xMAX

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Sistema de banda larga usa sinais fracos de rádio

"Uma nova tecnologia que emite sinais fraquíssimos em freqüências de rádio muito utilizadas pode permitir o acesso alta velocidade para dispositivos móveis ou conectar casas que não têm outro meio de navegar pela Internet. A xMax, mais recente inovação nas comunicações em banda larga, é um sistema de transmissão de dados muito silencioso que emprega canais de rádio já repletos de barulhentos sinais de pagers ou televisão." (...) Ler mais nesta página

Fonte: B. Piropo
[07/07/05] Um novo padrão “wireless”: xMax

As transmissões de dados sem fio estão por toda parte. Vão desde o padrão “Bluetooth” que permite a dois dispositivos trocarem dados no mesmo aposento, passam pelo WiFi que estende o raio de ação até o mesmo prédio e se encaminham para o WiMax, que o amplia até a mesma cidade. Pois bem: a empresa xG Technology LCC, sediada em Sarasota, no Estado da Flórida, EUA, está anunciando mais um padrão de comunicações sem fio em alta taxa (Wireless Broadband Communication) denominado xMax.

Mas em um mundo onde já há tantos padrões, qual a vantagem de criar mais um?

Bem, segundo Joe Bobier, o inventor do padrão, ela está no fato do xMax não exigir um “canal” (faixa de freqüências) exclusivo para transmitir dados. A transmissão é feita em alta taxa (“banda larga”) usando freqüências situadas na faixa conhecida por “sub-GHz”, já ocupada por outros usuários.

Nessa altura dos acontecimentos, se você tem algum conhecimento de telecomunicações deve estar, no mínimo, olhando atravessado e com a pulga atrás da orelha. Porque efetuar transmissões nas freqüências de outros usuários pode interferir com o sinal dos proprietários legais dos canais. O que tanto é inaceitável quanto expressamente proibido.

Não obstante, é exatamente isso que Bobier propõe. E garante que não somente a tecnologia não fere a legislação vigente como também não causa qualquer interferência no sinal que trafega legalmente pelos canais compartilhados.

Mas como isso é possível?

Segundo a xG Technologies (veja FAQ em www.xgtechnology.com/faq.htm , esse aparente milagre é fruto de uma tecnologia denominada xGCM (de xG Coded Modulation), que usa um sinal de baixíssima potência para transmitir dados que são captados por uma antena especial. A potência de transmissão é tão reduzida que o sinal transmitido fica abaixo do patamar de ruído normalmente existente na atmosfera. Como os receptores de radiofreqüência que se utilizam dessas faixas são regulados para desprezarem os sinais abaixo deste patamar, não são afetados pelos sinais xGCM.

Na verdade, não fosse assim, seria impossível efetuar transmissões por radiofreqüência, já que a interferência dos ruídos de fundo produzidos pela maioria dos equipamentos eletro-eletrônicos seria insuportável. Por isso as autoridades responsáveis estabelecem limites que impedem essas interferências. A xG Technologies assegura que os sinais xGCM situam-se em um nível de potência cem mil vezes menor que os dos limites estabelecidos pela FCC (a agência reguladora americana) e dez mil vezes menor que o usado pelas emissões da faixa UWB (Ultra WideBand).

O segredo, naturalmente, está na unidade receptora, que segundo a xG Technologies, é cuidadosamente sincronizada com a emissora de sinal. E, compreensivelmente, mais detalhes não fornece, já que a tecnologia ainda se encontra em fase experimental.

O primeiro teste de campo bem sucedido foi levado a termo no último mês de maio, uma transmissão entre pontos distantes uma milha (1.609m) que ultrapassou edificações e outros obstáculos sem perda sensível ou distorção de sinal (veja relato no artigo “ xMax First Long-Range Field Test: a Success” em www.xgtechnology.com/news.htm ).
E, segundo artigo de Peter Judge, na Techworld, a xG Technologies promete para setembro próximo a entrada em operação de uma estação base entre Miami e Fort Lauderdale, na Florida, EUA, que cobrirá um raio de 15 milhas transmitindo dados em uma taxa de 40 Mbits/s com uma potência inferior a um watt usando o canal de 900 MHz, que dispensa licença e é normalmente usado por telefones sem fio.

Não sei se realmente precisamos de um novo padrão. Mas o simples aparecimento de mais um é um bom indicador que a comunicação de dados sem fio é uma tendência irreversível.

B.Piropo
bpiropo@pobox.com

Sistema de banda larga usa sinais fracos de rádio

Uma nova tecnologia que emite sinais fraquíssimos em freqüências de rádio muito utilizadas pode permitir o acesso alta velocidade para dispositivos móveis ou conectar casas que não têm outro meio de navegar pela Internet. A xMax, mais recente inovação nas comunicações em banda larga, é um sistema de transmissão de dados muito silencioso que emprega canais de rádio já repletos de barulhentos sinais de pagers ou televisão.
"O xMax invade freqüências de rádio, embora invadir não seja a palavra correta porque temos autorização para transmitir um sinal desde que ele não interfira com os sinais mais fortes", explica o inventor Joe Bobier. O que o sistema tem de único é que ele é capaz de transmitir de sinais fracos demais para serem captados por antenas normais, mas que podem ser "ouvidos" por antenas especiais que sabem em que direção devem "escutar". Isso permite que o mesmo escasso espectro de freqüências de rádio possa ser usado por duas aplicações ao mesmo tempo.

A tecnologia poderia interessar a uma operadora de telecomunicações ou de Internet que não tenha licença de uso de ondas de rádio, porque a empresa poderia oferecer serviços de banda larga com número muito baixo de antenas especiais, acrescentando mais estações conforme a demanda cresce. A idéia interessa também regiões rurais onde as operadoras consideram caro demais a instalação de uma cobertura de acesso à Web por meio da tecnologia de telefonia celular de terceira geração (3G), que exige estações rádio-base separadas por intervalos de apenas alguns quilômetros.

"Estamos falando de aumento de alcance da ordem de 400% a 500%", diz Bobier, acrescentando que isso supera em muito o desempenho do Flash-OFDM, também alardeado como sistema de banda larga ideal para áreas rurais. A XG Technology, empresa sediada na Flórida que controla o xMax, está discutindo com diversos fabricantes de chips e equipamentos a produção do hardware necessário.

Os chips de rádio para os aparelhos custariam entre US$ 5 e US$ 6 por unidade, se produzidos em massa, e as estações rádio-base sairiam por cerca de US$ 350 mil, preços competitivos se for levada em consideração a área coberta.

