Wednesday, August 19, 2009
Wednesday, August 12, 2009
Monday, August 10, 2009
Wireless communications is a rapidly growing segment of the communications industry, with the potential to provide high-speed high-quality information exchange between portable devices located anywhere in the world. Potential applications enabled by this technology include multimedia Internet-enabled cell phones, smart homes and appliances, automated highway systems, video teleconferencing and distance learning, and autonomous sensor networks, to name just a few. However, supporting these applications using wireless techniques poses a significant technical challenge. This course will cover advanced topics in wireless communications for voice, data, and multimedia. We begin with a brief overview of current wireless systems and standards. We then characterize the wireless channel, including path loss for different environments, random log-normal shadowing due to signal attenuation, and the flat and frequency-selective properties of multipath fading. Next we examine the fundamental capacity limits of wireless channels and the characteristics of the capacity-achieving transmission strategies. These strategies are typically not practical. Thus, our next focus will be on practical digital modulation techniques and their performance under wireless channel impairments, including flat and frequency selective fading. The next part of the course is spent investigating techniques to improve the speed and performance of wireless links. We will investigate the design and performance of adaptive modulation and diversity techniques to compensate for flat-fading. Three techniques to combat frequency-selective fading are then examined: adaptive equalization, multicarrier modulation, and spread spectrum. We will also study the multiple access capabilities of spread spectrum with multiuser detection. The course concludes with a brief overview of wireless networks, including multiple and random access techniques, WLANs, cellular system design, and ad-hoc network design. Applications for these systems, including the evolution of cell phones and PDAs, smart homes and appliances, sensor networks, and automated highways and skyways, will also be discussed.
Sunday, August 2, 2009
Saturday, August 1, 2009
Examples of telecommunications networks are:
* Computer network
* the Internet Network- The internet network is a global ‘network of networks’. The internet is connected via an Internet Service Provider (ISP) and then becomes part of a network. This network then connects to a larger corporate network that interconnects with several other similar networks through Network Access Points (NAPs).
* the Public switched telephone network
* the global Telex network
* the aeronautical ACARS network