Chapter 6: Business Networks and Telecommunications.Learning Objectives:
- Describe business and home applications of digital telecommunications.
- Identify the major media and devices used in telecommunications.
- Explain the concept of protocols.
- Compare and contrast various networking and Internet services.
- List networking technologies and trends that are likely to have an impact on businesses and information management in the near future.
- Discuss the pros and cons of telecommuting.
Telecommunications is the transmittal of data and information from one point to another, referring to technologies which allow communication over a distance. Networking technologies have brought s4everal improvements to business processes in this area:
- Better business communications.
- Greater efficiency.
- Better distribution of data.
- Instant transactions.
- A more flexible and mobile workforce.
- Alternative (numerous) channels of communication.
Cellular phones derive their name from the territories of service providers, which are divided into areas known as cells. Each cell has at its center a computerized transceiver (transmitter-receiver), which both transmits signals to another receiver and receives signals from another transmitter. Many mobile phones have been merged with digital cameras, PDAs, and GPS (global positioning system) circuitry.
Videoconferencing is used to save on travel costs and lodging, care fleets, and the time of highly salaried employees, whether they work in different organizations or at different sites of the same organization. The increasing speed of internet connections makes it easy for anyone with a high-speed link to establish videoconferences by either using a peer-to-peer link or by using the services of a third party, a company that specializes in maintaining videoconferencing hardware and software.
Fax, or facsimile, is the transmission and reception of images over telephone lines. The receiving machine converts the digitized codes into images, and similarly transmits information. Faxing can also be executed through the internet using special software, and can be combined with scanning, printing, and copying functions in "multifunction" machines.
RFID (radio frequency identification) technology enables us to conclude transactions and to make payments very quickly. Telecommunications allows for the fast and reliable transfer of information necessary to operate such automated systems. RFID technology is also used in warehouses where employees can use handheld units to check a central system for the availability and location of items.
Peer-to-peer file sharing is done through the internet, through the use of special software applications. Using peer-to-peer file sharing, the software conducts a search for the file you wish to download. It finds several sources, and then downloads each segment of the file from a different source, decreasing the overall time of the download by a considerable extent.
Web-empowered commerce has also been made possible through the proliferation of telecommunications; increasingly fast digital communications enables millions of organizations to conduct business and individuals to research, market, educate, train, shop, purchase, and pay online. Whole new industries have been created thanks to this technology.
A communications medium is the physical means that transports the signal. The bandwidth of the medium is the speed at which data is communicated, which is also called the transmission rate, or simply the bit rate, and is measured in bits per second (bps).
- bps: bits per second.
- Kbps: thousands of bits per second.
- Mbps: millions of bits per second (mega bps).
- Gbps: billions of bits per second (giga bps).
- Tbps: trillions of bits per second (tera bps).
When a communications medium can carry only one transmission at a time, such as dial-up internet or ethernet computer network connections, it is known as baseband. When a line is capable of carrying multiple transmissions simultaneously, it is called broadband.
- Twisted par cable: high availability, low to medium bandwidth, high vulnerability to electromagnetic interference.
- Radio waves: high availability, medium to high bandwidth, low vulnerability to electronic interference (but vulnerable to RFI, radio frequency interference).
- Microwaves: low availability, high bandwidth, and low vulnerability to electromagnetic interference.
- Coaxial (TV) cables: high availability, high bandwidth, and low vulnerability to electromagnetic interference.
- Optical Fibers: moderate but growing availability, highest bandwidth possible, and immune to electromagnetic interference.
- Electric power lines (BPL): very high availability, high bandwidth, but also high vulnerability to electromagnetic interference.
Twisted pair cables are used in computer and telephone networks, and are comprised of insulated copper wires which are twisted together to reduce electromagnetic interference (EMI) and then encased in a plastic cover. They are flexible, reliable, and cheap.
Coaxial cables are used for cable television transmission, and is commonly called "cable." Television companies use the same network they employ to transmit television programming also to link households and businesses to the internet.
Fiber optic technology uses light instead of electricity to represent bits, and the lines are made of thin fiberglass filaments. A transmitter sends bursts of light using a laser or light-emitting diode device. This technology can allow internet connections into the range of Tbps.
