Report Icwcs

8/2/2019 Report Icwcs

1/24

In-Cave Wireless Communication

Dept of ECE, MSEC Bangalore 1

Chapter 1

INTRODUCTION


2/24



Here we concentrate on robust voice communication architecture for caves

based on wireless multimedia sensor networks. Although the outdoor use of radio

frequencies (RF) for communication has been a very ingrained and convenient technique for

a quite long time, indoor environments make the use of RF signals for communicationdifficult because of attenuation, reflection, refraction, diffraction and scattering that have

negative effect on RF signals. In caves, obstacles such as walls, rocks and curvatures with

rough surfaces amplify the negative effects of the mentioned distortions on the RF signals,

making wireless voice communication especially difficult. This architecture aims to

overcome these difficulties by use of a Wireless Multimedia Sensor Network (WMSN) with

densely deployed backbone nodes and scattered mobile nodes, so RF communication

between mobile nodes over the backbone can guarantee a desired level of uninterrupted

connectivity and communication quality.

There are some different types of cable-based systems used for in-cave

communication. One of them is known as single-wire telephone (SWT). The SWT, also

known as earth-return telephone, uses the conductivity of the ground to provide a return

path for the current. So, only one core cable is used in SWT, which reduces the weight of

the cable by fifty percent. In caves, both coaxial and single core copper cables become

bulky to handle especially with increased cable lengths. Therefore more weight efficient

solutions for in-cave communication are preferred. One such solution is the use of optical

fibers. Optical fibers weigh less, have greater bandwidth and noise immunity compared to

copper cables which tend to pick up random noise from the environment with longer cablelengths.

Although noise and cable weight problems can be compensated with the use

of optical fibers, there are still problems associated with the installation of these cable based

communication network within caves. Caves with multiple paths require the cables to be

split into multiple branches and each branch requires a connection to the main cable. These

connections can be made relatively easily with copper cables but each new connection has

negative effect on the communication quality. On the other hand, connecting optical fibers

together is a highly skilled task and requires the use of special hardware. Therefore, we

concentrate on WMSN based architecture for in-cave communication which is basically

composed of densely deployed backbone nodes and scattered mobile nodes. That gives rise

to In-Cave Wireless Communication System (ICWCS).


3/24



Chapter 2

WIRELESS MULTIMEDIA SENSOR NETWORK


4/24



Wireless sensor networks have drawn the attention of the research community

in the past few years. This growing interest can be largely credited to new applications

enabled by large-scale networks. Small devices are capable of harvesting information from

the physical environment, performing simple processing on the extracted data, and

transmitting it to remote locations. Most deployed wireless sensor networks measure scalar

data such as temperature, pressure, humidity, or the location of objects. In general, most of

the applications have low bandwidth demands and are usually delay tolerant. While the

traditional wireless sensor networks consist of low-bandwidth sensors with limited

capabilities, camera sensor networks can provide visual verification, in-depth situational

awareness, recognition, and other capabilities.

In recent years, wireless sensor networks have inspired tremendous research

interest in diverse application fields such as structural health monitoring, environmental

monitoring, and military and security surveillance. A typical wireless sensor network

consists of sensor nodes, each equipped with various kinds of sensors, deployed over a

geographical region of interest. Most of the applications are centered towards harvesting

information from the physical environment, performing a simple processing on the extracted

data and transmitting it to remote locations.

A new direction in wireless sensor network application design centers on the

idea of enabling the network to learn the behavior of the trend in the environment rather than

merely making measurements and reporting about a single event or information of interest.

A Wireless Multimedia Sensor Network (WMSN) is defined as a network of wireless

embedded devices that allow retrieving video or audio streams, still images, and scalar sensor

data. A WMSN ties the notion of wireless sensor networks and distributed smart cameras .

Wireless multimedia sensor networks will not only enhance existing sensor network

applications such as tracking, home automation, and environmental monitoring, but they will

also enable several new applications such as multimedia surveillance sensor networks.


