Route discovery based piconet forming

Details Route discovery based piconet forming Route discovery based piconet forming

2000-10-26

2004-06-15

Cangialosi, Salvatore (Department: 2661)

Multiplex communications

Network configuration determination

Using a particular learning algorithm or technique

C370S449000

Reexamination Certificate

active

06751200

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the field of telecommunications. More particularly, the present invention relates to the field of ad-hoc network telecommunications.
BACKGROUND
“Bluetooth” is an example of an ad-hoc wireless network technology that uses a frequency hopping scheme in the unlicensed 2.4 Ghz ISM (Industrial-Scientific-Medical) band. The original intention of Bluetooth was to eliminate cables between devices such as phones, PC-cards, wireless headsets, etc., in a short-range radio environment. Today, however, Bluetooth is a true ad-hoc wireless network technology intended for both synchronous traffic, e.g., voice and asynchronous traffic, e.g., IP based data traffic. The aim is that any digital communication device such as telephones, PDAs, laptop computers, digital cameras, video monitors, printers, fax machines, etc. should be able to communicate over a radio interface through the use of a Bluetooth radio chip and its accompanying software.
FIGS. 1A-C
illustrate three exemplary Piconets. In accordance with, the Bluetooth technology, two or more Bluetooth (BT) units sharing the same channel form a piconet. Within a piconet, a BT unit can be either a master or a slave, although each piconet must have only one master and up to seven active slaves. Any BT unit can become a master.
FIG. 2
illustrates a scatternet. A scatternet is formed through the interconnection of two or more piconets. Two or more piconets connect with each other through a commonly shared BT unit, that is a member of each piconet. BT unit
205
is an example of a BT unit that is shared by three piconets
1
,
2
and
3
.
FIG. 2
further illustrates that a BT unit, which is shared by two or more piconets, may be a slave unit in several piconents, but a master unit in only one piconet. For example, BT unit
210
is the master unit in piconet
10
, but only a slave unit in piconet
11
and
12
. In addition, a BT unit that is a member of two or more piconets may transmit and receive data in one piconet at a time. Accordingly, participation in multiple piconets has to be on a time division multiplex basis. It should be noted that there is no direct transmission between slaves, only between master and slave and vice versa.
Each BT unit has a globally unique 48-bit IEEE 802 address. This address, called the Bluetooth Device Address (BD_ADDR), is assigned when the BT unit is manufactured, and it never changes. In addition, the master of a piconet assigns a local, Active Member Address (AM_ADDR) to each active member of the piconet. The AM_ADDR, which is only three bits long, is dynamically assigned and deassigned and is unique only within a single piconet. The master uses the AM_ADDR to poll a particular slave in the piconet. When the slave, triggered by a polling packet from the master, transmits a packet to the master, it includes its own AM_ADDR in the packet header.
Though all data is transmitted in packets, the packets may contain synchronous data, on SCO links, which is primarily intended for voice traffic, and/or asynchronous data, on Asynchronous Connectionless (ACL) links. If the packet contains asynchronous data, an acknowledgment and retransmission scheme is used to ensure reliable transfer of data, as is forward error correction (FEC) in the form of channel coding.
FIG. 3
illustrates the standard format of a Bluetooth packet, although there are exceptions for certain control packets. The AM_ADDR is located in the packet header, followed by control parameters (e.g., a bit indicating acknowledgment or retransmission request, when applicable, and a header error check (HEC) code.
The format of the payload depends on the type of packet. The payload of an ACL packet consists of a header, a data field and, in most instances, a cyclic redundancy check (CRC) code. The payload of an SCO packet only contains a data field. In addition, there are hybrid packets that include two data fields, one for synchronous data and one for asynchronous data. Packets which do not include a CRC are neither acknowledged nor retransmitted.
FIG. 4
illustrates the protocol layers of a Bluetooth system. The Baseband, LMP and L2CAP are existing Bluetooth specific protocols, the “high level protocol or application” layer represents protocols that may or may not be Bluetooth specific, while the Network layer does not currently exist in the current Bluetooth specifications.
A significant limitation associated with Bluetooth is that there is no defined method for addressing and routing packets from a BT unit in one piconet to a BT unit in another piconet. In other words, the current Bluetooth specification does not specify how inter-piconet communication is performed in a scatternet.
An important capability in any ad-hoc networking technology is the neighbor discovery feature. This is also true for Bluetooth. Without a neighbor discovery capability, a BT unit can not find other BT units with which to communicate, and consequently, no ad-hoc network would be formed. The neighbor discovery procedure in Bluetooth involves an INQUIRY message and an INQUIRY RESPONSE message. A BT unit wanting to discover neighboring BT units within radio coverage will, according to well specified timing and frequency sequences, repeatedly transmit INQUIRY messages and listen for INQUIRY RESPONSE messages. An INQUIRY message consists of only an Inquiry Access Code. The Inquiry Access Code can be a General Inquiry Access Code (GIAC), which is sent to discover any BT unit in the neighborhood, or a Dedicated Inquiry Access Code (DIAC), which is sent to discover a certain type of BT unit, for which a particular DIAC is dedicated.
A BT unit receiving an INQUIRY message, whether it contains a GIAC or a DIAC responds with an INQUIRY RESPONSE message. The INQUIRY RESPONSE message is, in actuality, a Frequency Hop Synchronization (FHS) packet. Bluetooth uses FHS packets for other purposes, e.g., for synchronization of the frequency hop channel sequence, as the name suggests. In any event, by listening for INQUIRY RESPONSE messages, the BT unit that initiated the INQUIRY can collect the BD_ADDR and internal clock values, both of which are included in the FHS packet, of the neighboring BT units.
Related to the INQUIRY procedure is the PAGE procedure. A PAGE procedure is used to establish an actual connection between two BT units. Once the BD_ADDR of a neighboring BT unit is known, as a result of an INQUIRY procedure, the neighboring BT unit can be paged with a PAGE message. Knowing the internal clock value of the BT unit being paged speeds up the PAGE procedure, since it is possible for the paging unit to estimate when and on what frequency hop channel the neighboring BT unit will listen for PAGE messages.
A PAGE message consists of the Device Access Code (DAC), derived from the BD_ADDR of the paged BT unit. A BT unit receiving a PAGE message that includes its DAC, responds with an identical packet. The paging BT unit then replies with an FHS packet, including the BD_ADDR of the paging BT unit, the current value of the internal clock of the paging BT unit, the AM_ADDR assigned to the paged BT unit and other parameters. The paged BT unit then responds once again with its DAC, and the connection between the two BT units is established.
If the paging BT unit is already the master of an existing piconet, the paged BT unit joins the existing piconet as a new slave unit. Otherwise, the two BT units form a new piconet with the paging BT unit as the master unit. Since the INQUIRY message does not include any information about its sender, the BT unit initiating the INQUIRY procedure is the only one that can initiate a subsequent PAGE procedure. Thus, the BT unit initiating an INQUIRY procedure will also be the master of any piconet that is formed as a result of a subsequent PAGE procedure. However, if considered necessary, the roles of master and slave can be switched using a master-slave-switch mechanism in Bluetooth. This, however, is a complex and extensive procedure resulting in a redefinition of the entire piconet which may involve other s

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