Transcript Chapter 15. Recent advances

Chapter 15
Recent Advances
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
1
Outline
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Ultra-Wideband Technology.
Multimedia Services Requirements.
Mobility Management for Integrated Systems.
Multicast in Wireless Networks.
MANET Route Maintenance/Repair.
Design Issues in Sensor Networks.
Bluetooth Networks
Low Power Design
XML
Threats and Security Issues
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
2
Ultra-Wideband Technology (UWB)
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UWB Radio : Radio System having large bandwidth.
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Bandwidth > 25% of center frequency or > 1 GHz.
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Wide bandwidth makes it possible to share spectrum
with other users with certain co-coverage sense.
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Wide band signals are natural for location
determination applications.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
3
UWB Basics –
Time Modulated (TM-UWB)
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Basic element: Ultra short monocycle wavelet.
 Wavelet pulse width between 0.2 and 1.5 nsecs.
 Center frequency between 5 GHz and 600 MHz.
 Pulse-to-pulse interval between 25 and 1000 nsecs.
System uses pulse position modulation.
No Intermediate frequency stage.
 Reduces complexity.
Single bit of information is spread over multiple
monocycels.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
4
TM-UWB Modulation and DSC-UWB
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Pulse position modulation
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Positions signal one quarter cycle early or late relative
to the nominal PN coded location or pulse polarity.
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Modulation further smoothes the spectrum of the
signal, thus making the system less detectable.
Direct Sequence phase Coded (DSC)-UWB
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Wavelet pulse trains at duty cycles approaching that of
a sine wave carrier are direct sequence modulated to
spread the signal. A PN sequence provides spectrum
spreading, channelization and modulation.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
5
UWB Signal Propagation
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Generally follow a free space propagation law.
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Millions of coded pulses transmitted per second.
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Emissions below conventional receiver noise floor and
across an ultra wide bandwidth.
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Very low extant RF signature, providing intrinsically
secure transmissions.
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Low probability of detection and interception.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
6
UWB Capabilities
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Communications:
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Noise like spectral characteristics of UWB signals
enables secure communication with less detection.
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Suitable for robust in-building communications.
Advanced Radar Sensing:
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Through the wall radar, terrain mapping radar,
ground penetrating radar.
Precision Location and Tracking:
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Remote, secure and real time tracking system.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
7
UWB Applications
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High Performance Wireless Home Network
 To support a bit rate of at least 50 Mbps.
 Simultaneous data transmission from multiple digital
devices, high speed and affordable connectivity between
devices and full motion video.
An UWB Communication link for Unmanned Vehicle
applications
 UWBs low cost, all-digital design, small size , light
weight , LPI/D (probability of interception or
detection) and AJ (anti-jam) makes it ideal for
unmanned vehicle applications.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
8
UWB Advantages - Limitations
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UWB radio systems have large bandwidth (> 1 GHz).
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UWB has potential to address today’s “spectrum drought”.
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Emissions below conventional level.
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Single technology with 3 distinct capabilities.
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Secure transmission, low probability of interception or
detection and anti-jam immunity.
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Not appropriate for a WAN (Wide Area Network)
deployment such as wireless broadband access.
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UWB devices are power limited
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
9
Multimedia Service Requirements
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Two trends distinguish multimedia requirements with
respect to telecommunications – increasing demand for
bandwidth, and a transparent support for user mobility.
On today’s internet, 90% of the traffic uses TCP, while
80% of the networking is done over the IP network.
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Hence, multimedia streaming over IP has become a
major issue.
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The QoS of a network is defined by various parameters
such as bandwidth, latency, jitter, packet loss and packet
delay.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
10
Multimedia Service Requirements
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ETSI (European Telecommunications Standardization
Institute) has introduced four classes of services with
class 1 being best efforts service and class 4 being QoS
guaranteed service.
Some standards need to be defined in the following
areas to form complete streaming systems – media
codecs, transport protocols, media control, file formats,
and capability exchange.
Media codecs are comprised of MPEG-1, MPEG-2,
and MPEG-4.
MPEG-1 and MPEG-2 are limited to audio/video
compression.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
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Multimedia Service Requirements
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MPEG-4 on the other hand describes the coded
representation of natural and synthetic multimedia objects.
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The objects may include images, video, audio, text,
graphics, and animation.
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MPEG-4 audio capabilities include tools for speech,
audio, voice synthesis, composition and scalability.
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Two file formats are found in MPEG-4. One is based on
the Apple quick time format and the other is based on the
Microsoft ASF (Advanced Stream Format).
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
12
Multimedia Service Requirements
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HTTP (Hyper Text Transfer Protocol) is a very simple
and widely used way to stream media files.
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Works with regular web servers and does not require a
special media server.
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In MPEG-4 systems, the transport streams is divided into
4 layers – compression layer, synchronization layer,
flexmux layer and transport layer.
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A media control protocol needs to support issues of file
seek, bandwidth scalability and live streaming.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
13
Some Multimedia Protocols
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The Real-time streaming protocol (RTSP) establishes and
controls time synchronized streams of continuous media
such as audio and video.
