Alpha Omega Wireless Blog

Thinking of a Wireless Backhaul? Consider This

Posted by Joe Wargo on Thu, May 20, 2010 @ 02:57 PM

The wireless backhaul industry is booming and not just because of the build out of 4G, like WiMax backhaul and LTE. Government agencies, utilities, and private industry are all realizing the benefit of point to point wireless backhaul, point to multipoint wireless bridges, and wireless mesh. Microwave communication, also known as fixed wireless backhaul, is a great network solution because of its quick ROI, high throughput speeds, quick deployments, extreme reliability, and as a wireless last mile solution the ability to get bandwidth where traditional cable and fiber infrastructure is not available.

Outdoor Wireless BackhaulSo how does someone that is not a wireless backhaul expert decide what the right wireless backhaul solution is and what wireless equipment to use? There are so many outdoor wireless vendors that claim their wireless hardware is the best. Who do you believe and how do you know you are getting the best solution? Whether a licensed microwave link or an unlicensed wireless Ethernet bridge, here are a few things that someone looking into a microwave communication solution should consider:

Hire a Good Outdoor Wireless Integrator
People that have deployed indoor Wi-Fi sometimes think that doing a wireless installation of an outdoor wireless backhaul is something they can do themselves. Understand that Wi-Fi is pretty easy to deploy indoors and is very forgiving. Outdoor wireless bridges are a whole other story. Outdoor wireless backhaul needs to be properly engineered. There are considerations about frequency coordination, spectrum analysis, Fresnel Zone criteria, multipath issue, signal propagation, EIRP regulations by the FCC, security, and so on. Hiring a good outdoor wireless integrator or wireless installer will ensure a successful wireless deployment. An outdoor wireless integrator can provide a proper wireless network design, perform a wireless sight survey, and help pick the right wireless hardware solution.

Understand the Solution Before Choosing the System
So many times an end user finds out that wireless backhaul might be a good solution to a networking need by a case study or white paper from a wireless manufacture. Naturally they may call the manufacture to get more information. That's where the issue starts. It becomes the particular wireless manufacture sales rep's job to fit their wireless radio system into the end user's solution, whether they are a good fit or not. The best approach it to fully understand what the wireless backhaul solution is first. Is it a point to point licensed microwave link or an unlicensed non line of sight wireless bridge that is right for the application? Once you understand what the right wireless solution is then you can look for various manufactures of that type of hardware.

Wireless Hardware Marketing Material Is Just Marketing
Marketing material is great to get an overview of a solution or piece of hardware. But understand that it's the job of a wireless manufacture to position their equipment as the best solution and sometimes the only solution. It most cases the toted performance of a wireless radio is based on optimum conditions and sometimes only achievable in a lab environment. Be sure before choosing a particular wireless backhaul platform to consult a good outdoor wireless installation VAR that works with multiple wireless manufactures and has personally installed the wireless hardware that can help decipher hype from reality.

Choose Proven and Field Tested Wireless Backhaul Systems
There is nothing better than getting positive feedback from a peer or other organization similar to yours on what type of outdoor wireless they have experienced and finding out what works and what doesn't. When you have done thousands of wireless installations you learn real quick what wireless equipment is good and what wireless systems are junk.

Know the Wireless Equipment You are Buying
There are so many outdoor wireless companies that come and go. Many wireless hardware platforms are not actually made by the so called wireless vendor. There are a handful of manufactures that OEM their wireless bridge equipment to other companies that put their label on it, change the graphics on the software and call it their own. The problem is who really knows the engineering behind the microwave radios and who can provide quality support for it. A lot of the wireless bridge equipment is cheaply made but allows for a so called wireless manufacture to make good profit margins without having any of their own R&D and testing costs.

Have a Professional Wireless Installer to Do It Right
Again, there are a lot of factors that go into a good reliable outdoor wireless backhaul system. A good wireless installer is worth their weight in gold. No matter how good the wireless hardware is, if it isn't installed properly you'll have issues (see "Outdoor Wireless Installation Done Properly").

