Mobile Audiovisual Terminal: System Design and Subjective Testing in DECT and UMTS networks

It is anticipated that there will shortly be a requirement for multimedia terminals that operate via mobile communications systems. This paper presents a functional specification for such a terminal operating at 32 kb/s in a digital European cordless telecommunications (DECT) and universal mobile telecommunications system (UMTS) radio network. A terminal has been built, based on a PC with digital signal processor (DSP) boards for audio and video coding and decoding. Speech coding is by a phonetically driven code-excited linear prediction (CELP) speech coder and video coding by a block-oriented hybrid discrete cosine transform (DCT) coder. Separate channel coding is provided for the audio and video data. The paper describes the techniques used for audio and video coding, channel coding, and synchronization. Methods of subjective testing in a DECT network and in a UMTS network are also described. These consisted of subjective tests of first impressions of the mobile audio–visual terminal (MAVT) quality, interactive tests, and the completion of an exit questionnaire. The test results showed that the quality of the audio was sufficiently good for comprehension and the video was sufficiently good for following and repeating simple mechanical tasks. However, the quality of the MAVT was not good enough for general use where high-quality audio and video was needed, especially when transmission was in a noisy radio environment

Evaluating the Impacts of Information and Communication Technology (ICT) on Trade in Fruit and Vegetables within the APEC Countries

The global food marketing network is being constantly reshaped, providing opportunities and challenges to the use of information and communication technology (ICT) to develop international trade in food products. ICT is likely to be especially important for food products such as fresh fruit and vegetables that are differentiated and sensitive to timeliness in supply, possess varied quality dimensions, and involve considerable supply accumulation and assortment. Digital ICT (Internet and mobile phones), in particular, is expected to facilitate international trade and encourage efficiency in the fruit and vegetables marketing system in two main ways. First, it reduces communication and search costs through cheaper and more effective media. Second, it improves market information and corrects information externalities along the supply chain, by promoting greater price transparency and enabling consumer preferences and tastes to be more precisely met. We employed a gravity model of international trade to test the hypothesis that ICT positively affects bilateral international trade in fruit and vegetables between member Asia-Pacific Economic Cooperation (APEC) economies in the period from 1997 to 2006. Explanatory variables include the usage of the Internet, mobile telephones and fixed telephone lines, and a broad range of factors that might determine the value of bilateral trade such as income per capita, population, distance between trading partners and common language. A Poisson pseudo-maximum likelihood model was estimated in order to handle zero trade observations and reduce biases caused by heteroskedasticity. Empirical results were not quite as expected, with relatively minor impact of digital ICT. They suggest that using digital ICT has significant positive effects on trade in fruit and vegetables between APEC countries only for the Internet in exporting countries. A stronger positive impact was discerned for the traditional form of ICT, fixed telephone lines in exporting importing countries. Nevertheless, fostering the development of digital ICT infrastructure and its diffusion should make exporters in APEC countries more competitive in the fruit and vegetables supply chain through the Internet effect, and boost their trade values in these products.International Relations/Trade,

Satellite system performance assessment for in-flight entertainment and air traffic control

Concurrent satellite systems have been proposed for IFE (In-Flight Entertainment) communications, thus demonstrating the capability of satellites to provide multimedia access to users in aircraft cabin. At the same time, an increasing interest in the use of satellite communications for ATC (Air Traffic Control) has been motivated by the increasing load of traditional radio links mainly in the VHF band, and uses the extended capacities the satellite may provide. However, the development of a dedicated satellite system for ATS (Air Traffic Services) and AOC (Airline Operational Communications) seems to be a long-term perspective. The objective of the presented system design is to provide both passenger application traffic access (Internet, GSM) and a high-reliability channel for aeronautical applications using the same satellite links. Due to the constraints in capacity and radio bandwidth allocation, very high frequencies (above 20 GHz) are considered here. The corresponding design implications for the air interface are taken into account and access performances are derived using a dedicated simulation model. Some preliminary results are shown in this paper to demonstrate the technical feasibility of such system design with increased capacity. More details and the open issues will be studied in the future of this research work

Economic Development Potential through IP Telephony for Namibia

IP telephony, economic growth, telecommunications, ICT, Granger causality, Namibia

On-board processing satellite network architecture and control study

For satellites to remain a vital part of future national and international communications, system concepts that use their inherent advantages to the fullest must be created. Network architectures that take maximum advantage of satellites equipped with onboard processing are explored. Satellite generations must accommodate various services for which satellites constitute the preferred vehicle of delivery. Such services tend to be those that are widely dispersed and present thin to medium loads to the system. Typical systems considered are thin and medium route telephony, maritime, land and aeronautical radio, VSAT data, low bit rate video teleconferencing, and high bit rate broadcast of high definition video. Delivery of services by TDMA and FDMA multiplexing techniques and combinations of the two for individual and mixed service types are studied. The possibilities offered by onboard circuit switched and packet switched architectures are examined and the results strongly support a preference for the latter. A detailed design architecture encompassing the onboard packet switch and its control, the related demand assigned TDMA burst structures, and destination packet protocols for routing traffic are presented. Fundamental onboard hardware requirements comprising speed, memory size, chip count, and power are estimated. The study concludes with identification of key enabling technologies and identifies a plan to develop a POC model