20CS2007 Computer Communication Networks

20CS2007
Computer Communication
Networks
Module 4
Wireless Wide Area Networks and LTE Technology Design Private and public leased networks. Video
conferencing, television and radio broadcast transmissions. Wireless WAN, Cellular Networks, Mobile IP
Management in Cellular Networks, Long-Term Evolution (LTE) Technology, Wireless Mesh Networks (WMNs)
with LTE, Characterization of Wireless Channels.
Dr.A.Kathirvel, Professor,
DCSE, KITS
kathirvel@karunya.edu

3
Wireless networks
 Access computing/communication services, on the move
 Wireless WANs
– Cellular Networks: GSM, GPRS, CDMA
– Satellite Networks: Iridium
 Wireless LANs
– WiFi Networks: 802.11
– Personal Area Networks: Bluetooth
 Wireless MANs
– WiMaX Networks: 802.16
– Mesh Networks: Multi-hop WiFi
– Adhoc Networks: useful when infrastructure not available

4
Limitations of the mobile environment
 Limitations of the Wireless Network
 limited communication bandwidth
 frequent disconnections
 heterogeneity of fragmented networks
 Limitations Imposed by Mobility
 route breakages
 lack of mobility awareness by system/applications
 Limitations of the Mobile Device
 short battery lifetime
 limited capacities

Mobile communication
 Wireless vs. mobile Examples
  stationary computer
  laptop in a hotel (portable)
  wireless LAN in historic buildings
  Personal Digital Assistant (PDA)
 Integration of wireless into existing fixed networks:
– Local area networks: IEEE 802.11, ETSI (HIPERLAN)
– Wide area networks: Cellular 3G, IEEE 802.16
– Internet: Mobile IP extension

6
Wireless v/s Wired networks
 Regulations of frequencies
– Limited availability, coordination is required
– useful frequencies are almost all occupied
 Bandwidth and delays
– Low transmission rates
• few Kbits/s to some Mbit/s.
– Higher delays
• several hundred milliseconds
– Higher loss rates
• susceptible to interference, e.g., engines, lightning
 Always shared medium
– Lower security, simpler active attacking
– radio interface accessible for everyone
– secure access mechanisms important

384 Kbps
56 Kbps
54 Mbps
72 Mbps
5-11 Mbps
1-2 Mbps 802.11
Wireless Technology Landscape
Bluetooth
802.11b
802.11{a,b}
Turbo .11a
Indoor
10 – 30m
IS-95, GSM, CDMA
WCDMA, CDMA2000
Outdoor
50 – 200m
Mid range
outdoor
200m – 4Km
Long range
outdoor
5Km – 20Km
Long distance
com.
20m – 50Km
µwave p-to-p links
.11 p-to-p link
2G
3G

8
Reference model
Application
Transport
Network
Data Link
Physical
Medium
Data Link
Physical
Application
Transport
Network
Data Link
Physical
Data Link
Physical
Network Network
Radio

9
Effect of mobility on protocol stack
 Application
– new applications and adaptations
– service location, multimedia
 Transport
– congestion and flow control
– quality of service
 Network
– addressing and routing
– device location, hand-over
 Link
– media access and security
 Physical
– transmission errors and interference

10
Perspectives
 Network designers: Concerned with cost-effective
design
– Need to ensure that network resources are efficiently utilized
and fairly allocated to different users.
 Network users: Concerned with application services
– Need guarantees that each message sent will be delivered
without error within a certain amount of time.
 Network providers: Concerned with system
administration
– Need mechanisms for security, management, fault-tolerance
and accounting.

12
Factors affecting wireless system design
 Frequency allocations
– What range to operate? May need licenses.
 Multiple access mechanism
– How do users share the medium without interfering?
 Antennas and propagation
– What distances? Possible channel errors introduced.
 Signals encoding
– How to improve the data rate?
 Error correction
– How to ensure that bandwidth is not wasted?

13
Frequencies for communication
 VLF = Very Low Frequency UHF = Ultra High Frequency
 LF = Low Frequency SHF = Super High Frequency
 MF = Medium Frequency EHF = Extra High Frequency
 HF = High Frequency UV = Ultraviolet Light
 VHF = Very High Frequency
 Frequency and wave length:  = c/f
 wave length , speed of light c  3x108m/s, frequency f
1 Mm
300 Hz
10 km
30 kHz
100 m
3 MHz
1 m
300 MHz
10 mm
30 GHz
100 m
3 THz
1 m
300 THz
visible light
VLF LF MF HF VHF UHF SHF EHF infrared UV
optical transmission
coax cable
twisted
pair

14
Wireless frequency allocation
 Radio frequencies range from 9KHz to 400GHZ (ITU)
 Microwave frequency range
– 1 GHz to 40 GHz
– Directional beams possible
– Suitable for point-to-point transmission
– Used for satellite communications
 Radio frequency range
– 30 MHz to 1 GHz
– Suitable for omnidirectional applications
 Infrared frequency range
– Roughly, 3x1011 to 2x1014 Hz
– Useful in local point-to-point multipoint applications within confined
areas

15
Frequencies for mobile communication
 VHF-/UHF-ranges for mobile radio
– simple, small antenna for cars
– deterministic propagation characteristics, reliable connections
 SHF and higher for directed radio links, satellite
communication
– small antenna, focusing
– large bandwidth available
 Wireless LANs use frequencies in UHF to SHF spectrum
– some systems planned up to EHF
– limitations due to absorption by water and oxygen molecules
(resonance frequencies)
• weather dependent fading, signal loss caused by heavy
rainfall etc.