Faixas de frequência baixas

Stuart Schwartz, professor de engenharia elétrica da Universidade de Princeton, afirmou que o xMax não é um sistema eficiente para transmissão de dados sem fio, "mas o faz de uma maneira benigna. Você nem sabe que ele está lá. É muito inteligente". A vantagem é que além do mesmo espectro poder ser usado para duas aplicações sem a necessidade de um canal especial, o xMax pode operar a baixas frequências, que são capazes de percorrer grandes distâncias e de atravessar paredes.

Outras recentes tecnologias de banda larga sem fio, como a WiMAX e Flash-OFDM, precisam de frequências dedicadas. Se elas ficarem a frequências acima de 1 gigahertz o sinal terá problemas ao atravessar edifícios e outros obstáculos ou mesmo para percorrer grandes distâncias. A tecnologia da XG pode ser usada também em frequências mais altas e até em cabos, mas a companhia está se concentrando nos canais de frequência mais baixa primeiro.

Bobier descobriu uma maneira de colocar 1 bit de informação em um ciclo de frequência e recuperar este sinal fraco com um novo tipo de filtro. Se o xMax usar um sinal poderoso, que precisa de uma frequência dedicada, pode aumentar ainda mais o alcance e a sua capacidade. A primeira rede xMax está sendo construída em Miami e Fort Lauderdale onde uma estação rádio-base pode entregar um sinal de banda larga em uma área de 103,5 quilômetros quadrados.

A capacidade do xMax não é maior que a de outras tecnologias, o que significa que mais antenas precisam ser instaladas se um certo número de usuários estiver usando a rede, normalmente entre centenas a mil usuários.

Reuters

Novo sistema de banda larga sem fio "sussurra" em canal de rádio

Depois das recentes tecnologias de banda larga sem fio WiMAX e Flash-OFDM, chega ao mercado o xMax.
Esta pode ser a solução para conectar à web regiões rurais, onde considera-se caro a instalação de cobertura por telefonia celular 3G.
Uma nova tecnologia de comunicação que "sussurra" em freqüências de rádio muito utilizadas pode permitir serviços de banda larga móvel para aparelhos portáteis ou conectar casas que não têm outro modo de navegar pela internet em alta velocidade. Essa mais recente inovação nas comunicações em banda larga chama-se xMax.
Trata-se de um sistema de transmissão de dados muito silencioso que emprega canais de rádio já repletos de barulhentos sinais de pagers ou televisão, explica o inventor Joe Bobier. "O xMax invade freqüências de rádio, embora invadir não seja a palavra correta porque temos autorização para transmitir um sinal desde que ele não interfira com os sinais mais fortes", afirma.

O que o sistema tem de único é que ele é capaz de transmitir de sinais fracos demais para serem captados por antenas normais, mas que podem ser "ouvidos" por antenas especiais que sabem em que direção devem "escutar". Isso permite que o mesmo escasso espectro de freqüências de rádio possa ser usado por duas aplicações ao mesmo tempo.

Uma alternativa para conectar áreas rurais à web – A tecnologia poderia interessar a uma operadora de telecomunicações ou de internet que não tenha licença de uso de ondas de rádio, porque a empresa poderia oferecer serviços de banda larga com número muito baixo de antenas especiais, acrescentando mais estações conforme a demanda cresce.

A idéia interessa também regiões rurais onde as operadoras consideram caro demais a instalação de uma cobertura de acesso à web por meio da tecnologia de telefonia celular de terceira geração (3G), que exige estações rádio-base separadas por intervalos de apenas alguns quilômetros. Estamos falando de aumento de alcance da ordem de 400% a 500%", diz Bobier, acrescentando que isso supera em muito o desempenho do Flash-OFDM, também alardeado como sistema de banda larga ideal para áreas rurais.

A XG Technology, empresa sediada na Flórida que controla o xMax, está discutindo com diversos fabricantes de chips e equipamentos a produção do hardware necessário. Os chips de rádio para os aparelhos custariam entre US$ 5 e US$ 6 por unidade, se produzidos em massa, e as estações rádio-base sairiam por cerca de US$ 350 mil, preços competitivos se for levada em consideração a área coberta.

Eficiência questionável
Stuart Schwartz, professor de engenharia elétrica da Universidade de Princeton, afirmou que o xMax não é um sistema eficiente para transmissão de dados sem fio, "mas o faz de uma maneira benigna. Você nem sabe que ele está lá. É muito inteligente."

A vantagem é que além do mesmo espectro poder ser usado para duas aplicações sem a necessidade de um canal especial, o xMax pode operar a baixas freqüências, que são capazes de percorrer grandes distâncias e de atravessar paredes.

Outras recentes tecnologias de banda larga sem fio, como a WiMAX e Flash-OFDM, precisam de freqüências dedicadas. Se elas ficarem a freqüências acima de 1 gigahertz o sinal terá problemas ao atravessar edifícios e outros obstáculos ou mesmo para percorrer grandes distâncias.

A tecnologia da XG pode ser usada também em freqüências mais altas e até em cabos, mas a companhia está se concentrando nos canais de freqüência mais baixa primeiro. Bobier descobriu uma maneira de colocar 1 bit de informação em um ciclo de freqüência e recuperar este sinal fraco com um novo tipo de filtro. Se o xMax usar um sinal poderoso, que precisa de uma freqüência dedicada, pode aumentar ainda mais o alcance e a sua capacidade.

A primeira rede xMax está sendo construída em Miami e Fort Lauderdale onde uma estação rádio-base pode entregar um sinal de banda larga em uma área de 103,5 quilômetros quadrados. A capacidade do xMax não é maior que a de outras tecnologias, o que significa que mais antenas precisam ser instaladas se um certo número de usuários estiver usando a rede, normalmente entre centenas a 1.000 usuários.

Fonte: Reuters
www.intermanagers.com.br

Mídia Inernacional

[04/11/05] Could xMax change the world of broadband?
Rupert Goodwins
ZDNet UK

There are three big questions about xMax, the broadband wireless technology that creator XG Technology claims will give megabit access without needing any dedicated spectrum. What are the details of the claim; does it work; and what does it mean for the future of wireless?

The claims are extraordinary. By combining Ultrawideband (UWB) and more conventional technology, xMax's creator, Joe Bobier, says that the system can let anyone be a wireless ISP — covering thousands of square miles from one very affordable transmitter, and building in denser coverage as new users come online. It does this by using parts of the spectrum with much better long-range and in-building characteristics than the multi-gigahertz bands used by WiMax, 3G and UMTS-TDD — alternative spectrum below 1GHz that, while very desirable, is occupied by other users.

Yet XG says that this spectrum can be reused without upsetting the current allocations because xMax has an unmatched data carrying capacity per watt: it is potentially thousands of times more efficient than its competitors, according to Bobier. Its very weak signals won't interfere with existing users nor they with it, thanks to xMax's receiver design. That, frustratingly, remains secret — although Bobier says that the key component is being patented and the patent should become public some time this month. He also says that the receiver is very simple and cheap to produce.

