Ad-Hoc Networks

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Ad-Hoc Networks

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Title: Ad-Hoc Networks

1
Ad-Hoc Networks
Establishing node-to-node communication with no
infrastructure needed
Authors

Ðorde Trifunovic, djole_at_europemail.com
Nikola Milanovic, nikola99_at_EUnet.yu
Prof. Dr. Veljko Milutinovic, vm_at_etf.bg.ac.yu

2
What will you learn from this tutorial?
This tutorial will guide you through the
following sections

Introduction
Mobile networks
Routing in ad-hoc networks
Security in ad-hoc networks
Bluetooth
The IEEE/UB ad-hoc multihop sensor network and
Bluetooth lessons learned from the research by
Gvozden Marinkovic (mgvozden_at_eunet.yu)
Aleksandar Radovanovic (biblbroks_at_sezampro.yu)
Aleksandar Beric (alberic_at_eunet.yu)
Branislav Cukanovic (chuka_at_beotel.yu)
Nikola Milanovic (nikola99_at_eunet.yu)

3
Introduction to Ad-Hoc Networks
Evolution of network communications A new
stage
4
Introduction

Two basic groups of ad-hoc networks
Networks of mobile computers handled by users
Wireless sensor networks
Basic characteristic ability to establish
network communication between hosts without any
infrastructure needed.
The most significant advance compared to classic
fixed systems
Reveals a very large scale of new possibilities

5
Introduction

Ad-hoc networks may be considered as a new stage
in evolution of network communications
Fixed computer networks
Concepts and mechanisms educed and amended for
long time
Lot of experiences acquired
A useful base for origin and development of
mobile networks...

6
Introduction

Wireless communication has its peculiarities.
Taking the already developed solutions is not
possible.
In the beginning modifications and adaptations
of existing mechanisms.
Later more and more of new ideas, relieved from
the ballast of obsolete concepts.

7
Mobile Networks
Meet the family
8
Mobile Networks

Not long time ago, mobile networks were treated
just as extensions of fixed networks.
Actors are
Fixed hosts (FH)
Mobile hosts (MH)
Base stations (also known as mobility support
routers MSR)

9
Mobile Networks

Mobility Support Router (MSR)
Every MSR supports the area limited by its range
(wireless cell).
MSR can communicate with MHs currently located in
its cell.
MHs directly communicate only with MSRs
MHs can freely move from one cell to another

10
Mobile Networks

Sending packets from FH to MH
MSRs are bridges between the wired network and
mobile hosts.
When some fixed host (FH) wants to send a packet
to a mobile host (MH), communication is divided
into two parts
Standard communication inside the fixed
network,from FH to the proper MSR
Wireless communication between MSR and MH.

11
Mobile Networks

Hiding mobility
Mediation of MSR is entirely transparent to FH.
For this kind of communication, indirect
protocols were developed, with the purpose of
hiding mobility from immobile hosts.

12
Mobile Networks

One-hop wireless communication
Direct communication between mobile hosts does
not exist
Mobility is very limited and dependant on the
existing wired infrastructure
MHs can move only within areas determined by the
range of MSR, as well as by the range of its own
transmitter
Mobility is limited to only one hop between
mobile host and fixed network
Anyhow, a step towards real, multihop wireless
networks.
Nature of wireless communications had to be
considered
Later was of great benefit for development of
ad-hoc networks

13
Mobile Networks

Nature of wireless communications
Wireless vs wired links
Slower
Less reliable
Prone to loss of signal due to noise and fading
With much more limited bandwidth
With much more frequent occurrence of asymmetric
quality of communication
Mobile hosts are often disconnected from the
fixed network for short or long periods of time
Moving out of range
Exhausted battery

14
Mobile Networks

Realizations and usage possibilities
Wireless Local Area Network (WLAN)
Connecting mobile and portable computers to
existing widely used fixed networks like the
Internet

15
Mobile Networks

Drawbacks and limitations
Infrastructure is needed
Requires large investments
Time consuming installation
Communication cannot be always established where
needed
Expensive maintenance

16
Mobile Networks

In many cases it is necessary to establish a
connection even if infrastructure does not
exist, or is damaged.
Typical example alarming rescuers in case of
earthquake, flood, war destruction
Communication must be established without any
preliminary setup (ad-hoc).

