Showing posts with label WiMAX. Show all posts
Showing posts with label WiMAX. Show all posts

Wednesday 10 October 2007

Shaky foundations of WiMAX

Dov Bar-Gera, WiMAX Telecom CEO, says "technical hold-ups
could delay his commercial launch of mobile WiMAX in Austria, Slovakia and Croatia".
I was under the impression that WiMAX was all ready to steal the march from LTE camp and the standard was much faster and simpler than 3G+ because it doesnt care about backward compatibility.
Earlier blog titled, "Will WiMAX compete with 3G+" did mention the shortcomings of WiMAX compared to 3G+ but this latest article from Telecommunications Magazine gives an interesting insight into the WiMAX world:
Last March, the GSM Association, a lobby group for GSM technology, published the results of a report commissioned from consultancy Arthur D. Little, which purported to shred the business case for mobile WiMAX in markets where 3G is already in service.
Ericsson, a confirmed WiMAX opponent, is equally dismissive. Mikael Halén, director of government and industry relations for the Swedish vendor, reckons HSPA, a high-speed version of 3G, will have 20 times as many subscribers as mobile WiMAX by 2011 (600 million vs. 30 million).

Australia’s incumbent operator Telstra has also snubbed WiMAX in recent weeks. In July—still smarting from the Australian government’s decision to award a sizable broadband contract to chief rival Optus—Telstra dismissed the capability of the WiMAX technology Optus plans to launch, arguing it is "unproven" and "vastly inferior" to its own HSDPA service.

None of this has deterred some big operators from announcing varying levels of commitment to WiMAX technology over the summer months. In the United States, for example, Sprint Nextel has upped the scale of its investment in a nationwide network to US$5 billion from about $3 billion. And in Europe, UK-based Vodafone has surprised some by joining the WiMAX Forum, the main lobby group for WiMAX
Led by Ericsson, 3G vendors are trying to encourage 3G operators to include the LTE (long-term evolution) standard in their development plans. Promising speeds to rival those of future WiMAX technology, LTE is being promoted as an evolution of 3G technology and, therefore, a more natural choice than mobile WiMAX for an existing 3G operator.

The trouble is, LTE has not yet been standardized. In the absence of defined technical specifications, its critics have been able to cast doubt on whether it has much in common with 3G at all. They point out it uses a different air interface called OFDMA—which, coincidentally, is also used by WiMAX—and so will not be able to reuse much 3G infrastructure, making it as costly a deployment option as mobile WiMAX. If operators are persuaded by this argument and already see the need to plan for a post-HSPA future, they are unlikely to wait for LTE.

But Ericsson sternly repudiates LTE criticisms. "We will have LTE modules that fit into existing 3G base stations," says Halén, who expected an LTE standard to be released in late September (nothing had been announced when Telecommunications went to press) and commercial deployments to appear in late 2009, just 18 months after Sprint Nextel aims to launch its first mobile WiMAX service. "For an existing 3G operator, it will be far more expensive to roll out WiMAX than LTE," he insists.

3G’s long commercial lead in some markets is the one challenge mobile WiMAX may face. More than 100 operators have launched the relatively immature HSPA in 63 countries. This appears to give 3G a major advantage over mobile WiMAX on economies of scale.

As a result, WiMAX operators may find it hard at launch to compete with 3G on price, especially in markets such as Austria, where intense competition between the country’s 3G providers has driven the monthly price of an HSPA service down to as little as €15 ($20). The challenge is recognized by WiMAX Telecom’s Bar-Gera, who is gunning ultimately for about 400,000 mobile WiMAX customers across Austria, Slovakia and Croatia.

"Unfortunately we will have to adapt to this price level," he says. "It will be difficult, but we will match it."

Saturday 29 September 2007

WiMAX World Highlights



WiMAX is strating to be rolled out and this will definitely give it an advantage over LTE/UMB.

Motorola demoed its new WiMAX 802.16e mobile handoffs across a Sprint brand Xohm prototype network on a boat cruising downtown Chicago’s skyscraper-canyoned mid-town river. Not only was it good clean fun for the attendant pundits, punters and analysts, it was an impressive real-life demonstration of an important nascent technology that they could just as easily, and less expensively have unveiled in the controlled environs of the conference hall – boring as hell like usual – but they did not. Motorola and gang literally went the extra mile by also mounting the new WiMAX exhibition on a rolling Chicago public transit coach caroming about the city’s elevated metro tracks at 50 miles per hour, all the while delivering pretty seamless mobile apps like web browsing, VoIP, video streaming and Mobile TV.

Elsewhere, NextWave Broadband and Huawei Technologies also this week announced the interoperability testing of NextWave’s 802.16e mobile WiMAX chipsets and Huawei’s WiMAX infrastructure equipment in San Diego.

Telsima announced that the company’s Indian WiMAX Rollout was awarded the Best of WiMAX World USA 2007 Award for its StarMAX™ Solution in the WiMAX World Digital Cities Deployment category by the xchange magazine. The annual awards were presented in a late evening award ceremony on September 26 at the WiMAX World Conference held at Chicago on Sept. 25-27, and recognized leaders in the development and deployment of WiMAX technologies. In its second year, the awards received more than 80 submissions and Telsima pipped at the post several strong contenders to establish its leadership.

Telsima has established leadership position in WiMAX by enabling multi-city rollouts for Tier 1 operators, including, Reliance Communications and Tata-VSNL in India. The WiMAX rollouts, with thousands of base station sectors already shipped, support several advanced functionalities, like, MIMO & STC Antenna Diversity in support of NLOS deployments. The equipment installed in rollouts covers WiMAX Forum Certified™ Telsima BS StarMAX 4120, 6100 and 6400 and SS StarMAX 2140 and 2150.

Nortel set up one of the biggest booths at WiMax World on the show floor, and announced that it is working with the Choctaw Electric Cooperative and Pine Cellular to bring WiMax to southeastern Oklahoma and other rural areas where it is not economically feasible to build a wired network.

