The Bluetooth SIG is preparing its specifications for the next-generation of Bluetooth. Known as high-speed Bluetooth, this new specification will support high-speed file transfers and video streaming applications. Initially, the Bluetooth SIG selected only WiMedia ultra wideband (UWB) technology to enable this new protocol . Recently, however, it announced the option of using 802.11 as an interim solution, piggybacking Bluetooth protocols on existing Wi-Fi radios in portable devices .

This means that now WiMedia UWB and 802.11 are candidate alternate MAC/PHYs (AMPs) for the high-speed Bluetooth release. The principle is to allow the existing Bluetooth technology to be used in consumer devices while achieving faster throughput with the use of a secondary radio. However, many in the industry are concerned about the known interference issues that will result between the 802.11 radio in the Bluetooth device and other IMT-2000 services operating in adjacent frequencies, such as WiMAX, LTE, UMTS and WCDMA. The worry is that if consumers have a poor user experience with the initial implementation of high-speed Bluetooth using the 802.11 AMP, the long-term risks to the success of the technology could outweigh any short-term time-to-market gains. Bluetooth already has a high-profile position in the consumer marketplace (last year the SIG welcomed its 9000^th member ), and rushing time-to-market with an interim technology is risky.

Usage models
While WLANs and IMT-2000 do not typically operate simultaneously because they both provide access to the network infrastructure. However, high-speed Bluetooth and IMT-2000 services will support independent applications, and they will often be operating simultaneously. This means that if the high-speed Bluetooth device is using the 802.11 AMP, it is likely to be running in an environment with IMT-2000 services operating in nearby frequency bands. To illustrate this point, consider the following usage models.

Figure 1 shows two multi-radio handsets located close to each other. One is making a voice call over WiMAX, the other is transferring a file to a PC with 802.11-based high speed Bluetooth. The voice over WiMAX call will drop when the other handset transfers a file to the PC even at a distance of several meters. Figure 2 shows a handset making a voice call with WiMAX and at the same time printing using high-speed Bluetooth. The handset needs to wait for the end of the call before printing without dropping the call. Alternatively, it would not be able to receive a call if the print job already started.
Click here for Figure 1.
Figure 1: One handset transfers a file to a laptop using 802-11-based high-speed Bluetooth. The other handset operates a WiMAX voice call. The two handsets will interfere with each other even at 8m separation.

Click here for Figure 2.
Figure 2: A handset with WiMAX and 802.11-based Bluetooth cannot operate both functions at the same time.

In both of these usage models, any interference between the Bluetooth system and the WiMAX or cellular services would be extremely detrimental to the end user's experience. The reality is that consumers expect to be able to use multiple technologies simultaneously, without interference. Spectrum allocation
One of the initial reasons for concern regarding interference between the Bluetooth 802.11 AMP and IMT-2000 services is that they operate in adjacent parts of the spectrum (see Table 1). The concern is that the use of 802.11 as a high-speed option for Bluetooth would have severe detrimental effects on other services operating in adjacent licensed frequency bands.

Click here for Table 1.
Table 1. Spectrum allocations.

In addition, even though the Bluetooth SIG intends to limit the 802.11 AMP to file transfer applications, once this high-speed radio functionality exists, users may decide to use it for video streaming (as described by Bluetooth press materials ). Because of their continuous nature, these streaming applications over an 802.11 AMP will have an even higher potential for interference than file transfers.