Radio frequency (RF) technologies, such as those used by Wi-Fi and Bluetooth, use radio waves to carry bits. Microwaves are high-frequency radio waves that can carry signals over long distances with high accuracy. However, weather conditions can degrade communication quality.
Signals can also be transmitted using microwaves via satellite links. Geostationary (GEO) satellites keep place with the Earth's rotation, effectively staying stationary in relationship to the Earth. Low earth orbit satellites (LEO) are closer to the earth, and offer faster communications. Because LEO satellites revolve around the globe every few hours, multiple LEOs are required to maintain continuous coverage for uninterrupted communication.
Electrical power lines has just recently been tapped for telecommunications. The bits in an electric power grid are represented by electric impulses, but they must be distinct from the regular power that flows through the grid. In some regions of the United States, broadband service is offered through power lines. The service is referred to as Broadband over Power Line (BPL), or Power Line Communication (PLC).
A network is a combination of devices or nodes (computers or communication devices) connected to each other through one of the communication channels just discussed. Computer networks are classified according to their reach and complexity. There are three basic types of networks: LANs (local area networks), MANs (metropolitan area networks), and WANs (wide area networks). PANs (personal area networks) are sometimes added to this list.
A computer network within a building, or a campus of adjacent buildings, is called a local area network (LAN). They are set up by organizations to enhance communications among employees and to share IT resources. In office LANs, one computer is often used as a central repository of programs and files that all connected computers can use; this computer is called a server. When a LAN has a server, the server usually has centralized control of communications among the connected computers and between the computers and the server itself. A peer-to-peer LAN is one in which no central device controls communications.
Wireless LANs (WLANs) offer significant benefits: installation is easy, and you can move equipment wherever it is needed. Wireless networks also offer significant savings in some environments. Scalability is the ease of expanding a system. It is easy to add more nodes, or clients, to a WLAN, because all that is needed is wireless circuitry in any device that comes within range of a wireless network. However, WLANs can also be less secure than LANs.
A metropolitan area network (MAN) usually links multiple LANs within a large city or metropolitan region and typically spans a distance of up to 30 miles. For example, the LAN in a chemistry lab might be linked to a research hospital's LAN and to a pharmaceutical company's LAN several miles away in the same city to form a MAN. The high-speed links between LANs within a MAN typically use fiber optic or wireless broadband connections.
Wide area networks (WANs) are far-reaching systems of networks which can literally span continents. The simplest example of a WAN is a dial-up connection to a network provider's services over basic telephone lines. A more complex WAN is a satellite linkup between LANs in two different countries. The most well-known WAN is the Internet (capitalized!

).
A common carrier provided public telephone lines that anyone can access, and leased lines, which are dedicated to the leasing organization's exclusive use. Value-added networks (VANs) provide enhanced network services,fulfilling organizational needs for reliable data communications while relieving the organization of the burden of providing its own network management and maintenance. However, VANs cost much more than connections offered by Internet service providers (ISPs).
Personal area networks (PANs) are wireless networks designed for handheld and portable devices such as PDAs, cell phones, and tablet or laptop computers, and is intended for use by only one or two people. Transmission speed is low to moderate, and the maximum distance between devices is generally 33 feet.
Electronic data interchange: EDI. <---- That's pretty much self-explanatory.
Network interface cards (NICs) allow a device to connect to a network. A hub is a common device often used as a central location to connect computers or devices to a local network. A switch is like a hub, except that it is more intelligent. Communications that go through a hub are broadcast to all devices attached to the hub; communications through a switch go only to designated devices on the network. A bridge is a device that connects two networks, and a router routes data packets to the next node on their way to the final destination. Routers keep tables of network addresses, known as internet protocol (IP) addresses, which identify each computer on the network along with the best routes to other network addresses. A repeater amplifies or regenerates signals so that they do not become weak or distorted.
A modem, or modular demodulator, is a device whose purpose is to translate communications signals from analog to digital, and vice versa. Telephone lines, for example, handle continuous (analog) signals rather than digital signals, which consist of discrete bursts. Changing digital to analog is modulation, and changing analog to digital is demodulation. If you have DSL service, the device used is called a DSL modem, and if you use a power line it's called a BPL modem.
