ABSTRACT:
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????????????????????? ?Bluetooth technology eliminates the need for numerous and inconvenient cable attachments for connecting fixed computers, mobile phones, mobile computers, handheld devices, digital cameras and even new breed of digital appliances. It delivers opportunities for rapid ad hoc connections, and the possibility of automatic, unconscious, connections between devices. It creates the possibility of using mobile data in a variety of applications.
?????????????????????? However, we believe that the most compelling application for Bluetooth is the always-on Internet access at homes, offices, and public locations through a Bluetooth Internet Access Point. Pico Communications Inc. develops such Bluetooth Internet Access Point products for the home, office, and public locations where users can access Internet with their Bluetooth-enabled notebook, PDA, or Smart Phone.
????????????????????? The main objective of this paper presentation is to know about the Bluetooth technology and Bluetooth internet access point based on LAN access profile
INTRODUCTION:
???????????????? Bluetooth wireless technology is a worldwide industry standard that enables point-to-multipoint, low-power, wireless connectivity between PCs, PDAs, mobile phones and other portable devices and connections from those devices to the LAN and Internet. The Bluetooth Special Interest Group (SIG) includes promoter companies such as 3Com, Ericsson, IBM, Intel, Lucent, Microsoft, Motorola, Nokia and Toshiba, and over 2800 other adopter/associate member companies.
?????? ??????????????Bluetooth operates in the license-free 2.4GHz ISM band at a link range of 10 meters. With improved transmission power and receiving sensitivity the range can be increased up to 100 meters. Bluetooth is expected to be a standard feature on the next generation Smart Phones, PDAs and computers
??????????? ????????Bluetooth wireless technology is revolutionizing personal connectivity by providing freedom from wired connections.? Bluetooth is also revolutionizing wireless networking by providing stronger security, better resistance to interference and longer battery life than other wireless technologies. These features, in combination with the lower costs of Bluetooth technology, make it the ideal solution for handheld wireless networking.
????????? ?????????With a Bluetooth handheld, you can connect to your information where you want, when you want. Whether you're managing your schedule, accessing email, or sending an instant message to a friend, Bluetooth technology allows you to take advantage of the best network available at the time. When out of the office, you can use your handheld to connect to a wide area data network through your Bluetooth-enabled mobile phone. Or you can connect at your local Bluetooth "hot spot." In the office, you can switch to Pico's Bluetooth local area network to get even faster speeds with no airtime charges.Bluetooth technology allows you to connect from anywhere and that means you can do more with your life.
BASICS OF BLUETOOTH:
??? ?????????????Bluetooth is short-range radio technologies that enable wireless connectivity between mobile devices. Design-wise, the three main goals for Bluetooth were: small size, minimal power consumption, and low price. The technology was designed to be simple, and the target was to have it become a de facto standard in wireless connectivity. Bluetooth radio operates in the unlicensed ISM band at 2.4 GHz .In some countries, this band is reserved for military use, but these countries have now begun freeing that band for general use. The maximum gross data rate is 1 Mbps. The range of Bluetooth depends on the power class of the radio. Most devices are expected to use the class 2 radio that provides 0 dBm nominal output power, resulting in a range of up to 10 meters in an obstacle-free environment. This range is sufficient for cable-replacement applications. When a longer range is needed (e.g., in access points), a more powerful radio (class 1) can be used. Larger power consumption is not a problem if the device is a piece of fixed equipment. With mobile devices such as mobile phones, power-consumption issues are crucial and therefore class 2 is the only feasible option.
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Bluetooth system blocks: The Bluetooth system consists of a radio unit, a link control unit, and a support unit for link management and host terminal interface functions (see Figure 1). The Host Controller Interface (HCI) provides the means for a host device to access Bluetooth hardware capabilities. For example, a laptop computer could be the host device and a PC card inserted in the PC is the Bluetooth device. All commands from the host to the Bluetooth module and events from the module to the host go through the HCI interface. The protocol stack is above the radio and base band hardware, partly residing in the Bluetooth unit and partly in the host device. A Bluetooth solution can also be implemented as a one-processor architecture (embedded solution) where the application resides together with the Bluetooth protocols in the same hardware. In that case, the HCI is not needed. This is a feasible implementation for simple devices such as accessories or micro servers.