There are other claims, such as one that the system can be configured in an ultra-low-power mode so that a 2Mbps signal can be transmitted across over 10m with a power of just over 3nW. That's around 300 times less than a quartz wristwatch consumes. There are a wide variety of trade-offs that can be made to make the system match particular needs: one mode has a powerful but very narrow band signal providing timing information to increase the efficiency of the wide band component. If there's no narrow-band spectrum available, that can be omitted at a loss of around 25 percent of the efficiency. And cognitive radio techniques can be used so that multiple transmitters run by independent entities will automatically configure themselves to prevent mutual interference and advertise their most efficient access modes.

Does it work? Nobody can say for sure — not even XG. No independent tests have been published of any of the technology. However, the company has demonstrated a very important part of its plans: it has covered an area of over a thousand square miles with a claimed 50mW signal, and shown nearly 4Mbps arriving at a point almost 18 miles from the transmitter. Even given the details of the test — some 14dB total gain in the antenna systems and a 260m-tall tower for the transmitter — this is an exceptional result.

There are a nearly infinite number of questions to be answered on the technical side: how will the system work with multiple stations, how will it cope with real-life interference, and will it be allowed to operate in the same frequencies as existing licensed users. The company says that although there are severe limitations to the number of stations a single basic transmitter — possibly only 200 at a reasonable speed &;mdash; the much greater area the transmitter's signal usefully covers compared to the alternatives means that it is much easier to get that initial user base from among the much greater potential market. As more users arrive, it is easy to add more coverage by directional antennas or more base stations.

Alternatives such as WiMax would have to establish many more base stations initially to cover the same number of potential customers. Furthermore, the company has mathematically modelled high densities of users, indicating that the technology will continue to work well if it becomes very popular. And the company has said that xMax's key advantages can be combined with the best bits of other standards in a mix-and-match way to produce a very wide variety of solutions. Some big-name companies very active in wireless broadband are starting to take xMax seriously, even if none is ready to go on the record yet.

There are massive regulatory and strategic problems to overcome. UWB, perhaps the closest technology to xMax in existence, has so far failed to turn into consumer products after more than five years of promises; regulators outside the US have been cool towards it, existing spectrum users have raised question after question about its claimed ability to operate across multiple bands without causing interference, and the industry itself has been locked in a damaging, confusing and exhausting battle over the details of the standard. It is not clear that xMax could escape a similar fate, even if the technology questions were to be universally agreed. On the other hand, the bruising and disappointing experience of UWB is instructive: nobody I've talked to who was involved in the process says they'd do it the same way all over again.

And increasingly, regulators are willing to consider radical changes in their approach to managing spectrum. In the UK, Ofcom has said that its "view is that the market is better placed than a regulator to judge the optimum commercial service and technology", which, ten years ago, would have been an unthinkable attitude for such a regulator to adopt.

But if the technology works and the regulators are amenable, does that mean xMax has success guaranteed? Hardly. Take WiMax, which like UWB has been promised for a number of years but unlike UWB has spectrum allocated for it or its similary featured competitors in territories around the world. Despite many millions of pounds in investment and heavy promotion from companies such as Intel, nobody can say for sure whether WiMax will be a success. Even 3G remains something less than a sure bet in many of its markets.

The most frustrating aspect of all this is that new wireless technologies are very much needed, and that for all its remaining uncertainties xMax has earned the right for a sober and searching review of its potential. That potential is significant: the ideas within xMax can plausibly play a major role in creating the cheap, capable and ubiquitous wideband wireless networks that will mark the next generation of access. Those ideas are just part of a much bigger game XG will have to play if it is to achieve success in a market filled with existing players jealously guarding their space, regulators working with many conflicting interests and alternative systems shrilly proclaiming their suitability.

If all goes well, xMax will have its place as a major component of the wireless future, but that 'if' will figure as prominently in the technology's immediate future as that 850 foot tower did in its immediate past.

Copyright © 2005 CNET Networks, Inc. All Rights Reserved.
ZDNET is a registered service mark of CNET Networks, Inc. ZDNET Logo is a service mark of CNET NETWORKS, Inc.

[10/07/06] xG Technologies: Offers an Evaluation kit

xG Technologies is a company that I have spoken about in the past very favorably. They always outperform and do not resort to Hype because their stuff works better then their marketing team is capable of explaining in print.

Once again, xG Technologies goes above and beyond by offering a xG Technologies evaluation kit for companies to evaluate the performance of its first product using proprietary wireless broadband technology.

Nokia, Ericsson, Siemens, etc. do not offer an evaluation kit for their wireless network solutions. They have an old business model to sustain and providing such openness would effect the entire value chain they have built. Hence, I applaud xG Technologies for breaking the mold on how wireless network equipment is sold and by providing their solution to any Mobile operator thinking of offering a carrier class Mobile VoIP solution.

Here in Norway, Network Norway (new GSM operator) has announced they will build a new GSM network (2G) built by Siemens for 400 million Nok (@ 55 million Euro). Novotel, another new GSM operator has requested the remaining available UMTS license, thereby causing a UMTS bid process in October '06. Both of these companies are building wireless networks of the past while xG Technologies is offering a free evaluation kit for their future.

Competition is too great and time is moving too fast to make such costly business ending mistakes. Everyone must think outside the box (and country) as to what and where the next great business model is emerging from. xG Technologies is one of those companies that should be on every wireless operators list of whom to talk to about their future.

[01/09/05] Too good to be true?
By Donny Jackson

SUNRISE, Fla. — Wireless communications traditionally has been a story of tradeoffs, with each solution seemingly creating another problem.

Want greater signal range? Increasing the signal power will do the trick, but doing so increases the noise floor, increases interference risk and can drain the battery life from a receiver. Using smaller cells mitigates these negative effects, but that requires more base stations, which can greatly increase capital-expenditure and maintenance costs.

And if you want nationwide coverage, be ready to write checks for billions to pay for the spectrum at auction before spending a dime on network infrastructure.

But those truisms may change drastically in the near future, thanks to the work done in the lab of xG Technology. Within a modest 3500-square-foot space in a Ft. Lauderdale-area strip center, xG President of Operations Joe Bobier — inventor of the company's technology platform — has led a small staff in the development of a broadband-wireless system known as xMax, which uses a patented technique that Bobier characterizes as “a fundamental paradigm shift in the way radio signals are modulated and demodulated.”

Paradigm shifts generally are overblown. But xG promises a quantum-leap package: easily deployable broadband data in a potentially wide coverage area using little or no dedicated spectrum and operating at incredibly low power levels.

“It is a rather unusual way to do communications. In my 40 years in this industry, I've never seen anything like it,” said Stuart Schwartz, a Princeton electrical engineering professor. “I think Joe Bobier is a very, very clever guy. He's done something quite remarkable.”