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The Session initiating protocol (SIP) is an applicationlayer control protocol for creating, modifying and
terminating sessions with one or more users.
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IP broad-band networks have also caught the attention of
researchers in recent times.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
14
Mobility Management
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The next generation of wireless mobile networks have
been designed to support both real-time and non real-time
service.
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Mobility management has to be taken into consideration
while designing the infrastructure.
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Mobility management features two tasks - location
management and handoff management.
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Efficient handoff design schemes are essential in ensuring
good QoS in integrated wireless networks.
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Criteria for handoff initiation need to be selected
carefully.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
15
Mobility Management
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Some handoff criteria currently in use are word error
indicator, received signal strength and quality indicator.
Handoff strategy for integrated wireless networks has to
be different for different services. As an example,
handoff interruptions in real-time services are very
undesirable.
On the other hand, interruptions are not so critical in non
real-time applications.
In order to provide better QoS with limited frequency
spectrum reuse, various handoff schemes have been
proposed.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
16
Mobility Management
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Some guard channels in each BS are reserved for handoff
request calls. Such a request will have a higher priority
over an originating call.
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The guard channels are subject to availability.
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In a queuing based priority handoff scheme, each BS has
one or more queuing buffers for all incoming calls. A call
is serviced immediately if there is an available channel.
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Otherwise, the call is stored in a queue and is not
dropped/blocked.
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When a channel is released, the first call in the queue is
picked.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
17
Mobility Management
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The queue operates on a first-in-first-out basis.
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Current issues of interest are: How many queues should be
allocated to a BS, and what kind of service call should be
included into the queue?
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One way of giving priority reservation to real-time service
handoff requests is to reserve a number of channels for realtime service handoff requests.
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Queues are allowed for real-time service handoff requests
and non-real-time service handoff requests.
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A non-real-time request can be transferred to another queue
when the MS moves out of the cell.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
18
Mobility Management
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A service dependent priority handoff scheme for integrated
wireless networks has been proposed in [27, 28].
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Calls are divided into four different service types:
originating real-time service calls, originating non-realtime service calls, non real-time service handoff request
calls and real-time service handoff request calls.
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Correspondingly, the channels in each cell are divided into
three groups, one each for real-time service calls, non realtime service calls and overflowed handoff requests from
the previous two groups.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
19
Mobility Management
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Some channels are reserved exclusively for real-time
service handoff requests.
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Hence, real-time service handoff requests have priority
over non-real-time service handoff requests and all
handoff requests have priority over originating calls.
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Current issues of interest include the introduction of a
preemptive priority procedure that gives real-time service
handoff requests a higher priority over non real-time
service handoff requests.
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Individual queues will be added for both real-time and
non real-time requests.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
20
Mobility Management
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The non real-time service handoff requests waiting in
the queue can be transferred from the current base
station to one of the target base stations when the
mobile user moves out of the current cell before it gets
service.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
21
Multicast in Wireless Networks
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Range Based MoM (RBMoM)
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An enhancement of MoM.
RBMoM provides a trade off between the shortest delivery path
and the frequency of the multicast tree reconfiguration.
It selects a router called multicast home agent (MHA), which is
responsible for tunneling multicast packets to FA to which the
MH is currently subscribed within its service range.
If a mobile host is out of service range, then an MHA handoff
will occur.
Every MH can have only one MHA, which changes dynamically
as per the location of the MH, whereas the HA of an MH never
changes.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
22
Multicast in Wireless Networks
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Multicast for Mobility Protocol (MMP):
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It combines Mobile IP and CBT where the former
controls communication up to the foreign network, and
the latter manages movement of hosts inside them.
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It assumes the foreign domain to form a hierarchy of
multicast supporting routers.
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Similar to the concept of FA, base stations acting as a
multicast router transmit periodic beacons, which include
one multicast care-of address.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
23
Multicast in Wireless Networks
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Multicast for Mobility Protocol (MMP) (cont’d):
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Upon acquiring a care-of address, the MH sends a
registration message to the base station, which
triggers a multicast tree join and transmits a CBT
join request to the core.
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The core takes care of relaying the registration
request to the HA of the MH by replacing the CoA
to its own address, thus hiding the multicast part of
the protocol and acting as a sole foreign agent.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
24
Multicast in Wireless Networks
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Reliable Multicast Data Distribution Protocol (RMDP):
 Uses Forward Error Correction (FEC) and Automatic
Retransmission reQuest (ARQ) information to provide
reliable transfer. Redundant information is inserted into
the FEC, often enabling a receiver to reconstruct the
original packet.
 In the event that such information is not enough, an
ARQ is sent to the multicast source which in turn,
multicasts the requested packet to all receivers.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
25
Multicast in Wireless Networks