17
Mobile Networks

Ad-Hoc Networks
Mobile hosts can communicate between each other
on much greater distances than covered by their
ranges.
That is practicable thanks to presence of other
mobile hosts that can be reached by the source
host, and that are willing to retransmit its
packets further on
Thus, propagating from one MH to another,
packets are conveyed to the destination
That is how multihop wireless communication
through a temporally formed ad-hoc network is
realized.

18
Routing in Ad-Hoc Networks
How to find the right way?
19
Routing in Ad-Hoc Networks

Efficient routing of packets
In conventional networks, the most widely used
routing algorithms are such as distant vector or
link state
Periodical broadcast, with the purpose of
keeping routing tables up-to-date
In some cases those algorithms were adapted to
be used in ad-hoc networks
We will just mention two representatives
Destination-Sequenced Distance-Vector (DSDV)
Wireless Routing Protocol (WRP)
Benefit Route to every host in the network is
always known. But

20
Routing in Ad-Hoc Networks

Drawbacks of adapted conventional routing
algorithmsseem to be of much more significance
than the benefits
Large bandwidth overhead
Batteries quickly become exhausted
Significantly reduced scalability
Unneeded cumulation of redundant routes
Often not able to quickly enough respond to
dynamics of changes in systems in which the
hosts can move

21
Routing in Ad-Hoc Networks

On-demand routing protocols
Because of specified constraints of said
solutions,we are going to pay more attention on
another approach,which is fundamental for the
so-called on demand routing protocols.
We will shortly describe three of those
protocols, which attack the problem from
different standpoints,introducing different
assumptions and diversely prioritising problems
that are to be solved
Dynamic Source Routing (DSR)
Ad-Hoc On-Demand Distance Vector Routing (AODV)
Temporally Oriented Routing Algorithm (TORA)

22
Routing in Ad-Hoc Networks

All the proposed solutions contribute to the
apparent reclamation of performance, compared to
classic algorithms, which work much better in
the stationary environment for which they were
designed in the first place.
Algorithms that will be presented here are just
specimens of a large number of solutions
developed by now (ietf.org).
New algorithms are still being developed and
evolved.

23
Routing Protocols - DSR

1. Dynamic Source Routing (DSR)
Based on the concept of source routing
Sender provides the sequence of nodes through
which the packets will be sent
Sequences are held in route cache that every
host must maintain for itself
Route is determined dynamically, when it is
needed
There are no periodical advertisements of routers
Instead, every host initiates route discovery
when it needs to send a packet to another host
for which initiator does not have the associated
route in its cache

24
Routing Protocols - DSR

Route Discovery route request
Initiated by sending a route request packet
Propagates through the network until it reaches
the destination host (if the route exists)
On its way, it collects addresses of all visited
hosts, and stores them into its route record

25
Routing Protocols - DSR

Route Discovery route reply
The first route request packet that arrives to
destination is accepted, its route record is
copied and returned to the initiator using the
route reply packet.
Destination host returns the route reply to the
initiator of route discovery, using the route
from its own cache.

26
Routing Protocols - DSR

Route Discovery route reply (2)
If destination host does not have a route to the
source host in its cache, there are two options
Route reply is returned using inverse route that
was found by the route request packet
Destination host initiates route discovery to
find a route to the original initiator.
First option requires symmetric links
Transfer quality must be the same in both
directions
But that is often not the fact in mobile
communications.

27
Routing Protocols - DSR

Route Discovery route reply (3)
Second opportunity (inverse route discovery,
from destination to source) is more significant
Providing support for non-symmetric links (very
important merit of this algorithm).
I that case, the original route reply must be
sent together with new route request, i.e.
attached to it (that is called piggybacking)

28
Routing Protocols - DSR

Route Maintenance
Implemented by acknowledgements and route error
packets.
Acknowledgements may be
hop-by-hop links must be symmetric
end-by-end important when links are not
symmetric

29
Routing Protocols - DSR

Route Maintenance (2)
When using hop-by-hop acknowledgement
Host which did not get acknowledgement for its
retransmissionsends route error packet with
information about hop that broke down
Upon that error packet, source host truncates
routing tree being held in its cache, at the
point of that hop
When using end-by-end acknowledgement
Information about the point of breakage does not
exist
Source host may only assume that the last hop is
broken.

