12.6 Bluetooth Profiles

The purpose of the Bluetooth profiles is to describe the application-level usage models and their implementation. The usage models describe the usage scenarios utilizing the Bluetooth radio for specific applications. A profile describes the behaviors vertically down the protocol stack and defines the parameter ranges for each protocol. The Bluetooth profiles are needed for interoperability reasons, which is quite important considering the different types of devices that may be available and different vendors that will be developing Bluetooth devices. Definitions of profiles will enable interoperability not only at the radio level but also at the application level. Figure 12-11 shows different profiles that are currently defined for Bluetooth.

Figure 12-11. Bluetooth profiles.

The following sections briefly describe the significance of some widely used Bluetooth profiles. In addition to these profiles that are defined as part of Bluetooth specifications v1.1, new profiles for various other applications are currently being defined. Among them, imaging, printing, hands-free, ISDN access, and SIM access are noteworthy. Importantly for the purposes of IP connectivity, a new profile for personal area networking (PAN) is being defined and is discussed in this section for relevance.

12.6.1 Generic Access Profile

Bluetooth devices are required to connect to other Bluetooth devices irrespective of the manufacturer and common applications supported in those devices. Therefore, a set of basic device discovery, connection management, and security capabilities are provided as the basic Bluetooth capabilities under this profile. For the reason of basic interoperability and compatibility of all Bluetooth devices, this profile is a mandatory requirement for all Bluetooth devices.

The main objective of this profile is to describe the use of lower layers of the Bluetooth stack (LC and LMP). For security- related alternatives, higher-layer protocols (L2CAP, RFCOMM, and OBEX) are also used.

12.6.2 Service Discovery Profile

The service discovery profile (SDP) does not provide serve a specific user application, but it defines usage to discover the services offered by the Bluetooth devices in the vicinity. These services discovered are usually the other profiles (e.g., file transfer, cordless telephony). This profile is used by user-initiated requests and makes use of the SDP in the lower layers of the Bluetooth protocol stack.

12.6.3 Cordless Telephony Profile

The cordless telephony profile (CTP) defines the features and connection procedures so that a Bluetooth device can function as a cordless phone. The profile describes the interoperability aspects with a Bluetooth base station that is connected to a fixed telephony network. This profile completely defines the call setup and connection scenarios, DTMF signaling, call line identification features supported in the fixed network, and the audio over Bluetooth. This feature enables Bluetooth-capable cellular phones to be able to use fixed telephony networks by the use of some phone based on the user location. Two roles are defined for this profile:

Gateway (GW) ” GW acts as a Bluetooth base station that could serve several (up to seven) Bluetooth terminals supporting CTP. It has other capabilities to connect to the fixed network for telephony call establishments.

Terminal (TL) ” TL is the Bluetooth terminal, or simply a cordless phone with Bluetooth radio, or an integrated cellular/Bluetooth device with CTP support.

12.6.4 Headset Profile

Headset profile (HSP) was one of the first profiles developed by the SIG because of the importance of the wireless headset usage scenario. HSP is not related to telephony-oriented TCS-BIN but is related to SPP. HSP provides simple audio communications by utilizing AT telephony control over RFCOMM.

12.6.5 Serial Port Profile

The serial port profile (SPP) utilizes the RFCOMM protocol to enable many cable replacement scenarios. There is no need for master/slave roles in SPP, but instead SPP defines peer device roles for general serial communications. SPP defines the steps required to establish an RFCOMM serial port connection. SPP acts as the base or as an abstract profile for several other profiles. Dialup networking, fax, and LAN access profiles are derived from the SPP.

12.6.6 Dialup Networking Profile

The dialup networking profile (DUNP) utilizes RFCOMM to establish modem connections using the AT command set to support data calls. DUNP defines the GW and TL roles similar to the CTP scenario. The GW provides the modem service, and TL is another Bluetooth device requesting modem service to access a data network. Once the DUNP connection is established, higher-layer protocols like TCP/IP and above can be run. DUNP has capabilities similar to the LAN access profile with minor differences in the link connection establishments.

12.6.7 Fax Profile

The fax profile is also based on SPP and is similar to the DUNP profile in defining device roles and in utilizing the RFCOMM to establish modem connections using the AT command to set up fax connections. The AT command set depends on the fax classes supported. Three different classes are supported, of which at least one class is mandatory.

• Fax Class 1 is specified by TIA-578-A and ITU T.31.

• Fax Class 2.0 is specified by TIA-592 and ITU T.32.

• Fax Service Class 2 is manufacturer defined without any standards.

12.6.8 LAN Access Profile

The LAN access profile (LAP) describes how PPP connections can be set up over RFCOMM for Bluetooth devices to get connected and access LAN services. It also defines how connected devices in a piconet can form an independent LAN by using the same PPP connection mechanisms. There are two roles defined for the Bluetooth devices supporting LAP.

• LAN access point ” This Bluetooth device provides service access to LANs supporting various link-layer protocols.

• LAN data terminal ” This is a PPP client device that requests for access to the LAN through the LAN access point.

12.6.9 Generic Object Exchange Profile

The generic object exchange profile (GOEP) is similar to SPP in acting as an abstract profile for other profiles. It defines common aspects, including device roles, connection establishments, and security considerations. It utilizes the OBEX protocol to enable common data exchange operations supported by object push, file transfer, and synchronization profiles.

12.6.10 Synchronization Profile

The synchronization profile defines the requirements, protocol behavior, and procedures that shall be used by Bluetooth devices providing synchronization applications. It makes use of the GOEP to define the interoperability requirements for the synchronization profile protocol. The most common devices using the synchronization profile might be notebook PCs, PDAs, and mobile phones exchanging various kinds of data like PIM (personal information management) data, phone numbers , calendar, and personal information among Bluetooth devices. The synchronization features can either be user driven or automatically handled by the devices when in proximity based on some preconfigured behavior.