Alpha Omega Wireless Blog

If you thought wireless interference among unlicensed wireless Ethernet bridge systems is bad now, just wait. What's going to cause this flood of wireless interference is the introduction of 802.11n based, OFDM and MIMO, outdoor wireless backhaul systems. Add to the mix the amount of wireless backhaul being deployed in the IP video surveillance industry.

Now with the acceptance of 802.11n chipsets there has been a mad rush by the outdoor wireless manufacturers to introduce higher bandwidth point to point wireless backhaul, point to multipoint wireless bridges, and wireless mesh systems. Why not? It's pretty amazing that you can now buy an unlicensed wireless Ethernet bridge system that can provide up to 300Mbps of aggregate throughput for under $5,000.00

So what's the issue? In my article "Wireless Interference - The Effect on Unlicensed Wireless Backhaul" we discussed how wireless interference on unlicensed wireless Ethernet bridge systems has continued to grow. The new 802.11n based wireless backhaul radios use OFDM and MIMO taking advantage of multipath, especially helpful in nlos (non line of sight) applications. They also produce a lot of multipath! They also need to use a wider channel width to obtain a higher data rate, up to 40MHz wide. Because these systems, according to manufacture specifications and marketing, can produce high aggregate throughput at an attractive price many people that didn't use outdoor wireless bridge systems are now starting to.

As more and more people get tempted with the thought of 100Mbps, up to 300Mbps providing an extremely fast ROI compared to a leased telco line, more and more unlicensed wireless backhaul will be deployed. The one thing that that people don't understand is that to get the full throughput the system must run at full modulation and channel width with limited wireless interference. This is something that the manufactures forget to mention. Because people are not controlling their RF signals by deploying so called plug and play outdoor wireless bridge systems and using wide beam antennas at full transmit power the amount of interference is going to explode.

Add into the mix the amount of wireless backhaul for video surveillance. Wireless video backhaul is a huge topic and growing industry. Each year at the popular industry trade event, CTIA, there is a growing number of manufactures displaying their unlicensed wireless video backhaul systems. Using wireless backhaul for video is a great application. But with the large number of unlicensed wireless Ethernet bridges being deployed and the amount that is done improperly the amount of wireless interference is bound to grow.

Should you consider an unlicensed wireless Ethernet bridge, using OFDM and MIMO? These types of outdoor wireless Ethernet bridges provide a great inexpensive solution. They work extremely well on challenging near-line-of-sight and non-line-of-sight applications. They also provide a great amount of throughput at a great price. If you need a true enterprise point to point wireless bridge and have line-of-sight (LOS) there is no substitution to a licensed microwave link, see "Licensed Microwave Wireless Backhaul."

The one thing to keep in mind is prior to considering an unlicensed wireless Ethernet bridge for microwave communication a wireless site survey, spectrum analysis, and a proper wireless path calculations should be performed. As with any point to point wireless backhaul, point to multipoint, or wireless mesh system a certified expert should perform the wireless installation.

Service providers have adopted WiMax backhaul as a technology that they could readily deploy cost effectively to provide the last mile fixed wireless connectivity with greater bandwidth. It wasn't until later that WiMax backhaul evolved to the mobile carrier space. WiMax currently is a competing 4G technology to LTE (note: see article "WiMax Outdoor Wireless Bridges versus LTE Wireless Networks" for more detial). There are a lot of articles on whether WiMax and LTE truly compete or will end up being complimentary technologies providing different service benefits. The one issue with WiMax is because of the higher frequency bands it does not do well with penetrating obstructions like passing through walls of a building providing coverage indoors. The use of OFDM and MIMO do allow for (NLOS) non-line-of-sight wireless connectivity outdoors.

WiMax backhaul does not compete with the Wi-Fi standards, nor does it replace it. There will continue to be the need for Wi-Fi indoors and around campus environments to provide network connectivity to the LAN. WiMax backhaul will allow mobile device to get high speed internet from the carrier service provider companies that the devices are associated with (such as AT&T, Verizon, T-Mobile, Sprint, etc.).

The bottom line is WiMax backhaul is truly for service providers and mobile carriers. WiMax is not a solution for an end-user. The technologies used by WiMax have already been used for years now (e.g. OFDM and MIMO). WiMax is not a licensed microwave wireless solution that will completely avoid wireless interference. Nor will WiMax backhaul replace point to point wireless backhaul, licensed microwave links or unlicensed wireless Ethernet bridges. Because of the small channel width available currently, WiMax doesn't bring any higher bandwidth for an end user application. The WiMax 2 initiative takes more advantage of the use of MIMO and will provide more bandwidth, like wireless Ethernet bridges that use 802.11n chipsets today.

