ABSTRACT:
Third Generation (3G) mobile devices and services will transform wireless communications in to on-line, real-time connectivity. 3G wireless technology will allow an individual to have immediate access to location-specific services that offer information on demand. The first generation of mobile phones consisted of the analog models that emerged in the early 1980s. The second generation of digital mobile phones appeared about ten years later along with the first digital mobile networks. During the second generation, the mobile telecommunications industry experienced exponential growth both in terms of subscribers as well as new types of value-added services. Mobile phones are rapidly becoming the preferred means of personal communication, creating the world's largest consumer electronics industry.
The rapid and efficient deployment of new wireless data and Internet services has emerged as a critical priority for communications equipment manufacturers. Network components that enable wireless data services are fundamental to the next-generation network infrastructure. Wireless data services are expected to see the same explosive growth in demand that Internet services and wireless voice services have seen in recent years.
This white paper presents an overview of current technology trends in the wireless technology market, a historical overview of the evolving wireless technologies and an examination of how the communications industry plans to implement 3G wireless technology standards to address the growing demand for wireless multimedia services. We also show the differences between third generation wireless technology when compared to different wireless technologies.
3G Wireless Market Drivers:
Telecommunications service providers and network operators are embracing the recently adopted global third generation (3G) wireless standards in order to address emerging user demands and to provide new services. The concept of 3G wireless technology represents a shift from voice-centric services to multimedia-oriented (voice, data, video, fax) services. In addition, heavy demand for remote access to personalized data is fueling development of applications, such as the Wireless Application Protocol (WAP) and multimedia management, to complement the 3G protocols. Complementary standards, such as Bluetooth, will enable interoperability between a mobile terminal (phone, PDA etc.) and other electronic devices, such as a laptop/desktop and peripherals, providing added convenience to the consumer and allowing for the synchronization and uploading of information at all times. According to Lehman Brothers, approximately 50 percent of current voice services subscribers are expected to use wireless data services by 2007, instead of 25 percent as previously forecast1. Lehman Brothers further predicts that, within seven years, 18 percent of cellular revenues and 21 percent of PCS (personal communications services) revenue will come from wireless data services. Cellular subscriptions are forecast to exceed one billion by 20032, compared with the 306 million that was forecast at the end of 1998, representing a compound annual growth of 29 percent. Demand for voice services has traditionally been a market driver. However, today, demand for data services has emerged as an equally significant market driver. After many years of stasis, the telecommunications industry is undergoing revolutionary changes due to the impact of increased demand for data services on wireline and wireless networks. Up until recently, data
traffic over mobile networks remained low at around 2% due to the bandwidth limitations of the present second-generation (2G) wireless networks. Today, new technologies are quickly emerging that will optimize the transport of data services and offer higher bandwidth in a mobile environment. As a case in point, the increased use of the Internet as an acceptable source for information distribution and retrieval, in conjunction with the increased demand for global mobility has created a need for 3G wireless communications protocols.
The third generation of mobile communications will greatly enhance the implementation of sophisticated wireless applications. Users will be able to utilize personal, location-based wireless information and interactive services. Also, many companies and corporations are restructuring their business processes to be able to fully exploit the opportunities provided by the emerging new wireless data services. Many advanced wireless services are already available today, and the introduction of 3G wireless technologies will add to their ubiquity.
Generation First Wireless Technology:
The first generation of wireless mobile communications was based on analog signalling. Analog systems, implemented in North America, were known as Analog Mobile Phone Systems (AMPS), while systems implemented in Europe and the rest of the world were typically identified as a variation of Total Access Communication Systems (TACS). Analog systems were primarily based on circuit-switched technology and designed for voice, not data.
Second Generation Wireless Technology:
The second generation (2G) of the wireless mobile network was based on low-band digital data signalling. The most popular 2G wireless technology is known as Global Systems for Mobile Communications (GSM). GSM systems, first implemented in 1991, are now operating in about 140 countries and territories around the world. An estimated 248 million users now operate over GSM systems. GSM technology is a combination of Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA). The first GSM systems used a 25MHz frequency spectrum in the 900MHz band. FDMA is used to divide the available 25MHz of bandwidth into 124 carrier frequencies of 200kHz each. Each frequency is then divided using a TDMA scheme into eight timeslots. The use of separate timeslots for transmission and reception simplifies the electronics in the mobile units. Today, GSM systems operate in the 900MHz and 1.8 GHz bands throughout the world with the exception of the Americas where they operate in the 1.9 GHz band. In addition to GSM, a similar technology, called Personal Digital Communications (PDC), using TDMA-based technology, emerged in Japan. Since then, several other TDMA-based systems have been deployed worldwide and serve an estimated 89 million people worldwide. While GSM technology was developed in Europe, Code Division Multiple Access (CDMA) technology was developed in North America. CDMA uses spread spectrum technology to break up speech into small, digitized segments and encodes them to identify each call. CDMA systems have been implemented worldwide in about 30 countries and serve an estimated 44 million subscribers. While GSM and other TDMA-based systems have become the dominant 2G wireless technologies, CDMA technology is recognized as providing clearer voice quality with less background noise, fewer dropped calls, enhanced security, greater reliability and greater network capacity. The Second Generation (2G) wireless networks mentioned above are also mostly based on circuit-switched technology. 2G wireless networks are digital and expand the range of applications to more advanced voice services, such as Called Line Identification. 2G wireless technology can handle some data capabilities such as fax and short message service at the data rate of up to 9.6 kbps, but it is not suitable for web browsing and multimedia applications.
