By Topic

Potentials, IEEE

Issue 3 • Date Aug.-Sept. 1997

Filter Results

Displaying Results 1 - 10 of 10
  • The wireless local loop

    Page(s): 8 - 10
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1380 KB)  

    In telephony, the loop is defined as the circuit connecting a subscriber's station (e.g., telephone set) with the line terminating equipment in a central office (a switch in the telephone network). The trunks start from the central office in the loop; they break down into several smaller bundles of circuits after moving away from the central office. These circuits are eventually separated into individual drops for the residential homes. The cost of the loop tends to be dominated by the residential side. (It is typically referred to as the "expensive last km"). This statement is particularly true for rural areas. The International Telecommunications Union's (ITU) projection indicates that 150 million new telephone lines will need to be installed in developing countries by the year 2000. As a result, telecommunication operators are looking to wireless technology to replace part of the hard-wire infrastructure. Wireless local loop (WLL) technology is being considered because the radio systems can be rapidly developed, easily extended and are distance insensitive. The WLL eliminates the wires, poles and ducts essential for a wired network. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • AX.25 [data link layer protocol for packet radio networks]

    Page(s): 14 - 16
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1500 KB)  

    For packet radio networks, the AX.25 data link layer protocol is most often used. However, TCP/IP (Transport Control Protocol/Internet Protocol) is also popular. The AX.25 protocol is a variant of the international X.25 protocol applied to wireless communication and packet radio. Most networks are composed of copper or fiber optic cable and provide reliable communication between hosts. The wireless medium is vastly different. It is less reliable and suffers from phenomena that are not present in conventional wired networks. For example, in a cable network all hosts on a network can hear each other. This makes "carrier sense" protocols such as Ethernet easy to implement. Before any host seizes the network, it first listens to help avoid collisions. Wireless networks also support carrier sense. However, hosts on the network cannot always hear each other for numerous reasons. Buildings and the local terrain are two important factors that determine the ability to receive information. We concentrate on the analysis of AX.25 packet radio networks operating in the 144-148 MHz band. Understanding and studying a network is a com analyzers, sometimes called "sniffers," are available to aid the packet user in understanding how a network operates. XNET, a network analyzer developed specifically to examine AX.25 networks, is described. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • EMF and your health

    Page(s): 3 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (638 KB)  

    First Page of the Article
    View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Grad School Application Process

    Page(s): 20 - 28
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1525 KB)  

    First Page of the Article
    View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Examining "Problematic Behaviors"

    Page(s): 30
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    First Page of the Article
    View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On The Job: Marketing Your Ideas

    Page(s): 40 - 41
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (298 KB)  

    First Page of the Article
    View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Looking Back: Secret Radio Station

    Page(s): 42 - 43
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    First Page of the Article
    View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The Arecibo Observatory

    Page(s): 33 - 35, 38-9
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2236 KB)  

    The Arecibo radar and radio telescope stands on a triangular platform as it hovers 220 m above the ground. The spherical dish resides in a natural sink hole, one of the largest in Puerto Rico. This platform is the focal point of an isolated scientific outpost where staff and students ply their trade. The Arecibo Observatory is a US national laboratory managed by Cornell University (New York) through a cooperative agreement with the National Science Foundation (NSF). The bulk of the astronomy work done focuses on stellar evolution, galaxy formation, and pulsars View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Cellular digital packet data

    Page(s): 11 - 13
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (844 KB)  

    Cellular digital packet data (CDPD) offers on-the-go users access to a low-cost, widespread, wireless data network. CDPD can be overlaid on existing analog cellular systems, and share their infrastructure equipment on a non-interfering basis. Basically, CDPD transmits packet data over idle cellular channels. It autonomously switches to another channel when the current channel is about to be assigned for voice usage. CDPD does not communicate with the underlining cellular network. However, CDPD does use its knowledge about the channel assignment algorithm of the cellular cell to predict the channels available for CDPD use. CDPD may serve as the wireless extension to other data networks (e.g., Internet) or public switched telephone networks. It supports connectionless network services which have packets called network protocol data units (NPDU). Every packet is routed individually based on the destination address of the packet and knowledge of the current network topology. Initially, CDPD provides two connectionless network services: the standard open systems interconnection connectionless network protocol and the Internet protocol View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IEEE Potentials is the magazine dedicated to undergraduate and graduate students and young professionals.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
David Tian
Carnegie Mellon University
david.tian@ieee.org