Bluetooth

BT Antenna Position (CUH-1115A)

Bluetooth

Bluetooth is a wireless technology for creating personal area networks operating in the 2.4 GHz unlicensed band, with a default range of 10 meters.

An overview of Bluetooth:

• http://engineeringagenda.com/agenda/2013/09/bluetooth/ An introduction to Bluetooth
• http://www.eetimes.com/document.asp?doc_id=1200909 An introduction to debugging Bluetooth in embedded systems

Bluetooth radio

Bluetooth 2.0 uses frequencies between 2.4000 and 2.4835 GHz, and divides the band into 79 MHz channels (numbered 0-78), with frequency hopping at a rate of 1600 times per second. Channel 0 has a frequency centred at 2.4020 GHz, allowing a lower guard band of 2 MHz. Channel 78 has a frequency centred at 2.4800 GHz, allowing an upper guard band of 3.5 MHz. Bluetooth devices are divided into three classes, depending on their maximum transmitted power (and hence their maximum range):

Class	Power	Range
Class 1	100mW (20 dBm)	100m (325ft)
Class 2	2.5mW (4 dBm)	10m (32ft)
Class 3	1mW (0 dBm)	1m (3ft)

• http://www.instructables.com/id/Increase-and-extend-the-range-of-a-USB-Bluetooth-d/#step0 Increase and extend the range of a USB Bluetooth

Overlapping channels BT/WiFi

• archaic BT/Wifi channels

Center Frequency (2.4xx Ghz)	BT 2.0 Channel	BT 4.0 Channel	WiFi channel (center freq. in GHz)
00	Guard	Guard
01			1 (2.412)
02	0	0
03	1
04	2	1
05	3
06	4	2		2 (2.417)
07	5
08	6	3
09	7
10	8	4
11	9				3 (2.422)
12	10	5
13	11
14	12	6
15	13
16	14	7				4 (2.427)
17	15
18	16	8
19	17
20	18	9
21	19						5 (2.432)
22	20	10
23	21
24	22	11
25	23
26	24	12	6 (2.437)
27	25
28	26	13
29	27
30	28	14
31	29			7 (2.442)
32	30	15
33	31
34	32	16
35	33
36	34	17			8 (2.447)
37	35
38	36	18
39	37
40	38	19
41	39					9 (2.452)
42	40	20
43	41
44	42	21
45	43
46	44	22					10 (2.457)
47	45
48	46	23
49	47
50	48	24
51	49		11 (2.462)
52	50	25
53	51
54	52	26
55	53
56	54	27		12 (2.467)
57	55
58	56	28
59	57
60	58	29
61	59				13 (2.472)
62	60	30
63	61
64	62	31
65	63
66	64	32
67	65
68	66	33
69	67
70	68	34
71	69
72	70	35
73	71
74	72	36
75	73
76	74	37
77	75
78	76	38
79	77
80	78	39
81	Guard
82		Guard
83

Bluetooth connection

The number of Bluetooth® devices you can connect at the same time depends on the Bluetooth® devices.

There are three type of connections in Bluetooth:

• Single-slave: a point-to-point connection (only 2 Bluetooth units involved)
• Piconet: One Bluetooth unit acts as the master of the piconet, whereas the (up to seven active) others units acts as slaves.
• Scatternet: Multiple piconets with overlapping coverage areas form a scatternet.

Device icons

Shows the types of found Bluetooth® devices using icons.

Icon	Device
	DUALSHOCK™4 wireless controller or other controller	Yes
	PlayStation®Move motion controller	Yes
	Computer	Yes
	Mobile phone, smartphone	Yes
	Headset	Yes
	Speakers	Yes
	Mouse	Yes
	Keyboard	Yes
	Printer	Yes

Bluetooth Adressing

Each Bluetooth unit has a unique 48-bit address (BD_ADDR).

Company_assigned						Company_id
Lower Adress Part (24-bit) transmitted with every packet as part of the packet header						Upper Adress Part (8-bit)		Non-Significant Adress Part (16-bit) assigned publicly by the IEEE
lsbxxxx	xxxx	xxxx	xxxx	xxxx	xxxx	xxxx	xxxx	xxxx	xxxx	xxxx	xxxxmsb

Class of Device/Service (CoD)

In practice, most Bluetooth clients scan their surroundings in two successive steps: they first look for all bluetooth devices around them and find out their "class". You can do this on Linux with the hcitool scan command. Then, they use SDP in order to check if a device in a given class offers the type of service that they want.