1. Wireless and Mobile Communications - CN331
University of Benghazi
Faculty of Information Technology
Department of Computer Networks and Communications
Wireless and Mobile Communications - CN331
Lecturer: Khalid Ateea Alfaitori

2. Course Delivery Details
Contact Methods:
Lecturer name: Khalid Ateea Alfaitori
Assessment Method:
1- Midterm Exam=25%
2- Course Work Report=25%
3- Final Exam=50%
Time and Place:
Monday 14:00-16:30 (Weekly)
Classroom no. 6
Reference:
“Wireless Communications, Principles and Practice”, 2nd Edition, Theodore S. Rappaport, Prentice Hall.

3. Learning Outcomes To identify wireless communications systems.
To recognize the foundations of wireless communications.
To identify wireless communications systems.
To identify cellular system concepts.
To describe wireless channel characteristics.
To distinguish between different Multiple Access schemes.

4. course contents An Overview of Wireless Communications.
Cellular Systems, concepts and practice.
Wireless Channels Characterization.
Multiple Access Schemes.

5. Introduction to Wireless Communication Systems
Chapter 1
Introduction to Wireless
Communication Systems

6. Outline of Chapter 1 Brief History of Wireless Communications
Basic Terminology
Examples of Wireless Communication Systems
• Paging Systems
• Cordless Telephone Systems
• Cellular Radio Communications
• Wireless Area Networks (WANs)

9. Brief History of Wireless Communications “Birth of Mobile Telephony”
1960s - Improved Mobile Telephone Service (IMTS) was introduced.
• IMTS supports full-duplex, i.e. two parts can talk simultaneously.
• IMTS supports auto-dial, i.e. no operator’s assistance.
• IMTS supports auto-trunking, i.e. no dedicated frequency. Therefore, it is possible to sell mobile equipment to more than C users by assigning channels on a “demand” basis satisfying a certain blockage probability.
1970s - IMTS quickly became saturated in major markets. For example, in 1976, Bell Mobile Phone service for the New York City area had only 12 channels and could serve only 543 customers; service was poor due to call blocking due to the few available channels.

10. 1970s - “Cellular” concept was introduced: This involves breaking a coverage zone into small “cells” (regions), each of which reuse portions of the spectrum to improve efficiency of spectrum usage (more details to follow later in this chapter).
The Nippon Telephone and Telegraph company (NTT) in Japan introduced first commercial cellular phone system. The system, deployed in 1979, uses 600 FM duplex channels (25 kHz for each one-way link) in the 800 MHz band.
The Nordic Mobile Telephone system (NMT 450) In Europe was developed it for the 450 MHz band and uses 25 kHz channels.

11. Wireless Communications System Definitions
Base Station
A fixed station in a mobile radio system used for radio communication with mobile stations. Base stations are located at the center or on the edge of a coverage region and consist of radio channels and transmitter and receiver antennas mounted on a tower.
Control Channel
Radio channels used for transmission of call setup, call request, call initiation, and other beacon or control purposes.
Forward Channel
Radio channel used for transmission of information from the base station to the mobile.

12. Wireless Communications System Definitions
Reverse Channel
Radio channel used for transmission of information from the mobile to base station.
Half Duplex Systems
Communication systems which allow two-way communication by using the same radio channel for both transmission and reception. At any given time, the user can only either transmit or receive information.
Full Duplex Systems
Communication systems which allow simultaneous two-way communication. Transmission and reception is typically on two different channels

13. Wireless Communications System Definitions
Simplex Systems
Communication systems which provide only one-way communication.
Mobile Station
A station in the cellular radio service intended for use while in motion at unspecified locations. Mobile stations may be hand-held personal units (portables) or installed in vehicles (mobiles).
Mobile Switching Center
Switching center which coordinates the routing of calls in a large service area. In a cellular radio system, the MSC connects the cellular base stations and the mobiles to the PSTN. An MSC is also called a mobile telephone switching office (MTSO).
Transceiver
A device capable of simultaneously transmitting and receiving radio signals.