Reliable Multicast Data Distribution Protocol (RMDP)
(cont’d):
 In RMDP, a data object to be transmitted is a file,
identified by a unique name, say its Uniform Resource
Locator (URL).
 The file has a finite size, and is split into packets of s
bytes each. RMDP uses an (n, k) encoder with n >> k
to generate packets for transmission, and assumes the
existence of a multicast network which provides
unreliable, but efficient delivery of data packets.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
26
Multicast in Wireless Networks
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Reliable Multicast Data Distribution Protocol (RMDP)
(cont’d):
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Limitations:
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In RMDP, data encoding/decoding is done through
software resulting in a processing overhead and,
therefore, performance degradation.

In case of burst errors, a lot of ARQ packets are
generated. This triggers a substantial amount of
retransmission packets, which are multicast to all
receivers.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
27
Multicast in Wireless Networks
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Reliable Mobile Multicast Protocol (RM2):
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RM2 is a hierarchical protocol, which divides a
multicast tree into sub-trees where subcasting within
these smaller regions is applied using a tree of
retransmission servers (RSs).

RS have a retransmission subcast address shared by its
members and which may be dynamically configured
using IETF’s MADCAP (Multicast Address Dynamic
Client Allocation Protocol).
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
28
Multicast in Wireless Networks

Reliable Mobile Multicast Protocol (RM2) (cont..):
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In order to guarantee end-to-end reliability, the
receivers are required to send NACKs, pointing out the
packets to be retransmitted. In other words, RM2
implements selective packet retransmission.

