1. Data two types
 Analog
 Form of sinusoidal wave pattern…
changing states
 Digital
 Form of ON/OFF pattern… pulses

2. Communication
 Analog data transmission
 States changes (follows SIN wave)
 Maintenance cost is low
 But.. Cost of transmission is high
 Effect of environment is very high
 Amplifier circuit loses data

3.  Digital data transmission
 Follow ON/OFF pattern
 Mainainance cost is high
 Transmission cost is low
 Environment factor… low
 No loss while using amplifier/reapeter

4. Channel Characteristic
 Ideal channel
 Should convey the maximum from
sender to receiver
 Should not ALTER…(additional noise)
 No distance restriction
 Convey cost should be maintain
 Type
 Analog
 digital

5. Close look to the digital channel
 Channel carries BITS
 Measurement… how many BIT/ second
called bit rate (bps)
 The bps is the rate at which the channel
can carry BITS (digital data)
 Distribution of bits determine bit rate
shorter the duration greater bps

6. TRANSMISSION MODES
 Simplex
DATA
Sender receiver
 Only one way communication …
unidirectional flow
 Interactive part is absent… so no ackw
 Examples… keyboard/printer.. Radio, TV
 Cheapest… but low efficient

7.  Half duplex
Sender/ DATA Receiver
Receiver Sender
 Both communication thru same
medium
 Only one is active at a time … no one at
the same time
 Either send or receive at a time
 Examples HDD, RAM

8.  Full Duplex
Data
Sender Receiver
Receiver Sender
 Simultaneous transmission in both
direction
 Full interactive communication
 Examples… telephone/mobile
 costly

9. Asynchronous Mode Transmission
 Referred as ON/OFF (Start/stop)
transmission
 Transmission takes place character by
character
Character sequence
Irregular time interval

10.  Each channel is started by ‘start’ bit
and ended by ‘stop’ bit
 Channel remain unused between
the two character… hence at each
character start and stop bit is
required to notify the receiver
 Summery :- Data is transmitted
character by character at irregular
time interval

11. Synchronous Mode Transmission
 Character are grouped as a block
 Series of such blocks are
transmitted
 Each block is started by HEADER
and ended with TRAILER
information and each block may
contain hundreds of characters
Indefinite time interval between blocks

12.  Summary
 Synch
 Entire blocks of characters are framed and
transmitted
 Expensive
 Efficient
 Need for BUFFER and accurate synch and
is required.

13.  Asynchronous
 Data is transmitted character by
character.
 Less costly… but not efficient
 No buffer is required… but channel will
remain unused

14. Type’s Of Media
 Guided media
 Signals are guided thru solid media
(like copper wire)
 Thru cables
 Unguided media
 Signals are not guided… not thru solid
medium (use of air)
 Usage of radio waves

15. Guided Media
 Twisted pair cable
 Two insulated wires (1mm thickness)
With each other
 Less expensive
 FD transmission
 Can be used for analog and digital
 Flow efficient is carries the signal
depends on thickness and distance
 Very efficient for short distance (less
then 100meters)

16.  More noise friendly
 Normally Used in LAN
 If more twisted per centimeter… results
less noise effect and better will be the
quality
 Easy to maintain
 If used less then 100 meters can give
up to 9600bps

17.  CO-AXIAL CABLE
 Better shielding … higher data bps
@longer distances …several tens of bps
at distances up to thousands feet
 Used for analog (75 ohm cable) and
digital (50 ohm cable) communication
 Costlier then twisted pair
Wire mesh conductor
Protective
Copper wire plastic
covering
Insulating material

18.  OPTICAL FIBER
 Inner core… glass/plastic… conducts
the light…size is in microns(1/25000
inch)
 Cladding … reflects the light
 Most expensive
 Data rate up to 100 mbps to 2Gbps
 No effect of EM noise
 Mainly for digital
 Half duplex (FD cause interference)

19. cladding
Fiber corer
jacket
Electrical signal Light signal To
To Electrical signal
Light converter Converter
Fiber optic