14. Wireless Communications System Definitions
Page
A brief message which is broadcast over the entire service area, usually in a simulcast fashion by many base stations at the same time.
Handoff
The process of transferring a mobile station from one channel or base station to another.
Subscriber
A user who pays subscription charges for using a mobile communications system.
Roamer
A mobile station which operates in a service area (market) other than that from which service has been subscribed.

19. Paging Systems
Paging systems are communication systems that send brief messages (numeric, alphanumeric or voice) to a subscriber.
Diagram of a wide area paging system. The paging control center dispatches pages received from the PSTN throughout several cities at the same time.

20. Paging Systems
System does not need to know the location of the pager.
Same message is simultaneously transmitted from each base station, i.e. simulcasting. Each user “listens” all transmissions, however only decodes its “intended message” associated with its unique subscription number.
Paging systems are designed to provide very reliable coverage, even inside buildings.

21. Cordless Telephone Systems
Cordless telephone systems are full duplex communication systems that use radio to connect a portable handset to a dedicated base station, which is then connected to a dedicated telephone line with a specific telephone number on the public switched telephone network (PSTN).
In first generation cordless telephone systems (manufactured in the 1980s), the portable unit communicates only to the dedicated base unit and only over distances of a few tens of meters.
Second generation cordless telephones have recently been introduced which allow subscribers to use their handsets at many outdoor locations within urban centers such as London or Hong Kong.

22. Cordless telephone systems provide the user with limited range and mobility, as it is usually not possible to maintain a call if the user travels outside the range of the base station.
Typical second generation base stations provide coverage ranges up to a few hundred meters.
Diagram of a cordless telephone system.

23. Cellular Telephone Systems
A cellular telephone system provides a wireless connection to the PSTN for
any user location within the radio range of the system.
Cellular systems accommodate a large number of users over a large geographic area, within a limited frequency spectrum.
In cellular radio systems high capacity is achieved by limiting the coverage of each base station transmitter to a small geographic area called a cell so that the same radio channels may be reused by another base station located some distance away.
A sophisticated switching technique called a handoff enables a call to proceed uninterrupted when the user moves from one cell to another.

24. Basics of Cellular Radio Communications

25. Basics of Cellular Radio Communications (Cont’d)

26. Basics of Cellular Radio Communications (Cont’d)
Communication between the base station and the mobiles is defined by standard common air interface (CAI) that specifies four different channels.
The channels used for voice transmission from the base station to mobiles are called forward voice channels (FVC) and the channels used for voice transmission from mobiles to the base station are called reverse voice channels (RVC).
The two channels responsible for initiating mobile calls are the forward control channels (FCC) and reverse control channels (RCC).
Control channels are often called setup channels because they are only involved in setting up a call and moving it to an unused voice channel.
Control channels transmit and receive data messages that carry call initiation and service requests, and are monitored by mobiles when they do not have a call in progress.

27. Basics of Cellular Radio Communications (Cont’d)
The towers represent base stations which provide radio access between mobile users and the Mobile Switching Center (MSC).

28. How a Cellular Telephone Call is Made

29. How a Cellular Telephone Call is Made (Cont’d)

30. How a Cellular Telephone Call is Made (Cont’d)
Timing diagram illustrating how a call to a mobile user initiated by a landline subscriber is established.

31. How a Cellular Telephone Call is Made (Cont’d)
Timing diagram illustrating how a call initiated by a mobile is established.

32. Comparison of Common Mobile Radio Systems
Most people are familiar with a number of mobile radio communication systems used in everyday life. Garage door openers, remote controllers for home entertainment equipment, cordless telephones, hand-held walkie-talkies, pagers (also called paging receivers or "beepers"), and cellular telephones are all examples of mobile radio communication systems. However, the cost, complexity, performance, and types of services offered by each of these mobile systems are vastly different.
The following tables illustrate the types of service, level of infrastructure, cost, and complexity required for the subscriber segment and base station segment of each of the five mobile or portable radio systems discussed earlier in this chapter.