Ali Hedayati, a former Intel general manager who headed the chip giant's Centrino effort and now is a technical adviser for a venture-capital firm, echoes this sentiment.

“Most disruptive technologies change the way a segment of the business is run,” Hedayati said. “I think xG's technology could potentially do that.”

HOW DOES IT WORK?
At the heart of the xMax solution is xG's Flash Signal technology, which utilizes single-cycle waveforms to transmit information at a minimum effective rate of 1 MB/s for each megahertz of spectrum utilized in the information-bearing channels, Bobier said. Whereas most communications systems require a receiver to modulate thousands, or millions, of radio frequency (RF) cycles for each bit of information, the Flash Signal scheme accomplishes the feat in just one RF cycle.

Not only does this single-cycle technique increase throughput efficiency, it means even traditionally weak signals are usable, Bobier said. Moreover, because the receiver — the design of which is xG's most-guarded intellectual property — includes a passive wavelet path filter that acknowledges only single-cycle waveforms, all other RF signals are ignored. This lets xMax operate in “silent spectrum” that permits effective communication even at very low power levels, he said. (For a more technical explanation of how this technology works, visit "Breaking free of the past"

“We're talking about a 25 to 45 decibel advantage in an industry where 2 decibels is worth killing for,” Bobier said. “And you don't have to throw a lot of spectrum or power at [producing a broadband signal], if you can get rid of the noise.”

By virtually eliminating the typical noise floor, xMax enables the power levels for its information-bearing signal to be as much as 100,000 times below the FCC's current regulated power limit for out-of-band emissions, which is designed to prevent systems from interfering with each other. In fact, xMax's power levels are 10,000 times below the FCC's power limits for ultrawideband (UWB) transmissions, according to xG officials.

IS IT REAL?
Not surprisingly, the notion that an unknown company could devise a communications scheme that will outperform WiMAX at a fraction of the infrastructure costs while operating at sub-UWB power levels is enough to make those in the industry raise their eyebrows. The fact that xG claims it can do this without an operator having dedicated spectrum has caused many to incredulously dismiss xMax before seriously considering the technology.

“Broadband without spectrum — that's pretty funny,” said one industry source upon initially hearing a description of xMax. “Did they also promise you the Brooklyn Bridge when they were selling you that?”

Bobier said he understands the skepticism, particularly among longtime RF engineers who don't understand how the xG Flash Signal technology can possibly work. Indeed, there is no way xMax would have been developed within the constraints of traditional RF thinking, he said.

“There's nothing intuitive about processing radio and power in single cycles,” Bobier said. “Every time I found myself frustrated and I was going wrong, it was because I was following all the training I had received. It was only when you have a moment of clarity and you tell yourself, ‘Stop thinking in terms of power and tones and start thinking in terms of the mechanics of one wave at time’ that you make progress.”

Robert Syputa, a senior analyst at Maravedis, said the doubts about xG's technology are largely a reflection of the company's large promises.

“It's never proper to suspend suspicion about something that portends to walk on water,” Syputa said.

Indeed, Bobier encountered initial resistance even within xG's hierarchy when he first broached the notion of single-cycle modulation.

“Initially, we probably had the same reaction people are having today upon hearing about it for the first time,” said Roger Branton, xG's chief operating officer and chief financial officer. “It just sounds too good to be true.”

But xG officials insist it is true, the product of years of development and a few key moments of inspiration (see sidebar). And, for all the questions raised by the engineering community about xG's modulation scheme, there are an increasing number of indicators that xMax is more than an empty promise.

Princeton's Schwartz, an admitted initial skeptic, today may be xG's staunchest advocate. Hedayati said he believes xG's technology “has legs” after following the company and its technology for months and seeing a lab demonstration in August.

Perhaps most significantly, SkyTel — a paging firm that is a wholly owned subsidiary of MCI — has validated xG's technology and signed a letter of intent with the fledgling company in June, said Rick Mooers, xG chairman and CEO.

SkyTel declined to be interviewed for this story, but its belief in xG's ability to revitalize sub-gigahertz spectrum caused the paging firm to scrap plans to sell its 900 MHz airwaves, Branton said.

“They totally changed their business strategy after seeing this technology,” he said.

Of course, lab demonstrations can only be so convincing, which is why xG plans to conduct an xMax trial during the next two months in preparation for a scheduled commercial launch of a broadband wireless offering in November. The fixed-wireless system will have the following attributes:

Antenna: One omnidirectional transmitter located on TV broadcast tower at a height of 850 feet;

Range: 20 miles, covering the cities of Miami and Fort Lauderdale, including inside buildings (see map);

Data rate: At least 10 Mb/s throughout the coverage area;

Spectrum used: A 6 kHz carrier on dedicated spectrum and 10 MHz of information-bearing spread spectrum in the unlicensed 900 MHz band;

Interference: None, despite the presence of a TV transmitter on the same tower;

Power: A maximum of 50 W for the carrier and less than 0.15 W for the information-bearing channels.

The success level of this trial will largely determine xG's fate, Schwartz said.

“I understand why it works and how it works; what I don't know is just how well it's going to work when you place protocols and applications on top of it,” he said. “There may be some loss in the data rate … but I don't see any fundamental, technical reason why this won't work in a multi-user environment.”

WHAT DOES IT MEAN?
If xG's technology works as promised, the potential ramifications are mind-boggling, by all accounts.

As a fixed-wireless play, it could provide a local-loop alternative for independent ISPs and competitive carriers, which effectively have lost all leverage in their negotiations to lease lines with cable operators and telecom carriers that provide access to their customers. Mooers said SkyTel's representatives noted the local-loop potential of xG's technology during their Florida visit.

“If this technology had been available four years ago, AT&T and MCI probably wouldn't have been in play,” Mooers said, noting the long-distance giants' inability to connect directly with customers forced them to merge with RBOCs.

For operators with existing spectrum, xMax offers an opportunity to re-use the airwaves and maximize the value of the asset. This could be particularly significant to public-safety entities. Instead of deploying hundreds of nodes at 2.4 GHz or 4.9 GHz for a few square miles, a public-safety organization could deploy xMax to provide a fixed-wireless connection for a much greater coverage area with just one base station while re-using existing sub-gigahertz spectrum.

For potential operators without spectrum holdings, xMax can let them enter the wireless game. Instead of using dedicated spectrum, the timing function can be integrated with the information-bearing channels at a loss of 25% of the data rate, Bobier said.

Hedayati said he believes xMax could spark regulatory changes, including the way the FCC allocates spectrum and its interference rules. But the more immediate impact will be the manner in which it changes the economics of entry into the wireless market, he said.

“You can actually deploy [xMax] on unlicensed spectrum — that becomes a completely different ballgame,” he said.