20. UNGUIDED MEDIA
 Radio wave can travel ideally with
the speed of light (in vacuum) –
cover long distance
 RF are omni directional
 RF is subjected to interference at
any frequency
Visible
Micro
light
Radio wave infrared UV X Ray
4 5 6 7 8 9 10 11 16
Hz

21.  TERRESTRIAL MICROWAVE TRAN.
 4 TO 6 GHz and 21 to 23 GHz
 Cheaper then fiber optic
 1 to 4 mbps travel in straight line
(hence line of sight is required)
 Cost depend on distance
 Long distance telephone, cellular, TV,
link to cities etc..

22.  SATELLITE MICROWAVE TRANS.
 One antenna is on a satellite
 4 -6 GHz and 11-14GHz
 Use of satellite- cost
 Normally uplink is 6 KHz and downlink
is 4 KHz
 Earth based station required careful
adjustment
 Can reach most remotes places on
earth

23.  INFRAERED
 Used for short distance communication
 Do not pass thru solid object
 Generally cheaper
 Used for wireless LAN, remote controls
etc..
 licensing is not required.

24. MODEMS
 Types
 A) Landline :- connected to PSTN…
having jacks RJ11
 Internal – inside computer
 External –separate device… outside the
computer… connected to serial port
 PCMCIA – small size normally used for
laptops.
 Personal computer memory card
(designed by) international associatioan.

25.  B) Wireless
 Radio transmitters/receiver generally used
for mobile device.
 RJ11 is not there instead they can access
thru radio waves.
 If it is out of range – no use.
 C) LAN
 Allow shared remote access to LAN.

26.  Standards
 Bell Modem :- designed by bell lab. There
are 103/113 series,202 series, 212 series,
201 series, and 208/9 series.
 ITU- T modem- V.22,V.26,V.29
 V.26 from 1200-2400 bps… user phase shift
keying.
 V.22 bit- 600 baud line… during each signal
period (baud) the modem conveys 4 data bit
600*4= 2400 bps.
 V.29 operating at 2400 baud *4 =9600 bps.

27. Encoding Techniques
 Analog data to Analog signal
 Digital data to Digital signal
 Digital data to Analog signal
 Analog data to Digital signal

28. Analog data to Analog signal
 Types of modulation
 1) Amplitude
Carrier

29. Modulated
Double side
band
Transmitted
carrier Amplitude Modulation

30.  Modulation
 To modulate to mix the signal with the carrier.
 Process of encoding signals (information) for the
transmission
 Translate the source signal, base band to a
band pass signal (high frequency compared to
the source frequency).
 Source signal – MODULATING signal.
 Band pass signal – MODULATED signal.
 MODULATION is done by varying the amplitude
or frequency of high frequency carrier according
to the modulating signal.

31.  Amplitude Modulation
 Amplitude of high frequency carrier signal
is varied accordance to the instantaneous
amplitude of the modulating signal.
 Easy
 Environment friendly.
 Strength decrease with distance.

32.  Frequency Modulation
 FM signal constant MODULATED but
frequency VARIES IN ACCORDING TO
THE SIGNAL to be transmitted.
 Mixing of two frequency high frequency
(carrier) with the signal (low
frequency) compound frequency
varying according to signal.
 Least affected by noise.
 Requires high bandwidth than AM.

33. Frequency Modulation carrier

34.  Phase Modulation
 The shape of the carrier signal (phase) is
made to change at given pint of time.
 The difference between two sine signals is a
phase angle… normally 180 out of phase.
 USES:- medium speed modems use phase
modulation to convert digital signals into
phase modulated signals. This process of
phase shifting keying (PSK) allows modem to
modulate and demodulate

35. Phase Modulation carrier

36. Digital data to Digital signal
 Digital data to digital signal
conversion.
 Equipment less complex and
expensive then digital data to
analog modulation equipment.
 One logic state represented by
positive the other by negative
voltage
 Data rate
 Rate of data transmission in bps.