5/24



Components to build a WMSN can be very expensive and difficult to work

with or program due to the complicated algorithms and required hardware construction. We

had to decide on the type of microprocessor to use to run our node along with a camera with

good resolution that could capture effective images. Considered two microprocessor

modules: the ARM7 microprocessor and the Overo Air computer-on-module. The Overo

seemed like a better choice due to its extensive wireless capabilities that the ARM7 did not

have. Camera module that supports the Overo Air computer-on-module. It connects to the

Overo Air through a J5 flex circuit cable connector, making it simpler to communicate

between the two devices.

Major components of network are:

Standard Audio and Video sensors Scalar sensors Multiple processing hubs Storage hubs Sink Gateway Users

The problem of designing a scalable network architecture is of primaryimportance. Most proposals for wireless sensor networks are based on a flat, homogenous

architecture in which every sensor has the same physical capabilities and can only interact

with neighboring sensors. Traditionally, the research on algorithms and protocols for sensor

networks has focused on scalability, i.e., how to design solutions whose applicability would

not be limited by the growing size of the network. Flat topologies may not always be suitedto handle the amount of traffic generated by multimedia applications including audio and

video. Likewise, the processing power required for data processing and communications, and

the power required to operate it, may not be available on each node.

2.1 NETWORK COMPONENTS

2.2 NETWORK ARCHITECTURE


6/24



Fig. 2.1 Reference architecture of a wireless multimedia sensor network

In Fig. 2.1 Architecture for WMSNs, where three sensor networks withdifferent characteristics are shown, possibly deployed in different physical locations. The

first cloud on the left shows a single-tier network of homogeneous video sensors. A subset of

the deployed sensors have higher processing capabilities, and are thus referred to as

processing hubs. The union of the processing hubs constitutes a distributed processingarchitecture. The multimedia content gathered is relayed to a wireless gateway through a

multi-hop path. The gateway is interconnected to a storage hub, that is in charge of storing

multimedia content locally for subsequent retrieval. Clearly, more complex architectures fordistributed storage can be implemented when allowed by the environment and the application

needs, which may result in energy savings since by storing it locally, the multimedia content

does not need to be wirelessly relayed to remote locations. The wireless gateway is also

connected to a central sink, which implements the software front-end for network queryingand tasking.

The second cloud represents a single-tiered clustered architecture ofheterogeneous sensors (only one cluster is depicted). Video, audio, and scalar sensors relay

data to a central cluster head, which is also in charge of performing intensive multimedia

processing on the data (processing hub). The cluster head relays the gathered content to the

wireless gateway and to the storage hub.

The last cloud on the right represents a multi-tiered network, withheterogeneous sensors. Each tier is in charge of a subset of the functionalities. Resource-

constrained, low-power scalar sensors are in charge of performing simpler tasks, such as

detecting scalar physical measurements, while resource-rich, high-power devices areresponsible for more complex tasks. Data processing and storage can be performed in a

distributed fashion at each different tier.


7/24



Chapter 3SENSOR NODES ARCHITECTURE


8/24



A wireless sensor node is composed of four basic components. A sensing unit,

a processing unit (microcontroller), a transceiver unit and a power unit . In addition to the

above units, a wireless sensor node may include a number of application specific

components, for example a location detection system or mobiliser; for this reason, many

commercial sensor node products include expansion slots and support serial wired

communication.

Fig: 3.1 Sensor Node Architecture


9/24



Components of a Wireless Sensor Node:

Sensing Unit:

A sensor is a device that measures some physical quantity and converts it into

a signal to be processed by the microcontroller. A wide range of sensor types exist including

seismic, thermal, acoustic, visual, infrared and magnetic. Sensors may be passive (sensing

without active manipulation of the environment) or active (using active manipulation/probing

of the environment to sense data, e.g. radar) and may be directional or omni-directional. A

wireless sensor node may include multiple sensors providing complimentary data. The

sensing of a physical quantity such as those described typically results in the production of a

continuous analogue signal, for this reason, a sensing unit is typically composed of a number

of sensors and an analogue to digital convertor (ADC) which digitises the signal.

Microcontroller:

A microcontroller provides the processing power for, and coordinates the

activity of, a wireless sensor node. Unlike the processing units associated with larger

computers, a microcontroller integrates processing with some memory provision and I/O

peripherals; such integration reduces the need for additional hardware, wiring, energy and

circuit board space. In addition to the memory provided by the microcontroller, it is not

uncommon for a wireless sensor node to include some external memory, for example in the

form of flash memory.

