0 Development of a University Networking Project J. A. R. Pacheco de Carvalho Universidade da Beira Interior, Portugal P. A. J. Gomes Universidade da Beira Interior, Portugal H. Veiga Universidade da Beira Interior, Portugal A. D. Reis Universidade da Beira Interior, Portugal Universidade de Aveiro, Portugal D INTRODUCTION A communications channel has an important depen- dence for the channel capacity (C, in bps) to channel bandwidth (W, in Hz) ratio; this is capacity per unit bandwidth on signal to noise ratio (S/N, power of the signal over power of noise). Shannon's formula gives an upper limit for this dependence (Shannon & Weaver, 1949), C/W=log 2 (1+S/N), which represents channel ef- ficiency. Phase lock loops for waves and data symbols in the presence of noise have been given (Reis, Rocha, Gameira, & Carvalho, 2005). Properties of electromagnetic fields can be described by a set of four equations, known as the Maxwell's equations, due to J.C. Maxwell. From these basic equations, Maxwell discovered in 1865 the proof for electromagnetic waves, propagating in vacuum at light speed (Maxwell, 1954). It was concluded that light should be an electromagnetic wave. Heinrich Hertz in 1888 produced electromagnetic waves from electric and magnetic fields. Since long ago, electromagnetic waves in wide frequency ranges have been extensively used in tele- communications. In particular, electromagnetic waves have been increasingly used for data communications in computer networks. It is the case in wide area networks (WANs), metropolitan area networks (MANs), local area networks (LANs), and personal area networks (PANs). When the waves travel through an unguided medium such as the atmosphere, there are wireless com- munications. For a guided medium, such as an optical fiber, there are fixed (wired) communications. It is also the case of copper cabling systems, involving electric signals. Accordingly, there are wireless networks and fixed (wired) networks. Wireless communications re- lated to LANs originate as wireless local area networks (WLANs). Similarly, if they relate to PANs, wireless personal area networks (WPANs) arise. LANs and Ethernet LANs were developed in the late 1970s and early 1980s to constitute communication networks that provide interconnection of data communication devices within a small geographic area, say 10 km (Stallings, 1987). A family of IEEE 802 standards (IEEE-802 standards) exist for LANs. Ethernet, Token Ring, and Fiber-Dis- tributed Data Interface (FDDI) are examples of LAN technologies. Ethernet, corresponding to IEEE 802.3, has the most widely installed base worldwide. The Ethernet technology was developed in the mid-1970s by Xerox, Intel, and DEC, following its invention by Bob Metcalfe and David Boggs from Xerox in 1973. This was known as the experimental Ethernet at 2.94 Mbps that was patented in 1977 (U. S. Patent No. 4,036,220, 1977). Ethernet II at 10 Mbps appeared in 1982. Several other versions of Ethernet were de- veloped, initially based on the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) method for medium access control, which has been altered. Several types of Ethernet have existed, supporting different physical media and speed. They are repre- sented as x-Base-y, where x represents binary rate in Mbps and y corresponds to the type of medium used. Base stands for baseband, where the whole bandwidth is used to transmit digital signal without modulation Copyright © 2008, IGI Global, distributing in print or electronic forms without written permission of IGI Global is prohibited.