37. Schemes of D to D
 1)Non return to zero –level (NRZ-L)
 To different voltage for 0 & 1 bits
 Voltage constant during bit interval
 No transmission i.e. return to 0 voltage
 E.g. absence of voltage for 0, constant
positive for 1
 More often negative voltage for 1 value
and positive for the other

38. NRZ-L
0 1 0 0 1 1 0 0 0 1

39.  2) non return to 0 interval
 Constant voltage pulse for duration of
bit
 Data encoded else presence or absence
of signal transmission at beginning of
bit time
 Transition (low to high or high to low)
denotes binary 1
 No transition denotes binary 0

40. NRZ-I
0 1 0 0 1 1 0 0 0 1

41.  3)Manchester
 Transition in middle of each bit period
 Transition serves as clock and time
 Low to high represent 1
 High to low represent 0

42. Manchester
0 1 0 0 1 1 0 0 0 1

43.  4)Defrential Manchester
 Mid bit transition is clocking only
 Transition at start of a bit period
represent 0
 No transition at start of a bit period
represent 1

44. Differential Manchester
0 1 0 0 1 1 0 0 0 1

45. Digital Data to Analog Signal
 Public telephone system
 300 Hz to 3400 Hz.
 Amplitude Shift Keying (ASK).
 Frequency Shift Keying (FSK).
 Phase Shift Keying (PSK).

46.  ASK (Amplitude Shift Keying)
 Values represented different amplitude
of carries.
 Usually one amplitude as 0.
 i.e. presence or absence of carrier is
used.
 Susceptible to sudden gain changes.
 Inefficient.
 Up to 1200 bps on voice grade line.
 Used over optical fiber.

47. ASK
0 0 1 1 0 1 0 0 0 1 0

48.  Binary Frequency Shift Keying
 Most common form is Binary FSK.
 Two binary values represented by 2
different frequencies (near carrier).
 Less susceptible to error than ASK.
 Up to 1200 bps on voice grade lines.
 High frequency radio .
 Even higher frequency on LANs using
co-ax.

49. BFSK
0 0 1 1 0 1 0 0 0 1 0

50.  Binary phase shift keying (BPSK)
 Phase of carrier signal is shifted to
represent data.
 Binary PSK
 Two phases represent two binary digits.
 Differential PSK
 Phase shifted relative to previous
transmission rather than some reference
signal.

51. 0 0 1 1 0 1 0 0 0 1 0

52. Analog Data To Digital Signal
 Digitization
 Conversion of analog data in to digital
data.
 Digital data can then be transmitted
using NRZ-L.
 Digital data can then be converted to
analog signal.
 Analog to digital conversion done using a
codec.
 Pulse code modulation conversion of
analog data in to digital data.

53. Digitizer Modulator
Analog data
Digital Data
(voice)

54.  Pulse code modulation
 It’s a digitizing process in which analog
is represented in digital form.
 The sound are transformed in to pulse
by codec…sampling of the amplitude of
the analog signals at very short interval
of time… the sampled valued converted
in to digital number of 0’s and 1’s… and
finally it is transmitted.

55.  At the receiving, the original A/D is
reversed… voltage values are converted
read and production of the exact signal
will be achieved.
 If a signal is sampled at regular interval at
a rate higher than twice the highest signal
frequency, the samples contain all the
information of the original signal.
 Voice data limited to below 4000Hz.
 Required 8000 samples per second.
 Each sample assigned digital value.

56.  CODEC (Compressor/DECompressor)
 Its an electronic circuit that convert analog
to digital.
 Converts human voice in to digital code
using pulse code modulation.
 The resulting digital signal can travel
through all digital communication
equipment… provides more reliable and less
costly compared to analog.
 Its also converting back to voice.
 CODEC electronics used in digital phone.

57. Multiplexing
 Multiplexing is a set of techniques that
allows the simultaneous transmission
of multiple signal across a single data
link.
 Whenever the transmission capacity of
a medium linking two devices is
greater then the transmission needs of
the devices, the link can be shared in
order to maintained the utilization of
the link, much at one cable can carry
a hundreds of TV channel.

