Electronic Design

Broadband Wireless World

Las Vegas, NevadaApril 26-28, 2006

I love these focused shows. Several hundred attendees and about 70 to 80 exhibitors. A good size to get some critical mass in the field, yet small enough that you can get around to many of the sessions and visit most of the exhibits. But like most shows, these are pure information overload. Lots of great new things to learn and think about all crammed into a few days.

This show—Broadband Wireless World—zeros in on the broadband wireless access (BWA) field. If you are not familiar with it, you may want to know that it grew out of military and telecom microwave technologies where point-to-point back haul was dominant. Today it has evolved into a whole new business, that of wireless networking for a variety of high-speed data applications. The two hot topics at the show were WiMAX and Wi-Fi Mesh.

WiMAX is the relatively new wireless technology designed to provide point-to-point (P2P) back haul or last mile point-to-multipoint (PMP) Internet connectivity. The technology has been around a few years and the formal standard IEEE 802.16d (also known as 802.16-2004) was ratified in 2004. This is a standard designed to work in the 2- to 6- GHz bands using 256 OFDM and an adaptable modulation (64QAM, 16 QAM, QPSK, BPSK) scheme to adjust to local conditions.

The original 802.16a standard was strictly a line-of-sight (LOS) service that needed outdoor antennas and could not deal with non-LOS conditions and the multipath problems that plague this frequency range. 802.16d does this well even with an indoor antenna. It provides a data rate up to 75 Mbits/s and a range extending to 30 miles under ideal conditions, although most links will only be a few miles at most. In a PMP system, subscribers will get at least 1 Mbit/s service, but operators will charge by bandwidth as usual to consumers or business customers.

WiMAX is going through the normal cycle of development common to most wireless technologies. First comes the standards, then the alliance of manufacturers, in this case the WiMAX Forum, that promotes the technology. The alliance also sets up the testing and certification for interoperability. Next comes the silicon followed by some real end products. Finally, services are established and the business grows.

Some have criticized WiMAX for not moving faster, but that usually comes from those who have never lived through the process. Look at Bluetooth. Everyone said it was DOA because it took so long to emerge. But that is normal. Today Bluetooth is the volume leader with hundreds of millions of chips and products shipped annually. While WiMAX will never be that prolific, it will find its place.

I saw great progress with WiMAX this year. There are more new chips, new equipment, and services being established. Fujitsu introduced its baseband chip last year at this conference. This year Fujitsu presented its new partners who have been developing systems using the Fujitsu WiMAX SoC chip. This includes Air Broadband, who introduced its PiMAX subscriber and baseband stations for broadband metro networks. Aperto Networks presented its Packet MAX 5000 basestation. Hopling Technologies showed its HopMAX 1600 subscriber station and some micro-basestations. MITAC and Orza also use the Fujitsu chip in their subscriber stations.

A relatively new chip company called TeleSIS Wireless introduced its TWC 1620, an 802.16-2004 baseband SoC. President and CEO Sam Endy said the chip is a good fit for both fixed and portable systems. VP of Product Management and Marketing, David Sumi, pointed out that their chip had what may be the lowest power consumption of the current batch of baseband SoC chips available. With several watts being the norm for the first round of chips, the TeleSIS chip only consumes up to 750 mW. This is going to be a real necessity for portable and mobile devices.

Another chip vendor is Wavesat of Quebec. Its Evolutive WiMAX DM256 chip set includes both the physical layer (PHY) RF and the baseband functions. Other RF chip vendors at the show were Sierra Monolithics and Texas Instruments.

Equipment companies like Alverion, Aperto, Proxim, and others showed their latest base station and CPE products. Other older BWA companies are beginning to build their own new WiMAX products. Most say that initially, back haul is the big draw because of the low cost, but eventually, wireless Internet service suppliers (WISPs) will emerge with PMP services for consumers and small businesses. These services will compete with local cable TV and DSL carriers.

WiMAX will also provide wireless broadband to smaller towns and rural areas who are still without broadband service. These under-served areas will be the first to see BWA with WiMAX. And it’s a real boon to developing countries where wireless, or even wired services, are rare. Because WiMAX can easily deliver IPTV as well as VoIP services, it should fill a niche where voice and video services are not available.

There are two critical areas developing in WiMAX. First is the emergence of the mobile version of WiMAX. The standard 802.16e was ratified last year, but there are no products or services available. Chip makers are grinding away at suitable designs, but the rest of the industry is trying to figure out what to do with this version.

Standard 802.16d WiMAX is a fixed service. It can also accommodate so-called nomadic services where WiMAX-enabled laptops with PC cards or internal chips can move from one fixed point to another and maintain connections in an area covered by multiple base stations. Portable and mobile operation is not a good option for this version.

Portable operation means slow movement (walking) of a subscriber station. Mobile means the subscriber is in a moving car, bus, train, or whatever. It assumes handoffs between base stations and all the other features we have come to take for granted in our cell phones. The new 16e chips will provide for handoffs and be able to handle the constantly changing multipath and Doppler problems.

We may see some of these chips later this year, and will see them next year for sure. Such mobile WiMAX will surely compete with 3G cell phone data services. I think we will have to wait and see how this plays out. Incidentally, 16d and 16e are not compatible with one another. No doubt the goal of every chip maker will be to get WiMAX into every laptop just like Wi-Fi is today.