Tags: General, Wireless Industry, Wireless 101

WiMax Backhaul – What it is and what it’s not, Part 2

Posted by Joe Wargo on Mon, May 03, 2010 @ 02:04 PM

From Part 1, we described how WiMax backhaul is a point to multipoint wireless backhaul technology used to create high bandwidth wireless Ethernet bridges between a Base Station Unit (or an array of BSU's) to a Subscriber Unit (or CPE device). WiMax backhaul in the USA, according to the regulations of the FCC, is 50MHz wide of the 3.65GHz frequency band and is a non-exclusive use of microwave wireless, although a service provider must register the wireless bridge broadcast. In other countries the unlicensed wireless 3.5GHz band is common. Licensed microwave 2.5GHz is used by some carriers.

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.

WiMax Backhaul Coverage

If you need a point to multipoint wireless backhaul solution there has been for years wireless equipment that have the same benefits of WiMax, such as OFDM and use MIMO, that can actually provide much greater bandwidth ( now up to 300Mbps).

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!

Tags: Point to Point Wireless, Licensed wireless, General, Un-lincesed Wireless, Wireless Industry, Point to Multipoint, WiMax, Wireless 101

WiMax Backhaul – What it is and what it’s not, Part 1

Posted by Joe Wargo on Mon, May 03, 2010 @ 02:02 PM

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.

WiMax Deployments Worldwide

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 ForumTM) 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...

Tags: Point to Point Wireless, General, Un-lincesed Wireless, Wireless Industry, Point to Multipoint, WiMax, Wireless 101

Outdoor Wireless Bridges or Fiber, Which Do You Trust

Posted by Joe Wargo on Fri, Apr 30, 2010 @ 04:07 PM

Talk to most IT Network Administrators and they will tell you how great their fiber network is. Mention outdoor wireless bridges, either point to point wireless backhaul or point to multipoint wireless Ethernet bridges, and they'll say a wireless Ethernet bridge is not as reliable as their fiber. This is an obvious response from someone that hasn't experienced a carrier grade wireless installation!

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. 

Fiber on ground

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.

Tags: Point to Point Wireless, Licensed wireless, General, Point to Multipoint, Wireless 101

Non Line of Sight Point to Point Wireless Backhaul

Posted by Joe Wargo on Fri, Apr 23, 2010 @ 01:42 PM

Does an outdoor wireless point to point bridge require Line-of-Sight ("LOS") or can a quality wireless Ethernet bridge perform under Non-line-of-Sight ("NLOS") conditions? LOS is when both antennas in a outdoor wireless bridge system must have clear visibility with one another and have no encroachments to the first Fresnel Zone. In a NLOS situation there is either limited visibility from one wireless antenna to the other (near-line-of-sight or" nLOS") caused by a Fresnel Zone encroachment or complete obstruction blocking the visibility between the two wireless antennas.

NLOS wireless backhaul
The answer depends on the individual path and the throughput requirement. In many cases, if the wireless design and wireless installation is done properly a quality NLOS microwave link will provide good quality high bandwidth.

General Overview of Point to Point Wireless Backhaul:

A typical outdoor wireless backhaul is used to pass higher throughput over greater distances. Outdoor wireless bridges operate in the SHF (Super High Frequency) band in unlicensed wireless backhaul 5.3GHz, 4.9GHz, 5.4GHz, 5.8GHz, and 24GHz or licensed microwave backhaul 6GHz, 11GHz, 18GHz, and 23GHz. There is also unlicensed 60GHz and registered 80GHz millimeter wave in the EHF (Extreme High Frequency) band. The unlicensed wireless Ethernet bridges typically provide from 10Mbps to 300Mbps aggregate throughput. Unlicensed 24GHz and licensed microwave links offer up to 360+Mbps Full Duplex. 60GHz and 80GHz wireless bridge systems can provide up to GigE Full Duplex (gigabit wireless). The higher frequencies do not do well with penetrating obstructions.

For an outdoor wireless bridge to work the system gain must be greater that the total Path Loss. Historically, an outdoor wireless bridge required LOS providing first Fresnel Zone clearance. By having no obstructions in the first Fresnel Zone the receive signal are optimized and the out of phase signals are minimized.

General Overview of Non-Line-of Sight Wireless Bridges
When considering a point to point wireless backhaul, whether a licensed microwave link or an unlicensed wireless Ethernet bridge, one of the first questions asked is if there needs to be LOS to get a microwave link. Many don't understand the difference between wireless bridge technologies that they are use to (like cellular and cordless phones or Wi-Fi) compared to an outdoor point to point wireless Ethernet bridge.

