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Bluetooth Hotspot: Extending the Communication Range between Bluetooth Devices Madhu Kanojia, Swati Garje Lokmanya Tilak College of Engineering, Navi Mumbai, Maharashtra [email protected] Lokmanya Tilak College of Engineering, Navi Mumbai, Maharashtra [email protected] Abstract: Bluetooth is a wireless technology standard for exchanging data over short distances from fixed and mobile devices and building personal area network (PANs).Bluetooth is a wireless communication protocol, since it’s a communication protocol, you can use Bluetooth to communicate to other Bluetooth enabled devices. Bluetooth has a client server architecture; the one that initiates the connection is the client, and the one who receives the connection is the server. Keywords: Ad hoc, Bluetooth, piconet, scatternet, Hotspot, Internet, GPRS or Wi-Fi facility. 1. Introduction Bluetooth (Ericsson trademark) takes its name from Harald Blatland (Bluetooth), a Danish king born in AD 908 who united his country under Christianity. An Ericsson-led consortium, including IBM, Intel, Nokia, and Toshiba, have developed the technology. A second group, the Bluetooth Special Interest Group (SIG) was then formed to promote the technology and comprised 1371 member companies in early January 2000 [12]. Ad hoc networks today are based primarily on Bluetooth technology. Bluetooth is an open standard for short-range digital radio. It is touted as a low –cost, low –power, and low profile technology that provide a mechanism for creating small wireless networks on an Ad hoc basis. Bluetooth is considered a wireless PAN technology that offers fast and reliable transmission for both voice and data [3]. Untethered Bluetooth devices will eliminate the need for cables and provide a bridge to existing networks [1].A broadband hotspot is one application where Bluetooth has a value in providing internet access to mobile users. Consumers owning a Bluetooth enabled mobile phone can easily access a Bluetooth hotspot to browse the internet without having to carry a PDA or laptop [3].A distinguishing feature of Bluetooth networks is the master-slave relationship maintained between the network devices.Upto eight Bluetooth devices may be networked together in a masterslave relationship called piconet. As shown in Fig 1 In piconet one device is designated as the master of the network with upto seven slaves connected directly to the network [1]. Figure 1: Piconet and Scatternet 2. Bluetooth Protocol Stack The protocol stack makes up the core portion of the Bluetooth implementation [3]. As shown in figure 2 the connection devices can exchange data and interact with one another through various applications. The protocol architecture of the bluetooth consists of following in a bluetooth protocol stack: Core protocols consisting 5 layer protocol stack viz. radio, baseband, link manager protocol, and logical link control and adaptation protocol, service discovery protocol. Cable replacement protocol ,RFCOMM Telephony Control Protocols Adopted protocols viz. PPP, TCP/UDP/IP, OBEX and WAE/WAP [5]. 2.1 Core Lower Layers 2.1.1 Radio This layer deals with the conversion of data into radio frequency (RF) signals for transmission through the air [4].Data is broken up into very small packets and transmitted usually one packet per frequency jump or slot [1]. Bluetooth operates in the 2.4 GHz Industrial, Scientific and Medical (ISM) radio-frequency band, which is license-free for lowpower transmissions in most of the world [3] 2.1.2 Baseband/Link Controller Addressing scheme, packet frame format, timing and power control algorithms required for establishing connection between bluetooth devices within piconet defined in this part of protocol specification [3].The baseband layers role is to properly format data for transmission to and from the radio module and perform basic error control[1].The link controller is responsible for encoding and decoding of Bluetooth packets from the data payload and parameters related to the physical channel, logical transport and logical link[4]. 2.1.3 Link Manager The link manager is responsible for the creation, modification, and release of logical links as well as the update of parameters related to physical link between devices [4]. This protocol also includes authentication and encryption specifications [5]. 2.2 Host Controller Interface(HCI) The HCI provides a command interface to the baseband link controller and link manager, and access to hardware status and control registers [6].The host controller driver should be independent of the underlying transport technology [4]. 2.3 Core Upper Layers 2.3.1 Logical Link Control and Adaptation The Logical link control and adaptation protocol acts as the middle manager between applications and the bluetooth link controller [3].L2CAP passes packets either to the Host controller Interface(HCI),or in a Host-less system,L2CAP passes packets directly to the Link manager[7]. 