33. Comparison of Mobile Communication Systems — Mobile Station
Comparison of Mobile Communication Systems — Base Station

34. Trends in Cellular Radio Communications
Since 1989, there has been enormous activity throughout the world to develop personal wireless systems that combine the network intelligence of today’s PSTN with modern digital signal processing and RF technology.
The concept, called Personal Communication Services (PCS), originated in the United Kingdom when three companies were given spectrum in the 1800 MHz to develop Personal Communication Networks (PCN) throughout Great Britain.
Presently, field trials are being conducted throughout the world to determine the suitability of various modulation; multiple-access, and networking techniques for future PCN and PCS systems.
PCN refers to a wireless networking concept where any user can make or receive calls, no matter Where they are, using a light-weight, personalized communicator.
PCS refers to new wireless systems that incorporate more network features and are more personalized than existing cellular radio systems, but which do not embody all of the concepts of an ideal PCN.

35. Trends in Cellular Radio Communications (cont’d)
Indoor wireless networking products are steadily emerging and promise to become a major part of the telecommunications infrastructure within the next decade.
An international standards body, IEEE , is developing standards for wireless access between computers inside buildings.
The European Telecommunications Standard Institute (ETSI) is also developing the LAN standard for indoor wireless networks.
Before the end of the 20th century products will allow users to link their phone with their computer within an office environment, as well as in a public setting, such as an airport or train station.
A worldwide standard, the Future Public Land Mobile Telephone System (FPLMTS) — renamed International Mobile Telecommunication 2000 (IMT-2000) in mid-1995 — is being formulated by the International Telecommunications Union (ITU) which is the standards body for the United Nations, with headquarters in Geneva, Switzerland.

36. Trends in Cellular Radio Communications (cont’d)
The technical group TG 8/1 standards task group is within the ITU's Radiocommunications Sector (ITU-R).
ITU-R was formerly known as the Consultative Committee for International Radiocommunications (CCIR).
TG 8/1 is considering how future PCNs should evolve and how worldwide frequency coordination might be implemented to allow subscriber units to work anywhere in the world.
FPLMTS (now IMT-2000) is a third generation universal, multi-function, globally compatible digital mobile radio system that would integrate paging, cordless, and cellular systems, as well as low earth orbit (LEO) satellites, into one universal mobile system.
A total of 230 MHz in frequency bands 1885 MHz to 2025 MHz and 2110 MHz to 2200 MHz has been targeted by the ITU's 1992 World Administrative Radio Conference (WARC). The types of modulation, speech coding, and multiple access schemes to be used in IMT-2000 are yet to be decided.

37. Trends in Cellular Radio Communications (cont’d)

38. Trends in Cellular Radio Communications (Cont’d)

39. Different Service, Different Technology
1G 1980s
2G 1990s 3G
Analog
Digital
IMT-2000
AMPS
GSM
UMTS
CDMA
WCDMA
TACS
IS-95
Technologies
drive
Demands
drive
cdma
TDMA
NMT
2000
IS-136
Others
TD-SCDMA
PDC
3G provides compositive services for both operators and subscribers

40. To solve the fundamental technical defects of the analog systems, the digital mobile communication technologies emerged and the second generation mobile communication systems represented by GSM and IS-95 came into being in the middle of 1980s. The typical examples of the second generation cellular mobile communication systems are the DAMPS of USA, the IS-95 and the European GSM system.
The GSM (Global System for Mobile Communications) is originated from Europe. Designed as the TDMA standard for mobile digital cellular communications, it supports the 64 kbps data rate and can interconnect with the ISDN. It uses the 900 MHz band while the DCS1800 system uses the 1800 MHz band. The GSM system uses the FDD and TDMA modes and each carrier supports eight channels with the signal bandwidth of 200 kHz.
The DAMPS (Digital Advanced Mobile Phone System) is also called the IS-54 (North America Digital Cellular System). Using the 800 MHz bandwidth, it is the earlier of the two North America digital cellular standards and specifies the use of the TDMA mode.
The IS-95 standard is another digital cellular standard of North America. Using the 800 MHz or 1900 MHz band, it specifies the use of the CDMA mode and has already become the first choice among the technologies of American PCS (Personal Communication System) networks.

