A MANET Emergency Communication for Catastrophic Natural Disasters

 

When stricken by a catastrophic natural disaster, emergency rescue operation is very critical to many lives. Many people trapped in the disastrous areas under collapsed buildings or landslides may have a large chance to survive if they are rescued in "Golden 72 Hours". People evacuated from their home jammed in highways or dome shelters need to communicate to each other for various reasons. However, communication systems were usually down due to various reasons. The loss of communication systems made the rescue operation extremely difficult. Many people died before they got a chance to be rescued. This paper analyzes the causes that paralyzed the entire communication systems in Jiji Earthquake and proposes a MANET based emergency communication and information system that can support a large number of rescue volunteers under catastrophic natural disasters.

CHALLENGES AND SYSTEM

Impact of Communication System Crash

 

The impact of communication system crash to the Jiji Earthquake will be presented in this section. Many people trapped in the disastrous areas under collapsed buildings or landslides may have large  chance to survive if they are rescued in 72 hours, called Golden 72 Hour. The loss of communication systems and information system created a big impact to the efficiency of rescue operation.

•  In a catastrophic disaster, regular rescue teams including trained professional rescue squads, police, army, and fire fighters were far from sufficient for the emergency rescue mission.

• Transportation system was paralyzed not only by broken bridges and roads, but also by a large number of disorganized voluntary rescue vehicles

• A large volume of rescue and relief resources were misplaced because the assessment of disasters distribution is virtually blind and inaccurate in the early hours even days after a big quake.

•  Trained and skill-specific professional rescue squads were misplaced to wrong spots

Causes that Crashed Communication

Systems

To many people's surprise, cellular mobile communication systems that were thought highly dependable in emergency were completely wiped out in many cases. Followings are parts of causes we found in Jiji Earthquake:  

• Base stations were crashed.

• Trunks connecting base stations to MSCs were broken almost everywhere, especially broken roads and bridges

•  Backup power generators were out because of fuel exhausted.

•   Critical hardware equipments were down because cooling tower fell down or cooling pipes were broken.

Environmental Constraints and System

Requirements

Following are the constraints and requirements for an emergency communication system that can support a voluntary rescue operation for a catastrophic disaster.

• Outgoing link is either not available or very limited.

• Server is probably not available.

• All Internet based services, such as Skype, are not available, because of no Internet access.

• There is a very stringent time constraint that volunteers are not able to use those devices that have a complicated user interface. In other words, user interface must be very simple.

Available Options of Emergency

Communication Systems

There are few options for emergency communication systems

• Walkie-Talkie Perhaps Walkie-Talkie is the most convenient and reliable communication system for emergency. However, the popularity of Walkie-Talkie in many countries is far less than notebook PCs.

•    Emergency Mobile Communication Systems Various equipment vendors are offering emergency mobile communication systems to stop its momentum yet.

MANET based P2Pnet

To construct a MANET based group communication system to support emergency communication and information network, called P2Pnet. Using P2P communication technologies, a P2Pnet is able to support Walkie-Talkie-like communication, Push-to-Talk, VoIP, and network information systems for emergency usage. Compared with other options, no extra hardware cost is needed.

MANET Based P2Pnet

System Architecture

P2Pnet is a server less peer-to-peer communication network based on MANET to support temporary group communication and information network.  P2Pnet is a serverless peer-to-peer communication network based on MANET to support temporary group communication and information network. As depicted in Fig, some nodes may have satellite communication capability performing gatewayfunctions so that all other nodes can access Internet through gateways if they are available. On top of MANET, there is a layer of peer-to-peer communication service to support higher level services such as Walkie-Talkie, Push-to-Talk, and VoIP communications.

  

Three basic communication modes are supported as followings:

• Uncontrolled Single-Hop Group Communication Network (U1Net) Each node can broadcast data to neighboring nodes in one-hop distance.

•  Uncontrolled K-Hop Group Communication Network Each node can broadcast data to neighboring nodes in K-hop distance. No authorization will be enforced. This mode can support long range Walkie-Talkie-like communications.

• Controlled K-Hop Group Communication Network  This is a more advanced mode and can support unicast type services such as VoIP. 

