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AND PERVASIVE COMPUTING

12/11/2001

 

 

Table Of Contents

  1. Introduction
    1. Pervasive Computing
    2. Bluetooth Technology

 

  1. Bluetooth Architecture
    1. Software Protocol Stack

                                                              i.      Application Program Interface (API) libraries

                                                            ii.      Logical Link Control and Adaptation Protocol (L2CAP)

                                                          iii.      Link Manager

                                                           iv.      Baseband

                                                             v.      Radio

 

  1. Bluetooth Hardware Design
    1. Microprocessor
    2. Baseband Link Controller
    3. Radio

 

  1. Bluetooth Summary Overview

  2. Potential Applications

  3. Conclusion

  4. Works Cited

 

 

Introduction

Pervasive Computing


Pervasive computing is the next natural evolution of network computing, which in turn evolved from client-server computing (Miller).

 

The idea behind the term pervasive computing is an always-on mobile, networked, computing environment.  Pervasive computing is a term that embodies the future of network computing enabling transparent wireless communication between individuals, between individuals and computing devices, and between devices themselves.

 

Following this concept, computers will not only become increasingly mobile, but also will allow information to be accessible from any mobile position.  This concept allows us to think about networking in a different way.  No longer tied to the network by wires, users will have information on demand regardless of locale.  Seamless communication between different devices will become possible allowing possibilities like advertising to be streamed to a mobile phone as a shopper passes by a storefront while shopping.  As the shopper passes store-to-store, sales offers appear inviting him into the store.  The possibilities for applications of pervasive computing are limitless.

 

 

Bluetooth

 

Bluetooth is the name given to a new technology standard developed by the Bluetooth Special Interest Group (SIG).  The Bluetooth SIG was launched in May 1998.  Its goal was to develop the specifications for a low-powered, short-range, RF-based wireless communication technology.  Today, there are over 1,300 members of the Bluetooth SIG including IBM, Ericsson, Nokia, Toshiba, Intel, and Microsoft.

 

Bluetooth technology enables peer-to-peer communications among all sorts of devices.  The technology is intended to replace device cables and enable computing.  Bluetooth provides the structure for communications devices to exchange information and work together with minimal user effort.  Its key features are robustness, low complexity, low power and low cost.  As seen in Figure 1, Bluetooth provides wireless access to LANs, the PSTN, the mobile phone network, and the Internet to a host of home appliances and portable handheld interfaces.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



Figure 1: Wireless connectivity over Bluetooth.

 

The Bluetooth standard aims to achieve interconnectivity between any Bluetooth device regardless of brand or manufacturer.  As a result, any Bluetooth device anywhere in the world can connect to other Bluetooth devices within in its proximity.

 

 

Bluetooth Architecture

 

Bluetooth is enabled through 5 layers of software and hardware.  These layers distribute functional responsibility where the bottom layers handle the lowest level details and progressively higher layers handle ever more general concerns.

 

In terms of the OSI 7-layer mode, Bluetooth operates on 5 layers as seen in Table 1.

OSI 7 Layer Model

Application
X

Presentation

X

Session

Bluetooth

Transport

Bluetooth

Network

Bluetooth

Data Link

Bluetooth

Physical

Bluetooth

 

Table 1: Bluetooth operating layers of OSI model

 

The five layers utilized by Bluetooth to provide wireless communication can be described as follows.  These layers are show in Figure 2 from top to bottom accordingly.

 

1. Application Program Interface libraries

2. Logical Link Control & Data Adaptation Protocol

3. Link manager physical link control

4. Baseband data processing & transmission management

5. Radio transmission/reception

 

 

1
 

2
 

4
 

5
 
 

 

 

 

 

 

 

 

 

 


Figure 2: Bluetooth Layer Diagram

 

 

At the top resides an Application Program Interface layer (API).  This layer is a library of software modules that connect the Bluetooth hardware module to the host application.  The host is the device that wants to use Bluetooth for its communication requirements.  It could be a laptop, a headphone, a PDA or any other device.

 

The Logical Link Control and Adaptation Protocol (L2CAP) layer connects to the APIs and is responsible for defining Logical Connections.  This layer defines the source and destination for each link and adapts the data to/from the API and Bluetooth.

 

The Link Manager resides below the L2CAP and is responsible for creating and maintaining the Physical links.  This layer deals with establishing the physical connections, negotiating link options with the destination target, and monitoring the health and status of existing links.