Devices like cellular operate in a range from 800MHz to 1900MHz of the UHF (Ultra High Frequency) band. These frequencies do well with penetrating obstructions but have limited throughput capabilities. Most Wi-Fi operates in the 2.4GHz frequency of the UHF band and can provide higher bandwidth but is very limited in distance. Microwave communication signals are highly attenuated by an obstructed path. In a NLOS microwave link the RF signals will get to a destination by: diffraction around an object, reflection off objects, or by penetration through the obstruction.

For an outdoor wireless bridge, being used for high bandwidth, point to point backhaul to work in a NLOS application there are several requirements that need to be met. Proper power budget, fade mitigation, adaptive link characteristics, and proper demodulation in regards to dispersion. Because of obstructions in a NLOS situation there tends to be a large amount of multipath. Obstructions like trees add to multipath and add attenuation to the overall Path Loss of the microwave link. Trees can be tricky because they are not constant due to movement caused by wind, foliage changes during various seasons, moisture content of the foliage, etc. Constant obstructions like buildings or hills are easier to model and predict.

General Overview of NLOS Wireless Technology

Current wireless backhaul technologies can help in NLOS cases. MIMO (Multiple Input Multiple Output) antenna signaling and spatial diversity reduces the amount of fade margin required. OFDM (Orthogonal Frequency Division Multiplexing) which divides the data into several parallel data streams helping the fading that occurs with multipath. Adaptive rate modulation also helps by giving the wireless backhaul radio the ability to manage the modulation scheme and bandwidth according to the RSL (receive signal level) optimizing the microwave communication link. Outdoor wireless bridges that can take advantage of these wireless backhaul technologies are the unlicensed wireless systems. Unlicensed wireless backhaul using these technologies can provide up to 300Mbps aggregate throughput (depending again on the characteristics of the microwave link path).

A common question of why a licensed microwave link, which can provide higher, full duplex connectivity, doesn't use OFDM wireless or MIMO antenna solutions and why they can't be used in NLOS (non line of sight) applications. In a NLOS wireless link application point to point wireless Ethernet bridge radios that use OFDM or MIMO take advantage of multipath for their connectivity. Because a licensed microwave link is not to inject any interference on other licensed microwave backhaul operators in the area they must have LOS (line of sight) and not cause heavy multipath. If a licensed microwave radio was to cause a lot of wireless multipath it could potentially reflect into another existing licensed microwave communication radio belonging to another party.

Prior to considering a NLOS wireless backhaul, a wireless site survey and a proper wireless path calculation should be performed. Field test may need to be performed in order to verify if a NLOS microwave link will work or to gather accurate estimates on throughput performance. As with any point to point wireless backhaul, a certified expert should perform the wireless installation.

Tags: Point to Point Wireless, Licensed wireless, General, Un-lincesed Wireless, Wireless 101

Wireless Interference - The Effect on Unlicensed Wireless Backhaul

Posted by Joe Wargo on Fri, Apr 16, 2010 @ 06:06 PM

When evaluating wireless backhaul technology, whether point to point wireless, point to multipoint wireless, or wireless mesh, the possibility of radio frequency interference disrupting a wireless link poses a concern. Interference can degrade a radio system's performance and in some cases even prevent the system from functioning at all.

For the purpose of this article "Wireless Interference" is defined as a wireless signal that alters, modifies, or disrupts the desired wireless signal as it travels from the transmitting source antenna to the receiving antenna.

Typical wireless interference is a result caused by the introduction of two or more radio waves being received into the receiving antenna from unwanted radio frequency (RF) signals disrupting the system's communication. Typically these signals are at or near the same frequency as the receive frequency of an established wireless backhaul system. The source of interference is usually from other transmitters operating very close in frequency to the impacted system or caused by "multipath" which is a result of a wireless signal reaching the receiving antenna from two or more paths.

Wireless interference can cause fading or noise on the receiving wireless antenna lowering the quality of signal. Noise is often measured by SNR ("signal to noise ratio") or a relationship of the desired signal quality to the level of undesired or corrupting signal (background noise). This can make it difficult for a wireless system to clearly understand the signal (communications) from the desired transmitting wireless radio. Interference can come into the receiving antenna either in or out of phase. The wireless backhaul system has to differentiate from the signal it should be receiving from its partnered outdoor wireless bridge from the wireless signal it is hearing from the wireless interference source.