A virtual private network (VPN) only allows authorized users to access company resources. VPNs enable the use of intranets and extranets. An intranet is a network that uses Web technologies to serve an organization's employees who are located in several sites that might be many miles apart; an extranet serves both the employees and other enterprises that do business with the organization.
Switching Techniques:
- Circuit Switching: a dedicated channel (circuit) is established for the duration of the transmission.
- Packet Switching: a message is broken up into packets, groups of bits, and transmitted.
- Destination address.
- Source address.
- Data.
- Error Detection Bits.
- Frame Relay: high-speed flexible packet switching used in WANs.
A communications protocol is a set of rules that govern communication between computers or between computers and other computer-related devices that exchange data. Network protocols do the same thing for networks.
TCP/IP (transmission control protocol/internet protocol) is primarily used on the Internet. Transmission control protocol ensures that the packets arrive accurately and in the proper order, while internet protocol ensures delivery of packets from node to node in the most efficient manner by directing it through various hosts.
Every device on the Internet "backbone" is uniquely identified with a numerical label known as an internet protocol number (IP number), a 32-bit numeric address, presented in four parts separated by period. Domain name resolution enables you to replace a website's IP number with written text through DNS (domain name system). DNS servers are maintained by internet service providers (ISPs) and other organizations.
Servers and many other computers and devices are assigned permanent IP numbers, called a static IP number. A computer connected to the Internet intermittently might be assigned a temporary IP number for the duration of its connection only, and is known as a dynamic IP number. This way an IP number can be reassigned to someone else when you have disconnected from the internet.
CSMA/CD (carrier sense multiple access with collision detection) ensures that there are no collisions in transmission and that each device transmits without interfering with another (used with Ethernet LAN protocol).
IEEE 802.11 Wi-FI is a family of wireless protocols (Wi-Fi = wireless fidelity). A single Wi-Fi router can be connected to an access point (AP), which in turn is connected to a wired network and usually to the Internet, allowing tens to hundreds of Wi-Fi-equipped devices to share the same Internet link. A direct link to a wireless router or AP creates a hotspot.
IEEE 802.15 Bluetooh has a short range; examples are wireless keyboards.
IEEE 802.16 WiMAX (worldwide interoperability for microwave access) increases the range and speed of wireless communications, and uses licensed radio frequencies of 2-11 GHz.
IEEE 802.20 MBWA (mobile broadband wireless access) functions similarly to cell phone communications, because it controls communication from stationary towers. It provides mobile communications which is compatible with IP services. This should enable worldwide deployment of affordable, always-on wireless access.
Protocols:
- 802.11a 60-foot range, 54 Mbps speed, LAN.
- 802.11b 300-foot range, 11 Mbps, LAN.
- 082.11g 300-foot range, 54 Mbps, LAN.
- 802.15 Bluetooth: 33-foot range, 1 Mbps, LAN.
- 802.16 WiMAX: 31-mile range, 100 Mbps, MAN.
- 802.20 MBWA: global range, 4 Mbps, mobile voice, data, and internet communications.
Internet services:
- Dial-up: 56 Kbps, universal availability, $9-11 per month.
- Cable: 0.5-3 Mbps, widespread availability, $30-50 per month.
- DSL: 0.5-8 Mbps, more limited than cable, $30-50 per month.
- T1, T3: 1.544 Mbps/44.736 Mbps, widespread, $300-1,000/$3,000-10,000 per month.
- Satellite: 1 Mbps, widespread, $40-50 per month.
- Fixed wireless: 100 Mbps, limited, $2,000 per month.
- OC-3: 155.52 Mbps, limited availability, $60,000 per month.
- OC-12: 622.08 Mbps, limited availability, several hundred thousand dollars.
- OC-48, 2.488 Gbps, limited availability, several hundred thousand dollars.
- BPL: 3 Mbps, limited availability, $30-40 per month.
DSL: digital subscriber line.
T1 and T3 lines are point-to-point dedicated digital circuits provided by telephone companies.
Fixed wireless is point-to-point transmission between two stationary devices.
OC: optical carriers, using optical fibers.
RFID applications: Access control, tracking, livestock management, anti-theft measures, transportation of luggage, retail, pharmaceuticals, health care, shopping, product information, customer service, appliances, agriculture, waste management, etc.