Alpha Omega Wireless Blog

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.

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.

Wireless backhaul, also known as fixed wireless bridges, has become a standard means of creating a microwave communication between locations; whether building to building, last mile wireless to connect remote locations to a network presence, or for connecting devices like IP video cameras, access control, SCADA devices, client devices, or phones to networks. Wireless backhaul can be deployed in several network configurations.

A point to point wireless bridge is when only two microwave radio ends are bridged together to create a single wireless network path. Point to point wireless links are an ideal complement or replacement to leased lines and fiber. A point to point microwave link is used to create a wireless bridge network between two buildings to connect LAN connectivity or for creating a microwave link between two towers to join two WAN network segments together across large distances. Point to point wireless bridges can be licensed microwave links or unlicensed wireless Ethernet bridges and can provide throughput as low as 10Mbps up to GigE full duplex (with gigabit wireless).

Licensed microwave links used for point to point wireless backhaul operate in the 6GHz, 11GHz, 18GHz, and 23GHz frequencies and provide true full duplex wireless Ethernet and TDM communications. Licensed microwave links can provide up to 366Mbps full duplex or 732Mbps aggregate throughput using a single radio unit. Dual radio units can be combined on a single antenna to provide double the bandwidth and complete failover redundancy.

A few exceptions are the 24GHz microwave links that are unlicensed but work just like the licensed 23GHz microwave links and provide the full duplex connectivity and the 60GHz millimeter wave systems that provide up to full duplex gigabit wireless backhaul. There is also the 80GHz millimeter wave E-band that is a registered frequency that is used to provide gigabit wireless links. Unlicensed point to point wireless Ethernet bridges typically communicate in TDD because they use the same frequency channel to talk and listen. They can provide up to 300Mbps aggregate throughput.

Point to multipoint wireless Ethernet bridges use a hub spoke configuration using a Base Station Unit ("BSU" or "AP") that communicates with multiple Subscriber Units. This is similar to a cellular network where multiple mobile devices talk back to a cell tower location. Point to multipoint wireless backhaul systems are ideal for interconnecting campus buildings, security systems, control systems, IP video surveillance cameras, WISP applications, integrating remote business sites, or installing last mile connections. Point to multipoint wireless bridges operate in the unlicensed wireless frequency bands of 900MHz, 2.4GHz, 5.3GHz, 5.4GHz, or 5.8GHz. Point to multipoint wireless Ethernet bridges can provide up to 300Mbps aggregate throughput.

Wireless mesh configurations are used to create a wireless network where a radio node can communicate with two or more other wireless mesh nodes. Wireless mesh networks offer great redundancy. If one wireless mesh node can no longer operate, all the other wireless mesh nodes can still communicate with each other, directly or through one or more intermediate outdoor wireless bridge links. Each wireless Ethernet bridge link can send and receive messages in a wireless mesh network. Each link also functions as a router and can relay messages for its neighbors. Through the relaying process, a packet of wireless data will find its way to its destination, passing through intermediate links with reliable communication.

Mesh wireless backhaul networks are typically configured in a star topology or can be in a daisy chain configuration. They are used a lot in networks for wireless video backhaul and municipal wireless networks. Wireless mesh radios operate in unlicensed wireless backhaul frequencies like that of point to multipoint wireless bridges and can provide up to 300Mbps aggregate throughput.

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!