Wireless communication and its standards

AGENDA
WIRELESS COMMUNICATION.
CELLULAR TECHNOLOGY.
STANDARDS
EVOLUTION OF MOBILE TECHNOLOGY.
MODULATION&MULTIPLEXING.
FDMA/CDMA/TDMA.
GSM/CDMA.
GSM ARCHITECTURE(MS/BSS/NSS FUNCTION).
GSM CHANNEL.

WIRELESS COMMUNICATION
Definition: Transfer of information without ‘wires’. Information can be transmitted
between two location using a signal that can be either analog or digital in nature.
In telecommunication networks: Digital transmission is exclusively used.
Wireless communication can take several forms:
Microwave (Point-Point)-Low and medium capacity over short and medium distance.
Microwave radio transmissions have been used in telecommunication industry for the
transport of point-point data where information transmissions occur through carrier
signal.
Satellite communication- Low and medium capacity over long distance.
Wireless Technology:
To understand WT, a basic understanding of the radio frequency(RF) spectrum is
required.
It`s rate of oscillation in the range of about 3KHZ-300GHZ.

CELLULAR TECHNOLOGY
Cellular network is a radio-based technology; radio waves are electromagnetic waves that antenna
propagate. Most signals are in the 850MHZ, 900MHZ, 1800MHZ, 1900MHZ frequency bands.
Mobile radio Transmission system may be classified into: Simplex, Half-Duplex, Full-Duplex.
Simplex: One way communication- Paging System.
Half-Duplex: Two way communication, but same channel for TX and RX. Push-To-Talk, release-to-listen.
Ex: walkie talkies- Applies to TDD system.
Full-Duplex: Two way communication in different frequency, simultaneously transmit and receive.
Ex: Mobile phone. Applies to FDD system.
TDD- Time Division Duplex FDD: Frequency Division Duplex
One channel for uplink and down link Separate channel for uplink and downlink
ADV: Effective spectrum usage ADV: Suitable for voice communication
DIAADV: Time delay DIS ADV: Spectrum usage is high.

MICROWAVE COMMUNICATION
Microwave communication requires line of sight and earth towers to transmit information and hence
have relatively smaller area coverage. One tower receives a signal it amplifies it and sends it to the next
tower. The microwave systems have the capability to carry large amount of data both digital and
analogue at high speed and are mostly used for the transmission of telephone and television signals.
Advantages:
No cables needed.
Multiple channels available.
Wide bandwidth.
Disadvantages:
Line-of-sight will be disrupted if any obstacle, such as new buildings, are in the way
Signal absorption by the atmosphere. Microwaves suffer from attenuation due to atmospheric
conditions.
Towers are expensive to build.
MW equipment providers:
Ericsson
Nokia
Alcatel
Intracom

Evolution of Cellular technology

RANGE DATA RATE OF IEEE/ITU-T STANDARD

STANDARDS
What is STANDARD:
Standard is a level of quality, especially one that people think is acceptable.
standard is nothing but collection of defined criteria's to asses product ,service or system.
Why do we need standards?
Standards can be found throughout our daily lives but why do we need them?
Products might not work as expected.
They may be of inferior quality and incompatible with other equipment, in fact they may not
even connect with them.
non-standardized products may even be dangerous.
Standardized products and services are valuable User 'confidence builders', being perceived as:
Safe.
Secure.
high quality.
Flexible.
As a result, standardized goods and services are widely accepted, commonly trusted and highly
valued.

WIRELESS COMMUNICATION STANDARD
ITU-International Telecommunication Union.
IEEE- Institute of Electrical and Electronics Engineers.
The 3rd Generation Partnership Project (3GPP) is a collaboration between groups of
telecommunications associations, known as the Organizational Partners.
3GPP is the standard body behind the (UMTS) that is the 3G upgrade to GSM networks.
The 3rd Generation Partnership Project 2(3GPP) is a collaboration between telecommunications
associations to make a globally applicable 3G mobile phone system specification within the scope of
the ITU's IMT-2000 project.
3GPP2 is the standard body behind the competing 3G standard CDMA2000 that is the 3G upgrade
to CDMAONE networks used mostly in the United States.
GSM/GPRS/EDGE/W-CDMA is the most widespread wireless standard in the world. A few countries
(such as China, the United States, India, South Korea and Japan) use both sets of standards, but most
countries use only the GSM family.