?
30
Routing Protocols - DSR

Modifications / Optimisations
Various modifications and amendments of this
algorithm are feasible.
Well mention just one of them capability of
working in the so-called promiscuous receive
mode
Host auscultate packets that were sent to other
hosts, and updates its own cache according to
the information thus received
This, however, causes more power to be used and
more rapid battery discharge .

31
Routing Protocols - DSR

Summary DSR merits
Ability to work with asymmetric links.
No periodical routing advertisement
Enables bandwidth and energy conservation
Overhead does not exist when there are no
changes in the network.
Can be easily improved to become able for
providing multiple routes
That way, it is not always necessary to initiate
new route discovery when some link breaks.

32
Routing Protocols - DSR

Summary DSR drawbacks
Caused by the nature of source routing.
Large bandwidth overhead
Route request packets rapidly grow as they
propagate through the network(in their route
records they store information about every host
over which they passed)
That causes potential huge route reply packets
Also larger message packets, because addressing
demands the whole route to be specified.
Scalability problems acceptable size of the
network is limited
Diameter of the network (the largest number of
hops needed for communication between any two
hosts in the network)directly refers to
bandwidth overhead.

33
Routing Protocols - DSR

Summary
Dynamic Source Routing protocol is suitable for
appliance in ad-hoc networks
with moderate numbers of mobile hosts
which move with moderate velocities.

34
Routing Protocols - AODV

2. Ad-Hoc On-Demand Distance Vector Routing
(AODV)
New route is discovered in a manner that looks
similar to route discovery by DSR
Source host (src) broadcasts route request (RREQ)
to all of its neighbours when needs to discover
route to some destination host (dst)
Then, it waits for route reply (RREP).
But similarity is discontinued at this point.

?
35
Routing Protocols - AODV

Route Request
Sequence number
Number that every host generates for itself.
It is incremented every time when something is
changed in adjacency (e.g., when some link
breaks).
For every route, destination sequence number
(DSN) is stored in the routing table
Last DSN that src earlier knew for any route to
dst, is sent in RREQ, together with current
sequence number of src and other information
needed RREQ (src, dst, srcSN, dstDSN, )

36
Routing Protocols - AODV

RREQ does not contain the route record
Does not collect information about hosts through
which it propagates
Remembers only the number of hops.
Instead, the host through which RREQ propagates
adds inverse route (towards src) to its routing
table
Stores, together with other relevant information,
the address of the neighbour (n1) that sent RREQ
to it
If that host later receives relevant RREP, it
will automatically know that reply should be
transferred to the neighbour (n1)
In that case, it also records the address of the
neighbour (n2) that sent RREP, thus establishing
route towards dst.

n1
n2
37
Routing Protocols - AODV

Instead of recording the whole route, as with DSR
applied, host here keeps only next hop (among
other relevant information about some
destination), i.e. address of its neighbour to
which it transfers packets addressed to the
destination

38
Routing Protocols - AODV

Route Reply
When RREQ reaches a host that has a route to dst,
comparison of DSNs from the packet and from the
routing table is made
If DSN from RREQ is greater ? the hosts route
to dst is not recent enough ? the host
rebroadcasts the request
Otherwise, the host returns RREP to src, with
the calculated information about the discovered
route (total hop count, lifetime that remains),
among which more recent DSN, copied from the
routing table of the host.

DSN(dst)8
DSN(dst)12
39
Routing Protocols - AODV

RREQ may reach dst itself, and then dst returns
RREP to src.
Anyway, RREP is returned using inverse route
formed by intermediate hosts during the
propagation of RREQ.

dst
src
40
Routing Protocols - AODV

Route Maintenance
For every route that a host is acquainted with,
it maintains the list of neighbours that use
that route, so that it is able to notice them
about eventual link breakage on the route.
Link breakage is detected by the absence of
hello messages, which must be emitted by every
host after the specified time interval expires.

