Wireless communication for 8th sem EC VTU students

Wireless Communication: Unit 1- Introduction To Wireless Telecommunication System & Networks

Prof. Suresha V, Dept. Of E&C E. K V G C E, Sullia, D.K-574 327

UNIT-1

Introduction to Wireless Telecommunication Systems and Networks

Learning Objectives

Discuss the general history and evolution of wireless radio technology.

Explain the basic cellular radio concept.

Discuss the evolution of modern telecommunications infrastructure.

Discuss the structure and operation of the PSTN, PDN and the SS7 Network.

Explain the basic structure of Broadband Cable TV systems.

Explain the basic concept and structure of the Internet.

Discuss the OSI model and how it relates to network communications.

Discuss wireless network applications and the future of this technology

Discuss the concept of the different generations of wireless cellular systems.

Explain the basic operations and structure of a 1G cellular system.

Explain the difference between 1G, 2G, and 2.5G cellular systems.

Discuss the different subscriber services available over 2G mobile systems.

Discuss the characteristics of 3G wireless mobile systems.

Explain the concept of 4G wireless.

Explain the function of standards bodies.

1.1 The History and Evolution of Wireless Radio Systems

Some History

o Ancient Systems uses Smoke Signals, Carrier Pigeons, etc to convey the information.

o Evolution of wireless radio system started at late 18th centuries.

o 1861: Maxwell at king’s college in London proposed mathematical theory of EM waves.

o 1872: Mahlon Loomis was in fact issued a U.S patent for a crude type of aerial wireless

telegraph.

o 1887: Hertz demonstrated the existence of EM waves using standing waves.

o Wireless born on 12th-Dec-1901 when Marconi sent a message (the signal was a

repetitive letter “s” in Morse code) from Cornwall, England to Signal Hill st.John’s,

Newfoundland. This was first wireless transmission across the Atlantic Ocean without the

aid of any modern electronic devices.



Evolution of Wireless Radio Systems:

1. Early AM Wireless Systems

2. The First Broadcast

3. Modern AM

4. The Development Of FM

5. The Evolution Of Digital Radio

6. The Cellular Telephone Concept

1. Early AM wireless systems*: (Jan-2015 - 8 Marks)

o Inventors are Maxwell, Hertz, Fessenden and Marconi.

o In early wireless transmitter L-C used to tune the output frequency of the spark-gap.

o Early wireless experiments to use balloons and kites to support long lengths of wire that

served as the antenna

o It is a crude early low-frequency transmitters

o Used AM modulation and in particular on-off keying (i.e. Morse code)

o Typical early wireless transmitter as shown in Figure 1-1

Figure 1-1: Typical early wireless transmitter

It emits a signal EM signal at spark gap discharge of either long or short duration depending on

the length of telegraph key was closed. This signal propagated through the air to a receiver located

at some distance from transmitter. The receiver detected signal was interrupted by an operator as

either a dot or dash depending upon its duration. This is now called AM or OOK modulation.



Limitations:

o Very low frequency transmitter

o Low power and unstable output

o Need bigger and high elevated antenna

o Modulated signal is very sensitive to noise

Remedies: The above limitations are overcome by using next generation wireless transmitters

o It is a RF high powered “poulsen” spark gap transmitter.

o It is used BASK and BFSK modulation techniques

2. The First Broadcast

o 1900s –Reginald Fessenden conducted an experiment. It includes

Continuous Wave, 50 Hz alternators built by general electric. More stable output than

spark gap.

This experiments send message on Christmas eve on 1906.it is the first ever radio

broadcast

o 1910s –US Navy started ship-to-ship and ship-to-shore radio communication

The sinking of the titanic on the night of April 14th ,1912 send the last message

through ship’s wireless operator

World war -1 was also major driver of the development of radio technology by the US

military

o 1920s – Short-wave radio development era. It includes Improved Vacuum tube

technology with high frequency operation.

o 1930s-1940s: TV, Radar and Vacuum tubes with ability to generate microwaves.

3. Modern AM

o It is Used for LF radio broadcasting like Low definition TV, Video broadcasting, CB radio,

Armature radio & other low profile services

o Here using QAM(phase amplitude) modulation techniques for high data rates at RF

frequencies

4. The development of FM

o Edwin Armstrong invented super heterodyne receiver 1910s.

o It worked on the principles of FM and PM in 1920s to 1930s.

o FM broadcasting becomes popular during the late 1960s.

o FM used by many public safety departments used for fleet communication.

o AMPS cellular telephone service an FM based system.

o Now FM is used for TV broadcasting sound, Radio, DTH services, cordless phones and

mobile radio services etc.

o FM is capable of much more noise immunity than AM, most popular modulation scheme.



5. The Evolution of Digital Radio

o 1936: AT&T built long distance N/W from copper wires stung on poles.

o 1936: First experimental broadband coaxial cable was tested.

o 1941: First operational L1 system was installed, that could handle 480 telephone calls.

o 1947: First microwave relay was system installed b/w Boston & New York.

o 1951: AT&T coast to coast microwave radio relay was placed.

o 1970: AT&T microwave relay system carried 70% of its voice traffic and 95% of its TV traffic.

o 1970-1980: Advances in microwave digital radio technology and digital modulation

technique for higher data rates.

