Alpha Omega Wireless Blog

Licensed point to point wireless bridge systems are now becoming more of the norm rather than the exception. Historically, everyone turned to fiber as their primary choice for point to point data connectivity. Now with the recent changes to FCC regulations on point to point microwave, also referred to as “ptp wireless”, the opportunity to create high-speed bandwidth wireless point to point connections are easier than ever.

Wireless connectivity and wireless mobility has become a way of life. Today most everyone is carrying a mobile device and expects to have high speed wireless bandwidth everywhere they go. In many cases, people now have more than one wireless device carrying around their smart phone and their tablet device (e.g. iPad). A major problem in the wireless industry is when wireless networks get overloaded due to the high density of users on a local network. This problem becomes even greater when you have events that have thousands of people all trying to get online with their wireless devices all at the same time. Cellular networks can get slammed. This is why many carriers try and off load people onto Wi-Fi hotspots in order to free up the demand for their 3G / 4G networks.

A rule of thumb is to have a max capacity of 40 active Wi-Fi users on an access point at any given time. Now many manufactures have pushed that limit by using various techniques like timing algorithms, but as a general rule for high performance 40 is a good number. In high density wireless applications the thing to remember is that even if everyone is not trying to use their wireless handheld device, the devices still beacon the network. This causes a lot of traffic and overhead to an access point.

So what happens when you put thousands of people in a small area all trying to get a wireless Ethernet bridge using Wi-Fi connectivity? If you do the math you would have to add a lot of wireless access points in an area to handle the load. With Wi-Fi 802.11b/g 2.4GHz there are only three non-overlapping channels. In Wi-Fi 802.11a there are 8+ depending on the channel widths. Most all devices will try and use the 2.4GHz 802.11b/g Wi-Fi first by default. With only three non overlapping channels it becomes difficult to put a lot of AP’s next to each other in a small place, especially if the AP’s are using omni directional antennas. You have to do strict channel and power planning.

Recently, we were asked to provide Wi-Fi for over 3000 users in an area of 100ft x 500ft for an outdoor high profile event party for SXSW. We were able to not only provide Wi-Fi for that many users but where able to provide high speed seemly roaming without any problems. How did we do it?

First, we brought in a 300Mbps full duplex wireless backhaul to the event from a location across town using microwave communication. We didn’t have direct line of sight so we used a rooftop to create a wireless repeater. We did a point to point wireless shot from the main building to the wireless repeater and then another point to point wireless bridge down to the outdoor event. We used 24GHz SAF Tehnika Lumina radios for the microwave communication.

For the Wi-Fi at the event we choose to use a Wi-Fi array system by Xirrus. Xirrus arrays use multiple AP’s with sector antennas to distribute the Wi-Fi signals much like a cellular site design. This allows for greater output and better RF channel control. With the Xirrus system we were also able to force devices that had 802.11a 5GHz capability onto a 5GHz AP to free up the demand of the 802.11b/g 2,4GHz AP’s. Each Xirrus array has its own built in controller which communicates with every other array in the system. This was very effective and saved on costs of having to have an expensive traditional Wi-Fi controller on site. We weren’t able to cable each array directly so in some cases we used a millimeter wave solution to create a wireless Ethernet bridge between arrays.

The crowd loved it and it was amazing to be able to have wireless roaming capability on my iPad while Skyping my wife who couldn’t attend the event!

What do you do when you need to provide Internet connectivity for one of the largest live music and film festivals in the world? You build out a wireless backhaul network using point to point microwave!

At the 2011 SXSW (South by Southwest) Film and Music Festival tens of thousands of people from around the world swarmed to Austin, TX to experience the latest in film and see the over 2000 bands that played live at over 200 venues. The SXSW event merges film, music and technology all in one place. Technology is playing an even larger role at SXSW. It was the place that Microsoft launched their new IE9 platform.

Austin was filled with members of the media reporting on the events and who's making news in the film and music industry. Bloggers are found on every corner writing about who's playing and getting signed to large record labels. Live concerts were broadcasted live over the Internet. Bands like the Foo Fighters, Duran Duran, Blue October, Kid Rock, Snoop Dogg, Bob Schneider, Crystal Bowersox, and many others showed up without much warning to perform.