16
Frequency regulations
 Frequencies from 9KHz to 300 MHZ in high demand
(especially VHF: 30-300MHZ)
 Two unlicensed bands
– Industrial, Science, and Medicine (ISM): 2.4 GHz
– Unlicensed National Information Infrastructure (UNII): 5.2 GHz
 Different agencies license and regulate
– www.fcc.gov - US
– www.etsi.org - Europe
– www.wpc.dot.gov.in - India
– www.itu.org - International co-ordination
 Regional, national, and international issues
 Procedures for military, emergency, air traffic control, etc

17
Wireless transmission
 Wireless communication systems consist of:
– Transmitters
– Antennas: radiates electromagnetic energy into air
– Receivers
 In some cases, transmitters and receivers are
on same device, called transceivers.
Transmitter Receiver
Antenna
Antenna

18
Transmitters
Amplifier
Oscillator
Mixer Filter Amplifier
Antenna
Transmitter
Suppose you want to generate a signal that is sent at 900 MHz and
the original source generates a signal at 300 MHz.
•Amplifier - strengthens the initial signal
•Oscillator - creates a carrier wave of 600 MHz
•Mixer - combines signal with oscillator and produces 900 MHz
(also does modulation, etc)
•Filter - selects correct frequency
•Amplifier - Strengthens the signal before sending it
Source

20
Antennas
 An antenna is an electrical conductor or system of
conductors to send/receive RF signals
– Transmission - radiates electromagnetic energy into space
– Reception - collects electromagnetic energy from space
 In two-way communication, the same antenna can be
used for transmission and reception
Omnidirectional Antenna
(lower frequency)
Directional Antenna
(higher frequency)

21
 Radiation and reception of electromagnetic waves,
coupling of wires to space for radio transmission
 Isotropic radiator: equal radiation in all directions
(three dimensional) - only a theoretical reference
antenna
 Real antennas always have directive effects
(vertically and/or horizontally)
 Radiation pattern: measurement of radiation around
an antenna
Antennas: isotropic radiator
z
y
x
z
y x ideal
isotropic
radiator

22
Antennas: simple dipoles
 Real antennas are not isotropic radiators
– dipoles with lengths /4 on car roofs or /2 (Hertzian dipole)
 shape of antenna proportional to wavelength
 Gain: maximum power in the direction of the main lobe
compared to the power of an isotropic radiator (with the
same average power)
side view (xy-plane)
x
y
side view (yz-plane)
z
y
top view (xz-plane)
x
z
simple
dipole
/4 /2

23
Antennas: directed and sectorized
side view (xy-plane)
x
y
side view (yz-plane)
z
y
top view (xz-plane)
x
z
top view, 3 sector
x
z
top view, 6 sector
x
z
 Often used for microwave connections or base stations
for mobile phones (e.g., radio coverage of a valley)
directed
antenna
sectorized
antenna

24
Antenna models
In Omni Mode:
 Nodes receive signals with gain Go
In Directional Mode:
 Capable of beamforming in specified direction
 Directional Gain Gd (Gd > Go)

25
Directional communication
Received Power  (Transmit power)
*(Tx Gain) * (Rx Gain)
Directional gain is higher
Directional antennas useful for:
 Increase “range”, keeping transmit power constant
 Reduce transmit power, keeping range comparable
with omni mode

26
Comparison of omni and directional
Issues Omni Directional
Spatial Reuse Low High
Connectivity Low High
Interference Omni Directional
Cost & Complexity Low High

27
Antennas: diversity
 Grouping of 2 or more antennas
– multi-element antenna arrays
 Antenna diversity
– switched diversity, selection diversity
• receiver chooses antenna with largest output
– diversity combining
• combine output power to produce gain
• cophasing needed to avoid cancellation
+
/4
/2
/4
ground plane
/2
/2
+
/2

Signal Propagation and Modulation

29
Signals
 physical representation of data
 function of time and location
 signal parameters: parameters representing the value of
data
 classification
– continuous time/discrete time
– continuous values/discrete values
– analog signal = continuous time and continuous values
– digital signal = discrete time and discrete values
 signal parameters of periodic signals:
period T, frequency f=1/T, amplitude A, phase shift 
– sine wave as special periodic signal for a carrier:
s(t) = At sin(2  ft t + t)

30
Signal propagation ranges
distance
sender
transmission
detection
interference
 Transmission range
– communication possible
– low error rate
 Detection range
– detection of the signal
possible
– no communication
possible
 Interference range
– signal may not be
detected
– signal adds to the
background noise

31
Attenuation: Propagation & Range

32
Attenuation
 Strength of signal falls off with distance over
transmission medium
 Attenuation factors for unguided media:
– Received signal must have sufficient strength so that
circuitry in the receiver can interpret the signal
– Signal must maintain a level sufficiently higher than
noise to be received without error
– Attenuation is greater at higher frequencies, causing
distortion
 Approach: amplifiers that strengthen higher
frequencies