The most important lessons we learned from numerous disasters are that mobile communication system is vulnerable and the loss of communication system may have a catastrophic consequence. This paper analyzes the causes that paralyzed the entire communication systems in Jiji Earthquake and proposes a P2Pnet that uses notebook PCs to construct a MANET based emergency communication and information system. Brief system requirements and system design are presented. A prototype of Disastrous Earthquake Rescue Information System is presented. Finally, a P2Pnet prototype was tested in and English mobile learning class. The technical aspects of experiment results are presented.

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Quantum mechanics

Quantum mechanics is the body of scientific principles that explains the behaviour of matter and its interactions with energy on the scale of atoms and subatomic particles and how these phenomena could be related to everyday.
Classical physics explains matter and energy at the macroscopic level of the scale familiar to human experience, including the behaviour of astronomical bodies. It remains the key to measurement for much of modern science and technology. 

Mathematical formulations
In the mathematically rigorous formulation of quantum mechanics developed by Paul Dirac David Hilbert, John von Neumann,and Hermann Weyl the possible states of a quantum mechanical system are represented by unit vectors (called "state vectors"). Formally, these reside in a complex separable Hilbert space - variously called the "state space" or the "associated Hilbert space" of the system - that is well defined up to a complex number of norm 1 (the phase factor).

Mathematically equivalent formulations of quantum mechanics
There are numerous mathematically equivalent formulations of quantum mechanics. One of the oldest and most commonly used formulations is the "transformation theory" proposed by the late Cambridge theoretical physicist Paul Dirac, which unifies and generalizes the two earliest formulations of quantum mechanics—matrix mechanics and wave mechanics. 

Interactions with other scientific theories
The rules of quantum mechanics are fundamental. They assert that the state space of a system is a Hilbert space, and that observables of that system are Hermitian operators acting on that space—although they do not tell us which Hilbert space or which operators. This "high energy" limit is known as the classical or correspondence limit

1.The standard model
The most developed quantum theory to date is known as the "standard model", and is considered to be the most accurate physical theory ever created. It has been proved to be valid to a very high precision. 

2. Weird and spooky
Some of the phenomena of quantum mechanics, such as entanglement were described by Albert Einstein as "spooky" because, at the sub-atomic level, physics as we think we know it breaks down and becomes almost incomprehensible

3.Core principles
There are a few basic core principles for understanding quantum mechanics and the supposedly spooky oddness that goes on at the level of atoms. It is very important to remember one key thing: quantum mechanics is not classical mechanics. 


The Photoelectric Effect
In the late nineteenth century, James Clerk Maxwell formulated a theory of electromagnetism that described a wide range of electrical phenomena, and in particular described light as an electromagnetic wave. Despite the success of this theory, the early twentieth century found it unable to describe certain aspects of the photoelectric effect.

Quantisation of energy
Prior to quantum theory, energy was thought of as necessarily analogue; taking any value indiscriminately and acting as a smooth transition. In the macroscopic world, this observation remains fairly true. Like a hosepipe that can deliver whatever amount of water you like by turning the tap in small amounts.

Particle-wave duality
Classical mechanics treats particles and waves as different things. A particle is a point, a speck with mass and an exact location. A wave is a little more abstract but it has wavelength - it's spread out, with frequency and speed. In quantum mechanics there is no distinction. Particles can be waves and waves can be particles - although really they're something else entirely with some, but not all, of the properties of both. We've evolved in a macroscopic world where we can see a distinction, but there isn't in the quantum world.

Uncertainty
With the wave-like nature of quantum mechanics established, problems began to arise in figuring out the location of particles. Waves do not have a specific location; they're spread out over an area and aren't described the same way as particles. Thus the "uncertainty principle" was established; in short it means you cannot know the location and momentum of a particle to the same degree of accuracy. 

Interpretations
There are many attempts at intuitive interpretations of quantum mechanics, and a minor industry of physicists coming up with them. These attempt to come up with an intuitive framework to explain the equations - essentially, trying to get them to "make sense" because, frankly, they really don't. 

Copenhagen interpretation
The Copenhagen interpretation, favoured by quantum mechanical pioneer Neils Bohr, envisages that the wavelike behaviour of particles "collapses" upon observation. It proposes that superpositions of states should be taken extremely literally and that a wavefunction is nothing more than an abstract concept that just reflects our uncertainty and lack of knowledge prior to an observation. 