Next Generation Mobile Networks:
Second Generation (2G+) Wireless Networks: As stated in a previous section, the virtual explosion of Internet usage has had a tremendous impact on the demand for advanced wireless data communication services. However, the effective data rate of 2G circuit-switched wireless systems is relatively slow -- too slow for today's Internet. As a result, GSM, PDC and other TDMA-based mobile system providers and carriers have developed 2G+ technology that is packet-based and increases the data communication speeds to as high as 384kbps. These 2G+ systems are based on the following technologies: High Speed Circuit-Switched Data (HSCSD), General Packet Radio Service (GPRS) and Enhanced Data Rates for Global Evolution (EDGE) technologies. HSCSD is one step towards 3G wideband mobile data networks. This circuit-switched technology improves the data rates up to 57.6kbps by introducing 14.4 kbps data coding and by aggregating 4 radio channels timeslots of 14.4 kbps. GPRS is an intermediate step that is designed to allow the GSM world to implement a full range of Internet services without waiting for the deployment of full-scale 3G wireless systems. GPRS technology is packet-based and designed to work in parallel with the 2G GSM, PDC and TDMA systems that are used for voice communications and for table look-up to obtain GPRS user profiles in the Location Register databases. GPRS uses a multiple of the 1 to 8 radio channel timeslots in the 200kHz-frequency band allocated for a carrier frequency to enable data speeds of up to 115kbps. The data is packetized and transported over Public Land Mobile Networks (PLMN) using an IP backbone so that mobile users can access services on the Internet, such as SMTP/POP-based e-mail, ftp and HTTP-based Web services. EDGE technology is a standard that has been specified to enhance the throughput per timeslot for both HSCSD and GPRS. The enhancement of HSCSD is called ECSD, whereas the enhancement of GPRS is called EGPRS. In ECSD, the maximum data rate will not increase from 64 kbps due to the restrictions in the A interface, but the data rate per timeslot will triple. Similarly, in EGPRS, the data rate per timeslot will triple and the peak throughput, including all eight timeslots in the radio interface, will exceed 384 kbps.
GPRS networks consist of an IP-based Public Mobile Land Network (PLMN), Base Station Services (BSS), Mobile handsets (MS), and Mobile Switching Centers (MSC) for circuit-switched network access and databases. The Serving GPRS Support Nodes (SGSN) and Gateway GPRS Support Nodes (GGSN) make up the PLMN. Roaming is accommodated through multiple PLMNs. SGSN and GGSN interface with the Home Location Register (HLR) to retrieve the mobile user's profiles to facilitate call completion. GGSN provides the connection to external Packet Data Network (PDN), e.g. an Internet backbone or an X.25 network. The BSS consists of Base Transceiver Stations and Base Station Controllers. The Base Transceiver Station (BTS) receives and transmits over the air interfaces (CDMA, TDMA), providing wireless voice and data connectivity to the mobile handsets. Base Station Controllers (BSC) route the data calls to the packet-switched PLMN over a Frame Relay (FR) link and the voice calls to the Mobile Switching Center (MSC). MSC switches the voice calls to circuit-switched PLMN network such as PSTN and ISDN. MSC accommodates the Visitor Location Register (VLR) to store the roaming subscriber information. The reverse process happens at the destination PLMN and the destination BSS. On the data side, the BSC routes the data calls to the SGSN, and then the data is switched to the external PDN through the GGSN or to another mobile subscriber.
The following is a brief description of each protocol layer in the GPRS network infrastructure: Sub-Network Dependent Convergence Protocol (SNDCP): protocol that maps a network level protocol, such as IP or X.25, to the underlying logical link control. SNDCP also provides other functions such as compression, segmentation and multiplexing of network-layer messages to a single virtual connection. Logical Link Control (LLC): a data link layer protocol for GPRS which functions similar to Link Access Protocol – D (LAPD). This layer assures the reliable transfer of user data across a wireless network. Base Station System GPRS Protocol (BSSGP): processes routing and quality of service (QoS) information for the BSS. BSSGP uses the Frame Relay Q.922 core protocol as its transport mechanism. GPRS Tunnel Protocol (GTP): protocol that tunnels the protocol data units through the IP backbone by adding routing information. GTP operates on top of TCP/UDP over IP.