One of the most intriguing aspects of xMax is its potential in the mobile wireless environment, although the technology has not been optimized for that use yet. Because xMax operates at such low power levels, the battery life of mobile devices could improve dramatically, Bobier said.

The low power levels also create other opportunities, including Zigbee-like devices that offer greater range and functionality. For law enforcement and the military, the low power levels would make it easier to communicate in “stealth” mode because only an xMax receiver can detect xMax transmissions.

And xG Flash Signal technology is not limited to the wireless arena. Using the single-cycle waveform and receiver-centric design, telecom carriers should be able to quadruple the range of their DSL offerings, and cable operators can double the capacity of their networks, Bobier said. Similar advantages should be achievable in optical technologies, although xG has not tested those possibilities yet, he said.

“It's what we want it to do,” Bobier said. “We're starting with the bricks, and we can build any building that we want.”

That characteristic makes xG's technology especially attractive, Hedayati said.

“The beauty of this thing is that you don't have to modify anything — you can just walk right into existing infrastructure,” he said. “You can be on licensed spectrum or unlicensed spectrum. … You can have more flexibility with this than anything I've ever seen because of the way they deal with the noise.”

Officials for xG acknowledge all these possibilities and say new applications for the technology emerge on a weekly basis in different markets. But don't expect xMax to fund trials for anything other than the fixed-wireless project, Mooers said.

“If it's viable [as a fixed-wireless product], the engineers will see that it works, and they can extrapolate the application to other markets,” he said.

WHICH WAY TO THE PROMISED LAND?
This philosophy underscores a fundamental reality for xG: Its technology cannot reach its full potential if the small company tries to do everything itself, Mooers said.

“We're going to do fixed wireless in a Cisco model, where we make high margins on the equipment in the short term,” he said, noting that some wireless ISPs may let xG Technology get a piece of their revenues. “But it shifts to a Qualcomm and royalty model when you hit the economies of scale and large volumes. It will end up being small amounts of money — but in billions of units — if we hit it in the right scenario.”

That means teaming with companies that bring assets to the table outside of xG's core competency, Mooers said. The list of potential candidates is huge — chip vendors, independent ISPs, software companies and service providers, to name a few — and the most attractive possibilities are massive companies because they can provide the financial, legal and political resources that can assure xG's single-cycle system makes it to market on the company's terms.

“We're sitting on the solution,” Mooers said. “A lot of people say, ‘You're a competitor of WiMAX.’ That's not necessarily true — we may very well be a key part of the WiMAX solution. … It depends on who our partner is. If our partner is Intel, it's more than likely going to be kept under the name WiMAX.”

Hedayati said he believes the potential for such a scenario increased greatly with Qualcomm's recently announced plans to purchase OFDM vendor Flarion Technologies (read "OFDM sector faces changes"). With most WiMAX technologies not ready for prime time, wireless operators looking to deploy 3G and 4G technologies have little choice except to pay royalties to Qualcomm unless they turn to xMax, he said.

But striking such agreements promises to be a delicate endeavor, Mooers said. To date, most inquiries from large companies have come from their venture-capital arms — a direction in which Mooers is hesitant to go, claiming that funding is not an issue for xG. He said he is not interested in offers that would let a large company effectively swallow xG and its technology.

Mooers also said xG will be very discriminating about any exclusivity arrangements, probably granting exclusivity only on a niche-market or geographic basis, if at all.

“We have to make sure that we hook into a revenue model that lets us get a good piece of the economic value we provide,” he said. “We're not just going to do another big company/small company deal, where the big company gets the lion's share of the economic value from the small company's innovation.”

Complicating matters is the fact that many potential partners may have mixed feelings about xG's technology. For example, cable operators might view xG as an opportunity to add a wireless component cost-effectively to their portfolios or they might see it as a threat to their last-mile holdings.

Similarly, some wireless carriers may be excited that xG will let them add new services through the re-use of their spectrum, while others may curse the fact that this new technology could negate the current spectral advantages for which they've spent tens of billions of dollars during FCC auctions to secure.

Even the government could have reason to be ambivalent. Certainly xG's technology promises to be a great way to make President George W. Bush's goal of ubiquitous broadband in a competitive marketplace a reality. On the other hand, Congress is counting on a 700 MHz auction this decade to generate at least $10 billion to help address budget deficits, but bidders might not be willing to pay that much if a spectrally efficient technology like xMax lets them compete effectively without owning a lot of airwaves.

Of course, all of these hypothetical scenarios will be irrelevant if xG does not convince the marketplace that its technology is for real. xG officials say the stated performance projections for the technology are conservative, but Mooers recognizes that only a successful deployment will completely convince the naysayers.

“After this trial, I think [potential strategic partners] are going to come to us, if only because they risk having to compete against us if they don't.”

INSPIRATION HELPS FILL A NEED
It often is said that necessity is the mother of invention, and that certainly was the case with xMax. And, if Joe Bobier's invention of xMax somehow proves to be troublesome to Verizon Communications, the giant telecom carrier would have only itself to blame.

That's because Bell Atlantic — the RBOC's name before its merger with NYNEX — provided the copper wires that Bobier's family-owned business in Parkersburg, W.V., depended on to support its dial-up ISP business. But the RBOC wires frequently failed to provide a good connection, causing Bobier to believe that an alternative access method to his customers was necessary.

“I ended up with a staff of something like nine people working about 18 hours a day answering tech support because of phone-line problems,” he said. “When I looked at the cost of the phone lines and the cost of supporting the poor quality of the phone lines, I realized that's where all my money was going. I needed a way around.”

Thus, long before the term Wi-Fi was coined, Bobier developed several broadband wireless technologies in the 2.4 GHz band that was the foundation of a successful business.

“We built a very effective citywide network and started selling broadband service in 1997. I was selling 1.5 Mb/s speeds for $29.95,” he said. “I couldn't put it up fast enough. I covered my town, the neighboring town and then two more towns.”

While the wireless link was better than Bell Atlantic's copper lines, it was far from perfect — access points cost almost 10 times more than they do today, making the economics of a 2.4 GHz network even more challenging. Instead of dealing with multiple access points, Bobier wanted to cover a town with a single base station, like the systems he worked with in the Navy and as a land-mobile-radio dealer.

One snowy night in November 1999, the answer to the problem came to Bobier during one of his frequent midnight reading sessions in his country log house in St. Mary's, W.V. While reading Stephen Hawkings' “A Brief History of Time” and musing about Albert Einstein's Nobel Prize for explaining the Edison Effect, Bobier had a revelation.

“It just occurred to me that the least amount of radio energy I could have is one photon — one wavelength — and the least amount of data I could have is one bit,” Bobier said. “It just struck me that there was a correlation there.”

