Information from
Johnson Consulting

  1. What is "Bluetooth"?

  2. How could Bluetooth be used?

  3. Basic Bluetooth functions

  4. How does Bluetooth work?

  5. Establishing network connections

  6. What kind of traffic can Bluetooth handle?

  7. What about competing technologies?

  8. What about radiation; is it dangerous?

  9. What is Bluetooth´s growth potential?

  10. What is Bluetooth´s prestanda?

  11. What about Bluetooth´s security?

  12. Bluetooth definitions

  13. How networks are formed and controlled

  14. What´s the advantage of frequency-hopping?

  15. How timeslots are used

Bluetooth - An Overview

Establishing network connections

Creating a Piconet

A piconet can be created in one of 4 ways:
  1. A page (used by Master to connect to Slave)
  2. A page scan (a unit listens for its´ device access code)
  3. A Master – Slave switch is made
  4. An ”Unpark” of a unit is made (provided there are no active slaves).
In order to establish new connections the procedures inquiry and paging are used. The inquiry procedure enables a unit to discover which units are in range, and what their device addresses and clocks are. With the paging proce-dure, an actual connection can be established. Only the Bluetooth device address is required to set up a connection. Knowledge about the clock will accelerate the setup procedure. A unit that establishes a connection will carry out a page procedure and will automatically become the master of the connection.

For the paging process, several paging schemes can be applied. There is one mandatory paging scheme which has to be supported by each Bluetooth device. This mandatory scheme is used when units meet for the first time, and in case the paging process directly follows the inquiry process. Two units, once connected using a mandatory paging/scanning scheme, may agree on an optional paging/scanning scheme.

The Connection Establishment

After the paging procedure, the master must poll the slave by sending POLL or NULL packets, to which the slave responds. LMP procedures that do not require any interactions between the LM and the host at the paged unit’s side can then be carried out. When the paging device wishes to create a connection involving layers above LM, it sends LMP_host_connection_req. When the other side receives this message, the host is informed about the incoming connection. The remote device can accept or reject the connection request by sending LMP_accepted or LMP_not_accepted.

When a device does not require any further link set-up procedures, it will send LMP_setup_complete. The device will still respond to requests from the other device. When the other device is also ready with link set-up, it will send LMP_setup_complete. After this, the first packet on a logical channel different from LMP can then be transmitted.

The Salutation Architecture

The Salutation Architecture was created to solve problems of service discovery and utilization among a broad set of applications and equipment and in an environment of widespread connectivity and mobility”. The Salutation Architecture defines an entity called the Salutation Manager (SLM) which functions as a service brooker for applications, services and devices that are called Networked Entities. The Salutation Manager allows Networked Entities to discover and utilize other Networked Entities.

When and how is a Scatternet created?

A Master or Slave can become Slave in another piconet by being paged by the Master in this other piconet. This automatically means that any unit can create a new piconet by paging a unit that is already a member of a piconet. Any unit participating in one piconet can page the Master or Slave in another piconet. This could lead to a switch of roles between Master and Slave in this new connection. Inter-piconet communications are established over the shared unit. Time multiplexing must be used for that unit to switch between piconets. In case of ACL links, a unit can request to enter the HOLD or PARK mode in the current piconet, during which time in may join another piconet by just changing the channel parameters.
Units in the SNIFF mode may have sufficient time to visit another piconet in between the sniff slots.
If SCO links are established, other piconets can only be visited in the non-reserved slots in-between.

Copyright © 2001, Johnson Consulting
Last Updated: 2004-04-17