2.3.2 Service Discovery Protocol Service related queries including device information can be taken care at this protocol so that connection can be established between bluetooth devices [5]. SDP consists of servers and clients components, where the requesting devices are a client and the requested device the server. A single Bluetooth device can perform both roles of a SDP-server and –client [3]. 2.4 Non-Core Upper Layers 2.4.1 RFCOMM The RFCOMM protocol provides emulation of serial ports over the L2CAP protocol. RFCOMM is only concerned with the connection between the devices in the direct connect case, or between the device and a modem in the network case [8]. 2.4.2 OBEX Object Exchange (OBEX) is a widely used protocol for simple file transfers between mobile devices. Its main use is in infrared communication, where it is used for generic file transfers between notebooks or PDAs, and for sending business cards or calendar entries between cellular phones and other devices with Personal Information Manager (PIM) application. The OBEX client is used to push and/or pull objects from the OBEX server [8]. 2.4.3 Bluetooth Network Encapsulation Protocol (BNEP) The Bluetooth Network Encapsulation Protocol (BNEP) sits on top of L2CAP and allows standard network protocols such as TCP, IPv4 and IPv6 to be transported across Bluetooth links. BNEP provides this encapsulation by replacing the Ethernet header, with a BNEP header and sends this header and the data across the L2CAP layer [3]. 2.5 Audio Audio transmission can be performed between one or more bluetooth units, using many different usage models. Audio data do not go through the L2CAP layer but go directly, after opening a bluetooth link and a straightforward setup between two bluetooth units [9]. 2.6 Finding a Device Before a device is able to make a connection to another device, it needs to discover that device. For device discovery, the three states are inquiry, inquiry scan and inquiry response [3]. Figure 2: Bluetooth protocol stack 2.6.1 Inquiry State The inquiry state is entered when a device attempts to discover all other devices within range. In this state the searching device repeatedly transmits inquiry message on a set of different frequencies [3]. 2.6.2 Inquiry Scan Display For a Bluetooth device to be discoverable, it has to answer inquiry messages from other devices. This is done by entering an optional inquiry scan state. A device which is discoverable does this periodically (at least every 2.56 seconds) and listens for an extended time compared to the inquiry state. If a device does not want to be located it can be set to be non-discoverable and therefore will not enter the inquiry scan state [3]. 2.6.3 Inquiry Response State When a device receives a valid inquiry message it will then enter the inquire response state and respond with a frequency hopping synchronisation (FHS) packet [1]. 3. Need As the number of bluetooth products increases each year, it is important to develop applications and services to take full advantage of their potential and capabilities. A broadband hotspot is one application where Bluetooth has a value in providing Internet access to mobile users. Consumers owning a Bluetooth enabled mobile phone can easily access a Bluetooth hotspot to browse the Internet without having to carry a PDA or a laptop [10]. sitting in front of the PC if the acquired slave information indicates that the user’s bluetooth device is specified as an authentication key [11]. Figure 3. Inquiry Method 5.2 Communication Link Method A communication link is data transmission connection between a master and slave for sending and receiving data packets. The master sets up a communication link to a slave by using slave information when the master establishes a connection with the slave, and it controls data transmission to confirm whether the slave can communicate with it[11]. 4. Basic Steps Steps to be followed in Bluetooth hotspot are: • Connectivity • Authentication and security • Data transfer The process starts with connectivity process in which Bluetooth server sending a message of pairing to all the discoverable mobile devices in its range. The devices receiving the message need to send an appropriate response to the server back to complete the authentication. Now the connection link is established and the data/ file transfer can take place [10]. 5. Connectivity Identification and authorization are the two important steps for having trusted connection between two Bluetooth devices. Connectivity is the first step for establishing any Connection [11]. Figure 4. Communication link Method 6. Eavesdropping is the act of secretly listening to the private conversation of others without their consent [11]. 