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This project has started by giving an introduction to the mobile technology. This included mobile generations, the past, current, and future ones. Also, the programming languages that are used to build mobile applications were introduced, having the focus on the main programming language that was used in this project, which is the J2ME, from Sun Microsystems. Then, the focus moved to the area of communication signals aspects between mobiles itself and between mobiles and towers. After that, the research problem was highlighted, which is the coverage problems in mobiles. Moreover, the current existing solutions were presented to show the current phases of research and development that have been made in this area. The proposed solution is the relay technology, which was first introduced as a general concept in chapter four, and proposed in details in the following chapter. A prototype of the designed solution was covered in great details in the sixth chapter.
To conclude the main facts out of this work, let us start with the research problem itself. There are many cases in which mobile devices lose coverage with towers, some reasons are technical, which are related to the mobile communication with the tower, and some reasons are non-technical, which are related to physical blockages between mobiles and BTS towers. However, we live in our daily lives; we are experiencing this kind of problem of being in a place where it is considered as a block area where the BTS signals cannot provide signals to mobiles. The traditional approach of solving this problem is by adding more BTS towers in block areas to provide the sufficient signals to mobile devices. This explains the method of competition between mobile companies, which are competing each other by proving more BTS and BSC towers. The more towers a mobile company has in an area, the wider coverage can be obtained to mobile devices, which consequently mean good business. However, keeping in mind that building one BTS tower consists approximately two million dollars, this should be a good reason to think of an alternative solution to tackle this problem of coverage, without adding extra BTS stations, especially in growing cities where buildings are getting taller with time.
The concept of using relay technology has not been suggested as an alternative solution to the coverage problem, because the traditional understandings of using relay technology in mobiles means abstracting the entire BTS station in a tiny mobile device. This absolutely sounds unrealistic and with no sense, from the technical point of view and obviously it would be cost effective, even if it was assumingly possible. However, this can be discussed from a totally different point of view. For instance, the Bluetooth technology in mobile devices is based on special low-power signals. Bluetooth is used to transfer data between mobiles in a synchronous real-time communication approach. To understand the concept of relay technology as a solution to solve the coverage problems, let us assume that we will use the Bluetooth signals with a special protocol, assumingly called relay protocol, which is able to send commands between mobile connected in Bluetooth communication signal, to run a particular application on mobiles. This sounds achievable and practical, but in requires special software to enable handling the communication. If we have two mobiles connected in Bluetooth communication, and the first mobile needs to run an application on the second mobile, then why it would not be possible to run the application that is responsible for sending a message or making a call? This sounds also applicable and practical as well. This is exactly the idea of using relay technology to provide coverage to mobiles in block areas.
Therefore, this project has provided the software side of the concept of using the relay technology to provide coverage to a mobile that cannot connect to a BTS station. The software simulation used the SIP protocol to make a connection between the relay mobile and the mobile that will be relayed. In the proposal of this project (chapter five), there were three types of communications have been suggested. These types are the asynchronous communication approach, the synchronous communication approach, and the relayed communication approach. The asynchronous communication approach is responsible for one-off data package transfer, such as sending an SMS or an MMS message. The synchronous communication approach is responsible for providing a continuous real-time connection for mobiles, such as making a call or surfing the web. Finally, the relayed communication approach is when a mobile has no coverage but would like to be discovered by other mobiles. The relay mobile communicates with BTS towers and relayed mobiles in a bidirectional communication manner, allowing data transfer from and to relayed mobiles as if they were covered.
To prove this concept, a complete communication session in asynchronous approach was developed, and a text message was successfully sent from a mobile application that cannot connect to a BTS station application, through a relay mobile. The developed system proved that the software of the proposed solution is realistic and undoubtfully possible. The main concept of the relay technology is the usage of packet headers, which allow mobile devices, whether they are relay mobiles or relayed mobiles, as well as the mobile stations, such as BTS, BSC and MSC stations, to understand the communication between each other. A basic set of headers was used to allow the developed application to work. However, in actual scenario, more sophisticated and dedicated header can be used to specifically describe the communication between different nodes in mobile networks.
7.2 Issues and Concerns
Although the relay technology promises to provide a quite interesting alternative solution to adding extra high expensive BTS stations to solve the problem of coverage in mobile systems, there are some issues and concerns can be highlighted to analyze the proposed solution in more realistic manner. The concerns can be looked at from the following views:
Mobile Companies (Providers), and,
Relay Mobile in Multiple Services.
