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Bluetooth Guide

Ted's Bluetooth Guide for Pocket PC Devices

Bluetooth Technology is growing by leaps and bounds. It was thought at one point that Bluetooth was going to be a thing of the past. Boy was we mistaken! All of us has witnessed a surge of Bluetooth GPS devices. A great majority of PDA devices released now includes Bluetooth. There are now several Bluetooth GPS devices available. Then printers came along; then keyboards, cellular phones, Bluetooth dongles - you name it. Admit it; at one time you asked yourself, "Why would I need Bluetooth". "I have no use for it". I was one of those voices. Now a good portion of my accessories are Bluetooth. In allot of ways I found Bluetooth at times more beneficial than WiFi. As I started to do some research on Bluetooth and how to do some tasks via Bluetooth I found that there is not a great deal of information available on the internet. So a great deal of my Bluetooth success has been done with trial and error. I have then decided to put this document together. I wanted to bring together in one document just about everything you can do with Bluetooth. It is my intent that this tutorial is beneficial to others and can gain experience with the Bluetooth phenomenon.

Research and testing allowed me to put this tutorial together. All of my tests where done using the PDAs with integrated Bluetooth radios. Also all of the Bluetooth devices that I used utilize the Widcomm Bluetooth drivers and software. I used the following items:

Dell Axim X30 Mid
HP iPAQ h2215
Kensington USB Bluetooth Dongle
Linksys USB Bluetooth Dongle
Acore AG-600 Bluetooth GPS Receiver
Sony-Ericsson T608 Bluetooth Phone
Plantronics M3000 Bluetooth Headset
Jabra BT-250 Bluetooth Headset

All of the examples given in this tutorial may differ a little to your setup. Some Bluetooth adapters do not use the Widcomm drivers and software thus making setup slightly different. However the concept is the same and hopefully you can find some pointers here to help you out.

What is Bluetooth?

Bluetooth is a short-range wireless standard allowing devices to connect and interact with each other. There are a ton of hardware devices that can utilize the Bluetooth technology. These devices can be:

GPS
Modems
Keyboards and Mice
PDAs
Cellular Phones
Desktop Computers and Laptops (integrated Bluetooth)
Bluetooth Dongles for Desktops and Laptops
Printers
Audio Headsets
and many more

The popularity of Bluetooth is increasing as more devices are hitting the market that conforms to the Bluetooth standard. You can now get automobiles that can interact with Bluetooth devices.

Bluetooth utilizes a low-cost transceiver chip in each Bluetooth device. This chip transmits in the frequency range of 2.45 GHz (which is common in some household appliance devices). Bluetooth is short-range averaging about 10 meters. Bluetooth is unlike WiFi (Wireless Fidelity) which can communicate over greater distances. Bluetooth is also slower than WiFi in terms of transmission speed. Data is exchanged at a rate of 1 Mbps (megabit per second). Bluetooth utilizes a frequency hop scheme which allows devices to communicate in areas with a lot of electromagnetic interference.

Bluetooth also utilizes encryption and device verification. A pairing method is used between Bluetooth devices. In order for one device to use another it must be paired. An authentication key can be generated at the time of pairing to prevent other nearby Bluetooth devices to gain access to your device. Once the two devices are paired the transmission is then encrypted between the two devices. Since Bluetooth uses a frequency hopping scheme it makes things pretty difficult for a hacker to gain access to it.

Bluetooth: How It Works

Bluetooth connectivity works by pairing two devices together. Data packets are sent between the two paired devices controlled by data blocks. Both devices can do frequency hops at a rate of 1600 times a second depending on the state of traffic. As a result you can expect to see data transmissions between Bluetooth devices anywhere from 864 Kbps to 1 Mbps.