Transceiver:

A transceiver unit allows the transmission and reception of data to other

devices connecting a wireless sensor node to a network. Wireless sensor nodes typically

communicate using an RF (radio frequency) transceiver and a wireless personal area

network technology such as Bluetooth or the 802.15.4 compliant protocols ZigBee [2] and

MiWi [3]. The 802.15.4 standard specifies the physical layer and medium access control for

low-rate, low-cost wireless communications whilst protocols such as ZigBee and MiWi build


10/24



upon this by developing the upper layers of the OSI Reference Model. The Bluetooth

specification crosses all layers of the OSI Reference Model and is also designed for low-rate,

low-cost wireless networking. Wireless sensor communications tend to operate in the RF

industrial, scientific and medical (ISM) bands which are designed for unlicensed operation.

Power Source:

As an untethered computing platform, wireless sensor nodes must be

supported by a power unit which is typically some form of storage (that is, a battery) but

may be supported by power scavenging components (for example, solar cells). Energy from

power scavenging techniques may only be stored in rechargeable (secondary) batteries and

this can be a useful combination in wireless sensor node environments where maintenance

operations like battery changing are impractical. To conserve energy a power unit may

additionally support power conservation techniques such as dynamic voltage scaling.

For the two different types of wireless sensor nodes employed in ICWCS, two

different types of batteries were used according to the power requirements of the nodes.

Backbone nodes are stationary and they must be operational for long periods of time, so they

are equipped with high capacity batteries. On the other hand mobile nodes are equipped withbatteries of lesser capacity for making them more portable. Also spare batteries can be

carried by the users to extend the standard standby and operational time.

In our current design, ICWCS backbone nodes were powered with 12V,

1.3Ah batteries which provide a little more than 7 days of continuous operation. The mobile

nodes were equipped with three rechargeable 1.2V, 700mAh AAA size batteries which

provide nodes thirty hours of continuous operation

ENERGY ISSUES


11/24



Chapter 4

ICWCS NODES


12/24



The basic purpose of ICWCS is to provide a reliable voice communication

channel over a WMSN between the members of a team in a cave as shown in Fig. 1. ICWCS

consists of two different types of nodes. The skeleton of this networkis formed by backbone

nodes which are mounted on the walls of the cave. Mobile nodes, which have similar

functionality like cellular phones, are carried by the team members.

Backbone nodes are stationary nodes and their design is based on our previous

general purpose wireless sensor node VF1A . They have a processor module, an RF

transceiver module, a memory module and a power management module. These nodes are

responsible for maintaining the backbone connectivity within the cave, the registration and

roaming activities of mobile nodes, routing call information between mobile nodes, andcarrying the control and voice data over the wireless network shown in Fig 4.1

Fig: 4.1 Backbone Node Structure

4.1 BACKBONE NODES


13/24



Mobile nodes are carried by cavers and include features beyond the standardones of a wireless sensor node for the interaction with the cavers. These features include a

graphical display, a microphone, an earphone and a control keypad.

A mobile node is an Internet-connected device whose location and point of

attachment to the Internet may frequently be changed. This kind of node is often a cellular

telephone or handheld or laptop computer, although a mobile node can also be a router.Special support is required to maintain Internet connections for a mobile node as it moves

from one network or subnet to another, because traditional Internet routing assumes a device

will always have the same IP address. Therefore, using standard routing procedures, a mobile

user would have to change the device's IP address each time they connected through another

network or subnet. Since mobility and ease of connection are crucial considerations formobile device users, organizations that want to promote mobile communications are putting

a great deal of effort into making mobile connection and uncomplicated for the user.

The graphical display is used to inform the user about the current status of the

mobile node which includes RF signal strength, remaining battery capacity, connected

backbone node. The control keypad is used to manage both incoming and outgoing voicecalls. The design of the mobile nodes is also based on VF1A, but as stated above has some

extra features. Also for digitizing and playing back of voice a low power codec was added to

the design of VF1A.