STANDARDS
What is ITU:
International Telecommunication Union. is an agency of the United Nations (UN) whose
purpose is to coordinate telecommunication operations and services throughout the world.
The ITU sets and publishes regulations and standards relevant to electronic communication
and broadcasting technologies of all kinds including radio, television, satellite, telephone and
the Internet .
It has three sectors:
1.ITU-T
Telecommunication Standardization sector It coordinates standards for telecommunications.
Ex: GSM, 3G, 4G.
2.ITU-R
Telecommunication Radio communication sector. It coordinates standards for radio
communications services as well as the international management of the radio frequency
spectrum and satellite orbits. Ex: ULTRA-HDTV & 3D-TV
3.ITU-D
Telecommunication Development sector. Assists countries in developing and maintaining
internal communication operations

WIRELESS COMMUNICATION STANDARD
STAND LIST OF TECH BW MODULATION FREQ BAND
ITU-T GSM-2G 200KHZ GMSK 900/1800MHZ
ITU-T GPRS-2.5G 200KHZ GMSK 900/1800MHZ
ITU-T EDGE-2.75G 200KHZ GMSK/8PSK 900/1800MHZ
ITU-T W-CDMA-3G 5MHZ QAM/64QPSK 2100MHZ
ITU-T LTE-4G 5-20MHZ QAM/QPSK 2300MHZ
QUALCOMM CDMA-2000 1.25MHZ QPSK 850MHZ
IEEE BLUETOOTH 800Kbps-Data
rate
GFSK 2.4GHZ
IEEE WIFI 11Mbps-Data
rate
GFSK 2.4GHZ
IEEE WIMAX 30Mbps-Data
rate
OFDM 5.8GHZ

Generations Definitions/Data rate Features
1G-1980-1990 Analog-14.4Kb/s Voice
2G-1990-2004 Digital narrow band CKT
Voice, SMS, Conference calls,
Caller ID.
2.5G-GPRS Digital narrow band CKT/Packet data Voice+Data/WAP/MMS
2.75G-EDGE Digital narrow band CKT/Packet data
Voice Data/WAP/MMS/Web
browsing/Short audio video
clips.
3G-2004-13
Digital broadband packet data/Data rate-
200kb/s-2mb/s
High speed web/Video
conferencing/Navigation/maps
3.5G-HSDPA
8Mkb/s-10Mb/s
Multiplayer gaming
3.75G-HSUPA
1.4Mb/s-5Mb/s
4G-LTE
Digital broadband packet data very high
throughput/Data rate-100Mb/s-1Gb/s
High quality streaming
video/High quality video
conferencing.

Generations Advantages Disadvantages
1G-1980-1990
Focus on voice
Data service non-existent
Impossible international
roaming.
Poor handoff reliability.
Large Phone size.
2G-1990-2004 Possibility of wireless data
service.
More flexible.
Unable to handle complex data
such as video.
Circuit switch network, does
not support high data rate
results weaker digital signal.
3G-2004-13
Rich multimedia services.
More bandwidth and security.
High data rate.
Expensive service license.
Infrastructure for 3G.
4G-LTE(Up coming) Broadband access in remote
locations. Higher BW tight
network security.
Very expensive.

MODULATION TECHNIQUE
Modulation: Modulation is the process of superimposing a low frequency signal on high
frequency carrier signal.
It`s process of mixing a signal with sinusoid to produce a new signal. Will have certain benefits
of an un-modulated signal especially during transmission.
Modulation is a form of change process where we change the input information into a suitable
format for the transmission medium.
It`s general technique of shaping a signal to convey a information.
Keying : Keying is a family of modulation forms. The goal of keying is to transmit digital signal
over an analogue channel.
Analog Modulation: AM, FM, PM, QAM, SM, SSB.
Digital Modulation: ASK, APSK, CPM, FSK, MFSK, MSK, PSK.
Spread spectrum: CSS, DSSS, FHSS.

