cellular overview

7/30/2019 Cellular Overview

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BASIC CELLULAR OVERVIEW


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COURSE OUTLINE

Evolution of Wireless Communications System

Wireless Telecommunications Concept

Future Development of Wireless Communications

Telecommunication Standard Bodies

Definition of Terms


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Definition of Terms

Analog - Transmission of voice and images using electricalsignals. Analog mobile cellular systems include

AMPS, NMT and TACS.

Bandwidth - The range of frequencies available to be

occupied by signals.1. In analog systems it is measured in terms of Hertz (Hz).

2. In digital systems in bit/s per second (bit/s).

3. The higher the bandwidth, the greater the amount of

information that can be transmitted in a given time.


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Definition of Terms

Base Station - A radio transmitter/receiver and antenna used inthe mobile cellular network.

Bluetooth - A radio technology that makes possible

transmitting signals over short distances between

mobile phones, computers and other devices.

Cell - The geographical area covered by a single base

station in a cellular mobile network.


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Definition of Terms

Cellular - A mobile telephone service provided by a networkof base stations, each of which covers one

geographical cell within the total cellular system

service area.

Channel - One of a number of discrete frequency ranges

utilized by a base station to transmit and receive

information from cellular terminals (such as

mobile handsets).

Coverage - Refers to the range of mobile cellular network,

measured in terms of geographical coverage orpopulation coverage.


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Definition of Terms

Digital - Representation of voice or other informationusing digits 0 and 1.

1. The digits are transmitted as a series of pulses.

2. Digital networks allow for higher capacity, greater functionality

and improved quality.

3. Digital cellular networks include GSM, CDMA and TDMA.


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Definition of Terms

FDMA - Frequency Division Multiple Access. A cellulartechnology that has been used in the first-

generation analog systems (i.e., AMPS, NMT &

TACS)

Frequency - The rate at which an electrical current alternates,usually measured in Hertz (Hz). It is also used to

refer to a location on the radio frequency

spectrum, such as 800,900 & 1800 MHz.


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Definition of Terms

Frequency reuse - The ability to use the same frequencies

repeatedly across a cellular system.

1. As each cell uses radio frequencies only within its boundaries,

the same frequencies can be reused in other cells not far away with a

limited possibility of interference.

2. The reuse of frequencies is the key concept that enables a

cellular system to handle a large amount of calls within a limited

number of channels.


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Definition of Terms

Hand-off - A central concept of cellular technology, enablingmobility for subscribers. It is a process by which

the MTSO passes a mobile phone conversation

from one radio frequency in one cell to another

radio frequency in another as a subscriber

crosses the boundary of a cell.

Hz - Hertz. The frequency measurement unit equal to

one cycle per second.

MTSO - Mobile Telephone Switching Office. A centralpoint to which base stations of cells in a cluster

are connected to, either by landlines or

microwave.


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Definition of Terms

Multimedia - The combination of various forms of media(texts, graphics, animation, audio, etc.) to

communicate information. The term also refers to

information products that include text, audio, and

visual content.

PSTN - Public Switched Telephone Network. The public

telephone network that delivers fixed telephone

service.

Roaming - A service allowing cellular subscribers to use theirhandsets on networks of other operators.


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Definition of Terms

TDMA - Time Division Multiple Access. A digital

technology that divides frequency into time slots.

Radiation - The outward flow of energy from any source inthe form of radio waves.

Telephony - The word used to describe the science of

transmitting voice over a telecommunications

network.


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Cellular Frequency Allocation

FREQUENCY CLASSIFICATION DESIGNATION

3-30 Hz

30-300 Hz Extremely Low Frequency ELF

300-3000 Hz Voice Frequency VF

3-30 KHz Very Low Frequency VLF30-300 KHz Low Frequency LF

300-3000 KHz Medium Frequency MF

3-30 MHz High Frequency HF

30-300 MHz Very High Frequency VHF

300-3000 MHz Ultra High Frequency UHF

3-30 GHz Super High Frequency SHF30-300 GHz Extremely High Frequency EHF

300-3000 GHz

Cellular

Spectrum!

The part of the radio spectrum from 300 to 3000 megahertz which

includes TV channels 14-83, as well as many land mobile and satellite

services.


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Wireless Telecommunications Concepts

Telecommunications

Any transmission, emission or reception of signs, signals, writing, images,

sounds or intelligence of any nature by wire, radio, optical or other

electromagnetic systems.

Wireless Communication

Any broadcast or transmission which can be received through microwave

or radio frequencies without the use of a cable connection

for reception.


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Principles of Cellular System

Four key components make up most cellular radio systems:

1. The cellular layout.

2. A carefully engineered network of radio base stations and

antennas.

3. Base station controllers which manage several base

stations at a time,

4. A mobile switch, which gathers traffic from dozens of cells

and passes it on to the public switched telephone network.


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Basic Cellular Diagram


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Basic Network Elements / Call Flow

MS or Mobile Station Antenna / Cellsite

Makes a CallA nearby cell site's

antenna picks up the call

from the mobile


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Base Station Controller Mobile Switching Center

The call is then routed through thebase station's transceiver. Several

base stations may be controlled

by a base station controller or

BSC

The MSC or MTSO gets

the call next. It routes the

call to the called party.



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HLR, VLR, AUC and EIR PSTN

The mobile switch queries severaldatabases before permitting a

call. The call is processed and routed

next to the telephone network at

large, also known as the Public

Switched Telephone Network.