 

The Baseband sits on the bottom of the digital hierarchy and is responsible for all of the Bluetooth specific data handling.  This includes packet creation, encryption/decryption, error encoding and correction.  The Baseband is also responsible for a number of low level Bluetooth responsibilities such as inquire and page scanning.

 

 

Lastly, the Radio is responsible for taking the digital data from the Baseband, converting it to analog, and sending it over the air to the target Bluetooth device.

 

 

 

 

Bluetooth Hardware Design

 

Bluetooth system designs are typically comprised of three basic elements: a processor which runs the higher levels of the Bluetooth protocol stack, a baseband link controller which manages the core Bluetooth processes and a radio which implements the 2.4 GHz air interface.

 

Components from any manufacturer meeting the Bluetooth specification may be used to build a Bluetooth hardware device.

 

PCs and many embedded systems are constructed around central processors and chipsets. The processor is a specialized computation engine designed to execute host system application software.  A Bluetooth system design can utilize the processor of a PC or embedded to provide Bluetooth functionality and services.

 

The Baseband link controller is a chip dedicated to the baseband and link layers of functionality.  The BB link controller is designed to work in conjunction with a microprocessor and microcontroller to support the L2CAP layer and higher functions.

 

The radio module is short-range frequency radio transceiver.  It operates in the globally available 2.4 - 2.5 GHz band.  The radio is a mixed signal, digital and analog, device.

 

These components are commonly manufactured discretely using a specialized semiconductor processes.

 

It is important to examine the specifications of the discrete components used to assemble a Bluetooth system in order to ensure they interface correctly and conforms to the Bluetooth specification not only individually but also as a complete package.

 

 

To realize a Bluetooth system, all of its functions must be mapped into hardware. This can be done in a number of ways through a wide variety of components.

 

Four typical Bluetooth system designs are described below in Table 2.

 

 

System

Components

1

Radio (RF), Baseband (BB), and microprocessor/microcontroller (uC).

2

RF, BB, uC, Chipset

3

RF and BB with integrated uC.

4

Bluetooth ASSP IC with RF, BB, and uC.

 

Table 2: Bluetooth System Configurations

 

The four systems described above provide specific options and benefits to a Bluetooth hardware designer so that he may integrate discrete components from multiple manufactures to assemble a custom Bluetooth system.

 

The best choice for a quick Bluetooth solution would be to use System 4, which utilizes a fully integrated ASSP (Applications Specific Standard Parts).  Using the latest advances of System On Chip (SOC) technology Bluetooth ASSPs have emerged that integrate the microcontroller, the baseband link controller, and a radio all in the same device.  This Bluetooth package is ideal for Bluetooth hardware developers because of their all-in-one design.  A Bluetooth ASSP can be taken off the shelf with little or no hardware modification and integrated into a system to leverage the full potential of the Bluetooth design and services it provides.

 

Bluetooth Summary Overview

 

Bluetooth is an open specification that allows compliant devices to talk to each other in the 2.4 to 2.5 GHz ISM (Industrial Scientific and Medical) free band.  This band is not restricted by the FCC and is also used for wireless networking as specified by the IEEE 802.11b standard.  The Bluetooth radio is optimized for very low power consumption, short-range communication, and minimal interference through fast frequency hopping.

 

The nominal distance for a Bluetooth device with a one-milliwatt RF power output is 10 meters and this is extendable to 100 meters by increasing the power to 100 milliwatts or 20 dBm.  The raw data rate for a Bluetooth device is 1Mbps. However, the available data rate is 723 kbps.  This data rate is sufficient for both voice and data communication making Bluetooth hardware integration an increasingly viable option in many applications.

 

Bluetooth can support either:

  1. A single asynchronous data channel.
  2. Up to three simultaneous synchronous voice channels
  3. A channel that simultaneously supports asynchronous data and synchronous voice.

Each voice channel supports 64 kb/s synchronous link in each direction. The asynchronous channel can support an asymmetric link of 723.2 kb/s in either direction while permitting 57.6 kb/s in the return direction, or a 433.9 kb/s symmetric link.   The actual data rates depend on the kind of error correction capability introduced into the data.  This in turn determines the type of packet used.  See Table 3 below for details.