Another category of devices under development are ultra-mobile PCs, or mobile Internet devices, which are about the size of a VHS tape and function somewhere between a laptop and a mobile phone. Samsung displayed a "butterfly" device that has three folding sections, including two that form a full keyboard used with a small screen. Nokia has an ultra-mobile device expected to launch next year with Intel technology inside. It was in the dashboard of a Mini Cooper as an entertainment center.

Meanwhile the Koreans revealed world's first mobile WiMAX gaming device. Called the G100 and developed by Posbro, a subsidiary of Posdata (itself a subsidary of huge Korea steel maker Posco), it's just been revealed at the WiMAX World USA 2007 exhibition in Chicago.In terms of hardware specs, the G100 features a widescreen four-inch touchscreen that slides up to reveal four buttons which act as a D-pad, four face buttons and a mobile-style nub. There are also two shoulder buttons.As for network technology, the G100 supports mobile WiMAX – itself a cell phone-style high-speed technology equivalent to 3G and 4G mobile networks – as well as old fashioned Wi-Fi and Bluetooth. This, Posbro says, will enable users to select the most appropriate network to make an internet connection.

Finally, Clearwire had a minimal presence. It didn't have a booth or splashy banners hung from the ceiling. It didn't host a cruise on the Chicago River to show off its service. But the conference did pause Thursday to hear a progress report from the Kirkland-based company.

Clearwire, founded by wireless entrepreneur Craig McCaw, has been in business four years and serves more than 40 markets in the U.S. and a handful of cities in Europe.

The company offers a precursor to WiMax technology. Users receive a modem — about the size of a hardback book — that can be used anywhere in a service territory, though not on the go, such as in a moving vehicle.

Clearwire's progress differs from the rest of the industry, which is waiting to build networks based on true mobile WiMax technology, expected to be available early next year. "The difference with Clearwire and other folks in the room is that while others are planning, we are in service today," Richardson said.

In his speech, Richardson offered a rare glimpse into operations of a company that usually prefers to stay out of the spotlight and say little. Here are a few points worth noting, gathered from his presentation and a one-on-one interview:

  • Clearwire has about 300,000 subscribers. In August, 41 percent of its customers migrated from cable Internet access and 29 percent from DSL.
  • The combined total is about 10 percent more than in the first quarter, when 59 percent of customers moved from DSL or cable.
  • Clearwire is starting slowly to roll out mobile WiMax — which can be used on the go — into new markets, including Portland.
  • Deployment of true mobile WiMax is going well in Portland, Richardson said. In April, Clearwire completed the first phase, involving 15 square miles. It's now focused on a beta network covering 145 square miles.
  • In 2008, it expects to see laptops with embedded chipsets, as well as WiMax-enabled handsets.
  • As for a WiMax business model, he said that will likely evolve as networks become available. "I believe the future is driven by the types of things you do at home today and want to do on the go, but we have to provide the connectivity to enable the business model."
  • Richardson said a lot of the complexity in the business will be in the back end of Clearwire's network, where it handles billing. As a result, it bought IntraISP, of St. Louis, which will be a subsidiary and be able to sell billing solutions to other companies.

Saturday 22 September 2007

Asian WiMAX Deployments to Threaten 3G Carriers


A number of Asian countries have resolved in recent months to adopt and promote WiMAX, a super high-speed wireless broadband technology which some analysts believe could ultimately threaten existing 3G wireless providers.

With its impressive bandwidth and range, WiMAX has the potential to cover anything from a bustling city to a remote village, and could be useful in both developed markets like South Korea and emerging ones like Vietnam.

The island nation of Taiwan is the latest proponent of WiMAX technology, granting six spectrum licenses in the past months, and pressuring the respective carriers to have their networks up and running within the next 18 months.

Analysts expect WiMAX equipment makers, such as Gemtek Technology Co Ltd., D-Link, ZyXEL Communication Corp., and Accton Technology Corp. to experience significant revenue growth in the coming quarters. Cell phone manufacturers like Samsung and LG are also likely to experience growth, as they begin to release WiMAX-enabled handsets and other devices.

“A key reason (to build WiMAX) is to drive the manufacturing industry for equipment vendors, and to create and nurture this ecosystem quickly,” commented Bill Rojas, the director of telecom research at International Data Corp (IDC).
Meanwhile in India, Equipment suppliers and operators are readying plans for the commercial rollout of WiMax broadband services in India though the Centre continues to dither on the broadband policy.

Said Protip Ghosh, vice-president, sales and marketing, Telsima Corp, which develops and provides WiMAX-based Broadband Wireless Access (BWA) and mobility solutions: “Though the government has set a target of 20 million by 2010, wire line will be able to cater to only five million and the rest will have to be met by wireless technologies such as WiMax.”

In fact, the technology is already being deployed by telecoms for hooking up their backhaul connectivity (between telecom towers) while widespread testing is on for commercial rollouts later.

BSNL, Reliance Telecommunications, VSNL, Bharti Televentures, Aircel, Sify, to name just a few, have already rolled out limited WiMax networks. Others like Tata Teleservices are testing networks at various places.

In fact, the biggest event being watched is the BSNL tender for 10,000 WiMax base stations slated to open sometime soon which could open the floodgates.

Telsima is looking to rollout a massive 10,000 WiMAX base stations and 1,00,000 WiMAX subscriber stations this year, most of them in India, according to Ghosh. Much will depend on how soon clarity on the broadband policy can be achieved by the Centre.

Interestingly, Telsima is already a supplier to VSNL and Reliance while Alcatel is currently in talks with the former to help in the commercial rollout of the technology.

“We are proud to be the first company to launch WiMax-based services in India,” Vinod Kumar, president (global data & mobility solutions), VSNL, told DNA Money. VSNL will extend its WiMax network to about 120 cities across India for enterprise customers and in five cities for retail customers by the end of the current financial year.