Today there are many systems that can produce higher wireless backhaul bandwidth by using standard unlicensed wireless Ethernet bridges compared to using WiMax as a wireless backhaul solution. Many manufactures have cashed in on the WiMax standard and have over sold its capabilities and what it's for to the end user market place.

If you are not a mobile carrier or a service provider (WISP), WiMax backhaul does not provide you any advantages over other outdoor wireless Ethernet bridge systems that have been deployed for many years now. To register WiMax is pretty difficult in many areas because many WISP and mobile carriers already have taken the spectrum. Note: see image below showing the areas already registered by service providers and mobile carriers in the Sacramento and San Francisco, CA area.

Is WiMax good for you? As a mobile user it will provide us great wireless backhaul throughput to our mobile devices. For end users that need another internet provider solution, especially in areas where they can't get DSL, WiMax will allow service providers to provide a high quality wireless Ethernet bridge to areas that were either technically difficult or too costly to provide connectivity to. But for Government, Enterprise, or Private networks it does nothing!

Many customers come to us and say that they need a wireless backhaul solution, but say they are waiting for WiMax. We ask, "Why?"

Many people that are not part of (or don't closely follow) the wireless backhaul, point to point wireless bridges or point to multipoint wireless backhaul, industry or the 4G mobile (LTE and WiMax) carrier industry really don't understand what WiMax is all about. Some think it's a Wi-Fi replacement. Others think it's a new technology that is going to replace all outdoor wireless backhaul, like licensed microwave links or wireless mesh networks. There is a lot of talk about the standards-based technology of WiMax backhaul. Many people do not know what WiMax is or what WiMax is not.

The term WiMax has become a marketing machine and has pushed the outdoor wireless backhaul industry into one the fastest growing technology industries. Just as the term Wi-Fi has been trademarked to the indoor wireless LAN market, WiMax is a trademarked term for a standards-based point to multipoint technology for the outdoor wireless backhaul market. WiMax in itself is not encompassing of all outdoor wireless backhaul. Note: image below is reported by the WiMax Forum as of Feb, 2010.

A General Background:
WiMax backhaul was originally designed to be a point to multipoint wireless backhaul solution for providing last mile wireless Ethernet bridges, as alternative to DSL to the home and T1 replacement to businesses. A point to multipoint wireless system consists of a base station unit ("BSU") or sometimes called an Access Point ("AP"), as a standalone or part of a cluster to provide multiple sectors of wireless backhaul coverage that provides wireless backhaul to multiple Subscriber Units ("SU"). SU's are sometimes called CPE's (customer premise equipment). This was for the WISP and telecommunication provider markets.

Part of the equation was also to make mobile devices (like laptops and mobile phones) equipped with WiMax 802.16 chipsets so they could become an actual subscriber unit, creating direct internet access through the service provider (like a giant outdoor hot spot). This would basically provide a direct wireless Ethernet bridge connection directly to a WiMax point to multipoint wireless base station array. Like a mobile phone connecting to a cellular tower.

Manufactures of outdoor wireless bridges and the WISP market realized that wireless interference is a huge issue with outdoor Ethernet wireless bridges. When you start using unlicensed wireless bridges to be a point to point wireless backhaul to unlicensed point to multipoint wireless bridges, which then provide backhaul for Wi-Fi access, in unlicensed 2.4GHz (802.11b/g/n) and 5.8GHz (802.11a/n), there is a large risk of wireless interference. At the same time many people have tried to extend Wi-Fi to outdoor environments to provide greater wireless connectivity to mobile devices, but this still needs a backhaul at some point.

WiMax backhaul was originally going to be in a frequency band away from the popular 5GHz band (5.3GHz, 5.4GHz, and 5.8GHz) used for most unlicensed wireless bridges. Unfortunately, the FCC did not allow for this. Later the FCC did open up a small piece of spectrum, 50MHz wide, of the 3.65GHz band to be used by WiMax backhaul radios. The 3.65GHz band is non-exclusive, meaning it's not a licensed microwave bridge requirement, but just a lightly regulated space that requires service providers to register the microwave wireless broadcast. The 3.5GHz band is used for WiMax backhaul wireless radios in other countries. Some mobile carriers have manufactured their own radios to operate in their licensed 2.5GHz frequencies.