6. The cellular telephone concept:

o It is evolved from mobile radio networks. It is primarily used in police dept. and law agencies.

o It is one-way radio systems operating at about 2 MHz, i.e. pagers.

o Basic cellular model as shown in Fig 1.2, it consists of high power transmitter covers larger

area, one user per channel and one cell serves complete one metropolitan area around 75

mile radius.

Fig 1.2 First Mobile Telephone System

Problem with Original Design

o Original mobile telephone system could only support limited users, congestion etc..

o With only one high power base station, user’s phones also needed to be able to transmit

at high powers (to reliably transmit signals to the distant base station).

o Car phones were therefore much more feasible than handheld phones, e.g., police car

phones.



Improved Design: The Core Idea of Cellular Concept

o AT&T proposed a core idea of cellular system.

o Instead of one base station covering an entire city, the city was broken up into cells, or

smaller coverage areas. Each of these smaller coverage areas had its own lower-power

base station. User phones in one cell communicate with the base station in that cell.

o Core cellular Principles: Small cells tessellate overall coverage area. User’s handoff as

they move from one cell to another. Use the Frequency reuse concept.

1.2 The Development of Modern Telecommunications Infrastructure

Basic function of wireless networks and systems connect the users to the two main public networks.

They are

1. Public Switched Telephone Network ( PSTN)

2. Public Data Network (PDN).

1. Public Switched Telephone Network (PSTN)

Overview of basic PSTN

o PSTN has evolved over time to become an almost entirely digital network. AT&T shaped

present-day telecommunication infrastructure.

o Infrastructure Description: The subscriber may be connected to within a local exchange or

company office (CO) in several different ways. Plain-old telephone service (POTS) the

subscriber may be connected through a local loop connection consisting of a pair of copper

wires.

o Working: In this case, dialing information (via DTMF or traditional rotary dialing) signals are

interpreted by the local exchange switch to set up the correct pathway or connection

through the switch to the desired called party. Call signaling information (dial tone, ringing

tone, call waiting tones etc) is sent to the called party and also sent back to the caller.



Two types of telephone call setup they are as follows:

1. Intraoffice call: Call between two subscribers connected to the same switch, shown in fig 1.3

the analog call propagated through pair of copper wire to a line card located at the switch. The

line card converts this analog signal to digital PCM signal, which is connected to line card of the

called party and reverse operation perform at the called party side. This operation called

“connection oriented” or “Circuit switched connection”.

Fig 2.1 : A PSTN intra-office call through the local exchange

2. Interoffice call: Call between two subscribers connected to the different switches but within

the same area, shown in figure 1.4. Interoffice connection might use T-1 carriers with copper

wire, OFC or SONET transport technology. This type of connection for long distance

communication with high data rates and multiplexed signal.

Fig 1.4: A PSTN interoffice call over an inter-exchange trunk link



Signaling System #7 (SS7)*: (Dec-2010)

o Signaling System No. 7 (SS7) is Data communications network standard. It is intended to be

used as a control and management network for telecommunication networks.

o SS7 provides call management, data base query, routing, and flow and congestion control

functionality for telecommunication networks.

o SS7 is specifically designed to support the functions of an ISDN.

o The early PSTN used “in band” signaling to set up and tear down interoffice and long

distance telephone calls.

o “In - band” signaling mean that the same facilities used to create an actual physical circuit for

the call to be sent over.

o A big disadvantage of this type of system is that a voice trunk (an inter-office facility) or

possibly many trunks had to be “seized “in order to do the signaling necessary to set up the

call.

o As the PSTN evolved into digital network, for economic reasons and for both efficiency and

security, an entirely separate network was created for the purpose of routing long distance

calls (calls between different exchanges or switches).

o This system of using separate facility to channel to perform the call routing function is known

as “out of band” signaling.

o The network elements of the SS7 system: SS7 is packet network shown in figure 1.5. It

consists of three main elements, they are:

1. Service Switching Point (SSP): It communicates with the voice switch via primitives and

creates signal units for communication over SS7 network. It converts signaling from voice switch

into SS7 format. It may send messages for data base queries through SS7 network. Voice

connection is established through look-up of routing tables and sending SS7 messages to

adjacent switches to request circuit connection.



Figure 1.5: The network elements of the SS7 system

2. Signal Transfer Point (STP) : It connect to service switching points (SSP) at the local exchange

and the interface with the local exchange switch or mobile switching center in the case of a

PLMN. SS7 messages travel from one SSP to another through the services of a Signal Transfer

Point (STP). It acts as a router for SS7 messages. It exchanges information in form of packets

related to either call connections or database queries. Other tasks of the STP include: Traffic

measurements for performance monitoring of the SS7 and telecommunication network and

Usage measurements for billing purposes. Three levels of STP

1. National STP: It exists in one network, no capability to convert messages into other

formats.

2. International STP: It provides SS7 based interconnection between national networks.

3. Gateway STP: It provides protocol conversion between a national and international

network or with other non-SS7 networks

3. Service Control Point (SCP): It is a computer used as a front-end to a database. SCP serves as

interface to a telephone company’s database. It stores

o Subscriber’s services, Routing of special service numbers

o Calling card validation and fraud protection, advanced intelligent network features for

service creation.



o The Public Data Network (PDN): PDN has been evolving for connectivity needs of business,

industry and government for the transport of high speed data over WANs. PDN includes

many different types of networks like SONET, ISDN, ATM, etc. The connection between

these networks might be through leased lines, fiber facilities or wireless radio links. Fig1.6 is

the one possible view of the PDN.

