Motorola and MBOA split on UWB
Two specs risk chaos and slowdown
The two sides in the UltraWideBand standards battle are even more polarised at the end of a turbulent week for wireless personal area networking.
The Multiband OFDM Alliance (MBOA) has devised its own media access control (MAC) layer, in effect rejecting the MAC mandated by the IEEE for the upcoming 802.15.3a standard.
Meanwhile Motorola, the other contender to supply the technology for that standard, has come to this week's IEEE summit with a reworked version of its specification, targeted on very short range links rather than the general purpose digital media network on which the MBOA is focused. All this makes it almost inevitable that, whatever the IEEE finally decides, there will be at least two UltraWideBand physical layers in common use, and now, it seems, at least two MACs.
Chaos and slowdown
Chaos and slowdown in uptake of the superfast, short range technology will only be averted if these alternatives are clearly focused on different applications. The MBOA's moves are clearly designed to secure the plum territory of digital home networks for itself, in line with the core interest of leader Intel, while Motorola is differentiating itself by focusing on the narrower world of very short distance links and on applications in its own heartland of cellphones and PDAs.
The MBOA's leaders, Texas Instruments and Intel, failed last year to gain the 75 per cent of votes required for their technology to be adopted as the PHYSICAL LAYER basis for the IEEE's 802.15.3a standard - an extension to the current 802.15.3, also called WiMedia, with support for very high data rates up to 440Mbps over a few meters.
They have in effect hijacked the industry alliance that promotes and tests both the 15.3 standards, the WiMedia Alliance, but even so, are not prepared to wait for the IEEE to go through its process to get their technology established.
Both have pinned high hopes on the expected growth in digital media home networks and want to jumpstart this boom as soon as possible. To this end, the MBOA has created a new MAC that it claims meets the needs of all three sectors with keen interest in UWB's capabilities - consumer electronics, the PC industry and mobile phonemakers. The bulk of the work was done by Philips, Sony and UWB specialist Alereon. It deviates considerably from the IEEE MAC, which is used in both 802.15.3 standards.
According to MBOA member Philips, a new MAC was necessary to solve various issues with mobility and home electronics. A common criticism of the MBOA proposal in its early days was that it betrayed its roots in the PC industry, while Motorola's Direct Sequence UWB was more appropriate to consumer-focused equipment makers. Key to the new MAC, says Philips, will be enhanced support for mobility, mesh networking and management of piconets. This is achieved through support for the reservation of timeslots for high priority connections, and through decentralised operation that involves every node announcing its connections, so that all active nodes are aware of each other, reducing latency.
There is enhanced rerouting of messages should one link fail, cutting back on dropped connections. The 802.15.3 MAC lacks strong functionality for mesh, roaming and dynamically varying RF environments, claims Philips.Motorola retorts that the existing 802.15.3a MAC has proven support for low latency, quality of service and support for high numbers of users and claimed to be "disappointed" that the MBOA is walking away from it.
The move does seem to further stalemate the IEEE process. The MBOA proposal - which still has to pass some regulatory hurdles connected with power levels - has always taken the lead in successive 802.15.3a votes, though never gaining the requisite 75 per cent, and has the strongest industry backing, especially in the CE world, with the all-important Sony a key supporter. So, if the IEEE were to opt for the Motorola submission instead, on the basis of its technical compliance, it would be seen as a second choice option and undermine the credibility of the standard. But it may have little alternative - the IEEE has never been prepared to consider another MAC. and it does seem that the MBOA has decided to circumvent the standards process altogether, despite its protestations that it will still work with the IEEE.
One issue that is highlighted by the saga is that the IEEE remains focused on and dominated by the IT industry, even as its standards are increasingly critical to the consumer electronics world. In their bid to take their wireless chip architectures into every market from the home to the enterprise, Intel and Texas are finding the IEEE a straitjacket, and the new MAC reveals their keenness to please a whole new set of powerful friends, notably Sony in CE and, in mobile phones, Nokia.