41
Routing Protocols - AODV

Summary Advantages of AODV over DSR
Significantly smaller network bandwidth
overhead
Both control and message packets are smaller
The reason is the requirement of only two
addresses when routing (destination and next
hop), instead of the whole route as with
sequenced routing
This is good for scalability, because the size
of a packet does not depend on the network
diameter.
Provides support for multicasting.

42
Routing Protocols - AODV

Summary AODV drawbacks
Works only with symmetric links.
Hosts must periodically advertise hello messages
Increased bandwidth overhead
Reduced possibility of energy conservation by
remaining in the sleep mode.
Does not support multi path routing(offers only
one route per destination)
Every time when some link on the route breaks,
new route must be discovered
Increased probability of congestion.

43
Routing Protocols - TORA

3. Temporally Oriented Routing Algorithm (TORA)
Offers an interesting approach to problem
solution.
Conceived as link-reversal algorithm.
The idea is to define topology of a network
using a directed acyclic graph (DAG)
Hosts represented as nodes and with directed
links
Direction of link is realized by assigning
height to every node, so that the link is
directed from the node with greater height to
the node with lower height.

44
Routing Protocols - TORA

General idea
The destination node should have the minimal
height in the graph.
Other nodes get greater and greater height as
the distance from the destination grows.
Packets may be sent only from higher to lower
nodes, i.e., only via downstream links.

45
Routing Protocols - TORA

DAG Forming
Starts when node that does not have downstream
links wants to send a packet to a destination
node.
Initially, all nodes in the graph have
undetermined height (NULL), except the
destination node that has the height of ZERO
(which is considered less even from NULL).
Source node then broadcasts QRY packet to its
neighbours.
QRY packet propagates through the network,
marking every node over which it passes as
interested for route discovery by setting its
route request flag.

46
Routing Protocols - TORA

When QRY packet arrives to a node that has at
least one downstream link, the node then emits
the UPD packet.
UPD propagates back through the network, setting
the height to all nodes with the route request
flag set,at the same time resetting those flags.
Every further node gets greater height then the
precedent one on the path of the UPD propagation.

dst
src
47
Routing Protocols - TORA

Many downstream links can lead to the same
destination.
Algorithm enables multiple path routing.

48
Routing Protocols - TORA

In case of link break
If the node still has downstream links left, no
action is performed
Otherwise, the node broadcasts a UPD packet, thus
recovering DAG
Recovering is a one-pass process, except in the
case of network partitioning

49
Routing Protocols - TORA

Advantages of TORA
Fast route discovery
Multiple path routing
Recovering is localised
Multicast support
Lightweight Adaptive Multicast (LAM) algorithm

50
Routing Protocols - TORA

Downsides of TORA
Requires external timing mechanism (GPS)
DAG becomes less optimal as the time passes
Can be solved using refresh packets

51
Routing Protocols - TORA

TORA is designed for
Large networks
Many nodes with dense distribution

52
Issue of Security in Ad-Hoc Networks
There is no need to see his identification...
53
Attributes of security

The attributes of security are
Availability
Confidentiality
Integrity
Authentication
Non-repudiation.

54
Attributes of security

Availability ensures the survivability of
network services despite denial of service
attacks.
A denial of service attack could be launched at
any layer of an ad hoc network.
On the physical and media access control layers,
an adversary could employ jamming to interfere
with communication on physical channels.
On the network layer disruption of the routing
protocol can cause a break of the network.

55
Attributes of security

Confidentiality ensures that certain information
is never disclosed to unauthorized entities.
Leakage of information could have devastating
consequences.
Routing information must also remain confidential
in some cases.

56
Attributes of security

Integrity guarantees that a message being
transferred is never corrupted.
A message could be corrupted because of benign
failures, such as radio propagation impairment,
or because of a malicious attacks on the
network.

57
Attributes of security

Authentication enables a node to ensure the
identity of the peer node it is communicating
with.
Without authentication, an adversary could
masquerade a node, thus gaining unauthorized
access to resource and sensitive information and
interfering with the operation of other nodes.