Bobier said the notion so inspired him that he began doodling and taking notes furiously for more than an hour: “I was so high then, there was no way I was going to bed.”

Filled with inventive adrenalin, Bobier decided to put his idea to its first litmus test by awaking his wife, Angie, during the early-morning hours.

“She's not a technical person at all, but she's smart,” he said. “I drew this correlation for her between one particle of light and one bit of information. I explained this whole idea, and she started asking questions. Finally, she said, ‘Yeah, I think you might have something.’”

Bobier decided to take his single-cycle radio theory to Rick Mooers, who had bought his wireless broadband ISP a couple of months earlier.

“I brought the idea to [Mooers] and told him that it was a long shot,” Bobier said. “There was a lot I didn't know yet, but if my intuition was right and my understanding was right, this would potentially be a groundshaking thing.”

Mooers agreed to fund six months of initial testing, which was successful enough to convince Bobier that a single-cycle radio system could be built. That prompted additional funding from Mooers and the establishment of a lab in Ft. Lauderdale, Fla.

By fall 2003, the xG Technology team had resolved most aspects of the system but continued to get mediocre-to-disappointing performance from all its receiver designs — a fact that a technical consultant to xG Technology's then-CEO Mats Wennberg noted repeatedly during Bobier's visit to Stockholm, Sweden.

After a day full of “razzing” by the consultant, Bobier was admittedly rattled about how he would get the receiver to work correctly. He returned to this “crummy little European hotel,” only to find that a stuck window was letting all the cold night air in his room. Frustrated and cold, Bobier laid on his bed thinking about the receiver when he was hit by another piece of midnight inspiration.

“I stopped thinking in normal terms, slowed everything down and started visualizing the waveform in real time,” Bobier said of the patent-pending design. “All of a sudden, it came to me exactly what I needed to do. … It's so incredibly simple.”

Too simple, in fact. When Bobier explained the concept to chief engineer Nadeem Khan, the notion was not met with enthusiasm.

“So I just went back to work at my desk for a week and watched him struggle [with receiver designs], making all the same mistakes I had been making,” Bobier said. “Finally, I turned to him and said, ‘Are you ready to simulate my circuit?’

“He said, ‘Yes,’ and went to work. It only took us 15 minutes to simulate, and the result was dead-on perfect. And that's the receiver we use today, with virtually no changes at all.

[02/07/05] WAN technology promises lower power, faster speeds.

Broadband wireless base stations could get much cheaper, and phones could have a talk-time of days, if a new, long-distance UWB-like wireless technology is for real.

xMax, from xG Technologies, sounds like a contravention of the laws of physics. Yet the company has promised a public demonstration in September, delivering 40 Mbit/s over 15 miles, using less than a Watt of power, at low (sub-GHz) frequencies that have so far been considered unsuitable for broadband.

For now, the credibility of the technology rests on a few web references and the word of a Princeton professor. But xG are doing a better job of explaining their technology than previous companies that have turned out to be snake oil.

"Our unique benefit is we can use narrow channels [at low frequencies] where you get better propagation characteristics," says Joe Bobier, the technology's inventor, and president of xG Technologies. "If you can use these frequencies, yet still be broadband, then you compare favourably with fixed wireless technologies that are doing things in the microwave area where you have line of sight issues."

Magic - or reality?
Sub-GHz frequencies penetrate well, and so can be used for communication without the line-of-sight issues that occur at higher frequencies. However, they are sliced into small narrowband channels by the licensing authorities, so no-one can get hold of enough spectrum to send high-throughput (broadband) data in this spectrum by conventional means. Shannon's Law requires a wider band of spectrum to carry more data.

xMax uses one narrowband channel, but sends more data than could possibly be fitted into that channel - and yet it does not break the laws of physics, claims Bobier. The narrowband channel does not carry the payload, it is just used to co-ordinate and synchronise the sender and receiver. The information is then transmitted in a wideband signal (which xG calls a Flash Signal), at very low power.

"Our technology uses a narrowband channel, and places a carrier there for an extremely precise clock in the receiver," says Bobier. "The transmitter also transmits information in side bands, at levels lower than ultra-wideband. We are able to get performance comparable to a wideband licensed trasmission."

The data is sent out-of-band, but at power levels that are lower than those permitted for unintentional out-of-band signals by normal transmitters. "The levels of out-of-band emissions are highly regulated," says Bobier. "Ours are even lower."

The synchronisation allows the receiver to pick out signals below the noise floor, claims Bobier, so a signal that is not registered by other spectrum users, can be picked up by the intended recipient. There is some explanation in a FAQ at xG, and an article in Microwave Engineering.

Using power levels lower than the out-of-band leakage from normal transmitters makes it somewhat similar to ultra-wideband (UWB - read our coverage), which operates over short distances, using power levels lower than those which are permitted (by the FCC and other regulators) to leak from non-transmitting devices such as stereos.

In September xG promises to have a base station between Fort Lauderdale and Miami, covering a radius of 15 miles, with a shared bandwidth of 40 Mbit/s, all provided by less than one Watt, using the unlicensed 900MHz ISM band. The first demonstration will be omnidirectional, but greater throughout would be possible with a sectorised station, or using a wider noise-level band.

Other benefits
"What Joe has invented can use 100,000 times lower power than other technologies," says xG's chairman Rick Mooers. Besides allowing cheaper base stations for broadband, it has other benefits.

The low-power channel it uses can overlap with other users, because it is below the noise floor, creating "dual use" for the radio spectrum, claims Mooers.

It also has implications for battery life. "Instead of having a 600mW handset, you could have 1mW or 0.5mW handset, says Bobier. This would give a talk time of days. Low power handsets would also neatly sidestep allegations of medical harm from handsets, the pair assert.

The technology can also be used on wireline systems, sending data further over ADSL, and allowing more channels on broadband wired and cable systems, they claim.

Who will use it?
As the name implies, xMax is intended as a "beyond-WiMax" technology, and xG hope to propose it as a potential new physical layer for WiMax. "A great deal of the WiMax standard is essentially protocols, only a little is the physical layer," says Bobier. "This could be super-WiMax."

In the prototype, xG will; use portions of the published WiMax specifications, making this a part-WiMax, pre-XMax network. The name xG is, as you might have guessed, a similar play on the term 3G.

Although currently proposed for WANs, xMax could also be used at LAN and WAN distances "We can go 63 ft with 0.5 pW," says Mooers. "It could run for years on a watch battery." So we can possibly expect x-Fi and and xTooth in the future...

But is it real?
"People will understandably be sceptical as they are with all disruptive technoligies," says Mooers. "We've had five years of rigorous testing, and we say come see it. We are very close to a field demonstration now. That's why we've decided to stick our head up and talk."