For a piece of wireless backhaul equipment to be considered WiMax Certified (by the WiMax Forum^TM) it must comply with the 802.16 IEEE standards and be completely interoperable with other manufactures WiMax equipment. The problem is that there are not many devices that are truly interoperable or have been fully tested to work with one another. It's funny how many of the WiMax 802.16 standards, like OFDM, were already found in the existing product lines or outdoor wireless Ethernet bridge manufactures like Proxim, Alvarion, Motorola, and others. Most WiMax equipment is almost no different than current point to multipoint wireless systems operating in the 2.4GHz or 5.8GHz unlicensed wireless bridge frequency bands. Most use OFDM and MIMO technologies. WiMax backhaul just operates in a different 3.65GHz wireless band, which provides a smaller channel width and less data throughput.

More to come in Part 2...

An experienced IT Director once told me, "The question is not if your fiber backhaul will go down, but when will it go down." This was on a day where he experienced his fiber being cut due to some construction workers trenching up the conduit that his fiber was in during a road repair project. This happens more often than you think. Why do you think most SLA'a by a telecommunications companies are only 99.9% uptime.  

Ever question how long it takes for a telecommunications company to do a truck roll to repair a cut fiber? If it's a clean break fiber can sometimes be fusion spliced back together. In most cases where a fiber pole goes down or gets ripped out by a backhoe, the fiber gets stretch and has to be replace but cutting it at two ends and a new piece fusion spliced back in. This can take hours if not days to accomplish. What would be the cost to your business if that occurred?

This picture shows a local telecommunications companies main fiber line providing the main backhaul for a city government laying on the ground after a pole fell over. It has been like this for weeks. 

Most people don't think about the fiber once it leaves their building or know the path it takes. Most long haul fiber in established urban areas runs inside sewer lines. In rural areas fiber mostly runs along telephone poles. Ever drive down a road and see a bunch of wood telephone poles leaning from side to side? Well that might just be the fiber your network is running on.

Now let's talk about microwave communication using a point to point wireless bridge. A fixed wireless microwave link can go distances up to 50+ miles and provide data rates of 10Mbps full duplex to GigE Full Duplex (gigabit wireless). If proper wireless system design is done, a fixed wireless Ethernet bridge can provide a predictable reliability of 99.999% uptime. That's less than 5 minutes of predictable outage a year.

Microwave communication can be in the form of a point to point wireless backhaul, a point to multipoint wireless bridge system, or a mesh wireless Ethernet bridge. If a microwave radio fails it can be swapped out in the matter of minutes (provided a spare is maintained). After an earthquake or other natural disaster, a wireless system can be realigned immediately getting communications back up and running. Wireless backhaul was used after Hurricane Katrina for months before the telecommunication companies could get their fiber repaired. The biggest concern with wireless backhaul is the potential for wireless interference. Using a licensed microwave link can solve any interference concerns.

Customers that have experienced a good wireless installation typically use their point to point wireless backhaul as their primary connection and downgrade their leased telco circuit (saving them reoccurring costs) as a secondary. A wireless link also puts control back into the hands of the owner rather than relying on a telco. You can't fixed a down telephone pole because a tree branch fell on it, but you can swap out a wireless Ethernet bridge radio easily.

The one thing that most people don't understand is the industry background between WiMax backhaul and LTE wireless networks.

WiMax backhaul was originally developed by outdoor wireless backhaul manufactures as a way to provide fixed last mile outdoor wireless bridge connectivity. These were wireless Ethernet bridge players like Alvarion and Proxim (funny how many of the WiMax 802.16 standards, like OFDM, were already found in their existing product lines). Other players like Intel, who has a big stake in IP based technologies, joined the forum. The early intent, of those pushing the WiMax 802.16 standard, was to get the FCC to open up the 3.5GHz space for point to multipoint wireless backhaul. This was to serve the WISP (Wireless Internet Service Provider) market place. Part of the equation was to make mobile devices (like laptops and mobile phones) equipped with WiMax chipsets so they could become an actual subscriber unit (a CPE device) and connect directly to a WiMax point to multipoint wireless base station array.

