Chapters 1-2 Introduction to Wireless Communication Systems

Yimin Zhang, Villanova University 1

ECE 8708 Wireless Communications : Introduction to Wireless Communication Systems

Chapters 1Chapters 1--22

Introduction to Introduction to Wireless Communication SystemsWireless Communication Systems

Yimin Zhang, Ph.D.

Department of Electrical & Computer EngineeringVillanova University

http://yiminzhang.com/ECE8708



OutlinesOutlines

History

Examples of Mobile Radio Systems

Cordless Phone / Paging System / Cellular System

Cellular Process

To a mobile user / From a mobile user

Roaming

2G, 2.5G, 3G Technologies

Frequency Spectrum Allocations



• 1897:Marconi invented wireless concept

• 1960’s & 1970’s:Bell laboratories developed the cellular concept

• 1970’s:Development of highly reliable, miniature solid state radio frequency hardware

Wireless communication era was born

A little History and Evolution of Mobile RadioA little History and Evolution of Mobile Radio



Wireless Communications

• Cellular phone users 1984 - 25,0001994 - 16 million 1997 - 50 million 2000 - Number of wireless users = Number of wired users



Worldwide Cellular Telephone Subscribers



The first portable units were really big and heavy.



Cellular Technologies

Advanced Mobile Phone System. Developed by Bell Labs in the 1970s and first used commercially in the United States in 1983. It operates in the 800 and 1900 MHz band in the United States and is the most widely distributed analog cellular standard.

AMPS

Analog Cellular Technologies

Digital Cellular Technologies

Digital AMPS. Designed to use existing channels more efficiently, D-AMPS (IS-136) employs the same 30 kHz channel spacing and frequency bands(824-849 and 869-894 MHz) as AMPS. By using TDMA instead of frequency division multiple access or FDMA, IS-136 increases the number of users from 1 to 3 per channel. An AMPS/D-AMPS infrastructure can support either Analog AMPS phone or digital AMPS phones. (The Federal Communications Commission mandated that digital cellular in the U.S. must act in a dual-mode capacity with analog). Operates in the 800 MHz band and 1900 MHz.

D-AMPS(IS-54,

now rolled into

IS-136)




Personal Communications Service. The PCS frequency band in America is 1850 to 1990 MHz, encompassing a wide range of new digital cellular standards like N-CDMA and GSM 1900. Single-band GSM 900 phones cannot be used on PCS networks. PCS networks operate throughout the USA.

PCS

Global System for Mobile Communications. The first European digital standard, developed to establish cellular compatibility throughout Europe. Its success has spread to all parts of the world and over 80 GSM networks are now operational. It operates at 900 and 1800 MHz in many parts of Europe and in England. Works at 1900 MHz in some parts of the United States. TDMA based.

GSM




Code Division Multiple Access. Developed by Qualcomm characterized by high capacity and small cell radius. It uses the same frequency bands as AMPS and supports AMPS operation, employing spread-spectrum technology and a special coding scheme. It was adopted by the Telecommunications Industry Association (TIA) in 1993.

CDMA


Wide ranging wireless specification involving IS 95, IS-96, IS-98, IS-99, IS-634 and IS-41.AT&T, Motorola, Lucent, ALPS, GSIC, Prime Co, Qualcomm, Samsung, Sony, US West, Sprint, Bell Atlantic, Time Warner are sponsors.

cdmaOne




In 1990 North American carriers faced the question -- how do we increase capacity? -- do we pick an analog or digital method? The answer was digital. In March 1990 the North American cellular network incorporated the IS-54B standard, the first North American dual mode digital cellular standard. This standard won over Motorola's Narrowband AMPS or NAMPS, an analog scheme that increased capacity by cutting down voice channels from 30KHz to 10KHz. IS-54 on the other hand increased capacity by digital means: sampling, digitizing, and then multiplexing conversations, a technique called TDMA. This method separates calls by time, placing parts of individual conversations on the same frequency, one after the next. It tripled call capacity.