BSNL, which has undertaken pilots at 14 locations, is looking to roll out a WiMax network across 1,000 cities in the country.

In October 2006, Chennai-based mobile operator Aircel launched its broadband wireless access on WiMax and by December 2007, it will cover 44 cities.

An interesting thing to the whole broadband play will be the impending showdown between the WiMax players and the 3G lobby which, too, maintains that the WCDMA/HSPA standard is the best for broadband services for a country like India. “In our reckoning, WiMax will have only 5-10 per cent of the market,” said P Balaji, vice- president, marketing and strategy, Ericsson India, which is aggressively pushing the WCDMA technology.

In fact, given that choices have already been made in some 150 odd markets, HSPA will command a 75-80 per cent of the broadband market down in India, he said. However, given that Ericsson does not push WiMax technologies, one could perhaps take the opinion with a pinch of salt.

However, with less focus on mobility and powerful players like Intel aligned on its side, the WiMax lobby could emerge the winner in the long run.

Monday 27 August 2007

WiMAX on display


Vodafone has deployed WiMAX technology in Malta. The island (population 400,000) is one of Vodafone's smallest markets.

The supplier of the network, Airspan, announced in June that Vodafone Malta had deployed its HiperMAX 80216d 'fixed' WiMAX base stations and CPE to offer bundled mobile, fixed voice, and data services to residential and business customers. Since that announcement was made, Vodafone has joined the lead industry organisation promoting and steering WiMAX development, the WiMAX Forum.

According to Pyramid research, "Vodafone, owing to its scale, is an agent of change in the operator community and we expect others to follow its trajectory. With operators present in different markets and looking for new revenue sources, there is no 'one-size-fits-all' technology, but the wrong technology can set an operator back years."

The research firm adds that "in catering to the needs of different markets and customer segments, operator networks will comprise diverse access technologies, each optimised for certain geographies, demographics, and services. For the WiMAX champions this is good news; for LTE backers it is a strong warning that should lead to increased R&D budgets for the next few years—in both camps.


In other news, Samsung Electronics will demonstrate the next generation telecommunications technologies at its annual international forum, which will shed light on what they call as global 4G technologies and gadgets.

This year’s Samsung 4G Forum will draw more than 130 influential industry leaders and service providers from 26 countries. It will mark the first time that all three candidate 4G technology _ IEEE 802.16m (Mobile WiMAX), 3GPP2 Ultra Mobile Broadband (UMB) and 3GPP Long Term Evolution (LTE) _ will be seen with each other.Each of the 4G technologies has a head cheerleader, with Intel supporting WiMAX, Ericsson touting LTE and Qualcomm preferring UMB. IEEE 802.16m WiMAX, UMB and LTE are expected to be initially implemented in 2010.

I think for companies like Samsung to break into new markets, its very important to use the term 4G. Lets hope that they all succeed.

Tuesday 21 August 2007

XOHM = ZOOM + ROAM


Sprint (US) is getting ready to unleash a WiMAX network unto the masses. The quirky news is that they've decided to name it XOHM. The 4G high-speed data network will be based on WiMAX technology, and they plan on sharing the network with Clearwire.

By the end of 2008, the XOHM (pronounced "zoam"... sort of like a zoom-roam hybrid) network will be able to reach 100 million people. If everything goes according to plan, this number will expand to 125 million by the end of 2010. The initial building of the infrastructure will cost Sprint about $2.5 billion.

The first cities to experience XOHM will be Chicago, Baltimore, and Washington when they get their hands on the soft launch at the end of this year. The full commercial WiMAX launch is scheduled for "the first half of 2008."
In another announcement, Sprint Nextel Corp., the third largest US wireless service firm, has announced plans to spend nearly $5 billion by the end of 2010 on a new network based on the emerging high-speed wireless technology known as WiMax, Reuters reported. The company said that it expects spending on the network through the end of 2008 to be at the low end of its previously announced estimates due to its agreement to connect its network with Clearwire Corp., a small wireless service provider. Sprint said it expects to spend $2.5 billion on the network through the end of 2008 compared with its earlier estimate of $2.5 billion to $3 billion. Sprint expects to reach a potential 100 million customers in that time, with the company providing coverage to 70 million people and Clearwire covering 30 million people.
To read the Press release for XOHM click here.
Official XOHM Website here.

Prepare for WiMAX 2.0



I was completely unaware of IEEE 802.16m which is promising speeds upto 1Gbps. Only when someone asked me what my opinion was on this i did some digging in this.


IEEE 802.16m promises to deliver speeds up to 1Gbps and be backward compatible with 802.16e-2005 (mobile WiMAX) solutions. The 802.16m group should wrap up the technology development phase in 2007. Similar to existing mobile WiMAX, 802.16m will use multiple-input/multiple-output (MIMO) antenna technology. The idea with 802.16m, though, is to increase bandwidth by using larger MIMO antenna arrays.


The 802.1m group is targeting ratification and finalization of the standard by late 2009. So, we’re still a couple of years (or more) from having a gigabit version of WiMAX. As compared to other IEEE 802 standards development, such as 802.11, this is an aggressive schedule. In my opinion, these will be difficult dates to hit, especially with the requirement for being backward compatible with 802.16e-2005.


The advantage of 802.11m to cellular companies is that it could allow the convergence of 3G and 802.16 into a single 4G technology for mobile and fixed applications. This would enable cellular companies to offer service, such as IPTV and VoIP, as effectively over wireless connections as they are today on wired networks. This would lead to competition with existing fixed wireless broadband services currently delivered over cable and telephone lines.