Figure 1.6: A depiction of the public data network

PDN can support many different types of service structures including.

1. Connection oriented services: They are Virtual circuits, Switched virtual circuits, Semi

permanent virtual circuits.

2. Connectionless oriented services: These services are used for data services over network.

o PDN use all the same technologies to construct, owned, and maintained by the user or

leased from the service provider.

o Virtual private data networks Use the public data network, maintaining privacy through the

use of a tunneling protocol that effectively conceals the private network data and protocol

information by encapsulating it within the public network transmission.

o Modern cellular telephone systems are currently in an evolutionary upgrade phase in an

effort to provide mobile subscribers with high speed connectivity to the PDN.



o Broadband Cable Systems (BCS): It is sophisticated and complex wideband networks

designed to deliver the following services Analog and Digital Video Signals (including HDTV),

Data (Internet , FAX etc….).The video content can come from local off-air television stations,

satellite feeds a distant station program content and local access facilities. The data service

typically connects to an Internet service provider (ISP) Telephone service connects to the

PSTN. The most important change in the legacy cable-TV plant is the migration to the two-

way hybrid fiber-coaxial cable system as shown in the figure 1.7.

Fig 1.7 Modern two way hybrid fiber coaxial cable TV system with fiber nodes

o The bandwidth of cable systems has been expanded to 870 MHz.

o Use of the frequency spectrum between 5 and 42 MHz allows for upstream data

transmission over the network

o Use the standardized cable modem (CM).

o Use the Data-Over-Cable-Service Interface Specification (DOCSIS) protocol has led to

multiple-vendor interoperability of cable modems located at the subscriber premise and

cable modem termination systems (CMTS) located at the cable service providers' network

centers or "head ends.“



The Internet: The Internet is the world's largest computer network. The structure of the

Internet is shown conceptually in Figure 1.8.

o Internet consists of thousands of computer networks interconnected by dedicated special-

purpose switches called routers.

o The routers are interconnected by a wide area network (WAN) backbone.

o This WAN backbone actually consists of several networks operated by National Service

Providers (NSP) (namely Sprint Link, UNet Technologies, internet MCI, etc.)

o These backbone 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.

o These national service provider (NSP) networks are interconnected to each other at

switching centers known as network access points (NAPs).

o Regional ISPs may tap into the backbone at either the NSP hubs or the NAPs.

o If an individual wants to connect to the Internet, he or she must usually go through an ISP.

o The user might connect to the ISP through the PSTN over a low-speed dial-up connection

using a modem that communicates with a "modem pool at the ISP, or through high-speed

cable-modem or ADSL (adaptive digital subscriber line) service. These services are usually

connected through the PDN to the ISP.



1.3 REVIEW OF THE SEVEN-LAYER OSI MODEL***: (July 2014-10M)

o It is a seven layer reference model. Developed by ISO.

o It describes how information moves from a software application in one computer to a

software application in another computer either over a simple network or through a

complex connection of networks or internetwork.

Layers Description**

Layer 7: Application Layer:

o It is closest to end user and it interfaces the users to the network.

o The end user can interact with network through software application that is running on the

computer.

o Some application layer implementations include: File Transfer Protocol (FTP) for file transfer

services, Simple Mail Transfer Protocol (SMTP) for electronic mail, Domain Name System

(DNS) for name server options, and Telnet for terminal services.

Layer 6-Presentation Layer:

o It provides a variety of conversion and coding functions that are applied to application layer

information/data. Some of the types of the coding and conversion that are performed are

Common data representation formats (standard multimedia formats), Conversion of

character representation formats (e.g., EBCDIC and ASCII converted to a syntax acceptable to

both machines),

o Perform common data compression schemes (e.g., GIF JPEJ, and TIFF), and

o Perform common data encryption schemes.



Layer 5 - Session Layer

o The session layer has the task of establishing, managing, and terminating communications

over the network.

o It performs dialogue control and synchronization.

Layer 4 - Transport Layer

o Perform process to process delivery

o Flow control manages the transmission between devices. Virtual circuits are set up and torn

down by this layer, error checking and correction is executed, and multiplexing may be

performed. Familiar transfer protocols are TCP and UDP.

Layer 3 - Network Layer:

o It performs routing and addressing.

o It creates, maintain, and release connections between the nodes in the network and also

manage addressing and routing of messages.

o A typical network layer implementation is Internet Protocol.

Layer 2 - Data Link Layer:

o It provides for the reliable transmission of data across a physical network connection or link.

o Different data link layer specifications define different network and protocol characteristics.

o Some of these characteristics include physical addressing, error notification, network

topology, sequencing of frames, and flow control.

o The data link layer divided into two sub layers: Logical Link Control (LLC) and Media Access

Control (MAC).

o The LLC sub layer of the data link layer manages communications over a single link of a

network.

o The MAC sub layer of the data link layer manages the protocol access to the physical

network medium.

Layer 1 – Physical Layer:

o It defines the electrical and mechanical specifications for the physical network link.

o Characteristics such as voltage levels, timing, physical data rates, maximum distance of

transmission, and physical connectors are all part of this specification for the wireless media.

o For fiber- optic media similar specifications exist for the type of network transport

technology employed (FDDI, ATM, SONET, etc).