Using IS-54, a cellular carrier could convert any of its systems' analog voice channels to digital. A dual mode phone uses digital channels where available and defaults to regular AMPS where they are not. IS-54 was, in fact, backward compatible with analog cellular and indeed happily co-exists on the same radio channels as AMPS. No analog customers were left behind; they simply couldn't access IS-54's new features. CANTEL got IS-54 going in Canada in 1992. IS-54 also supported authentication, a help in preventing fraud. IS-54, now rolled into IS-136, accounts for perhaps half of the cellular radio accounts in this country.

North America Goes to Digital: IS-54



Europeans saw things differently. No new telephone system could accommodate their existing services on so many frequencies. Theydecided instead to start a new technology in a new radio band. Cellular structured but fully digital, the new service would incorporate the best thinking of the time. They patterned their new wireless standard after landline requirements for ISDN, hoping to make a wireless counterpart to it. The new service was called GSM.

GSM first stood for Groupe Speciale Mobile, after the study group that created the standard. It's now known as Global System for MobileCommunications, although the "C" isn't included in the abbreviation.

The Rise of GSM



Key Specifications of 2G Technologies



Upgrade Paths



2.5G and 3G Data Communication Standards




• Garage door openers

• Remote controllers for home entertainment

• Cordless telephones

• Hand-held walkie-talkies

• Pagers/beepers

• Cellular telephones



trans-ceiver<1 GHzmoderatehighhighhighCellular

phone

trans-ceiver

<100 MHzlowmoderatelowlowCordless

phone

receiver<1 GHzlowlowhighhighPaging system

trans-mitter

<100 MHzlowlowlowlow

Garage door opener

trans-mitterinfra-redlowlowlowlow

TV remote control

Function-ality

Carrier frequency

Hardware cost

Com-plexity

Required infra-

structureCoverage

rangeService

Mobile Communication Systems - Mobile Station



trans-ceiver<1 GHzhighhighhighhighCellular

phone

trans-ceiver

<100 MHzmoderatelowlowlowCordless

phone

<1 GHzhighhighhighhighPaging system

receiver<100 MHzlowlowlowlow

Garage door opener

infra-redlowlowlowlowTV remote control

Function-ality

Carrier frequency

Hardware cost

Com-plexity

Required infra-

structureCoverage

rangeService

trans-mitter

receiver

Mobile Communication Systems - Base Station



... Examples of Mobile Radio Systems

• Mobile – Describes a radio terminal attached to a high speed mobile platform (e.g., A cellular phone in a fast moving vehicle).

• Portable – Describes a radio terminal that can be hand-held and used by someone at walking speed (e.g., cordless telephone).

• Subscriber – Mobile or portable user.

• Base stations – Link mobiles through a backbone network.



Types of Mobile Radio Transmission Systems

• Simplex – Communication is possible only in one direction, (e.g., paging systems).

• Half Duplex – Two way communication, but uses the same radio channel for both transmission and reception. User can only transmit or receive information.

• Full Duplex – Simultaneous two-way radio transmission and reception between subscriber and base station. – Two simultaneous but separate channels (FDD) or

– Adjacent timeslots on a single radio channel (TDD)



Cordless Telephone Systems

• Full duplex communication

• Few hundred meters

Fixed Port

(BaseStation)

wirelesslinkPublic

Switched Telephone Network(PSTN) cordless

handset



Paging Systems

Paging systems are communication systems that send brief messages to a subscriber...– Numeric messages

– Alpha-numeric message

– Voice message

– News headlines

– Stock quotes

– Faxes

Paging System Coverage Areas– 2 to 5 km

– Within individual buildings

– Worldwide coverage



Satellite link

Paging System: Wide Area System

Landline link

Landline link

City 1: Paging terminal

City 2: Paging terminal

City N: Paging terminal

Pagingcontrolcenter

PSTN

The paging control center dispatches pages received from the Public Switched Telephone Network (PSTN) throughout several cities at the same time.