Many vendor sources however, have expressed some skepticism about the speed with the work can be completed (the end of 2009 is being mooted as a baked date) and the chances of maintaining backwards compatibility with mobile 802.16 technology. Some folks worry that carriers have unrealistic expectations on how fast new WiMax profiles and interfaces can be developed. "They just walk in, snap their fingers, and expect it to happen," one industry source told us on the show floor yesterday. After all, it took several years for the IEEE to arrive at a satisfactory fixed broadband wireless specification in the form of 802.16d and even longer for the WiMAX Forum to certify interoperability between products using the technology.


Martin has some interesting analysis on his Mobile technology page:


Between today and WiMAX II, there's systems such as WiMAX and LTE which promise faster data rates than those available today by mainly doing the following:
  • Increase the channel bandwidth: HSDPA uses a 5 MHz channel today. WiMAX and LTE have flexible channel bandwidths from 1.25 to 20 MHz (Note: The fastest WiMAX profile currently only uses a 10 MHz channel today for the simple reason that 20 MHz of spectrum is hard to come by). So by using a channel that is four times as broad as today, data rates can be increased four times.
  • Multiple Input, Multiple Output (MIMO): Here, multiple antennas at both the transmitting and receiving end are used to send independent data streams over each antenna. This is possible as signals bounce of buildings, trees and other obstacles and thus form independent data paths. Both LTE and WiMAX currently foresee 2 transmitting and 2 receiving antennas (2x2 Mimo). In the best case this doubles data rates.
  • Higher Order Modulation: While HSDPA uses 16QAM modulation that packs 4 bits into a single transmission step, WiMAX and LTE will use 64QAM modulation under ideal transmission conditions which packs 6 bits into a single transmission step.
By using the techniques above, LTE and WIMAX will be able to increase today's 2 MBit/s to about 20-25 MBit/s. That's still far away from the envisaged 1.000 GBit/s. To see how to get there let's take a look at what NTT DoCoMo is doing in their research labs, as they have already achieved 5 GBit/s on the air interface and have been a bit more open at what they are doing (see

here and especially here):
  • Again increase of the channel bandwidth: They use a 100 MHz channel for their system. That's 4 times wider than the biggest channel bandwidth foreseen for LTE and 20 times wider than used for today's HSDPA. Note that in practice it might be quite difficult to find such large channels in the already congested radio bands.
  • 12x12 MIMO: Instead of 2 transmit and receive antennas, DoCoMo uses 12 for their experiments. Current designers of mobile devices already have a lot of trouble finding space for 2 antennas so a 12x12 system should be a bit tricky to put into small devices.
  • A new modulation scheme: VSF spread OFDM. This one's a bit mind bogelling using CDMA and OFDM in combination. Wikipedia contains a description of something called VSF-OFCDM which might be a close brother.


More Information available at IEEE 802.16 Task Group m (TGm) page.

Monday 13 August 2007

Beginning of the Cablefree world


With UWB becoming popular and more devices about to be rolled out, the cable connections between TV, VCR, DVD players, Camcorders, etc can be a thing of past.

In UK, OFCOM removed the restrictions for the use of UWB devices upto a range of 30 metres. In the US and Japan, UWB home hubs are a popular way of sharing domestic broadband.

Ultra-Wideband (UWB) can be used to send huge amounts of information between electronic devices, making it suitable for connecting items such as digital TV decoders and DVD players to television sets, or digital cameras to computers.

It could also be used to wirelessly link satellite dishes or cable TV connections to set-top boxes, doing away with the need for cables to be poked through walls and run around skirting boards. Satellite broadcaster Sky, for instance, is understood to be looking at whether UWB could be integrated into its equipment.

Described by techies as "Bluetooth on steroids", UWB can operate over distances of up to 30 metres. Japanese electronics manufacturers are already producing modems that use UWB, while Cambridge-based chip maker ARM Holdings has deals with several companies that plan to make UWB devices.

Separately, Vodafone yesterday joined the Wimax Forum which is creating standards and specifications for a new longer-range wireless broadband technology. The company stressed that it is taking a neutral stance on the next generation of wireless technologies, but the move raised eyebrows in the mobile phone industry.

Wimax, which can operate over many miles, is seen as a competitor to another next generation wireless technology, which is being developed by the mobile phone companies and builds on the existing 3G standard. LTE, or Long Term Evolution, is an mobile industry-led project designed to upgrade the existing 3G service. The LTE group is supposed to come up with recommendations on a new standard next month.

Earlier this year Vodafone's chief executive Arun Sarin warned that the process of getting a new wireless standard was taking too long. "As an industry it takes us a long time to get things done - we need to move faster or others will eat our lunch," he said.

Meanwhile The European Commission is opening up the wireless technology market by discarding out-dated rules limiting the areas of available radio spectrum. Next-generation wireless technologies such as BlackBerrys and smartphones work best over low frequencies that, until now, were reserved for GSM mobile phones. According to a statement last week, the Commission will allow new services to co-exist alongside GSM. The aim is to establish a more flexible, market-driven approach to spectrum management, says European Union telecoms commissioner Viviane Reding.

Thursday 9 August 2007

Vodafone plays the WiMAX card

Vodafone announced that it is to become a member of the WiMAX Forum, the organisation which tests and certifies interoperability for products based on the WiMAX standards. Vodafone sees the move as a means of taking a more technology-neutral approach to the future development of its business, by placing WiMAX on a strategic par with 3G LTE for a potential role in the next generation of mobile technology. Although mobile WiMAX is less mature than LTE at present, Vodafone believes it may have an important role to play for some of its national operating companies. Vodafone therefore wants to understand WiMAX better, and to play an active role in developing end-to-end specifications for possible future deployment.

WiMAX standard is often compared to Wi-Fi, though the comparison is unfair as WiMAX isn't based on a 20-year-old wired standard but was designed for wireless use (at least, the bits not borrowed from DOCSIS were). WiMAX offers greater speed and range than Wi-Fi, but most importantly it offers quality of service guarantees that make VoIP and streaming applications easier to manage.