33
Signal propagation
 Propagation in free space always like light (straight line)
 Receiving power proportional to 1/d²
(d = distance between sender and receiver)
 Receiving power additionally influenced by
– fading (frequency dependent)
– shadowing
– reflection at large obstacles
– refraction depending on the density of a medium
– scattering at small obstacles
– diffraction at edges
reflection scattering diffraction
shadowing refraction

34
 Signal can take many different paths between sender
and receiver due to reflection, scattering, diffraction
 Time dispersion: signal is dispersed over time
  interference with “neighbor” symbols, Inter
Symbol Interference (ISI)
 The signal reaches a receiver directly and phase shifted
  distorted signal depending on the phases of the
different parts
Multipath propagation
signal at sender
signal at receiver
LOS pulses
multipath
pulses

35
Effects of mobility
 Channel characteristics change over time and location
– signal paths change
– different delay variations of different signal parts
– different phases of signal parts
  quick changes in the power received
(short term fading)
 Additional changes in
– distance to sender
– obstacles further away
  slow changes in the average power
received (long term fading)
short term fading
long term
fading
t
power

36
Propagation modes
Earth
Earth
Earth
a) Ground Wave Propagation
b) Sky Wave Propagation
c) Line-of-Sight Propagation
Transmission
Antenna
Receiving
Antenna
Signal
Signal
Ionosphere
Signal

Chapter 16
Wireless WANs:
Cellular Telephone
and Satellite Networks
and Satellite Networks
16.1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

16
16-
-1
1 CELLULAR TELEPHONY
CELLULAR TELEPHONY
Cellular
Cellular telephony
telephony is
is designed
designed to
to provide
provide
p y
p y g
g p
p
communications
communications between
between two
two moving
moving units,
units, called
called
mobile
mobile stations
stations (MSs),
(MSs), or
or between
between one
one mobile
mobile unit
unit and
and
( ),
( ),
one
one stationary
stationary unit,
unit, often
often called
called a
a land
land unit
unit.
.
Topics discussed in this section
Topics discussed in this section
Frequency-Reuse Principle
Transmitting
Topics discussed in this section:
Transmitting
Receiving
Roaming
g
First Generation
Second Generation
16.2
Third Generation

Figure 16.1 Cellular system
16.3

Figure 16.2 Frequency reuse patterns
16.4

N t
AMPS is an analog cellular phone
Note
AMPS is an analog cellular phone
system using FDMA.
16.5

Figure 16.3 Cellular bands for AMPS
16.6

Figure 16.4 AMPS reverse communication band
16.7

Figure 16.5 Second-generation cellular phone systems
16.8

Note
D-AMPS, or IS-136, is a digital cellular
h t i TDMA d FDMA
phone system using TDMA and FDMA.
16.10

Figure 16.9 Multiframe components
16.13

Note
GSM is a digital cellular phone system
Note
GS s a d g ta ce u a p o e syste
using TDMA and FDMA.
16.14

Figure 16.10 IS-95 forward transmission
16.15

Figure 16.11 IS-95 reverse transmission
16.16

Note
IS-95 is a digital cellular phone system
i CDMA/DSSS d FDMA
using CDMA/DSSS and FDMA.
16.17

Note
The main goal of third-generation
ll l t l h i t id
cellular telephony is to provide
universal personal communication.
16.18

Figure 16.12 IMT-2000 radio interfaces
16.19

16
16-
-2
2 SATELLITE NETWORKS
SATELLITE NETWORKS
A
A satellite
satellite network
network is
is a
a combination
combination of
of nodes,
nodes, some
some of
of
A
A satellite
satellite network
network is
is a
a combination
combination of
of nodes,
nodes, some
some of
of
which
which are
are satellites,
satellites, that
that provides
provides communication
communication from
from
one
one point
point on
on the
the Earth
Earth to
to another
another.
. A
A node
node in
in the
the
one
one point
point on
on the
the Earth
Earth to
to another
another.
. A
A node
node in
in the
the
network
network can
can be
be a
a satellite,
satellite, an
an Earth
Earth station,
station, or
or an
an end
end-
-
user
user terminal
terminal or
or telephone
telephone.
.
user
user terminal
terminal or
or telephone
telephone.
.
Orbits
Footprint
Th C i f S lli
Three Categories of Satellites
GEO Satellites
MEO Satellites
16.20
MEO Satellites
LEO Satellites

Figure 16.13 Satellite orbits
16.21

Example 16.1
What is the period of the Moon, according to Kepler’s
law?
Here C is a constant approximately equal to 1/100. The
period is in seconds and the distance in kilometers
period is in seconds and the distance in kilometers.
16.22

Example 16.1 (continued)
Solution
The Moon is located approximately 384,000 km above the
Earth. The radius of the Earth is 6378 km. Applying the
formula, we get.
16.23

Example 16.2
According to Kepler’s law, what is the period of a satellite
that is located at an orbit approximately 35,786 km above
the Earth?
Solution
Solution
Applying the formula, we get
16.24

Example 16.2 (continued)
This means that a satellite located at 35,786 km has a
period of 24 h, which is the same as the rotation period of
the Earth. A satellite like this is said to be stationary to the
h h bi ill i ll d
Earth. The orbit, as we will see, is called a
geosynchronous orbit.
16.25

