Marketing Mix - Bharat Sanchar Nigam...
Transcript of Marketing Mix - Bharat Sanchar Nigam...
For BSNL internal circulation only.
E2-E3
Consumer Mobility
GSM Radio Concept
For BSNL internal circulation only.
WELCOME
• This is a presentation for the E2-E3 Consumer
Mobility Module for the Topic: GSM Radio
Concepts
• Eligibility: Those who have got the Upgradation
from E2 to E3.
• This presentation is last updated on 15-3-2011.
• You can also visit the Digital library of BSNL to
see this topic.
For BSNL internal circulation only.
Learning Objective
Define radio concept
Frequency Spectrum for GSM
The Air Interface
Physical Channels- FDMA &
TDMA
Logical Channels
Frames
Network Attachment Procedure
For BSNL internal circulation only.
1. GSM Radio Concept
GSM Radio interface is an important openinterface which facilitates integration of variousmobiles with GSM networks. Coverage in a cellis provided by means of radio signalstransmitted through BTS.
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GSM Interface
Air interface or U m –interface
The Air Interface is the interface between theBTS (Base Transceiver Station) and the MS(Mobile Station). The air interface is required forsupporting:
Universal use of any compatible mobile stationin a GSM network
A maximum spectral efficiency
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A bis -interface
The A bis -interface is the interface between theBSC and the BTS.
The interface comprises traffic and controlchannels. Functions implemented at the A bis -interfaces are:
Voice-data traffic exchange
Signaling exchange between the BSC and theBTS
Transporting synchronization information fromthe BSC to the BTS
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7
GSM RADIO INTERFACE
Most Important Interface
Full Compatibility between mobile stations ofvarious Manufacturers & Networks of differentvendors to help roaming
To increase spectral efficiency
-- Large number of simultaneous calls in agiven
bandwidth
-- Frequency Reuse
-- Interference
-- Use of Interference Reduction Techniques
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GSM Uplink & Downlink
Frequency Bands
GSM 900 Mhz
DCS 1800 MHz
B
T
S
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9
GSM Specifications
RF Spectrum :
GSM 900
Mobile to BS (UP-LINK) - 890 to 915 MHz
BS to Mobile (DOWN -LINK) - 935 to 960 MHz
Bandwidth - 25 MHz
GSM 1800
Mobile to Cell (UP-LINK) - 1710 to 1785 MHz
Cell to Mobile (DOWN -LINK) - 1805 to 1880 MHz
Bandwidth - 75 MHz
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U m or Air interface
To achieve a high spectral efficiency in the
cellular network a combination of FDMA
(Frequency Division Multiple Access) and TDMA
(Time Division Multiple Access) is used.
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Frequency Division Multiple Access FDMA
It involves the division by frequency of the 25
MHz bandwidth into 124 carrier frequencies
spaced 200 KHz for GSM-900
GSM-1800 the frequency spectrum of the 75
MHz bandwidth is divided into 374 carrier
frequencies spaced 200 KHz.
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Time Division Multiple Access TDMA
To increase the number of channels per carrier
frequency
A carrier frequency channel carries eight time-
division multiplexed signals
A mobile station can transmit speech data only
during its assigned timeslot.
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Physical channel
It is determined by the carrier frequency and the
time slot number
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GSM-900 Specifications
Carrier Separation - 200 kHz
No. of RF Carriers - 124
Access Method - TDMA/FDMA
Modulation Method - GMSK
Transmission Rate - 270.833 Kbps
Speech Coding - Full rate 13 Kbps
Half rate 6.5 Kbps
Duplex Distance - 45 MHz
For BSNL internal circulation only.
GSM-1800 Specifications
No. of RF Carriers - 124
Access Method - TDMA/FDMA
Modulation Method - GMSK
Transmission Rate - 270.833 Kbps
Speech Coding - Full rate 13 Kbps
Half rate 6.5 Kbps
Duplex Distance - 95 MHz
For BSNL internal circulation only.
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GSM-- TDMA STRUCTURE
• TDMA 8 Time Slots / RF Channel
• Time slot duration 0.577m sec or 15 / 26 m sec
• Frame 8 Burst Periods ( Time Slots)
• Multi Frame Traffic 26 4.615 = 120 msec
Control 51 4.615 = 235.365 m sec
• Super Frame 51 Traffic Multi frames
26 Control Multi frames
• Hyper Frame 2048 Super Frames = 3 28 52.76
hr min sec
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Logical Channels
Traffic channel
Broadcast channels
Common control channels
Dedicated control channels
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Traffic channels
The traffic channels are used to send speech or
data services. There are two types of traffic
channels. They are distinguished by their
transmission rates
1. TCH/F (Traffic Channel Full rate )
2. TCH/H (Traffic Channel Half rate)
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TCH/F (Traffic Channel Full rate)
The TCH/F carries information at a gross bit rateof 22.8 kbit/s (after channel coding). The net (oreffective) bit rate at the TCH/F is for speech 13kbit/s and for data 12, 6 or 3.6 kbit/s (beforechannel coding). The transmission rates of thedata services allow services which arecompatible to the existing, respectively, 9.6, 4.8and 2.4 kbit/s PSTN and ISDN services.