Nokia was a latecomer to the MBOA camp but its interest in UWB is intense and its influence almost certainly strong on the creation of a more mobile-optimized MAC. As the MBOA seeks to establish a de facto standard in consumer electronics, Motorola has shifted its focus in a bid to keep its own UWB approach alive with its revised submission, concentrating on distances of 2-3 meters.
Most of the battle to provide the IEEE 802.15.3a standard for high throughput personal area networking has surrounded distances of around 10 meters, with applications for full-room home media networks. Now Motorola says it sees the real potential for UWB lying in very short distance links, providing a Bluetooth-style link for wireless handhelds and a replacement for peer-to-peer cable standards (although the MBOA has already inched into this space to some extent with its plans for a UWB-based implementation of WirelessUSB).
Motorola says the revised version of its Direct Sequence UWB technology offers up to 1.3Gbps over two meters, and 10 times greater efficiency than the MBOA's over 2-3 meter distances, a boast that it hopes will reawaken enthusiasm for its approach within the IEEE group. It plans to follow its rival in setting up its own industry body to support its technology and, if necessary, circumvent the IEEE and WiMedia Alliance. This is likely to be formed after the IEEE meeting and be called the UWB Alliance. The MBOA has already set up such a body for its technology, called the MBOA Special Interest Group.
Having focused almost entirely on UWB for media centers and home theatres, Motorola told EE Times that "what we've seen happen over the last quarter is an upsurge in interest in handheld applications such as USB and 1394, and the idea that mobile handsets are central to UWB". It has also incorporated the Common Signalling Mode (CSM) devised by UWB start-up Pulse~Link into its specifications. This allows different UWB physical layers to coexist without significant interference (though not to interoperate).
On the defensive
Both these steps by Motorola show that it is on the defensive in UWB, but determined not to give up on the technology it acquired last year with pioneer XtremeSpectrum, one of the only vendors with working short range UWB silicon (incidentally, the rump of that company, minus the UWB assets that it sold to Motorola, filed for Chapter 11 bankruptcy protection this week).
By embracing CSM, something the MBOA has so far failed to do, Motorola is acknowledging that there are likely to be several UWB physical layers in use, whichever finally forms the basis for 802.15.3a - whereas the MBOA still believes it can, in time, make its own physical layer the only significant player. This is not necessarily a bad thing; the remit of UWB is vast, and different physical layers can be suitable for different types of applications, as Motorola is arguing with its latest revision.
This may smack of defensiveness - refusing to admit defeat, but instead trying to move the goalposts. But it also raises a key problem with the IEEE process, particularly in 802.15.3a - the attempt to adopt a single specification to meet a wide variety of needs, with the almost inevitable descent into lowest common denominator territory.
The WiMAX standard has managed to avoid some of this effect by leaving significant leeway for extensions and higher layer variables, without becoming non-standard, but Wi-Fi and 802.15 specifications are less flexible. Martin Rofheart, director of UWB operations at Motorola, said to US reporters this week that "we plan to share with the rest of the community a direct sequence UWB solution that is head and shoulders above either our previous DS-UWB solution or the Multiband OFDM solution".
Critics claimed this proves that Motorola's technology is inferior over the 10 meters mandated by the IEEE taskgroup, but supporters said the company was making positive moves to break the destructive deadlock and to open the way for a dual physical layer world, assuming that the MBOA proposal gains FCC approval following tests later this year. In its new implementation of DS-UWB, Motorola has abandoned a controversial feature of its original proposal, a modulation scheme called MBOK, and introduced a simpler keying scheme, plus improved error correction.
But of course the debate has gone well beyond technology. The best outcome to be hoped for now is that there will, at least, not be more than two UWB physical layers, and that there will be coexistence between both in the same frequencies. It is more than likely that DS-UWB will seek to replace Bluetooth and USB in cellphones and short range device connections, while MBOA will end up in digital media and entertainment devices. It all sounds very neat, except that, by the time UWB products are mainstream, those two classes of devices will be converging rapidly. That could raise a whole new battle, and one that the IEEE is demonstrating itself to be inadequate to referee.
© Copyright 2004 Faultline
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