Figure 16.14 Satellite categories
16.26

Figure 16.15 Satellite orbit altitudes
16.27

Table 16.1 Satellite frequency bands
16.28

Figure 16.16 Satellites in geostationary orbit
16.29

Figure 16.17 Orbits for global positioning system (GPS) satellites
16.30

Figure 16.18 Trilateration
16.31

Figure 16.19 LEO satellite system
16.32

Figure 16.20 Iridium constellation
16.33

Note
The Iridium system has 66 satellites in
i LEO bit h t
six LEO orbits, each at an
altitude of 750 km.
16.34

Note
Iridium is designed to provide direct
worldwide voice and data
communication using
handheld terminals a service similar to
handheld terminals, a service similar to
cellular telephony but on a global scale.
16.35

N t
Teledesic has 288 satellites in 12 LEO
Note
Teledesic has 288 satellites in 12 LEO
orbits, each at an altitude of 1350 km.
16.37

Mobile IP Management in Cellular
Network

2
Motivation: the changing wireless environment
• Explosion in wireless services
– Some connectivity everywhere
– Overlapping, heterogeneous networks
• Small, portable devices
• A choice of network connectivity on one
device
– Sometimes built-in
– Sometimes a portable “bridge” between choices

3
Opportunity for connectivity
• New environment gives us opportunity
– Continuous connectivity for a mobile host
– Seamless movement between networks
• Examples
– Move from office to elsewhere in building
– Move outside building, across campus, to cafe
• Why maintain connectivity?
– Avoid restarting applications/networks
– Avoid losing “distributed state”

4
Different approaches
• The traditional approach: support in the network
– Intelligence (and expense) is in the network
– End-points are cheap (handsets)
– Allows for supporting infrastructure
– Requires agreements/trust amongst multiple vendors
– Examples:
• A link/physical level (many wireless networks)
• At routing level (Columbia, VIP)
– Doesn’t work when switching between technologies and
often not between vendors
– In Internet would require modifying lots of routers

5
Different approaches, continued
• The Internet approach: end-to-end
– Intelligence (and expense) is in the end-points
– Network is cheap (relatively) and as fast as possible
– Implies self-support for many activities
– Less work/trust required amongst multiple vendors
• End-to-end support at transport/naming/application
levels
– May be ideal in future, but requires extensive changes
– Not currently backwards compatible
– TRIAD may be interesting approach

6
Different approaches, continued
• Use end-to-end support at routing level
– Makes problem transparent at layers above and below
– Current Internet standard: Mobile IP (RFC 2002)
application
transport
routing
link
physical
Modify all applications?
Modify TCP, UDP, etc.?
Modify IP end-points?
Modify all device drivers?
How dies this work across
network technologies?
TCP/IP network stack:

7
IP address problem
• Internet hosts/interfaces are identified by IP address
– Domain name service translates host name to IP address
– IP address identifies host/interface and locates its network
– Mixes naming and location
• Moving to another network requires different
network address
– But this would change the host’s identity
– How can we still reach that host?

8
Routing for mobile hosts
CH
MH
Home network
MH
CH
MH = mobile host CH = correspondent host
Home network Foreign network
Foreign network
How to direct packets to moving hosts transparently?

9
Domains versus interfaces
• Switching domains & switching interfaces are the
same problem at the routing level
Network interfaces: Administrative domains:
Mobile
host
ether
radio
171.64.14.X
42.13.0.X
Karunya.edu
Iitm.edu
171.64.X.X
128.32.X.X

10
Mobile IP (RFC 2002)
• Leaves Internet routing fabric unchanged
• Does not assume “base stations” exist everywhere
• Simple
• Correspondent hosts don’t need to know about mobility
• Works both for changing domains and network
interfaces

11
Basic Mobile IP – to mobile hosts
MH = mobile host
CH = correspondent host
HA = home agent
FA = foreign agent
(We’ll see later that FA
is not necessary or even
desirable)
•MH registers new “care-of address” (FA) with HA
•HA tunnels packets to FA
•FA decapsulates packets and delivers them to MH
HA
CH
FA MH

12
Packet addressing
Source address = address of CH
Destination address = home IP address of MH
Payload
Source address = address of HA
Destination address = care-of address of MH
Source address = address of CH
Destination address = home IP address of MH
Original payload
Packet from CH to MH
Home agent intercepts above packet and tunnels it

13
When mobile host moves again
HA
CH
Home network Foreign network #1
FA #1 MH
Foreign network #2
FA #2 MH
•MH registers new address (FA #2) with HA & FA #1
•HA tunnels packets to FA #2, which delivers them to MH
•Packets in flight can be forwarded from FA #1 to FA #2

14
Basic Mobile IP - from mobile hosts
HA
CH
FA MH
Mobile hosts also send packets
•Mobile host uses its home IP address as source address
-Lower latency
-Still transparent to correspondent host
-No obvious need to encapsulate packet to CH
•This is called a “triangle route”

15
Problems with Foreign Agents
• Assumption of support from foreign networks
– A foreign agent exists in all networks you visit?
– The foreign agent is robust and up and running?
– The foreign agent is trustworthy?
• Correctness in security-conscious networks
– We’ll see that “triangle route” has problems
– MH under its own control can eliminate this problem
• Other undesirable features
– Some performance improvements are harder with FAs
• We want end-to-end solution that allows flexibility

