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

Traditional wireless routing protocols do not take into account the possibility of network coding. A series of routing protocols are specifically designed to exploit the power of network coding. However, they mostly focus only on initial route set-up but neglect further maintenance. New flows coming in and old flows dying out can greatly impact the amount of network coding utilized. In this paper, we propose Self-recommendation Coding-Aware Routing (SCAR), to account for these changes in network. With intermediate nodes sensing the changes, they can send self recommendations to source nodes, triggering a route-change procedure. In route-change procedure, adjustments are applied to the route metrics so that the new recommended route can be fairly weighed without bias. Simulation results show that our protocol can achieve higher throughput compared to other static coding-aware routing protocols. This is especially true in topologies where coding opportunity is scarce, or multiple-packet coding is possible. It is also shown that SCAR is more robust against changes in flow arrival sequence.

SCAR: A dynamic Coding-Aware Routing protocol

This letter proposes a 4-kb/s multimode code-excited linear prediction (CELP) coder with pitch synchronous extended excitation. Three modes are used for the short-term excitation, namely algebraic, extended, or stochastic excitations, together with an adaptive codebook for the long-term excitation. Comparisons with the FS-1016 and ITU-T G.723.1 coders show a performance level between these standards.

Pitch synchronous extended excitation in multimode CELP

This paper shows how Rate-Distortion-Authentication (R-D-A) optimized streaming may be performed with the Generalized Butterfly Graph (GBG) stream authentication method. R-D-A streaming is designed to compute an optimized transmission policy by accounting for both coding and authentication dependencies, and GBG is designed to protect the authenticity of a media stream. The GBG graph is better suited for streaming than the original Butterfly graph since it is highly flexible and can support an arbitrary number of packets and arbitrary overhead. However, the dependency chains within the GBG graph are much longer and are tangled with each other-making it very difficult to quantify the dependencies necessary to perform R-D-A streaming. We propose a method to estimate the authentication dependencies, which is then used by the R- D-A technique to compute the optimized transmission policy.

Rate-Distortion-Authentication optimized streaming with Generalized Butterfly Graph authentication

Data fusion techniques are a promising solution to increase the lifetime of wireless sensor networks, because it allows the reduction of data that needs to be transmitted back to the network sink. However, data fusion schemes are vulnerable to Byzantine attacks. Specifically, a Byzantine (dishonest) data fusion node can send falsified fusion data to mislead the sink. Hence, many witness-based schemes have been proposed to rectify such vulnerabilities by making use of additional “witness” nodes to monitor the main fusion node. The witnesses then submit a “vote” to the sink which decides whether the received data is valid. This paper proposes a dynamic witness concept together with distributed forwarder node monitoring to validate the transmitted fusion data. The distributed monitoring system detects any modification of the fusion data in transit while a randomly chosen witness is used to monitor the fusion node. We show through analysis and simulation that our scheme offers better resilience against Byzantine nodes and improved energy efficiency compared to existing witness-based approaches. More importantly, we reduce the overheads and limitations of existing witness-based schemes to make such schemes more practical.

Wai-Choong Wong

Papers

SCAR: A dynamic Coding-Aware Routing protocol

Pitch synchronous extended excitation in multimode CELP

Rate-Distortion-Authentication optimized streaming with Generalized Butterfly Graph authentication

Mitigating byzantine attacks in data fusion process for wireless sensor networks using witnesses

Dual wakeup design for wireless sensor networks