ility in channel assignment and reducing interference. channels. However, the group sought to use a slightly Some exposure to increased intersymbol interference reduced bandwidth of 15 MHz, SO that more non- and sensitivity to multipath may result from the overlapping channels could be provided in the same area narrower bandwidth, but because 802.15.3 is a PAN than 802.11 classic or b/g allow. technology not intended to be used at long ranges, little In July 2003, the 802.15.3 task group approved a new performance limitation should result. PHY layer standard that provides higher data rates while otherwise essentially using the Bluetooth MAC and 5.1.5.3 UWB PANs: A progress report protocol stack. The general approach is to use more so- phisticated coding than was available a decade ago to Although 55 Mbps may seem like a lot of bits, it is a mar- allow more data to be transferred in less bandwidth. As ginal capacity for wireless transport of high-definition with 802.1 la and g, higher modulations are used to send television signals (a technology that may finally reach more data per symbol; 32QAM uses the 16QAM con- mainstream deployment in this decade in conjunction stellation with the addition of partial rows and columns. with large-screen displays). Task group 802.15.3a was A novel coding approach, trellis-coded modulation charged with achieving even higher data rates, at min- (TCM), is used to achieve good performance at modest imum 100 Mbps with a target of 400 Mbps, to support (S/N). In the conventional coding schemes we examined versatile short-range multimedia file transfer for homes SO far, each set of bits determines a modulation symbol and business applications. (for example, a dibit determines a QPSK point) and the To achieve such ambitious goals, the task group turned received voltage is first converted back to a digital value to a new approach, based again on recent FCC actions. In (an estimate of what the dibit was) and then used to 2002 the FCC allowed a novel use of spectrum, ultra- figure out what