58
Attributes of security

Non-repudiation ensures that that the origin
of a message cannot deny having sent the
message.
Non-repudiation is useful for detection and
isolation of compromised nodes.

59
Challenges and opportunities

Attacks ranging from passive eavesdropping to
active impersonation, message replay, and message
distortion.
Eavesdropping might give an adversary access to
secret information, violating confidentiality.
Active attack might allow the adversary
to delete messages,
to inject erroneous messages,
to modify messages, and
to impersonate a node
Violating availability, integrity,
authentication, and non-repudiation.

60
Challenges and opportunities

We should take into account the attacks launched
from within the network, by compromised nodes.
The ad-hoc networks should have a distributed
architecture with no central entities.
Introducing any central entity into our security
solution could lead to significant vulnerability.

61
Challenges and opportunities

There are two sources of threats to routing
protocols
from external attackers
from compromised nodes

62
Challenges and opportunities

Detection of incorrect information is difficult
Outdated routing information
False routing information generated by
compromised nodes
could be considered as the outdated
information
If routing protocols can discover multiple
routers, nodes can switch to an alternative route

63
Challenges and opportunities

Another way is to use diversity coding
Diversity coding takes advantage of multiple
paths in an efficient way, without message
retransmission
Even if certain routes are compromised, the
received node may still be able to validate and
to recover messages

64
Challenges and opportunities

Cryptographic schemes
digital signature
public and private keys
Key management service
A public key infrastructure is superior in
distributing keys and in achieving integrity and
non-repudiation.
In a public key infrastructure, each node has a
public/private key pair.
Public keys can be distributed to other nodes,
while private keys should be kept
confidential
to individual nodes.

65
Challenges and opportunities

There is a trusted entity called Certification
Authority (CA) for key management.
The CA has a public/private key pair
Public key is known to every node
CA signs certificates binding public keys to
nodes
The trusted CA has to stay on-line to reflect the
current binding
Although no single node is trustworthy in an ad
hoc network we can distribute trust to an
aggregation of nodes.
Assuming that any t1 nodes will unlikely be all
compromised, consensus of at least t1 nodes is
trustworthy.

66
Challenges and opportunities

This is the principle of distributed trust.
To accomplish distribution of trust in key
management service one can use threshold
cryptography.
An (n,t1) threshold cryptography
scheme allows n
parties to share the ability to perform a
cryptographic
operation (e.g., creating a
digital
signature), so that any t1 parties

can perform this operation jointly,
whereas it
is infeasible for most t
parties to do so,
even by collusion.

67
Challenges and opportunities

We divide the private key k of the service into n
shares (s1,s2,,sn), assigning one share to each
server.
Each server generates a partial signature for the
certificate using its private key share
With t 1 correct partial signature, the
combiner is able to compute the signature for the
certificate.
Compromised servers cannot generate correctly
signed certificates by themselves

68
Challenges and opportunities

A combiner can verify the validity of a computed
signature using the service public key.
In case verification fails the combiner tries
another set of partial signatures.
A problem with threshold cryptography is that it
assumes synchronous system and an ad hoc network
is asynchronous by its nature
Any synchrony assumption is a vulnerability in
the system
Fortunately there is an asynchrony prototype of
such a key management service, which has been
implemented recently.

69
Summary

An ad hoc network is very vulnerable to many
kinds of attacks.
We have to protect not only the data, but also
the routing information.
The best way for that is a cryptography scheme
with public/private key management, combined
with distribution of trust.
But it is not cheap and it is complex.
A lot of things still have to be done in this
area in the future.

70
Bluetooth
Following the steps of King Harald...
71
Bluetooth
Special Interest Group (SIG)

Ericsson Mobile Communications AB
IBM Corp.
Intel Corp.
Nokia Mobile Phones
Toshiba Corp.