58. MUX
FDM TDM
Synch Asynch

59.  Frequency division mux (FDM)
 In FDM signal generated by each sending
device modulated different carrier
frequencies. These modulated signals are
then combined in to a single composite signal
that can be transported by the link. The
carrier frequencies have to be different
enough to accommodate the modulation and
demodulation signals.
 (refer fig.) The first PC terminal is sending
“1010” where as second terminal is sending
“0110”. The multiplexing process starts by
applying amplitude modulation in to each
signal by using different carrier frequencies
as f1 and f2

60. FDM mux process
Amplitude
Modulation
101 0
With
Carrier f1
Modulated
signal +
Amplitude
0 11 0 Modulation
With
Carrier f2
Signal connected

61.  In demux process, we use filters to
decompose. The multiple signal in
to its constitute signals. Then each
signal is passed to a amplitude
demodulation process to separate
the carrier signal from the message
signal. Then the message signal is
sent to the waiting receiver.

62. Signal with
Carrier f1
Bandwidth f1
Amplitude 101 0
Filter
Filter
Amplitude 0 11 0
Bandwidth f2
Signal with
Carrier f2

63.  Time Division mux (TDM)
 In the TDM multiple transmission can
occupy a single link by subdividing
them and interleaving the portion. We
say that TDM is a round robin use of a
frequency.

64.  Synch TDM
 The mux allocate exactly the same time
slot each device at all times, whether or
not a device has any thing to transmit.
Time slot 1 ,for example is assigned to
device 1 alone and can not be used by
any other device.
 FRAME: In synch TDM, a frame consist of
one complete cycle of time slots. Thus the
number of slots in frame is equal to the
number of inputs.

65. Synch TDM: mux process
1
2
4321 4321 4321 4321
MUX
3
4

66. Synch TDM: mux process
1AAAA
2 BB
A D A D BA DCBA
MUX
3 C
4 DDD

67. Synch TDM: demux process
AAAA
D
BB
A D A D BA DCBA E
M
U
X C
DDD

68.  Asynch TDM
 In asynch TDM each slot in a frame is not
dedicated to the fix device. Each slot
contain an index of the device to be sent
to and a message. Thus the number of
slots in a frame is not necessary to be
equal to the number of inputs devices.
More than one slots in a frame can be
allocated for an input device. Asynch TDM
allows maximization the link. It allows a
number of lower speed input lines to be
multiplexed to a single higher speed line.

69. Synch TDM: mux process
1AAAA
BB
A D A D BA DCBA
MUX
C
DDD

71.  FRAME: In asynch TDM, a frame contain a
fix number of time slots. Each slot has an
index of which device to receive.

72. MULTIPLE ACCESS TECHNOLOGIES
FOR WIRELESS
COMMUNICATION

73. MULTIPLE ACCESS TECHNOLOGIES
FOR
WIRELESS COMMUNICATION
 COMMUNICATION : Fixed BAND of
Frequency Spectrum.
 Multiple Access Methods - WHY ?
 SHARE THE FREQUENCY SPECTRUM.
 Differentiates the signals from different
sources , without degrading the Quality.
 Different techniques of SHARING …
called Multiple Access Methods /
Techniques / Schemes / Technologies.

74. MULTIPLE ACCESS TECHNOLOGIES
FOR
WIRELESS COMMUNICATION
 THREE Basic Multiple Access Methods
currently in use :-
 FDMA
FREQUENCY DIVISION MULTIPLE ACCESS
 TDMA
TIME DIVISION MULTIPLE ACCESS
 CDMA
CODE DIVISION MULTIPLE ACCESS

75. FDMA
(Frequency Division Multiple Access)
Channel 2
Channel 3
Channel 5
Channel 4
Channel 1
User B
User E
User A
User D
User C
Frequency
F1 F2 F3 F4 F5
 Users SHARE the available spectrum in the
FREQUENCY domain.
 Assigns the individual CHANNEL ( Unique
Frequency) to users - Allocated band is called
TRAFFIC CHANNEL. Hence .. Different Users
…..Different Traffic Channels.