Bluetooth is designed to link up to eight different devices. Depending on the connection each device is classified as a master or a slave. This is done in the discovery process. The discovery process allows detection of other Bluetooth devices for pairing. In order for a device to be detected it must be put in discovery mode. Some devices will stay in discovery mode once it is enabled. I suggest not leaving a device in discovery mode. This opens the door for other people to detect your device and take control of it. Some devices once enabled will automatically disable itself from discovery mode after a given interval (usually 30 or 60 seconds). Once a device is discovered the ability to use the discovered device highly depends on a Bluetooth Profile. Bluetooth Profiles control Bluetooth device behavior. Profiles establishes a link connecting the transmission mode of one device to the other. For example a Bluetooth enabled PDA may be able to discover a Bluetooth headset that was placed in discovery mode. However in order to use the headset with the PDA the necessary profile must exist on the PDA in order to be able to use it. If the profile is missing then the two devices are rendered totally unaware of each other.

As already mentioned Bluetooth is designed to link up to eight different devices. Some devices are point to point devices. This means that these devices can only pair to only one device at a time. In order to use these type of devices on another device you must establish a link to the new device thus loosing the link to the prior device. Other devices are multi-point devices. These devices allow multiple Bluetooth connections on the same device. Examples of this would be PDA devices which now leads us into the next section.

The Profiles of Bluetooth

The Bluetooth Special Interest Group (SIG) consortium has defined 20 different profiles. In version 1.1 of the Bluetooth specification 13 different profiles are used. These profiles control the behaviors through which Bluetooth devices communicate and interact with each other. In order for the two devices to work together the supported profile must exist on both devices.

Generic Access Profile (GAP)
This profile defines how two units discover and establish a connection with each other. This profile handles the discover and linkage between two unconnected devices. This profile general exists in all Bluetooth devices.
Service Discovery Application Profile (SDAP)
This profile discovers the application services available on Bluetooth devices during discovery mode. A service inquiry is sent to the other Bluetooth device and receives what services is supported. It is at this time the proper service profile can be used and a proper link is established for usage of the device.
Cordless Telephony Profile
This profile defines how a Bluetooth device can be used with a wireless phone such as Bluetooth-adapted cellular phones.
Intercom Profile
This profile actually works along with the Cordless Telephony profile. This defines how two Bluetooth equipped cellular phones in the same cellular network communicating with each other without the use of the public telephone network. This enables for instance using the two phones as an intercom within an office.
Serial Port Profile
The Serial Port profile establishes a wireless virtual serial port between two devices. This profile emulates RS-232 control signal communication. An example of devices that would use this profile would be Bluetooth GPS receivers.
Headset Profile
This profile defines how a Bluetooth headset should communicate with other headsets or computers (desktop, laptop or PDAs).
Dial-up Networking Profile
This profile defines how a modem connection can be used with a Bluetooth device such as a Bluetooth equipped desktop, laptop, PDA, cellular phone or a Bluetooth equipped standalone modem. This profile gives wireless access to a dial-up modem for the purpose of dial-up to the internet, corporate LANs and other data dial-up needs.
FAX Profile
This profile is similar to the Dial-up Networking profile except that it sends and receives faxes.
LAN Access Profile
This profile establishes connection between two Bluetooth devices to share network connectivity to the existing LAN connection or to the internet. One Bluetooth device would be connected to the LAN as an ordinary LAN workstation. The LAN connection on that workstation would then be shared with the other Bluetooth device giving that device access to the LAN. The network connection and transmission would use the PPP (Point-to-Point) protocol.
Generic Object Exchange Profile (GOEP)
This profile defines the protocols and procedures to be used by applications handling object exchanges between devices. Instances of this would be File Transfer and Synchronization which is based on this profile. Devices usually using this profile is computers, PDAs and cellular phones (mobile phones and smart phones). This profile is dependent on the Serial Port profile. When exchanging objects the OBEX standard is used.
Object Push Profile
This profile is used with the GOEP profile to send and receive small objects. Examples of this would be the exchange of electronic calling cards.
File Transfer Profile
This profile is also used with the GOEP profile to transfer files between two Bluetooth devices.
Synchronization Profile
This profile is also used with the GOEP profile to enable synchronization of calendar and address information between two computers. To clarify things this is not the profile that is used for synchronization of Pocket PC devices using Activesync. The profile actually used for this would be the Serial Port profile. This profile is used by devices such as Bluetooth equipped cellular phones.