41. Multiple Access Technology
WCDMA RAN Fundamental
Multiple Access Technology
Frequency
Time
Power
FDMA
Frequency
Time
Power
TDMA
Power
Time
CDMA
Frequency
Frequency Division Multiple Access means dividing the whole available spectrum into many single radio channels (transmit/receive carrier pair). Each channel can transmit one-way voice or control information. Analog cellular system is a typical example of FDMA structure.
Time Division Multiple Access means that the wireless carrier of one bandwidth is divided into multiple time division channels in terms of time (or called timeslot). Each user occupies a timeslot and receives/transmits signals within this specified timeslot. Therefore, it is called time division multiple access. This multiple access mode is adopted in both digital cellular system and GSM.
CDMA is a multiple access mode implemented by Spreading Modulation. Unlike FDMA and TDMA, both of which separate the user information in terms of time and frequency, CDMA can transmit the information of multiple users on a channel at the same time. The key is that every information before transmission should be modulated by different Spreading Code to broadband signal, then all the signals should be mixed and send. The mixed signal would be demodulated by different Spreading Code at the different receiver. Because all the Spreading Code is orthogonal, only the information that was be demodulated by same Spreading Code can be reverted in mixed signal.
Confidential Information of Huawei. No Spreading Without Permission

42. Frequency Division Multiple Access means dividing the whole available spectrum into many single radio channels (transmit/receive carrier pair). Each channel can transmit one-way voice or control information. Analog cellular system is a typical example of FDMA structure.
Time Division Multiple Access means that the wireless carrier of one bandwidth is divided into multiple time division channels in terms of time (or called timeslot). Each user occupies a timeslot and receives/transmits signals within this specified timeslot. Therefore, it is called time division multiple access. This multiple access mode is adopted in both digital cellular system and GSM.
CDMA is a multiple access mode implemented by Spreading Modulation. Unlike FDMA and TDMA, both of which separate the user information in terms of time and frequency, CDMA can transmit the information of multiple users on a channel at the same time. The key is that every information before transmission should be modulated by different Spreading Code to broadband signal, then all the signals should be mixed and send. The mixed signal would be demodulated by different Spreading Code at the different receiver. Because all the Spreading Code is orthogonal, only the information that was be demodulated by same Spreading Code can be reverted in mixed signal.

43. Duplex Technology FDD TDD UL DL USER 2 USER 1 DL USER 2 UL USER 1
WCDMA RAN Fundamental
Duplex Technology
FDD
Time
Frequency
Power UL DL
USER 2
USER 1
Time
Frequency
Power
TDD
USER 2
USER 1 DL UL
Confidential Information of Huawei. No Spreading Without Permission

44. 2G&2.5G Cellular Systems
Since the 2G mobile communication systems focus on the transmission of voice and low-speed data services, the 2.5G mobile communication systems emerged in 1996 to address the medium-rate data transmission needs.
2G systems were originally designed for voice communication and low-rate data communication. They use “circuit-switched” data modems that limit users to data rate of a single voice channel (~10 kbps). Examples for 2G data comm. applications: SMS of GSM.
In an effort to “upgrade” 2G standards to make it compatible for the increased data rates to support Internet applications (e.g. WAP) and multimedia services, 2.5G standards were introduced.
2.5G allows existing 2G equipment to be used with some hardware/software
add-ons at the base station and software upgrades on the mobile station.

