1. COMMUNICATIONS & NETWORKS Shanti Kusumawardhani, MBus.Sys. shanti@pmbs.ac.id

2. Analog VS Digital Digital - describes any system based on discontinuous data or events. In the case of computers, it refers to communication signals or information represented in a two-state (binary) way using electronic or electromagnetic signals. Each 0 and 1 signal represents a bit Analog - Continuously varying in strength and/or quality.

3. Purpose of Modem Modem is short for modulate/demodulate. A sending modem modulates digital signals into analog signals for transmission over phone lines. A receiving modem demodulates the analog signals back into digital signals

4. Analog to Digital Converting analog data to digital data requires a technique called “Digital Sampling” Examples of digital sampling: ◦ Tape recorder, voices, musical instruments (analog)  CD (digital) ◦ Still pictures (analog)  movies (digital)

5. Networks A system of interconnected computers, telephones, or other communications devices that can communicate with one another and share applications and data Before we had computer networks, people used “sneakernet” to share data between computers ◦ Person 1 saved their document to a floppy disk ◦ Then they walked over to person 2’s desk (wearing sneakers, of course) and handed over the disk to person 2 ◦ Person 2 loaded the disk into their computer to read and edit the document

6. Networks: The Benefits  Sharing of peripheral devices  Sharing of programs and data  Better communications  Security of information  Access to databases

7. Types of Networks Wide area network (WAN) is a communications network that covers a wide geographical area, such as a country or the world Metropolitan area network (MAN) is a communications network covering a city or a suburb Local area network (LAN) connects computers and devices in a limited geographical area, such as one office, one building, or a group of buildings close together

8. Types of Networks Home area network (HAN) is a communications network that uses wired, cable or wireless connections to link a household’s digital devices Personal area network (PAN) is a communications network that uses short- range wireless technology to connect an individual’s personal electronics

9. Network Structures Client-Server LAN - consists of clients, which are microcomputers that request data, and servers, which are computers that supply data. Different servers may be used to manage different tasks: ◦ File server ◦ Database server ◦ Print server ◦ Web server ◦ Mail server

10. Network Structures Peer to Peer LAN - All microcomputers on the network communicate directly with one another without relying on a server. Peer-to-peer networks are less expensive than client-server networks and work effectively for up to 25 computers. Beyond that, they slow down under heavy use

12. Network Topologies  Bus – all nodes are connected to a single wire or cable Bus

13. Ring Ring – all nodes are connected in a continuous loop Network Topologies

14. Star – all nodes are connected through a central host Star Network Topologies

15. Network Scope Intranet – an organization’s internal private network that uses the infrastructure and standards of the internet and the web Extranet – private intranets that connect not only internal personnel but also selected suppliers and other strategic parties Virtual Private Network – private networks that use a public network (usually the internet) to connect remote sites

16. Wireless Communications Media Infrared transmission – transmission that sends data signals using infrared-light waves at a frequency too low for human eyes to receive and interpret (speed: 1-4 Mbps) Broadcast radio – a wireless transmission medium that sends data over long distances between regions, states, or countries (speed: 2 Mbps)

17. Wireless Communications Media Microwave radio – transmits voice and data through the atmosphere as superhigh-frequency radio waves called microwaves (speed: 45 Mbps) Communications Satellites – microwave relay stations in orbit around the earth

18. Communications Satellites GEO (Geostationary Earth Orbit) Satellites ◦More than 22,300 miles above equator ◦Satellites travel at the same speed of the earth

19. Communications Satellites MEO (Medium Earth Orbit) ◦5,000-10,000 miles up ◦The orbital periods of MEO satellites range from about 2-12 hours ◦A fleet of several MEO satellites, with orbits properly coordinated, can provide global wireless communication coverage

20. Communications Satellites LEO (Low Earth Orbit) ◦200-1,000 miles up ◦LEO satellite system employs a large fleet of "birds," each in a circular orbit at a constant altitude. ◦Each revolution takes approximately 90 minutes to a few hours.

21. Long-Distance Wireless: One-Way Communication Global Positioning System (GPS) ◦Consists of 27 earth-orbiting satellites, continuously transmitting timed radio signals that can be used to identify earth locations

22. How GPS Works The principle behind GPS is the measurement of distance (or “range”) between the satellites and the receiver A GPS receiver can pick up transmissions from any of four satellites, interpret the information from each, and pinpoint the receiver’s longitude, latitude, and altitude The system is accurate within 3-50 feet

23. How GPS Works

24. Long-Distance Wireless: One-Way Communication Pagers – simple radio receivers that receive data sent from a special radio transmitter  Efficient for transmitting one-way information (emergency messages, news, stock prices, etc.) at low cost to single or multiple receivers

25. 1G Cellular Service: Analog Cellphones ◦ Design primarily for communications by voice through a system of ground area cells ◦ Calls are directed between cells by a Mobile-Telephone Switching Office (MTSO) Long-Distance Wireless: Two-Way Communication

26. 2G Wireless Services: Digital Cellphones & PDAs ◦ Use a network of cell towers to send voice communications and data over the air in digital form ◦ Has 2 standards:  GSM  data rates up to 9.6 kbps  CDMA  data rates up to 1404 kbps Long-Distance Wireless: Two-Way Communication

27. 2.5G Wireless Digital Services ◦Upgrade of GSM ◦GPRS  data rates 30-100 kbps ◦EDGE  data rates up to 236 kbps 3G Wireless Digital Services ◦Broadband technology ◦Two important upgrades:  UMTS  data rates 220-320 kbps  EV-DO  data rates up to 2 Mbps

28. Long-Distance Wireless: Two-Way Communication 3.5G Wireless Digital Services ◦HSDPA  data rates up to 14 Mbps 4G Wireless Digital Services ◦Use WiMax technology ◦A wireless standard capable of transmitting at a typical range of 6-10 miles (max. 20-30 miles) at up to 20 Mbps

29. Short-Range Wireless: Two-Way Communication Three kinds of networks covered by this range: ◦Local Area Network (range 50-150 feet) ◦Personal Area Network (range 30-32 feet) ◦Home Automation Network (range 100-250 feet)

30. Short-Range Wireless for LAN Wi-Fi – a short-range wireless digital standard aimed at helping portable computers and handheld wireless devices to communicate at high speed and share internet connection

32. Short-Range Wireless for PAN Bluetooth – a short-range wireless digital standard aimed at linking cellphones, PDAs, computers, and peripherals Ultra wideband (UWB) – a technology that uses low power source to send out millions of bursts of radio energy every second over many different frequencies, which are then reassembled by a UWB receiver  100 times faster than Bluetooth

33. Short-Range Wireless for PAN Wireless USB ◦Can combine the speed and security of wired technology with the ease of use of wireless ◦Would have a typical range of 32 feet and a maximum data rate of 480 Mbps

34. Short-Range Wireless for HAN Insteon – combines electric power line and wireless technology, capable of sending data at 13.1 kbps at a typical range of 150 feet ZigBee – an entirely wireless, very power-efficient technology that can send data at 128 kbps at a range of 250 feet Z-Wave – just like ZigBee, can send data at 127 kbps to a range of 100 feet