"Our membership of the WiMAX Forum will complement our existing memberships of other key industry bodies such as the GSMA, 3GPP, and the Next Generation Mobile Network initiative," Vodafone global chief technology officer Steve Pusey said.

WiMAX has been heavily pushed by Intel, which intends to build it into laptop chipsets, encouraging rapid adoption of a technology in which it owns key intellectual property.

According to Ovum analysis:

Although a slightly crude generalisation, it's basically accurate to see the WiMAX Forum as the wireless Internet camp; the 3GPP as the wireless telecoms camp. There was a time when those two camps represented philosophies which were mutually exclusive and frequently antagonistic. These days, it makes less sense to see the world in those terms, because convergence between telecoms and the Internet - though far from complete - is now well under way. But at this early phase of the transition to convergence, it's not yet clear whether the predominant technologies and business models will eventually be those of telecoms, or those of the Internet. It's sensible, therefore, to remain interested in (and influential over) both possible outcomes, so long as they both remain possible.

Seen in that context, it seems perfectly natural that a large mobile operator would decide to join the WiMAX Forum. In Vodafone's case, the move is especially logical because of its increasing presence in emerging markets. The prospects for WiMAX to play an important role in the future development of mobile are better in those parts of the world where large numbers of people do not yet have access to telecoms or the Internet. If alternative models are going to take root, it's most likely to happen in areas with less legacy. On the other hand, the telecoms model will predominate for the forseeable future in more mature markets. Vodafone clearly needs to be involved in the development of both types of model, since its business encompasses both types of market.

It says something about the way mobile has changed since the turn of the century, that joining the WiMAX Forum just seems like an obviously sensible thing for Vodafone
to do.

Thursday 28 June 2007

OFDM and OFDMA: The Difference

I was curious as to why IEEE 802.16d (fixed service) uses Orthogonal Frequency Division Multiplexing (OFDM). IEEE 802.16e (mobile) uses Orthogonal Frequency Division Multiple Access (OFDMA). So, what’s the difference between the two, and why is there a difference?

Lets first look at FDM:

In FDM system, signals from multiple transmitters are transmitted simultaneously (at the same time slot) over multiple frequencies. Each frequency range (sub-carrier) is modulated separately by different data stream and a spacing (guard band) is placed between sub-carriers to avoid signal overlap.

OFDM is sometimes referred to as discrete multi-tone modulation because, instead of a single carrier being modulated, a large number of evenly spaced subcarriers are modulated using some m-ary of QAM. This is a spread-spectrum technique that increases the efficiency of data communications by increasing data throughput because there are more carriers to modulate. In addition, problems with multi-path signal cancellation and spectral interference are greatly reduced by selectively modulating the “clear” carriers or ignoring carriers with high bit-rate errors.
Like FDM, OFDM also uses multiple sub-carriers but the sub-carriers are closely spaced to each other without causing interference, removing guard bands between adjacent sub-carriers. This is possible because the frequencies (sub-carriers) are orthogonal, meaning the peak of one sub-carrier coincides with the null of an adjacent sub-carrier.

In an OFDM system, a very high rate data stream is divided into multiple parallel low rate data streams. Each smaller data stream is then mapped to individual data sub-carrier and modulated using some sorts of PSK (Phase Shift Keying) or QAM (Quadrature Amplitude Modulation). i.e. BPSK, QPSK, 16-QAM, 64-QAM.

OFDM needs less bandwidth than FDM to carry the same amount of information which translates to higher spectral efficiency. Besides a high spectral efficiency, an OFDM system such as WiMAX is more resilient in NLOS environment. It can efficiently overcome interference and frequency-selective fading caused by multipath because equalizing is done on a subset of sub-carriers instead of a single broader carrier. The effect of ISI (Inter Symbol Interference) is suppressed by virtue of a longer symbol period of the parallel OFDM sub-carriers than a single carrier system and the use of a cyclic prefix (CP).
The OFDM spread-spectrum scheme is used for many broadly used applications, including digital TV broadcasting in Australia, Japan and Europe; digital audio broadcasting in Europe; Asynchronous Digital Subscriber Line (ADSL) modems and wireless networking worldwide (IEEE 802.11a/g).
Like OFDM, OFDMA employs multiple closely spaced sub-carriers, but the sub-carriers are divided into groups of sub-carriers. Each group is named a sub-channel. The sub-carriers that form a sub-channel need not be adjacent. In the downlink, a sub-channel may be intended for different receivers. In the uplink, a transmitter may be assigned one or more sub-channels.
Subchannelization defines sub-channels that can be allocated to subscriber stations (SSs) depending on their channel conditions and data requirements. Using subchannelization, within the same time slot a Mobile WiMAX Base Station (BS) can allocate more transmit power to user devices (SSs) with lower SNR (Signal-to-Noise Ratio), and less power to user devices with higher SNR. Subchannelization also enables the BS to allocate higher power to sub-channels assigned to indoor SSs resulting in better in-building coverage.

Subchannelization in the uplink can save a user device transmit power because it can concentrate power only on certain sub-channel(s) allocated to it. This power-saving feature is particularly useful for battery-powered user devices, the likely case in Mobile WiMAX.

The WiMAX forum established that, initially, OFDM-256 will be used for fixed-service 802.16d (2004). It is referred to as the OFDM 256 FFT Mode, which means there are 256 subcarriers available for use in a single channel. Multiple access on one channel is accomplished using TDMA. Alternatively, FDMA may be used.

On the other hand, OFDMA 128/512/1024/2048 FFT Modes have been proposed for IEEE 802.16e (mobile service). OFDMA 1024 FFT matches that of Korea’s WiBRO. OFDM 256 also is supported for compatibility with IEEE 802.16d (fixed, 2004).