RM2 adopts a retransmission algorithm that
dynamically switches between unicast and multicast
modes to save network and wireless resources.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
29
Multicast in Wireless Networks
A Comparison of IP based Wireless Multicast Routing Protocols
Reliability
Packet
Redundancy
Multicast
Protocol
Dependency
Join & Graft
delays
Yes
No
No
Independent
Yes
No
No
Yes
Independent
No
MoM
No
No
Minimal
Independent
No
MMP
No
No
Minimal
CBT
No
Mobicast
Yes
No
Minimal
Independent
Yes
RMDP
No
Yes
Yes
Independent
Yes
RM2
Yes
Yes
No
Independent
Yes
Mobility
Protocol
Remote
Subscription
Bi-directional
Tunneling
Mobile IP
Optimal
Routing
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
30
Localized Route Repair
Destination node
D
C
A
B
New path
Source node
Original path
Node Movement
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
31
Localized Route Repair

The major task of routing mobile stations in a MANET is
to find a route to the destination MS quickly.

Route maintenance/repair are also major issues in such
networks as they aim at the reduction of the data losses
that may occur otherwise.

Existing protocols such as DSR, and AODV stick with a
fixed route between a source destination pair till it is
expired or broken.

Route maintenance addresses the problem that arises
when a route becomes bad/broken due to host mobility.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
32
Localized Route Repair
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With route optimization, mobile hosts need to collect as
much fresh information as possible with the least cost.
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In the event of a route failure, a local route recovery
process is performed before the problem is reported to
the source. An illustrative example is shown.

Node B moves away from the current route between the
source and the destination. Node A, on finding its
connection to B broken, broadcasts a ROUTE_REQ
packet with a small hop limit.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
33
Localized Route Repair

In the next step, nodes near A send a normal
ROUTE_REPLY packet to rebuild the route. The
initiator of the ROUTE_REQ sets a timer so that it can
send a normal route error packet to sources node if the
broken route is not rebuilt.

Various route repair techniques for MANETs
demonstrate the effect of relative node velocity, node
density, and communication range on the scalability of a
routing protocol.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
34
Sensor Network Design Challenges
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Robustness
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Stability against task dynamics
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Scalability
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Energy efficiency

Providing quality of service for time critical
applications
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
35
Sensor Network Databases
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COUGAR, which was developed at Cornell is a model
for distributed query execution in sensor networks.

Fantastic data LLC (logical Link Control) have
developed a Web database system which adapts to data
criticality requirements and power consumption.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
36
Collaborative Information Processing

Sensor Networks require efficient beam-forming
algorithm to collaborate and aggregate the data that
they gather periodically.

The algorithms and methods employed for
collaborative sensing strongly influence the overall
performance of ad hoc networked sensors
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
37
OS Design for Sensor Networks

TinyOS developed at Berkeley is an ultra-low power
sensor network platform that enables low cost
deployment of the sensor network.

MagnetOS developed at Cornell is a single system
image (SSI) operating system in which the entire ad
hoc network looks like a single Java virtual machine.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
38
Bluetooth Networks

Bluetooth wireless technology enables links between
mobile computers, mobile phones, portable handheld
devices, and connectivity to the internet.

Despite using a frequency hopping scheme, bluetooth
devices experience a drop in throughput due to
interference because of WLAN and WPAN operations.

A mathematical model has been derived for packet
success probability due to interference [46].

The interference in bluetooth networks has been found to
be intermittent in nature.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
39
Bluetooth Interference

According to the IEEE 802.15.2 WG, two classes of
coexistence mechanisms are possible – collaborative and
non-collaborative.

If it is possible for the WLAN and WPAN to exchange
information, then the collaborative mechanism may be
used. Otherwise, the non-collaborative mechanism needs
to be used.

An example of such a non-collaborative mechanism is
IBLUES. It employs dynamic packet segmentation to
mitigate interference effects on Bluetooth devices.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
40
Bluetooth Networks

Bluetooth standard defines different packet types to
adjust to different application requirements.

They range from the single 1-slot packet to the FEC
encoded 5-slot packet.

The onus of choosing the packet is on the application.

The adaptation layer is responsible for receiving
messages from the upper layers and segmenting them into
smaller pieces of data.