1.4 Different Generation of Wireless Cellular Network*****

o Different Generation of Wireless Cellular technologies: 1G, 2G, 2.5G, 3G and 4G

1G CELLULAR SYSTEM **** (Jan 2015, July -2014, June-2010)

Features/ characteristics of 1G or AMPS System

o 1G (or 1-G) refers to the first-generation.

o It is a analog based voice oriented telecommunications standards

o AMPS (Advanced Mobile Phone system) were the popular 1G cellular system.

o Used analog frequency modulation FM).

o FDD used to achieve Duplexing.

o Type of multiple access is FDMA

o Channel B.W is 30Khz

o Frequency band is 824-894 MHz.

o Forward link and Reverse link separated by 45 MHz.

o ID numbers were assigned to the cellular system (SID) and mobile handset (MIN, SIM).

o The system standard also defines physical layer technical parameters such as max.

Permissible power level, Maximum out of band radiation level.

o The standard also prescribes the required protocol for system operations.

AMPS channels***

o AMPS spectrum divided into “A” and “B” bands both consists of 333 channels.

o AMPS channels are divided in to two sets of channels:

1. Traffic channels (TCH): It used for subscribers call.

2. Control channels (CCH): it used for system control functions.

o In “A” bands: The Channels 1-312 were Traffic channels (TCH). Channels 313-333 were

Control channels(CCH)

o In “B” bands: Channels 334-354 were Control channels (CCH). Channels 355-666 Traffic

channels (TCH).

AMPS system components and layout*** (July-2011)

Typical early AMPS cellular system shown in fig 1.9. It consists of the following components

1. Mobile Station(MS)

2. Radio Base Stations (RBS)

3. Communications links



4. Mobile telephone switching office(MTSO)

Figure 1.9: An early AMPS cellular system 1. Mobile Station (MS)

o It is a radio terminal in cellular system intended for use while in motion at unspecified

location but within the radio range.

o It is a hand held personal unit or installed in vehicles.

2. Radio Base station (RBS)

o It is often referred to as a base trans-receiver station (BTS). It provides coverage to

mobile subscriber over a particular geographical area.

o The base station is connected to the MTSO that is in turn connected to the PSTN.

o Together the base stations and the mobile stations provide the air interface that permits

subscriber mobility while connected to the PSTN.

3. Mobile Telephone Switching Office (MTSO)

o It is the heart of cellular system.

o It connects several BTS’s to PSTN.

o It performs the system control by switching the calls to the correct cell interfacing with

the PSTN. Monitoring the system traffic for billing performing various diagnostic services

and managing the operation of the entire network.

o A typical MSC handles 1, 00,000 cellular subscribers and 5000 conversion at a time.

Typical AMPS operations: Two section of operations (July-2011)

1. Typical operations performed by the mobile station (MS) and the base station (BS).

2. Second part of the operation that occurs between the base stations (BS) and the MTSO.

1. Basic Operations between MS and BTS:



o Two types of channels used by cellular system for their operations. They are control and

voice channels. These channels again divided into

(1). Voice : Forward Voice Channel (FVC)-It is from BS to MS

Reverse Voice Channel (RVC) -It is from MS to BS

(2). Control: Forward Control Channel (FCC) – It is from BS to MS

Reverse Control Channel (RCC) - It is from MS to BS

Figure below depicts the flow of information over voice and control channels

Fig 1.10: AMPS forward and Revere control and voice channels

o The AMPS Base Station (BS) uses the dedicated control channels send a variety of control

information to idle Mobile Stations (MS) within its cells.

o MS uses the RCC to communicate with the BS while in the idle mode.

o When the MS is engaged in a voice call, control and signaling information may be also be

transmitted over the traffic channel being used by the mobile and BS.

o Use of supervisory audio tones (SATs) transmits radio link status signaling information

over active voice channels.

o Three SAT frequencies are used: 5970 Hz, 6000 Hz, and 6030 Hz.

o These SAT tones give the base and mobile station ability to keep informed about each

other’s transmitting capabilities and to confirm the success or failure of certain mobile

operations.



o The base station periodically adds a SAT signal to the forward voice channel (FVC), thus

transmitting it to the mobile station.

o The mobile station acting like a transponder. Transmits the same frequency tone on the

reverse voice channel (RVC) back to the base station.

o Additionally a signaling tone (ST) of 10 kHz can be transmitted over a voice channel to

confirm orders and to signal various requests.

o To perform handoff operation by make use of both the SAT and ST signals.

o MS may transmit two types of messages over the reverse voice channel: Order

confirmation message or “called address message”.

More detail AMPS operation: Operation steps are

The FOCC transmits three data streams in time division multiplexed (TDM) format.

These three data streams are known as:

1. Stream A: message to mobile phones with the LSB of MIN equal to 0

2. Stream B: message to mobile phones with the LSB of MIN equal to 1

3. Busy idle stream: Indicates the current status of the reverse control channel.



o The use of stream A and B doubles the capacity of the control channel. Both control

channels operate at a 10 kbps data rate.

o FOCC Message format: Each FOCC message consists of one or more words. The types of

messages to be transmitted over the FOCC are:

1. Overhead messages: It is used to allow MS to perform initialization task , to update

MS with latest system parameters

2. Mobile station control messages: Two types of MS control messages can be sent by

the BS. The BS may either page the MS or send it to an order message that initiates a

particular operation

3. Control filler messages: It consists of one space filler word that is sent whenever

there is no other message to b sent on the FOCC.

o Some of these order messages are:

1. Alert order message: It is used to inform the mobile phone that there is an incoming

phone call.