16
Solution
HA
CH
MH
•Mobile host is responsible for itself
-(With help from infrastructure in its home network)
-Mobile host decapsulates packets
-Mobile host sends its own packets
-“Co-located” FA on MH
MH must acquire its own IP address in foreign network
This address is its new “care-of” address
Mobile IP spec allows for this option

17
Obtaining a foreign IP address
• Can we expect to obtain an IP address?
– DHCP becoming more common
– Dynamic IP address binding like some dial-up services
– Your friend can reserve an IP address for you
– Various other tricks
– More support for dynamic IP address binding in IPv6
• This assumes less than getting others to run a FA

18
Design implications
• New issues: the mobile host now has two roles:
– Home role
– Local role
- More complex mobile host
- Loss of in-flight packets? (This can happen anyway.)
+ Can visit networks without a foreign agent
+ Can join local multicast groups, etc.
+ More control over packet routing = more flexibility

19
Problems with ingress filtering
HA
CH
MH
•Mobile host uses its home IP address as source address
•Security-conscious boundary routers will drop this packet

20
Solution: bi-directional tunnel
HA
CH
MH
•Provide choice of “safe” route through home agent both ways
•This is the slowest but most conservative option
At the other extreme…

21
Problem: performance
• Example: short-lived communication
– When accessing a web server, why pay for mobility?
– Do without location-transparency
– Unlikely to move during transfer; can reload page
– Works when CH keeps no state about MH

22
Solution: yet more flexibility
HA
CH
MH
•Use current care-of address and send packet directly
-This is regular IP!
•More generally:
-MH should have flexibility to adapt to circumstances
-A range of options: from slow-but-safe to regular IP
-Should be an end-to-end packet delivery decision (no FA)

23
Routing options
• Allow MH to choose from among all routing options
• Options:
– Encapsulate packet or not?
– Use home address or care-of address as source address?
– Tunnel packet through home agent or send directly?
• Choice determined by:
– Performance
– Desire for transparent mobility
– Mobile-awareness of correspondent host
– Security concerns of networks traversed
• Equivalent choices for CH sending packets to MH

24
Mobile IP issues on local network
• Host visiting local network with foreign agent
– No real presence on local network
• Host visiting local network with its own IP address
– Has a role on local network
– Reverse name lookups through special name?
– Or do you change the DNS entry?
– Its IP address / HW address gets into local hosts’ ARP
caches
– Which IP address should go into cache?
– How do you update caches if host moves again?

25
Local ARP cache problem
• ARP caches store (IP address, HW address) pairs
• MH host visits foreign network
• Wants to talk directly back and forth to local hosts
– If it wants to maintain connectivity with them after moving
• Use home IP address
• Other hosts address MH by HW address on local link
• But if MH moves again, ARP cache entries are wrong
– If it doesn’t care
• Use local IP address
• If MH moves, ARP cache is wrong, but nobody cares

26
Multiple Network Interfaces – Why?
• Want to probe hosts through all active interfaces
– Example: register with HA through new interface before
switching to it
– Helps with smooth handoff between types of networks
• Want transparent mobility for more than one interface
• Example:
– One application users cheap/slow interface while another
uses expensive/fast interface
– Move to new network(s) or lose contact with one network
– Don’t want to restart either application

27
Why is this hard?
• System support missing in at least two areas
• Need “next hop” info for more than one interface
– Need to be able to send packets beyond local subnet for
more than one interface
– Current support only uses gateway info for one interface
• Mobile IP doesn’t separate traffic flows to different
interfaces
– (This isn’t the Mobile IP “simultaneous binding” feature)
– Current HA won’t keep different bindings for more than
one interface per host based on traffic flow

28
Solution for next hop
• Backwards-compatible extension to routing table
– Add “next-hop” info for more than one interface
– Take advantage of “metric” field for priority of interface
– This maintains backwards compatible default route
Destination Gateway Netmask Flags Metric Iface
a.b.0.0 0.0.0.0 255.255.0.0 U 0 eth0
c.d.0.0 0.0.0.0 255.255.0.0 U 0 st0
127.0.0.0 0.0.0.0 255.0.0.0 U 0 lo
0.0.0.0 a.b.0.1 0.0.0.0 UG 1 eth0
0.0.0.0 c.d.0.1 0.0.0.0 UG 100 st0

29
Solution for Mobile IP
• Extend home agent
• Mobile host registers flow-to-interface bindings
Home
Agent
Mobile
Host
Correspondent
Host
flow 1
flow 2
flow 1
+
flow 2
CoA1
CoA2

30
Flexible connectivity management
• Need to manage this extra flexibility through adaptivity
– Monitor availability of various interfaces
– System detects & configures interfaces automatically
– Applications can express interest in types of service
– System (or application) can choose best interface
– System feedback necessary: system notifies application of
changes as conditions warrant

31
Connectivity management, continued
• Must address protocol interaction when connecting
– Is DHCP available?
– Is this a frequently visited network? (probe for gateways)
• If so, can use pre-determined address
– Must the host use a foreign agent here?
• If it’s broken, how do we find what’s wrong & fix it?
– Cable loose?
– Battery in radio dead?
– Home agent dead?
• Strong need for “no-futz” computing on mobile hosts