In years past, one of the biggest complaints was the lack of broadband connectivity, that's if you could get connected at all. With so many people in such a concentrated area many of the cellular networks get overloaded and come to a crawl. Add to the fact that there is now a 1 to 1 or even a 2 to 1 ratio of wi-fi enabled devices to people. Laptops, iPhones, iPads, and all the other smartphone devices were present everywhere. This year SXSW wanted to make sure that they could enhance the attendees experience by bringing wireless bandwidth to the people.

SXSW could get a large (GigE) Internet pipe to their corporate office but couldn't get connectivity to the major facilities by the local telecommunication providers. With months of planning At&t, Time Warner, Verizon, etc. failed provide a temporary wireless solution. So they turned to Alpha Omega Wireless to solve the problem. We were able to build out a high bandwidth, point to point wireless backhaul network from their facility to some major venues around Austin. Even though the fiber providers couldn't do it with months of advanced notice the wireless installation of SXSW's wireless broadband was deployed in days.

Because of the bandwidth demand we used full duplex microwave radios, such as SAF Lumina licensed microwave and 24GHz unlicensed wireless ethernet bridges, BridgeWave 60GHz wireless links, and a few unlicensed wireless bridges for specific events. Most venues were able to get 100Mbps full duplex wireless connectivity.

Wireless backhaul used for the core network distribution and last mile wireless used to provide bandwidth to special event venues gave SXSW a lot of flexibility and the ability to provide wi-fi to attendees. Once the event was over the equipment was removed as if it was never there.

As a Wireless Integrator, that has deployed thousands of wireless Ethernet bridges, I am a firm believer that wireless technology for broadband backhaul not only provides a phenomenal value but in many cases is a better technology for broadband backhaul than traditional fiber / copper infrastructure. Wireless backhaul, whether we are talking about point to point wireless backhaul, using licensed microwave or an unlicensed wireless Ethernet bridge, point to multipoint wireless Ethernet backhaul (using 5GHz unlicensed wireless band or WiMax), or wireless mesh,  can provide greater reliability, last mile presence, quicker deployments, and is far cheaper than hard line infrastructure.

You can say, “Well you do wireless backhaul for a living so you are biased.” Let me tell you about a recent trip I took to a third world country and experienced a natural disaster. Recently I was on the island of Roatan in Honduras while a hurricane passed over the island. We experience sustained winds of 70+mph (with gusts of 100mph) and about 4 inches of rain. During the storm I was uploading photos to Facebook because I had a fast, uninterrupted full 3G cellular services without any outage or latency.

Remember Katrina? Well most of all the fiber networks in New Orleans were wiped out and untill today it hasn't been all fully replaced. Immediately after the hurricain there wireless networks were installed all over to provide voice and data connectivity.

All throughout the Caribbean and Central America most countries have leapfrogged the USA in the use of wireless backhaul for telecommunications and broadband services. A lot of countries can’t run fiber due to terrain (jungles, mountains, waterways, and a lack of infrastructure) and the pure inability to afford a fiber build out. Wireless though is everywhere. You can be in the jungles of Belize and have a solid 3G connection.  

In order to get broadband connectivity and voice service many of the Caribbean islands depend on point to point microwave connectivity. Then cellular and point to multipoint wireless is used to distribute wireless broadband around the island. One would wonder how well the service coverage would be and the quality of the wireless installation would be in a third world country. After seeing first hand during a hurricane I would say it’s pretty good! Back home in the USA where I am served by a local cable provider my internet connection gets knocked out all the time when we have a storm of 30 to 40MPH winds

Wireless backhaul is far easier and cheaper to deploy than fiber. Broadband wireless networks also allow for a lot of flexibility in access to a POP (point of presence) and network design. The greatest concern most people have with using wireless backhaul is if it’s reliable. From what I experienced I would say it’s extremely reliable. Understand that microwave radio equipment uses extremely little power. In most cases a microwave radio can be powered on a battery or over solar. Most outdoor radio units use -48vDC at 30W. A standard UPS can keep a wireless end node powered for hours. If installed properly a wireless network can provide 99.999% reliability. See my previous articles: “Does Weather Effect Wireless? The 5 Misconceptions - Part 1” and “Is Wireless Reliable? - The 5 Misconceptions - Part 2.”

