Air
Interfac
e &
Protocol
overview
Air interface
Frequency, Frequency Band, EM Spectrum
TDD,FDD
Frame structure
A signal is a set of information of data
What is signal ?
What is wave ?
What is Frequency ?
Band Vs Bandwidth
Bandwidth is the difference between the upper and lower frequencies in a
continuous band of frequencies. ... A key characteristic of bandwidth is that
any band of a given width can carry the same amount of information,
regardless of where that band is located in the frequency spectrum
What is wavelength?
• The wavelength is the distance a radio
wave will travel during one cycle. The
formula which relates the wavelength to the
frequency is the following:
λ = c/f
EM spectrum
Extremely low frequency (ELF) 30 Hz to 300 Hz. Power line frequencies and low end of human audio.
Voice frequency (VF) 300 Hz to 3000 Hz. Typical range associated with human voice.
Human hearing 20 Hz to 20 kHz
Very low frequency (VLF) 3 kHz to 30 kHz. Used for communications with submerged submarines
Low frequency (LF) 30 kHz to 300 kHz. Long range radio navigation.
Medium frequency (MF) 300 kHz to 3000 kHz. AM radio and long-range communication.
High frequency (HF) 3 MHz to 30 MHz Known as “short wave”, used by two-way radio
Very high frequency (VHF) 30 MHz to 300 MHz Radio communications and FM radio.
Ultra high frequency (UHF) 300 MHz to 3000 MHz TV, military and cell phones
Super high frequency (SHF) 3 GHz to 30 GHz. Microwave. Satellite communications and radar.
Extremely high frequency (EHF) 30 GHz to 300 GHz. Satellite communications
Carrier frequency
In the communication system, the carrier which carries information from transmitter to receive or
vise versa is a frequency that called carrier frequency. How much data can be sent on the carrier and
how far it can reach depends on frequency, on its bandwidth, tha band power of transmission, type
of antenna, wireless channel condition, condition, Transmitter/ receiver characteristics
Frequency Band and Carrier B/W
Wireless Technology
GSM,GPRS,EDGE
CDMA
WCDMA,HSPA,HSPA+
LTE(Rel 8)
LTEA
WiFi
Bluetooth
Microwave
Frequency Band
900,1800,1900 MHz
800,2100 MHz
850,2100 MHz
Multiple Bands ( 1 to 40)
Multiple Bands ( 1 to 40)
2.4 GHz/ 5 GHz
2.4 GHz
6-38 GHz
Carrier Bandwidth
200 KHz
1.25 MHz
5 MHz
1.4/3/5/10/15/20Mhz
Upto 100 MHz
20/40/80 MHz
1/2 MHz
3.5/7/14/28/56 MHz
Multiplexing vs Multiple access!
Need ?
• Multiple access just means many can access at one time, Ethernet is multiple access, token ring is
not. Multiplexing is process to combine multiple signal for transmit it over a single channel or media.
generally multiplexing combines several low-speed signals for transmission over a single high-speed
connection
• Need 
• Spectrum is limited recourse
• Accommodate more user in limited bandwidth
• More effective way of transmission in long distance communication
• Reduces implementation cost
• In wireless telecom if LOS is not available with receiver, traffic can be multiplexed with nearest node
Technology vs Access technique
Wireless Technology
GSM,GPRS,EDGE
CDMA
WCDMA,HSPA,HSPA+
LTE(Rel 8)
LTEA
Access Technique
FDMA/TDMA
CDMA
CDMA
OFDMA/SCFDMA
OFDMA/SCFDMA
Modulation! Need for Modulation ?
• Process of varying one or
more properties of a
periodic waveform, called
the carrier signal, with a
modulating signal that
typically contains
information to be
transmitted.
Need
1-Antenna length or Hight of
antenna.
2-Power
3-Mixing of signal
Wireless Technology Modulation
Schemes
Wireless Technology
Modulation Technique
GSM,GPRS
GMSK
EDGE
GMSK,8PSK
CDMA
QPSK,BPSK
WCDMA,HSPA,HSPA+
QPSK,BPSK,16 QAM,64 QAM
LTE(Rel 8),LTEA
16 QAM,64 QAM
WiFi
64 QAM, 16 QAM , QPSK
Microwave
256 QAM , 512 QAM
GSM Air Interface
Um
• Uses Physical FDMA/TDMA/FDD
• In 900 MHz band:890-915 MHz Uplink band,935-960 MHz Downlink.