Long Term Evolution (LTE)
Technology

IMT-2000 Submission Plan [of
Mar 2016]
Pg 3 |

Introduction
• Spectrum is a finite and scarce but non-
exhaustible natural resource which is a vital
input for wireless services
• Rapid development of wireless technology
has ensured that there is an increasing
range of valuable uses of the spectrum
• With competing users, uses and growth of
wireless services, the demand for spectrum
has tremendously increased.
4

Introduction
• The trend of modern communications is
towards mobility, with increasingly higher
data rates/ speeds, for which wireless is the
only option
• The requirements of captive applications
are also growing.
• All these have resulted in greater demands/
pressure on the already scarce RF spectrum
resource
5

Introduction
• Shortage of spectrum will be setback to
innovations, competition, businesses and
consumers.
• Making spectrum available at a time when
convergence is causing rapid and unpredictable
change poses a severe challenge.
• Advances in technology create the potential for
systems to use spectrum more efficiently and to
be much more tolerant of interference than in
the past.
The Second meeting of SATRC Working Group on Spectrum
12-13 December 2011 Colombo, Sri Lanka 6

Introduction
• With the availability of higher data speeds, the user
requirements are also continually increasing wrt:
– different services and applications,
– expecting a dynamic, continuing stream of new
capabilities that are ubiquitous and available across a
range of devices using a single subscription and a single
identity.
• Requirement for new radio access technologies to
satisfy the anticipated demands for higher
bandwidth services is increasing.
• IMT and IMT-Advanced technologies are the answers
to these requirements
7

IMT and IMT-Advanced Technologies
• LTE, LTE Advanced and Wireless MAN-
Advanced, are designed to enable high speed
Internet/Broadband at anytime, anywhere.
• These systems facilitate higher bandwidth, higher
data rate and support higher level of user-level
customization.
• As per ITU for IMT-Advanced technologies, the
targeted peak data rates are up to 100 Mbit/s for
high mobility and up to 1 Gbit/s for low mobility
scenario. Scalable bandwidths up to at least
40 MHz should be provided
8

IMT-Advanced Technologies-Key Features
• High degree of commonality of functionality
worldwide while retaining the flexibility to support
a wide range of services and applications in a cost
efficient manner;
• compatibility of services within IMT and with
fixed networks;
• capability of interworking with other radio access
systems;
• high quality mobile services;
• User equipment suitable for worldwide use;
• User-friendly applications, services and equipment;
• Worldwide roaming capability; 9

LTE and LTE-Advanced Technologies
10

LTE and LTE-Advanced Technologies
• LTE and Wimax technologies are available since
2009/2006.
• Current versions are called ‘LTE-Advanced’ and
WirelessMAN Advanced respectively.
• Qualifies IMT-advanced technologies make use of same
key technologies:
– Orthogonal Frequency Division Multiplex (OFDMA)
– Multiple Input Multiple Output (MIMO) and
– System Architecture Evolution (SAE)
11

Multiple Input Multiple Output (MIMO)
• Uses multiple transmitter and receiver antennas, which
allow independent channels to be created in space.
• Various Approaches for MIMO:
– Space diversity:- to improve the communication reliability
by decreasing the sensitivity to fading by picking up
multiple copies of the same signal at different locations in
space.
– Beamforming:- antenna elements are used to adjust the
strength of the transmitted and received signals, based on
their direction for focusing of energy.
– Spatial Multiplexing:- Increased capacity, reliability,
coverage, reduction in power requirement by introducing
additional spatial channels that are exploited by using space-
time coding
12

Orthogonal Frequency Division Multiple Access (OFDMA)
• Based on the idea of dividing a given high-bit-rate data stream
into several parallel lower bit-rate streams and modulating each
stream on separate carrier – often called sub-carriers or tones.
• Multi-carrier modulation scheme minimize inter-symbol
interference (ISI) by making the symbol time large enough so that
the channel-induced delays are an insignificant (<10%) fraction
of the symbol duration.
• OFDM is a spectrally efficient version of multi-carrier
modulation where the sub-carriers are selected such that they are
all orthogonal to one another over the symbol duration, thereby
avoiding the need to have non overlapping sub-carrier channels to
eliminate inter-carrier interference .
• Guard intervals are used between OFDM symbols. By making
the guard intervals larger than the expected multi-path delay
spread, ISI can be completely eliminated 13

Long Term Evolution(LTE): Speed
• Capabilities:-
– Scalable bandwidth up to 20 MHz, covering 1.4, 3, 5, 10,
15, and 20 MHz
– Up/Downlink peak data rates up to 86.4/326 Mbps with 20
MHz bandwidth
– Operation in both TDD and FDD modes
– Reduced latency, up to 10 ms round-trip times between
user equipment and the base station, and upto less than
100 ms transition times from inactive to active
14

Long Term Evolution(LTE): Specifications and Speed
15
Parameter Details
Peak downlink speed with 64QAM in Mbps 100 (SISO), 172 (2x2 MIMO), 326 (4x4 MIMO)
Peak uplink speeds(Mbps) 50 (QPSK), 57 (16QAM), 86 (64QAM)
Data type
All packet switched data (voice and data). No
circuit switched.
Channel bandwidth (MHz) 1.4, 3, 5, 10, 15, 20
Duplex schemes FDD and TDD
Mobility
0 - 15 km/h (optimised),
15 - 120 km/h (high performance)
Latency
Idle to active less than 100ms
Small packets ~10 ms
Spectral efficiency
Downlink: 3 - 4 times Rel 6 HSDPA
Uplink: 2 -3 x Rel 6 HSUPA
Access schemes
OFDMA (Downlink)
SC-FDMA (Uplink)
Modulation types supported
QPSK, 16QAM, 64QAM (Uplink and
downlink)
LTE specification