the protocols used in BTS, BSC, SGSN, GGSN, and mobile handsets:
GPRS Mobility Management (GMM/SM): protocol that operates in the signalling plane of GPRS, handles mobility issues such as roaming, authentication, selection of encryption algorithms and maintains PDP context. Network Service: protocol that manages the convergence sub-layer that operates between BSSGP and the Frame Relay Q.922 Core by mapping BSSGP's service requests to the appropriate Frame Relay services. BSSAP+: protocol that enables paging for voice connections from MSC via SGSN, thus optimizing paging for mobile subscribers. BSSAP+ is also responsible for location and routing updates as well as mobile station alerting. SCCP, MTP3, MTP2 are protocols used to support Mobile Application Part (MAP) and BSSAP+ in circuit switched PLMNs. Mobile Application Part (MAP): supports signaling between SGSN/GGSN and HLR/AuC/EIR.
Third Generation (3G) Wireless Networks:
3G wireless technology represents the convergence of various 2G wireless telecommunications systems into a single global system that includes both terrestrial and satellite components. One of the most important aspects of 3G wireless technology is its ability to unify existing cellular standards, such as CDMA, GSM, and TDMA, under one umbrella. The following three air interface modes accomplish this result: wideband CDMA, CDMA2000 and the Universal Wireless Communication (UWC-136) interfaces. Wideband CDMA (W-CDMA) is compatible with the current 2G GSM networks prevalent in Europe and parts of Asia. W-CDMA will require bandwidth of between 5Mhz and 10 Mhz, making it a suitable platform for higher capacity applications. It can be overlaid onto existing GSM, TDMA (IS-36) and IS95 networks. Subscribers are likely to access 3G wireless services initially via dual band terminal devices. W-CDMA networks will be used for high-capacity applications and 2G digital wireless systems will be used for voice calls. The second radio interface is CDMA2000 which is backward compatible with the second generation CDMA IS-95 standard predominantly used in US. The third radio interface, Universal Wireless Communications – UWC-136, also called IS-136HS, was proposed by the TIA and designed to comply with ANSI-136, the North American TDMA standard. 3G wireless networks consist of a Radio Access Network (RAN) and a core network. The core network consists of a packet-switched domain, which includes 3G SGSNs and GSNs, which provide the same functionality that they provide in a GPRS system, and a circuit-switched domain, which includes 3G MSC for switching of voice calls. Charging for services and access is done through the Charging Gateway Function (CGF), which is also part of the core network. RAN functionality is independent from the core network functionality. The access network provides a core network technology independent access for mobile terminals to different types of core networks and network services. Either core network domain can access any appropriate RAN service; e.g. it should be possible to access a “speech” radio access bearer from the packet switched domain. The Radio Access Network consists of new network elements, known as Node B and Radio Network Controllers (RNCs). Node B is comparable to the Base Transceiver Station in 2G wireless networks. RNC replaces the Base Station Controller. It provides the radio resource management, handover control and support for the connections to circuit-switched and packet-switched domains. The interconnection of the network elements in RAN and between RAN and core network is over Iub, Iur and Iu interfaces based on ATM as a layer 2 switching technology. Data services run from the terminal device over IP, which in turn uses ATM as a reliable transport with QoS. Voice is embedded into ATM from the edge of the network (Node B) and is transported over ATM out of the RNC. The Iu interface is split into 2 parts: circuitswitched and packet-switched. The Iu interface is based on ATM with voice traffic embedded on virtual circuits using AAL2 technology and IP-over-ATM for data traffic using AAL5 technology. These traffic types are switched independently to either 3G SGSN for data or 3G MSC for voice.
The following is a brief description of each protocol layer in a 3G wireless network infrastructure:
Global Mobility Management (GMM): protocol that includes attach, detach, security, and routing area update functionality. Node B Application Part (NBAP): provides procedures for paging distribution, broadcast system information and management of dedicated and logical resources. Packet Data Convergence Protocol (PDCP): maps higher level characteristics onto the characteristics of the underlying radio-interface protocols. PDCP also provides protocol transparency for higher layer protocols
PDCP also provides protocol transparency for higher layer protocols. Radio Link Control (RLC): provides a logical link control over the radio interface. Medium Access Control (MAC): controls the access signaling (request and grant) procedures for the radio channel. Radio resource Control (RRC): manages the allocation and maintenance of radio communication paths.
Radio Access Network Application Protocol (RANAP): encapsulates higher layer signaling. Manages the signaling and GTP connections between RNC and 3G-SGSN, and signaling and circuit-switched connections between RNC and 3G MSC. Radio Network Service Application Part (RNSAP): provides the communication between RNCs. GPRS Tunnel Protocol (GTP): protocol that tunnels the protocol data units through the IP backbone by adding routing information. GTP operates on top of TCP/UDP over IP. Mobile Application Part (MAP): supports signaling between SGSN/GGSN and HLR/AuC/EIR. AAL2 Signaling (Q.2630.1, Q.2150.1, Q.2150.2, AAL2 SSSAR, and AAL2 CPS): protocols suite used to transfer voice over ATM backbone using ATM adaptation layer 2. Sigtran (SCTP, M3UA): protocols suite used to transfer SCN signaling protocols over IP network.
