Bluetooth Remote Access to PC Using Mobile Devices
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Published: Thu, 08 Feb 2018
INTRODUCTION TO RESEARCH
Bluetooth is a wireless technology of the last decade, there has been a lot of research going on this technology all over the world. The Bluetooth was named after the 10th century Danish King Harald Blatand or Harold Bluetooth. King Blatand was influential in uniting militaristic factions in parts of what are now Norway, Sweden and Denmark – just as Bluetooth technology is designed to allow collaboration between differing industries such as computing, mobile phone and automotive markets. Bluetooth technology was the internal project of Ericssion, which was intended for providing short distance multiple links. Then it was collaborate with Intel in 1997, later the association with Nokia, IBM, Toshiba, Microsoft, Motorola, 3com etc to form a non profitable trade association Bluetooth Special Interest Group (SIG). The formed consortium adopted common code name to Bluetooth for their open source specification. Bluetooth uses 2.4 GHz frequency for transmitting the data at band rate of 1Mbps. In taking account of user’s point of view, there are three important features to Bluetooth. (Ali M Aljuaied 2001)
- It is wireless. When you got to client place, you need not have to worry about keeping track of cables to attach all of your components and you can design your application without wondering where all the wires will go.
- It is economical.
- You do not have to think about it. Bluetooth does not require any extraordinary skills to make it work. The devices find one way or another and pairs up a conversation without any user input at all.
Bluetooth technology is a standard and communications protocol which is designed for low power consumption, with a short range (power-class-dependent: 1 meter, 10 meters, 100 meters) based on low-cost transceiver microchips in each device. Bluetooth enabled devices tend to communicate with each other when they are in range. These devices use radio wave communications system, so that they do not have to be in line of sight with other and can even be in other rooms, as long as the received transmission is powerful enough. During the discovery process Bluetooth device transmits class type of device and the supported services of that class
Max permitted power
Table reference [www.bluetooth.com]
The popular Bluetooth applications are:
- Mobile phone and hands free headset.
- File transfer between Bluetooth enable devices using Obex application
- The places where traditionally used by IrDA in control equipment.
- In gaming equipments like play station.
- Used to connect the Dial up internet for PC.
1.2 AIMS AND OBJECTIVES OF RESEARCH:
The main research aim of the project is to develop Remote PC manager from mobile through Bluetooth and make it more efficient and reliable for future applications. The following are the research objectives:
- Developing user friendly software for remote management of PC through mobile using Bluetooth.
- Improvement of response time in the existing application.
- To solve the problem occurred in application during the connection and disconnection Process.
1.3 PAST WORKS:
There has been a vast amount of research carried out in Bluetooth related applications all over world of which is this PC remote mobile phone using Bluetooth application, but most of the applications that are made have been having problems related to response time, compatibility with specific mobile such as Nokia and Sony Ericsson, connection and disconnection. Hence, the next few lines will discuss about the background for developing PC remote.
Based on Blueshareware.com
The first beta type control 1.0 version using Nokia 6600
23 Feb. 2005
Then added applications related to audio and video player
7 march 2005
Then started to test the code on Sony Ericsson
6 Nov 2005
New GUI for phone has been developed with special soft keys
29 Jan 2006
After then they started to have better GUI by correct early problems and adding new applications releasing higher version
Bluetooth remote control 2.0
- The Open java script that allowed others to be modified
- They have added new PowerPoint application.
- It had some drawback such as application could not run in some mobiles and screen turn blank some times.
There has been a lot of modification and re-releases by solving problems like increasing the range of compactable mobile and correcting minor problems.
Bluetooth remote control 3.0
- Win AMP player has been added
- Till this version the power point and any applications was not given importance.
- The development of latest version of the GUI was available in J2me, which decreased the application size.
Bluetooth remote control 4.0
- Though they added, Win AMP could not be launched from it.
- The phone could not be compactable with other stacks.
- Response was improved for some functions.
- The application had problems with the connection and disconnection.
- Less application size than compare to the above version was achieved by better versions of MIDP and CLDC.