76. FDMA
(Frequency Division Multiple Access)
 If User A is in USE .. Channel 1 will not be
allotted to others. Disadvantage -> When
Channel is not in Use … can not be used by
others .. Wastage of Resource.
 Each Channel has Very LOW Bandwidth ….
Hence Implemented normally in Narrow band
Systems.
 Requires TIGHT filtering to reduce the
Channel Interference .
 Channel ID = Frequency Slot ID.

77. TDMA
(Time Division Multiple Access)
Time
T3 User C User F User I
T2 User B User E User H
T1 User A User D User G
Frequency
F1 F2 F3
 Spectrum is divided in narrow frequency bands
(Like FDMA) and further divided into a number of
time slots.
 Each User is allotted a Time Slot that permit access
to the frequency channel for that duration of the
time slot.

78. TDMA
(Time Division Multiple Access)
 Traffic Channel ID =
Frequency Slot ID + Time Slot
ID
 Periodic train of time slots … make a FRAME.
 Each User shares a frequency with several
users.
 Transmission for any user is non continuous.
 Allocation of different numbers of Time Slots
per frame to users … Better Utilization of
Spectrum…
 Analog Systems used FDMA .. Digital Systems
used TDMA.

79. Spread Spectrum Multiple
Access
 PN Code - pseudo-noise code …
random binary Sequence / Code.
 SSMA - a) Frequency Hopped Multiple
Access (FHMA) & b) Direct Sequence Multiple
Access(DSMA).
 FHMA :- Carrier Frequencies of individual user
are VARIED in a pseudo random way.
 Based on the PN code of the user .. Each user
occupy the narrow band channel at one
particular time.
 Because of the PN … Signals changes channels
rapidly.
 Difference between FHMA & FDMA is that the
FHMA signal changes channels at rapid interval.

80. CDMA
(Code Division Multiple Access)
PN codes
Code 3 User C
Code 2 User B
Code 1 User A
Frequency
F1
 DSMA is also called CDMA.
 Unique PN code is assigned to unique user.
 Users share the Block of frequency spectrum on
the basis of PN code.

81. CDMA
(Code Division Multiple Access)
 Channel ID = PN Code ID
 Utilizes the entire spectrum of allotted spectrum
-
 All the PN code modulated signals from the users
are transmitted over the entire spectrum. And
at the receiving end the signals classified as
per the copy of PN sequence .
 Unlike FDMA - TDMA … There is no LIMIT of
number of users … but increase in users
degrades the quality.
 Each user operate independently with NO
knowledge of other users.

82. CORDLESS TELEPHONE
SYSTEMS
Public
Telephone Fixed Station -
Network ..
(DoT) Base Station
Handset
 Cordless Telephone System -
provide the user limited range and
mobility. Coverage rang is few
Tens of Meters to Few hundred
Meters.

83. CELLULAR TELEPHONE
SYSTEMS
 The concept was developed in early 70’s by
Bell Laboratories
 Extension of your wireless connection to the
public telephone network for any user location
within the range of the system.
 The principle of cellular system…To divide a
large geographic area into cells.
 Each adjacent Cell Transmitters operate on
different frequencies to avoid interference.

84. CELLULAR TELEPHONE
SYSTEMS
 Transmitted power and height of antenna of each
CELL is low so that the same set of frequency can
be used for different cells far apart.
 Hence theoretical coverage range and capacity of a
cellular system are therefore UNLIMITED.
 Each Cell is represented by HEXAGONE.

85. A cellular System –
An Overview.
Public
Telephone
Network
Mobile
Switching
Center
To Other MSC MSC
 Basic Cellular System - Mobile Stations+Base
Stations+Mobile Switching Center.