Evolution to 3G Wireless Technology:
Initial coverage Initially, 3G wireless technology will be deployed as "islands" in business areas where more capacity and advanced services are demanded. A complete evolution to 3G wireless technology is mandated by the end of 2000 in Japan (mostly due to capacity requirements) and by the end of 2001 in Europe. NTT DoCoMo is deploying 3G wireless services in Japan in the third quarter of 2000. In contrast, there is no similar mandate in North America and it is more likely thatcompetition will drive the deployment of 3G wireless technology in that region. For example, Nextel Communications has announced that it will be deploying 3G wireless services in North America during the fourth quarter of 2000. The implementation of 3G wireless systems raises several critical issues, such as the successful backward compatibility to air interfaces as well as to deployed infrastructures. Interworking with 2G and 2G+ Wireless Networks The existence of legacy networks in most regions of the world highlights the challenge that communications equipment manufacturers face when implementing next-generation wireless technology.Compatibility and interworking between the new 3G wireless systems and the old legacy networks must be achieved in order to ensure the acceptance of new 3G wireless technology by service providers and end-users.
The existing core technology used in mobile networks is based on traditional circuit-switched technology for delivery of voice services. However, this traditional technology is inefficient for the delivery of multimedia services. The core switches for next-generation of mobile networks will be based on packet-switched technology which is better suited for data and multimedia services. Second generation GSM networks consist of BTS, BSC, MSC/VLR and HLR/AuC/EIR network elements. The interfaces between BTS, BSC and MSC/VLR elements are circuit-switched PCM. GPRS technology adds a parallel packet-switched core network. The 2G+ network consists of BSC with packet interfaces to SGSN, GGSN, HLR/AuC/EIR. The interfaces between BSC and SGSN network elements are either Frame Relay and/or ATM so as to provide reliable transport with Quality of Service (QoS). 3G wireless technology introduces new Radio Access Network (RAN) consisting of Node B and RNC network elements. The 3G Core Network consists of the same entities as GSM and GPRS: 3G MSC/VLR, GMSC, HLR/AuC/EIR, 3G-SGSN, and GGSN. IP technology is used end-to-end for multimedia applications and ATM technology is used to provide reliable transport with QoS. 3G wireless solutions allow for the possibility of having an integrated network for circuit-switched and packet-switched services by utilizing ATM technology. The BSC may evolve into an RNC by using add-on cards or additional hardware that is co-located. The carrier frequency (5Mhz) and the bands (2.5 to 5Ghz) are different for 3G wireless technology compared to 2G/2G+ wireless technology. Evolution of BSC to RNC requires support for new protocols such as PDCP, RRC, RANAP, RNSAP and NBAP. Therefore, BTS' evolution into Node B may prove to be difficult and may represent significant capital expenditure on the part of network operators. MSC evolution depends on the selection of a fixed network to carry the requested services. If an ATM network is chosen, then ATM protocols will have to be supported in 3G MSC along with interworking between ATM and existing PSTN/ISDN networks. The evolution of SGSN and GGSN to 3G nodes is relatively easier. Enhancements to GTP protocol and support for new RANAP protocol are necessary to support 3G wireless systems. ATM protocols need to be incorporated to transport the services. The HLR databases evolve into 3G-HLR by adding 3G wireless user profiles. The VLR database must also be updated accordingly. The EIR database needs to change to accommodate new equipment that will be deployed for 3G wireless systems. Finally, global roaming requires compatibility to existing deployment and graceful fallback to an available level when requested services are not available in the region. Towards this end, the Operator Harmonization Group (OHG) is working closely with 3G Partnership Projects (3GPP and 3GPP2) to come up with global standards for 3G wireless protocols.
Comparison of 2G and 3G Mobile Networks:
As mentioned above, although there are many similarities between 2G and 3G wireless networks (and many of the 2G and 3G components are shared or connected through interworking functions), there are also many differences between the two technologies. Table 1 compares the differences between the core network, the radio portion and other areas of the two networks.
REFERENCES:
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NATIONALWIDE WIRELESS.NET
BLUETOOTH TECHNOLOGY IN WIRELESS COMMUNICATIONS
Abstract:
“Imagine the world with out wires and cables. Is this possible? Yes this can be possible with the implementation of a new technology in wireless communication called BLUETOOTH TECHNOLOGY.”
