Notes on Wireless Communication- Unit 1.pptx

Early AM wireless system
First Broadcast
Modern AM
Development of FM
Evolution of Digital Radio
Cellular telephone concept

1. 1 WIRELESS COMMUNICATION UNIT- 1 Wireless Communication

2. Dr. TANUJA PATGAR Dept. of Electronics and Communication Dr. Ambedkar Institute of Technology Bangalore [email protected] 2

3. 3 Wireless Transmission Wireless communication systems consist of: Transmitters Antennas: radiates electromagnetic energy into air Receivers In some cases, transmitters and receivers are on same device, called transceivers. Transmitter Receiver Antenna Antenna

4. History and Evolution of Wireless Radio Systems

5. History of Wireless Radio Systems 1867 – Maxwell's predicted existence of EM Waves 1872 - Marlon Loomis was issued U.S. patent for a crude type of aerial wireless telegraph 1887- Heinrich Hertz performed laboratory experiments, that proved the existence of electromagnetic waves 1890 – Branly developed Coherer (apparatus for detecting radio waves) 1896 – Marconi demonstrated wireless telegraph 1897 – “Birth of radio” by Marconi and he started “Marconi station” on needles island to communicate with the English coast

6. History of Wireless Radio Systems 1898–Marconi experimented on tuned communication Wireless telegraph connection between England & France established 1895 –1901-- Marconi experimented with a wireless telegraph system 1901, Dec 12 - Marconi sent a message (the signal was a repetitive letter “s” in Morse code) from Cornwall, England to Signal Hill, St. John’s, Newfoundland—the first transmission across the Atlantic Ocean 1902 – First bidirectional communication across Atlantic 1909 – Marconi awarded Nobel prize for physics

7. Evolution of Wireless Radio System Early AM wireless system First Broadcast Modern AM Development of FM Evolution of Digital Radio Cellular telephone concept

8. Early AM Wireless Systems

9. Early AM Wireless Systems A typical early wireless transmitter is shown in Figure 1–1 The wireless transmitter would emit a signal of either long or short duration depending on the length of time the telegraph key was closed. The transmitted signal was the electromagnetic noise produced by the spark-gap discharge. This signal propagated through the air to a receiver located at some distance from the transmitter. The inductance & capacitance used to tune the output frequency of the spark gap. Due to the nature of the spark gap emission , maximum output occurs at a very low frequency At the receiver, the detected signal was interpreted by an operator as either a dot or a dash depending upon its duration. Using Morse code, combinations of dots and dashes stood for various alphanumeric characters. This early wireless transmission form is now known as amplitude modulation (AM) and in particular, on-off keying (OOK).

10. Limitations Very low frequency transmitter Low power & unstable output Need bigger & high elevated antenna Modulated signal is very sensitive to noise. Remedies These limitations can be overcome by using next generator wireless transmitter.

11. The First Broadcast 1905 - Reginald Fessenden conducted experiments with continuous wave (CW) wireless transmissions at Brant Rock, Massachusetts, using 50-kHz high-frequency alternators built by General Electric. The output of this type of generator was much more stable than that of a spark-gap or Poulsen transmitter, allowing him to experiment with a continuous form of amplitude modulation. 1906 – He credited with transmitting the first radio broadcast. 1910 - U.S. Navy led a major effort to develop wireless radio for ship-to-ship and ship-to-shore communications. 1920 – ( i ) Decade of high-frequency or short-wave radio development.

12. Contd.. (ii) Marconi’s research on radio wave propagation revealed that trans- atlantic radio transmission was feasible at frequencies much higher than that had previously been done. (iii) vacuum-tube technology had improved to such an extent as to increase the upper-frequency limit of their operation. 1926 – trans-oceanic telephone calls were available via high-frequency radio transmission. 1930–1940--Saw more advancement in radio technology with the invention of television, radar and vacuum tubes with the ability to generate “microwaves.”

13. Modern AM Amplitude modulation has been used for low-frequency radio broadcasting, shortwave broadcasting, low-definition television video-signal transmission, amateur and CB radio and various other low-profile services. Newer uses of AM include quadrature amplitude modulation (QAM or n-QAM, where n is a power of 2). QAM is a hybrid form of amplitude and phase modulation (PM) used for high-speed data transmission at RF frequencies. QAM is considered a digital modulation technique. Today, QAM is used extensively by broadband cable and wireless systems to achieve bandwidth efficiency.