DIFF-AM FM PM
AM FM PM
Amplitude of the carrier signal
increase or decrease
Frequency of the carrier signal
Phase of the carrier signal
Can Transmit long distance Short Distance FM and PM are inseparably links
BW is small BW is high Phase is integral of frequency
Poor sound quality Better than AM PM used for digital form of txn
Range 535-1705Khz upto 1200
Bps
88-108 Mhz upto 1200-2400Bps ASK+PSK=QAM
Impacted with environmental
noise
Doesn`t degrade linearly with
distance
While Phase changes Frequency
will change and vice-versa
Impacted with physical barrier

MULTIPLEXING TECHNIQUE
Multiplexing: Combining multiple stream information for transmission over a shared medium. Several
input one output.
To combine many signals(voice or data) so they can sent over one transmission medium.
De multiplexing: Reverse function of multiplexing. One input several Output.
Guard Band: It`s an unused part of the radio spectrum between radio bands.
FDM TDM WDM
Can be used with analog signal. Can be used with digital signal or
analog signal carrying digital data.
Multiplexes no.of optical carrier
signal onto a single optical fiber by
using different wavelength.
No.of signal carried signal on same
medium.
Data from various sources are
carried in respective frames.
Its applied to CWDM&DWDM
By allocating to each signal a
different frequency band.
Each frames consists of time slots. Each wavelength can carry different
signal. SDH 2.5G, 10G, ATM, IP
Guard bands are used for avoid
interference,
Each source assigned time slot per
frame.
Provide much better latency. Sync pulses added to identify the
beginning of each frame.
Provide much better flexibility. Best application: Long Haul.

Frequency Division Multiple Access
Frequency is a precious and natural resource.
Each mobile is assigned a separate frequency channel for the duration of the call.
MS will have one downlink frequency band and one uplink frequency band.
Guar band is required to prevent adjacent channel interference.

Time Division Multiple Access
TDMA is a type of multiplexing where two or more channel of information are transmitted over
the same link by allocating a different time interval for the transmission of each channel.
TDMA separates users according to time, it ensures that there will be no interference from
simultaneous transmission.
Each user is given a specific slot.
It`s the only technology that the user has occupied predefined time slots.
Only one mobile terminal transmits during each slot.

Code Division Multiple Access
CDMA is a digital wireless air interface and networking standards based on the principle of
spread spectrum technology, which allow multiple users to access the system simultaneously on
the same carrier frequency.
Bandwidth occupied by the signal is much larger than the information transmission rate.
Each symbol of bit is transmitted as a larger number of bits using the user specific code –
Spreading.
Use of orthogonal codes to separate different transmissions.
But all users use the same frequency band together.

FDMA CDMA TDMA
Differ signals are assigned frequency
channel. A channel is a frequency.
Users can access the system
simultaneously on the same carrier
frequency by using SS.
Users can access the same
frequency spectrum by dividing the
time slots.
Each channel can be assigned to
only one user at a time.
By using unique assigned codes
users can be occupy the frequency.
2 or more channel of information
are transmitted over same link by
allocating diff time interval.
SS: The signal occupies a BW in
excess of the minimum necessary to
send the information.
FHSS: improves C/I ratio by utilizing
many freq channel. And also fading
and mmultipath prob.
ADV: Make before break
connection.” soft hand off”
Very high spectral capacity.
ADV: “Hard hand off”. Easily adapt
data & voice transmission.
Users separates by dividing time
slots. It ensures no interference.
DIS ADV: Channel pollution.
There is no international roaming.
DIS ADV: “call drop” may occur when
moving one to another.
EX: AMPS, TACS EX: CDMA 2000-1X RTT,
CDMA 2000-1X EVDO
EX: GSM