Bluetooth is a method for data communication that used short-range radio links to replace cables between computers and their connected units. Industry-wide Bluetooth promises very substantial benefits for wireless network operations, end workers and content developers of exciting new applications. This article delves into the implementation and architecture of Bluetooth. It also describes the functional overview and applications of Bluetooth, and deals with the development of a model for recording, printing, monitoring, and controlling of eight process variables at the same time, using a distributed control system. We explain industrial automation via Bluetooth using IISS. Industrial automation is one of the major applications of Bluetooth technology. Industrial automation, in terms of controlling or monitoring a factory. Office or industrial process means to install machines that can do the work instead of human workers. Industrial plants consists of many devices interconnected in different ways ranging from simple data collection units (I/O) to more intelligent devices such as sensor, one-loop controllers, or programmable controls, and a supervisory system used as a human-machine interface (HMI) for data logging and supervisory control. As IISS is a controlling device that monitors the devices in a company. It basically communicates via the interface card in the PC; the hardware is connected parallel across the device, and it is interfaced with the PC via a transceiver. The device can be accessed both manually via the switches and remotely via the PC. A simulation of connecting a PC withy the machines in a company was executed. Also, we wrote a software program using C language; we will show the remote monitoring takes place between the control room and the PC. These details in the article establish the growing need for Bluetooth technology.
Introduction:
Bluetooth is an open standard for wireless connectivity with supporters mostly from the PC and cell phone industries. Not surprisingly, it primary marker is for data and voice transfer between communication devices and PCs. In the way, it is similar in purpose to the IrDA protocol, Bluetooth, however, is a radio frequency (RI) technology utilizing the unlicensed 2.5 GHz industrial, scientific, and medical (ISM) band. Target applications include PC and peripheral networking, hidden computing, and data synchronization such as for address bookstand calendars. Other applications could include home networking and home applications of the future such as smart appliances, heating systems, and entertainment devices.
Bluetooth history:
Bluetooth was invented in 1994 by L.M. Eriesson of Sweden. The standard is named after Harald Blaatand “Bluetooth” II. King of Denmark 940-9SIAD. A nice stone has be received in his capitol city Jelling (Jutland) that depicts the chivalry of Harald and the ‘runces’ say
v Harald christianized the Danes.
v Harald controlled Denmark and Norway.
v Harald thinks and cellular phones should seamlessly communicate.
The blue tooth Special Interest Group (SIG) was founded by Ericsson. IBM. Intel. Nokia and Toshiba in February 1998 to develop as open specification for short-range wireless connectivity. The group is now also promoted by 3 Com. Microsoft. Lucent and Motorola. More than 1900 companies have joined the SIG.
The following section describes some of the requirements for the Bluetooth system and in essence suggests the functionalities planned for it.
Why Bluetooth?
Bluetooth attempts to provide significant advantages over other data transfer technologies, such as Ir DA and Home RF, vying for similar markets. Despite comments from the Bluetooth SIG indicating that the technology is complementary to Ir DA it is clearly a competitor for PC-to peripheral connection, Ir DA is already popular in PC peripherals, but is severely limited by the short connection distance of 1 m and the line-or-sight requirement for communication. This limitation laminates the feasibility of using Ir DA for chidden computing, where the communicating devices are carboy but not visible to one another.
Due to its RF nature, Bluetooth is not subset to such limitations. In addition to wireless device connections up to 10m (up to 100 m if he transmitter’s power is increased), devices used not be within line of sight and may even connect through walls or other nonmetal objects. This allows for applications such as a cell phone in a pocket or a briefcase acting as a modem for laptop or PDA.
Bluetooth is designed to be low cost, inventorially under $ 10/unit. On the flip side, however, are the limited connection distance and, even more damaging, the transmission speeds. Bluetooth supports only 780 kb/s, which may be used for 721 kb/s unidirectional data transfer (57.6 kb/s return direction) or up to 432.6 kb/s symmetric data transfer. These rates are comparable to the 1 – 2 Mb/s supported by Home RF and. Although live digital video is still beyond the capability of any RF technology, perfectly adequate for file transfer and printing applications.
Finally, Blue tooth’s main strength is its ability to simultaneously handle both data and voice transmissions. It is capable of supporting on asynchronous data channel and up to three synchronous voice channels, or one channel supporting both voice and data. This capability combined with ad hoc device connection and automatic service discovery make it a superior solutions for mobile devices and Internet applications. This combination allows such innovative solutions as a mobile hands-free headset for voice calls, print to fax capability, and automatically synchronizing PDA, laptop and cell phone address book applications.
Architecture Overview
Bluetooth link control hardware, integrated as either one-chip o a radio module and a base-band module, implements the RF, base-band, and link manager portions of the Bluetooth specifications. This hardware handles radio transmission and reception as well as required digital signal processing for the base band protocol. Its functions include establishing connections, support for asynchronous (data) and synchronous (voice) links, error correction, and authentication. The link manager firmware provided with the base band CPU performs low-level device discovery, link setup, authentication, and link configuration. Link managers on separate devices communicate using the Link Management Protocol, which utilizes the services of the underlying link controller (base band). The link control hardware may also provide a host controller interface (HCL) as a standard interface to the software.
