efficiency when compared to other schemes.

Dynamic Packet Size Optimization and Channel Selection for Cognitive Radio Sensor Networks

The platoon control for vehicles can efficiently reduce traffic pressure. Current control schemes are able to achieve stable platoon control, but cannot guarantee collision avoidance, connectivity preservation and convergence time at the same time. In this paper, we propose a novel control scheme that can simultaneously guarantee the safe distance and communication connectivity, which is called flexible safe distance constraint, and also can guarantee the specified convergence time. A dynamic gain based distributed control law is first designed for the vehicle with single-integral model. Using the prescribed transient and steady-state performance control approach, the flexible safe distance constraint can be satisfied. Using the time transformation method and Lyapunov stability theory, the closed-loop systems under the proposed protocols can achieve stable platoon within the specified time. Compared with some existing results, the novelty of this work is that the proposed approaches allow a vehicle to converge with the platoon within any preset time without dependence on the initial conditions or system parameters. Another contribution of this work is to propose specified-time platoon control protocols for the vehicle with double-integral model under a flexible safe distance constraint. Furthermore, in order to get closer to the actual system, the controller is extended to the triple-integral system, and some special cases are also discussed. Finally, some simulations are presented to show the effectiveness of the proposed protocols.

Wai-Choong Wong

Papers

An indoor dead-reckoning algorithm with map matching

Optimal Privacy-Preserving Probabilistic Routing for Wireless Networks

Dynamic allocation of packet reservation multiple access carriers

Dynamic Packet Size Optimization and Channel Selection for Cognitive Radio Sensor Networks

Specified-Time Vehicular Platoon Control With Flexible Safe Distance Constraint