14. The Development of FM 1920s - Major Edwin Armstrong worked on the principles of frequency and phase modulation Late 1960s and early 1970s - FM broadcasting became popular. Technological advances reduced the cost of consumer equipment and improved the quality of service. Many public safety departments were early adopters of FM for their communications.

15. 1983–AMPS(Advance Mobile Phone System) cellular telephone service, an FM-based system, was introduced in the United States Today FM is used – Transmissions in the FM broadcast band TV-broadcasting sound transmission Direct-satellite TV service Cordless telephones Every type of business band and mobile radio service. FM is capable of much more noise immunity than AM, and is now the most popular form of analog modulation.

16. Evolution of Digital Radio 1936 - First experimental broadband coaxial cable was tested 1941 - First operational L1 system that could handle 480 telephone calls was installed in Microwave radio relay systems developed in tandem with broadband coaxial cable systems. 1947- First microwave relay system was installed between Boston and New York 1951 - AT&T’s coast-to-coast microwave radio relay system was in place by Microwave relay systems which had lower construction and maintenance costs than coaxial cable . By 1970s, AT&T’s microwave relay system carried 70% of its voice traffic and 95% of its broadband television traffic.

17. Contd.. Most of these systems used analog forms of modulation, although simple digital modulation forms like Binary Frequency Shift Keying (BFSK) existed. 1970s and 1980s - Microwave digital radio technology and digital modulation techniques provide increased data rates over the same radio channel . Many of the analog and digital microwave relay systems in use became backup systems with newly installed fiber -optic cables.

18. Contd.. Many service providers of point-to-point connectivity were employing microwave and millimeter -wave radio transmission systems that use the most modern digital modulation techniques to obtain high data rate links. Cellular operators were using economical point-to-point microwave radio systems to backhaul aggregated bandwidth signals to a common network interface point from both remote and not-so-remote cell sites. Wireless Internet service providers (WISPs) are using digital radio equipment designed for the Unlicensed National Information Infrastructure (U-NII) bands for point-to-point and point-to-multipoint systems that provide high bit-rate Internet connections to their customers.

19. Contd.. Television broadcasting industry is in the process of transitioning to a high-definition television (HDTV) standard for over the-air broadcast that uses a digital transmission system. The oldest analog cellular systems (these systems are in the process of being phased out) are digital, and all of the newest wireless LAN, MAN, and PAN technologies use complex digital modulation schemes.

20. Cellular Telephone Concept Evolved from earlier mobile radio networks. The first mobile radio was used by police department or other low enforcement agencies. One way mobile radio system operating at 2Mhz – used to page the police cars. 1968 – FCC asked for a proposal with high capacity, efficient mobile phone system. AT & T proposed core idea of cellular system. Illustration of a cell with a mobile station (MS) and a base station (BS) BS MS Cell Hexagonal cell area used in Ideal cell area Alterative shape o MS

21. Development of Modern Telecommunications Infrastructure Wireless networks and systems have the basic function of connecting users to Public Switched Telephone Network(PSTN) or the Public Data Network(PDN). So it is necessary to examine- what these 2 public networks are ? & How they have evolved ? Public Switched Telephone Network(PSTN) To explain the physical infrastructure of the PSTN, it is necessary to consider the various pathways of communication available through the system. Two types of PSTN Intra-office Inter-office

22. PSTN Intra-office call through a local exchange

23. PSTN inter-office call over an inter-exchange trunk line

24. Signaling System #7 The early PSTN USED “In – band “ signaling to set up inter-office and long distance telephone calls – This has many disadvantages. The system of using a separate facility or channel to perform the call routing function has developed. “Out of band “ signaling Today it is called CCIS(Common Channel Interface Signaling) or SS#7.

25. The Network Elements of SS7 System

26. SS7 system is a packet network that consists of STP & Transmission facilities linking the STP’s as shown in fig.3 The STP’s are connected to SSP’s at local exchange and interface with the local exchange switch or mobile switching center in case of a PLMN(public land mobile network) SSP’s convert signaling information to SS7 signaling Messages in the form of data packets that are sent over SS7 network. STP’s serve as routers. RCL’s between STP’s provide SS7 network with a degree of reliability. SS7 provides 2 forms of services:- - Circuit related –Setting up & tearing down of circuits - Non circuit related –Access of information from data bases maintained by the network. SCP – Acts as interface between SS7 network and various databases maintained by telephone companies. NOC(Network operation center) is the maintenance center. All PSTN and PLMN’s use SS7 for signaling operations within the network and between the network and other networks.