Based on these profiles in the Bluetooth 1.1 specification, users with Bluetooth equipped devices normally fall in 5 commonly used models for Bluetooth connectivity. These are predominately more common than the other uses.

Internet Bridge
This is the ability to use a mobile phone or a wireless modem as means for a PC or PDA with dial-up networking capabilities to access the network (internet) without a physical connection to the device. This affords the user the freedom to connect to the internet using their Bluetooth equipped cellular phone no matter where they are located.
Headset Usage
Everyone just loves the ability to be able to use a headset without the distracting wires dangling around their neck. Bluetooth headsets acts as the remote unit's audio input/output interface. The unit is most likely computer devices (including PDAs) as well as Bluetooth equipped cellular phones.
LAN Access
In some instances you won't have WiFi available (e.g. some Corporate LANs do not provide WiFi access). Bluetooth affords you the opportunity to use another Bluetooth equipped computer the ability to access that LAN or the internet. Once connected you would operate just as if your device was connected directly to the LAN.
File Transfer
Being able to transfer files and folders in a pinch is very important to some users that are on the go. With transmission speeds up to 1 Mbps, file transfers are quick and painless. This prevents the need to look for flash memory cards, thumb drives or worse yet; floppy disks.
Synchronization
Just as with LAN Access everyone is not afforded with WiFi access on their corporate LAN but have a need to be able to synchronize their PDA when away for the desk. Syncing via IR is out of the question because you won't have line of site. However Bluetooth gives you the ability to do a wireless sync short range.

Other common uses are Bluetooth printing and Bluetooth GPS usage.

NOTE: All of the Bluetooth procedures in this guide was tested using the Dell Axim X30 and the iPAQ h2215 which has integrated Bluetooth and also uses the Widcomm drivers. Some procedures may differ due to the Bluetooth drivers used.

Connecting a Bluetooth Headset to a PDA

Bluetooth Headsets are becoming very popular. It provides a convenient way to listening to audio or using it for speech recognition without wires. In order to utilize Bluetooth headsets with PDAs the Headset profile is used. This allows the PDA to be able to recognize and make a link to the Bluetooth headset. However you will not be able to hear any sound just using the Headset profile alone. An additional profile is used to transfer sound from the PDA to the headset. This profile is the Audio Gateway profile. The two profiles together provides users with complete hands-free use of Bluetooth headsets with PDAs.

At the time of this writing several HP iPAQ PDAs do not provide the Headset or the Audio Gateway profile. Either HP purposely omitted the profiles or disabled them. The only current iPAQs that can be modified to use the Bluetooth headsets is the iPAQ h2200 series and the iPAQ 194x series. Kai's Bluetooth Headset Patch modifies that registry to enable the Bluetooth Headset profile and the Audio Gateway. The Dell X30 provides the necessary Bluetooth profiles to use Bluetooth headsets. Check your PDA documentation (if it has integrated Bluetooth) or your Bluetooth SD or CF card documentation to make sure that the Headset and Audio Gateway profiles are provided. The setup of a Bluetooth headset is as follows (setup was done on the Dell Axim X30):

Place your Bluetooth Headset in discovery mode. Check the documentation of your device for the instructions on how to do so with your particular headset model.
Open Bluetooth Manager on the PDA and select New.
If available select Hands-free/Headset setup

Figure 4.1
When prompted click Next. The PDA will now go into discovery mode and should detect the Bluetooth Headset if it has been properly set to discovery mode.

Figure 4.2
Tap on the discovered Bluetooth Headset. In my case I am using the Jabra BT200 Headset. The PDA will now try to authenticate to the Headset to complete setup. This is part of the pairing process. Usually the Passkey for most headsets is '0000'.

Figure 4.3
Once the Passkey is entered the Headset will now bond to the PDA. A shortcut icon is created in Bluetooth Manager and it can be used to either connect or disconnect from the device.

Figure 4.4

The double arrows on the Headset shortcut icon symbolizes a connection between the PDA and the Headset. To disconnect tap and hold on the Headset icon and select Disconnect. When a connection is made all sound from the PDA will be redirected to the Headset.