The following will shed the light on each of these issues and concerns, with some details that explains why these issues should be considered when applying the relay technology in mobile systems.
7.2.1 Relay Signal
As it was explained in the proposal chapter (chapter five), the relay signal has not been discovered yet, though, the features of this signal can be summarized in the following:
It should provide a communication signal that allows mobiles to communicate with each other.
It is able to scan a specific area around the mobile for available mobile devices that are relay-enabled.
It provides the possibility to either manually or automatically connect to any of the mobile devices that are discovered in the scan, which have coverage with a mobile network.
It applies a set of security policies to secure the established communication channel between the two mobiles. These policies ensure checking the authentication, authorization, and encryption of the information during the transaction process.
Meanwhile, as long as this signal is not present, the Bluetooth signals can be used as a short-range relay signal. Keeping in mind that with Bluetooth signals, a coverage area of 100 meter radius circled area can be provided with advanced Bluetooth signals. This looks suitable for a wide range of coverage problem situations, such as in basements and many other cases of block area. This can be a good starting point to apply the relay technology until the suitable wide range relay signals become available. Theoretically, there is no typical range can be specified for relay signals, and can be left to RF engineers and electronic engineers to investigate more features about the proposed relay signal.
One of the main issues to be considered when applying the relay technology in mobiles is the security issue. Along with the need of a relay signal, there is also a crucial need to design special software that will handle the security side of the communication between mobile devices in relay mode. This can be achieved by implementing a security protocol that can manage and control the handshaking process of the data packets that are transferred between mobiles. This security protocol should consider applying the most secure encryption methods to maintain the communication while data being transferred. There are many encryption algorithms and methods, and they are not difficult to use, and they can be adopted from those which are used in wireless technology. There is a wide range of security threats can be experienced in the relay technology. Threats can be classified into internal threats and external threats. The internal threats are the possible threats that can lie on the mobile device, whether it was a relay mobile or a relayed mobile, such as viruses and other types of malicious mobile micros. The external threats refer to all possible threats that can occur while there is a communication established between a relay mobile and a relayed mobile. The key to overcome these challenges is to have a proper security protocol that ensures that all data packets are safe in its journey between mobile devices in the relay mode. The higher encryption standards applied the better in terms of securing all transferred data. It is crucial to prepare a robust security plan against attacks such as sniffers and session high-jacking, as well as the misuse of the communication between mobile devices in the relay mode.
The issue of privacy rises in the relay mobile while in action. The relay mobile is used like a bridge between a mobile device that is in need of having coverage and a BTS station. As mentioned before, there are two possible interaction scenarios of communication from a relayed mobile to a relay mobile: asynchronous and synchronous communication approaches. These two approaches are also applied from the relay mobile to the relayed mobile when the relayed mobile is in the relayed mode of communication. The issue that should be highly considered is how to ensure that the data packets of the relayed mobile that will be transferred to and from the relay mobile will not be sniffed at. The concern goes higher if there is a synchronous communication provided by a relay mobile to a relayed mobile when the last is willing to achieve a mobile commerce tasks (referred to as m-commerce). In m-commerce, there will be a secured session established from the website and the mobile that is willing to do online shopping using mobile devices. This issue can be solved by using advanced encryption algorithms, with the use of public and private keys. This sounds like adding more complication to the providers of m-commerce web applications. However, it should be kept in mind that adding any new technology has also its advantages, considering that having such a remarkable solution to the coverage problem will increase the accessibility of m-commerce web applications will reduce the effort that have to be paid to increase the security in mobile devices to ensure privacy of transferred information. The same concern does exist when citizens try to access some governmental web application using mobile devices, which is called the m-government. However, as discussed above in terms on m-commerce, increasing the resources of making the citizens more convenient to access the government web application through their mobile devices, will make the m-government more accessible, and consequently, more successful. As a conclusion, the relay mobile has the right to accept to decline serving as a relay mobile when it is discovered in the relay search that is done by a mobile requires coverage, exactly as in Bluetooth communication. However, once the mobile agrees to sever as a relay mobile, it will have no privilege over the data packets that are transferred through it, to ensure that privacy is maintained in relay mobiles.