What is GSM
GSM stands for Global System for Mobile communication.
The European system was called GSM and deployed in early 1990`s. Designed on 900MHZ and
1800MHZ range.
It was the first fully digital system utilizing the 900MHZ frequency band. The initial GSM had
200KHZ radio channel s, 8-full rate or 16-half rate TDAM channels per carrier.
The GSM makes use of narrowband Time Division Multiple Access (TDMA) technique for
transmitting signals.
The GSM was developed using digital technology. It has an ability to carry 64 kbps to 120 Mbps
of data rates.
Presently GSM support more than one billion mobile subscribers in more than 210 countries
throughout of the world.
The GSM provides basic to advanced voice and data services including Roaming service.

What is CDMA
IS-95-Code Division Multiple Access.
824-849MHZ.
Each carrier 1.24MHZ.
4 types of logical channel: A pilot, A synchronization, 7 paging, 55 traffic.
Channels are separated using different spreading codes.
QPSK modulation scheme.
64 orthogonal walsh code are used. It`s used to differentiate between the transmission with in
the cell.
Using PN offset we can separate the cells

GSM CDMA
TDMA CDMA
FHSS DSSS
900/1800MHZ 850MHZ
CHANNEL SPACING(BW)-200KHZ CHANNEL SPACING(BW)-1.25MHZ
FREQUENCY REUSE PN REUSE
MODULATION-GMSK MODULATION-QPSK
USERS SEP BY DIFF TIME SLOTS USERS CAN ACCESS WHOLE SPECTRUM
FREQ MUST BE PLANNED NO FREQ PLANNING
11 TYPES OF LOGICAL CHANNEL 4 TYPES OF LOGICAL CHANNEL
NEED MORE NO.OF BTS TO COVER LA NEED LESS NO.OF BTS TO COVER LA
DEPENDING ON.TRAFFIC-N/W CAP,COV
INCREASE
DEPENDING ON NOISE-N/W PLANNED
DIFFERENCE B/W GSM & CDMA

DIFFERENCE B/W 900/1800 MHZ FREQ BAND
900MHZ 1800MHZ
PROVIDE LARGE COVERAGE PROVIDE SMALLER COVERAGE
IT`S MAINLY SUPPORTED FOR SUBURBAN, RURAL IT`S MAINLY SUPPORTED FOR URBAN, DENSE
URBAN AREA
LESS NO.OF BTS WE CAN PROVIDE MORE
COVERAGE.
WE USE MORE NO.OF.BTS.
CAPACITY WISE WE CAN USE MORE BTS WITH IN
A CERTAIN RANGE.
VICE-VERSA

Comparison b/w 900/1800MHZ
Parameters 900 1800
Multiple Access TDMA/FDMA/FDD TDMA/FDMA/FDD
Uplink 890-915MHZ 1710-1785MHZ
Downlink 935-960MHZ 1805-1880MHZ
No. of. Channels 124 374
Channel spacing/BW 200KHZ 200KHZ
Channels/Carrier 8 time slot 8 time slot
Time slot duration
0.577ms 0.577ms
Frame duration 4.62ms 4.62ms
Duplex spacing 45MHZ 45MHZ

Why GSM?
The ETSI group aimed to provide the following through the GSM:
Improved spectrum efficiency.
International roaming.
Low-cost mobile sets and base stations (BSs).
High-quality speech.
Compatibility with Integrated Services Digital Network (ISDN) and other telephone company
services.
Support for new services.

GSM ARCHITECTURE
The GSM network can be divided into following broad parts:
The Mobile station(MS).
The Base Station Subsystem(BSS).
The Net work Switching Subsystem(NSS).

GSM network areas
Cell: Cell is the basic service area: one BTS covers one cell. Each cell is given a Cell Global Identity
(CGI), a number that uniquely identifies the cell.
Location Area: A group of cells form a Location Area. This is the area that is paged when a
subscriber gets an incoming call. Each Location Area is assigned a Location Area Identity (LAI). Each
Location Area is served by one or more BSCs.
MSC/VLR Service Area: The area covered by one MSC is called the MSC/VLR service area.
PLMN: The area covered by one network operator is called PLMN. A PLMN can contain one or
more MSCs.