• Radio carrier is a 200 kHz=> 125 pairs of radio channels called absolute
radio frequency channel number (ARFCN).
• Duplex spacing is 45 MHz
• Channel & ARFCN will differ according to Band
• A TDMA frame is defined on the radio carrier (8 users per carrier)
GSM-FDMA/TDMA
GSM normal Burst Vs specific
burst.
Framing Scheme in GSM
Structure of Multi-Frame
Channel concept , Physical
channel Vs Logical channel
• One timeslot of a TDMA-frame on one carrier
is referred to as a physical channel.
There are 8 physical channels per carrier in
GSM,channel 0-7(timeslot 0-7)
The combination of an ARFCN and a time slot defines a physical channel
• A great variety of information must be
transmitted between BTS and the MS,for e.g.
user data and control signaling.Depending
on the kind of information transmitted we
refer to different logical channels.These logical
channels are mapped on physical channel.
Logical Channels on Air interface
GSM
Protocol
s
GSM
Protocol
Stack
GSM Protocol Stack
• Three Layers specified in the protocol
• Network layer has three sublayers
• 1. Call Management Establishment, maintenance, and termination of circuit-switched calls.
• 2. Mobility Management Registration, authentication, and location tracking.
• 3. Radio Resource Management  Establishment, maintenance, and termination of radio channel
connections.
• Link Layer  Uses variation of ISDN LAPD protocol – termed LAPDm
Physical layer Time slot on a 200 KHz carrier – absolute radio frequency channel number (ARFCN)
• Wideband code division multiple access (WCDMA)
• -The air radio interface standard for UMTS
•
-Wideband direct sequence spread spectrum
• -Variable orthogonal spreading of multiple access (OVSF)
• Type of Interface
• -FDD,TDD or dual mode
WCDMA
• Wide range of data rates due to CDMA with variable
spreading, coding and modes
• – Varying user bit rate is mapped to variable power and
spreading
• – Different services can be mixed on a single carrier for a
user
• 5-MHz Channel (25 GSM channels)
• – Each service provider can deploy multiple 5MHz carriers
at same cell site
• – Each 5 MHz shared by multiple subscribers using CDMA
• – Maximum chip rate = 3.84 Mchips/sec
WCDMA
• • Standard advantages of CDMA
• – Soft handoff
– Frequency reuse cluster size of 1,
• – Better quality in multipath environment
• – RAKE receiver
• • QPSK modulation
Scrambling and Channelization
• • Channelization codes are orthogonal codes – Separates transmissions from the same source
• – Uplink: used to separate different physical channels from the same UE
• – voice and data session
• – Downlink: used to separate transmissions to different physical channels and different UEs –
UMTS uses orthogonal variable spreading codes
• • Scrambling (pseudo noise scrambling) – Applied on top of channelization spreading
• – Separates transmissions from different sources
• – Uplink effect: separate mobiles from each other – Downlink effect: separate base stations
from each other
Spreading Principle
Channelization
Codes & OVSF
UMTS FDD
frame structure
UMTS Protocol
UMTS protocol
stacks
Protocols for the Control Plane
in WCDMA RAN
NAS
NAS
RRC
RRC
RANAP
RANAP
RLC
RLC
SCCP
SCCP
MAC
MAC
MTP-3b
MTP-3b
FP
FP
NNI-SAAL
NNI-SAAL
AAL2
AAL2
AAL5
AAL5
ATM
ATM
ATM
ATM
Uu
Layer 1
Layer 1
Layer 1
UE
RBS
Iub
Layer 1
Layer 1
RNC
Iu
Layer 1
CN
Uu Protocol Structure
Control Plane
NAS
User Plane