Like I always say, if wireless backhaul is properly engineered and the wireless installation is done properly it is extremely reliable!

Wireless backhaul, often referred to as fixed wireless backhaul or wireless Ethernet bridges, has become a standard for creating network connectivity between locations. Wireless backhaul can be used for establishing data network connections from building to building, field locations to a network presence, connecting network fiber segments, or last mile connections, etc. Wireless Ethernet bridges can also be used for connecting devices on to networks, like IP video cameras, SCADA devices, client devices, phones, two-way radio / pagers, etc.

Wireless backhaul can be in the form of point to point wireless, point to multipoint wireless, or wireless mesh configurations. Wireless bridges can be licensed microwave links or unlicensed wireless Ethernet bridges. A licensed microwave link or wireless Ethernet bridge can provide throughput as low as 10Mbps up to GigE full duplex (with gigabit wireless).

Wireless Ethernet bridges, allow you to eliminate reoccurring costs of leasing fiber from telecommunication companies, eliminate the cost of additional head end equipment, and AES encryption hardware devices. Wireless Ethernet bridges preserve native IP throughout the system. Because you own the microwave link connection and not lease it, ROI is maximized with a low CPEX. You also gain the peace of mind of having control over your own infrastructure.

Take for example the cost to lease a DS3 (45Mbps) connection through a carrier. A typical scenario is that it costs roughly $4000.00 a month with a 3 to 5 year contract. Over three years that’s $144,000.00! Let’s not forget that it also typically takes 3 to 6 months to provision.

Now for comparison, let’s look at a point to point wireless Ethernet bridge using a licensed microwave radios. Although you can install a 50Mbps full duplex (100Mbps aggregate throughput) wireless bridge, most systems are typically purchased at 100Mbps full duplex (200Mbps aggregate throughput) because there just isn’t much cost differential between a 50Mbps and 100Mbps full duplex licensed microwave link. It’s typically the same radio system and just software throttled. Most licensed microwave radios are capable of 366Mbps full duplex (732Mbps aggregate throughput) and 60GHz and 80GHz millimeter wave is GigE full duplex.

A typical 100Mbps full duplex licensed microwave link, which can be installed in several days rather than 4 to 6 months like a DS3, would have a CAPEX of $20,000.00 to $30,000.00 depending on the frequency and distance. Say you add in a 5 year advanced replacement manufacture warranty and annual support from the integrator at a cost of $15,000.00. That’s roughly $45,000.00 compared to $144,000.00. That gives you an ROI of roughly 11 months. Plus you have over double the bandwidth!

As you compare higher bandwidths like leased 100Mbps or gigabit fiber the ROI is increased even further. Most GigE wireless backhauls have an ROI of 3 to 4 months. That’s it. No more reoccurring costs because you own it. If a wireless Ethernet bridge is properly engineered and the wireless installation is done by a professional wireless integrator a point to point wireless backhaul can provide greater security over leased lines and give 99.999% reliability (meaning <5min of predictable outage a year). Most telecommunication companies can only guaranty 99.9% on a SLA because they know they’ll have network outages throughout the year.

Wireless backhaul in the form of point to point microwave - licensed microwave links or unlicensed wireless Ethernet bridges, point to multipoint wireless Ethernet bridges, or wireless mesh network infrastructures can provide up to 99.999% reliability and keep you up and running when your telecommunications provider fails you.

Do you ever experience downtime on you network due to outages with your telecommunications provider, such as: AT&T, Verizon, or Comcast? What does a network outage cost you organization in dollars and man hours due to lack of productivity and internal communication or with clients? What do you say? This never happens? Think again!

You think you’re safe because you have a point to point fiber connection from your telecommunications vendor? Read my article “Outdoor Wireless Bridges or Fiber, Which Do You Trust.” What if you use an MPLS network, doesn’t that provide you failover redundancy? What about having different carriers for a backup connection? Or what about using cellular modems as a last result? Aren’t you protected by having redundancy? Not really!