86. A cellular System -
An Overview.
 Mobile Station - Contains a transceiver+
antenna+Control Circuitry
 Base Station - Bridge between MS and MSC
 MSC - Coordinated the activities of all BS and
connect them to PTN. Plus Billing & System
Maintenance.
 The Channel used for VOICE transmission from
BS to MS …called Forward Voice Channel (FVC).
 The Channel used for VOICE transmission from
MS to BS …called Reverse Voice Channel (RVC).

87. How it WORKS ?
 When MS is turned ON … Searches for the
strongest FVC.
 When a Call is made for MS.. MSC dispatches
the request to all BS.
 The Mobile Number is broadcasted as a paging
message.
 MS acknowledges the Paging message.
 BS relays this ACK to MSC .
 MSC instructs the BS to select particular
frequency Channel for communication .

88. How it WORKS ?
 BS TO RING sends DATA message in FVC TO
RING the MS.
 During CALL .. MSC handles the transmitted
power and controls the channel between BS
and MS in order to maintain the Quality ( as MS
is likely in MOBILE mode)
 When MS goes out of range of BS … called
HANDOFF …
 Two other Channels are also Used besides FVC
& RVC … a) FCC & b) RCC

89. How it WORKS ?
Call from
MSC DoT. Sends
Number to
all BS
Paging
Message for
FCC MS
RCC
BS
FVC
RCC
Receives
FCC Paging
Message
RVC
MS
FVC
RVC
TIME

90. How it WORKS ?
 When MS Originates Call… sends all information
to BS.
 BS passes information to MSC
 MSC Validates .. And If required help from
Public Telephone Network requested.
 And the two way PATH will be maintained till
the Call Lasts.

91. Handoff
 During the ongoing call if BS senses the LOW
power Quality from MS , it requests
neighboring BS to check the signal level .
( This happens when MS moves to different cell
while in USE)
 If the signal is BETTER , current BS signals the
MS to switch over to new BS and inform the
new BS to take over.
 This change of SPEECH channel is called
“Handoff”
 This changeover will not be noticed /
experienced by the user.

92. Frequency REUSE
E
E F C
F C A
G B
A B D
G
D
 BS in adjacent cells are assigned channel
groups … totally different from the neighboring
cells.
 BS antennas are designed to cover the
particular cell.

93. Wireless Systems Standards

94. 1G Cellular Systems
 Based on Analog Cellular Systems
Concept
 Depends on Frequency Band , Channel
Spacing and channel coding
 Individual calls use different channels
and the Spectrum is shared on the
basis of FDMA
 Uses Analog FM for speech
transmission
 Normally uses 7 Cell reuse pattern –
provision for Cell splitting.

95. 2G Cellular System
 Completely DIGITAL Cellular System
 Increased in Capacity ( 3 to 10 times)
 MS Terminal Size Reduction
 Reduces the Power requirements … Increases
the battery life
 Improved Reception
 Highly Secured … Interference prone
environment.
 Cell Splitting … Better
 Wide Area Roaming
 More Popular

96. 2G Cellular System
 Spectrum Sharing in the digital
environment can be based on ;
 TDMA : Each Radio Channel is partitioned in to
number of time slots - each user is assigned a
frequency/time slot COMBINATION
 CDMA : A radio Channel is used
SIMULTANEOUSLY by multiple mobile users ,
and the signals from different users are
distinguished by SPREADING them on the
basis of PN code.

97. Global System for Mobile
(GSM)
 Introduced in Europe in 1990.
 World’s most popular standard now.
 A memory device that stores the
subscriber Id , Networks, Countries where
he’s entitled to get services , personal
information is inserted into GSM phones .
(Subscriber Identity Module - SIM).
Example TOI dated 18th March.
 Without SIM – non operational.
 Encryption is possible … More secured

98. GSM Architecture
HLR
MSC Other MSC
VLR PSTN
AUC BSC BTS

99. GSM Architecture
 MS (Mobile Station)
• Low Power Requirement…0.8-8.0w
• SIM is Required
 BSS (Base Station System)
• BSC+BTS (Base Transceiver Station)
• Responsible For Radio Channel Allocation/
Monitoring (BSC)
• Power Control (BSC)
• Handoff Management (BSC) – Reduce The Burden
of MSC
• Digital Signal Processing (BTS)