6.2 • Inquiry method (Inquiry function of Bluetooth) • Communication link method (Monitoring communication link) 5.1 Inquiry Method The Bluetooth device of the PC (master) gets the slave information of surrounding Bluetooth devices by running the inquiry function regularly. The PC then judges that the user is Security When a user sends data over a wireless network, he has a reasonable expectation that such data is not easily readable by unauthorized persons. Unlike a wired network, which requires a physical intrusion, wireless data packets can be received by anyone nearby with an appropriate receiver, potentially outside the physical security barriers of an organization. There are basically two main security issues in wireless technology which are needed to be considered for trust building between two devices [11]. Eavesdropping False authentication Bluetooth technology provides a method for authenticating devices .Device authentication is provided using a shared secret between the two devices. The common secret key is called a link key. There are two types of link keys. Unit keys and combination keys [11].A device using a unit key uses the same secret for all of its connections. Combination keys are link keys that are unique to a particular pair of devices. The combination key is only used to protect the communication between these two devices [11].Authentication is performed with a challenge response Scheme utilizing the E1 algorithm. The scheme operates as follows: The verifier issues a 128 bit long challenge. The claimant then applies E1 using the challenge, its 48-bit bluetooth address, and the current link key. He then returns the 32 most significant bits of the128 bit result. The verifier confirms the response, in which case the authentication has succeeded [11]. 7. Data Transfer Data is transferred using packets .To transfer data, a link needs to be established between the devices. Between two (or more) Bluetooth devices two types of links can be established, namely: 8.2.1 Masquerading This requires designing a system where each hotspot is able to masquerade as other bluetooth devices and therefore able to advertise itself as a device that is located at other hotspots. As shown in the Figure 6 where bluetooth device A is communicating with bluetooth device B via the hotspots. Each Bluetooth device thinks that it is communicating directly with each other but in fact are communicating with the respective hotspot which is masquerading as the distant device. • Synchronous Connection-Oriented (SCO) link The SCO link is typically used for time-bounded data, such as voice. • Asynchronous Connectionless Link (ACL) The ACL link works as a traditional packet switched network. Packets are transmitted only when necessary. 8. Proposed Bluetooth Hotspot In this section we propose a bluetooth hotspot and examine two different implementation approaches. 8.1 BlueSpot BlueSpot, the software components of the proposed Bluetooth hotspot are introduced, as well as the connection framework between these components and other hotspots. Bluetooth devices that are out of radio range to communicate with each other we envision setting up a collection of devices that would be connected together by an IP network as shown in Figure 4 and would act as what has been called Bluetooth hotspots. These Bluetooth Hotspots would allow Bluetooth devices that are distant from each other but within range of a hotspot to be able to communicate with each other via the hotspots. Figure 6: Using masquerading to create communications 8.2.2 Using Service Proxying The second method was to examine Bluetooth’s SDP and the feasibility of using SDP to provide facilities to discover remote devices and make possible the setting up of communication links between devices. Figure7: Using Service Discovery to create communications As shown in figure 7 a user (Device A) within the range of hotspot (Hotspot X) is able to query that hotspot for all the services that it offers. The hotspot will then return a list(“service available”) of what other devices (device B) are within range of other distant hotspot(Hotspot Y) and what services they can offer to allow for communication with a distant device [1]. Figure 5: Bluetooth Hotspot 8.2 Different Approaches The functionality of extending the reach of Bluetooth Communication can be implemented at different layers in the Bluetooth protocol stack. These could be broken down into two primary implementation approaches: Hotspots masquerade as other remote bluetooth devices, Hotspots offer or otherwise proxy the services offered by other devices 8.3 Bluetooth Hotspot The bluetooth hotspot is made up of three separate interlinked components. Figure 9: Advertising a services Figure 8: Bluetooth hotspot components 8.3.1 Management Component: Manages the other software components that make up the hotspot as well as detects when bluetooth devices come within range and leave. The main role of the management component is to supervise such as start and stop the different applications. It periodically scans for the local bluetooth devices that have entered range and detecting as if previously detected device is not communicating and inform to service device component about new device. 8.3.2 Using a proxyed service Service Database Component: Collects, stores and advertises services that are detected by all the Bluetooth hotspots within a network. When it is notified of a new bluetooth device it will acquire a list of all the services that that device is advertising via its SDP server. If the services have transport application available then it can added to an internal database and all the other remote database are notified about the device. Then the local and remote databases will start the transport. 