72
Bluetooth
Bluetooth wireless technology

Open specification for short-range wireless
connectivity
Effortless, instant connections
Wide range of communication devices
Based on a radio link
Facilitates fast and secure transmission of both
voice and data
Operates in a globally available frequency band

73
Bluetooth
Bluetooth module

ports (USB, UART, PCM)
baseband
voltage regulator
crystal
radio
antenna interface
flash

74
Bluetooth

External interfaces
USB 1.1 (12 Mbps), full USB slave functionality
UART (Rx, Tx, RTS and CTS), 460.8 kbs
PCM (sync 8kHz, clock 200kHz-2MHz)
Antenna Interface
50 ohm Bluetooth ISM band antenna (2.4 - 2.5 GHz)

75
Bluetooth

Communication layers
Base Band (BB)
Link Manager (LM)
Host Controller Interface (HCI)
Additional software
L2CAP
RFCOMM

76
Bluetooth

Base Band General Description
Frequency hop transceiver
Shaped, binary FM modulation
Symbol rate is 1 Ms/s
Slotted channel is applied with a nominal slot
length of 625 ms.
Time-Division Duplex (TDD) scheme
Information is exchanged through packets
Each packet is transmitted on a different hop
frequency
Combination of circuit and packet switching.

77
Bluetooth

Bluetooth can support
Asynchronous data channel
Up to three simultaneous synchronous voice
channels
Channel which simultaneously supports
asynchronous data and synchronous voice

78
Bluetooth

Bluetooth system consists of
Radio unit
Link control unit
Link management and host terminal interface
functions

79
Bluetooth

Connection types
point-to-point
point-to-multipoint

Master/slave communication
piconets
scatternets

80
Bluetooth

Other features
Link Manager Protocol
Logical Link Control
Service Discovery Protocol
RFCOMM
IrDA
Telephony Control Protocol
...

Potential platform for ad-hoc network
realization!
81
Design of ad-hoc multihop sensor net with
Bluetooth Lessons learned
How to make your electronic devices cooperate
with each other?
82
Introduction

The main goals of this project
Creating hw/sw specification for replacing and/or
upgrading the existing wire systems for data
acquisition and process control
Development of routing protocol
Connecting Bluetooth with a microcontroller
(router)
Integration of routing protocol on the base
Bluetooth chip
Universal platform for wireless integration
Stable and universal hardware platform
Reliable and easy replaceable software

83
System Overwiev

An open data acquistion system, based on wireless
ad-hoc multihop sensor network
Routing protocol
Interface and routing module (IFRM)
Personal Digital Assistant (PDA)
Digital Signal Processing System (DSPS)
Software for data acquisition (Shell)
Internet accessible database

84
System Overview
85
System Overview

Basic advantages
Universal and open platform
Can be implemented in any environment
Possibilites of use
Factories
Power plants
Health-care institutions
Rescue actions
Research of inhospitable terrain

86
System Overview

Main problems
Providing critical data transmission rate
Stable ad-hoc networks
Proposed solutions
Bluetooth technology
Designed routing protocol

87
Implementation - routing protocol

Designed with the following guidelines
speed
reliability
simplicity
Existing solutions considered
DSR
AODV
TORA

88
Implementation - routing protocol

The routing algorithm defines three types of
messages
Route Request (RREQ)
Route Reply (RREP)
Route Error (RERR)

89
Implementation - routing protocol

Route Request

90
Implementation - routing protocol

Route Reply

91
Implementation - routing protocol

Route Error

92
Implementation - routing protocol

Functioning of the protocol
Master
Gateway
Slave

93
Implementation - routing protocol

Possible network topology

94
Implementation - routing protocol

System initialization
Forming of piconets
Creation of neighboor tables
Initialization of empty routing tables

95
Implementation - routing protocol

Routing table entry

96
Implementation - routing protocol

Sending RERR
Link is broken
No active route to destination
RRER is received from a neigboring node

97
Implementation - routing protocol

Simulation
Starting topology specified in the configuration
file
Number of nodes is not limited
For each node, a separate thread of execution is
created
Messages and destinations are being generated in
random fashion
Traversing of nodes between piconets

98
Implementation - routing protocol

Process of route discovery (RREQ forwarding)

99
Implementation - routing protocol

Process of route discovery (RREP forwarding)

100
Implementation - routing protocol

Usability analysis
Advantages compared to classic broadcast
algorithms

101
Implementation - routing protocol

Usability analysis
Elimination of redundant piconets

102
Implementation - IFRM

The routing protocol was implemented
in a separate hardware module
Serial (UART) connection with Bluetooth
HCI level

