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

This paper describes and analyses a new priority CSMA/CD protocol for multichannel local area networks. In this scheme, low priority messages can be transmitted by using the CSMA/CD protocol only when the number of idle channels exceeds a certain value. Following a general description of the proposed priority protocol, this paper analyses the protocol by first formulating the various state transition probabilities of the network. The delay and throughput characteristics of the various priority messages are then calculated and presented. It is found that the performance of this simple scheme is comparable to the priority schemes studies in Reference 8 for CSMA/CD networks. Also, in order not to starve off low priority stations, the largest number of idle channels when the transmission of low priority packets becomes inhibited should not be more than about one third of the total number of channels.

Simple priority scheme for multichannel CSMA/CD local area networks

We examine various strategies to provide low delay, high quality digital speech communications in a high capacity wireless network. Multiple access schemes based an time-division and packet reservation are compared in terms of their statistical multiplexing capabilities, sensitivity to speech packet dropping, delay, robustness to lossy packet environments, and overhead efficiency. In particular, we propose a low-delay multiple access scheme, called Shared Time-Division Duplexing (STDD), which allows both the uplink and downlink traffic to share a common channel, thereby achieving high statistical multiplexing gain even with a low population of simultaneous conversations. Typically, with a total capacity of 1 MBaud, 2 ms frame and 8 kBaud speech rate, low delay STDD is able to support 48 pairs of users compared to 38, 35 and 16 for TDMA with speech activity detection, basic TDMA and PRMA respectively. >

http://ieeexplore.ieee.org/iel2/1047/7666/00318349.pdf

Low delay, high quality wireless digital speech communications by shared time division duplexing

To increase the capacity of blank and burst transmission of control information in cellular communication systems, the authors explore the application of a speech segment reconstruction technique. The transmitter selects a blanking interval on the basis of a segment classification measure, while the receiver replaces the missing speech with an estimate based on previously received speech. Using this approach, approximately 3.2 data bursts per second, each lasting 16 ms may be sent without degrading speech quality.

Blank and burst transmission of data over active speech channels

Inter-user interference deteriorates reliable communication in body sensor networks (BSNs) when multiple BSNs are transmitting simultaneously in close proximity to each other. Stochastic geometry provides a natural way of modeling the placement of interferers, by averaging over all potential geometrical realizations for the interferers. This paper presents a stochastic geometry analysis of inter-user interference in IEEE 802.15.6 BSNs. The analysis evaluates the performance of BSNs in terms of outage probability and spatial throughput. The effects of medium access control (MAC) design in IEEE 802.15.6 are considered where both contention-free and contention-based MAC operations co-exist in the BSN deployment area. Based on the analysis, the interference detection range is optimized to achieve the maximum spatial throughput while the reliable transmission requirement is met. Moreover, insights are provided on the design of MAC for BSNs depending on the specific BSN applications.

A stochastic geometry analysis of inter-user interference in IEEE 802.15.6 body sensor networks

This paper addresses building networks that emphasizes on user-centric human computer interaction and context awareness. To achieve this user-centric intelligent network goal, we propose to explicitly take the end-user into account by defining a new layer called the User Layer above the traditional application layer. By exposing some lower layer information to the end-user, the new User Layer establishes a feedback loop between the end-user and the underlying network infrastructure, empowering the end-user to control and influence network performance based on his own behavior and preferences. A cross-layer design approach using a shared database between the different lower layers is adopted. To illustrate the User Layer in action, we present an exemplary implementation of the User Layer, which can dynamically allocate network resources by leveraging on the TCP flow control mechanism. We evaluated network performance via simulation and show that such a design improves the user perceived quality of service (QoS).

Wai-Choong Wong

Papers

Simple priority scheme for multichannel CSMA/CD local area networks

Low delay, high quality wireless digital speech communications by shared time division duplexing

Blank and burst transmission of data over active speech channels

A stochastic geometry analysis of inter-user interference in IEEE 802.15.6 body sensor networks

Intelligent network design: User Layer architecture and its application