Bluetooth Intercom Vinita D. Mishra Patkar Varde College S. V. Road, Goregaon (West), Mumbai

Transcription

1 Bluetooth Intercom Vinita D. Mishra Patkar Varde College S. V. Road, Goregaon (West), Mumbai vinsmishra11@gmail.com Abstract This paper Defines feature of Bluetooth wireless communication technology and how it can be use for voice communication for small region. Bluetooth device can be use as intercom for any Organization or college campus. Keywords Bluetooth, mobile, wireless, scatternet. 1. INTRODUCTION Driven by the boom in Internet usage, on-line trading, banking and shopping, mobile and home offices, and corporate employees with multiple offices the convergence of the wireless radio and computer are a reality. Mobility is at the center of this marriage, bridging the gap between computing and communications for a wide range of computing devices such as notebook computers, pagers, cellular phones, and Personal Digital Assistants (PDAs). Connectivity among these devises will become a necessity to share resources, printing, transferring , Internet access and video data exchange among wired and wireless devices. Connectivity must incorporate the mobility of pagers, wireless and cordless phones, as well as the immobility of PCs and the portability of laptop computers. In a mobile work environment, communicating with office equipment without the burden of cables is not only convient and inexpensive it is also faster than serial or Irda and requires no line-line-of sight.the alternative to wired connectivity is the wireless short-range connectivity offered by Bluetooth technology at 2.4 GHz. Bluetooth is a wireless technology standard for exchanging data over short distances (using short-wavelength radio transmissions in the ISM band from MHz) from fixed and mobile devices, creating personal area networks (PANs) with high levels of security. Created by telecom vendor Ericsson in 1994, [2] it was originally conceived as a wireless alternative to RS-232 data cables. It can connect several devices, overcoming problems of synchronization. Originally Bluetooth conceived as a low-power short-range radio technology designed to replace cables for interconnecting devices such as printers, keyboards, and mice, its perceived potential has evolved into far more sophisticated usage models. The requirement to do this in a totally automated, seamless, and user-friendly fashion, without adding appreciable cost, weight, or power drain to the associated host is an enormous engineering challenge.bluetooth devices can form piconets of up to seven s and one master, enabling discovery of services and subsequent implementation of many varied usage models including wireless headsets, Internet bridges, and wireless operations such as file exchange, data synchronization, and printing. Bluetooth is managed by the Bluetooth Special Interest Group, which has more than 18,000 member companies in the areas of telecommunication, computing, networking, and consumer electronics. Bluetooth was standardized as IEEE , but the standard is no longer maintained. The SIG oversees the development of the specification, manages the qualification program, and protects the trademarks. To be marketed as a Bluetooth device, it must be qualified to standards defined by the SIG. [citation needed] A network of patents is required to implement the technology, which is licensed only for that qualifying device. Bluetooth is essentially a networking standard that works at two levels: It provides agreement at the physical level -- Bluetooth is a radio-frequency standard.it provides agreement at the protocol level, where products have to agree on when bits are sent, how many will be sent at a time, and how the parties in a conversation can be sure that the message received is the same as the message sent. 2. WHY IS IT CALLED BLUETOOTH? Harald Bluetooth was king of Denmark in the late 900s. He managed to unite Denmark and part of Norway into a single kingdom then introduced Christianity into Denmark. He left a large monument, the Jelling rune stone, in memory of his parents. He was killed in 986 during a battle with his son, Svend Forkbeard. Choosing this name for the standard indicates how important companies from the Nordic region (nations including Denmark, Sweden, Norway and Finland) are to the communications industry, even if it says little about the way the technology works. 3. HOW BLUETOOTH OPERATES? Bluetooth networking transmits data via low-power radio waves. It communicates on a frequency of 2.45 gigahertz (actually between GHz and GHz, to be exact). This frequency band has been set aside by international agreement for the use of industrial, scientific and medical devices (ISM). A number of devices that you may already use take advantage of this same radio-frequency band. Baby