2. Audit order message: It is used by the base station to determine if the mobile is still

active in the system.

3. Change power order message: it is used to alter the mobile’s RF output power.

4. Intercept order message: It is used to inform the user that a procedural error has

been made in placing a call.

5. Maintenance order message: It is used to check the operation of MS.

6. Send called address order message: Used to inform the mobile station that it must

send a message to the base station with dialed-digit information.

7. Stop alert order message: used to inform a mobile station that it must stop alerting

(ringing) the user.

8. Release order message: It is used to disconnect the call.

AMPS Security And Identification : Three ID numbers are used by the AMPS system:

1. Electronic Serial Number (ESN): The ESN is provided by the mobile phone’s manufacturer

and is not able to be easily altered.

2. System Identification Number (SID): SIDs is 15-bit binary numbers that are uniquely

assigned to cellular systems. These numbers are exchanged by the base and mobile station

to determine the status of the mobile-at home or roaming.

3. Mobile Identification Number (MIN): The MIN is a 34-bit binary number derived from the

mobile station’s 10-digit telephone number 24 bits are derived from the 7-digit local number.

10 bits are derived from the 3-digit area code.



o Summary of Basic AMPS Operations (***) :Operation includes:

1. AMPS mobile phone initialization

2. Mobile-to-Land Calls

3. Land-to-mobile and mobile-to-mobile calls

4. AMPs Network Operations

a. Amps network operations for a mobile originated call

b. AMPS Handoff operation

1. AMPS mobile phone initialization**: (July- 2013, Dec-2012)

Figure 1.11 AMPS mobile phone initialization

o Step1: When the mobile phone is first powered up, it goes through an Initialization process.

o Step2: Mobile phone scanning of the twenty-one dedicated control channels of the selected

service provider’s system.

o Step3: At the completion of step2, the mobile station will select the strongest control

channel to lock onto.

o Step4: The BS transmits a system parameter message that is used to update the data stored

by the mobile station about the cellular system.

If the mobile station cannot complete this task within 3 seconds, it will go to the

next strongest control channel signal and attempt to complete the task within a 3 sec



If unable to complete this task, the mobile will now return to step1 and enable itself

to use the other provider’s system.

o Step5: If the mobile station can complete steps 1-4, it moves on to the next task.

o Step6: It requires the MS to scan the paging channels (a control channel) of the system and

then lock onto the strongest paging channel.

o Within three seconds the mobile must receive an overhead message and verify certain

overhead information.

If this portion of the task cannot be completed, the mobile will go to the next

strongest paging cannel and attempt to complete the task within a 3 sec.

During this task the mobile will compare its home system ID (SID) to that of the

system ID delivered to it in the overhead message.

If the two system IDs are not the same, the mobile station knows that it is in a

roaming status and sets parameters to allow roaming operations to take place

between itself and the system that is attached to.

This action is necessary for the home system to be able to update the location of the

mobile phone.

If step 6 cannot be completed successfully. The MS returns to step1 and starts over.

o Step7: If steps 1 to 6 are complete, the mobile will identify or register itself with the network

by sending its ESN, MIN and SID numbers over the RECC.

o Step8: These ID numbers will be compared against a database at the MSC to validate the

mobile station’s ability to have roaming status.

o Finally: The base station sends a control message to the mobile to verify that the

initialization process has been completed after step 1 to 8 have been successfully executed

the mobile goes into an idle mode.

MS idle mode: Which it continually performs four ongoing tasks. The mobile phone must

execute each of the following four tasks every 46.3 milliseconds:

o Idle Mode Task #1: Respond to overhead information. The mobile must continue to receive

overhead messages and compare the received SID with the last received SID value. If the

most recently received SID is different, the MS enters the initialization procedure again. If

the SID value is the same, the mobile phone updates the received, if any, in the overhead

message.



o Idle Mode Task #2: Page matchup. The MS must monitor mobile station control messages

for page messages. If paged, the mobile will enter the system Access Task with a page

response.

o Idle Mode Task #3: Order the MS must monitor mobile station control messages for orders.

If an order is received, the mobile must respond to it.

o Idle Mode Task #4: Call initialization. When the mobile subscriber desires to initiate a call,

the system Access Task must be entered with an origination indication.

o Mobile-to-Land Calls***( Dec – 2012)

Figure below shows the steps needed to complete the tasks

Figure 1.12: AMPS Mobile originated call



Task description:

o Step #1: MS enters the System Access Task mode and then attempts to seize the RECC once

it becomes idle.

o Step #2: MS starts to transmit a service request message to the BS over the RECC. This

message will include MIN, ESN, and the phone number of the dialed party. After transmitting

a service request message to the BS the mobile station goes into an Await Message mode.

o Step #3: If the BS grants to service request it will send an initial voice Channel designation

message. The BS has also passed this information on to the network side (i.e., MSC). The

mobile will switch to the initial voice channel number provided by the BS . Other information

is also included in the base station message – the power level for the mobile and as SCC that

will designate what SAT tone to use on the traffic channel.

o Step #4: At this point, both the base and MSs have switched their communications to the

voice channels.

o Step #5: The BS sends a mobile control message over the FVC with the SAT Signal.

o Step#6: the MS responds to this message over the RVC with the SAT signal, which confirms

the radio link.

o Step #7: The MS now awaits completion of the call with the resultant signal coming from the

network (MSC).

o Step #8: Finally, the conversation takes place between the users.

o Step #9: To disconnect or complete the call, either the BS sends a release order message or

the mobile sends a signaling tone (ST) for 1.8 seconds at which point the base and mobile

station drop the voice channel radio link.