45. The CDMA system has a very large capacity that is equivalent to ten or even twenty times that of the analog systems. But the narrowband CDMA technologies come into maturity at a time later than the GSM technologies, their application far lags behind the GSM ones and currently they have only found large-scale commercial applications in North America, Korea and China. The major services of mobile communications are currently still voice services and low-speed data services.
With the development of networks, data and multimedia communications have also witnessed rapid development; therefore, the target of the 3G mobile communication is to implement broadband multimedia communication.
The 3G mobile communication systems are a kind of communication system that can provide multiple kinds of high quality multimedia services and implement global seamless coverage and global roaming. They are compatible with the fixed networks and can implement any kind of communication at any time and any place with portable terminals.

46. 3G Cellular Systems
3G standards were developed to support demanding requirements of Internet/multimedia services. Target minimal data rate is 2Mbits/sec for fixed (indoor) and 144Kbits/sec for mobile (outdoor) environments.
International Telecommunication Union (ITU) initiated “International Mobile Telephone (IMT-2000)” plan with a vision for a single, ubiquitous wireless communication standard throughout the world.
There are many proposals that were submitted for IMT-2000 in Currently, two of these proposals, i.e. CDMA2000 and W-CDMA, take the lead. With major political and economic backing behind both camps (techno-politics!), it is now apparent that the hope for a single worldwide standard will not come true, at least within the 3G era.
The world’s first 3G commercial system was launched by SK Telecom (Korea) in October It is based on CDMA2000.
It is expected that CDMA2000 and W-CDMA based technologies will dominate the worldwide market. One exception is China who desires to craft its own wireless standard and initiates/supports TD-SCDMA.

47. Non-Cellular Wireless Access Systems
Wireless Local Area Networks (WLANs)
License-free, low-power, short-range data communications
WLANs provide license-free, low-power short-range data communications, which facilitates internet connection and private computer communications at the workplace and other designated areas such as coffee shops, airports, libraries, etc. as well as for home-networking.
Although the IEEE WLAN standard body was established in 1987, WLAN did not get popular until recently. The widescale acceptance of Internet combined with increasing use of laptop and other mobile computing devices such as PDAs has caused WLAN to get further momentum.
WLANs operate in the 2.4 GHz ISM (Industrial, Scientific and Medical) band. These are the same unlicensed bands where cordless phones, baby monitors and Bluetooth devices operate.

48. Wireless Local Area Networks (WLANs)
License-free, low-power, short-range data communications
Current WLAN standards are based on IEEE a/b/g. Although the term “Wi-Fi” has been originally introduced to denote b, it is currently used as a generic term.
A new standard IEEE n (based on MIMO technology) is currently under development. Check for latest updates.

49. Wireless Metropolitan Area Networks (WMANs)
Last-mile brodband access
Fixed wireless access provides a reliable and inexpensive alternative to fiber optic for the “last mile”.
Unlike mobile cellular phone systems, fixed wireless access systems are able to take the advantage of time-invariant nature between the fixed transmitter and the fixed receiver.
Standardization efforts are centered around IEEE and ETSI-HiperMAN.
For updated information,
check

50. Wireless Personal Area Networks (WPANs)
Interdevice connection within the range of a person/home
The Bluetooth standard aims to unify the connectivity chores of appliances within the personal workspace of an individual. It operates in the unlicensed 2.4 GHz ISM band.
Bluetooth is an open standard that has been embraced by over 1000 manufacturers of electronic appliances. It provides an ad-hoc approach for enabling various devices to communicate with one another within a typical 10 meter range.
For further information, check

51. 4G Cellular Systems
The basic technology driver: Higher and higher data rates to support ever-increasing demands of end-users.
4G should not be seen as a linear extension of 3G cellular: Seamless service provisioning across a multitude of wireless systems/ platforms Heterogeneous networks.
A single, ubiquitous seamless cellular phone standard (if techno-politics allows): You will be able to use your cellular phone wherever you go all over the world.

52. The Main Features of Fourth Generation Technology
Faster and more reliable
100 Mb/s
Lower cost than previous generations
Multi-standard wireless system
Bluetooth, Wired, Wireless
OFDM used instead of CDMA
Potentially IEEE standard n
Most information is proprietary