The true fact is that the major telecommunications companies have outages all the time. December 11^th, 2009 San Francisco experienced a several hour AT&T outage. July 21, 2010, AT&T Wireless had a regional outage for hours in NC. On April 9^th, 2009 Santa Clara County, CA declared a local emergency when someone intentionally cut an underground fiber optic cable in South San Jose taking out cellular, internet, and phone usage to AT&T, Verizon, and Sprint/Nextel customers. This affected multiple cities. A local hospital had to cancel surgeries due to the emergency. Recently, Union City, CA experienced a city wide outage when central office went dark. All voice, internet, MPLS, cellular, etc. was out for almost 10 hours.

So what happens when you have no cellular, internet, data, or voice connectivity?  For some organizations they have critical operations that have to be monitored so they have to be physically manned if the network goes down. What’s the cost to deploy people to remote sites or work overtime during the middle of the night? What about lost data? Some organizations can run into the millions of dollars an hour during a network outage.

Too often organizations fail to ensure their communications, both data and voice, are protected by not having appropriate redundancy or just flat out relying on a third party telecommunications vendor. Many times those who have a redundancy solution in place don’t have “True Redundancy.” Many overlook their WAN connections or have single point of failures in using the same medium (such as fiber), or taking the same external routes (out the same conduits from their MPOE), or have unknown points of failure by relying on third party telco providers’ networks. You can have MPLS but if you first connect through a local central office and that CO goes dark there is an issue. Even with backup power central office have gone dark (recently in Union City, CA) and fiber lines have been cut (San Jose, CA).

Wireless backhaul connectivity, both point to point wireless links and point to multipoint wireless bridges, provide an avenue for extremely reliable primary connections and for creating “True Redundant” network paths and connections. With both unlicensed wireless Ethernet bridges or licensed microwave links, an organization can create a completely separate stand alone network and eliminate the dependency on third parties equipment and facilities, and remove the risk of failure of fiber cuts off site and out of an organizations control.

So why own your own wireless backhaul network? Wireless backhaul, with proper wireless path engineering, the use of the right outdoor wireless backhaul equipment, and proper wireless installation can provide truly reliable networks. See articles, “Is Wireless Reliable? - The 5 Misconceptions - Part 2” and “Outdoor Wireless Installation Done Properly.”

Wireless backhaul can have multiple advantages. Wireless networks can be used for primary or redundant links. Throughput can match or even exceed that of a leased line from a telco. You can get connectivity where you can’t get it from a telco for last mile solutions. Wireless backhaul typically has an extremely low ROI and can eliminate reoccurring lease line costs. Wireless installation can be done in days compared to months of provisioning time from a telco. Also with wireless backhaul you have complete control of your network. Even in the event of equipment failure wireless nodes can be restored quickly by simply hot swapping the radio communications equipment.

That’s right no more trouble tickets from some call center agent in another country!

Wireless backhaul, also known as fixed wireless, technology has become a standard means of creating a data communications link between locations. Microwave radio links can be used to make data connections from building to building, to connect remote field locations to a network presence (also known as last mile wireless), connecting network fiber segments, and for connecting network devices (like IP video cameras, SCADA devices, client devices, phones, two-way radio / pagers, etc.) to networks.

Wireless backhaul can be in point to point wireless, point to multipoint wireless, or wireless mesh configurations. Wireless bridges can be licensed microwave links or unlicensed wireless Ethernet bridges. A licensed microwave link or unlicensed wireless Ethernet bridge can provide throughput as low as 10Mbps up to GigE full duplex (with gigabit wireless). There are many wireless backhaul radio platforms offering a solution to just about any application. Wireless backhaul systems can provide 99.999% reliability. A Point to point wireless Ethernet bridge or licensed microwave link can enable high capacity wireless backhaul connections from less than one mile to more than 50 miles, without performance degradation. Licensed microwave links and unlicensed wireless Ethernet bridges enable carrier class delivery of IP services with full wire-speed performance. Typical latency on a wireless Ethernet bridge or licensed microwave link is under 1ms.