In wireless sensor networks, nodes lack a global id like an IP address inlegacy networks, therefore a simple yet efficient method for addressing nodes is required.

VF1A sensor nodes have a unique 64-bit id which was used for the identification and

addressing of the nodes in ICWCS. Each mobile node and thus its user are registered to theICWCS directory server, which stores the ids of the backbone and mobile nodes, usernames,

status and location information of the mobile nodes. The information stored in the directory

server is used for establishing real time communication between online users, monitoring and

detecting battery related connection failures, and to narrow the reconnaissance area in the

case of a rescue operation within the cave.

4.2MOBILE NODES

4.3NODES NETWORK
http://searchmobilecomputing.techtarget.com/definition/cellular-telephonehttp://searchmobilecomputing.techtarget.com/definition/cellular-telephonehttp://searchmobilecomputing.techtarget.com/definition/handheldhttp://searchmobilecomputing.techtarget.com/definition/laptop-computerhttp://searchnetworking.techtarget.com/definition/routerhttp://searchnetworking.techtarget.com/definition/subnethttp://searchwindevelopment.techtarget.com/definition/IP-addresshttp://searchwindevelopment.techtarget.com/definition/IP-addresshttp://searchnetworking.techtarget.com/definition/subnethttp://searchnetworking.techtarget.com/definition/routerhttp://searchmobilecomputing.techtarget.com/definition/laptop-computerhttp://searchmobilecomputing.techtarget.com/definition/handheldhttp://searchmobilecomputing.techtarget.com/definition/cellular-telephonehttp://searchmobilecomputing.techtarget.com/definition/cellular-telephone


14/24



Fig: 4.2 Node Network

Each backbone node also registers itself to the ICWCS directory server for

backbone network monitoring. Status information including remaining battery capacity of

backbone nodes will be sent to the directory service periodically. The directory service isusually run on a computer outside the cave, but to accelerate directory operations, backbone

nodes employ a caching mechanism. The information within the cache of the backbone nodes

is updated periodically.


15/24



ICWCS OPERATION

Chapter 5


16/24



Several steps including deployment, initial setup and routing, Node call

registration, call management and broken link and recovery must be performed before an

ICWCS becomes operational. The details of these steps are given in the following

Sub topics.

Wireless sensor networks can be deployed either manually or randomly. In

ICWCS, the backbone nodes are required to be deployed manually as the cavers move along

the cave farther. Each backbone node has a simple RSSI indicator, which shows the

connection quality to the last deployed backbone node, so the user has the opportunity toplace the backbone node at an optimum distance to the last backbone node. This way a

dynamic backbone network is deployed within the cave as the cavers move forward .

Whenever a new backbone node is permanently laid out, the updated topology

information is exchanged between the backbone nodes and then sent to the directory service.When updating topology information, the backbone nodes exchange their routing tables to

recalculate the next hop to every other backbone node. For the routing protocol we preferred

to employ a simplified link state routing algorithm which is suitable for wireless sensornetworks because of its low message overhead .This way all backbone nodes know how to

reach a particular backbone node and thus its registered mobile nodes. A sample routing table

exchange operation is given. The age column in the routing table is used to detect the dead

backbone nodes in the network. When a backbone node does not receive data from aneighboring backbone node within a predefined timeout, the value of the corresponding age

column is decremented by one. An age column with a value of zero indicates a dead neighbor

backbone node. Table 2 shows the final routing table of backbone node BN4 for the networkgiven.

Each mobile node must register itself to the ICWCS network to becomeoperational. When a mobile node is powered on, it broadcasts a registration request message

in order to register itself to the ICWCS directory service. The backbone nodes that receive

registration message initiate a directory service lookup for the verification of the identity

5.1 DEPLOYMENT

5.2 INITIAL SETUP AND ROUTING

5.3 MOBILE NODE REGISTRATION


17/24



of the mobile node. Upon receiving a positive reply regarding the identity of the mobile

node, the backbone nodes acknowledge this registration request back to the mobile node. In

cases where more than one positive acknowledgement is received by the mobile node, themobile node decides which backbone node to register with using the RSSI functionality.