3. Land-to-mobile and mobile-to-mobile calls*** (Dec – 2012, July-2011)

Figure 1.13: AMPS Mobile terminated call

Task description:

o Step #1: MSC sends the ID of the MS to the BS.

o Step #2: The BS constructs a page control message. The ID information (ESN, MIN, and SID) is

added to the message as s the initial voice channel information.

o Step #3: The MS responds to the page by returning identification information over the RECC

in a page response message.

o Step #4: Another control message is sent over the FOCC by the BS that contains an SCC value

to inform the mobile as to the correct SAT to be used on the voice channel.

o Step #5: The base and mobile station both switch to the voice channels and alternately use

SAT tones to verify the radio link (step #6 and #7).

o Step #8: After this last handshake occurs, the traffic channel is then opened to conversation.



o Amps Network Operations****

1. AMPS network operations for a mobile originated call: (June-2010)

Consider a mobile-originated call shown before in figure 1.14.

Fig 1.14: AMPS network operations for a mobile originated call

o On the network side of the cellular system, there are messages exchanged between the BS

and the MSC and between the MSC and the PSTN. These messages are a combination of

IS-41 and SS7 messages.

o Toda TIA/EIA-41-D is the intersystem standard and TIA/EIA-634-B is used between the MSC

and the BS.

o Notice that after the handshaking between the MS, BS and MSC the PSTN is contacted.

o After the radio link between the mobile station, BS is confirmed, the telephone call is put

through to the called party over the PSTN.

o Several more operations are performed as handshaking between the called party and the

MS. If the called party answers, the alert ring-back signal is removed and a conversation

ensues on the forward and reverse voice channels.

o Either the called party or the MS may terminate the call.



2. Handoff operations*: (Dec-2010)

o Handover or Handoff refers to the process of transferring an ongoing call or data session

from one channel connected to the core network to another.

Handoff operations

o A handoff operation occurs in a cellular system when a MS moves to another cell.

o Consider that BS A is handling an active call from a MS within its area of coverage.

o However the MS is in transit and is moving from BS A and towards BS B’s coverage area.

o BS A constantly monitors the received signal power from MS. When the signal from MS goes

below a predetermined threshold level, BS A sends a handoff measurement request to the

MSC. The MSC requests that all the BSs that are able to receive the transmissions from the

specified MSs monitor its power level. It is determined that BS B is receiving the strongest

signal from the mobile.

o The MSC assigns a traffic channel (TCH) to BS B. Base station B responds and handover order

is sent from the MSC to BS A.

o BS A sends a handoff control signal to the MS with the necessary new channel information

and then mobile switches to new voice channel with its newly prescribed output power and

new SCC code.

o The mobile receives Base station B’s SAT and returns it. If everything goes well, the handoff is

successful.

http://en.wikipedia.org/wiki/Core_network



Other IG systems: Other first generation cellular other than AMPS are as follows

1. TACS (Total Access Communication System) cellular system)

2. NMT (Nordic Mobile Telephone) cellular system )

3. NTT (Nippon Telegraph and telephone ) Cellular system

1. TACS (Total Access Communication System) cellular system

It is developed by Motorola began its operation in UK.

It is operated in the frequency 800-MHz and 900-MHz bands.

Channel spacing of 25 kHz thus yielding a total of 1000 channels in the allotted spectrum.

Two UK service provider network evolved- Cellnet and Vodaphone.

TACS was upgraded shortly thereafter to Extended-TACS or E-TACS in the UK.

2. NMT (Nordic Mobile Telephone) cellular

The NMT 450 cellular system was another variation of AMPS.

It was first deployed in the Nordic countries of Denmark, Finland, Norway, and Sweden.

The first NMT systems operated in the 450 MHz band with channel spacing of 25 kHz.

An up banded NMT cellular system operating in the 900-MHz band in the year 1986 with a

narrower channel spacing of 12.5 kHz.

NMT cellular systems have since been deployed in approximately fifty countries worldwide.

3. NTT (Nippon Telegraph and telephone) Cellular

Introduced in Japan in December of 1979.

Operated in the frequencies of both 400-MHz and 800 MHz band.

Channel spacing of 25 kHz.

The system was not well received due to its high cost

The JTACS/NTACS (Japanese TACS/narrowband TACS) cellular system operated in the 800-

MHz and 900-MHz bands with 25-kHz and 12.5-kHz channel spacing, respectively.

These systems, developed by Motorola, were derived from the original TACS system.

Digital AMPS o It is an attempt to increase the capacity of the original AMPS cellular system.

o It allows for the continued use of the AMPS bandwidth and many of the AMPS procedures.

o D-AMPS cellular system is that second-generation system using TDMA technology is able to

use the same traffic channels as the first-generation AMPS system.

o D-AMPS/AMPS environment, a certain percentage of channels would be reserved for analog

traffic and the rest allocated to TDMA traffic.

o D-AMPS were published as interim Standard 54-B or simply IS-54-B.

o IS-54-B defined dual mode operation within the same 800-MHz cellular network all the

frequency specifications remained identical to the AMPS specification.



