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 presents an improved scheme to maximize system throughput through joint rate and power adaptation with perfect channel information in a multicode CDMA system. By specifying suitable boundary conditions, the search range can be narrowed down thereby significantly improving search complexity.

An improved code rate search scheme for adaptive multicode CDMA

A compensation based indoor localization method is proposed for localizing mobile stations utilizing Received Signal Strength Indicator (RSSI). The method consists of two subsystems, a data collection subsystem and a decision making subsystem based on log-distance path loss model. The main contribution of the method proposed is that localization errors caused by multipath fading are estimated and compensated in a vector space. The accuracy of traditional log-distance path loss model based localization method is improved. A new measure of multipath fading is proposed and analysed in comparison to existing measures. Experiments are conducted and results show that an average error of 2.98m and a 31% improvement compared to the traditional log-distance path loss model based algorithms can be achieved.

COMVELOC: A Compensation Vector-Based Indoor Localization System in WIFI Environments

Context-aware applications generally need to retrieve various kinds of dynamic context data from a large number of context sources. A middleware managing context sources must provide an efficient context lookup mechanism to ease application development. In this paper, we categorize the context sources as operating spaces and propose semantic peer-to-peer overlays over these spaces to accelerate dynamic context lookup in a context-aware middleware. Our proposed overlay structure is specially designed to deal with dynamic sensory context such as a person’s location and temperature that are frequently changing and difficult to be promptly retrieved using traditional peer-to-peer protocols. Our overlay and indexing method has a low maintenance overhead. Measurement results show that the proposed overlay achieves a good response time and accuracy for context lookup as well as requires low maintenance overhead. (Less)

Semantic P2P Overlay for Dynamic Context Lookup

This paper presents a novel hierarchical optimization handoff algorithm (HOHA) which has superior performance over the conventional 1- and 2-threshold handoff algorithms. The proposed algorithm scans through layers of call handoff options and determines the best candidate based on a heuristic that synchronises reciprocal handoffs in adjacent cells and maximises the spare channel capacity in the destination cells. Computer simulation results show that under a unity normalised load condition, the HOHA achieves a gain of about 55% and 11% in the probability of handoff failure as compared to the 1- and 2-threshold handoff algorithms, respectively. In addition, the total effective load carried is also improved by about 13% and 4%, respectively.

Hierarchical optimization of microcellular call handoffs

The authors study a hybrid approach in determining the excitation vector in a low-delay code excited linear predictive coder. By a judicious division of the composite excitation vector into long-term and short-term components, and the use of switched quantisation, substantial improvement in coding quality is obtained. In addition, the use of an adaptive postfilter which incorporates both the envelope and fine spectral structure of the input signal results in improved recovered speech quality.

Wai-Choong Wong

Papers

An improved code rate search scheme for adaptive multicode CDMA

COMVELOC: A Compensation Vector-Based Indoor Localization System in WIFI Environments

Semantic P2P Overlay for Dynamic Context Lookup

Hierarchical optimization of microcellular call handoffs

A low-delay hybrid vector excitation linear predictive speech coding scheme