2 monitors, garage-door openers and the newest generation of cordless phones all make use of frequencies in the ISM band. Making sure that Bluetooth and these other devices don't interfere with one another has been a crucial part of the design process. One of the ways Bluetooth devices avoid interfering with other systems is by sending out very weak signals of about 1 milliwatt. By comparison, the most powerful cell phones can transmit a signal of 3 watts. The low power limits the range of a Bluetooth device to about 10 meters (32 feet), cutting the chances of interference between your computer system and your portable telephone or television. Even with the low power, Bluetooth doesn't require line of sight between communicating devices. The walls in your house won't stop a Bluetooth signal, making the standard useful for controlling several devices in different rooms. Bluetooth can connect up to eight devices simultaneously. With all of those devices in the same 10-meter (32-foot) radius, you might think they'd interfere with one another, but it's unlikely. Bluetooth uses a technique called spreadspectrum frequency hopping that makes it rare for more than one device to be transmitting on the same frequency at the same time. In this technique, a device will use 79 individual, randomly chosen frequencies within a designated range, changing from one to another on a regular basis. In the case of Bluetooth, the transmitters change frequencies 1,600 times every second, meaning that more devices can make full use of a limited slice of the radio spectrum. Since every Bluetooth transmitter uses spread-spectrum transmitting automatically, it s unlikely that two transmitters will be on the same frequency at the same time. This same technique minimizes the risk that portable phones or baby monitors will disrupt Bluetooth devices, since any interference on a particular frequency will last only a tiny fraction of a second. When Bluetooth-capable devices come within range of one another, an electronic conversation takes place to determine whether they have data to share or whether one needs to control the other. The user doesn't have to press a button or give a command -- the electronic conversation happens automatically. Once the conversation has occurred, the devices -- whether they're part of a computer system or a stereo -- form a network. Bluetooth systems create a personalarea network (PAN), or piconet, that may fill a room or may encompass no more distance than that between the cell phone on a belt-clip and the headset on your head. Once a piconet is established, the members randomly hop frequencies in unison so they stay in touch with one another and avoid other piconets that may be operating in the same room. Let's check out an example of a Bluetooth-connected system. 4. COMPUTER REQUIREMENTS An internal notebook Bluetooth card ( mm).a personal computer that does not have embedded Bluetooth can be used with a Bluetooth adapter that will enable the PC to communicate with other Bluetooth devices (such as mobile phones, mouse and keyboards). While some desktop computers and most recent laptops come with a built-in Bluetooth radio, others will require an external one in the form of a dongle. Unlike its predecessor, IrDA, which requires a separate adapter for each device, Bluetooth allows multiple devices to communicate with a computer over a single adapter. A Bluetooth-enabled mobile phone is able to pair with many devices. To ensure the broadest feature functionality together with compatibility with legacy devices, the Open Mobile Terminal Platform (OMTP) forum has published a recommendations paper, entitled "Bluetooth Local Connectivity". 5. THE BLUETOOTH SIG Since the original Bluetooth specification was published in 1999, more than 2000 additional companies have signed on as associate members, able to participate in development of future standards and extensions by contributing efforts to various working groups. 5.1 The Current Specification The current specification, Ver , defines a radio which operates in the unregulated Industrial, Scientific, and Medical (ISM) band as follows: 2.4 GHz, FHSS w/1600 hops/s over 79 channels: 1 Mbps The fundamental elements of a Bluetooth product are defined in the two lowest protocol layers, the radio layer and the baseband layer. Included in these layers are hardware tasks such as frequency hopping control and clock synchronization, as well as packet assembly with associated FEC (Forward Error Correction) and ARQ (Automatic Repeat Request). The link manager layer is responsible for searching for other Bluetooth devices, creating and tearing down piconets, as well as authentication and encryption. Higher layer definitions include the Bluetooth profiles. Enhancing the Specification The Bluetooth SIG is currently working on a new specification, due for publication sometime in In the interest of maintaining backwards compatibility, most of this work is confined to describing new profiles. One of the most intriguing is a car profile that describes the use of personal devices like pagers, cell phones, and laptops in an automotive environment. Envisioned usages include the automatic adjustment of various settings in an automobile, such as seat and mirror positions and radio tuning, based on