Even though there are some outdoor wireless radio systems that can do non-line-of-sight (“NLOS”), the majority of wireless backhaul requires line-of-sight (“LOS”) with proper Fresnel Zone clearance to properly operate. This means the transmitting and receiving antennas most be able to see one another with any obstructions. In most cases this requires mounting the antennas on a structure with adequate height to create LOS.

Many times when doing a point to point microwave link from one tall buildings roof top to another’s it can be easy to have LOS.
Sometimes this is not possible. Putting a antenna mast on a roof top can sometimes be sufficient. Other times it may become necessary to construct a communications tower. The first reactions that come to a client’s mind when a wireless installation vendor says a tower need to be built is no way. Several misconceptions arise. Towers are too expensive, unsightly, and are a huge construction project. Reality is that none of these are true.

Communication towers are relatively inexpensive to have installed. Leasing high speed bandwidth form a telco or installing dark fiber is extremely expensive. Point to point wireless backhaul or creating point to multipoint wireless Ethernet bridges for last mile connections have a rapid ROI (typically less than 6 months with no reoccurring costs). Adding a tower into the solutions may only add 3 to 4 months until the CAPEX achieves and ROI. Free standing towers from 40ft to 80ft in height can be installed from $15,000 to $35,000. That is not much money when you look at the big picture.

Build it and they will come! Communication towers are typically built for an initial solution but can offer great potential for future wireless backhaul projects. The tower may have been built to accommodate a point to point wireless bridge like a licensed microwave link between two locations. Now in place it may be used for other wireless Ethernet bridges or point to multipoint last mile wireless bridge connections. Odds are that if you needed to build a tower to gain some height in a geographical area other may need some height too. Leasing opportunities can come knocking on the door. Tower can create a great source of re-occurring revenue for an organization by leasing antenna space off to other parties that need a repeater location or leasing space to the mobile carriers, like At&t, Verizon, Sprint, Clearwire, etc. These opportunities can pay for the tower itself.

The fact is that there are tower all around us and we just don’t even notice them. Microwave communication towers tend to blend into the skyline. So many times we hear about cosmetic concerns when it comes to mounting antennas on buildings but the fact remains that they are all around and no one ever notices them (unless you are in the wireless industry and pay attention to them). Many are less obtrusive that satellite TV dishes everyone mounts on their homes!

Microwave tower have been manufactured in ready to deploy configurations and even come with approved engineered design drawings making the permitting process simple. Communication towers used for wireless backhaul can typically be installed within a few days and offer a long term solid structure for mounting wireless backhaul antennas and equipment.

Choosing the right outdoor wireless vendor is critical for the success of a wireless backhaul project, whether it’s a licensed microwave link, unlicensed wireless Ethernet bridge, wireless mesh, WiMax, point to point wireless backhaul, or point to multipoint wireless Ethernet bridges. Not all wireless vendors or wireless installation companies are the same. Too many companies and people claim to be RF Engineers or outdoor wireless backhaul experts without ever having any real world project experience.

Some wireless vendors are just “box movers” with a sole purpose to sell hardware. These companies typically do not have any field experience with wireless installations, wireless site surveys, or spectrum analysis. They may be able to do wireless path calculations using some software programs, but the information they use for the outdoor wireless network design is based on information they receive from the client. Because they lack any real world filed experience they tend to miss the fine intricacies that can make or break an outdoor wireless backhaul project. They also typically try and push to the customer whatever product makes them the best margins.

Some “so called” wireless vendors come with the IT networking background. They too lack any real world outdoor RF or microwave experience. They may focus on a conceptual wireless network design but have no understanding on the details of what it takes to actually install and maintain an outdoor radio system. Everything looks great on paper but when it comes time to install the system and make it work everything goes south when there is a huge groove of trees or buildings in the way! These companies might be good at the network integration portion of a project but have no clue to the way outdoor wireless systems perform in the field or what it takes to properly do a wireless installation.

There are some great outdoor wireless vendors that have a ton of outdoor radio system experience but lack any knowledge of integrating the wireless infrastructure to the client’s network.