Long Term Evolution(LTE)-Advanced: Key Features
• Features:-
– Compatibility of services
– Enhanced peak data rates to support advanced services and
applications (100 Mbit/s for high and 1 Gbit/s for low
mobility).
– Spectrum efficiency: 3 times greater than LTE.
– Peak spectrum efficiency: downlink – 30 bps/Hz; uplink –
6.75 bps/Hz.
– Spectrum use: the ability to support scalable bandwidth use
and spectrum aggregation where non-contiguous spectrum
needs to be used.
16

Technologies(2G, IMT, IMT-Advanced) in SATRC countries
17
• Based on the data available, the bands being
operated in SATRC Countries are:
• 450, 700, 800, 900, 1800, 1900 MHz;
2.1, 2.3, 2.5, 3.3-3.6GHz for various mobile
services i.e. 2G,3G,BWA services, with
various block sizes offered to the mobile
operators.
• Spectrum Allocation methodologies varies
from Command& Control to auction.

18
Spectrum Bands Identified for various wireless
telecom services (INDIA)
Band Technology
450MHz 2G & 3G
700 MHz Digital Mobile TV
800 MHz 2G & 3G
900MHz 2G
1800MHz 2G
1900MHz 2G & 3G
2010-2025 MHz BWA
2.1 GHz 3G
2.3 GHz BWA
2.5 GHz BWA
3.3 GHz BWA
3.4GHz BWA
2.4-2.4835, 5.15-5.35 & 5.725-5.875 GHz are unlicensed spectrum bands

Challenges posed by technologies like LTE in
spectrum management
19
• Identification of common spectrum bands
– Common to SATRC Countries for Ubiquitous roaming
– identify the availability of large chunk of spectrum in the
identified bands
• Spectrum management planning, allocation, allotment
and regulations of frequency bands
– to determine the use or uses that would best serve the public and government
interest
– to tackle the transmissions interference unless the user frequencies are
sufficiently separated in terms of frequency, geography or time
– co-ordination with neighbouring countries, to mitigate the extent of harmful
interference
– need to strike a balance between reducing the extent of harmful interference,
through careful planning, and enabling new and potentially valuable new
services to enter the market

spectrum management
20
• Frequency assignment and licensing
– Traditional methods poses many challenges in
terms of time, technological progress and the
delivery of services, thus causing inefficient
utilization of this precious resource.
– to assign spectrum to those who value it the most
and are able to utilize rationally and efficiently

spectrum management
21
• Responsive to change
– to devise procedures to ration current and future
demand for radio spectrum between competing
commercial and public service users
– it would require a detailed knowledge of supply
and demand trends, technology developments, and
the relative value to society of alternative services
– accumulation and assimilation of sufficient
information to make a correct assignment of
spectrum to optimise use over time

22
Wireless Mesh Networks
with LTE

23
Wireless routers
Gateways
Printers, servers
Mobile clients
Stationary clients
Intra-mesh wireless links
Stationary client access
Mobile client access
Internet access links
Node Types Link Types
Overview

24
Gateways
• Multiple interfaces (wired &
wireless)
• Mobility
– Stationary (e.g. rooftop) – most
common case
– Mobile (e.g., airplane,
busses/subway)
• Serve as (multi-hop) “access
points” to user nodes
• Relatively few are needed,
(can be expensive)
GW

25
Wireless Routers
 At least one wireless interface.
 Mobility
 Stationary (e.g. rooftop)
 Mobile (e.g., airplane,
busses/subway).
 Provide coverage (acts as a mini-
cell-tower).
 Do not originate/terminate data
flows
 Many needed for wide areas,
hence, cost can be an issue.

26
Users
• Typically one interface.
• Mobility
– Stationary
– Mobile
• Connected to the mesh
network through wireless
routers (or directly to
gateways)
• The only
sources/destinations for
data traffic flows in the
network.

27
User – Wireless Router Links
• Wired
– Bus (PCI, PCMCIA, USB)
– Ethernet, Firewire, etc.
• Wireless
– 802.11x
– Bluetooth
– Proprietary
• Point-to-Point or Point-to-
Multipoint
• If properly designed is not a
bottleneck.
• If different from router-to-
router links we’ll call them
access links

28
Router to Router Links
• Wireless
– 802.11x
– Proprietary
• Usually multipoint to
multipoint
– Sometimes a collection of
point to point
• Often the bottleneck
• If different from router-to-
user links we’ll call them
backbone links

29
Gateway to Internet Links
• Wired
– Ethernet, TV Cable, Power
Lines
• Wireless
– 802.16
– Proprietary
• Point to Point or Point-to-
Multipoint
• We’ll call them backhaul
links
• If properly designed, not
the bottleneck

30
How it Works
• User-Internet Data Flows
– In most applications the main
data flows
• User-User Data Flows
– In most applications a small
percentage of data flows