27. Mobile Switching Centre

28. Base Station

29. Mobile Station

30. Public D ata N etwork Dept. of Electronics and Communication, Dr. AIT 30

31. Public Data Network It is evolved in response to connectivity needs of business, industry & govt. – for transport of data over WAN’s. Often depicted as fuzzy “cloud” on diagrams –show how end users are connected to it. Reason for the use of cloud Network uses different transport technologies such as T-carrier,, XDSL, Ethernet, ISDN,ATM,SONET etc. P hysical media to transmit Data within it & from end pt. to end pt. Connections - through copper pairs, fiber facilities or wireless radio links. 31

32. Public Data Network Data n/w- transports packets of data depending on type of transport protocol. PDN- supports service structures including permanent (ii)virtual (iii) switched virtual circuits & iv ) permanent virtual circuits. PDN – consists of “connectionless systems – use connectionless protocols – to forward data packets through n/w – reduce overhead requirements & faster. New technology – uses both connection oriented and connectionless protocols- to obtain the benefits of both technologies. In addition to this there are 2 more n/w’s 1. Private data n/w 2. virtual private data n/w(VPDN) Private data n/w use same tech.as PDN- can be constructed, owned & maintained by user/leased from some service provider. 32

33. Additional PDN’s Broadband cable system Internet Cellular telephone system 33

34. Broad B and C able S ystem 34

35. Broad B and C able S ystem Broadband cable - sophisticated and complex wideband networks designed to deliver analog and digital video signals (including HDTV), data, and plain-old telephone service to the subscriber. The video content can come from local off-air television stations, satellite feeds of network or distant-station program content, and local access facilities The data service typically connects to an Internet service provider (ISP) and telephone service connects to the PSTN. The most important change in the legacy cable-TV plant is the migration to the two-way hybrid fibre coaxial cable system shown in Figure 1–6. The bandwidth of cable systems has been expanded to 870 MHz, and the use of the frequency spectrum between 5 and 42 MHz now allows for upstream data transmission over the network Another important aspect to the evolution of the cable system is the development and standardization of the cable modem (CM) 35

36. Broad B and C able S ystem The Data-Over-Cable-Service interface specification (DOCSIS) project has led to multiple-vendor interoperability of cable modems located at the subscriber premise. Cable M odem T ermination S ystems (CMTS) located at the cable service providers’ network centers. These systems allow for a shared high-speed data connection over the cable network to the Internet that passes Ethernet packets to and from the subscriber’s cable modem to the subscriber’s PC. 36

37. Internet 37

38. Internet The Internet is the world’s largest computer network . Over the Internet any computer or computer network may access any other computer or computer network . The structure of the Internet is shown in Figure . It consists of thousands of computer networks interconnected by dedicated special-purpose switches called routers . The routers are interconnected by a wide area network (WAN) backbone . WAN backbone actually consists of several networks operated by national service providers ( SprintLink , UUNet Technologies, internet MCI, etc .) These networks consist mainly of high-speed, fiber-optic, long-haul transport systems that are interconnected at a limited number of hubs that also allow for the connection of regional ISPs. 38

39. Internet National Service Provider (NSP) networks are interconnected to each other at switching centers known as Network A ccess P oints (NAPs ). Regional ISPs may tap into the backbone at either the NSP hubs or the NAPs . If an individual wants to connect to the Internet, they must usually go through an ISP . The user might connect to ISP through PSTN over low-speed dial-up connection using modem that communicates with “ modem pool” at ISP or through high-speed cable modem or ADSL (Adaptive D igital S ubscriber L ine ) service. These services are usually connected through PDN to ISP . 39

40. Internet Local Area Network (LAN) at an enterprise location will usually be connected to the ISP through some type of high- speed connection to the PDN (usually leased from a service provider) and then through the ISP’s high-speed connection to the PDN . The ISP will in turn be connected to the Internet through another high-speed network connection . Today , one may be connected to the Internet by wireless device while roaming or while connected to LAN . Telephones and P ersonal D igital A ssistants (PDAs) allow one to connect through the packet data network. The Web “browser” experience is not the same as with a desktop computer but it is an Internet connection 40

41. Cellular Telephone Systems The technology used to implement cellular systems has evolved from analog (first generation or 1G), to digital (second generation or 2G), to systems with medium- speed data access (called 2.5G ). High-speed data-access third-generation or 3G systems are already being deployed worldwide . Cellular operators have expanded coverage and capacity by using new frequency allocations, new air interface technologies, and cell splitting, and they have increased the functionality of their systems by expanding their scope to include access to the PDN, as well as the PSTN. 41

42. Thank You 42 [email protected]