100. GSM – System Architecture
 MSC
 Doesn’t contain Info regarding MS .
 Call Setup, Supervision & End / Routing
 BILLING
 MOBILITY Management
 Management with Other MSCs , PSTN .
 Home Location Register – HLR
 Centralized Database of MS falling under MSC
 Refer for every Incoming Call

101. GSM – System Architecture
 VLR – Visitor Location Register
 Temporarily stores the MS … Each roaming MS
visiting MSC.
 AUC – Authentication Center
 Strongly protected database which handles the
authentication and encryption keys of every MS
Interfaces :
Between BSC & MSC ::: A Interface
Between BSC & BTS ::: Abis Interface
Between BTS & MS ::: GSM Radio Air Interface
SS7 Protocol ::: Signal Correction control part

102. GSM Specifications
 RC :: 890 – 915 MHz
 FC :: 935 – 960 MHz
 Separation ::: 45 MHz
 Channel Spacing ::: 200 kHz
 Each Channel is TIME SHARED
between 8 subscribers using TDMA
 Total number of channel :::
125 (25MHz bandwidth) * 08 = 1000
approximately

103. GSM Specifications
 Channel Frame :
156.25bits
576.92μs
TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7
4.615ms

104. GSM Traffic Channels
 Traffic Channels (TCHs)
 Carry digitally encoded user SPEECH or DATA
 Control Channels (CCHs)
 Carry signaling and synchronizing commands
between BS & MS
 Full Rate :
 User Speech / Data … one TS per Frame
 Half Rate :
 Same time slot but sent in alternate frames
 Two half rate channel users would share the
same time slot but would alternately transmit
during every other frame

105. TCHs - Types
 Full Rate TCH
 TCH/FS … Full rate speech channel carries
@13kbps
 TCH/F9.6 … Full rate DATA channel @9600bps
 TCH/F4.8 … Full rate DATA channel @4800bps
 TCH/F2.4 … Full rate DATA channel @2400bps
 Half Rate TCH
 TCH/HS … half rate of the full rate channel …
6.5kbps
 TCH/H4.8 …half rate DATA @4800bps
 TCH/H2.4 …half rate DATA @2400bps

106. CCH - Types
 Three Main Control Channels – Broadcast
Channel (BCH), Common Control Channel
(CCCH) & DEDICATED Control Channel
(DCCH)
 BCH – Operates only on Forward link …
Synchronization for all MS
 Broadcast Control Channel – BCCH … used to
broadcast info. Such as cell & network identity
. Plus … Channel structure , channel
availability and congestion parameters.
 Frequency Correction Channel – FCCH …
allows each MS to synchronize its internal
frequency as of BS
 Synchronization Channel – SCH … used to
identify the serving BTS

107. CCH - Types
 Common Control Channel – CCCH – used
to page specific MS , assign signaling
signals to specific MS and receive
requests for service from MS
 Paging Channel – PCH … provides paging
signals from BSC to all MS in the cell … used
to provide cell broadcast ASCII text messages
to all MS – SMS feature.
 Random Access Channel – RACH … reverse
link used by MS .. Used by MS to originate
calls
 Access Grant Channel – AGCH … used by the
BSC to provide forward link communication
to the MS and carries signals which instructs

108. CCH - Types
 Dedicated Control Channels (DCCH) – bi-
directional in nature like traffic channels …
 Stand-alone Dedicated Control Channel –
SDCCH …ensures that MS will remain
connected with BSC while MSC verify the MS …
 Slow Associated Control Channel – SACCH …
carries general info. Between the BTS and MS…
on the forward , regular signals to MS like
transmitted power … in reverse , it carries
received signal strength , quality of TCH info.
 Fast Associated Control Channel – FACCH …
carries urgent messages same as of SDCCH …
urgent message like handoff request .