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BLUETOOTH TECHNOLOGY
?Piconet and Scatternet: The Bluetooth network is called a piconet. In the simplest case it means that two devices are connected (see Figure 2a). The device that initiates the connection is called a master and the other devices are called slaves. The majority of Bluetooth applications will be point-to-point applications. Bluetooth connections are typically ad hoc connections, which mean that the network will be established just for the current task and then dismantled after the data transfer has been completed. A master can have simultaneous connections (point-to-multipoint) to up to seven slaves (see Figure 2b). Then, however, the data rate is limited. One device can also be connected in two or more piconets. The set-up is called scatternet (see Figure 2c).
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Implementation of Bluetooth:
A typical implementation of Bluetooth includes the RF, baseband, HCI interface, and host stacks software.???????? ??????????????????????????????????????????
RF:
Bluetooth operates in the license-free 2.4-2.4835GHz ISM band by frequency hopping at a rate of 1600 hops/s within 79 1MHz channels. Japan, France and Spain have a smaller band but these issues are being resolved. Bluetooth supports 10-meter range and 1Mbps rate and a 100-meter range with improved transmission power and receiving sensitivity.
There are three classes of transmit power for Bluetooth: Class 3 at 0 dBm (1 mW), Class 2 at 4 dBm (2.5 mW) and Class 1 at 20 dBm (100 mW). The minimum receiver sensitivity level is -70 dBm (but most products are between ?75dBm and ?90dBm) for 10-3 BER.
?BASEBAND:
A wireless PAN, more often referred to as a Piconet, provides the cable replacement for connectivity among various devices such as a notebook PC to a cell phone, a cell phone to a headset, a PDA to a notebook, a cell phone to PSTN, a notebook/PDA to Internet and LAN, and other ad-hoc networking applications. Multiple devices (256 parked, 8 active) can participate in a Piconet.
Bluetooth communications in a Piconet is based on a master/slave relationship, where one unit serves as a master and the rest serve as slaves. The access is synchronized via master identity whose Bluetooth address determines the frequency hopping sequence and system clock determines the phase. Each slave will follow the hop sequence and add an offset to its clock to follow the master. Each Bluetooth packet has a fixed format that starts with a 72-bit access code that is based on the master identity and is unique to the Piconet. Then a 54-bit header containing error correction, retransmission and control information follows. Finally, a payload of 0 to 2745 bits ends a packet.
Figure-3 master to slave connection in a piconet
Frequency hopping:
Bluetooth uses frequency hopping, at 1600 hops/s, among 79 one MHz channels at 1 bit/symbol GFSK. To provide full duplex operation, it uses Time-Division Duplex (TDD) scheme to divide the channel into a number of 625 us time slots with a 220 us TDD guard time. Master and slave alternatively transmit. The master shall transmit in even-numbered time slot only while the slave shall start its transmission in odd numbered time slots. The time slots are numbered based on the Bluetooth clock of the piconet master. The numbering ranges from 0 to (2^27 ?1) and is cyclic with a cycle length of 2^27.
Bluetooth protocol is a combination of circuit and packet switching. Reservation of slots can be made for Synchronous Connection-Oriented (SCO) links for circuit switching audio application. Bluetooth can support three 64Kbps voice channels. It also supports an Asynchronous Connection-Less (ACL) link for packet data switching, based on a polling access scheme. Typical packet size is one slot but can span multiple slots as defined in the specification. Bluetooth provides maximum data rate of asymmetrical 721 Kb/s upstream (57.6Kb/s downstream), or symmetrical 432.6 kb/s data transfer rate.
The master controls all traffic in a Piconet. It allocates capacity for SCO links and handles the polling scheme for ACL links among slaves. Slave may only send in the slave-to-master slot after being addressed in the preceding master-to-slave slot. Figure-1 illustrates master-to-slaves connection in a Piconet.