Some individuals have been working on this software like Jerome Laban. The project related to two PC remotes, the software developer who is working on compatibility for different types of mobiles such as Orange E200/QTEK 8080 and some are Motorola based mobiles with Blue Soleil third party stack in .NET FRAMEWORK 2.0 where he using different programming languages and client software’s.
There has been lot of development going on PC remote using Mobile phone Bluetooth many of them are developing many applications based on different software’s .The improvement in MIDP, CLDC in the new mobile have increased the applications, and the application code size started to decrease with improvements in them.
1.4 RATIONALE FOR RESEARCH:
After my under graduation I started working in an embedded system based company in India. Lampex electronics Ltd which deals with providing embedded solution to local firm, we had an Electrical billing handheld machine, which we supplied to state of Andhra Pradesh (India) Electricity board, they requested for a short distance wireless technology to upload the data from handheld machine to PC. We have selected IrDA as wireless technology because of low power consumption and less memory application .We have done the work successfully but as a developer, I was not convinced for two reasons:
- The handheld machine and PC transceivers have to be placed face to face.
- We had problem with time slots management, went slaves (handheld machine) are more than two at the same time.
This made me to select Bluetooth technology as my research topic, and then I came across different research topics on Bluetooth related to security, pairing, remote PC manager etc. Then I started working on a Remote PC manager.
Remote PC manager is an application developed using Bluetooth available in your mobile phone to manage a PC. The application had problem related to response time in certain areas of application. The response time is the time an application takes to react to a give input. In this application, we define response time as the time taken to respond when an instruction have been sent from mobile phone to remote pc manager.
AND RESEARCH METHODOLOGY
2.1 RESEARCH APPROACHES:
The following are the approaches towards my research, which have eventually done in stages:
- To study about Bluetooth behaviour and comments related to the application from the users.
In the course of research, reading has been done from books, journals and websites regarding Bluetooth and related software is used in the project.
- Developing Program and data flow diagrams
An IT related program was developed which had all the modern approaches to the project development and deployment and as well as the data flow diagrams were drawn for the clear view of the data in the program
After the development of the programs, implementation has carried out to check its success and working
The programmable code is tested, verified and made sure that its bug free.
2.2 Justification of Research Approaches:
Mixed research methods have been used for projects as it deals with collecting information about the product and implementation to the product. Using Qualitative research, more data is gathered from journals and textbooks, which showed about the Bluetooth applications. There was also chance to know, to what are hurdles in the existing Bluetooth technology. I have registered in Bluetooth groups and started to ask experts in this field about their feedback regarding the application. I went through some of the existing technologies available in the market and where I could study the functioning of the Bluetooth PC remote. Knowing about the application, I could estimate that projects with modern approach will be needed, in enhancing the application throughput. Online journals also helped me out a lot. Research books also helped me in how to carry out my research and which method would more suit my needs.
Quantitative research is also a very important criterion in my research .I could plan my whole project on Gantt chart and proceed further. So, I had opted with mixed approach, i.e. qualitative and quantitative which made my research easier.
2.3 LITERATURE REVIEW:
A lot of research is done on Bluetooth related application by Special Interest Groups (SIG) and developer all over the world because of its futuristic nature. From the past most of the developers have been developing applications on Bluetooth and WLAN. We can see degradation on Wi-Fi when a Bluetooth is close to the Wi-Fi station; the impact of interference is significant. However, the relocation of Bluetooth from the Wi-Fi by 10m will not have great impact on the throughput. So both can coexist but we should be sensible in our expectations and attempts to combine these technologies. [Brent A. Miller, Chatschik Bisdikian 2000]. We present an AFH that modifies it in order to mitigate interference. Frequency hopping in Bluetooth is achieved as follows. Frequencies are listed as even and odd frequencies in the range of 2.402-2.480 GHz. The main idea in BIAS is to wait for association of slot with a “good” frequency in order to transmit a packet.