31
Taxonomy
Wireless
Networking
Multi-hop
Infrastructure-less
(ad-hoc)
Infrastructure-based
(Hybrid)
Infrastructure-less
(MANET)
Single
Hop
Cellular
Networks Wireless Sensor
Networks
Wireless Mesh
Networks
Car-to-car
Networks
(VANETs)
Infrastructure-based
(hub&spoke)
802.11 802.16 Bluetooth
802.11

32
Mesh vs. Ad-Hoc Networks
• Multihop
• Nodes are wireless,
possibly mobile
• May rely on
infrastructure
• Most traffic is user-to-
user
Ad-Hoc Networks Wireless Mesh Networks
 Multihop
 Nodes are wireless,
some mobile, some
fixed
 It relies on
infrastructure
 Most traffic is user-to-
gateway

33
Mesh vs. Sensor Networks
 Bandwidth is limited (tens of kbps)
 In most applications, fixed nodes
 Energy efficiency is an issue
 Resource constrained
 Most traffic is user-to-gateway
Wireless Sensor Networks Wireless Mesh Networks
 Bandwidth is generous (>1Mbps)
 Some nodes mobile, some fixed
 Normally not energy limited
 Resources are not an issue
 Most traffic is user-to-gateway

36
Extend WLAN Coverage
Source: www.belair.com
Source: www.meshdynamics.com

37
Mobile Internet Access
Law enforcement
Intelligent transportation
• Direct competition
with G2.5 and G3
cellular systems.
Source: www.meshnetworks.com
(now www.motorola.com).

38
Emergency Response

39
Layer 2 Connectivity
• The entire wireless mesh
cloud becomes one (giant)
Ethernet switch
• Simple, fast installation
– Short-term events (e.g.,
conferences, conventions,
shows)
– Where wires are not desired
(e.g., hotels, airports)
– Where wires are impossible
(e.g., historic buildings)
Internet

40
Military Communications

41
Community Networks
Source: research.microsoft.com/mesh/
 Grass-roots broadband
Internet Access
 Several neighbors may
share their broadband
connections with many
other neighbors
 Not run by ISPs
 Possibly in the
disadvantage of the ISPs

42
Many Other Applications
• Remote monitoring
and control
• Public
transportation
Internet access
• Multimedia home
networking

43
Broadband Internet Access
Cable
DSL
WMAN
(802.16)
Cellular
(2.5-3G)
WMN
Bandwidth Very
Good
Very
Good
Limited Good
Upfront
Investments
Very
High
High High Low
Total
Investments
Very
High
High High Moderate
Market Coverage Good Good Good
Modest

44
WLAN Coverage
Source:
www.meshdynamics.com
802.11 WMN
Wiring
Costs
Low
High
Number of APs As needed Twice as many
Cost of APs High
Low
Bandwidth Good
Very
Good

45
Mobile Internet Access
Cellular
2.5 – 3G WMN
Upfront
Investments
Low
High
Geolocation Limited Good
Bandwidth Good
Limited
Upgrade
Cost
Low
High

46
Emergency Response
Cellular
2.5 – 3G WMN
Walkie
Talkie
Availability Reasonable Good Good
Bandwidth Good
Limited Poor
Geolocation Poor Limited
Poor

47
Layer 2 Connectivity
Ethernet WMN
Total Cost Low Moderate
Mobile Users 802.11 needed Good
Bandwidth Good
Very
Good
Speed/Ease of
Deployment
Fast/Easy
Slow/Difficult

48
Military Communications
WMNs
Existing
System(s)
Coverage
Very
Good Good
Good
Poor
Bandwidth
Voice Support Good
Very
Good
Covertness Poor Better
Power efficiency Good
Reasonable

CHARACTERIZATION OF
WIRELESS CHANNELS

Characterization of Wireless Channels
• Path loss models: Free Space and Two-Ray models
• Link Budget design
• Parameters of mobile multipath channels
• Time dispersion parameters
• Coherence bandwidth
• Doppler spread & Coherence time
• Small Scale fading
• Fading effects due to multipath time delay spread
• Fading effects due to doppler spread

Introduction
• Wireless communication – broadcasting and reception of
signals by an appropriate receiver through wireless
medium (air)

Characteristics of wireless channels
• Path loss
• Fading
• Interference
• Doppler shift

Path Loss
• Ratio of power of the transmitted signal to the power of
same signal received by reciever.
• Dependent on radio frequency used and nature of terrain
• Path loss models – Free space & Two ray
• Free space – no attenuation of signals, only direct path
• Two ray – direct path & Reflected path

Fading
• Fluctuations in signal strength when received at the
receiver.
• Types – (1) Fast/small scale fading (2) slow/large scale
fading.
• Fast fading – rapid fluctuations in amplitude, phase or
multipath delays.
• Slow fading – objects partially absorb the transmissions
• Counter measure – Diversity & Adaptive modulation

Interference
• Types : (1) ACI (2) CCI (3) ISI
Interference Counter measure
ACI Guard band
CCI Usage of directional
antennas, dynamic channel
allocation
ISI Adaptive equalization

Doppler shift
• Change in frequency when transmitter and receiver are
mobile in nature.
• Higher frequency – when both move towards
• Lower frequency – when both move away

20CS2007 Computer Communication Networks

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