A mobile node can retrieve a list of the online users within the ICWCS

network and show this information to the user on its graphical display. The retrieved list ofthe online users can be a partial list when the ICWCS network is in the beaconing state and

the backbone node does not have access to the connection table on the directory service or a

full list when the directory service is accessible. Users can then select any of the online users,

and initiate a voice communication with that user. The id of the selected destination usersmobile node is sent to the registered backbone node to forward the call request to the

destination mobile node. If the user of the destination node accepts the incoming call request,

a voice communication channel between the source and the destination mobile node isestablished. Otherwise a negative acknowledgement is returned to the source mobile node.

The current Mobile Node connection table of the network on the directory service is shown

Table 1 Initial Routing Setup

5.4 CALL MANAGEMENT


18/24



Table: 2 Final Routing Table

Table: 3 MN Connection Table

When a backbone node becomes dead, the backbone network will be broken

unless the two immediate upstream and downstream neighbors of the dead backbone node

can establish a direct connection. In this case, the ICWCS enters the beaconing state. In this

state, the operation of the dead backbone node should be resumed by either replacing the

batteries or the node itself. Each backbone node uses the age column in its routing table todetect whether the beaconing state should be entered. After each successful communication

with the neighboring backbone nodes, each backbone node updates the corresponding agevalues with the predefined timeout value. Whenever the value in an age column becomes

zero this indicates that no successful communication has occurred within the timeout period,

so the backbone node concludes that the corresponding backbone node is dead. In the

beaconing state, the detecting upstream and downstream backbone nodes broadcast a

5.5 BROKEN LINK DETECTION AND RECOVERY


19/24



warning message to all online mobile nodes and the directory server. This way, still

reachable users get notified about this network failure.

The backbone nodes which forward the broadcast message delete the entry for

the failed backbone node from their routing table. After the dead backbone node is replaced,

the new backbone node advertises its presence to the neighboring backbone nodes, whichtriggers the regeneration of the routing tables over the ICWCS backbone network. When a

connection is established between mobile nodes, the participating backbone nodes save an

entry in their caches to accelerate future call establishment to these mobile nodes. With this

caching mechanism, future calls to the cached mobile nodes will not require an interactionwith the directory server, unless the mobile node has roamed to another backbone node.

Additionally when no connection to the directory server is available, themobile nodes may still be able to communicate with the other reachable mobile nodes,

unless they have changed their registered backbone node. Assuming that the mobile nodes

MN2 and MN3 in Fig. 5.4.1 have established a connection over the time and the backbonenode BN4 has cached the ids of MN2 and MN3, MN2 can still establish a new connection to

MN3 even if BN1 becomes dead, which would have normally prevented querying the

directory service for the location of MN3.


20/24



FEATURES TECNOLOGIES OF WMSNs

Chapter 6


21/24



Multimedia in-network processing in WMSNs:

Distributed source coding in WMSNs Multimedia aggregation and fusion in WMSNs Low-bit rate and energy-efficient multimedia source coding for WMSNs

WMSN architectures and applications:

Scalable and flexible WMSN architecture WMSN design for supporting heterogenous applications Multimedia sensor coverage Novel WMSN applications Experimental studies of WMSNs WMSN modelling and performance analysis

Emerging WMSN technologies:

Hardware platforms Physical layer technologies Energy harvesting technologies

Effective and energy-efficient protocols for WMSNs:

Real-time and reliable multimedia streaming Routing and medium access control Topology control and synchronisation protocols Energy efficient traffic management QoS provisioning protocols

Cross-layer design in WMSNs:

Joint multimedia processing and communication Cooperative communication for multimedia delivery Effective cross-layer communication protocols Joint optimisation for WMSN design

Data management for WMSNs:

In-network and distributed storage techniques for WMSNs Lightweight multimedia encoding techniques Collaborative in-network processing Energy-efficient DBMS for WMSNs


22/24



ADVANTAGES:

The availability of low-cost hardware such as CMOS cameras and microphones hasfostered the development of Wireless Multimedia Sensor Networks (WMSNs), i.e.,

networks of wirelessly interconnected devices that are able to ubiquitously retrieve

multimedia content such as video and audio streams, still images, and scalar sensordata from the environment.