7.2.4 Mobile Companies (Providers)
In the developed simulation software, we assumed that the communication will be managed and controlled by the BTS application. We have abstracted the BTS, BSC, and MSC stations in one application. However, it is known that the BTS and BSC stations function as transceivers and there is no actual processing of data will occur in them. The MSC station in actual cases belongs to one mobile company. Moreover, mobile companies can have more than one MSC station to handle the wide number of the company's customers. Each MSC station is connected to all other MSC station of the same company, as well as it is connected all other MSC stations of other companies. This scenario is similar to the concept of Internet Service Providers (ISP), which collaborates with each other to provide the universal mobile networks as it is known today. For instance, when a call is made from a mobile customer of Orange Company to a mobile customer of O2 Company, the MSC stations of Orange connect its customer to the MSC stations of O2 and from there to the destination O2 mobile.
However, there are many aspects should be considered when applying the relay concept. For instance, any mobile, whether it was functioning as a relayed mobile or as a relay mobile, has to be connected to a mobile company. The question that will arise is what if the relay mobile belongs to a company and the relayed mobile belongs to another company? For such cases, when the relay mobile and the relayed mobile do not belong to the same company, or in other words, they are not customers of the same provider, there should be a special protocol to be agreed on by mobile companies to facilitate the use of the relay technology in a convenience way. Therefore, for instance if a mobile customer of Orange (with a free minutes contract) would like to use a mobile of O2 Company (with a pay-as-you-go SIM card) as a relay mobile, the O2 mobile will not be charged by its company (the O2 Company), instead, O2 Company will understand that its customer is willing to serve as a relay mobile for an Orange customer. Furthermore, the MSC stations of the O2 Company will contact Orange MSC station to check the contract and credentials of Orange's customer to make this call for the desired destination. This process should be done immediately with no huge delay to ensure a reasonable quality of service in the relay technology. Finally, the kind of agreements and protocols between mobile companies is already done for a mobile application service called the Roaming service.
7.2.5 Relay Mobile in Multiple Services
There are several scenarios can be discussed regarding using the relay mobile to utilize the benefits of the obtained coverage for multiple services. One of the issues to be discussed here is the following: Can the relayed mobile work as a relay mobile for another mobile that needs to be relayed? This question highlights the possibility of using a chain of relay mobiles. When a mobile with no coverage runs the relay search, logically it should be possible to discover any mobile with relay-type coverage (relayed mobile). This means that a relayed mobile can serve as a relay mobile to other mobiles that need coverage. This scenario can be developed to the extent of having an unlimited chain of relay-relayed mobiles. This can be an extraordinary advantage of using the relay technology in mobile systems, especially in rural areas, forests, desserts, large cities with complex architectures of buildings, and in any areas that are practically difficult to establish a BTS station.
The other issue to be discussed here is how many relayed mobiles that one relay mobile can support? For instance, if a relayed mobile is making a call through a relay mobile in a synchronous communication mode, and while calling, there is an incoming call coming to the relayed mobile through the relay mobile, what would happen in this scenario? First, it has to be mentioned here that in the synchronous mode of communication, the relayed mobile is already in a relayed communication mode with the relay mobile. This is because there is an established synchronous continuous connection between the relay mobile and the relayed mobile. This means, there is a benefit was not mentioned before, which is it is possible to receive a call while a relayed mobile is in a call. Therefore, as in covered mobiles, the mobile user has the right to put the current call on hold and answers the new call, or the new call can be declined. Also, because of this, the relayed mobile is able to receive a message while being in a call. This is for one relayed mobile connected to a relay mobile. This means that there is a full support of bidirectional and multiple services on the same relayed mobile. However, is it possible for the relay mobile to serve as a relay mobile to more than one relayed mobile simultaneously? The answer evidently is yes. This is because, basically, a mobile when serving as a relay, it actually functions as a normal mobile that can call and receives a message in the same time, and from the other side, a mobile can make a call conference to more than one destination. It has become usual nowadays to make a call conference with multiple recipients. This feature indeed is a proof that a mobile can make more than one call at the same time. Consequently, this feature of establishing more than one connection with the BTS station from a mobile will be used in the relay mobile to serve more than one relayed mobile at the same time; in a simultaneous manner.
