TOWER TECHNICIAN

Presented By:

Mr. NIMAY CHANDRA GIRI

girinimay1@gmail.com

CONTENTE

Objective

Introduction

GSM System & Architecture

Network identities

MS & BTS

Architecture of BTS with configuration

Antenna types & configurations

Different pole types antennas

Tilt

OBJECTIVE

To understand details about BTS system in GSM

system. Different types of Antennas used in the

market. Functional structure of BTS & different

parts of it.

MIMO & LTE Antennas used.

INTRODUCTION

A cell site or cell tower is a cellular telephone

site where antennae and electronic

communications equipment are placed, usually on

a radio mast, tower or other high place, to create a

cell (or adjacent cells) in a cellular network.

Frequency reuse – same frequency in

many cell sites

Cellular expansion – easy to add new cells

Handover – moving between cells

Roaming- between networks

BRIEF HISTORY

First telephone (photo phone) – Alexander Bell, 1880

The first car mounted radio telephone – 1921

1946 – First commercial mobile radio-telephone service by Bell and AT&T in Saint Louis, USA. Half duplex(PTT)

1973 – First handheld cellular phone – Motorola. 1982 „Groupe Spécial Mobile” is created within CEPT

(Conférence Européenne des Postes et Télécommunications) 1987 Main Radio transmission techniques are chosen,

based on prototype evaluation (1986) 1989 GSM becomes an ETSI technical committee 1990 The Phase I GSM900 specification are frozen

DCS1800 adaptation starts 1991 First systems are running

DCS 1800 specifications are frozen 1992 All major European GSM 900 operators begin

commercial operations (2G) 2000 3G system comes in to market. 2010 4G system comes in to market.

GLOBAL SYSTEM FOR MOBILE

COMMUNICATION

GSM is a standard developed by the European Telecommunications StandardsInstitute (ETSI) to describe protocols for second-generation (2G) digital cellularnetworks used by mobile phones. As of 2014 it has become the default globalstandard for mobile communications - with over 90% market share, operating inover 219 countries and territories.

2G networks developed as a replacement for first generation (1G) analogcellular networks, and the GSM standard originally described a digital, circuit-switched network optimized for full duplex voice telephony. This expandedover time to include data communications, first by circuit-switched transport,then by packet data transport via GPRS (General Packet Radio Services)and EDGE (Enhanced Data rates for GSM Evolution or EGPRS).

Subsequently, the 3GPP developed third-generation (3G) UMTS standardsfollowed by fourth-generation (4G) LTE Advanced standards, which do notform part of the ETSI GSM standard.

GSM Functions Transmission.

Radio Resources management (RR).

Mobility Management (MM).

Communication Management (CM).

Operation, Administration and Maintenance (OAM).

COMPARED TO FIXED NETWORK

GSM ARCHITECTURE

Transcoder is a device that takes 13 KBPS

speech data and multiplexes four of them into

standard 64 Kbps data.

NETWORK IDENTITIES

IMEI (International Mobile Equipment Identity)

MSISDN (Mobile Station ISDN Number)

IMSI (International mobile subscriber Identity)

TMSI (Temporary Mobile subscriber Identity)

MSRN (Mobile Station Roaming Number)

MOBILE STATION (MS)A Mobile Station consists of two main elements:The mobile equipment or terminal.There are different types of terminals distinguished principally by their power and application:The `fixed' terminals are the ones installed in cars. Their maximum allowed output power is 20

W.The GSM portable terminals can also be installed in vehicles. Their maximum allowed output

power is 8W.The handhels terminals have experienced the biggest success thanks to the weight and volume,

which are continuously decreasing. These terminals can emit up to 2 W. The evolution oftechnologies allows to decrease the maximum allowed power to 0.8 W.

The Subscriber Identity Module (SIM).

The SIM is a smart card that identifies the terminal. By inserting the SIM card into the terminal,

the user can have access to all the subscribed services. Without the SIM card, the terminal

is not operational. SIM has microprocessor and memory, IMSI,

Authentication Key, Ki

Security Algorithms:kc,A3,A8

PIN & PUK

Function of MS:

Voice and data transmission & receipt

Frequency and time synchronization

Monitoring of power and signal quality of the surrounding cells

Provision of location updates even during inactive state

THE BASE STATION SUBSYSTEM (BSS)

The BSS connects the Mobile Station and the NSS. It is incharge of the transmission and reception. The BSS can bedivided into two parts:

The Base Transceiver Station (BTS) or Base Station.

The BTS corresponds to the transceivers and antennas usedin each cell of the network. A BTS is usually placed in thecenter of a cell. Its transmitting power defines the size of acell. Each BTS has between one and sixteen transceiversdepending on the density of users in the cell.

The Base Station Controller (BSC).

The BSC controls a group of BTS and manages their radioresources (up to 100 BTSs). A BSC is principally in chargeof handovers, frequency hopping, exchange functions andcontrol of the radio frequency power levels of the BTSs .

BASE TRANSCEIVER STATION (BTS) OR

BASE STATION (BS)

Provides the radio links with the mobile station & BSC…

RF resources such as frequency assignments, sector separation, transmit

power control

BTS connects to BSC through un-channelized T1 facilities or direct cables in

co-located equipment (Abis)

The protocols are proprietary and are based on High-level data link control (HDLC)

Typically terminates the IS-2000 LAC/MAC protocols for common channels,

although in some implementations such protocols are terminated at the BSC

In case of dedicated channels, the BTS exchanges physical layer frames with

the BSC over Abis interface

Typically equated to the physical site of the wireless network where antennas

are located

3-cell BTS configuration is most common (max. up to 6 cell BTS)

OPERATION RANGE OF CELL TOWER

Height of antenna over surrounding terrain (Line-of-sightpropagation).