User Radio Bearers
Layer 3
RRC
Control
Measurements
control
PDCP
BMC
Signaling Radio Bearers
RLC
RLC
Layer 2
Control
Logical Channels
MAC
Transport Channels
Physical
PhysicalLayer
layer
NAS – Non Access Stratum
BMC- Broadcast Multicast Control
MAC – Medium Access Control
Layer 1
RRC – Radio Resource Control
RLC – Radio Link Control
PDCP – Pcket Data Convergence Protocol
Interaction between WCDMA
Protocols, Mapping of Channels
CTRL
USER
DATA
USER
DATA
CTRL
RRC
RRC
L3/RRC
Signaling
Radio Bearer
Radio Bearer
RLC
RLC
RLC
RLC
L2/RLC
Logical Channel
MAC
MAC
L2/MAC
PHY
L1
Transport Channel
PHY
Physical Channel
UE
UTRAN
LTE Physical Layer
User #1 scheduled
Δf=15kHz
User #2 scheduled
› Downlink: Adaptive OFDM
– Channel-dependent scheduling and link adaptation
in time and frequency domain
User #3
scheduled
› Uplink: SC-FDMA with dynamic bandwidth (Pre-coded OFDM)
– Low PAPR  Higher power efficiency
– Reduced uplink interference (enables intra-cell
orthogonality )
frequency
› Multi-Antennas, both RBS and terminal
– MIMO, antenna beams, TX- and RX diversity, interference rejection
– High bit rates and high capacity
• Flexible bandwidth
• Possible to deploy in 6 different bandwidths
up to 20 MHz
› Harmonized FDD and TDD concept
1.4
– Maximum commonality between FDD and TDD
› Minimum UE capability: BW = 20 MHz
3
5
FDD-only
180 kHz
frequency
TX
10
RX
15
20 MHz
Half-duplex FDD
fDL
fDL
fUL
fUL
TDD-only
fDL/UL
LTE Physical Layer
User #1 scheduled
Δf=15kHz
User #2 scheduled
› Downlink: Adaptive OFDM/OFDMA
– Channel-dependent scheduling and link adaptation
in time and frequency domain
User #3
scheduled
OFDMA
› Uplink: SC-FDMA with dynamic bandwidth (Pre-coded OFDM)
– Low PAPR  Higher power efficiency
– Reduced uplink interference (enables intra-cell
orthogonality )
– Channel-dependent scheduling and link adaptation
in time and frequency domain
OFDM
frequency
frequency
180 kHz
LTE Channel Bandwidth
Channel Bandwidth [MHz]
Transmission Bandwidth Configuration [RB]
Channel edge
Resource block
Channel edge
Transmission
Bandwidth [RB]
DC carrier (downlink only)
Active Resource Blocks
Channel Bandwidth [MHz]
Number of Resource Blocks
1.4
3
5
10
15
20
6
15
25
50
75
100
OFDMA/SC-FDMA (Time Domain)
10 msec Radio Frame
Resource
Block
1 msec Sub-fame
carries 14 symbols
Sub-carrier
#1
Sub-carrier
#12
A CP > Delay Spread
will completely
remove ISI as the
receiver sees each
reflection is seen as
the same symbol
 71.4 s
CP
 4.7 s
Symbol
 66.7 s
LTE Downlink Physical Rates
10 msec
168 168 168 168 168 168 168 168 168 168
1.4 MHz BW => 6 RBs
Frequency
3 MHz BW => 16 RBs
5 MHz BW => 25 RBs
10 MHz BW => 50 RBs
15 MHz BW => 75 RBs
20 MHz BW => 100 RBs
168 168 168 168 168 168 168 168 168 168
Eg 168 X 10 X 100 = 168000 symbols in 10 msec = 16.8 Msps
= 100.8 Mbps using 64 QAM and 201.6* Mbps using 64 QAM and MIMO
* User rate will be less due to signaling and adaptive coding overhead
LTE/EPC Control Plane
S1-M
Uu
UE
NAS
RRC
PDPC
RLC
MAC
L1
MME
S-GW
S11
S5/S8
PDN-GW
eNodeB
RRC
PDPC
RLC
MAC
L1
Relay
S1-AP
SCTP
IP
L2
L1
NAS
S1-AP
SCTP
IP
L2
L1
Relay
Relay
GTPv2-C
GTPv2-C
GTPv2-C
GTPv2-C
UDP
IP
L2
L1
UDP
IP
L2
L1
UDP
IP
L2
L1
UDP
IP
L2
L1
LTE/EPC User Plane
S1-U
Uu
S5/S8
PDN-GW
eNodeB
UE
Application
IP
PDPC
RLC
MAC
L1
S-GW
PDPC
RLC
MAC
L1
Relay
GTPv1-U
UDP/IP
L2
L1
GTPv1-U
UDP/IP
L2
L1
Relay
GTPv1-U
UDP/IP
L2
L1
IP
GTPv1-U
UDP/IP
L2
L1
SGi
Thank You