A true outdoor wireless integrator will have in house experience with all aspects of an outdoor wireless backhaul system. A good wireless integrator will know how to properly design a wireless backhaul network, perform accurate wireless path calculations, and understand exactly what it takes to deploy a wireless backhaul network.

The good companies have experience with point to point unlicensed wireless Ethernet bridges, licensed microwave links, wireless mesh, point to multipoint wireless bridges, etc. These companies know the industry and can make appropriate recommendations on whether unlicensed wireless Ethernet bridges or licensed microwave links are right for the backhaul solutions or which is the right fit between wireless mesh and point to multipoint wireless bridges. Good wireless vendors also understand IP networking and can integrate the outdoor wireless system into the client’s network.

The good outdoor wireless integrators have experience working with towers, poles, and on roof tops. They know exactly what the mounting and power solutions need to be and what goes into the proper wireless installation of the radio equipment. True wireless integrators can properly plan, price, and insure success of an outdoor wireless backhaul project.

What about after the project? Many “so called” wireless vendors come across knowledgeable about designing a radio communication system or claim that have a lot of wireless installation experience. The question to ask is if something goes wrong or there is an issue down the road, will the wireless vendor be there for support. Did the wireless vendor rely on subcontractors for the project? Will they need to coordinate with subcontractors to support the client’s system? What will they charge to perform support if they do need to rely on a sub? These are important questions. The “so called” wireless vendors can’t control if their subs will be around in the future or what they may charge. What about the amount of time it would take to get different companies involved and dispatched?

A good wireless integrator performs all the work themselves and does not rely on subcontractors. They can take full ownership of the outdoor wireless system and can support it.

Wireless backhaul, whether you are talking about wireless mesh, WiMax, point to multipoint wireless, or point to point wireless backhaul, systems can function with extreme reliability and predictability with proper wireless network design, wireless engineering, and a quality wireless installation. The mobile wireless carriers take this matter critically and waste no expenses on ensuring their systems are installed properly. Any down time can cost them tens of thousands of dollars. The craziest thing is when organizations are willing to rely on wireless technology for their primary connectivity but pinch pennies by choosing the cheapest and many times least experienced wireless vendor or wireless installation companies for their projects.

The terms "unlicensed wireless bridge" and "licensed microwave link" refer to the radio frequency spectrum characteristics set by the U.S. Federal Communications Commission ("FCC") or equivalent national government regulatory body. Licensed products require regulatory approval before deployment while license-exempt products can be deployed without any regulatory approval.

Licensed microwave communication links offer true full duplex communications. Licensed microwave wireless systems are becoming more popular as a result of wireless interference in unlicensed wireless spectrum. Licensed microwave radios provide security from the risk of interference from other RF systems. In a licensed system the channels that the radio system transmits and receives on are owned by the user and are registered with the FCC for frequency coordination. Getting a license is inexpensive and can be obtained in the matter of weeks.

The most common wireless backhaul, known as a wireless Ethernet bridge, operate in the unlicensed wireless (license-exempt) 900MHz (902-928), 2.4GHz, 5.3GHz, 5.4GHz, 5.8GHz frequencies of the RF spectrum and are exempt from FCC licensing requirements. There are also 24GHz, and 60GHz wireless bridge point to point links that are considered unlicensed wireless, but are typically immune to interference. This means the system operator does not have to apply for and purchase a fixed microwave communication link license from the FCC. These systems, although quick to deploy, do not promise exclusive use of the band and are susceptible to potential interference.

Recently we had a client that was operating two wireless backhaul networks for roughly four years using two sets of Motorola PTP600 unlicensed wireless Ethernet bridges. When they were originally installed they were getting almost 300Mbps aggregate throughput (this is like having 150Mbps full duplex throughput). Over the years the wireless bridges started to get hit with interference. The PTP600 wireless backhaul radios do channel hop to try and operate on a cleaner frequency channel when they receive high levels of wireless interference. They also can down step their modulation to create a better RF communication, which also lowers the radios wireless throughput capacity. They ended up struggling with only about 30Mbps aggregate throughput due to the amount of wireless interference they were being hit with.