The technology is endorsed by Stuart Schwartz, professor of electronic engineering at Princeton University, who also serves as an advisor to xG, and co-wrote the article in Microwave Engineering.

xG will be formally launched in November, and presented at the 3GSM show in Barcelona next Spring. At this point we will start to see the independent testing that will tell us if this is more than a pipedream.

1. Is the name xG^TM meant to imply a comparison with 3G wireless technology??

Yes. xG Technology, LLC^TM intelligently pushes radio technology to its theoretical limits - far beyond that of third generation (3G) or even fourth generation (4G) technologies. Hence, the name xG, or X^th generation. xG Technology also produces performance improvements over other technologies in multiples – 10x, 20x, 30x, 100x. That’s another reason for the name. To be clear, 3G and 4G wireless technologies don’t directly define modulation systems, so the comparison made here is to the core modulation techniques used in those technologies.

xMax is a novel modulation and encoding technology that boosts the data rates of all wired and wireless communications. xMax is not a compression technique, but rather a synergistic mix of two well-established communication approaches that dramatically improves spectrum utilization. By combining elements of traditional narrowband carrier systems with non-interfering elements found in low-power wideband systems, xMax delivers data rates orders of magnitude higher than other broadband approaches.

The technology's name has been recently changed from xG Coded Modulation (xGCM^TM) to xMax as it prepares to leave the laboratory for the marketplace.

xG Flash Signaling is the micro power wideband signal used by xMax to convey information. xMax uses xG Flash Signaling to transmit wideband data at power levels well below the static noise found in the atmosphere. Because radio frequency (RF) receivers can only detect signals above the noise floor, xG Flash Signals are completely non-interfering to neighboring systems.

Since every radio technology produces similar emissions the Federal Communications Commission (FCC) has set regulatory limits that prevent one system from interfering with another’s operation. xG Flash Signals fall as much as 100,000 times below these regulated power limits and up to 10,000 times below that of ultra wideband (UWB) emissions.

In addition to its advanced modulation technology, xMax uses a unique encoding system that dramatically reduces sideband emissions while multiplying the data throughput rate. This technique is called Index-N.

xMax offers a feature called Variband. This can be useful to adjust the data throughput rate on-the-fly.

S/Nr stands for the Signal to Noise Ratio. Every communications system is subject to interference by noise. Some systems are more susceptible than others. The S/Nr test is a measure of the sensitivity of the receiving system to noise. Eb/No is also a measure of signal and noise. Our technical papers relate noise performance using both S/Nr and Eb/No for the readers convenience.

Shannon’s Law is the relationship between channel capacity C (bits/sec) or maximum data rate, bandwidth B (Hz) and Signal to Noise power ratio S/N, as summarized in the Shannon-Hartley Theorem: C = B log ₂ (1+S/N). The narrowband channel allocation that xMax uses to coordinate reception of its wideband xG Flash Signal is not the system's information-bearing bandwidth. xMax does not violate Shannon's Law.

BER stands for Bit Error Rate. All digital communications systems are subject to the loss of data or “bits” during the act of transmission. The BER is a ratio of bits that are lost versus bits that are successfully transferred. BER varies with signal to noise ratio. The lower the BER for a given S/Nr, the better. This is just one area where xG excels.
Click HERE to open a new window with a full size BER plot.

RF stands for Radio Frequency. Most communication systems send data via radio frequencies; one exception is fiber, which sends data via light pulses. xMax is designed for RF communication systems and does not work on fiber.

Modulation is method of transmitting data by systematically changing a carrier radio signal in a manner that can be detected and interpreted by a receiver.

The core research & development underlying xMax is complete. The company has developed working reference hardware designs. The modulation and demodulation circuitry can be integrated into FPGA or ASIC and will be integrated into equipment such as computers, TV’s, phones, cell phones, base stations, etc.

2. I understand xMax can be used for both wired and wireless applications. Why would wired applications be an attractive market?

xMax has dramatic implications for the DSL and cable industries. xMax enables delivery of new services such as high definition television (HDTV), video on demand, Internet protocol television (IPTV), voice over Internet protocol (VoIP)—all with new reach and functionality.

Because of its inherent nature xMax can be interleaved among existing cable RF channels allowing operators to offer new services in an incremental fashion without the interruption of existing services. Since xMax can operate over existing network mediums, requiring only new line end-points, such new services can be added quickly—allowing operators to increase average revenue per user (ARPU) on a positive cash flow basis.

In this respect, xMax is particularly important for telecom firms that rely on wireline facilities. The higher capacity signals that xMax produces allows for much higher quality of service (QoS) levels than do current network standards. In fact, xMax is so robust that signal capacity improvements to cable networks enable the delivery of over 1,000 channels of enhanced services. In the DSL space, xMax delivers improved data-rates while increasing the reach of DSL up to an estimated 72,000 ft. from the central office. As such, xMax provides a cost-efficient avenue for voice, video, and data services into enterprise and consumer markets

xMax complies with all regulatory thresholds set by the Federal Communications Commission (FCC), that prevent one system from interfering with another's operation.

See the report from Blooston Mordkofsky verifying xMax is compliant with existing FCC rules. (By request)

4. For broadband wireless applications, how far can xMax transmissions reach?

Because xMax can be deployed at low, far-reaching frequencies it is particularly attractive for broadband wireless access (BWA) services. Like the term implies, “broadband” services require very broad swaths of spectrum in order to deliver high-speed data. Given that the lower portion of the spectrum has already been divided into numerous narrow channels that cannot be easily re-bundled, broadband deployments to date have been limited to higher microwave frequency bands (upwards of 2GHz to 30GHz). For traditional broadband technologies, deployments in these microwave bands are an expensive proposition. Radio waves do not propagate very far at high frequencies nor are they proficient at passing through buildings or other dense objects. This requires service providers to build expensive infrastructure closer together than would be required at lower frequencies.

Focusing on a business model that utilizes easily obtainable VHF and UHF RCC licenses for frequencies, conservative estimates in large metropolitan areas put one base station every 35 miles. In other words, 4 base stations would cover the entire Washington D.C. metropolitan area including Maryland and Northern Virginia. Because the propagation characteristics of low frequencies allow them to pass through dense obstacles, deployment of xMax in the VHF and UHF bands completely eliminates the line of sight issues that are problematic with higher frequency broadband technologies.