8.3.3 Transport Component: This makes the connection between hotspot and bluetooth devices. It transports the bluetooth communications between the two bluetooth devices via bluetooth hotspots over an IP network. 8.4 8.4.2 Figure 10: Using a proxyed service 1. A bluetooth device B browses the SDP server on Hotspot Y. 2. The transport component then connect to its peer and start transmitting the data received from device B1. 3. A bluetooth device B browses the SDP server on Hotspot Y2. 4. Using the above information it then connect to the transport component and transport component is then connect to its peer and start transmitting the data it receives from device B. Connection Framework The two jobs that a bluetooth hotspot performs are the advertising of services from remote devices and the facilitating of communication between two devices. 8.4.1 Advertising a service The steps for advertising a service are: Bluetooth hotspot X detects bluetooth device A. 1. The management component informs the local service database component(SDC) of the new device within range 2. The SDC queries the SDP server on the bluetooth device and finds out what services it is able to facilitate. 3. The SDC then starts the transport component for services. 9. Bluetooth vs. Infrared Infrared Infrared technology is what most TV remotes use. The distance an infrared signal can travel varies based on the strength of the remote, but is usually less than 50 feet for household electronics. In order for an infrared signal to be detected, there must be a direct line of sight between the transmitter (Remote) and the receiver (TV).If there is a wall on large object between them, the signal will not pass through it. Bluetooth Bluetooth uses a radio frequency, which allows transmission through walls and other objects. The standard range of bluetooth device is upto 30 ft. which makes it ideal for syncing PDAs with computers, using wireless cell phone headsets, and enabling hands free cell phone use inside Bluetooth-enabled automobiles. While Bluetooth is well on its way to replacing infrared in many different areas, the technology is not meant to be used for wireless networking. Instead, Wi-Fi technology, which has a larger range and higher bandwidth than Bluetooth, is the standard that most wireless networking equipment uses [13]. Conclusion Bluetooth is a wireless radio specification designed to replace the cables as the medium for data and voices signals between electronic devices. With the use of internet so rampant in these days the access of internet must be simplified and made common. Bluetooth Hotspot is the perfect way to realize this need. Bluetooth Hotspot already exists for use in computers and in laptops. But to carry around a laptop everywhere to access free internet on mobile phone is a lot of effort. Also a Bluetooth dongle should be used. That is why Bluetooth Hotspot will be of a great help. The Bluetooth specification seeks to simplify communication between electronic devices by automating the connection process. In this paper we explained Bluetooth protocol stack and its different layers, then moving on to how Bluetooth networks are formed and devices are located. The proposed idea in this paper is to develop Bluetooth hotspot and examine two different implementation Approaches. BlueSpot, the software components of the Proposed Bluetooth hotspot are introduced, as well as the connection framework between these components and other Hotspot. Aacknowledgement We would like to thank our guide, Prof. Anil Chhangani for his guidance and support, which has helped us, complete this research paper successfully. References [1] Pooja Sharma et al, / (IJCSIT) International Journal of Computer Science and Information Technologies, Vol. 2 (2), 2011, 817-823. [2] International Journal of Computer Science, Engineering and Information Technology (IJCSEIT), Vol.1, No.3, August 2011. [3] International journal of Advanced Technology & Engineering Research (IJATER). [4] https://developer.bluetooth.org/TechnologyOverview /Pages/Core.aspx [5] http://www.rfwireless-world.com/Tutorials/Bluetoothprotocolstack.html [6] Palowireles bluetooth resource center (http://een.iust.ac.ir/profs/Shahri/Computer%20Buses_8 4/bluetooth_tutorial.pdf) [7] http://oscar.iitb.ac.in/onsiteDocumentsDirectory/Bluetoo th/Bluetooth/Help/Logical%20Link%20Control%20and %20Adaptation%20Protocol.htm [8] https://www.freebsd.org/doc/handbook/networkbluetooth.html [9] http://www.thestudymaterial.com/presentationseminar/el ectronics-presentation/51-bluetoothtechnology.html?start=3 [10] http://www.ijarcce.com/upload/2014/january/IJARCCE1 E__a_prashant_bluetooth.pdf [11] International Journal of Advanced Research in Computer and Communication Engineering Vol. 3, Issue 1, January 2014 [12] J. Wakefield, Bluetooth: what is the potential? Analysts Disagree, ZDNet UK News, April 1999. http://www.zdnet. co.uk/news/1999/14/ns-7758.html. [13] http://pc.net/helpcenter/answers/bluetooth_vs_infrared