The basic idea of response times has been about the same for thirty years [Brent A. Miller, Chatschik Bisdikian 2000]:
- If the response time is about 0.1 second user feels that the system is reacting instantaneously, means that no feedback is necessary except to display the result.
- If the response time is about 1.0 second user feels to stay uninterrupted, even though the user will notice the delay. Normally, no feedback is necessary during delays of more than 0.1 but less than 1.0 second, but if its 1 second the user feels that he can directly on the data.
- If the response time is about 10 seconds user’s attention is focused on the dialogue. For longer delay such as scanning whole system by anti virus will take long time and user knows about it. Feedback is required especially important if the response time is likely to be highly variable, since users will not know what to expect.
Normally, response time of an application should be as fast as possible [Myers, B., H. Stiel & R. Gargiulo (1998)], but it is also possible for the computer to react so fast that the user cannot keep up with the feedback. For example, a scrolling down in word document application move so fast that the user cannot stop it in time for the desired pages or section within the available window. The fact is that computers with modern processor can go work in few milliseconds can be too fast for the user which indicates the need for user-interface changes, user interface is set according to real-time clock rather than being set to indirect effect of the computer’s execution speed.
These applications take advantage in varying degree of Bluetooth capabilities such as to be always on, always connected, mobile and easy to use. Throughout all of this, of course it is important not to lose sight of the requirements to get basic application to operate properly. However most of developers have found the specification of 1.1 to be stable, so future Bluetooth enabled products for general consumer would confine to this specification [Robert Morrow, 2002]. In an indoor environment, multipath is almost present because of furniture and other equipment in building along with the building material themselves, are prone to reflections when they are illuminated from radio source. Unlike the large fading which is seen in radio frequency where distance travel by the wave is in terms of 10 times the wavelength.
According to Morrow the Bluetooth, channel fading could be analysed based on Doppler spread, delay spread and out probability.
- If a Bluetooth Piconet is an indoor environment where an object can move at speed up to a fast walk, then minimum Doppler shift will be about 10 Hz and coherence time is about 40 ms. So, the coherence time will be 1 microsecond smaller than coherence time which leads to slow fading and this could really slow down when 40000 bytes transfer is done.
- Suppose if we take a large room where the delay speed is 50ns and gives coherence bandwidth of 2 MHz, but maximum bandwidth between each hop is only 1MHz, so this leads to flat fading.
- As the Bluetooth channel is flat fading this will effect the Bit Error Rate
BER (Rayliegh equation).
According to Morrow the enhancement has done related to lower level protocol.
- Bluetooth data rate should be increased at the rate of 10 to the present specification.
- Proper implementation of Adaptive frequency hopping should be done.
- The range of Bluetooth has to be increase by Store and forward capability.
- Use of Smart antenna.
The ACL link is based on polling scheme mechanism between master and up to seven active slaves in a Pico net. It can provide both symmetric and asymmetric bandwidth, which is determine by the packet type and frequency with which the device is polled. The ACL payload is protected by CRC check, which is used for retransmission scheme, the value seems to be small about 1.25ms [David, 2002], but it is important when we are dealing with IP streaming because it may lead to retransmission delay. This could be limited by setting the flush timeout setting.
If Bluetooth transmit constantly on same frequency, the maximum raw date rate would be 1 mbps. However [David, 2002], this is not the data rate we will obtain over air interface. Bandwidth required for a 72 bit access code to identify the piconet and 54 bit header to indentify the slave will be about 405microseconds and guard time of 220 microseconds for next frequency hop. So, one slot packet requires a bandwidth of about 1/3 for pay load data and 7/9 and 13/15 for 3 and 5 slots of data respectively. So these counts have at least guard time of 1250 micro second as slot size increases.
User friendly can be defined as easy to learn, easy to use, easy to remember and they increase the user ability to perform the desired task. According to Barrie Shermann, 1985 User friendly means adapting parts of the system to the operator rather than the operator having to adjust to the system.
Donald Norman explains user friendly software design with respect to relationship between visibility, mapping and feedback to the design of usable objects. [The Design of Every day Things,1990]
- Visibility means how easy user can find the function in the software. Poor visibility can cause too many problems to the users.