Ramifications of this are enormous. xMax can be used by public safety, police, homeland security, and emergency services to form large area wireless broadband networks. It can be deployed by commercial fleet operators to equip vehicles with the equivalent of a 10 base T network. xMax allows Metropolitan Area Networks to deliver, from a single tower, wireless backhaul to hotspots across an entire city. The emergence of a true retail fixed wireless model becomes possible as xMax enables the design of affordable “over the counter” modems that eliminate the need for high gain antennas or expensive outside mounting. With line of sight no longer an issue, broadband for the user becomes portable, from home to car to office to pocket.

xG Technology, LLC has maintained an invention disclosure program and a vigorous Intellectual Property protection program since its inception. xG Technology employs in-house patent counsel and has filed several patents related to xMax. Additional disclosures are reviewed by Howrey, Simon, Arnold & White and timely filed with the USPTO. Howrey, Simon, Arnold & White, LLC has been:

As companies scramble to develop 3G telephony and data services, the need to acquire additional radio spectrum from the FCC has become a pressing issue. To accommodate increased demand for data services, the radio spectrum bandwidth needed to transmit data must increase proportionally. Essentially, in order to effectively transmit more data, the speed of data carried must also increase, which means that the allocated channel width must also be increased.

Since the demand for spectrum exceeds today’s supply, competitors have driven up the price for this scare commodity. As such, the cost of spectrum licenses constitutes an increasingly high percentage of the overall cost of delivering wireless services. Despite these high costs, in the U.S., no single block of radio spectrum remains unallocated in sufficient size to meet the needs of 3G services.

xMax solves this problem by dramatically reducing the amount of allocated spectrum required to transmit data. xMax uses a narrow channel allocation of dedicated spectrum to coordinate reception of its non-interfering, xG Flash Signal. By using xG Flash Signaling to convey wideband data below the noise floor, xMax allows for efficient spectrum reuse by numerous users in a manner that solves the spectrum crunch. Because xG Flash Signaling accomplishes this with far less “out of band” energy than traditional modulation systems such as CDMA and GSM, xMax helps to "clean-up" the spectrum for more efficient use than is currently realized.

Based upon inherently simple but proprietary framework, xMax viably meets the tremendous demand for cost effective broadband solutions. xMax has the capacity to revolutionize all electronic communications and connect all media, data, appliances, etc. Applications are virtually endless. Initial applications are expected to focus on high-end markets where a greater present demand exists for high-speed communication solutions, as well as in applications that can afford to pay higher prices.

The initial market applications are expected to include, but are not limited to, the following:

License holders will determine the ultimate uses of xMax. Applications are anticipated to range from low cost consumer products to highly sophisticated installations in both wired and wireless markets. In reaching the consumer market for wireless broadband, the three most common impediments to deployment: line of sight restrictions, high consumer equipment cost, and carrier truck rolls (associated with user installation) become non-issues with xMax.

Numerous physical tests verify the results of both qualified analysis and comprehensive computer modeling. Demonstration devices are surprisingly immune to AWGN and co-channel interference. Qualified interested parties are invited to participate in hardware demonstrations and analysis, as well as a review of numerous technical white papers.

2. What is the error correction scheme used in FSK, QAM, AFSK, PSK or other modulation schemes?

No modulation approach employs error correction as an inherent part of the technology. Error correction schemes are installed in the data stream before modulation is applied. Likewise, they are used after the demodulation.

Modulation is a way to transmit data by systematically changing the radio signal in a manner that can be detected and interpreted by the receiver. By data, we mean payload data in addition to any formatting or error correction bits that have been added to the data stream. If information for error correction is added to a data stream the space available for the payload is reduced. That is independent of how the radio signal is modulated.

BER will always be variable because as the environment changes, the variables of signal strength, noise, fading and multipath will change. Tests already done have clearly shown that xMax is quite robust in the presence of noise. Since noise is the predominant factor in BER performance, it’s probably safe to assume that the BER of working systems, when used within ordinarily acceptable system design parameters, will be quite good. Remember that the "system control" areas are defined by the application. A set-top box will have different system control mechanisms than a wireless Internet connection. Even vastly different would be a wireless phone where system control will integrate many features and functions.
Click HERE to open a new window with a full size BER plot.

No. In fact since the BER and noise susceptibility performance is excellent, one should expect to use lower powered transmitters than one would otherwise. This translate to longer battery life, more forgiving link budgets and longer range networks.

Hybrid technology combines aspects of narrowband carrier systems and low-powered wideband PPM.

With the increased demand for wireless technologies, industry leaders are looking to see how Washington policy makers will confront the vexing problem of RF spectrum scarcity. Of late, the FCC has opted to relieve the pressure by making additional swaths of licensed spectrum available for commercial use, typically in the higher microwave frequencies. The Commission's move this winter to make the 3.65- to 3.7-GHz band available for nationwide license with minimal regulatory requirements is one such example.

[05/13/05] xG Tests Low-Power Broadband System

xG Technology LLC has come out of stealth mode and conducted a field test of its broadband technology, which is designed to operate over wireline and sub-Gighahertz-frequency wireless infrastructure.

The test marks the debut of the company's new xMax technology, which combines coding and demodulation techniques at the physical layer to enable low-power broadband communications.

The test was conducted using the VHF band — the portion of the band typically used for paging services. An xMax transmitter and receiver, along with ground-level antennas, were used for the test. Transmitting at 0.0005 Watts, the system was able to deliver data at a distance of more than one mile, according to an announcement issued by the company.

Joe Bobier, president of xG Technology and inventor of the xMax technology, said that xG conducted the test using the 169.44 MHz frequency. The company had an experimental license issued by the Federal Communications Commission.

The test used omni-directional antennas placed at six feet and 12 feet, Bobier said. Omni-directional antennas represent a less expensive solution than using sector panel antennas.

Ground-level testing typically presents the challenge of maintaining the link through obstacles on the horizon, such as buildings. One of the advantages of the xMax technology is that it uses the lower frequency bands, which enables better penetration compared with the upper bands.

For the test configuration, xMax was able to deliver data communications at 6 Mbps, according to Bobier. However, he said that the technology in its first generation has demonstrated 42 Mbps speeds.

Bobier said that the xMax technology "might be in the same species" as ultrawideband technology (UWB), which is another low-power, high-capacity technology. However, Bobier said that UWB has not proved to be very practical and that a high aggregation of UWB may cause interference.

The xMax technology concentrates more than 99 percent of its power within a narrowband carrier, while keeping its sideband energy at micropower levels, according to the company's announcement. The system operates well within the FCC's power regulations, Bobier said.

The xMax technology potentially compares favorably with other broadband wireless technologies, such as 802.11 Wi-Fi gear, which typically transmits at 1 Watt, reaching a distance of 300 feet under comparable non-line-of-sight conditions.

Bobier suggested that a single tower using xMax technology could cover all of Miami and Ft. Lauderdale. In contrast, Wi-Fi technology would require multiple towers to do the same.

Bobier said that he has long-standing experience working with fixed wireless systems operating in the 2.4 GHz band. He conceived xMax as a way to achieve broadband at lower power levels. The company has been in stealth mode for five years and is now negotiating with other companies concerning the technology, Bobier said.

-- Kurt Mackie

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