We ended up replacing the Motorola PTP600 unlicensed 5.8GHz wireless Ethernet bridges with SAF Tehnika CFIP Lumina licensed point to point microwave links. The new wireless bridges operate in the licensed 18GHz frequency. The SAF Lumina licensed microwave links are now providing the client with 366Mbps Full Duplex (over 720Mbps aggregate) throughput. Because the SAF Lumina are licensed wireless and the frequencies are now owned by the client they are operating interference free. We were also able to downsize the antenna sizes to smaller parabolic dishes.

Unlicensed point to point wireless bridges became very popular because anyone could buy them and deploy them with little experience. Note: even unlicensed point to point wireless links should be installed by certified professionals, see my article "Outdoor Wireless Installation Done Properly". Licensed microwave communications can be daunting for those that don't understand it. Licensed microwave point to point wireless links provide far greater performance, security, and longevity. Today licensed microwave wireless bridges are about the same price as any carrier grade unlicensed point to point wireless Ethernet bridge. Licensed wireless links do need clear LOS where unlicensed wireless links can be used in nLOS applications.

If you have good LOS and want true fiber replacement on a primary network connectivity path licensed microwave links should be considered over unlicensed wireless bridges.

The term "Microwave" is a broad term that covers the UHF (Ultra High Frequency with frequencies between 300MHz and 3GHz) to the EHF (Extremely High Frequency with frequencies between 30GHz to 300GHz). Licensed microwave links and unlicensed wireless Ethernet bridges typically operate in the SHF (Super High Frequency with frequencies between 3GHz to 30GHz) and the EHF bands.

The terms "unlicensed wireless bridge" and "licensed microwave link" refer to the radio frequency spectrum characteristics set by the U.S. Federal Communications Commission ("FCC") or equivalent national government regulatory body. Licensed products require regulatory approval before deployment while license-exempt products can be deployed without any regulatory approval.

Licensed microwave link frequencies used for wireless backhaul in a point to point wireless backhaul operate 6GHz, 11GHz, 18GHz, 23GHz bands and the 80GHz millimeter wave E-band. Unlicensed wireless Ethernet bridges, used in point to point wireless bridges, point to multipoint wireless bridges, or wireless mesh configurations, typically operate in 900MHz, 2.4GHz, 5.3GHz, 5.4GHz, or 5.8GHz frequencies. There is also the 60GHz millimeter wave band that is used for point to point gigabit wireless bridges.

There are registered frequencies that many think are licensed but are actually unlicensed, like the 3.65GHz WiMax band used for point to multipoint wireless backhaul and the 4.9GHz Public Safety band. These registered bands do provide some protection against interference but only require local users to coordinate with one another on frequency channel coordination. This is often confused by Public Safety organizations that think the 4.9GHz band is for exclusive use by local law enforcement. Anyone can register the use of the 4.9GHz band as long as it's used for some form of public safety, such as video backhaul.

Licensed microwave wireless radio systems are typically built and designed for long term solutions. Point to point licensed microwave links are true fiber replacement systems and offer full duplex wireless communications for both Ethernet and TDM. The licensed wireless bridge hardware is designed to provide carrier grade performance (high bandwidth and low latency). Because a microwave link is licensed and is not to inject and interference on other licensed microwave backhaul operators in the area they must have LOS (line of sight) and not cause heavy multipath. This is a common question of why licensed microwave radios don't use OFDM or MIMO and why they can't be used in NLOS (non line of sight) applications. In a NLOS wireless link application unlicensed wireless backhaul radios that use OFDM or MIMO take advantage of multipath for their connectivity.

Microwave communication using unlicensed wireless Ethernet bridge systems have been an extremely popular choice for outdoor wireless backhaul. The unlicensed spectrum of 5GHz (5.3GHz, 5.4GHz, and 5.8GHz UNII bands) became a primary selection by many end users and outdoor wireless installation VAR's, because of their flexibility, cost effectiveness, rapid ROI, and quick deployments. Many outdoor wireless manufactures started introducing "value line" point to point wireless Ethernet bridges using 802.11 chipsets. Basically, the same radio boards found in Wi-Fi access points put into an outdoor enclosure and using outdoor wireless antennas. 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. The major issue with unlicensed wireless Ethernet bridges is potential wireless interference.