- Mapping means the relationship between controls, the thing it affects, outcome. Good mapping is one which has buttons which is clearly marked and simply indicates their function.
- Feedback to the design of usable objects means every function on operation must give feedback to the user. When passenger press train door button he gets feedback in terms of voice message saying that “door opening” .Such feedback makes user feel good.
The creation of user friendly software is equal to part of science and art .The science is referred to as usability. The International Organisation for standardization (ISO) defines usability as the effectiveness, efficiency and satisfaction with which the user achieve specified targets. Effectiveness is the accuracy and completeness with which specified user can achieve goal in an environment. Efficiency is the resource expended in relation to the accuracy and completeness of goal achieved. Satisfaction is the comfort and acceptability of work system to its users and other people affected by its use.
The second part is the Art of design, which inspires and often take long time .We are not speaking about art in terms of graphic art, although it plays an important role in development of user friendly software. We are speaking of the designer ability to create a vision of how software can and should be.
2.4 CRITICAL ANALYSIS:
Since this Bluetooth application is an indoor application, it’s associated with reflection, diffraction, scattering, and refraction of radio waves. Quality of service means predefined and negotiated data rate, delay and error rate. Since the delay and the error rate are strongly related to the data rate, we focus our present investigations on the data rate. A signal passed over a wireless channel is affected by path loss, narrow, wideband fading and co-channel interference. In the present application the response time is dependent on, the performance metrics include the path loss, the mean access delay and the channel response time.
When a receiver is placed some distance from the transmitter antenna it is logical to say that there will be some loss in signal. As we know that there is high probability of multipath effects in this application, as it plays a significant role in path loss values, thus high path loss of signal will lead to retransmission of signal. So we need to perform multipath mitigation, so we have selected compensate for multipath through diversity combinations. So normal Bluetooth antenna will be replaced by smarter antenna with diversity combinations .The packets that are transferred consecutive to time do not use the same frequency, which in turn avoids the drawbacks of the narrowband transmission. As we know that the link performance obeys the rules for narrow band systems and additionally depends on fading of the individual channels occupied. Therefore, all these methods of improving the physical layer have to be frequency agile.
The access delay measures the time taken to transmit a packet from the time it is passed to the MAC layer until it is successfully received at the destination. The delay is measured at the L2CAP layer. The access layer delays which are caused due to improper management of the Bluetooth instruction. Management of ACL links can decrease this and by keeping slot numbers at a low value as possible, but as file length increases the number of slot tends to increase so we cannot do much to that, but by decreasing the path loss we can definitely resend ACL link commands.
The channel estimation response time measures the time to track changes in the channel state. It is the time to avoid using a bad frequency to the time to start reusing a frequency that is good. The channel response time depends upon the bit error rate (BER), which depends on the frequency hopping rate (good frequency and bad frequency), since the methods used to perform the classification depend on BER measurements per frequency visited. So, proper implementation of adaptive frequency hopping must be done to improve response time.
User friendliness is a thin gap between failure and success of the end product. According to usability studies done by Andy Smith Overall it would seem that roughly only 30 percent of IT systems are fully successful and that too 70 percent either fail or some marginal gain even after providing same function. These successful one have marginal difference with the other such as easy to handle, light weight, high visibility of screen, little more advance feature in hardware and software, robust etc. Natural and efficient products can make user’s task seem a lot easier.
BLUETOOTH PC REMOTE
Bluetooth was projected to allow low bandwidth wireless connections to become so simple to use such that they flawlessly work into your daily life. A simple example of a Bluetooth application is to update the phone directory of your mobile phone. You would either normally enter the names and phone numbers of all your contacts or use a cable or IR link between your phone and your PC and start an application to synchronize the contact information. With Bluetooth, this can be done automatically and without any user involvement as soon as the phone comes within range of the PC. You can easily see this is expanded to include your calendar, to do list, memos, email, etc. This is just one of many exciting applications for this new technology! The Bluetooth PC remote using Mobile phone also comes into these list of applications that is been developed in using Bluetooth
3.2 SYSTEM ARCHITECTURE:
Bluetooth communications occur in the unlicensed ISM band at 2.4GHz. The transceivers utilize frequency hopping to reduce interference and fading. A classic Bluetooth device has a range of about 10 meters, with a total bandwidth of 1 Mb/sec. This technology supports two types of communication modes [Robert Morrow, 2002].