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OMC

At all times an Operations andMaintenance Center monitors the

network.



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The area a base station covers is called a cell.

The spot where the base station and antennas are located

is called a cell site.

Viewed on a diagram, the small territory covered by each

base station appears like a cell in a honeycomb, hence the

name cellular.

Cell sizes range from sixth tenths of a mile to thirty miles in

radius for cellular (1km to 50km).



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Each base station uses carefully chosen frequencies to

reduce interference with neighboring cells.

Narrowly directed sites cover tunnels, subways and

specific roadways.

The area served depends on topography, population, and

traffic.

A base station hierarchy exists, with pico cells covering

building interiors, microcells covering selected outdoor

areas, and macrocells providing more extensive coverage

to wider areas.



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The macro cell controls the cells overlaid beneath it. A

macro cell often built first to provide coverage and smallercells built to provide capacity.



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Fundamental Features of a Cellular System


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Frequency Reuse

Frequency reuse distinguishes cellular from conventional mobile

telephone service, where only a few frequencies are used over a large

area, with many customer's competing to use the same channels.

One high powered transceiver covering large geographical areas.


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Frequency Reuse

Cellular relies on a distributed network of cells, each cell site

with its own antenna and radio equipment, using low power to

communicate with the mobile.

In each cell the same frequency sets are used as in other cells. But the

cells with those same frequencies are spaced many miles apart toreduce interference.

Thus, in a 21 cell system a single frequency may be used several

times.

The lone, important exception to this are CDMA systems. In those, the

same frequencies are used by every cell.


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Frequency Reuse

Each base station controls a mobile's power output, keeping it low

enough to complete a circuit while not high enough to skip over to

another cell.

Several low powered transceiver covering the same large

geographical areas.


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The Frequency Reuse Concept

Each honeycomb/ hexagon represents a cell.

Each number represents a different set of channels or

paired frequencies.

A cellular system separates each cell that shares the same

channel set. This minimizes interference while letting the

same frequencies be used in another part of the system.

A channel is a pair of frequencies, one for transmitting on

and one for receiving.

Frequencies are described by their place in the radio

spectrum, such as 800mHZ, whereas channels are

described by numbers, such as channels 334 through 666.


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Cell Splitting / Sectorization

Splitting a single cell does not mean that it is broken into

smaller cells, but rather into sectors.

A previously omni-directional base station antenna,

radiating equally in all directions, is replaced by several

directional antennas on the same tower.

This "sectorizing" divides the previously homogeneous

cell into 3 or 6 distinct areas (120 and 60 degrees around

the site respectively). Each sector gets its own frequencies to operate on.


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Cell splitting is done to increase traffic capacity

Cell Splitting / Sectorization


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Handoff occurs when the mobile network automatically transfers a call

from a radio channel in one base station to another radio channel in an

adjacent base station as the subscribers crosses into the adjacent base

stations cell area.

Handoff ( Mobility )


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Modulation Technique

Frequency Modulation (FM)

Radio transmission covering 88-108 MHz on the broadcast

band. FM is less susceptible to interference than AM

broadcasting, and is also used in other frequency bands fortwo-way communications in land mobile and marine

services.


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Transmission Mediums

Microwave Radio Copper Cable


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Transmission Mediums

Satellite Fiber optic cables


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Multiplexing Concept

Cellular Access Methods

Power

Frequency

Time

FDMA

Frequency

Power Time

TDMA

FrequencyCDMA

PowerTime


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Cellular Applications and Value Added Services

Location

Personalization

Preference Selection

Prioritization ofinformation andcontent

Analytic Capability

Bandwidth On Demand


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Evolution of Wireless Communications System

Global Perspective

Philippine Scenario


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AMPS

TACS

NMT

Time

Mobility

1G

Global Perspective

Generation

Technologies

MotivatingFactor

TDMA

GSM

CDMA

IS-95A

Roaming

Capacity/

Quality

2G

GPRS

EDGE

CDMA

IS-95B

MediumData

Speed

2.5G

WCDMA

CDMA2000

More

Capacity

Higher

Data Speed

3G


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89 90 93 95 96 97 98 9994 0091 01 200392 YY

A A

islacom

A G G T C G G 3G

TDMA

Philippine Scenario


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Future Development of Wireless Communications

Industry Convergence

Migration Path

Emerging Wireless Applications and Services


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IP

COMPUTER (I.T.)MEDIA

TELECOMMUNICATION

- streaming audio- video on demand

- interactive video services

- TV/Radio / Data contribution

& distribution

- internet access- electronic mail

- real time images

- multimedia

- mobile computing

- ISDN services

- video telephony

- wideband data services

Mobility

(High Speed Services)

Mobility

(Wideband Services)

Mobility

(Personal Services)

Industry Convergence


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IS-95A IS-95B

GSM GPRS

CDMA2000 1x

CDMA2000 x1EV

EDGE

WCDMA

1995 1999 2000 2001 2002 2003 2004

CDMA

14.4K

9.6K

64K 384K

2Mbps

Data Only 115K

384K

Data Only 2.4 Mbps

Migration Path


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Voice vs.

Emerging Wireless Applications and Services


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Telecommunication Standard Bodies

ITU - International Telecommunications Union. The

worldwide policy, spectrum regulation andstandardization body in telecommunications

operating under the auspices of the United Nations.

NTC - National Telecommunications Commission. An

agency who handles the policies, rules and

regulations of Philippine Telecommunications.

ATO - Air Transportation Office

Local Government

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