The Mobile Stations(MS)
MS is the user’s handset and has two parts.
ME+SIM.
Mobile Equipment:
•Radio equipment
•User interface
•Processing capability and memory required for various tasks.
It provides the air interface to the user in GSM networks.

The Mobile Station(MS)
Functions of mobile stations:
Voice and data transmission and receipt.
Frequency and time synchronization.
Monitoring of power and signal quality of surrounding cells.
Provision of location update even during inactive state.
An MS can have any of the following state:
IDLE: The MS is ON but a call is not in progress.
ACTIVE: The MS is ON and a call is in progress.
DETACHED: The MS is OFF.

Network Identities
MSISDN: Mobile Station ISDN is registered in the telephone directory and used by the calling
party for dialing. Shall not exceed 15 digits.
IMSI: International Mobile Subscriber Identity, The IMSI is an unique which is used
internationally and used within the network to identify the mobile subscribers. Max 15 digits.
TMSI: Temporary Mobile Subscriber Identity. It`s temporary IMSI no. The VLR assigns a TMSI to
each mobile subscribers entering the VLR area. Assigned only after successful authentication.
TMSI changes on location updation. TMSI is less than 8 digit.
MSRN: Mobile Station Roaming Number. It`s temporary identity which is assigned during the
establishment of a call to a roaming subs.
IMEI: International Mobile Equipment Identity. It`s an unique code allocated to each mobile
equipment.

Functions of BSS
The BSS composed of TWO parts:
The Base Transceiver Station(BTS)
The Base Station Controller(BSC).
The interface between BSC and BTS is designed as an A-bis interface.
The interface between the MSC and the BSS is a standardized SS7 interface (A-interface).
The BSS is responsible for all the radio related functions in the system, such as:
 Radio communication with the mobile units
Handover of calls in progress between cells
 Management of all radio network resources and cell configuration data.

Functions of BSC
It`s part of BSS system
BSC manages the radio resources for one or more BTSs. It handles radio channel setup,
frequency hopping and handovers.
The function of the BSC is to allocate the necessary time slots between the BTS and MSC.
Control of frequency hopping.
The BSC is connected to the MSC on one side and to the BTS on the other.
Handling of MS connections and performs the intercell handover for MSs moving between BTS in
its control.
Manage the Handover within BSS area.
Knows which mobile stations are within the cell and informs the MSC/VLR about this.
Controls several transmitters.

Function of Base Transceiver Station
BTS acts as the interface between MS’s (Mobile Station) and the network, by providing radio
coverage functions from their antennae.
It`s located between the Mobile Station (MS) and the Base Station Controller (BSC).
The BTS is basically classified into two types: Indoor & Outdoor.
The primary responsibility of the BTS (Base Transceiver Station) is to transmit and receive radio
signals from a mobile unit over an air interface.
A BTS is usually placed in the center of a cell. Its transmitting power defines the size of a cell.
Each BTS has between 1 and 16 transceivers, depending on the density of users in the cell.
Encoding, encrypting, multiplexing, modulating, and feeding the RF signals to the antenna.
Decoding, decrypting, and equalizing received signals

Cont….
Transcoding and rate adaptation.
Voice through full- or half-rate services
Trans-coding to bring 13-kbps speech to a standard data rate of 16 kbps and then combining four
of these signals to 64 kbps is essentially a part of BTS, though, it can be done at BSC or at MSC.
Every BTS or RBS has standardized hardware units.
EX:ERICSSON RBS 2000 FAMILY: (INDOOR UNIT)/GSM 900/1800 FREQ BAND:
DXU: Distribution Switching Unit.
TRU: Transceiver Unit.
CDU: Combined Distribution Unit.
CXU: Configuration Switching Unit. Or Rx Splitter.
PSU: Power Supply Unit.