Network Topology:
Bluetooth devices are generally organized into groups of two to eight devices called Pico nets. Consisting of a single master device and one or more slave devices. A device may additionally belong to more than one piconet, either as a slave in both or as a master of one piconet and a slave in another. These bridge devices effectively connect Pico nets into a scatter net. A diagram of a blue tooth scatter net.
Bluetooth operates in the unlicensed ISM frequency band, generally cluttered with signals from other devices; garage door openers, baby monitors, and microwave ovens, to name just a few. To help Bluetooth devices coexist and operate reliably alongside other IMS devices each Bluetooth piconet is synchronized to a specific frequency-hopping pattern. This pattern, moving through 1600 different frequencies per second, is unique to the particular piconet. Each frequency hop is a time slot during which data packets are transferred. A packet may actually span up to five time slots, in which case the frequency remains constant for the duration of that transfer.
Baseband State Machine:
Piconets may be static or formed dynamically as devices move in and out of range of one another. A device leaves standby (the low-power default state) by initiating or receiving an inquiry or a page command. An inquiry may be used if the address of a targeted device is unknown; it must be followed by a page command. A page command containing a specific Device Access-Code is used to connect to a remote device. Once the remote device responds, both devices enter the connected state, with the initiating device becoming the master and the responding device acting as a slave.
One in the connected state, the slave device will synchronize to the master’s clock and to the correct frequency-hopping patterns. At this point, link managers exchange commands in order to set up the link and acquire device information. The master will then initiate regular transmissions in order to keep the piconet synchronized. Slaves listen on every master-transmit time slot in order to synchronize with the master and to determine if they have been addressed.
Each active slave is assigned an active member address (AM_ADDR) and participates actively on the piconet, listening to all master time slots to determine if it is being addressed by the master. In addition, there are three lower-power slave states: sniff, hold, and park. A master can only transmit to devices in sniff mode during particular sniff-designated time slots. Therefore, these devices listen only during these special time slots and sleep the rest of the time. A slave in hold mode, alternately, does not receive any asynchronous packets and listens only to determine if it should become active again. Finally, a device in park mode not only stops listening, but also gives up its active member address. It is only a member of the piconet in that it remains synchronizing with the frequency-hopping pattern.
Baseband Links:
The Bluetooth base band provides transmission channels for both data and voice, and is capable of supporting on asynchronous data link and up to three synchronous voice links (or one link supporting both). Synchronous connection-oriented (SCO) links are typically used for voice transmission. These are point-to-point symmetric connections that reserve tome slots in order to guarantee timely transmission. The slave device is always allowed to respond during the time slot immediately following an SCO transmission from the master. A master can support up to three SCO links to a single slave can support only two SCO links to different masters. SCO packets are never retransmitted.
Asynchronous connectionless (ACL) links are typically used for data transmission. Transmissions on these links are established on a per-slot basic (in slots not reserved for SCO links). ACL links support point-to-multipoint transfers of either asynchronous or isochronous data. After an ACL transmission from the master, only the addressed slave device may respond during the next time slot, or if no device is addressed the packet is considered a broadcast message. Most ACL links include packet retransmission.
Link Manager:
The base band state machine is controlled largely by the link manager. This firmware, generally provided with the link control hardware, handles link setup, security and control. Its capabilities include authentication and security services, quality of service monitoring, and base band state control. The link manager controls paging. Changing slave modes, and handling required changes in master / slave roles. It also supervises the link and controls handling of multislot packets.
Link managers communicate with each other using the Link Management Protocol (LMP) which uses the underlying base band services. L.M.P packets, which are sent in the ACI. Payloads are differentiated from logical link control and adaptation protocol (L2 CAP) packets by a bit in the ACL header. They are always sent is a single-slot packet and are higher priority than L2CP packets. This helps ensure the integrity of the link under high traffic demand.
Software Protocols:
The remaining Bluetooth protocols implemented in software. L2CAP, the lowest layer provides the interface to the link controller and allows for interoperability between Bluetooth devices. It provides protocol multiplexing, with allows support for many third-party upper-level protocols such as TCP and a card / volts. In addition. L2CAP provides gr4oup management mapping upper protocol groups to Bluetooth Pico nets, segmentation and reassembly of packets between layers, and negotiation and monitoring quality of service between devices.
Several Bluetooth protocols interface to the L2CAP link layer. SDP provides service discovery specific to the Bluetooth environment will out inhibiting the used to map the communication AP1 to RFCOM service, effectively allowing legacy software to operate on a Bluetooth device. Technology Control protocol specification (TCS) is provided for voice and data call control, providing group management capabilities and connectionless TCS. Which allows for signaling unrelated to an ongoing call. Blue point-to-point and point-to-multipoint signaling are supported using L2CAZP channels, although actual voice or data is transferred directly to and from the base band-bypassing L2cap-over SCO links.