Friday 15 June 2007

AT&T bets on LTE


AT&T says its next-generation roadmap leads to LTE, though it's evaluating the use of WiMAX technology for backhaul according to a report in Wireless Week.
AT&T's Chris Hill, vice president of Government Solutions for Mobility, commented during an interview at the Wireless Communications Association (WCA) conference that, "LTE provides similar throughputs, so we're taking a wait-and-see approach to WiMAX. We just don't see the value proposition for mobile WiMAX."
After reading this i started digging around on who is betting on WiMAX and i found an excellent summary:
Mobile wimax equipment which utilize beam-forming and MIMO technologies will become available towards the end of this year. Broadband wireless deployments using pre-802.16e compliant equipment have already begun. In Korea both KT and SK Telecom have implemented mobile broadband wireless networks in specific locations throughout the country.

Sprint/Nextel are deploying an 802.16e compliant mobile wimax network which will reach 100 million Americans by the end of 2008. BT will bid for 2.5GHz RF spectrum in the Ofcom auctions which will take place towards the end of the year 2007. Gaining such spectrum will allow the incumbent to deploy an efficient wimax service and compete with companies such as Vodafone for triple play services. Cable companies are gradually acquiring spectrum and are looking at distributing their content to mobile devices. Greenfield operators are expected to utilize mobile wimax technology in order to secure a 3G/4G market position by attracting consumers with an early new level of service. Clearwire is such a carrier with operations in the United States, Denmark, Belgium, Ireland and in Mexico (via MVSnet).

Equipment manufacturers are becoming increasingly active in mobile wimax. Vendors such as Samsung, Nortel Networks, Alcatel and Nokia-Siemens Networks are all involved in 802.16e projects globally. Motorola have just announced a major deal in Pakistan. Companies that have been heavily involved in operator proprietary broadband wireless implementations such as Alvarion and Proxim are also developing 802.16e compliant platforms. Various chipset providers such as Wavesat, Runcom Technologies and Beceem Communications are developing OFDMA chips and are testing their products for interoperability with solutions from other vendors. Dual mode handsets will be very popular with mobile wimax deployments with GSM/OFDMA and CDMA/OFDMA handsets dominating the market.

But there is confusion. Ericsson believe that by the year 2010 mobile wimax will account for only 5-10% of global broadband wireless revenues and are therefore more focused on broadband cellular technologies. Who is right? Availability of 2.5GHz spectrum is crucial to the success of mobile wimax particularly throughout the western world. In Europe HSPA is dominating the cellular market and this combined with the current unavailability of 2.5GHz spectrum throughout most of the continent is leading to little interest from mobile operators. In the U.S a lot of the 2.5GHz spectrum is owned by Sprint. The carrier will start its deployment by using 10MHz channels to deliver services and could use even larger bandwidths in the future.
Meanwhile in the US, everyone is concentrating on the 700MHz spectrum auction that will be happening soon. The spectrum is in the upper 700 MHz range, not the lower 700 MHz band where companies such as Qualcomm’s MediaFLO already are deploying services. It’s desirable for wireless carriers because at 700 MHz, fewer base stations are required than at higher ranges, making it more economical for buildouts. But numerous other parties also are interested in the spectrum, as evidenced in FCC filings. Everyone from Cyren Call Communications to Frontline Wireless and Google are giving advice on how to use the spectrum.
Among the more neutral players in the cacophony of lobbyists trying to affect the outcome of the auction is Nortel. The company has been sending executives to Washington, D.C., mainly to serve as educators around technologies that could be deployed in the space. Those include OFDM/MIMO and others around WiMAX, as well as evolutions of the GSM and CDMA technologies in long-term evolution (LTE) and ultramobile broadband (UMB), respectively.

“We are keeping a very close eye on where the 700 MHz auction goes,” says Danny Locklear, director of Nortel wireless product marketing. “We see this 700 MHz space as being a very large opportunity for us,” as well as for the overall U.S. market, where it will add more competition and improvements for end-users.

It’s important for companies like Nortel to be involved now, he explains, because typically there is an 18-month cycle from the time standards are developed to the actual product. Delivering products for a new or different band of spectrum is nothing new; vendors know how to do it, but it still takes time, not only in the hardware but software as well.

Discussions over 700 MHz are expected to continue through the coming months, with a final ruling possibly toward the end of the summer and an auction start time anywhere between the third quarter of this year and January of next year. Even then, some of the winners of the spectrum probably won’t be moving in immediately. Analog TV users currently in the spectrum have until the first quarter of 2009 to vacate.

Tuesday 12 June 2007

Will WiMAX compete with 3G+



Various reports and discussions have started trying to compare WiMAX and HSPA/LTE and also justifying why WiMAX is better or vice versa. so will WiMAX compete with 3G+? To answer this problem lets go back to the beginning of 3G.

NTT DoComo launched the worlds first 3G system which it called as FOMA. Infact before FOMA it already had i-Mode available which was a revolutionary technology of its time. So instead of being so great and revolutionary, why was it not adopted by everyone. The answer is that it was a closed technology and not an open standard.

WiMAX is comparatively an open standard. Its Specifications are not available freely as is 3G. This gives 3G a definite advantage over WiMAX. Also 3G+ (which includes HSPA, HSPA+, LTE, MIMO, etc) has evolved from 3G which has in turn evolved from GSM. There is an inbuilt facility to move between 3G/GSM and perform Handovers, etc. This would be missing in WiMAX.

You may argue that once IMS is there, these problems wont be big as IMS would allow these handovers to take place. IMS is access agnostic. The problem is that it will take time for IMS to be adopted and for it to be completely functional. When this happens, by that time LTE would already be available. LTE uses the same Radio Technology as WiMAX and since it has evolved ffrom 3G/GSM, it would definitely be preferrred over WiMAX.