3 personal preferences stored in a Bluetooth device. Another profile would link a cell phone, car radio, and text-to-speech software on a laptop, to allow to be spoken audibly over the car radio. In addition to developing new profiles, other working groups are developing extensions to enhance Bluetooth operations. The radio working group is developing optional extensions to the current Bluetooth standard that include higher data rates and handoff capability to support roaming, and the coexistence working group is collaborating with the IEEE and working groups to address interference concerns and ensure that Bluetooth can coexist in the same environment with WLANs. 6. BLUETOOTH IS CHOSEN FOR VOICE COMMUNICATION As Bluetooth offers the ability to provide seamless voice and data connections to virtually all sorts of personal devices the human imagination is the only limit to application options. Beyond un-tethering devices by replacing the cables, this technology provides a universal bridge to existing data networks, allows users to form a small private ad hoc wireless network outside of fixed network infrastructures, enables users to connect to a wide range of computing and telecommunications devices easily and simply, without the need to buy, carry, or connect cables. The Bluetooth technology allows users to think about what they are working on, rather than how to make their technology work. The Internal Documents and Presentations (IDC) forecast in 2004, million devices in the United States and million devices worldwide would become Bluetooth enabled. 7. BLUETOOTH PICONETS Let's say you have a typical modern living room with typical modern stuff inside. There's an entertainment system with a stereo, a DVD player, a satellite TV receiver and a television; there's also a cordless telephone and a personal computer. Each of these systems uses Bluetooth, and each forms its own piconet to talk between the main unit and peripheral. The cordless telephone has one Bluetooth transmitter in the base and another in the handset. The manufacturer has programmed each unit with anaddress that falls into a range of addresses it has established for a particular type of device. When the base is first turned on, it sends radio signals asking for a response from any units with an address in a particular range. Since the handset has an address in the range, it responds, and a tiny network is formed. Now, even if one of these devices should receive a signal from another system, it will ignore it since it's not from within the network. The computer and entertainment system go through similar routines, establishing networks among addresses in ranges established by manufacturers. Once the networks are established, the systems begin talking among themselves. Each piconet hops randomly through the available frequencies, so all of the piconets are completely separated from one another. Now the living room has three separate networks established, each one made up of devices that know the address of transmitters it should listen to and the address of receivers it should talk to. Since each network is changing the frequency of its operation thousands of times a second, it's unlikely that any two networks will be on the same frequency at the same time. If it turns out that they are, then the resulting confusion will only cover a tiny fraction of a second, and software designed to correct for such errors weeds out the confusing information and gets on with the network's business. Fig 1 Piconet 8. BLUETOOTH SCATTERNET As with piconets, where multiple Bluetooth devices are able to connect with each other in an ad-hoc manner, so too can multiple piconets join together to form a larger network known as a scatternet. Bluetooth devices must have point-tomultipoint capability in order to engage in scatternet communication, and several piconets can be connected to each other through one scatternet. Furthermore, a single Bluetooth device may participate as a in several piconets, but can only be a master in one piconet. P1 P3 Fig 1.2 scatternet Maste Maste Master Figure 1.2 shows an example of a scatternet consisting of three separate piconets, P1, P2 and P3. Each piconet is controlled by a separate master and contains one or more s. P2 Maste