Perhaps the most critical WiMAX issue, at least in the U.S., is the availability of spectrum. Most speakers referred to this problem in some way. Spectrum is tight for almost every country, but the U.S. is hurting. The bands targeted for U.S. WiMAX are 2.5 and 5.8 GHz.

The 2.5-GHz band is probably the best because it is a licensed band so interference from other services will be non-existent. The bad news is that this spectrum is in the hands of only a few companies, amongst them Sprint Nextel and Clearwire. Will these companies decide to create WiMAX services or sell/lease their spectrum to others? Sprint Nextel is still undergoing the pain of their recent merger and dealing with the upgrade of their cdma networks to 3G level. I doubt they will act soon on the WiMAX opportunity. Who knows about Clearwire. Some one may be able to scrounge out a few bands to implement WiMAX.

The most popular WiMAX band is 3.5 GHz, which is not available in the U.S. However, that is where most of the action is in the rest of the world and that is where over 80% of the products are going today.

The 5.8-GHz band is unlicensed spectrum that anyone can and does use. It is used by educational institutions and of course cordless phones and 802.11a Wi-Fi. Besides the potential interference problems, range is more limited at these frequencies meaning more transmit power and more base stations. But it is a band that will get used. It just remains to see how.

WiMAX is definitely on track despite what some critics will say. It is more of a niche technology, but one that fits many possible needs. That is the great thing about wireless, there is something for everyone.

Wi-Fi Mesh
One hot topic at the show that I did not anticipate was meshed Wi-Fi access points to provide widespread coverage. By meshing Wi-Fi, the coverage can be extended from a single hot spot coverage area to a big enterprise facility or a whole city. Lots of cities are implementing and installing these so-called municipal or muni-Wi-Fi meshes. Philadelphia, San Francisco, Anaheim, Mountain View, Milpitas, Tucson, St. Cloud, Florida, and Alexandria, Virginia to name a few.

By bolting a complete base station to light poles like the old Riccochet system, height and power are provided. These access points (APs) talk to one another and in standard mesh form they serve not only as APs but also as repeaters for nearby APs. And the really good news is that only one of the APs in the system needs a fast wired connection to the ISP.

Mesh is a great technique for greatly extending the range of any wireless system. The connection is maintained if one AP goes down or if the user hits a dead zone since multiple alternate paths through the system exist. And better still, Wi-Fi is cheap. Entire muni areas can be covered with minimum cost. Some small cities have meshed their main localities for only tens of thousands of dollars.

Small cities are building the meshes to provide Internet connectivity to mobile citizens and less privileged citizens without a high-speed connection. But they are also using it for a wide variety of public works (water and other utilities) and public safety (police, fire, etc.) applications.

There has been some fussing by the local cable TV and DSL providers that cities are taking business away. I suspect that they really are not as the mesh system is more for the portable/mobile crowd. One of the speakers estimated that there were roughly 300 of these muni-meshes now operational in the US.

In any case, mesh is definitely hot. A number of companies are jumping in with their own software to mesh standard Wi-Fi hardware. It is reasonably fast and easy to do. And in many ways it competes with potential future WiMAX apps. With WiMAX not fully there yet, it is no wonder that cities are taking advantage of this affordable technology. Look for this mesh trend to roll out fast over the next year or so. It won’t kill WiMAX and in fact, WiMAX may end up being the technology to mesh the various hot spots.

Is there a mesh standard? The early 802.11 standard provides for it but no one has ever taken advantage of it. A broader, more formal mesh standard 802.11s is working its way through the IEEE process now. Some will adopt it, but most may not. Every mesh system I looked at was proprietary. Once 802.11s is ratified (next year), it may be a factor, but right now, the non-standard systems are doing just fine, thank you.

Less we forget the lowly antenna, any wireless device is only as good as its antenna. There were a batch of antenna companies at the show. The trend these days is to package the antenna so your home or business doesn’t look like the roof of the local ham or the top of an NSA listening post. Yagis and colinears are housed in cylindrical plastic tubing so are much less offensive. Patch antennas and some arrays are contained in unobtrusive flat panels. Most are boring looking and essentially not noticeable. Who would care?

But for the really paranoid, you can get a housing that has been covered with an actual photo of the portion of the building where it will be mounted. Real stealth. Stealth is a big issue these days with home owners and businesses fussing about the proliferation of antennas and cell towers everywhere. It is okay to still build them, but not in my back yard. Cell phone companies have become masters at hiding towers or using camo techniques to put the antennas where they are needed. WiMAX will face the same problem.

One Final Word
When I speak to BWA companies, I am always amazed at how much proprietary wireless technology is still out there. With so many different technologies and approaches available, it was once said that lack of a standard was holding this field back. Now that we have some standards, the proprietary approaches still exist. I guess the applications are such that widespread interoperability is just not an issue.

Two of the biggest proprietary systems are Motorala’s Canopy broadband mesh and Proxim’s AP-4000MR-LR. The condition will continue to exist as most proprietary systems are hardened and far more rugged and reliable than, say, a Wi-Fi mesh. When a system must really provide the QoS demanded by the government or a large company, the more robust system will win out, proprietary or not. When we begin to get VoIP over WLAN and IPTV, we will see just how good mesh Wi-Fi really is.

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