Bluetooth also supports Ir DA object exchange protocol (IrOBEX) a session protocol defined by IrDA. This protocol may run over other transport layers, including RFCOMM and ICP/IP. For Bluetooth devices. Only connection printed OBEX is supported. There application profiles have been developed using OBEX. These include synchronization functionality for phone books, calendars, messaging and so no; file transfer functionality; and object push for business card support.
Finally Bluetooth may be used as a wireless application Protocol (WAP) bearer. The specification outlines the interoperability requirements for implementing this capability.
Logical Control and Adaptation Protocol:
The L2CAP link layer operates over an ACL link provided by the base band. A single ACL link, set up by the link manager using LMP, is always available between the master and any active slave. This provides a point-to-multipoint link supporting both asynchronous and isochronous data transfer. L2CAP provides services to upper-level protocol by transmitting data packets over L2CAP channels. Three types of L2CAP channels exist: bi-directional signaling channels that carry commands; connection – oriented channels for bi-directional point to – point connections. And unidirectional connectionless channels that support point – to –multipoint connections, allowing a local L2CAP entity to be connected to a group of remote devices.
Channels:
Shows L2CAP entities with various types of channels between them. Every L2CAP channels includes two endpoints referred to by a logical channel identify (CID). Each CID may represent a channel endpoint for a connection oriented channel, a connectionless channel, or a signaling channel. Since bi-directional signaling channels is required between any two L2CAP colitis before communication can take place, every L2CAP entity will have one signaling channel endpoint with a reserved CID of ox0001. all signal channels between the local L2CAP entity and any remote entities use this one endpoint.
Each connection-oriented channel in an L2CAP entity will have a local CID that is dynamically allocated. All connection-oriented CIDs must be connected to a single channel, and that channel must be configured before data transfer can take place. Notice that the channel will at that point bound to a specific supper level protocol. In addition, an quality of service (“QoS) agreement for the channel will be established between the two devices. QoS is negotiating for each cannel during configuration and includes data flow parameters such as peak bandwidth. As well as the transmission type: best effort, guaranteed, or no traffic.
Connectionless channels are unidirectional and used to form groups. A single outgoing connectionless CID on a local device may be logically connected to multiple remote devices. The devices connected to this outgoing endpoint from a logical group. These outgoing CIDs are dynamically allocated. The incoming connectionless CID however is fixed at 0x002. Although multiple outgoing CIDs may be created to form multiple logical groups. Only one incoming connectionless CID is provided on each L2CAP entity. All incoming connectionless data arrives via this endpoint. These channels do not require connection of configuration information such as upper-level protocol is passed as part of the data packet.
Channels State Machine:
An L2CAP connection –oriented channel endpoint may be in one of several possible states, with data transfer only possible in the OPEN state. Initially, an endpoint is CLOSED, indicating that no channels are associated with the CID. This is the only state in which a base band is not required, and it is the state an endpoint will default to if the link is disconnected.
Connection:
In order to open a channel, the channel endpoint must be connected and configured. A connection occurs when either the local L2CAP entity requests connection to a remote device or an indication has been received indicating that a remote L2CAP entity is requesting connection to a local CID. In the first case, the request has been passed on to the remote device, and the local entity enters the W4_L2CAP_Connect_RSP state to await a response. In the latter case, the indication is recognized as a connection request, the request has been passed on to the upper layer and the local entity enters the W4_L2CA_Connect_RSP state to await a response. In either case, when the expected response is received, the local device enters the CONFIG state.
Disconnection:
TO close a channel, one L2CAP entity must send a disconnection request to the other. If an entity receives a disconnect request from the upper-level protocol. It passes the request onto the remote device, and the local entity enters the W4+L2CAP_DISCONECT_RSP state to await a response. If the local entity receives an indication that the remote device is requesting disconnection, it sends a disconnection request to the upper layer and then enters the W4_L2CAP_DISCONNECT_RSP state to await a response. In either case, when the expected response is received, the local device enters the CLOSED state.
Packets:
Data is transmitted across channels using packets. A connection-oriented channel uses packets with a 32-bit header followed by a payload of up to 56,535 bytes. The header includes a 16-bit length of payload to use for integrity check and the 16-bit destination CID. The payload contains information received from or being sent to the upper-level protocol. Connectionless channel packets also include a header but always use 0x0002 for the remote CID. In addition, the header is followed by a 16-bit (minimum) protocol/service multiplexer (PSM), which is used to indicate from which upper-level protocol the packet originated. This allows for packet reassembly on the remote device. The PSM field is not required for connection-oriented channels since they are bound to a specific protocol during connection.