4 A scatternet is a number of interconnected piconets that supports communication between more than 8 devices. Scatternets can be formed when a member of one piconet (either the master or one of the s) elects to participate as a in a second, separate piconet. The device participating in both piconets can relay data between members of both adhoc networks. However, the basic bluetooth protocol does not support this relaying - the host software of each device would need to manage it. Using this approach, it is possible to join together numerous piconets into a large scatternet, and to expand the physical size of the network beyond Bluetooth's limited range. Scatternets have the potential to bring the interconnectivity of the Internet to the physical world through wireless devices. A number of companies have attempted to launch social networking and dating services that leverage early scatternet implementations. Scatternets can also be used to enable ad-hoc communication and interaction between autonomous robots and other devices. Most of the existing algorithms are based on essentially two scatternet topologies: Tree Topology (TTP) TTP assigns master/ roles to nodes while connecting them in a tree structure. Every bridge (internal node) performs the dual function of a in its parent s piconet and as a master in its children s piconet. Shared s Topology SST In shared s topology, the piconets share s, i.e. a frequently switches between member piconets and is active in only one of them at a time. The shared could either be a pure bridge ( in all member piconets) or alternates being a master and in its respective piconets.a variant of SST based scatternet topology called BlueRing has been proposed in [8], [9] which connects piconets as a circular ring interleaved by bridges between piconets. 9. HOW BLUETOOTH CAN BE USED FOR INTERCOM As we have discussed earlier Bluetooth is highly efficient device and provides robust in built security, it is a faster way to send data and voice over Bluetooth. Bluetooth is such a technology that is available with every handset, laptop table etc. For office environment Bluetooth communication can be easily possible. There are many industries where using phone call during work time is restricted. At time their handset or laptop or any other device can be act as Bluetooth communicator. For example a manager of finance department wants call manager of Human resource department so he can just send voice message over Bluetooth. This mechanism is very simple and effective. Today no handset or laptop prover provides voice communication feature over Bluetooth. may be because Bluetooth is freely available with every device now a days. 10. HOW CAN WE DEAL WITH BLUETOOTH S SMALL RANGE? Bluetooth technology was designed primarily to support simple wireless networking of personal consumer devices and peripherals, including cell phones, PDAs, and wireless headsets. Wireless signals transmitted with Bluetooth cover short distances, typically up to 30 feet (10 meters). Bluetooth devices generally communicate at less than 1 Mbps. So this question arises that if Bluetooth can be used for such a small range than how can we implement intercom with the help of Bluetooth. for such a small range we don t need any device for communication for any two person. But there is a concept for expanding Bluetooth range and network region as we have discussed earlier that is Bluetooth scatternet two or more piconents can be combine to establish Bluetooth network. For example a industry wants to built a mobile communicator which can be used for only industry s buildings as intercom. 11. BLUETOOTH SCATTERNET FORMATION The Bluetooth speciation enables the formation of a larger network from many nodes but it does not define an exact method for scatternet formation. There are only a few publications about how to form a scatternet which aspect must be taken into account and which methods must be used to connect the nodes. Bluetooth technology was originally optimized for establishing point-to-point connection between devices. The networking point of view requires to solve new problems. The standard Bluetooth address field is 3-bit long which enables the master to address its s. The can only transmit to its master. Due to this restricted addressing Bluetooth packets can only be forwarded in a single piconet. Each time when we want to forward a packet through many nodes we have to send the packet to the higher layers which decide where to send the packet. Differerent methods can be used to route the packets. The existing IP routing algorithms can be applied for the Bluetooth environment, however they were not designed for the ad hoc environment. In one single piconet the master decides which is allowed to send data in the next to master time slot. To determine which can transmit we must use a scheduling algorithm. With the scheduling procedure the master of a piconet determines when the s can transmit. This initiation is called polling. During the poll procedure the master sends poll packets to the s. 12. BLUETOOTH SECURITY Bluetooth security, when compared with WLAN security, is both more complex and simpler. It is more complex in the sense that there are many different options for security based on different application scenarios. It is simpler in the sense that, for the most part, they are transparent to the user.