The last issue to be discussed is the following situation: what if the relayed mobile got coverage while it is connected to a relay mobile? Will it continue using the relay or it will switch immediately to the BTS signal? This situation is somehow similar to a similar situation occurs when a mobile that is connected to a certain BTS signal, and mobile user is moving (by a car, train, walk, etc) to an area that is covered by another BTS station. In such cases, there is a mechanism called: Hand Over, which is done automatically between BTS stations, which causes the mobile to automatically switch from the first BTS to the second one without noticing the handing over process that has occurred to its signal. The same scenario can be applied when a BTS signal becomes available for a relayed mobile; the relay software application can handle this hand-over process without making any inconvenience to the relayed mobile. In this case, with the aid of the relay software application, the relayed mobile will be called a covered mobile and will stay in a continuous connectivity to the mobile network. However, to criticize the hand-over process, it might be better to give the relayed mobile user the authority to be transferred from a relayed state to covered state. This would be crucial if the mobile user is doing m-commerce or m-government process that requires a session going necessary through the relay mobile.
7.3 Future Work
There are some interesting future work directions that can be drawn out of this work. These directions are a result of the promising relay technology that was proposed in this project. Firstly, this work can be extended to cover a complete simulation of a mobile network, including a BTS, BSC and MSC stations applications. Also, more than one mobile can be tested in the scenario. Moreover, in the developed system, there was only one relay mobile to be used. This can extended to have more than one relay mobile, and an application that simulates the searching facility on the Mobile application can also be simulated. Although the actual suggested search facility will be based on the relay signal, but building software simulation to the search mechanism would make the work looks more solid. If this can be simulated, then the extended design can also cover implementing some security encryption algorithms to test and evaluate the security side of the communication. This will make a more realistic scenario of the actual mobile network.
Furthermore, another direction of research can be made to implement and design simulation software to the functionality of mobile companies when their MSC collaborate to check whether a call can be made from a mobile that belongs to a different company than the one the relayed mobile belongs to. This will require having a database corresponding to the database available in MSC stations.
Another extension can be added to the achieved work in this project is to add more features in the Mobile application to use the three ways of the proposed communication approaches (asynchronous, synchronous, and relayed), because in this version of the project, only the asynchronous communication approach was used. Moreover, features like adding a voice toolkit to the Mobile application to make real calls between two Mobile applications or to make a voice call conference between more than one Mobile application.
Also, an interesting extension can be made to this project by using this version of the software to install it as a real application on some actual mobile devices, and to use Bluetooth signals as a relay signal. So, there will be two mobile devices want to send a file (a message) and there is a relay mobile and a BTS mobile. This will make a real implementation of the relay mobile using the Bluetooth signal. This would a serious and confident step towards applying the relay technology in real life but by using Bluetooth signals.
The final and most interesting future work that can be achieved after this work is to propose and implement a concept called: Relay Station. The typical situation to apply the relay station is in undergrounds stations and its trains, in addition to supermarkets with basements. Let us take the scenario of undergrounds, assumingly London undergrounds trains network. It is well known that there is no in-door coverage in London underground trains network. The relay station framework can be used to provide coverage for mobile users in the underground networks, whether they were waiting a train underneath the station or those who are already in trains. First, before explaining how the proposed relay station works, it has to be noted that there are many mobile users who are in essential need to be connected to a mobile network, either to make a call, to send a message, or send an email. This is one of the potential situations that can be mentioned to show how important it is to find a solution for the mobile coverage problem for customers who require to be connected all time to satisfy their business' needs. Therefore, the proposed relation station can be the optimum solution to overcome this problem. A relay station is a framework consists of a mobile devices and an internal mobile Access Point. The mobile device is fixed over ground in the station and it is always in covered mode. The access point will be fixed under ground to provide coverage for mobile users who are in the underground station or in the trains. The covered mobile device will work as a relay mobile for the access point. So, there is a continuous connection between the relay mobile and the access point. Therefore mobile users who are in the underground network can use the access point signal to obtain coverage. This will be an effective alterative solution to the tradition approach of overcoming this problem, which would require building a complete BTS station inside the underground train network. A simulation of this proposed idea of the relay station can be achieved as a masters or a PhD project, provided that a basic mobile internal access point is available for the student to work on to proof this concept. If this idea was successful in a prototype form, then it would be a very interesting idea to be applied in the real situation in London underground trains network, and it also could be applied in an international scale and in a variety of situations where it is required.