Cellular System

Base stations (towers) provide radio access between mobile users and Mobile Switching Center (MSC).

Mobile Switching Center PSTN



FVCFVCRVCRVC

FCCFCCRCCRCC

Base Station - Mobile Network

Forward Voice Channel

Reverse Voice Channel

Forward Control Channel

Reverse Control Channel



Functions of Cellular System

• Provides wireless connection to the PSTN for any user location within the radio range of the system.

• High capacity is achieved: – by limiting the coverage of each base station transmitter to a small

geographical area called a Cell, and

– by the same radio channels being reused by another base station located some distance away – Frequency reuse.

• Switching system, called handoff, enables call to proceed uninterrupted when the user moves from one cell to another.

• Typical MSC handles 100,000 cellular users and 5,000 simultaneous conversations at a time.



IncomingTelephone

Call to Mobile X

IncomingTelephone

Call to Mobile X

3, 73, 7

PSTNPSTN

Mobile XMobile X

Mobile Switching

Center

2, 62, 6

55

44

Step 1Step 1

Base StationsBase Stations

Telephone Call Made To Mobile User



Brief Outline of Cellular Process: Telephone Call Placed to a Mobile User




Step 1 – The incoming telephone call to Mobile X is received at the MSC.

Step 2 – The MSC dispatches the request to all base stations in the cellular system.

Step 3 – The base stations broadcast the Mobile Identification Number (MIN), telephone number of Mobile X, as a paging message over the FCC throughout the cellular system.

Step 4 – The mobile receives the paging message sent by the base station it monitors and responds by identifying itself over the reverse control channel.

Step 5 – The base station relays the acknowledgement sent by the mobile and informs the MSC of the handshake.

Step 6 – The MSC instructs the base station to move the call to an issued voice channel within in the cell.



Step 7 – The base station signals the mobile to change frequencies to an unused forward and reverse voice channel pair.

At the point another data message (alert) is transmitted over the forward voice channel to instruct the mobile to ring.

Now the call is in progress. The MSC adjusts the transmitted power of the mobile and changes the channel of the mobile end and base stations in order to maintain call quality.




Telephone Call Placed by Mobile X

Telephone Call Placed by Mobile X

PSTNPSTN

Mobile Switching

Center

22

11

33

Telephone Call Placed by Mobile







Step 1 – When a mobile originates a call, it sends the base station its telephone number (MIN), electronic serial number (ESN), and telephone number of called party. It also transmits a station class mark (SCM) which indicates what the maximum power level is for the particular user.

Step 2 – The cell base station receives the data and sends it to the MSC.

Step 3 – The MSC validates the request, makes connection to the called party through the PSTN and validates the base station andmobile user to move to an unused forward and reverse channel pair to allow the conversation to begin.



Roaming

• All cellular systems provide a service called roaming.

This allows subscribers to operate in service areas other than the one from which service is subscribed.

• When a mobile enters a city or geographic area that is differentfrom its home service area, it is registered as a roamer in the new service area.

• Periodically, the MSC issues a global command over each FCC in the system, asking for all mobiles which are previously unregistered to report their MIN and ESN over the RCC for billing purposes.

• If a particular mobile user has roaming authorization for billing purposes, MSC registers the subscriber as a valid roamer.



Frequency Spectrum for US Cellular Radio ServiceChannel Center Frequency Number (MHZ)

1 ≤ N ≤ 799 .03 N + 825991 ≤ N ≤ 1023 .03 (N – 1023) + 825

1 ≤ N ≤ 799 .03 N + 870 991 ≤ N ≤ 1023 .03 (N – 1023) + 870

Channels 800-990 are unused.





OutlinesOutlines

History


Cordless Phone / Paging System / Cellular System

Cellular Process

To a mobile user / From a mobile user

Roaming

2G, 2.5G, 3G Technologies

Frequency Spectrum Allocations

Chapters 1-2 Introduction to Wireless Communication Systems

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