The one major issue many manufactures of point to multipoint wireless bridges were facing was that they were also providing point to point wireless backhaul in the unlicensed wireless backhaul space and providing outdoor Wi-Fi solutions. Wireless interference is becoming a huge issue in the outdoor Ethernet wireless bridge space when you start using unlicensed wireless bridges (like 5.8GHz wireless backhaul) to serve unlicensed point to multipoint wireless bridges, which then provide Wi-Fi access in unlicensed 2.4GHz (802.11b/g/n) and 5.8GHz (802.11a/n). WiMax equipment if offered in a separate frequency band like 3.5GHz would open up a lot of outdoor wireless backhaul spectrum.

It wasn't until later that WiMax backhaul evolved to the mobile carrier space. Carriers, both fixed wireless and mobile, have adopted WiMax as a technology that they could readily deploy cost effectively to provide the last mile connectivity with greater bandwidth. The other advantage of WiMax backhaul is that IT people (that understand IP networking) can easily take part in outdoor wireless backhaul network deployments because they understand the IP networking background required for WiMax backhaul networks.

LTE was the evolution of the carrier's TDM transport to gain broadband to mobile devices. Many carriers like LTE because it's just an evolved technology of what they are already using. LTE is a natural progression from 2G / 3G and allows fall back. When a mobile device roams out of quality signal strength of an LTE (4G) network it can easily fall back to 3G or lower speed connectivity. Another advantage of LTE over WiMax is that LTE offers less wireless backhaul latency. WiMax backhaul uses a bigger overhead in packets. Many of its supporters are the manufactures that have been part of the mobile market all along.

WiMax backhaul has gained great ground recently worldwide because the equipment is very inexpensive and can be readily deployed for both fixed wireless backhaul and mobile broadband applications. WiMax backhaul equipment can literally be purchased any day of the week form a wireless installation company or wireless distributor. Most outdoor wireless installation companies have equipment on the shelf. Although LTE is a natural progression for carriers that have an existing 2G / 3G networks, countries that do not have a built out cellular network, WiMax backhaul is an easy choice to jump to.

One big difference is that LTE is solely a licensed microwave technology that carriers are utilizing their existing licensed spectrum, where WiMax backhaul is mostly unlicensed (at least in the USA with the exception of a small slice of spectrum in the 3.65GHz space). Many carriers are having the WiMax backhaul manufactures produce outdoor wireless point to multipoint radio equipment that will work in their licensed bands.

Wireless as a Green Technology? Actually it is based on power consumption and impact on the environment. Green technologies are the talk of the town as the world community tries to preserve our planet's natural resources by turning to cheaper and more efficient energy sources. Data and telecommunications are one of the fastest growing industries worldwide. How often do people think about the environmental impact of the broadband infrastructure rapidly being deployed?

For years the USA has relied on fiber infrastructure to provide its broadband backhaul. Fiber deployments require installing fiber cable either by aerial means (strung from pole to pole along a particular route) or by trenching the ground to put fiber in underground conduits. Both impact the environment. Aerial fiber requires a lot of PVC and rubber based jacketing to protect the fiber. These materials are not good for the environment. Aerial fiber also requires poles, either metal or wood, to be placed every 100ft or so. Underground fiber is put into conduits which eventual have a soil impact. Plus the trenching of natural land impacts nature. One must also take into account CO2 emissions that are produced in the construction and deployment of fiber.

Wireless backhaul, such as a point to point wireless Ethernet bridge, can provide data connectivity over 50+ miles. A single communications tower can be a hub site for many fixed wireless backhaul antennas. Existing buildings offer rooftop space that can be used so no new mounting infrastructure needs to be constructed.
Today many point to point wireless Ethernet bridge systems operate at 20W to 35W (-48vDC). Most point to multipoint wireless Ethernet bridge systems can run on POE (802.3af) or POE+ (802.3at). These systems have such a low power draw they can easily be powered by solar or wind generation.

  

Take for example a solar powered repeater site used for a client's video backhaul. On a hill above a reservoir, where there was no local power available, two solar panels provide enough energy to power a point to multipoint wireless system that backhauls multiple PTZ IP cameras located a mile away and a point to point wireless Ethernet bridge to a remote facility 4 miles away. The outdoor wireless system is powered by recyclable batteries that are charges during the day by the solar panels. The systems provides up to 5 days of survivability in the event of the solar system failing.

Installing a solar powered wireless backhaul system is relatively inexpensive, compared to running AC circuits. A quick ROI can be achieved from the savings of equipment shelter leasing costs and monthly power costs. Plus you'll be doing your part to help the environment!