As Mobile Video and other bandwidth-hungry mobile applications dominate the wireless communications infrastructure, wireless backhaul — the transfer of traffic from a wireless base station back to the core network (and ultimately the Internet) — become critical. In the past, T1s and E1s were used to do this, but increasing bandwidth demands encourage the deployment of fiber, which can be expensive. The latest approach is to use point-to-point wireless backhaul technologies, or a combination of wireless and fiber. In this six-part series, we take a look at what’s happening with wireless backhaul today.

 

The next player we shall examine is Exalt (News - Alert) Communications (www.exaltcom.com) an innovative provider of next-generation wireless backhaul systems for service providers and enterprises worldwide. Exalt solutions address the network bottlenecks associated with the growing demand for IP-based voice, data and video applications and the resulting migration from TDM to IP-based networks. Having designed a flexible architecture and technology-agnostic product platform covering multiple market segments, Exalt has managed to provide a full-range of carrier-class wireless backhaul solutions for any access technology or campus connectivity as a cost-effective and flexible alternative to fiber and leased lines.

 

Exalt Communication’s CEO Amir Zoufonoun, says, “I’ve been in this business for 28 years. Until I started Exalt, I had always focused on microwave radio development. I spent about 10 years at Harris Corporation and then about 12 years at Western Multiplex, where we were very much concentrating on licensed free-band. The advantage of that for myself and the team I worked with was that we had these free-bands in which to innovate. That’s a key point concerning how Exalt came into being. We created a class of radios that were carrier-class in licensed free-bands and we sold them to carriers and enterprises all over the world over a 10-year or 12-year period. We tested many technologies during those years. It turns out that a lot of those things are now very much relevant to what’s going on in the mobile networks as they expand and shift towards IP and they add more capacity.”

 

“In the 2004 timeframe I started up Exalt Communications because I wanted to take advantage of this opportunity that I saw in the markets,” says Zoufonoun. “I saw a huge shift occurring that I had never seen in the previous two decades or so. All of a sudden, T1s and E1s were going to be a thing of the past, and people were going to shift towards using Ethernet and IP. At the same time, operators were talking about how they would need 10, 100 or even 200 times the bandwidth capacity that they presently had at their cell site, which is a completely new situation. In the past, increases in bandwidth demand caused by increasing numbers of users and applications had been handled by incrementally adding a copper T1 here and there as they need arose. But now operators were talking about several hundred more megabits per second at the cell sites. Additionally, it became evident that TDM was going to be around for a long time, because you have all the 1G, 2G, 2.5G, and some 3G networks that have T1 or E1-based backhaul. The operators are not going to throw those away immediately. There about two billion phones that are on those networks and operators are adding the newer 3G and 4G base stations that are Ethernet-based, but they will be layered. It also means that you’ll have multiple access technologies carried over what’s effectively one conduit on the backhaul end of the network.”

 

“The other thing related to all of this is that is that copper T1s and E1s easily max out, and many cell sites use these,” says Zoufonoun. “So you can only add a few T1s and E1s, up to a maximum of 10, and then beyond that the question becomes whether the operator runs their own fiber or do they resort to microwave links. All of this became an opportunity for Exalt on which to capitalize. We formed the company in 2004. We brought our products to market in early 2006, so we’ve now had two years of revenue behind us. We’ve been ramping up selling to carriers and enterprises. Fortunately, the market itself went in exactly the direction we had predicted in 2004. At that time, most experts told us that we’d be crazy to start another company in this field. They thought the market was saturated with many vendors. But now the situation is quite the opposite. In fact, if anything, the market is very much underserved and needs new vendors to come in and supply innovative, high capacity, software-defined radios for next-gen backhaul.”

 

“When it comes to backhaul using microwave frequencies, we’re talking from about 2 gigahertz to about 40 gigahertz,” says Zoufonoun. “That’s the basic range in which much activity occurs. There are a few bands above that, in the 60, 70 and 80 gigahertz range as well, but not so much. Those products are not mainstream. They’re at the edges. But the 2 to 40 gigahertz band accommodates many microwave radios from various vendors over the years. However, those products are mostly TDM-based, and of course people are trying to shift to IP and Ethernet. The bands are 2, 5 and 6 gigahertz, and then 10, 11, 15, 18, 23 and so forth. Those are the bands used for backhaul. It depends on what is available in your geographic area. If you can a license to operate in a particular band, then that’s the band you must use. As you go up in frequency, the reliable transmission distances become shorter. There are physical limitations – for example, above 15 gigahertz you encounter ‘rain fading’ that occurs with radios. In other words, the signal level goes down depending on the amount of rainfall in the region. So an operator must be mindful of that and engineer your links accordingly. For instance, if you’re in South Florida, it’s quite different than being in northern California. Rainfall statistics are quite different and therefore the length of a link can be affected, as well as the size of the antenna needed. So the choice of what band to use is a multi-valued function. You must pay attention to many parameters when choosing a particular band in addition to simply having it available.”