This can be thought of in terms much like that of listening to music. Even if the music you are trying to listen to is at a desired volume but there is a lot of background noise, it can be difficult to listen to the music. The background noise can drown out the signal of the desired source causing missed bits of information. In an outdoor wireless backhaul system we see this as errors caused by dropped packets and/or multiple resends having to occur. A wireless link will have a certain threshold of wireless interference it can overcome before experiencing issues. This is often referred to a wireless system's CIR or carrier to interference ratio.

For a wireless backhaul system to operate properly it must maintain a quality receive signal level ("RSL"). Wireless bridges are designed to operate with a certain level of "Fade Margin" that allows the system to operate at a predictable reliability (for most point to point wireless systems 20 to 25dB of Fade Margin is recommended, but many point to multipoint wireless and wireless mesh systems can meet the manufactures requirements at a lower amount of Fade Margin). This means if a system has an RSL of -50dBm and it has a receiver threshold of -72dBm, you'll have 22dB of Fade Margin or the amount of dB signal strength a system can lose before you will experience errors (referred to as BER - Bite Error Ratio) or loss of connectivity.

Even if a wireless backhaul radio receiver has a good RSL the quality of the signal can be distorted by interference. A wireless bridge must have enough Fade Margin to overcome the interfering signal or have good enough CIR to function properly.

Wireless interference in regards to outdoor wireless backhaul often occurs with unlicensed wireless bridges ("license-exempt") operating in the 902-928MHz (spread spectrum), 2.4GHz, 5.3GHz, 5.4GHz, and 5.8GHz frequency bands. Note: 60GHz millimeter wave, often used in gigabit wireless backhaul, is unlicensed but is extremely immune to interference due to its inherent features of narrow beam widths and the occurrence of oxygen absorption over fairly short relative distance.

With unlicensed wireless bridges it can never be guaranteed that the wireless link will operate interference free and with any predictable reliability. Many manufactured wireless backhaul systems can help overcome interference by having a good carrier to interference ratio inherent with the hardware and by proper RF path design and wireless installation. Prior to deploying an outdoor unlicensed wireless backhaul a wireless spectrum analysis should be performed. A wireless installation company should use a proper Spectrum Analyzer to evaluate the amount of potential interfering signals in the desired frequency that is to be used (e.g. if you are deploying a 5.8GHz wireless backhaul system, as defined by the U-NII radio band of 5.725 to 5.825GHz, you would want to capture the amount of potential interference and the source of any particular wireless interference on any given channel in the 5.8GHz spectrum that will be used). A spectrum analysis will only show the amount of potential interference on the date it was taken. Other unlicensed wireless systems may be deployed at a later date that can introduce newer wireless interference.

Wireless Spectrum Analysis

Safe guards to help avoid or overcome unwanted wireless interference can be taken by choosing the appropriate wireless backhaul hardware. Using directional antennas can narrow the wireless signal's beam width, which in turn also narrows the amount listening area, while providing overall higher system gain. Using different polarizations (e.g. vertical vs. horizontal). Many of today's wireless radio systems have the ability to utilize iDFS (intelligent Dynamic Frequency Selection) that allows the wireless radio system to optimize by choosing the best wireless backhaul channel to operate on. Newer wireless bridge systems can also take advantage of using OFDM and MIMO that can help overcome interference.

Best practices should always be used by consulting an experienced outdoor wireless integrator who can perform proper spectrum analysis, path engineering and path calculations, consult on which manufacturer's equipment would be best for the solution, and perform proper wireless installation.


Tags: General, Un-lincesed Wireless, Wireless 101

Licensed Microwave Wireless Backhaul

Posted by Joe Wargo on Wed, Apr 14, 2010 @ 03:34 PM

Licensed microwave wireless backhaul is also known as fixed wireless backhaul. A microwave link is a point to point wireless bridge or a point to multipoint wireless bridge used for wireless Ethernet backhaul. Microwave backhaul is becoming more popular for wireless Ethernet bridge applications as a result of noise interference in unlicensed wireless spectrum (U-NII Band).

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 wireless Ethernet bridge systems operate in the SHF (Super High Frequency with frequencies between 3GHz to 30GHz) and the EHF bands. Typical licensed microwave link frequencies used for wireless backhaul operate within 3.65GHz WiMax (as a point to multipoint wireless backhaul), 4.9GHz public Safety, 6GHz, 11GHz, 18GHz, 23GHz bands and the 80GHz millimeter wave E-band.  Microwave link example

For example: a licensed microwave point to point wireless Ethernet bridge that operates in 23GHz band will have a licensed frequency channel to transmit on and a channel to receive on. One end of the wireless link being channelized on the low end of the 23GHz band and the other end of the wireless link channelized on the high end of the 23GHz band.