Bluetooth supports authentication and encryption, combining with frequency hopping, to give the technology the robust security. Three entities are used, a 48-bit Bluetooth address, 64-bit private user key, and a 128-bit RAND. The link level security of each pair of Bluetooth devices in a connection is based on a secret 128-bit random number link key that is used for authentication and encryption. For error correction, Bluetooth uses Forward-Error Correction (FEC) including 1/3 rate, 2/3 rate and ARQ scheme for data
HCI INTERFACE:
The Host Controller Interface, HCI, provides a uniform interface method for accessing the Bluetooth hardware capabilities. It contains a command interface to the Based band controller and link manager and access to hardware status. Typical connection w/standard interfaces include USB, UART, and PCMCIA.
HOST PROTOCOL STACK:
Protocols are needed to implement different profiles and usage models. Every profile uses at least part of the protocol stack. In order to achieve interoperability between two Bluetooth devices, they both must have the same vertical profile of the protocol stack. The Bluetooth protocol stack is depicted in Figure 4.
Figure-4?? Bluetooth protocol stack
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BLUETOOTH CORE PROTOCOLS:
?Base band and Link Control together enable a physical RF link between Bluetooth units forming a piconet. This layer is responsible for synchronizing the transmission-hopping frequency and clocks of different Bluetooth devices.
Link Manager Protocol (LMP): is responsible for link set-up (authentication and encryption, control, and negotiation of base band packets) between Bluetooth devices and for power modes and connection states of a Bluetooth unit. Logical Link Control and Adaptation Protocol (L2CAP) take care of multiplexing, reassembly, and segmentation of packets.
Service Discovery Protocol (SDP): is needed when requesting device information, services, and the characteristics of other devices. Devices have to support the same service in order to establish a connection with each other.
Cable Replacement Protocol:
RFCOMM emulates RS-232 signals and can thus be used in applications that were formerly implemented with a serial cable (e.g., a connection between a laptop computer and a mobile phone).
Telephony Protocol:
Telephony Control Protocol ? Binary (TCS-BIN): defines the call control signaling for the establishment of speech and data call between Bluetooth devices. AT commands provide means for controlling a mobile phone or a modem.
Adopted Protocols:
?OBEX (Object Exchange): is adopted from IrDA. It is a session protocol that provides means for simple and spontaneous object and data transfer. It is independent of the transport mechanism and transport Application Programming Interface (API).
TCP/UDP/IP is defined to operate in Bluetooth units allowing them to communicate with other units connected, for instance, to the Internet. The TCP/IP/PPP protocol configuration is used for all Internet Bridge usage scenarios in Bluetooth 1.0 and for OBEX in future versions. The UDP/IP/PPP configuration is available as transport for WAP.
Point-to-point protocol (PPP):
?PPP in the Bluetooth technology is designed to run over RFCOMM to accomplish point-to-point connections. PPP is a packet-oriented protocol and must therefore use its serial mechanisms to convert the packet data stream into a serial data stream.
?Wireless Application Protocol (WAP): The stack can reside on top of RFCOMM (based on LAN Access Profile) or on top of L2CAP (based on PAN Profile). The latter reduces overhead and is likely to become the preferred solution for WAP over Bluetooth. In Figure 4, a LAN Access Profile-based implementation is depicted. Wireless Application Environment (WAE) hosts the WAP browser environments.
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BLUETOOTH PROFILES:
The Bluetooth Special Interest Group (SIG) has defined a number of usage models for Bluetooth technology. They describe the main Bluetooth applications and the intended devices, e.g., the synchronization between a handheld device and a PC, and connecting to the Internet wirelessly using a mobile phone or a cordless modem. Profiles specify how the interoperable solution for the functions described in the usage models is provided; in other words, a profile defines the protocols and protocol features supporting a particular usage model. Bluetooth profiles are shown in Figure 5. Some profiles are dependent on other profiles. For example, three profiles (File Transfer Profile, Object Push Profile, and Synchronization Profile) are dependent on the Generic Object Exchange Profile. All profiles are dependent on the Generic Access Profile, i.e., they are reusing it.
