Bluetooth on overdrive; UWB at a penny per megabit per second!
Thursday 6 March 2008 @ 2:05 pm
Recently much has been written about the BT SIG’s decision to add WiFi (announced at the GSMA conference opening a few weeks ago in Barcelona) as a means of speeding up certain BT applications in cell phones. Many have conjectured that this announcement means the BT SIG is walking away from UWB. Though controversy and battles makes for more interesting reading, the truth behind this logical choice is much more boring and straight forward than the technology battle it has been portrayed as. On the one hand, it is pretty easy to see why the BT SIG chose to add WiFi as an alternative transport for BT profiles. Simply put, many high-end cell phone manufacturers are adding WiFi to their handsets for both internet access and VoIP services. So, with WiFi already in the phone, using a radio that is “free” and paid for is a pragmatic choice. Another reason to consider adding WiFi is that for many mid-range phones, there is insufficient processing power available on the main applications SOC to be able to keep up with more than about 50Mbps of data. Therefore, the lower throughput of WiFi better matches the available CPU horsepower for many phones.
One way to think of this strategy is that the BT SIG is choosing to have three gears in their radio shifter box – 1st gear, 2nd gear, and turbo overdrive. To simplify the analogy, we can think of today’s BT2.1 as the low gear – about 2Mbps of throughput. The next gear up would be WiFi, which has a throughput of about 20Mbps – or 10x faster than low gear. And finally, the jump up to UWB or turbo overdrive. In the short term, the UWB throughput will be over 200Mbps. Within a year, that throughput will jump up to 500Mbps. Therefore UWB represents another 10x improvement in throughput over WiFi for essentially the same power budget. Thought of another way: basic BT is a 2HP lawnmower, WiFi is a 20HP Vespa scooter, and UWB is a 200HP V-6 or 500HP sports car that gets 10x better gas mileage as the Vespa. Interestingly, UWB will essentially be selling for a penny per Mbps when it ships in volume! If BT had the same cost structure, it would cost 3 cents for a BT chip, and 54 cents for a WiFi chip. So economically speaking, UWB is also a very cost-effective means to turbo charge wireless data transfers.
The more interesting challenge for Dr. Foley and the BT SIG as they adopt both WiFi and UWB as speed boosters for BT application profiles is how these new radios will be effectively marketed to consumers. I suspect if you were to ask Joe Consumer what he thinks about the idea of an improved BT standard that is 10x faster he would likely respond that he can’t listen that fast. Why? Because most consumers equate the BT brand with their “hands free” ear piece. However, it is not difficult to imagine a scenario where two teenagers who have BT-HDR (BT over WiFi or UWB) phones transferring photos from one phone to another. Transparent to them, it will simply go 10x faster than if the phones only had BT in low gear. Or will it? WiFi is normally used in a client-server access point to device connection model. But two cell phones exchanging pictures would require a peer-to-peer type of connection. OK, so use the WiFi ad hoc mode instead. However, the trouble with ad hoc mode is that most corporate access points are designed with the ability to turn it off in any WiFi radio within range. This is possible through the use of a Network Allocation Vector (NAV); and it occurs when an access point observes interference due to “hidden nodes” such as an ad hoc network. (Ad hoc mode would effectively disrupt WiFi network planning of the corporate IT department – thus motivating them to disable ad hoc mode on their premises). Therefore, if WiFi acceleration of BT applications were to become at all popular (which is the objective of the BT SIG) corporate networks would very quickly disable any ad hoc networks they detected – thus disabling the 2nd gear and relegating the use of WiFi based BT applications to connectivity at home or outside away from any corporate networks. In contrast, UWB has been designed since its inception to include a peer-to-peer network. So, UWB turbo overdrive is not fraught with the same technical impediments as WiFi will be. Nevertheless, BT over WiFi will happen. It is a very logical progression for BT to take. With Certified Wireless USB having chosen UWB to eliminate USB cables on the PC, and the BT SIG having chosen UWB for their top gear in the cell phone space, we are moving ever closer to a Life Without Wires™.