Licensed Microwave link

To operate a licensed microwave wireless radio system one must obtain a license from the FCC by performing frequency coordination, filing a public notice (PCN), and submitting an application (601 form) with the FCC. This process is to ensure that no one else is already operating on the same frequency or a frequency that will inject interference on existing systems. Getting a license to operate a microwave link is inexpensive and can be obtained in the matter of weeks. Licensed microwave link operators are permitted exclusive use of part of the band on a particular azimuth over an assigned geographic area. If licensed radios encounter interference, it is typically resolved with the assistance of the regulatory body.

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). Licensed microwave backhaul radios provide security from the risk of interference from other RF systems. Interference can degrade a radio system's performance and in some cases even prevent the system from functioning at all. Licensed microwave wireless systems can be engineered to provide predictable reliability of 99.999% uptime.

Licensed microwave wireless radio systems are typically built and designed for long term solutions. The wireless bridge hardware is designed to provide carrier grade performance (high bandwidth and low latency). Unlike many of the Atheros (Wi-Fi) chipset based wireless Ethernet bridge systems many use, licensed microwave link systems use actual transceivers and receivers hardware that do not have high IP packet overhead. 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 radios that use OFDM or MIMO take advantage of multipath for their connectivity.

Prior to considering a licensed microwave backhaul a wireless site survey and a proper wireless path calculation should be performed. As with any point to point wireless backhaul system a certified expert should perform the wireless installation. When an organization needs a carrier grade network connection where fiber is not an option or is too expensive, a point to point wireless licensed microwave link is a cost effective solution.

Tags: Point to Point Wireless, Licensed wireless, General, Wireless 101

Point to Multipoint Wireless Ethernet Bridge

Posted by Joe Wargo on Sat, Apr 03, 2010 @ 04:21 PM

Outdoor point to multipoint wireless Ethernet bridge systems are flexible, economical, and easily deployed wireless backhaul solutions for connecting multiple remote sites to a network. Point to multipoint wireless backhaul is an ideal wireless last mile solution for interconnecting campus buildings, remote facilities, security systems, access control systems, IP video surveillance cameras, SCADA PLC's, or WISP applications as a DSL replacement. Point to multipoint wireless can also be used to backhaul wireless mesh networks. Theycan also be used to eliminate telco dependancy or to provide wireless network redundancy.

point to multipoint wirelessPoint to multipoint wireless Ethernet bridge systems are made up of a Base Station Unit (BSU or AP) that can communicate with multiple Subscriber Units (SU's). Many systems can handle over 100 plus SU's per BSU. In most cases the BSU's provide a sector antenna beam pattern (typical is 60 degree, with some systems allowing external antenna configurations for expanding to 90 and 120 degree sector antennas). Multiple BSU's can be installed to create a 360 degree sector (like a typical cell site configuration). 

Point to multipoint wireless Ethernet bridge systems can operate in the unlicensed wireless spectrum (900MHz, 2.4Ghz, 5.3GHz, 5.4GHz, or 5.8GHz), the 3.65GHz WiMax spectrum,  or in the 4.9GHz public safety band. There are propriatery point to multipoint wireless backhaul systems operated by various telecommunication providers that operate in the lincensed microwave wireless spectrums.

Point to multipoint wireless backhauls is generally used where bandwidth requirements are generally low, such as a DSL or T1 repalcement. Recently though  many point to multipoint wireless systems have taken advantage of the Wi-Fi 802.11n chip sets and can now provide wireless bandwidth up to 300Mbps aggregate throughput. Note: the actual throughput at any given SU is determined by the number of SU's connected in the system and the network configuration.

Some of the better point to multipoint wireless systems use OFDM (Orthogonal Frequency Division Multiplexing) to provide better near and non line of sight ("NLOS") connectivity. The newer 802.11n chip set systems also take advantage of multipathing by incorporating MIMO (2x2 or 3x3) to give even better NLOS capability and higher bandwidth. The range of a point to multipoint wireless backhaul can extend as far as 10 miles with clear line of sight ("LOS"), by using high gain directional antennas connected to the SU's. The optimum performance though of most point to multipoint wireless is in the 1 to 2 mile max range. NLOS applications need to be closer to the BSU / AP in order to have adequate system gain. 