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TCH/H (Traffic Channel Half rate)
The TCH/H carries information at a gross bit rateof 11.4 kbit/s. The net bit rate at the TCH/H is forspeech 5.6 kbit/s and for data 6 or 3.6 kbit/s.
A TCH/F or a TCH/H may also be used to sendsignaling information (for example callforwarding and short messages). In that case asmall portion of the time slot is used.
For BSNL internal circulation only.
Broadcast Channels
The information distributed over the broadcast
channels helps the mobile stations to orient
themselves in the mobile radio network.
The broadcast channels are point-to-multipoint
channels which are only defined for the downlink
direction (BTS to the mobile station)
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Types Of Broadcast Channels
BCCH (Broadcast Control Channel)
FCCH (Frequency Correction Channel)
SCH (Synchronization Channel)
CBCH (Cell Broadcast Channel)
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BCCH (Broadcast Control Channel)
Via the BCCH the mobile station is informed
about the system configuration parameters (for
example Local Area Identification, Cell Identity
and Neighbor Cells). Using this information the
mobile stations can choose the best cell to
attach to.
The BCCH is also known as beacon.
For BSNL internal circulation only.
FCCH (Frequency Correction Channel)
To communicate with the BTS the mobile station
must tune to the BTS. The FCC transmits a
constant frequency shift of the radio frequency
carrier that can be used by the mobile station for
frequency correction
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SCH (Synchronization Channel)
The SCH is used to time synchronize the mobile
stations. The data on this channel carries the
TDMA frame number and the BSIC (Base
Station Identity Code).
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CBCH (Cell Broadcast Channel)
The CBCH is used for the transmission of
generally accessible information (Short Message
Service messages) in a cell, which can be polled
by the mobile station.
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Common Control Channel
Common control channels are specified as
point-to-multipoint channels which only operate
in one direction of transmission, either in the
uplink or downlink direction
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Types of Common Control Channel
PCH (Paging Channel)
AGCH (Access Grant Channel)
RACH (Random Access Channel)
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PCH (Paging Channel)
The PCH is used in the downlink direction for
paging the mobile stations
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AGCH (Access Grant Channel)
The AGCH is also used in the downlink direction.
A logical channel for a connection is allocated
via the AGCH if the mobile station has requested
such a Channel via the RACH.
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RACH (Random Access Channel)
The RACH is used in the uplink direction by the
mobile stations for requesting a channel for a
connection. It is an access channel that uses the
slotted Aloha access scheme
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Dedicated Control Channels P-P
Dedicated control channels are full-duplex,
point-to-point Channels. They are used for
signaling between the BTS and a certain mobile
station
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Types of Dedicated Control Channels
SACCH (Slow Associated Control Channel)
FACCH (Fast Associated Control Channel)
SDCCH (Stand-alone Dedicated Control Channel)
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SACCH (Slow Associated Control Channel)
The SACCH is a duplex Channel which is
always allocated to a TCH or SDCCH. The
SACCH is used for transmission of signaling
data, radio link supervision measurements,
transmit power control and timing advance data.
Note that the SACCH is only used for non-urgent
procedures.
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FACCH (Fast Associated Control Channel )
The FACCH is used as a main signaling link forthe transmission of signaling data (for examplehandover commands). It is also required forevery call set-up and release. During the call theFACCH data is transmitted over the allocatedTCH instead of traffic data; this is marked by aflag called a stealing flag. The process ofstealing a TCH for FACCH data is called pre-emption.
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SDCCH (Stand-alone Dedicated Control
Channel)
The SDCCH is a duplex, point-to-point Channelwhich is used for signaling in higher layers. Itcarries all signaling between the BTS and themobile station when no TCH is allocated. TheSDCCHs are used for service requests (forexample Short Message Service), locationupdates, subscriber authentication, cipheringinitiation, equipment validation and assignmentto a TCH. The net SDCCH bit rate is about 0.8kbit/s.
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Multiplexing Logical Channels onto
Physical Channels
Several of the above-mentioned types of logicalchannels can be transmitted over one singlephysical channel (timeslot).