Conscious observation
"Observation," in the sense of the Copenhagen interpretation is really just short-hand for any form of interaction with a quantum system. There are some, however, that seem to take it as requiring conscious observation, i.e., observation by a human mind. This is highlighted in the intentional absurdity of Schrödinger's cat experiment, where the cat and the detector itself act as "observers."

Quantum woo
Quantum physics is a difficult subject and people without science degrees are rarely expected to understand it — even those with the degrees are usually expected to have a working knowledge and not a full appreciation of every aspect of it. Its difficulty is further increased by the fact that, in many cases, there really are no decent lay explanations of how it works, so more accurate and nuanced explanations are lacking in popular science. 

Quantum consciousness
Scientists have some partial understanding of quantum physics but frequently disagree with each other while ordinary people are regularly mystified. Similarly the reason for consciousness is, given current scientific knowledge, impossible to understand.

Applications:
Quantum mechanics had enormous success in explaining many of the features of our world. Quantum mechanics is often the only tool available that can reveal the individual behaviors of the subatomic particles that make up all forms of matter (electrons, protons, neutrons, photons, and others). 

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cellular network

A cellular network or mobile network is a radio network  is a radio network distributed over land areas called cells, each served by at least one fixed-location transceiver, known as a cell site or base station. In a cellular network, each cell uses a different set of frequencies from neighboring cells, to avoid interference and provide guaranteed bandwidth within each cell.

When joined together these cells provide radio coverage over a wide geographic area. This enables a large number of portable transceivers (e.g., mobile phones, pagers, etc.) to communicate with each other and with fixed transceivers and telephones anywhere in the network, via base stations, even if some of the transceivers are moving through more than one cell during transmission.

Cellular networks offer a number of advantages over alternative solutions:

•        flexible enough to use the features and functions of almost all public and private networks

•        increased capacity

•        reduced power use

•        larger coverage area

•        reduced interference from other signals

 Concept

In a cellular radio system, a land area to be supplied with radio service is divided into regular shaped cells, which can be hexagonal, square, circular or some other regular shapes, although hexagonal cells are conventional. Each of these cells is assigned multiple frequencies (f1 – f6) which have corresponding radio base stations. The group of frequencies can be reused in other cells, provided that the same frequencies are not reused in adjacent neighboring cells as that would cause co-channel interference.

The increased capacity in a cellular network, compared with a network with a single transmitter, comes from the fact that the same radio frequency can be reused in a different area for a completely different transmission. If there is a single plain transmitter, only one transmission can be used on any given frequency. Unfortunately, there is inevitably some level of interference from the signal from the other cells which use the same frequency. This means that, in a standard FDMA system, there must be at least a one cell gap between cells which reuse the same frequency. In the simple case of the taxi company, each radio had a manually operated channel selector knob to tune to different frequencies. As the drivers moved around, they would change from channel to channel. The drivers knew which frequency covered approximately what area. When they did not receive a signal from the transmitter, they would try other channels until they found one that worked. The taxi drivers would only speak one at a time, when invited by the base station operator (this is, in a sense, time division multiple access (TDMA)).

Cell Signal Encoding

To distinguish signals from several different transmitters, frequency division multiple access (FDMA) and code division multiple access (CDMA) were developed.

With FDMA, the transmitting and receiving frequencies used in each cell are different from the frequencies used in each neighbouring cell. In a simple taxi system, the taxi driver manually tuned to a frequency of a chosen cell to obtain a strong signal and to avoid interference from signals from other cells.

The principle of CDMA is more complex, but achieves the same result; the distributed transceivers can select one cell and listen to it.

Other available methods of multiplexing such as polarization division multiple access (PDMA) and time division multiple access (TDMA) cannot be used to separate signals from one cell to the next since the effects of both vary with position and this would make signal separation practically impossible. Time division multiple access, however, is used in combination with either FDMA or CDMA in a number of systems to give multiple channels within the coverage area of a single cell.

Cellular Data Usage

Push Notifications

Some applications from the App Store use the Apple Push Notification service to alert you of new data. Applications that rely extensively on push notifications (such as instant messaging applications) will consume data. To disable push notifications, go to Settings > Notifications and set Notifications to Off. Note that this does not prevent new data from being received when the application is opened. Also, the Notifications setting will not be visible if you do not have any applications installed that support push notifications.