Cont…
DXU: It`s CPU of BTS acts as an interface b/w transmission networks and transceivers.
Manages the link resources and connects the traffic time slots from the BSC link to the TRU’s.
DXU can work on both 1.544MBPS(T1), 2.048MBPS(E1).
TRU: It is responsible for radio transmitting, radio receiving, power amplification and signal
processing.
EdTRU, EDRU, RRU-Support for EDGE, GPRS.
CDU: It`s interface b/w transceivers and antenna system.
The task of the CDU is to combine signals to be transmitted from various transceivers and to
distribute received signals to the receivers.
A range of CDU types have been developed to support different configurations within the RBS
2000 family. EX: CDU-G, CDU-F.
CXU: Positioned b/w CDU & TRU.
It distributed b/w Rx signals from CDU to TRU within the same BTS.
1 CXU can support max 3CDU.
PSU: The PSU rectifies the power supply voltage to the +24 VDC necessary for RBS operation.

Functions of Network Switching Subsystem
NSS or GSM core network is the component of GSM system that carries out call switching
and mobility management functions for mobile phones.
It was originally consisted of circuit switched core network used for traditional GSM sevices
such as voice call, SMS circuit switch data calls. Now extended with an packet switched data
services known as GPRS core network.
Main functions of NSS: Call control, charging, mobility management, subscriber data
handling.
The switching system includes the following functional elements.
MSC-Mobile Switching Centre.
HLR-Home Location Register.
VLR-Visitor Location Register
AUC-Authentication Centre
EIR-Equipment Identity Register.

Functions of MSC
The central component of the Network Subsystem is the MSC.
primary functions of an MSC include the following:
Switching and call routing: Routing of calls between GSM users and PSTN users.
Service provisioning: Supplementary services are provided and managed by a MSC. In addition,
the SMS service is handled by MSC’s.
Charging: The MSC performs billing on calls for all subscribers based in its areas. When the
subscriber is roaming elsewhere, the MSC obtains data for the call billing from the visited MSC.
Service provisioning: Gateway to SMS between SMS centers and subscribers.
Communication with HLR: The primary occasion on which an MSC and HLR communicate is during
the set-up of a call to an MS, when the HLR requests some routing information from the MSC.
 Communication with the VLR: Associated with each MSC is a VLR, with which it communicates for
subscription information, especially during call set-up and release.
Communication with other MSC’s: It may be necessary for two MSC’s to communicate with each
other during call setup or handovers between cells belonging to different MSC’s.

Cont…..
Control of connected BSC’s: As the BSS acts as the interface between the MS’s and the SS, the
MSC has the function of controlling the primary BSS node: the BSC. Each MSC may control many
BSC’s, depending on the volume of traffic in a particular MSC service area. An MSC may
communicate with its BSC’s during, for example, call set-up and handovers between two BSC’s.
Direct access to Internet services: Traditionally, an MSC accessed the Internet nodes of an
Internet Service Provider (ISP) via existing networks such as the PSTN.
GMSC: It`s node that interconnected two network.
EX: Calls to and from one network to another network. Either MS to MS and MS to fixed line
service.

Functions of HLR
The HLR is a centralized network database that stores and manages all mobile subscriptions
belonging to a specific operator.
Both VLR and HLR can be implemented in the same equipment in an MSC.
Data in HLR:
IMSI, MS-ISDN number.
Category of MS.
Roaming restriction ( allowed or not ).
Supplementary services like call forwarding.
The information stored includes:
 Subscriber identity (i.e. IMSI, MSISDN) .
Subscriber supplementary services.
Subscriber location information (i.e. MSC service area).
Subscriber authentication information.

