Some more clarity on xG Technology's xMax

I had an update meeting this morning with the xMax management team, and got a chance to grill them a bit more deeply on the current plans & business model. I last met them in late 2005, so obviously there's a fair amount that's happened since then.

The first and most important takeout is what applications and customer types they're aiming at initially. It is absolutely evident that xMax is not aimed at service providers looking to compete head-to-head with dense, large-scale, telco-grade cellular networks with all the complicated machinery they require. Maybe on the far horizon if all goes fantastically well, but not right now or realistically within a 3-4 year view.

The target segment of operators is much more akin to a those that are happy with lowest-cost, best-efforts, ISP/VoIP provider approach. The base stations & infrastructure are aimed at competitive service providers wanting to create a bargain-basement, 'alternative' network that avoids the need to tackle complex wholesale and interconnect arrangements with incumbents (wired or wireless) except via Internet VoIP.

Now, there are quite a lot of service providers that would be happy to take the compromises involved - proprietary technology, no "name brand" handsets, little spectrum management, limited end-to-end QoS, no international roaming and so on. These are the same type of organisations that might also look at low-end WiMAX installations, or even the larger WiFi mesh approach. But it is important to stress that these are essentially wireless ISPs that also have a VoIP proposition - similar in many ways to WiMAX Telecom in Europe or niche UMTS-TDD players like Woosh in New Zealand. The difference is that those operators are starting with PCs (which can support VoIP) rather than phones.

All this is well and good - and may even enable 100's of thousands of subscribers in the US, where there's still a few million subscribers on regional cellular networks outside the 'Big 4' carriers. Many of these customers have limited service capabilities - even having to pay extra if they roam nationally out of their local area. But it's not going to quickly scale to millions of users per country for a variety of reasons.

The international story was also interesting, for example talking about its evaluation with Telefonica's Mexican arm. The angle there is to allow large players to enter into commercially challenging new markets at a low cost, not to replace their existing incumbent networks such as Telefonica's Spanish busines or O2. Fair enough as an entry strategy where it's hard (politically or regulatorily) to deal with incumbents, but again it's a bit of a lower-grade solution rather than a fully bulletproof one.

Less clear was the situation with other international markets outside North America, particularly with regard to spectrum. The company's position is that it expects its customers to have access to their own spectrum - but they were very vague about which bands were ideal, how much spectrum might be needed for a given application, or critically, how long it might take to support a new frequency band in the base stations or phones. I also found it slightly worrying that the execs were unclear whether necessary spectrum had to be designated for TDD or FDD use.

I specifically didn't go down the route of asking the company about the recent public spat with a Qualcomm employee (Phil Karn), who has aggressively been trying to 'debunk' some of the company's more high-profile claims for xMax. Nevertheless they proactively raised the issue & pondered on his motives. The execs didn't brandish statements about 'orders of magnitude' better performance but were keen to stress power efficiency. Given that nobody with an engineering background was in the meeting it wasn't a topic I wanted to focus on. Either way, I don't see worrying about xMax as exactly being #1 on Qualcomm's to-do list at the moment given its other predicaments, so I don't see Karn's mission as some weird conspiracy: I suspect he just likes an argument, although in my view there are better ways to win one than the route he's taking.

However.... the CEO did give me useful numbers which I hadn't heard before. Some other engineers may be able to get their teeth into these & yield some analysis.

Apparently, the 1st generation products should yield an aggregate of 17Mbit/s in 26MHz of spectrum in the US ISM band at 902-928MHz, after accounting for guard bands and overhead. Ultimately the company is aiming for 2 bits / Hz in this band, in what they refer to as a "4G" network. They are also intending to go for four sectors per site, yielding a total of 17x4=68MBit/s , or in later versions maybe 2x26x4=208Mbit/s
[edit - that's my calculation, and based on comments below I should have asked about spectrum reuse & probably a bunch of other stuff. Treat it as an upper bound, I guess]

If I'm reading the tables here correctly, that's good but not exceptional in terms of spectral efficiency. My engineering knowledge doesn't permit me to say anything about power consumption, though. Someone else may have a view on this. It's worth noting that range is a bit of a non-issue here as it simply spreads the given (fixed) capacity over a larger area. Again, possibly useful for a startup operator wanting to build up a best -effort network over time by adding base stations, but again that's not a viable proposition for a mainstream operator wanting to launch a large network on Day 1 without having to go back & acquire more lots cell sites subsequently while the network is already running.

There's a bunch of other issues I haven't touched on here that are also important especially around backhaul, standards, threats from US 700MHz services and regional exclusivity.

But my current bottom line is that it sounds like a solution for the "Wireless ISP with VoIP" market, but not a near- or mid-term threat to conventional cellular voice or data services. There may be some extra-clever stuff in how it does power management, but the rest of the solution is not 'telco grade', and it would take a long time to get there as there's no 'ecosystem' in place and no clear strategy to build one. Although they ultimately want to sell silicon, it's not obvious how (for example) Nokia might engage with the company to integrate xMax into its phones.

I've seen some recent comparisons between xMax and 3GPP LTE and major 802.16e WiMAX rollouts like Sprint's, and I think they're largely unfounded & unrealistic - they're completely different propositions aimed at different customer groups & usage cases. To my mind, xMax is more of a potential threat to low-end ISP-type WiMAX deployments, CDMA450 in rural areas, and the largest WiFi mesh implementations, especially in North America or anywhere else with 900MHz unlicenced spectrum. I'm unconvinced they've progressed much towards supporting other frequencies - they certainly don't seem to have any other obvious preferred 'profiles' for 2.6GHz or 700MHz or 2.3GHz or whatever, and given work I've done recently it would probably take a lot of time & effort to support even one of these to a reasonable degree.

(As with my previous posts on xMax, I'm going to be ruthless with comment moderation/deletion)