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Channel Combination
1.TCH/F + FACCH/F + SACCH/F
2. TCH/H + FACCH/H + SACCH/H
3. (TCH/F + FACCH/F + SACCH/F) or (TCH/H +FACCH/H + SACCH/H)
4. FCCH + SCH + CCCH + BCCH
5. FCCH + SCH + CCCH + BCCH + SDCCH/4 +SACCH/4
6. CCCH + BCCH
7. SDCCH/8 + SACCH/8
For BSNL internal circulation only.
The CCCH is a channel that carries both thePCH and the AGCH on the downlink, and theRACH on the uplink.
The extensions “/4” and “/8” mean, respectively,that four and eight logical channels are mappedonto one physical channel (timeslot).
Note that the BCCH is always transmitted intimeslot 0 on the first defined frequency.
The logical channels FCCH, SCH, BCCH andCCCH are transmitted on the downlink intimeslot 0.
For BSNL internal circulation only.
Frame Types on the Um –interface
TDMA frame
A TDMA frame consists of eight timeslots(physical channels). The length of a timeslot is0.577 ms. The length of a TDMA frame istherefore 4.62 ms.
Data on a timeslot is transmitted in bursts, thelength of a timeslot is often expressed in BP(Burst Period); 1 BP represents the length of 1timeslot.
For BSNL internal circulation only.
26-TDMA multiframe
This multiframe is defined as a succession of 26TDMA frames, and corresponds to the 26 x 8 BPor 120 ms cycle used in the definition of theTCH/F and TCH/H.
51-TDMA multiframe
This multiframe is defined as a succession of 51TDMA frames, and corresponds to the 51 x 8 BPcycle used in the definition of the TCH/F, TCH/Hand of the common channels
For BSNL internal circulation only.
Super frame
The superframe is a succession of 51 x 26 TDMAframes (6.12 sec), and corresponds to the smallestcycle for which the organization of all channels isrepeated.
Hyper frame
The hyper frame is the numbering period. It is 2048 x51 x 26 x 8 BP long, or 3 hours, 28 minutes, 53seconds and 760 milliseconds. It is a multiple of allpreviously cited cycles, and determines all the cyclesin the transmission of the radio path. It is in particularthe smallest cycle for frequency hopping and forciphering.
For BSNL internal circulation only.
45
OPERATIONAL CONCEPTSIDLE MODE
• IDLE MODE
ACCESS PROCDURE DEDICATED MODE
• MS O/G Call
• MS I/C Call
----FCCH
---- SCH
----BCCH
----RACH
----AGCH
----SDCCH
----TCH
----PCH
----RACH----AGCH
----SDCCH
----TCH
For BSNL internal circulation only.
Network Attachment Process:
Network attachment is the process of selectingan appropriate cell (radio frequency) by themobile station to make its location known to thenetwork.
The process starts when the mobile is switchedon, and ends when the mobile station enter theidle mode. In idle mode the mobile station doesnot have a traffic channel allocated to make orreceive a call, but the Public Land MobileNetwork (PLMN) is aware of the existence of themobile station within the chosen cell
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For BSNL internal circulation only.
The network attachment process
It consists of the following three tasks
Cell Identification
PLMN Selection
Cell selection
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For BSNL internal circulation only.
Cell Identification
When Mobile Station is switched on, it attemptsto make contact with a GSM PLMN byperforming following actions.
Measure the BCCH channel.
Search for a suitable cell.
The Mobile Station measure the signal strengthof the BCCH (Broadcast Control Channel)Channels received. It stores a list informationabout 30 of these BCCH channels, such assignal strength and the frequencycorresponding.
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PLMN Selection
Automatic mode
In automatic mode, the station will choose which PLMNs to tryby itself. The automatic mode is based on the existence of thepreferred list, which is stored in a non-volatile memory in theSIM. This list includes a number of PLMN identities in order ofpreference and is under control of the user. The most preferredis usually the home PLMN. The list is filled in by the userthrough a mechanism to be specified by the mobile stationmanufacturer. The automatic mode is normally used when themobile station operates on its home PLMN (that is the PLMNthe mobile station is subscribed to).
Manual mode
In manual mode, the user is presented a list containing allfound PLMNs. The user chooses one of the PLMNs from thelist.
For BSNL internal circulation only.
Cell selection
The mobile station attempts to find a suitable cell bypassing through the list in descending order of receivedsignal strength; the first BCCH Channel which satisfies aset of requirements. The requirement that a cell mustsatisfy before a mobile station can be provide servicefrom it, are:
It should be a cell of the selected PLMN.
The mobile station checks whether the cell is part of theselected PLMN.
It should not be “barred”.
The PLMN operator may decide not to allow mobilestations to access certain cells. These cells may, forexample, only be used for handover traffic. Barred cellinformation is broadcast on the BCCH to instruct mobilestations not to access these cells.
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If No suitable cell found MS can only attemptto make emergency calls irrespective of thePLMN identity .
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