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

The authors describe a hybrid image coding scheme called the classified hybrid image coder (CHIC). CHIC combines the classified vector quantization (CVQ) and the discrete cosine transform (DCT) coding schemes to achieve a better performance than would be possible if they were to be used separately. The image is subdivided into 16*16 pixel blocks (vectors) and transformed using DCT. Each vector is classified into an edge vector and a shade vector. Classification is based on the distribution and value of the DCT coefficients in each vector. Shade vectors are coded using CVQ. Edge vectors are further classified according to their edge strengths. In each of these classes, the coefficients are quantized and then coded with an adaptive arithmetic coder (AAC). The performance of the AAC is further improved by further classifying the DCT coefficients into different groups, based on their different frequency ranges. The AAC uses a set of training images to generate the initial histogram tables. >

https://ieeexplore.ieee.org/iel5/555/4470/00176360.pdf

A hybrid image coding scheme using CVQ and DCT

Network coding techniques are usually applied upon network-layer protocols to improve throughput in wireless networks. In scenarios with multiple unicast sessions, fairness is also an important factor. Therefore, a network coding-aware packet-scheduling algorithm is required. A packet-scheduling algorithm determines which packet to send next from a node’s packet backlog. Existing protocols mostly employ a basic round-robin scheduling algorithm to give “equal” opportunities to different packet flows. In fact, this “equal”-opportunity scheduling is neither fair, nor efficient. This paper intends to accentuate the importance of a coding-aware scheduling scheme. With a good scheduling scheme, we can gain more control over the per-flow throughput and fairness. Specifically, we first formulate a static scheduling problem and propose an algorithm to find the optimal scheduling scheme. We then extend the technique to a dynamic setting and, later, to practical routing protocols. Results show that the algorithm is comparatively scalable, and it can improve the throughput gain when the network is not severely saturated. The fairness among flows is drastically improved as a result of this scheduling scheme.

https://www.mdpi.com/2224-2708/3/4/274/pdf

Towards a Fair and Efficient Packet Scheduling Scheme in Inter-Flow Network Coding

Traffic patterns for mobile communication networks are well known and accurately modelled. However, traffic generation behaviors for sensor networks are often lacking in research and not well understood. We investigate one class of sensor networks for a target tracking application using realistic sensing models and a general target motion model. Results show that the probability of arrivals for a tracking sensor network fits a quadratic curve.

Sensor Traffic Patterns in Target Tracking Networks

When Ambient Intelligence meets the Internet: User Module framework and its applications

The human body displacement estimation in different gait patterns using wearable sensors is extremely challenging due to lack of external references. In this paper, we present a novel algorithm to estimate the Center of Mass (CoM) displacement of human body during walking, running and hopping using 7 body-worn Sensor Measurement Units (SMUs). The lower body posture and feet displacements are firstly estimated by a complementary Kalman filter (CKF) which compensates the orientation, velocity and position errors of the Inertial Navigation system (INS) solutions through its error state vector. The CoM displacement can then be acquired by further fusion of the lower body posture and feet locations based on the linked biomechanical model. The experimental results have shown that our method can accurately capture human motion including orientation and locomotion for these three different gait patterns with regard to the optical motion tracker.

/pdf/displacement-estimation-for-different-gait-patterns-in-micro-t46wft0xbp.pdf

Wai-Choong Wong

Papers

A hybrid image coding scheme using CVQ and DCT

Towards a Fair and Efficient Packet Scheduling Scheme in Inter-Flow Network Coding

Sensor Traffic Patterns in Target Tracking Networks

When Ambient Intelligence meets the Internet: User Module framework and its applications

Displacement estimation for different gait patterns in micro-sensor motion capture