2G Cellular Systems***: (Jan 2015, July -2014, June-2010)

Features/ characteristics of 2G

o 2G is digital cellular system

o It uses digital modulation techniques.

o Introduce two major multiplexing schemes called TDMA and CDMA.

o Use digital modulation techniques to send digital control messages rather than SAT

tones.

o Use Digital encryption used for security and privacy for the mobile network subscriber.

o Use of digital encoding and decoding schemes.

o Use of error detection and correction codes for reliability.

o Two major 2G technologies and standards are GSM and CDMA.

GSM(Global System for Mobile communication)

o It is a 2G digital cellular system

o Began operation in late 1992.

o Approximately 72% of the world’s cellular customers subscribing this service.

o GSM technology uses TDMA to allow up to eight users per channel.

o Channels are spaced 200 kHz apart.

o Different Operating frequency bands.

The basic system uses frequencies in the 900-MHz band (GSM 900),

An up banded version was added at 1800 MHz (GSM 1800)

1900-MHz band was added in the United States for PCS service (GSM 1900).

o GSM service supported circuit-switched data rates of up to 9.6 kbps.

CDMA(Code Division Multiple Access)

o It is totally new digital technology known developed by Qualcomm Corporation

introduce in 1990s

o CDMA cellular systems use a digital modulation technique known as spread spectrum.

o It is also called for the next generation of wireless service

o CDMA air interface is IS-95.

o The first CDMA commercial network began operation in Hong Kong in 1995.

o CDMA systems have been used in both the cellular and PCS bands extensively in the

United States and throughout the rest of the world.

o TDMA or CDMA cellular systems, both control information and traffic share the same

radio channel.



o For CDMA systems, control information is carried by dedicated channel elements and traffic

is placed on any available traffic channel element.

o Channel elements (CEs) are individual transmitters that are all transmitting on the same

frequency simultaneously.

o CDMA has experienced very rapid growth and presently 13% of the world’s cellular

telephones use this technology

TDMA ( Time Division Multiple Access)

o TDMA system was developed for use at the 800-Mhz and then the 1900-Mhz PCS bands.

o Standard IS-136 is a TDMA based GSM. Today it is known as NA-TDMA.

o Currently, only 10% of the world’s cellular subscribers use this technology.

PDC (Personal Digital Communication)

o Japanese Personal Digital Communication (PDC) System in 1991.

o Using TDMA technology similar to Is-54 in both the 800-Mhz and 1500-Mhz bands

o PDC system supplied by Motorola was deployed starting in 1993.

o Currently, only 5% of the world’s cellular subscribers use PDC technology.

2.5g Cellular Systems

o Main limitation in 2G networks are slow data transmission.

o 2.5g uses protocol such EDGE (Enhanced Data over GSM Evolution) used for increase

data service.

o Different technologies to increase the data services are over 2g networks:

1. CDPD (Cellular Digital Packet Data)

2. HSCSD ( High Speed Circuit Switched Data)

3. GPRS ( General Packet Radio Service)

4. Packet data over CDMA and other technologies.

1. CDPD (Cellular Digital Packet Data):

o It originally designed to provide mobile packet data services on overlay AMPS system.

o It delivers low speed bursty packet data for nearer mobile station.

o Data rate is 9.6Kbps.



2. HSCSD (High-Speed Circuit-Switched Data):

o It is an increasing circuit-switched data rates on GSM networks.

o It is not a packet-switched data service.

o It yields data transfer rates up to 43.2 kbps in phase one and 64 kbps at phase two.

o This technology works by giving a mobile subscriber multiple timeslots out of standard

GSM TDMA frame with its eight timeslots.

3. GPRS (General Packet Radio Service)

o It is provide packet-switched data service that allows full mobility and wide area

coverage on GSM networks.

o GSM GPRS service is designed to provide data transfer rates up to 160 kbps.

o This technology is being deployed by NA-TDMA systems with data rates up to 45 kbps.

4. Packet Data over CDMA

o The CDMA system used an Inter Working Function (IWF) component that is necessary for

both circuit and packet data shown in the figure 1.17

Figure 1.17 CDMA interworking function node

o For circuit-switched data, the IWF supplies a modem connection to the PSTN and the

modem function is built into the mobile subscriber’s CDMA telephone.

o In CDMA systems (IS-95A), the maximum possible data rate for circuit-switched data rate

is 14.4 kbps.

o For packet data, the IWF provides the interface between the wireless system and the

external packet network with a maximum data rate of 14.4 kbps also.

o For 2.5 CDMA systems (IS-95B revision) higher data rates of 115.2 kbps are possible.

However, the real data throughput of the system is more in the range of 60 to 80 kbps.



o 3G Cellular Systems*** (Jan 2015, July -2014, July -2013, June-2010)

Features/ characteristics of 3G

o Support high-speed data transfer from packet networks

o Permit global roaming.

o Advanced digital services (i.e., Multimedia) and

o Work in various different operating environments (low through high mobility, urban to

suburban to global locations, etc.).

o These standards are being facilitated by the International Telecommunication Union

(ITU) and other regional bodies around the world as shown below.

o 3G Operating Environments: Below figure shows different operating environment to permit

global roaming



Table: 3G Characteristics by cell size and mobile speed****(Jan 2015)

Requirements for 3G systems:

o It must be able to support varying data rates by providing bandwidth on demand to the

subscriber.

o 3G subscriber devices (SDs) or end terminals (ETs) will be required to support multiple

technologies and frequency bands and have the ability to be reprogrammed by their home

cellular systems.

o Mobile phones have dual band and tri mode capabilities, can provide limited video

multimedia support, and have limited reprogramming features.

o 3G systems must be able to support multiple simultaneous connections, IP addressing and be

backward compatible with 2G networks.