The small pieces of data can fit into the Bluetooth
standard packet.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
41
Bluetooth Networks

According to a study, different packets should be
employed according to the interference levels.

The Bluetooth communication substrate consists of a
radio, baseband, link controller, and link manager layers.

Bluetooth specification alludes to the concept of
internetworking multiple piconets called scatternets.

Some major challenges need to be addresses first – a)
topology formation, b) link scheduling, and c) packet
scheduling.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
42
Need for Low Power Design

Limited energy of ad hoc and sensor network nodes.

Not easily replaceable after deployment in forests and
oceans.

Slow progress in battery technology.

Most of the times wireless devices are in a idle state or
doing very trivial work.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
43
Power Conservation Approaches

Turning off hardware if not in use (display screens etc).

Going to sleep during idle periods.

Reducing the voltage supply during periods of low
power operations.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
44
Dynamic Voltage Scaling (DVS)





For a sensor node processor consumes 30-50% of the
battery power.
DVS is conserving processor power without significant
performance degradation.
Pdynamic  CVdd2 f
where, C: capacitance, f: frequency, Vdd: supply voltage.
Therefore, reducing voltage reduces power consumption.
Transmeta TM5400 or the “Crusoe” is the one of the few
processors which supports voltage scaling
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
45
Future Applications

The need for the power conservation will increase for
future video processing applications by wireless
nodes.

Other applications such as image processing and
sound processing will also need more power.

Therefore, conserving power is one of the important
research areas today.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
46
XML

Programming versus Markup Language
- One Process data and other Presents Data

SGML (Standard Generalized Markup Language)

Why XML, Why not Html ?
- HTML instructs Web Browser
- XML (eXtensible Markup Language) is low level
syntax for representing structured data and this
simple syntax could be used to support a wide
variety of applications
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
47
WML (Wireless Markup Language)

XML Application

Designed for low bandwidth and small display
devices

Deck of cards concept

Multiple Screens in single retrieval

Predefined set of elements
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
48
Threats and Security Issues

Larger security challenges present in wireless networks
than in conventional wired networks.

Security is essential due to hackers, intruders, viruses,
and industrial espionage.

Wireless networks are very dissimilar from wired
networks.

Data is broadcast so that it can be received by all nodes
in the vicinity.

Wireless networks operate under low battery powers,
limited bandwidth, and higher costs.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
49
Attacks in Wireless Networks


Hence, it is very difficult to adapt security schemes from
wired networks to wireless networks.
Three types of attacks exist in wireless networks – a)
Active attack, b) Passive attack, and c) Accidental attack.

An active attack occurs when data modification or false
data transmission takes place. Can be divided into four
categories – a) masquerade, b) replay, c) message
modification, and d) denial of service.

The object of a passive attack is to obtain information
transmitted through the network.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
50
Attacks in Wireless Networks

Accidental attacks occur because of exposure due to the
failure of components.

An eavesdropper is able to tap the communication into
the wireless channels by positioning itself within the
transmission range.

Networks are vulnerable to unauthorized access from the
outside world. User authentication is an appropriate way
to secure such networks.

May not be feasible to implement security schemes on
wireless networks with very limited computational
ability.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
51
Current Approaches

IEEE 802.11 defines two authentication schemes : open
system authentication and shared key authentication.

No key management functions defined in 802.11

Secure key generation and distribution required by systems
containing authentication and identification schemes.

Key distribution to the service provider via a backbone
network is being proposed.

A scheme that assumes mutual trust among network nodes
while authenticating route reply messages has been
proposed by Venkatraman and Agrawal in [60].
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
52
Current Approaches

A scheme has also been proposed to identify some
internal attacks specific to the AODV routing
protocol.

Current security mechanisms for wired networks are
not applicable to wireless networks.

Hence, new techniques need to be developed to make
wireless networks more secure and less vulnerable to
attacks.
Copyright © 2003, Dr. Dharma P. Agrawal and Dr. Qing-An Zeng. All rights reserved.
53