- Synchronous communication (voice traffic): The synchronous voice communication is provided using circuit switching with a slot reservation at fixed intervals. A synchronous link in Bluetooth technology is referred to as an SCO (synchronous connection-oriented) link.
- Asynchronous communications (data traffic): The asynchronous data communication is provided using packet switching, utilizing a polling access scheme. An asynchronous link in Bluetooth technology referred to as an ACL (asynchronous connection-less) link.
Max. Data Rate Upstream
Max. Data Rate Downstream
3 Simultaneous Voice Channels
64 kb/sec X 3 channels
64 kb/sec X 3 channels
723.2 kb/sec or 57.6 kb/sec
57.6 kb/sec or 723.2 kb/sec
Reference [www.bluetooth.com ]
A combined data-voice SCO packet is defined, which can give 64 kb/sec voice and 64 kb/sec data in each direction.
3.3 THE PICONET:
Bluetooth devices can pair up with one or more other Bluetooth devices in several different ways. The simplest way of connecting two Bluetooth devices, is by connecting point-to-point when there are two Bluetooth devices is known as Pico net. One of the devices acts as the salve and the other as a master. This ad-hoc network is a good example for a Pico net. A simple Pico net network needs to have one master and one or more slave, the Bluetooth can have maximum of seven slaves in a Pico net network.
In the case of multiple slaves, the communication topology is known as point-to-multipoint. In this case, the bandwidth is shared among all the devices in the Pico net. They can communicate up to seven active slaves in a Pico net. In the case of multiple slaves concept the slaves need to have specific address. So each of the active slaves has been assigned 3-bit Active Member address (AM_ADDR). There can be extra slaves who remain synchronized to the master, but these will not have an Active Member address. The slaves are not active and are referred to as parked. In case of both active and parked units, the complete bandwidth is synchronized by the master. A parked device will have an 8-bit Parked Member Address (PM_ADDR), thus we can have maximum number of parked members to 256. A parked device remains synchronized to the master clock and can vary quickly, become active and communicate with other devices in the Pico net.
3.4 THE SCATTERNET:
The process in which two adjacent Pico nets have an overlapping of coverage area is known as scatter net. Slaves in one Pico net can take part in another Pico net as either a master or slave; it can be done through time division multiplexing. In a scatter net, the two (or more) Pico nets are not synchronized in either time or frequency. Each of the Pico nets operates in its own frequency hopping channel while other devices in multiple Pico nets participate at the appropriate time via time division multiplexing.
Let us assume two different Pico nets one consisting of mobile phone and PC, while the adjacent Pico net person consisting of a cell phone, headset and business card scanner.
Dig Ref : www.wirelessadvent .com/channel/blutooth/feartutre/bluetooth .html
The cubicle 1 may set up cubicle 2 business card scanner also transmit the information that is scanned to your PC so that you will have access to his business contacts information.
3.5 AUTHENTICATION AND PRIVACY:
Authentication and privacy are handled at the software protocol layer and it is also provided in the Bluetooth physical layer. A particular connection can be specific to need either one-way, two-way, or no authentication. The authentication is generally done using a challenge or response to the system. The system supports both 40 and 64 bit keys. The authentication of the user is done at application layers. This security mechanism and the related software allow the user to set up his or her devices only to communicate with each other. All Bluetooth devices employ this physical layer security in the same way. Of course, for highly aware applications, it is also recommended that you use more advanced algorithms in the network transport or application layer.
3.6 HARDWARE FOR BLUETOOTH:
Bluetooth hardware can be divided into two modules, they are.
- Radio Module
- Link Module.