The frequency of signal in use.

Timing limitations in some technologies (e.g., GSM is limited to35 km, with 70 km being possible with special equipment)

The transmitter's rated power.

The required uplink/downlink data rate of the subscriber's device.

The directional characteristics of the site antenna array.

Reflection and absorption of radio energy by buildings orvegetation.

It may also be limited by local geographical or regulatory factorsand weather conditions.

GSM, have a fixed maximum range of 35 kilometers (22 mi)

CDMA and IDEN have no built-in limit, but it is possible to getbetween 50 to 70 km (30–45 miles)

FUNCTIONS OF BTS

Radio resources

Signal Processing

Signaling link management

Synchronization

Local maintenance handling

Functional supervision and Testing Controls the radio link

encryption

error control

signal strength

BTS FUNCTION ARCHITECTURE

CONT…

BTS has three levels;

a) Antenna coupling level (ANC)

b) Trans receiver level (TRX)

c) Base station control function level (BSF)

BTS is also referred to as the radio base

station (RBS), node B (in 3G Networks) or, simply,

the base station (BS). For discussion of the

LTE standard the abbreviation eNB for evolved

node B is widely used.

GENERAL ARCHITECTURE OF BTSA BTS in has the following parts:

Transceiver (TRX) Quite widely referred to as the driver receiver (DRX), DRXare either in form of single (sTRU), double(dTRU) or a composite double radiounit (DRU). It basically does transmission and reception of signals. It also doessending and reception of signals to and from higher network entities (likethe base station controller in mobile telephony).

Power amplifier (PA) Amplifies the signal from DRX for transmission throughantenna; may be integrated with DRX.

Combiner Combines feeds from several DRXs so that they could be sent outthrough a single antenna. Allows for a reduction in the number of antenna used.

Duplexer For separating sending and receiving signals to/from antenna. Doessending and receiving signals through the same antenna ports (cables to antenna).

Antenna This is the structure that the BTS lies underneath; it can be installed asit is or disguised in some way (Concealed cell sites).

Alarm extension system Collects working status alarms of various units in theBTS and extends them to operations and maintenance (O&M) monitoringstations.

Control function Controls and manages the various units of BTS, including anysoftware. On-the-spot configurations, status changes, software upgrades, etc. aredone through the control function.

Baseband receiver unit (BBxx) Frequency hopping, signal DSP, .

ANTENNA COUPLING LEVEL (ANC)

It is the stage between antenna & TRX.

A single module called ANC performs function up to 4

RTXs.

For higher capacity a COMBINER stage can be added.

TRANS RECEIVER LEVEL (TRX)

Trans-receiver equipment.

Used for reception & transmission of RF signal.

The Absolute Radio frequency channel number

(ARFCN) is allotted to one TRX & each ARFCN

is divided in 8 time slots, hence one TRX can

provide connection to 8 subscribers at a time.

One BTS= 12TRX= 12 ARFCN= 12*8 =96 Users

So at a time only 96 users can make calls.

BASE STATION CONTROL FUNCTION

LEVEL (BSF)

This station is ensured by station Unit Module (SUMA):

central unit of BTS.

Only one SUMA for one BTS.

Generally clocks for all other BTS module for

synchronization purposes. Ex: Abis link…

SUMA

BSF

RF & BTS STRUCTURE

BTS CONFIGURATION

CONT…

TYPES OF TOWER USED

– Self Supporting

– Monopoles

– Guys

TOWER SITE CONFIGURATION

ANTENNAS USED

An Antenna is a device to transmit and/or receive electromagnetic waves. Electromagnetic waves

are often referred to as radio waves.

ANTENNAS TYPES USED

Primary Antenna types in Wireless configurationsare:

Omni Directional Broadcasts in all directions

Examples are whip, helical and dipole

Directional Broadcast in a single direction

Examples are Yagi, and parabolic

Leaky Coax Broadcasts along path of the coaxial cable

Coaxial cable with the closely spaced slots in theouter conductor allowing signals to penetrate to thecore

Leaky

Coax

ELECTRICAL & MECHANICAL TILT

The tilt represents the inclination orangle of the antenna to its axis.

Electrical tilt is used for increasing ordecreasing of Beam radiation.

(+)=> Tx & (-)=> Rx

MECHANICAL TILT

Mechanical tilt is adjusted for maximum or

minimum coverage area radiation.

MULTI-INPUT MULTI-OUTPUT (MIMO) ANTENNAS

Mobile MIMO antenna

Directional Base station MIMO antenna

Dual band Wi-Fi MIMO antenna

Single band Omni directional MIMO antenna

2.4-5 GHz

LONG TERM EVOLUTION (LTE)

Long Term Evolution (LTE) is the world's leading 4G cellular

network technology.

LTE's high data rates and low latency enable applications such as

streaming HD video, high definition Voice over LTE (VoLTE),

broadcasting, and public safety emergency response.

Bandwidths ranging from 1.4 MHz to 20 MHz.

This makes LTE a natural upgrade path for carriers with both

GSM/UMTS and CDMA2000 networks.

Bands currently in use range from 450 MHz to 2700 MHz, with

bands as high as 3.5 GHz.

LTE MIMO antennas must be carefully designed in order to get

the full benefit of MIMO technology.