The state of the art in algorithms, protocols, and hardware for wireless multimediasensor network are easily designable in multimedia environments.

Currently off-the-shelf hardware as well as available research prototypes formultimedia sensor networks are possible with cross-layer synergies andoptimizations.

.DISADVANTAGES:

Must put powerful protection to protect your connection in case somewhere betweenyour laptop & WiFi, there is a hacker steals your WiFi connection, resulting the WiFi

range reduction

.Must put powerful protection to protect your data in case somewhere between yourlaptop & WiFi, there is a hacker steals your data, resulting your firewall/antivirus

must work extra to encrypt the data to check and then decrypt it again beforetheencryption software opens it

ADVANTAGES DISADVANTAGES OF WMSNs


23/24



Here we focused on building a reliable voice communication network with

the use of wireless multimedia sensor nodes in RF challenged indoor environments. We havedesigned wireless multimedia sensor nodes based on our previous researches. Two different

types of wireless sensor nodes were designed based on the design of our previous sensornode. One sensor node design was used as the backbone nodes of the ICWCS and the other

one with multimedia features was used as the mobile nodes.

Our current implementation of ICWCS handles only one active point to pointvoice communication. We can Still look to improve the work on the concurrent voice

communications with multicast and broadcast capabilities to improve the performance of

ICWCS.

Reliable voice communication can be provided byWMSN in RF challenged indoor environment. Two different types of sensor nodes were used,their design was based on VF1A sensor node. This ICWCS is a point-to-point

communication, it is being improved to have multicast and broadcastc abilities

Conclusion


24/24


Dept of ECE MSEC Bangalore 24

1. Pingenot J., Rieben R., White D., "Full Wave Analysis of RF Signal Attenuation in aLossy Cave using a High Order Time Domain Vector Finite Element Method"IEEE/ACES International Conference on Wireless Communications, IEEE Press, Apr.

2005, pp. 658 - 661, doi: 10.1109/WCACEM.2005.1469674.

2. Kalomiris V. E., Abbott R. W., Sherrets L. R., A Dual Use Fiber Optic Video andAudio Link, Military Communications Conference, IEEE Press, Nov. 1993, pp. 858-863, doi: 10.1109/MILCOM.1993.408698.

3. Taysi Z. C., Yavuz A. G., Considerations for Design of a General Purpose WirelessSensor Node, ECC 2007, in press.

4. Clausen T., Jacquet P., Optimized Link State Routing Protocol (OLSR), ProjectHipercom, October 2003.

5. Palmertree B., Bronez T., Semanchik T., Wireless Relay Communications for RFChallenged Environments The Mitre Corporation, 2005.

6. Gibson D., Darnell M., Adaptive Digital Communications for Sub-Surface RadioPaths, CREG Journal, ISSN 1361-4800, Dec 1999.

7. Tian He, Stankovic J.A., Chenyang Lu, Abdelzaher, T. , SPEED: A Stateless Protocolfor Real-time Communication in Sensor Networks, 23rd International Conference onDistributed Computing Systems, IEEE press, May 2003, pp.46 - 55, doi:

10.1109/ICDCS.2003.1203451.

8. Li L., Xing G., Sun L., Liu Y. ,QVS: Quality-aware Voice Streaming for WirelessSensor Networks, ICDCS 2009, in press.\

9. Mangharam, R., Rowe, A., Rajkumar, R., Suzuki, R., "Voice over Sensor Networks",Real-Time Systems Symposium, 2006. (RTSS '06), IEEE Press, Dec. 2006, pp. 291 -302, doi: 10.1109/RTSS.2006.51

10..Brunelli, D., Teodorani, L., "Improving audio streaming over multi-hop ZigBeenetworks", Computers and Communications, 2008 (ISCC 2008), IEEE Press, Jul. 2008,pp. 31 - 36, doi: 10.1109/ISCC.2008.4625771.

11. Wang C., Sohraby K., Jana R., Ji L., Daneshmand M.. "Voice communications overzigbee networks" Communications Magazine, IEEE, vol. 46(1), Jan. 2008, pp. 121 - 127,doi: 10.1109/MCOM.2008.4427240.

Re erences

Documents

Report Icwcs