103
Implementation - IFRM

The main functions of IFRM
Forming of a wireless multihop ad-hoc network
Link maintenance
Packet routing
Route discovery
Providing a transparent interface between the
ad-hoc network and any serial (RS-232) device
Providing PDA functionality

104
Implementation - IFRM

The architecture of IFRM

105
Implementation - IFRM

Routing protocol - host side
The modified AODV protocol, with the following
restrictions
Size of routing tables is limited to 79 entries
Communication in the network is server centric

106
Implementation - IFRM

Routing protocol - host side
The modified AODV protocol, with the following
restrictions
End-to-end flow control is omitted
CRC checking and retransmission are not
implemented
Packet sequence is not checked
Restrictions due to fact that Bluetooth modules
do not conform to the Bluetooth V1.0B
specification

107
Implementation - IFRM

Routing protocol - host side
Assumptions due to uncomformance to V1.0b
specification
In course of full-duplex communicationthere is
no implicit master-slave switch
Inquiry and paging are possible without
interfering with the current transmission
Only the master can broadcast on the piconet
A node can transparently be a member in more
piconets(Bluetooth baseband controller is
capable of transparent TD multiplexing)
It is possible to have more than 7 nodes in a
piconet(parking and unparking is done
transparently by the baseband controller)

108
Implementation - IFRM

Routing protocol - host side
Bugs and workarounds
Sending two consecutive broadcast packets causes
a reset
During maximum full-duplex transfer, packets or
parts of the packets disappear

109
Implementation - IFRM

Connection of IFRM with the mobile host

110
Implementation - IFRM

Routing protocol - server side
No routing module
The software performs routing
Special mechanism for implicit destination
address discovery

111
Implementation - IFRM

Routing protocol - server side
Communication with Bluetooth
TCP ports
For each mobile host exists a corresponding TCP
port on the sever
Port numbers start from 10 000
All communication is performed over the TCP/IP
connections on these ports
The mapping of ports and hardware addresses of
Bluetooth modules is static

112
Implementation - PDA

The role of PDA is to provide mobility to the
expert.
PDA is capable of receiving two types of
messages
Sensors have reported irregular data, but expert
system managed to stabilize the system. The
confirmation is required.
Sensors have reported irregular data and expert
system did not manage to stabilize the system.
The remote command and presence is required.
PDA is capable of sending two types of messages
Confirmation of received warning
Command that initiates some action in the system,
based on received data
In this phase, the internal battery supply is not
designed.

113
Implementation - DSPS

DSPS is realised as an example of device
that can be connected to this platform.
Based on TI Digital Signal Processor
Gathering of information from different
peripherals
Real-time processing
Transferring data to server over IFRM

114
Implementation - DSPS

The DSPS architecture

115
Implementation - DSPS

DSPS Communication
Standard RS-232 connection (MAX3225cpp)
CAN driver
Synchronous Serial Interface (SPI)

116
Implementation - DSPS

DSPS function
Finding spectrum of some analog signal using FFT
Transferring data to server via transparent
ad-hoc network
Receiving commands from the system, thus
creating positive feedback system

117
Implementation - Shell

Multipurpose software platform
Data acquisition
Decision making
Signal processing
Slarming
Tracking the current stateof the system
Database administration

118
Implementation - Shell

Communication with sensors
TCP/IP ports
Two-way socket communication
Conformance to IEEE 999-1992. SCADA specification

119
Implementation - Shell

System configuration
Type of the sensor
Name of the sensor
Factory address of corresponding Bluetooth
module
Range of allowed values

120
Implementation - Shell

Readings display
Simple view
Graph view
Real-time monitoring
History

121
Implementation - Shell

Spectrum analysis

122
Implementation - Shell

Database
Realized with MySQL Server
ODBC
Flexible, DBMS independent

123
Implementation - Shell

Expert System
Monitoring (controlling)
Knowledge base
Algorithm of direct chaining
Based on preconditions (sensor readings) and
using the rules, the expert system reaches a
decision
Depending on the actual application, any expert
system with its knowledge base can be easily
integrated

124
Implementation - Internet connectivity