The usage models have gradually lost their significance and it is more illustrative to talk about corresponding profiles. Thus, usage models have been omitted here and the emphasis is on profiles.
Bluetooth products support different sets of profiles. In order to support a certain profile, mandatory features of the profile must be implemented.
Figure-5 Bluetooth profile dependencies
The Four General Profiles in the Bluetooth Specification:
Generic Access Profile: defines the generic procedures related to discovery of Bluetooth devices (idle mode procedures) and link management aspects of connecting to Bluetooth devices (connecting mode procedures). It also defines procedures related to use of different security levels. In addition, this profile includes common format requirements for parameters accessible on the user interface level. Every Bluetooth device has to support the Generic Access Profileorum.Nokia.com
Service Discovery Application Profile: defines the features and procedures for an application in a Bluetooth device to discover services of another Bluetooth device.
?Serial Port Profile: defines the requirements for Bluetooth devices necessary for setting up emulated serial cable connections using RFCOMM between two peer devices.
Generic Object Exchange Profile: defines the protocols and procedures that will be used by applications that need object exchange capabilities. Possible scenarios are synchronization, file transfer, and object push.
LAN Access Profile: defines how Bluetooth-enabled devices can access the services of a local-area network using PPP (Point-To-Point Protocol) over RFCOMM (Bluetooth protocol that emulates RS-232 signal) and how the same PPP mechanisms are used to form a network consisting of two Bluetooth-enabled devices.
BLUETOOTH INTERNET ACCESS POINT BASED ON LAN ACCESS PROFILE:
?????????? The LAN Access Point (LAP) is a Bluetooth connectivity device that provides PPP server function for access to a LAN (Ethernet, Token Ring, Cable Modem, DSL, Firewire, USB or Home Networking).
Figure 4 shows a typical protocol stack communication between a Data Terminal (DT) and LAP. Both the LAP and the DT must enforce encryption that is operating on the baseband and physical link while any PPP traffic is being sent or received. Bluetooth pairing occurs as a means of authenticating the users. A PIN or link key must be supplied.
Figure-6?? Protocol for LAN access point to data terminal
???????????? The PPP connection is carried over RFCOMM to transport the PPP packet and it can be used for flow control of the PPP data stream. The assumption for the DT is that it is a PPP client that forms a PPP connection with a LAP in order to access a LAN.
A single DT uses a LAP as a wireless means of connecting to a LAN. Once connected, the DT will operate as if it were connected to the LAN via dial-up networking and access all of the services provided by the LAN. Multiple DTs can also use the LAP via dial-up networking and communicate with each other via the LAP.
BLUETOOTH INTERNET ACCESS POINT:
?????????? Figure 7 shows a Bluetooth Internet Access Point. Within the coverage area of the device, the access point serves as a wireless to wire-line gateway to the Internet. Any standard Bluetooth-enabled device that is a PPP client can connect to any access point that meets the LAP profile. After connection, these clients could use a standard HTML or WML browser forviewingWebor WAP content.
Figure-7 Bluetooth internet access point
We believe that the following features are important for a Bluetooth Internet Access Point based on LAP:
CONCLUSION:
Designed as a cable-replacement technology, Bluetooth wireless technology is well suited to the connectivity requirements of WPANs composed of portable computers, PDAs, mobile phones, and printers. It is ideally suited to mobile devices (particularly PDAs) because of their small size, low power requirements, and applications (mobile phone wireless WAN connectivity, peer-to-peer business card or calendar exchange, and wireless synchronization). As the technology matures, implementations increase, and native operating system support becomes available, interoperability and ease-of-use issues should diminish. Dell is committed to providing Bluetooth solutions that meet customer needs, have been thoroughly tested for compliance, and coexist with Wi-Fi networks.
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