Service Discovery Protocol:
The Service Discovery Protocol (SDP) provides a means to determine which Bluetooth services are available on a particular device. A blue tooth device may act as an SDP client querying services, an SDP server providing services, or both. A single Bluetooth device will have no more than one SDP server, but may act as a client to more than one SDP server, but may act as a client to more than one remote device. SDP provides access only to information about services; utilization of those services must be provided via another Bluetooth or third-party protocol. In addition, SDP provides no notification mechanism to indicate that an SDP server, or any specific service, has become available or unavailable as may occur when the service available on a device change, or when a device comes in or out of RF proximity. This would be a common occurrence in a network supporting mobile devices. The client may, of cores poll a server to detect unavailability, but other means are required to detect a server or service that has recently become available.
Service Records:
In SDP a service may provide information per form an action or control a resource. SDP servers maintain service records to catalog all available services provided by the device. A single service record with a dynamically allocated service record handle that is unique within the server represents each service. A special service record with a service record handle of 0x00000000 is provided to describe the SDP server itself and it supported protocols. Service attributes within a service record describe and define the supported service including the service type a service ID. The protocols supported the service name a service description and so on. These attributes are composed of a 16-bit ID and a variable length value. Attribute values in turn include a header field, with a data type and data size, and a data field. A range of data types are supported: null unsigned imager, signed twos-complement integer, universally unique Identifier (UUID), text string, Boolean. Data element sequence (set) data ciement alternative (select one), and URL. The interpretation of this data is dependent on the attribute ID and the service class to which the service belongs.
Discovering Service:
The purpose of SDP is to discover, not access services. Two process are supported: searching and browsing. Searching is based on UUIDs. A service record is returned by a search only if all of the UUIDs in the service search pattern are found within service record attribute values. It does not matter in which attribute a UUID is found, or whether the UUID is only one element in a list, as long as all the search pattern UUIDs are contained somewhere among the attribute values for the service.
Protocol:
SDP is a packet-based protocol utilizing request-response architecture. The SDP packet is referred to as a protocol data unit (PUD). Which includes a header followed by a variable number of parameters. The length of the parameter field is specified in the header, as is the type (PDU ID). Which may indicate a request or response for searches or attribute queries. The header also includes a transaction ID that is used to match a request with a corresponding response. If for some reason the server cannot handle the request it may send a response of type Error Response (PDU ID 0x0).
It is possible that the response may be too large to fit into a single PDU. To accommodate this, a continuation state parameter is supported by most PDUs. In a response, this parameter indicates the number of bytes that are outstanding. The client may then resend the original request, with a new transaction ID, but with the continuation state parameter set. This alerts the server to send the continuation of the response. At what point a response is split is determined by the server.
Three categories of transactions (PDU IDs) are supported: service search transactions service attribute transactions and service search attribute transactions. Service search transitions are used to request a list of service record handles for service records that have attributes containing all of the UUIDs in a service search pattern. There is no mechanism to request all the service records, although browsing is supported as already described. Service attribute transactions are used to request specific attribute values from a service record. Service search attribute transactions combine the service search and service attribute transactions. Which allows getting specific attribute values for all service records that match a service search pattern.
Frame Formats:
The Bluetooth core protocols consist of base-band LMP, L2CAP and SDP. The base band and link control layer enables the physical RF link between Bluetooth units forming a piconet. As the Bluetooth RF system is a frequency hopping spread-spectrum system in which packets are transmitted in defined tome slots on defined frequencies, this layer uses inquiry and paging procedures to synchronize the transmission hoping frequency and clock of different Bluetooth device.
The link manager protocol is responsible for link setup between Bluetooth devices. This includes security aspects like authentication and encryption by generating, exchanging, and checking link and encryption keys, and the control and negotiation of base band packet sizes.
L2CAP provides connection-oriented and connectionless data services to the upper-layer protocols with protocol multiplexing capability, segmentation and reassembly, and group abstractions. Discovery services are crucial to the Bluetooth framework. These services provide the basis for all the usage models.
Bluetooth Today and Tomorrow
With the bulk of the work developing the Bluetooth specification complete, the Bluetooth SIG in now working on improvements and analyzing feedback from the industry. In addition to their work investigating improvements in sped security, noise immunity, and so on the SIG continues to develop Bluetooth profiles.
Together with other industry initiatives, such as WAP and Symian, Bluetooth will have tremendous effects on everybody life. Bluetooth is one of the key technologies that can make the mobile information society possible blurring the boundaries between home, office and outside world.
Conclusion:
In the future Bluetooth is likely to be standard in tens of millions of mobile phones, PCs laptops and a whole range of other electronic devices. As a result, the market is going to demand new innovative applications. Value-added services, end – to – end solutions, and much more. The possibilities opened up really are limitless and because the radio frequency used is globally available, Bluetooth can offer fast and secure access to wireless connectivity all over the world. With potential like that it is no wonder that Bluetooth is set to become the fastest adopted technology in history.
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