There was an article in Financial Express last week comparing WiMAX and 3G. Some important points from that:

But from what we do know, 3G/HSPA has several clear advantages vis-à-vis mobile WiMAX in terms of backward compatibility, standardisation, use of licensed spectrum and availability of infrastructure and terminals giving it an edge over WiMAX in terms of large scale economies leading to better affordability, availability, scalability and overall ruggedness of the 3G/HSPA standard. Further, the pace of adoption of HSPA has been remarkable. HSPA is already commercially available in Africa, America, Asia, Australia, the European Union and the Middle East. There is thus already a large ecosystem of global suppliers of components, subsystems, equipment and network design and implementation services in place for 3G/HSPA.

WiMAX on the other hand faces a number of challenges. Mobile WiMAX standards are still under evaluation. The capex for deploying WiMAX is upto 5-10 times higher than HSDPA because the size of mobile WiMax cells is upto 16 times smaller than the cells in an HSPA system, which would necessitate a larger number of base stations to cover the same geography.

Further, the prices of mobile WiMAX handsets as and when available, will be significantly higher than the cellular terminals, which are being developed in much higher volumes and offered at increasingly lower costs. Also WiMax has fragmented frequency bands. In Europe and the United States, WiMAX operates in 3.5GHz and 5.8GHz while in Asia Pacific it operates in 2.3, 2.5, 3.33 and 5.8GHz. This makes global or even pan-regional roaming rather difficult. Users visiting different countries will have to either hope that the visited country uses the same band or have their devices equipped with multiple modes to enable connectivity to other WiMAX based broadband networks. WiMAX systems also have a lower capacity for voice vis-à-vis 3G/HSPA networks, which will limit the potential market size that WiMAX can cater to.

Arthur D. Little and Altran Telecoms & Media have also produced a report for GSM Association comparing HSPA and Mobile WiMax for Mobile Broadband Wireless Access (MBWA). According to them:

HSPA is likely to account for the majority of investment in global mobile broadband networks over the next five years, finds a new study by Arthur D. Little. By comparison mobile WiMax will be a niche technology within the overall
global mobile broadband wireless access market, likely to account for at most 15% of this network equipment market and perhaps 10% of mobile broadband wireless subscribers by 2011-2012.

HSDPA (including HSUPA and HSPA+) is taking the lead as it is a natural migration path for a large number of GSM and UMTS operators already operating commercial networks in 3G spectrum. This will give rise to significant economies
of scale on handsets and user devices and a large ecosystem of global suppliers of components, subsystems, equipment and network design and implementation services. Hence this is the least risky and best understood route to offering broadband mobile services which can offer speeds comparable to first generation fixed DSL services.

According to a report in Broadband Wireless Exchange Magazine:

The results of Arthur D. Little's modeling work shows that WiMax systems are expected to achieve significantly greater theoretical peak data transfer rates when deployed than today's commercial HSPA networks deliver now, such as theoretical speeds of e.g. 16.8 Mbps in urban areas vs 2-3 Mbps for HSPA. However, the coverage a WiMax base station can achieve, is substantially lower than HSPA, hence HSPA operators will be able to deploy a smaller number of base stations and sites to cover the same geography. Indications are that radio access network capex for current WiMax technology can significantly exceed HSDPA capex.

Another consequence of this characteristic of these two technologies is that an HSPA operator will be able to match its growing investment more clearly to the development of demand than mobile WiMax operators who will have to install more cell sites at the beginning to ensure coverage.

Arthur D. Little acknowledges that in the longer term, well into the second decade of this century, mobile broadband wireless systems will be characterized by technologies such as OFDMA and MIMO. Development of these technologies is being pursued by the 3G/HSPA ecosystem within the framework of 3G LTE as well as by WiMax. The long term future relative roles of 3G LTE and mobile WiMax, both of which face major development hurdles before they achieve the full promise of new, so-called 4G systems, is uncertain and will be influenced by continuing expected shifts in the priorities and competitive alignments of major players in the wireless industry which has undergone a number of consolidations in recent months.

In contrast to many other reports on HSPA, mobile WiMax and other broadband wireless technologies, the Arthur D. Little study highlights and assesses all the factors - strategic, competitive, commercial, regulatory and political as well as technological that influence operators' choices of wireless network technology.

Evidence for the potential complementary nature of HSPA and WiMax can be seen in the increased interest in multi-mode user devices and roaming capabilities across the technologies. This development, which reflects the widespread anticipation of the central role of OFDMA and other technologies involved in WiMax and 3G LTE in all eventual future broadband wireless networks, is a welcome change from the provocative and misleading headlines that have appeared over the past two years which imply that mobile WiMax threatens the viability of today's HSPA and related technologies

With Intel promising WiMAX chips on all its laptops in future, only time will tell how far WiMAX will and if this comparison holds true.

Wednesday 6 June 2007

IMT Advanced = 4G



In this story on Telecom TV, is says:

Working under a mandate to address "systems beyond 3G", the working party has now come up with a name for the future mobile systems. Thankfully, they are veering away from 4G and are calling it 'IMT-Advanced'.

A simple search on Google returned some useful information from Telecom ABC:

International Mobile Telecommunications - Advanced (IMT-Advanced) is a concept from the ITU for mobile communication systems with capabilities which go further than that of IMT-2000. IMT-Advanced was previously known as “systems beyond IMT-2000”.


It is foreseen that the development of IMT-2000 will reach a limit of around 30 Mbps. In the vision of the ITU, there may be a need for a new wireless access technology to be developed around the year 2010 capable of supporting even higher data rates with high mobility, which could be widely deployed around the year 2015 in some countries. The new capabilities of these IMT-Advanced systems are envisaged to handle a wide range of supported data rates according to economic and service demands in multi-user environments with target peak data rates of up to approximately 100 Mbit/s for high mobility such as mobile access and up to approximately 1 Gbit/s for low mobility such as nomadic/local wireless access.


To support this wide variety of services, it may be necessary for IMT-Advanced to have different radio interfaces and frequency bands for mobile access for highly mobile users and for new nomadic/local area wireless access.


