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  • 1. Wood, Mark 'Cell@lert' via Cell Broadcast Cell@lert, a new idea in mass public warning for disaster mitigation - 'It's about time'. Mark Wood Hon Sec, Cellular Emergency Alert Systems Association (CEASa) ABSTRACT In this document we describe the mass public warning system that works via 'Cell Broadcasting'. It can send millions of short text messages, to a specific geographic area, and do this even when the network is in full overload. Furthermore the system does not itself cause any load of its own. It can enable authorites to reach millions of citizens directly, rather than through the media. However there are many technical and political problems to be solved if we want the result to be a truly practical international system. The Cellular Emergency Alert Systems Association (CEASa) has been working for 10 years to provide a fully integrated solution. This year, for the first time, we can expect to see practical working systems deployed in many countries. Cell@lert system Components Cel@lert Network X Direct Cell@lert Via web browser HTML Cell Broadcast Cell Broadcast Centre Advanced Broker Server BMSP Broadcast CAP Commander Network Y BMSP Cell BMRP Broadcast Cell Broadcast Centre Reporter Fig1 The location of the Cell Broadcast Broker Server in the Network. Proceedings of the Second International ISCRAM Conference (Eds. B. Carle and B. Van de Walle),Brussels, Belgium, April 2005 1
  • 2. Wood, Mark 'Cell@lert' via Cell Broadcast 1 An overview of Cell@lert. 1.1 Example It is late at night and a river level is rising to dangerous levels. The local police want to warn the population at risk, the people who live in the area likely to flood. However since it is night time, they are not watching their TVs or listening to the radio. How will we work out which people are in the area at risk and contact them all in a short time? If the community is protected by a Cell@lert service, they do have a chance. The senior police officer, or disaster manager, can go to the Cell@lert web site. Here he selects a map of the area in danger. By using the mouse, he can draw a warning box around the area in trouble. After defining the area, he can then type in a short text message indicating the nature of the danger and suggested actions. Such as ‘Flood warning in this area, protect property at low elevations”. The officer then needs to press the ‘Go’ button, and that’s it, he can then get on with planning the action required! Meantime the Cell@lert Broker has been sent the message. It checks that the person who proposed the message is indeed genuine and is working within his jurisdiction. If so it speeds the message to all the networks which cover that area, so that every citizen is protected no matter which service provider they have chosen. In about a minute, every mobile phone in the area is ringing to wake up the vulnerable population. They can read the message and decide to take action to reduce their danger. 1.2 Cell Broadcasting The secret of the success of Cell@lert, is the use of Cell Broadcasting. Cell broadcast messages can be employed in several ways when a number of cell phone users in a certain geographical area need the same urgent information. Such information may include text messages relating to emergency situations, and, for 3G cells and phones, pictures of wanted or missing persons or maps of areas to avoid and best escape routes. Cell broadcasting is an already existing function of cellular networks and is defined by the official standardisation bodies, such as GSM MoU, (GSM 03.41) UMTS, 3GPP/3GPP2 and IS95CDMA. Many networks have cell broadcast channels defined for their networks which are unused at present for lack of a suitable application. This is that application. Best of all, it still works in real disasters when overload has made other uses of the cellular system unworkable. Cell Broadcasting is not effected by overload and does not even make any overload problems of its own! Proceedings of the Second International ISCRAM Conference (Eds. B. Carle and B. Van de Walle),Brussels, Belgium, April 2005 2
