Chapter 1. Introduction
1.4. System Requirements for RDN
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withdrawn.
Figure 1.4. Vulnerable points of cellular network
1.4. System Requirements for RDN
On the basis of our firsthand experience obtained in the 921 Chi-Chi Earthquake and extensive research over the past decade [14,13,17,23,42]. We summarized the environmental constraints in the disaster areas are described as follows, (1) large number of disorganized non-professional voluntary responders and victims, (2) transportation system paralyzed, (3) time is running out, (4) hectic/chaotic usage environment, and (5) very limited deployment funding due to little commercial incentive.
We also summarized a set of communication requirements that must be addressed when
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constructing and operating a communication network for first responders. These requirements are categorized into two sets: user end and operator end.
User End Requirements
Popularity: In large-scale disasters, numerous volunteers must be mobilized to work on rescue and relief operations. In addition, people in the disaster area—including victims—may have extensive communication requirements. Therefore, several user terminals are necessary for a RDN. Because of the rareness of terminals, most common emergency communication networks, such as satellite systems, trunking radios, and amateur radios, can only be used by specific groups; most victims and volunteer disaster responders cannot access these communication networks. Moreover, users must be trained before using the terminals for trunking radio and amateur radio; hence, these systems can only be employed by professional disaster response squads.
Usability: A RDN should provide task-oriented communication services and support mobility, as well as have adequate service quality. Furthermore, RDN handsets should be user-friendly, durable, and not require a long training period, and task-oriented communication services should include both ordinary and group communication services. Finally, because disaster responders may have to move frequently, the mobility of user terminals is crucial.
Operator End Requirements
Practicality: Practicality is the essential operator end requirement, and includes low
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deployment costs, easy acquisition of equipment, and rapid deployment. Although RDNs are essential to disaster response operation, they do not generate profit and the occasions for their use are limited. A commercial cell phone operator may not be justified in making a large investment in the design and development of a large-scale RDN; therefore, a RDN must have low development costs to be practical.
Because of obstacles created by terrain and paralyzed transportation systems, transporting external aid to disaster areas is usually difficult. In many cases, helicopters may be the only vehicle that can access disaster areas in the early hours or days of a large-scale disaster. Hence, the size and weight of RDN equipment should be suitable for air transportation. For instance, mobile base stations (called “cells-on-wheels”), which have a base station with satellite backhaul and are carried by a truck, may be too heavy to be carried by a helicopter; hence, this equipment may be useless.
Finally, survival rates are highly dependent on rescue speed. If trapped victims are rescued quickly, their chances of survival are considerably higher; thus, RDNs should be deployed as swiftly as possible. Furthermore, cell phone operators must work at full capacity to restore their systems. The value of a “band-aid” style RDN is substantially lower once any cell phone is recovered. Therefore, a RDN must be rapidly deployable.
Capacity: A RDN must have sufficient capacity to satisfy the communication demands of large numbers of victims and disaster responders—both professional and voluntary—within stricken areas, as well as limited incoming and outgoing calls to external institutions.
Furthermore, a RDN should have the ability to resist the burst of call requests, to prevent it from crashing.
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Sustainability: A RDN should not only be deployed as quickly as possible but should also continuously operate until the public communication network is recovered, which may take several days or even weeks. If nonstop operation is impossible, it should be rapidly recoverable once it has crashed.
Figure 1.5. 7-Ability of rapidly deployable network
Adaptability: Similar to a battle field, the situation in a disaster area may constantly change due to factors such as aftershocks, fires, and the progress of disaster response. Therefore, a RDN must be able to adapt to the changing environment either manually or automatically.
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Operability: Similar to any production system, a RDN must have an operation, administration, and maintenance function to remain in operation.
The system requirements are summarized as 7-ability of rapidly deployable network and showed in Fig. 1.5.
The layout of this dissertation is as follows. Chapter 2 introduces the traditional communication systems for disaster response and current available solutions with a comparative evaluation against the 7-ability requirement. We design a large-scale, low cost and rapidly deployable communication system called Contingency Cellular Network (CCN) to support large number of disorganized users. Chapter 3 discusses the design philosophy, system architecture and research issues of CCN. Chapter 4 formulates the network design problems of CCN with a comprehensive mathematic model. A binary linear algorithm and a topology design heuristic algorithm are proposed to solve the problem. Effectiveness and efficiency of the algorithms are verified by simulation. Chapter 5 formulates the deployment scheduling problem. Two heuristic algorithms are proposed and discussed. Chapter 6 formulates the bandwidth allocation problem and proposes a solution. Finally, Chapter 7 concludes this dissertation with a discussion of the contribution of our research works.
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