Subject: Bluetooth address.

From: "Yong Liu" <[email-masked]>
Date: Mon, 02 Oct 2000 16:52:17 EDT

Hi, everyone:

When I read the Specification of the Bluetooth System,
I'm a little comfused about the address of Bluetooth
device. Although every bluetooth device has a BD_ADDR
address, the access code of bluetooth packet only
contains the information of LAP field of the BD_ADDR
address.So I wonder if LAP field of the BD_ADDR is
enough to identify different Bluetooth devices, or
if LAP is unique to every bluetooth device, or can
two bluetooth devices have the same LAP address?

Can anyone help me make this clear?

Thanks,

Yong
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---

From: Johan Sörensen (ECS)<[email-masked]>
Date: Tue, 3 Oct 2000 08:58:26 +0200

Yong,

Since the LAP is only a part of the whole unique BD_ADDR, the LAP is not unique in itself. The access code in the beginning of every packet is not there to uniquely identify anything in itself. A device expecting a packet correlates against the access code to find the beginning of the next packet within the piconet. Then the header checksum calculation also makes some use of the BD_ADDR of the master to verify the piconet identity.

Regards,

Johan Sörensen.

-----Original Message-----
From: Yong Liu [mailto:[email-masked]]
Sent: den 2 oktober 2000 22:52
To: [email-masked]
Cc: [email-masked]
Subject: Bluetooth address.

Hi, everyone:

Thanks,

Yong

---

From: "Tohru Aihara" <[email-masked]>
Date: Tue, 3 Oct 2000 17:34:04 +0900

Hi Yong,

You are right. Packets in a piconet are identified with the access code derived
from the 24-bit LAP of the master.

However, the FH of the piconet is derived from the master's lower 28-bit BD_ADDR
and the master's 28-bit system clock in the connection state.

I think an LAP with a specific FH is usually enough to identify the piconet
nearby, although some Bluetooth devices can have the same LAP addresses, There
can still theoretically be identical piconets if the masters have the same lower
28-bit of Bluetooth address and if the system clocks are synchronized. Can you
really imagine the situation?

Best regards,
Toru Aihara
IBM Research, Tokyo Research Laboratory

From: "Yong Liu" <[email-masked]> on 2000/10/03 05:52

To:   [email-masked]
cc:   [email-masked] (bcc: Tohru Aihara/Japan/IBM)
Subject:  Bluetooth address.

Hi, everyone:

Thanks,

Yong

---

From: [email-masked]
Date: Wed, 4 Oct 2000 09:57:19 +0800

Dear Aihara and Yong,

The access code (which uses LAP)  is not the only thing used when receiving
a packet.  The packet header is also used in deciding whether a packet
belongs to the correct piconet. The HEC in the header uses master's UAP
(page 53 of baseband spec).   The combination of UAP and LAP should make
every piconet unique.

Best Regards,

Mar Kheng Kok
IBM Emerging Technology Centre

"Tohru Aihara" <[email-masked]> on 10/03/2000 04:34:04 PM

Please respond to "Tohru Aihara" <[email-masked]>

To:   [email-masked]
cc:   "Yong Liu" <[email-masked]> (bcc: Kheng Kok Mar/Singapore/IBM)
Subject:  Re: Bluetooth address.

Hi Yong,

You are right. Packets in a piconet are identified with the access code
derived
from the 24-bit LAP of the master.

However, the FH of the piconet is derived from the master's lower 28-bit
BD_ADDR
and the master's 28-bit system clock in the connection state.

I think an LAP with a specific FH is usually enough to identify the piconet
nearby, although some Bluetooth devices can have the same LAP addresses,
There
can still theoretically be identical piconets if the masters have the same
lower
28-bit of Bluetooth address and if the system clocks are synchronized. Can
you
really imagine the situation?

Best regards,
Toru Aihara

Hi, everyone:

Thanks,

Yong