The Radio Module:
Bluetooth devices operate in 2.4GHz Industrial Scientific Medicine (ISM) band. The frequency is an unlicensed one because of international standards and a few exceptions in certain countries like France (2446.5 to 2483.5 MHz) and Spain (2445 to 2475 MHz .So range of frequency is defined with unlicensed version from 2400 to 2483.5 MHz. These local versions have a reduced frequency band and a different hopping algorithm, the Bluetooth SIG is working with authorities in different countries to open compact ability.
The RF channels used in Bluetooth technology are from 2402 to 2480 MHz with a channel spacing of one MHz. Frequency hopping has been implemented in order to reduce interference and fading effects. So we have 625 microseconds the channel will hop to another frequency within the 2402 to 2480 MHz range, so we get 1600 hops every second. Every Pico net has a unique hopping sequence which is determined by using an algorithm; the uses of Bluetooth device address the master device. All Bluetooth units in the Pico net are then synchronized to this hopping sequence.
All packets are transmitted at the beginning in one of the 625 microsecond time slots, a packet may take 5 time slots. A time division duplex method is used to facilitate full duplex transmission. It is normally done this way, during even numbered slots the master transmits data and odd numbered slots are for a slave to transmits data. In voice data, these time slots can be reserved for synchronous applications.
Bluetooth technology use Gaussian Frequency Shift Keying (GFSK) for modulation. A binary system is used where logical one is represented by a positive frequency deviation and a logical zero is represented by a negative frequency deviation. The data is transmitted at a sign rate of 1 Ms/sec.
The Link Module
The Link Module and Link Manager Software are responsible for the baseband protocols and some other low level link functions. This are related to sending/receiving data, setting up connections, error detection and correction, data whitening, power management and authentication.
The link module in the Bluetooth is responsible for deriving the hop sequence. This can be done by using the BD_ADDR (Bluetooth Device Address) of the master device. All Bluetooth devices are assigned with a 48-bit IEEE 802 address. This 48-bit master device address is used by all other devices in the Pico net to derive the hop sequence.
The Link Module is also responsible for performing three error correction schemes that are defined for Bluetooth:
- 1/3 rate FEC
- 2/3 rate FEC
- ARQ scheme for the data
The purpose of having two FEC (forward error correction) schemes is to reduce the number of retransmissions. The ARQ scheme (automatic retransmission request) is responsible for the data to be retransmitted until an acknowledgement is received indicating a successful transmission (or until a pre-defined time-out occurs). A CRC (cyclic redundancy check) code of 2 bytes is added to each packet and used by the receiver to decide whether the packet arrived is error free or not. Note that the ARQ scheme is only used for data packets, but not for synchronous payloads such as voice.
Bluetooth provides necessities for three low power saving modes to conserve battery life. These states in decreasing order of power are Sniff Mode, Hold Mode, and Park Mode. While in the Sniff mode, a device listens to the Pico net at a reduced rate. The Sniff intervals provide flexibility for different applications and are programmable. The Hold mode is same as the Park mode, except that the AM_ADDR (Active Member address) is retained. In Park mode, the slave clock continues to run and remains synchronized to the master, but whereas the device does not participate at all in the Pico net.
4.1 INTRODUCTION TO SYSTEM DESIGN:
The Basic structure of software has been developed as an application based on Bluetooth technology, using the host controller interface concept. This is one of the most common physical implementation in which external cards are plugged into the host computer .when cond in this manner we need to have some ways to send the data and commands to module to obtain the results. The Bluetooth specification has such provision to have host controller interface. The Bluetooth protocol stack consists of the radio, link controller, link manager and the rest of the protocol stack from the L2CAP and above resides on the Host controller interface (HCI) .Hence the HCI provides the communication between the application at the top layer to the link manager, two ways audio packet transportation and transfer the data packet between module (USB dongle) and host computer.
HCI interface does not require great knowledge or certification, but it is a good idea when you want to implement any software so that it has wide range of compatibility and also provides us in operating the third party protocol also. The Host cont
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