 

“That’s why we at Exalt Communications decided from Day One that we’re would be agnostic in terms of bands,” says Zoufonoun. “We would support all of the different low frequency bands, both in licensed and license-free, as well as the higher-frequency bands. When you’re putting a network together, you really need to have access to multiple bands in order to create a large network. In the past, microwave was basically an afterthought or a ‘last resort’ kind of solution, since you had copper and fiber. You could easily obtain a T1 in many places in the U.S. and individual cell site coverage was pretty big, such as 5, 10 and 15-mile radii. Now, with the advent of new access technologies, the physics dictate that cell sites must be much more confined to a smaller geography. That means that you will more base stations, and at these base stations you must bring in very high bandwidth connections, and fiber by definition is not available in many of these situations, so microwave is the choice. And in order to resort to microwave, you need access to bands that bring that kind of high bandwidth into that particular region and provide the necessary capacity.”

 

“At Exalt, we don’t really care about particular band technologies,” says Zoufonoun. “All bands are good bands for us, be they license-free or licensed, low-frequency or high frequency. We have a single platform that works with all of these frequency bands, and it’s all software-defined. Microwave for backhaul is now moving to the front burner. It’s not an afterthought anymore. Because of the shortage of fiber at many locations, or the paucity of available leased lines, microwave is becoming mainstream and indeed the number one choice for many carriers needing a backhaul solution. Outside of the U.S., microwave has been the norm in places such as Western Europe, where 70 to 80 percent of cell sites are backhauled by microwave. No news there, but the Europeans do need to rip out all of the old equipment and install new generation microwave equipment because they are faced with the same dynamics as bandwidth requirements increase with the introduction of 3G and 4G. Bandwidths are multiplying by about 100 fold so that creates a tremendous bottleneck in backhaul network so they need new microwave technology. But outside of Western Europe, it’s been a mix. In the U.S., about 20 percent of installations traditionally have been microwave, with 80 percent being fiber and leased lines. And now, that ratio is going to shift. We’ll see more and more microwave being used because of the dynamics that I’ve previously described.”

 

“Microwave for backhaul is becoming more popular,” says Zoufonoun, “and at the same time microwave follows something very similar to Moore’s Law. You see more functionality and less cost every year. This continues because it is, after all, digital electronics that dominates what the cost happens to be. In the case of fiber, however, you still have to dig up the ground. Those costs have reached an asymptote and they aren’t decreasing any more. It can cost you at least couple hundred thousand dollars to dig up the ground and create a link to a base station, even for relatively short distances. With microwave technology, however, for $10,000 or $20,000 you can create a link, and by the way, you can do it instantly – same day installation. You can turn on your services immediately, unlike fiber, where you have a wait time because of zoning and other issues. With microwave, you can pay back that $10,000 or $20,000 in a few weeks, because now you’re talking about moving multi-hundred megabit per second conduits, compared to leased lines. The payback period is thus very fast. It’s a no-brainer.”

 

“Within a five-mile radius of a downtown metropolitan area,” says Zoufonoun, “you typically have a lot of fiber available. As you move beyond this radius, there is mix of fiber and other technologies, mostly microwave. In rural areas, of course, it almost always must be microwave. It just doesn’t make sense to put a lot of fiber into the ground, because the user density is just not there. Interestingly, in the middle-mile section, where you have a mix of fiber and copper and microwave, there’s now a shift occurring from copper and fiber toward microwave usage. The reason is that the cells coverage areas are splitting. In the past you had a five or ten mile radius covered by a single base station in the middle-mile section of the network. Now, however, because of the users and the higher bandwidth access technologies and applications, coverage has shrunk down to about a mile radius around each base station. That dictates that you look for some alternative to bring that greater capacity to ten new cell sites instead of just one. So you have to use microwave to achieve this. There really is no other way to do it.”