Abstract
Over the last few years, we have witnessed the emergence of many wireless systems and devices such as cellular phones, personal digital assistants, pagers, and other portable devices. However, they are often used separately, and their applications do not interact. One of the goals of personal area networks (PANs) (Bluetooth SIG, 2002a; Gavrilovska & Prasad, 2001) is to enable such a diverse set of devices to exchange information in a seamless, friendly, and efficient way. The emergence of Bluetooth (Bluetooth SIG, 2001b; Roberts, 2003) wireless technology promises such seamless networking. Bluetooth is an open industry standard that can provide short-range radio communications among small form factor mobile devices. Bluetooth is based on a high-performance, low-cost integrated radio transceiver and has been designed to provide a cable replacement technology with emphasis on robustness and low cost. Bluetooth supports two types of links: the synchronous connection-oriented (SCO) link and the asynchronous connectionless link (ACL). Figure 1 illustrates the Bluetooth protocol stack. The link manager protocol (LMP) performs link setup and configuration functions. The logical link and control adaptation (L2CAP) layer supports protocol multiplexing and connection-oriented/connectionless data services. The host controller interface (HCI) layer provides an interface to access the hardware capabilities of Bluetooth. In this article, we focus on the design and implementation of an architecture that (a) provides interoperability and connectivity of Bluetooth networks with other networks using Internet protocol (IP) technology and (b) enables Bluetooth mobile devices to wirelessly stream high-quality audio (greater bandwidth than toll quality voice) content from other Internet devices. We also investigate the efficiency of different design approaches that can be used by Bluetooth-enabled devices for high-quality audio streaming.
TopIntroduction
Over the last few years, we have witnessed the emergence of many wireless systems and devices such as cellular phones, personal digital assistants, pagers, and other portable devices. However, they are often used separately, and their applications do not interact. One of the goals of personal area networks (PANs) (Bluetooth SIG, 2002a; Gavrilovska & Prasad, 2001) is to enable such a diverse set of devices to exchange information in a seamless, friendly, and efficient way. The emergence of Bluetooth (Bluetooth SIG, 2001b; Roberts, 2003) wireless technology promises such seamless networking. Bluetooth is an open industry standard that can provide short-range radio communications among small form factor mobile devices. Bluetooth is based on a high-performance, low-cost integrated radio transceiver and has been designed to provide a cable replacement technology with emphasis on robustness and low cost. Bluetooth supports two types of links: the synchronous connection-oriented (SCO) link and the asynchronous connectionless link (ACL). Figure 1 illustrates the Bluetooth protocol stack.
Figure 1. The Bluetooth protocol stack
The link manager protocol (LMP) performs link setup and configuration functions. The logical link and control adaptation (L2CAP) layer supports protocol multiplexing and connection-oriented/connectionless data services. The host controller interface (HCI) layer provides an interface to access the hardware capabilities of Bluetooth.
In this article, we focus on the design and implementation of an architecture that (a) provides interoperability and connectivity of Bluetooth networks with other networks using Internet protocol (IP) technology and (b) enables Bluetooth mobile devices to wirelessly stream high-quality audio (greater bandwidth than toll quality voice) content from other Internet devices. We also investigate the efficiency of different design approaches that can be used by Bluetooth-enabled devices for high-quality audio streaming.
TopAudio/Video Transmission Over Bluetooth With Avdtp
The Audio Video Working Group has defined a Bluetooth profile that allows streaming of high quality mono or stereo audio directly over L2CAP from another device. This profile, the advanced audio distribution profile (A2DP) (Bluetooth SIG, 2002b), is based on the generic audio/video profile distribution profile (GAVDP) (Bluetooth SIG, 2002c), which in turn uses the audio/video distribution transport protocol (AVDTP) (Bluetooth SIG, 2002d). AVDTP specifies the transport protocol for audio and video distribution and streaming over Bluetooth ACL links. Figure 2 shows the protocol stack model for AVDTP.
Figure 2. The AVDTP protocol stack in Bluetooth (only the audio portion of AVDTP is shown)
Key Terms in this Chapter
Local Area Network (LAN) Profile: The LAN profile defines how Bluetooth-enabled devices access services of a LAN using the point-to-point protocol (PPP).
Bluetooth: Bluetooth evolved from the need to replace wires in short-range communications (e.g., serial cable between computers and peripherals) with short-range wireless links.
Audio/Video Distribution Transport Protocol (AVDTP): Specifies the transport protocol for audio and video distribution and streaming over the Bluetooth air interface using ACL links.
Logical Link and Control Adaptation (L2CAP): The (L2CAP) layer supports protocol multiplexing, provides connection-oriented/connectionless data services to upper layers, and performs segmentation and reassembly operations of baseband packets.
Asynchronous Connectionless Link (ACL): An ACL link is point-to-multipoint between a master device and up to seven slave devices.
Link Manager Protocol (LMP): The LMP performs link setup and configuration, authentication, encryption management, and other functions.
Personal Area Network (PAN) Profile: The PAN profile describes how two or more Bluetooth-enabled devices can form an ad-hoc network. The PAN profile uses the Bluetooth Network Encapsulation Protocol (BNEP) to provide networking capabilities for Bluetooth devices.
Synchronous Connection-Oriented (SCO) Link: A SCO link is a symmetrical point-to-point link between a master and a single slave and is typically used for sensitive traffic such as voice.