Together with the introduction of the name IMT-Advanced, the ITU introduced the generic root name IMT. The generic root name IMT covers the capabilities of IMT-2000, including future development of IMT-2000, and IMT-Advanced.

Meanwhile a story in ChinaTechNews is suggesting that Datang Telecom has already written a Draft on 4G and is working on 3G&4G convergence. Cannot find much more on this right now.

For more on 4G technologies, either read this story on Network World or 3G4G website.

Monday 28 May 2007

More 4G and WiMax



In a recent article in EE Times, the author is stressing that "Mobile WiMax opportunities will be the next big growth engine for personal broadband and next-generation cell phone networking equipment vendors and for the communications industry in general". A good point raised though is that there are many people who have comitted to WiMax:



In US, global communications carriers like Sprint have announced plans to deploy large-scale mobile WiMax services by mid-2008. In some cases, entire countries have committed to WiMax as their fourth-generation standard of choice. Two such examples are Korea, with the early WiBro predecessor to mobile WiMax, and Taiwan, with the "M-Taiwan" national initiative.

What other thing the author is trying to stress is that WiMax is 4G but i do not agree.

Sony Ericsson is another high profile name that recently announced joining of WiMax forum. According to MacNN, no hardware updates or new products have been announced, but it's likely that Sony-Ericsson will begin to upgrade their products to take advantage of faster speeds.

According to another article in ARN today:

Unlike 3G, no specific standards spell out what a 4G service, network or technology is today. Analysts say these specifications are to come, but today "4G is more of a marketing idea," says Phil Redman, a research vice president at Gartner.

There is a mobile WiMAX standard -- the IEEE's 802.16e standard -- on which Sprint Nextel is basing its US$3 billion investment. But Redman says mobile WiMAX is not 4G, "although the WiMAX folks would love for that label to catch on."
Still, WiMAX and other technologies may be part of a forthcoming 4G specification. "There's no doubt that existing technologies like WiMax and other technologies such as [Orthogonal Frequency Division Multiple Access] and [multiple input multiple output] will be included in 4G," Redman says. "But no one technology will be 4G."

"These things tend to run in 10-year cycles," Redman says. "2G came out in 1995, 3G in 2004. There will not be a 4G standard before 2015."
In the meantime, a number of players have attempted to spell out what 4G should look like. The World Wireless Research Forum (WWRF) says 4G will run over an IP infrastructure, interoperate with Wi-Fi and WiMAX, and support fast speeds from 100Mbps to as high as 1Gbps.

It's also key that next-generation wireless includes QoS metrics and the ability to prioritize traffic, says Lisa Pierce, a vice president at consulting firm Forrester Research. "Lack of prioritization is preventing businesses from using current EV-DO services as their primary data connection."

WWRF expects 4G will be a collection of technologies and protocols, not just one single standard. That's similar to 3G, which today includes many technologies such as GSM and CDMA that meet specific criteria.

To help move the standards process along, WWRE -- whose members include Ericsson, Huawei Technologies and Motorola -- contributes to standards work done within groups such as the International Telecommunications Union (ITU), the group that defined 3G wireless specifications, and the IETF.

4G's predecessor, 3G wireless, is still taking off. The fourth-largest wireless-service provider, T-Mobile,launched its 3G network this year. So if 3G is just getting going, what does that mean for 4G?

Opinions on when 4G services might be available differ. The Next Generation Mobile Networks (NGMN) group says commercial services beyond 3G could launch as early as 2010. KPN Mobile, Orange, Sprint, T-Mobile International, Vodafone, China Mobile and NTT DoCoMo make up NGMN. The goal of the group, similar to the WWRF, is to work with standards bodies in developing next-generation specifications.

But if standards don't come before 2015, as Gartner's Redman predicts, true 4G services could come only after 2015.

Thursday 24 May 2007

Almost 300,000 LTE Base Transceiver Stations by 2014

Nearly 300,000 LTE Base Transceiver Stations will be installed by 2014, according to a new study from ABI Research. While LTE will encounter competition from other mobile broadband technologies, its supporters extol its potential to unify the mobile infrastructure market.

LTE brings to the market 25 years of operating experience using TDM and CDMA technology. It aims to use that, combined with OFDM, and other techniques, to provide the best of both worlds, perhaps stealing WiMAX’s thunder. This also takes the industry from the current two-network approach of circuit switching for voice, and packet switching for data to a single IP network for both services.





“LTE faces competition from other broadband wireless technologies and it will need to demonstrate clear technical and economic advantages to convince network operators,” says ABI Research analyst Ian Cox. “The mobile variant of WiMAX will start to appear in 2007 as the WiMAX Forum Certification program ramps up. The industry is also working on HSPA+, which could offer the same performance in a 5 MHz bandwidth. Without additional spectrum, operators could face a difficult choice.”
Cox further comments that, “LTE is the NGN for the mobile industry and is being standardized by 3GPP with the full support of operators via the NGMN Group.”

Long Term Evolution (LTE) of 3G technologies is about to benefit from Release-8 of the 3GPP standard, planned for the third quarter of 2007. The potential rewards of LTE are simplicity of operation, a “flat” architecture offering low latency, and spectrum flexibility. Backwards compatibility and roaming with 2G and 3G networks are added bonuses, along with lower power consumption and improved performance, . LTE could also unite the W-CDMA and CDMA communities because of its spectral flexibility.

For vendors, LTE will allow development of a new market to replace declining 3G revenues.

For users, says Cox, LTE will enable broadband services, including VoIP, to be offered over SIP-enabled networks. Each service will be IP-based, offering high data rates and low latency, with on-line gaming becoming a reality along with mobile network data speeds comparable to those of fixed networks.

“UMTS Long Term Evolution”
(http://www.abiresearch.com/products/market_research/UMTS_Long_Term_Evolution) reviews the world market for LTE.