 

 

Packet Type

Max Symmetric rate (two way)

Max Forward Rate

(Assymetric)

Max Reverse (Assymetric) rate

DM1

108.8

108.8

108.8

DH1

172.8

172.8

172.8

DM3

258.1

387.2

54.4 

DH3

390.4

585.6

86.4 

DM5

286.7

477.8

36.3

DH5

433.9

723.2 

57.6 

AUX1

185.6

185.6

185.6

 

Table 3: Bluetooth Packet Data Rates

 

Note: The packet types containing an 'H' in their type field (eg. DH1) refer to packet types with low error correction overhead and high data rates. 'M' refers to medium data rate.  (Kansal)

 

In order to provide security, Bluetooth utilizes four discrete key values.  The four values are:

  1. Public device address.
  2. Private 128-bit authentication key.
  3. Configurable private encryption key of 8 to 128-bits.
  4. A Random number.

 

As the keys have to be secret, they cannot be obtained by inquiry.  While authentication and privacy could be handled at the software protocol layer, it is also provided in the Bluetooth physical layer.  A particular link or connection can be specified to require either one-way, two-way, or no authentication. The authentication is provided using a challenge/response system.  Once a link has been established between two devices, the link key is remembered.  If another link is to be established between the two devices at a later time, this link key can be directly used thus eliminating the need to send keys over the channel again. As a result data can be transmitted securely with minimum user interaction.

 

Bluetooth devices can interact with one or more other Bluetooth devices in several different ways.  The simplest scheme is when only two devices are involved.  This is referred to as a point-to-point connection.  As Bluetooth enabled devices connect and communicate wirelessly, they form ad hoc networks called piconets.  Piconets of up to eight devices can simultaneously communicate with each other (Figure 3).  Moreover, each device can simultaneously belong to several piconets in a network called a scatternet (Blankenbeckler).  These piconets are established dynamically and automatically as Bluetooth devices enter and leave the radio proximity.

 

 

Figure 3: Bluetooth Piconet

 

 

 

Potential Applications

Bluetooth technology is relevant to a very wide range of industry segments like computing, telecom, networking, automotive, consumer electronics, medical and military.  It is projected that by the year 2006 there will be over 200 million Bluetooth enabled devices globally.  Also it is projected that by the year 2004, there will be more than 1 billion mobile subscribers using the internet in some form.  Bluetooth provides RF connectivity for both fixed and mobile devices.


Applications of Bluetooth technology includes, but are not limited to, data exchange, home networking, LAN Access, Dial-up Networking, voice applications, mobile headsets, universal remote controls, security applications, internet Appliances, and the list goes on.  Because of the flexible nature of this wireless technology the potential benefits of using Bluetooth are immense.

 

Bluetooth wireless technology provides an easier way for mobile computing and communications devices to communicate with each other and connect to the Internet at high speeds without the use of wires or cables. The Bluetooth technology also makes it easier for data synchronization of mobile computers, mobile phones, and handheld devices.

 

Imagine some of these everyday applications: you enter a bus and your bus fare is automatically paid by your mobile phone.  Or you get an automatic text message notifying that your kids are safely home from school.  Or while waiting at the airport lounge, you get some interesting duty-free offers directly to your mobile phone. You could play multiplayer games with your friends, or write e-mails on your laptop on the 'plane, then when you land and switch on your handset, the messages can be automatically sent by your phone.  You could even use your mobile phone to control the locking and alarm on your car, as well as integrate it with the car's stereo so you can talk hands free while you are on the go (Miller).

 

 

Conclusion

 

 

Together with other industry initiatives, such as WAP Wireless Application Protocol and the IEEE 802.11b wireless standard, Bluetooth will have tremendous effects on everyday life as it becomes increasingly popular.  Bluetooth is one of the key technologies that can make the mobile information society possible, blurring the boundaries between home, the office, and the outside world.  It is clear that wireless technology still does not replace the functionality of the wired network but the benefits afforded by wireless far outweigh its drawbacks.  The removal of wires in the network makes network computing available to everyone everywhere.  No longer will users be tethered to the information they desire, but the information will be accessible to them, when and where they want it.  At the heart of this revolution are wireless technologies like Bluetooth whose goal it is to connect to the world.


Author: Earth Skater
 


Citations

 

Miller, Brent A. Bluetooth™ Applications in Pervasive Computing. Feb 2000.

IBM, 07 December 2001 < http://www-3.ibm.com/pvc/tech/bluetoothpvc.shtml>.

 

Kansal, Aman. Unofficial Bluetooth page.  Aman Kansal. Nov 2001.

07 December 2001 < http://everything.at/bluetooth >.

 

Blankenbeckler, David. An Introduction to Bluetooth.  Wireless Developers Network.  08 December 2001

< http://www.wirelessdevnet.com/channels/bluetooth/features/bluetooth.html >.

 

 

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