  • 3. Wood, Mark 'Cell@lert' via Cell Broadcast There are several technical as well as political problems to solve to make this happen. 2 Political problems to solve The power of Cell Broadcasting, that of reaching millions of members of the public within minutes, means great responsibility for the operators of any service which uses Cell Broadcasting. To meet those responsibilities the Cell Broadcast Broker (CBB) has been developed. The people will want to have faith in the whole truth of the messages, they may be changing their whole life on the basis of what they see, perhaps getting the children out of school or changing their working plans for the day. Businesses would be affected by loss of trade if the area were suggested as one to be avoided, so the validity of the messages is most important to the citizens. Superior governmental authorities will need to be sure that the proper steps have been taken to ensure that the CBB users (that is message senders) who have access to the public with information, are indeed those who are bona fide authoritative sources of such information, and that their mandate is Pro Bono Publico, (in the public good). Furthermore, the network operators, (whose co-operation is vital to the success of the programme), will want assurances also. They will not want to be liable for any information which turns out to be false. They will want to protect the reputation of their network and the interest of their customers by ensuring that messages are indeed timely, pertinent and not seen as a nuisance by the people. Network operators have a lot of face to loose if trivial use of the system blunts the impact of the service. After all, the people can always churn to another network if they become dissatisfied. The same cannot be said of a police force! When dealing with the networks we must be respectful of this reality. So mesages are vetted by sofware in the Cell Broadcast Broker (CBB). It is not possible for computers to make decisions like that, only people can be that smart. The CBB strategy is one of decisions being made by human ‘Gatekeepers’, while their policies are faithfully administered by the operation of the Cell Broadcast Broker. No one can send a Cell Broadcast message unless the agreed rules have been followed. The CBB makes sure of that. However since the CBB software is checking the message, the message is not delayed and is passed in in seconds. 3 Technical Problems to solve There will probably be many operators covering the same area, at least two and up to eight in some cases (taking 3G licences into account). There is no co-ordination of cell planning between competing operators, so the Cell layouts and Cell_IDs of different networks will be very different. In addition, due to constant improvements in Cell coverage and capacity, the size and layout of the cells covering a geographical area can be highly dynamic. The Cell_IDs that were true for a town last month may not be true now due to cell splits or switch cut-overs. Proceedings of the Second International ISCRAM Conference (Eds. B. Carle and B. Van de Walle),Brussels, Belgium, April 2005 3
  • 4. Wood, Mark 'Cell@lert' via Cell Broadcast Also, many networks have a hierarchical cell structure system, with overlapping patterns of cells of different sizes, Umbrella Cells, Macro Cells, Overlaid cells, Micro Cells and Pico cells, and up to 8 layers of sub band structure in different frequency bands, (850-1900 or 900-1800-2Ghz) each having very different Cell_IDs and different base station spacing. The situation will get much more complex by the end of 2003, with the introduction of 3G GPRS, EDGE, CDMA2000, and UMTS. 3G cell broadcast messages will be much more capable, so different Cell_ID tables will be needed for a ‘plain text’ version of the broadcast than for a ‘multi-media’ version. 4 THE SOLUTION; THE CELL BROADCAST BROKER (CBB). All of this is much more complexity than the user, (such as a police officer) can possibly have the time to deal with. He will need a simple map with a 'mouse click' interface to define the geographical area to be covered. The rest will need to be invisible to the user. By having the user interact with the Cell Broadcast Broker over a web page, (via a Web Portal), loading of special client software is an unnecessary and expensive step. Almost any computer can use CBB without any modification at all. This option is called Cell@lert Direct. Alternatively, if the needs are more specific than a simple web based interface can handle, the Advanced Broadcast Controller (ABC) is needed. This third party application, can call on more, perhaps confidential information to define the broadcast area. In this way the confidential information never leaves the building. Cell broadcast messages are broadcast by the Cellular Network Operators on a per-cell basis over a cell broadcast channel. In order to make a cell broadcast message happen, a signal has to be sent to the cell broadcast centre. From here, to the Base Station Controllers (BSC), containing the message to be transmitted, and crucially, the 'Global' Cell_IDs of the cells in which the broadcast is to be made, along with some other data such as how often and when the message is to be broadcast. Importantly, Cellular operators guard the information about their cells (the cell data) with great care, as the information can be useful to a competitor. They may find the prospect of having this information on multiple unsecured servers to be unacceptable. The solution is to keep the cell data in a look up table in a ‘Cell Broadcast Centre’ at the Network operator’s office, listing the Cell_IDs of the cells, the Lat Long positions of their respective Radio Base Station sites and azimuth data for their sectors. This leads to per cell resolution, but for the first application this may be good enough considering the small size of modern cells, which are typically 1-3 Km across (about 2 miles). The cell data never leaves the Network’s office. 