Push email and over-the-air syncing

Applications such as Mail can be set to fetch data wirelessly at specific intervals. The more frequently email or other data is fetched, the faster data is consumed. To fetch new data manually, from the Home screen choose Settings > Mail, Contacts, Calendars > Fetch New Data and tap Manually. To increase the fetch interval, go to Settings > Mail, Contacts, Calendars > Fetch New Data and tap Hourly. Note that this is a global setting and applies to all applications that do not support push services.

Operation Of The Cellular Phone

When the mobile unit is active (i.e. when a mobile phone is switched on), it registers with the appropriate BS , depending on its location, and its cell position is stored at the responsible MSC. When a call is set-up (when a user makes a call), the base station monitors the quality of the signal for the duration of the call, and reports that to the controlling MSC, which in turn makes decisions concerning the routing of the call. When a cellular phone moves from one cell to the other, the BS will detect this from the signal power and inform the MSC of that. The MSC will then switch the control of the call to the BS of the new cell, where the phone is located. This is called handover . It normally takes up to 400ms, which is not noticeable for voice transmission.

A cellular phone user can only use his/her mobile within the covered area of the network. Roaming is the capacity of a cellular phone, registered on one system, to be able to enter and use other systems. Those other systems must be compatible to enable roaming (i.e. they must have the same type of networks). In Europe, the standard cellular network is called GSM (Global System for Mobile Communication). Incoming calls to GSM[8] users are routed to them, irrespective of where they are, as long as they are within Europe.

The benefits of Microcellular systems

•        Interference reduced (compared to decreasing the cell size)

•        Handovers reduced (also compared to decreasing the cell size) since the microcells within the cell operate at the same frequency; no handover occurs when the mobile unit moves between the microcells

•        Size of the zone apparatus. The zone site equipment are small, so the can be mounted on the side of a building of on poles.

•        Increased system capacity. The microcell is an intelligent cell. The new microcell knows where to locate the mobile unit in a particular zone of the cell and deliver the power to that zone. Since the signal power is reduced, the microcells can be closer and therefore increase capacity. However, in microcellular system, the transmitted power to a mobile phone within a microcell has to be precise; too much power results in interference between microcells, while too little power and the signal might not reach the mobile phone.

This is a drawback of microcellular systems, since a change in the surrounding (a new building, say, within a microcell) will require a change of the transmission power.

Multiple Access Systems

In digital cellular networks, Multiple access systems  are used to allow simultaneous users to share the same channel within a cell. The common methods are time division multiple access (TDMA) and frequency division multiple access (FDMA).

In TDMA, the bandwidth allocated for the channel is divided into time slots - the number of slots depends on the system. Each user is then allocated a slot, and hence multiple users share the same frequency but at different times.

In FDMA, the channel is divided into frequency bands, and each user is allocated a frequency band.

 A  New Technology

Due to the rapid growth in the cellular communication industry, there is an increased need for greater system capacity. Code division multiple access is the new technology, and it does not need a cellular structure.

CDMA is a 'spread spectrum' technology; it spreads the information contained in a particular signal over the entire bandwidth allocated for the mobile communication. With CDMA, unique digital codes, rather than radio frequencies or channels, are used to differentiate the different signals. These codes are shared by both the transmitter and receiver; and hence the receiver (the mobile phone) receives all the signals but can only recognise the one with the same codes.

CDMA has many advantages over the existing cellular systems

•        Increases capacity and improves quality of the signal.

•        Simplified system planning through the use of the same frequency all over the covered area.

•        Enhanced privacy

However, CDMA can only be used for digital transmission, unlike the cellular system. This makes the move towards CDMA in some countries, which do not use the digital system, a distant future.

The Future

Currently, there are different standards of cellular systems in different parts of the world; the major ones are the GSM in Europe, and the PCS in North America. Roaming is not possible between these two systems. The next step would be to have duel-mode phones which could operate in the two different systems at the touch of a button. Having one global cellular communication system is ideal, but will take a while, since it will require altering one system's hardward (which costs a lot of money!).

Since the "information age" and due to the rapid growth of the cellular system, one could predict that in the very near future, everyone will have a portable communication terminal, which is small in size, fast in accessing the internet and transmit/receive data, cheaper, and could virtually be used from anywhere in the system.  

Finally, celluar networks will soon be replaced by the spread specturm technology; this move has already began in some parts of the world and the rest will sure to follow.

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