Some popular 3G system

1. UMTS (Universal Mobile Phone system): (Dec-2012)

o It is a 3G GSM mobile phone systems.

o It uses present spectrum allocation and new frequency allocations on the 2-GHz band.

o It is also employing combinations of W-CDMA technology and either TTD or FDD based

CDMA technologies depending upon spectrum availability.

o The users TDD or FDD CDMA technology in conjunction with W-CDMA is to support the

different symmetrical and asymmetrical services.

o The NTT DoCoMo system uses a present Standard form of W-CDMA technology.



2. CDMA2000 : (Dec-2012)

o It is a 3G CDMA system

o This is the enhanced wideband version of CDMA.

o It is supported by the TIA and the CDMA Development group(CDG).

o The major features of cdma2000 are

1. Backward compatibility with CDMA IS-95B (a 2.5G technology)

2. Support for data rate of up to 2 Mbps.

3. support for multimedia services (i.e., Quality of Services QoS)

4. Support for advanced radio technologies.

o A unique feature of CDMA 2000 is that it supports several radio link bandwidths

depending upon required data rate.

1. Support data service at rates up to 144 Kbps in a mobile environment.

2. 1x EV-DO can support peak data rates of 2.4Mbps on the down link but only 153kbps

on the uplink thus application such as MP3 transfers and video and conferencing are

possible.

3. 1x EV-DV supports integrated voice simultaneous high-speed data packet multimedia

services at speed up to 3Mbps over an all-IP architecture radio access and core

network.

3. UWC-136/EDGE

o UWC-136 is the 3G proposal for the evolution of NA-TDMA cellular systems.

o It is developed by the United Wireless Communication Consortium (UWCC) that consists

of NA-TDMA manufacturers and service providers.

o It appears at this time that most NA-TDMA operators have opted to follow the GSM/EDG

route to 3G cellular.



4G CELLULAR SYSTEMS AND BEYOND( Jan 2015, July -2014, June-2010)

Some key Features of 4G: ***

o It is an IP based packed switched network.

o 4G networks are projected to provide speeds of 100 Mbps while moving and 1 Gbps

while stationary.

o High usability: anytime, anywhere, and with any technology.

o Support for multimedia and integrated services at low transmission cost.

o Smooth Handoff across heterogeneous networks.

o Seamless connectivity and global roaming across multiple networks.

o High quality of service for next generation multimedia support (real time audio, high

speed data, HDTV video content, mobile TV, etc.)

o Interoperability with existing wireless standards.

o It provides Dynamic bandwidth allocation, QoS and advanced Security

o It is Self organizing networks.

1.6 WIRELESS STANDARDS ORGANIZATIONS

o Need for standardization

Standardization is usually necessary for low-cost implementation and speed in bringing

services to the market.

Standards are necessary to ensure interoperability of equipment from different vendors

on a worldwide basis.

o Standards organizations usually consist of manufactures, service providers, and users

working together to promote physical characteristics for the anticipated telecommunications

requirements of the futures.

o Standards bodies are sponsored at the

1. Implementation level

2. National

3. Regional

4. International or global level.

1. Implementation Groups:

o This group also called “Standards Development Organization”.

o These groups generally consist of interested members from Manufacturing industry,

Academic world and government entities, Trade associations, Industry service providers,

and users.



o Some of the groups presently active in the wireless arena are

IEEE 802

CDMA development group

UMTS forum or committee.

TR-45 of the TIA

GSM association and so on.

2. Regional Organization:

o Regional standards organizations receive developed standards from implementation

groups.

o The regional organizations are task with approving the standard.

o Members of the regional organization will vote on the standard.

o Some of the more well-known regional organizations are

1. European telecommunications standards institute(ETSI)

2. Telecommunications Technology Committee(TTC)

3. Association of Radio Industries and Businesses(ARIB) in Japan

4. Telecommunications Technology Associations(TTA) in Korea

5. China Communications Standards Association(CCSA) in China

6. Committee T1-Telecommunications (ANSI-T1) in United States

7. EIA/TIA (Electronics Industries Alliance/Telecommunications Industry Association).

3. National organization

o The most well known national standards organization that exists in the United States is

the American National Standards Institute or ANSI.

o The TIA and EIA develop North American wireless standards and forward them to ANSI

for final approval as a national standard.

4. Global Organizations

o Global standards organizations receive recommendations from regional organizations.

o These worldwide organizations give the final approval for an international standard.

o There are three global standards organizations:

1. The international telecommunications union (ITU)

2. The international standards organization(ISO)

3. The international electrotechnical commission (IEC).

Prepared By: Prof.Suresha V, Professor, E&C Dept. KVGCE, Sullia.

Email:[email protected]. Cell No: +91 94485 24399.

Date: 28-02-2015.

Wireless communication for 8th sem EC VTU students

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