5 The Cell@alert System The Cell@lert System consists of five parts; • The Users Browser (at the disaster management office) • The Advanced Broadcast Commander. (at the disaster management office) • The Cell Broadcast Broker (at a secure location). Proceedings of the Second International ISCRAM Conference (Eds. B. Carle and B. Van de Walle),Brussels, Belgium, April 2005 4
  • 5. Wood, Mark 'Cell@lert' via Cell Broadcast • The Cell Broadcast centre (At the network operations centre). • The Cell Broadcast Reporter (At the disaster management office). At the Disaster Management Office, or police control room, the officer who will create and propose the message needs either a browser such as Internet Explorer, with web access, (Cell@lert Direct), or the Advance Broadcast Commander (If using ABC). The Cell Broadcast Broker (CBB) would be responsible for ensuring the authenticity of the message and the authority of the sender to create such a message. Human ‘Gatekeepers’ will set the ‘User profile’ in the ‘Administration Subsystem’ to control sender rights and privilege. The signal from the end user’s workstation, for example, at the police station, to the CBB at CEASA, would only indicate the geographical area to be covered, plus the message. CBB then sends the broadcast request signal to the ‘Cell Broadcast Centre’ at the office of each network operator concerned. At the network operator’s office, there is a ‘Cell Broadcast Centre (CBC)’ server, which collates the cell Lat-Long data from the CBB with the CellID data, for that network. The table is derived as a standard report in plain text form, as is regularly done as a ‘report’ from the Cell Planning tool or Network Management tool. The Radio Network Engineering department of each network already have this information on file in the office and keep it up to date with regular reports. All that is needed is a copy of this report. None of the operators would have access to each others cell data, neither is it necessary to update hundreds of remote data bases with the cell data tables. Transmission between CBB and CBC could be achieved with standard 'commercial off the shelf’ TCP/ IP secure tunnelling protocols, featuring security and authentication. Alternative secure transmission via satellite is also possible. 6 Cell Broadcast reporter At the disaster management office, or control room, the officer may wish to review what other messages are being broadcast in the area before deciding on action of his own. The Cell Broadcast Reporter can show a real time report as to what messages are already in progress in the area. 7 The business model The CBB service could be purchased on a subscription basis by the users, such as the Police Force or River Authority. This would finance the operation of the broker service. Or there could be surcharges on a per request basis. The Cellular network operators could levy charges to CEASA on a ‘Per-message-per-cell’ basis, or on a basis as to what size of area has been covered. Charging on a basis of population density covered is also possible. CEASA CBB would be acting as the billing gateway broker as the CBB knows the geographical coverage requested by the user and is also capable of calculating population density if so desired. CEASA would also manage customer account management, authentication, security and applying of Proceedings of the Second International ISCRAM Conference (Eds. B. Carle and B. Van de Walle),Brussels, Belgium, April 2005 5
  • 6. Wood, Mark 'Cell@lert' via Cell Broadcast any restriction on the customer, such as what jurisdiction may be addressed. 8 Ceasa international. There are issues to solve in the international sphere. For example, Cell Broadcast messages can be separated from each other by the use of one of 65000 codes. There need to be codes based on language, so that people can see messages in their own language if they live in a multi-lingual country. This needs to be agreed on an international basis. This will also mean that tourists abroad will be protected by messages, from the local authorities, but in their own language. Also in the case of international events such as tsunamis, a common signalling system can send messages across national boundries provided multilateral agreements exist. End Proceedings of the Second International ISCRAM Conference (Eds. B. Carle and B. Van de Walle),Brussels, Belgium, April 2005 6