Functions of VLR
It`s always integrated with MSC.
VLR database which contains information about subscribers currently being in the service area of
the MSC/VLR.
The VLR database is temporary, in the sense that the data is held as long as the subscriber is
within its service area.
When a mobile station roams into a new MSC area, the VLR connected to that MSC will request
data about the mobile station from the HLR.
 if the mobile station makes a call, the VLR will have the information needed for call setup
without having to interrogate the HLR each time.
VLR assigns TMSI which keeps on changing.
Data in VLR:
IMSI & TMSI.
MSRN.
Location Area.
MS category.
Authentication Key

Functions of AUC
The authentication centre is a protected database.
The authentication centre provide security information to the network.
AUC is connected to HLR which provides it with authentication parameters and ciphering keys
used to ensure network security.
To perform subscriber authentication and to establish ciphering procedures on the radio link
between the network and MS.
Information provided is called a TRIPLET consists of:
RAND(Non Predictable Random Number)
SRES(Signed Response)
Kc(ciphering Key).

Functions of EIR
EIR is used for security reasons.
The equipment identification procedure uses the identity of the equipment itself (IMEI) to ensure
that the MS terminal equipment is valid.
This data base stores IMEI for all registered mobile equipments and is unique to every ME.
White list : IMEI, assigned to valid ME.
Black list : IMEI reported stolen.
 Gray list : IMEI having problems like faulty software, wrong make of equipment etc.

GSM Channels
Physical Channel: one time slot on one carrier is called physical channel.
Logical Channel: Information carried by physical channel is called logical channel.

Functions of Broadcast channel
CHANNEL DIRECTION FUNCTION
BCCH Point to Multipoint(Down link)
1.GSM band & frequency
hopping 2. LAI, RACH
parameters 3.Neighbouring
infromation
FCCH Point to Multipoint(Down link)
To communicate BTS MS must
tune to the BTS freq, It`s used
MS for freq correction
SCH Point to Multipoint(Down link)
SCH is used to time
synchronize the MS, This
channel carries the TDMA
frame.

Functions of common control channel
PCH
Point to Multipoint(Down
link or Uplink)
1.Downlink direction for
paging MS. 2.Incoming call
purpose PCH is used
AGCH
Point to Multipoint(Down
link)
1.MS request a call. 2.
Connection is allowed via
AGCH
RACH Point to Multipoint(Up link)
MS wants to make call,
receive call, SMS, LAI the MS
uses RACH.

Functions of dedicated control channel
SACCH Point to point
1.Always used with
TCH(or)SDCCH.2.It`s only for
non-urgent&periodically.3.Txn
of signalling data, radio link
measur, transmit power
control
FACCH Point to point
1.Used for emerging
procedures. 2.It`s require for
call setup&release
SDCCH Point to point
1.It carries all signalling b/w
BTS&MS when no TCH
allocated.2. It`s used for LAI,
subscriber AUC,ciphering
initiation, equipment
validation.

Mobile Originating Call
A call is originated from a MS as follows,
The MS uses RACH (Random Access Channel) to ask for a signaling channel.
 The BSC/TRC allocates a signaling channel, using AGCH (Access Grant Channel).
 The MS sends a call set-up request via SDCCH (Stand alone Dedicated Control Channel) to the
MSC/VLR. Over SDCCH all signaling preceding a call takes place. This includes:
Marking the MS as “active” in the VLR
The authentication procedure
Equipment identification
Sending the B-subscriber’s number to the network
Checking if the subscriber has the service “Barring of outgoing calls” activated

Cont….
The MSC/VLR instructs the BSC/TRC to allocate an idle TCH. The BTS and MS are told to tune
to the TCH.
The MSC/VLR forwards the B–number to an exchange in the PSTN, which establishes a
connection to the subscriber.
If the B-subscriber answers, the connection is established.
videosEricsson The History of Wireless Communication.wmv

2G/3G Architecture
SD
Mobile Station
MSC/
VLR
Base Station
Subsystem
GMSC
Network Subsystem
AUC
EIR HLR
Other Networks
Note: Interfaces have been omitted for clarity purposes.
GGSN
SGSN
BTS
BSC
Node
B
RNC
RNS
UTRAN
SIM
ME
USIM
ME
+
PSTN
PLMN
Internet

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