5 With WLANs it is up to the network administrator to add security at higher levels. With Bluetooth, since the Bluetooth spec includes all levels, higher-level security features are already built into the devices when appropriate. Bluetooth security includes both authentication and confidentiality, and is based around the SAFER+ encryption algorithm. SAFER+ is a block cipher, but in this application is implemented as a stream cipher. SAFER+ was thoroughly analyzed and tested during the NIST s search for a national encryption standard. Although some versions were found to have very minor weaknesses, the 128-bit version as used in Bluetooth is considered very strong. Link layer security keys and more keys The Bluetooth Baseband (link layer) specification defines methods for both authentication and encryption that are subsequently utilized by higher layers. These methods utilize a number of keys generated by a process that begins with three basic device entities: a public 48-bit device address, a random number generator, and a secret PIN which is either built into the unit by the manufacturer or programmed by the user. A typical PIN may consist of just four decimal digits. However, for applications requiring more security a PIN code up to 128-bits long can be entered. The first of many keys is created the first time the Bluetooth device is installed on the host and is typically never changed. This is referred to as the unit key. Authentication When a Bluetooth session (defined as the time interval for which the device is part of a piconet) is initiated, a series of additional keys is generated. One of these keys, referred to as the link key or authentication key, is a one-time 128-bit secret key that is used only during that session. The process of authentication employs the encryption of a random number by each device to verify that each is sharing the same secret link key. Encryption If encryption is required by the application, an encryption key is further derived from the link key, a ciphering offset number, and a random number. While the authentication key is always 128-bits, the encryption key may be shorter to accommodate government restrictions on encryption, which vary from country to country. A new encryption key is generated each time the device enters encryption mode. The authentication key, however, is used during the entire session. Application layer security The Bluetooth General Access Profile defines three security modes: Mode 1 is non-secure. Authentication is optional. Mode 2 gives service-level enforced security. The service provided by the application decides whether or not authentication or encryption is required. The Bluetooth SIG has published the Bluetooth Security Architecture white paper5 that defines a suitable architecture for implementing service-level enforced security on Bluetooth devices. The white paper splits devices into different categories and trust levels, as well as suggesting three security levels for services. The utilization of a database is suggested for enabling the user to authorize devices to utilize only particular services. Because the implementation of security at this level does not affect interoperability. Mode 3 is link-level enforced security. Both devices must implement security procedures in order for a connection to be established. In addition to the above modes, a device can be configured to not respond to paging, so that other devices cannot connect to it. Or it can be configured so that only devices that already know its address can connect to it. Such numerous and complex levels of security are necessary to accommodate the large variety of different usage scenarios. It falls on the designers of Bluetooth products to ensure that the complexity of Bluetooth is hidden from the user, while still providing the user with necessary security options. 13. HYPOTHESIS As explained we can demonstrate Bluetooth scatternet and can use our any PDA or laptop as mobile intercom device to communicate with each other. The following elements are needed: Master transmitter, Radio channel IEEE b interferer receiver, Bit error rate (BER) display Instrumentation. The transmitter subsystem performs speech coding, buffering, framing, header error control (HEC), forward error correction (FEC), GFSK modulation, and frequency hopping. Channel effects modeled include thermal noise, path loss and interference. The Free Space Path Loss block, from the RF Impairments library, models path loss. The IEEE b interferer is a masked subsystem that opens up a mask dialog for user input on double-clicks. Mean packet rate, packet length, power and frequency location in the ISM band can be specified in the mask dialog. The Receiver recovers speech from the transmitted signal, performing all the complementary operations that the transmitter does, but in reverse order THE IMPLEMENTATION For Bluetooth communicator following is needed Hardware

6 Bluetooth network Front end Frond end should be there for every device which contains contact information for every device. It must add new contact or delete unwanted contact. It must have facility to accept call and reject it. If a user wants to set up call to any of the contact than there should be mechanism to select that contact and set up the call. Device should also have interpreter to convert the signal into voice and voice to signal. The scatternet formation should be there so that higher range is provided. There are two kinds of connection for Bluetooth Asynchronization Connectionless (ACL) Link and Synchronous Connection oriented (SCO) Link. If the bluetooth network connection is implemented as ACL then both user can transmit at a time, but if it is implemented as SCO link then only one user send voice and other end s user has to wait. But for voice communication SCO link is more feasible, it provides QoS feature also. The receiver device receives Bluetooth address to setup the call, then Bluetooth module establish the connection. Once its established sender s address is sent. The network layer is responsible for sending voice packets from the sender to receiver. Network layer establish the Bluetooth address of the device and multicast it so that other devices can have address for communication. At receiver s side pop up message arrives Bluetooth address of the sender and voice message. 14. CONCLUSIONS Need of communication at every point has become vital, we need to have in touch at every time that s why we required easy and cheap way for communication. This paper introduce Bluetooth voice transmission technology which provides mobile, robust and highly secured technology which can be act as intercom. ACKNOWLEDGMENT I would like to thank my guide Mr. ARUN DALVI, who guided me to prepare my documentation. REFERENCES [1]. of the Bluetooth System, December 1st [2]. Scatternet - Part 1 Baseband vs. Host Stack Implementation White paper, Ericsson Technology Licensing June 2004 [3]. Wikipedia, the free encyclopedia [4]. Understanding Bluetooth January 2002 [5] How stuff worksbluetooth