There are a lot of manufactures that offer point to multipoint wireless Ethernet bridges. Some manufactures have been in the point to multipoint wireless arena for many years. Proxim with their Tsunami MP.11 series (5054-R which is a tri-band 5.3GHz, 5.4GHz, or 5.8GHz system, MP.16  that is a 3.3GHz, 3.5GHz, or 3.65GHz licensed WiMax system, and their newer high bandwidth MP8100 series), Motorola with their Canopy wireless (their newest is their Canopy 400 series that operates in the 5.4Ghz and the PtMP320 WiMax), and others such as: Alvarion, Firetide, Trango, Solectek and BelAir. Some of the newer players include FluidMesh (which specializes in wireless video backhaul and wireless mesh), Ubiquiti,and InscapeData.

When designing a point to multipoint wireless Ethernet bridge system it is highly recommended to perform a wireless site survey and a spectrum analysis. All systems regardless of how good they are have their limitations. The biggest source of failure we come across is unrealistic expectations of performance. Any organization thinking of deploying a point to multipoint wireless system should consult a professional wireless integration company that has a lot of experience designing and performing outdoor wireless installation

Tags: Licensed wireless, General, Un-lincesed Wireless, Wireless Industry, wireless video, Wireless 101

Point to Point Wireless Ethernet Bridge

Posted by Joe Wargo on Wed, Mar 31, 2010 @ 02:30 PM

Point to point wireless Ethernet bridges, also known as fixed wireless backhaul, are becoming extremely popular among organizations across all vertical markets. Once used only by the large telecommunication companies, wireless Ethernet bridges are being implemented by everyone, from federal, state, county, and local governments, utilities, health care organizations, agricultural industries, and even the private commercial sectors. 

Bridgewave Proxim wireless Ethernet bridge Wireless backhaul is an ideal complement or complete replacement to leased lines and fiber. Whether the requirement is to link the data and voice networks between individual buildings or link networks across large distances, organizations are increasingly turning to point to point wireless networks, both licensed microwave links and unlicensed wireless backhaul, as the preferred solution. Point to point wireless backhaul provides several advantages over leased lines:

  • Increased Bandwidth - With all the applications that are now driven across the network, IT departments are requiring more bandwidth across their network infrastructure. An outdoor wireless Ethernet bridge can provide true Ethernet throughput up to GigE Full Duplex (using gigabit wireless links).
  • Lower cost of installation and no recurring costs - Probably the number one driver for turning to outdoor wireless backhaul is the tremendous ROI point to point wireless bridges provide. On a 100Mbps Full Duplex wireless backhaul link the typical ROI is about 3 months. This is compared to a leased  DS3 at 45Mbps. So you can get over double the throughput and eliminate any reoccuring operational costs almost immediately. The wireless cost reduction savings can be even greater when compared o the cost of installing fiber networks.
  • Last mile connections - In many cases, organizations such as government or utilities who maintain multiple sites, just can't get their required bandwidth out to remote locations. Sometimes the best a local telco can provide is a T1. Point to point wireless can reach up to 50+ miles (if designed and installed properly). Where once you could only get a T1 circuit, you can now get 100Mbps Full Duplex up to GigE  (gigabit wireless) throughput, better known as wireless last mile.
  • Quick installation- A typical point to point wireless backhaul can be installed in a couple days. I always recommend using industry professionals that have a lot of experience (see my article "Wireless Installtion Done Properly").We've talked to a lot of clients that have waited over 6 months to have their telco provision a simple circuit. This is especially true when compared to fiber installations that can takes years to gain right away access and time it takes to trench conduit paths.
  • Reliability - Wireless backhauls designed and installed properly can provide 99.999% predictable reliability (see my article "Is Wireless Reliable"). Most telco's only provide a SLA of 99.9% uptime. In many cases where a client has installed wireless backhaul, like licensed microwave or millimeter wave gigabit wireless, for fiber redundancy we have seen the client actually convert over to using the wireless point to point backhaul as their primary and down grade their fiber connection as their redundancy. This is because the wireless backhaul typically provides a more direct path (less routing in the case of leased circuits) and is cheaper to maintain.

Point to point wireless Ethernet bridges can be used by any organization that has more than one facility that they need to connect to. There is a multitude of products in the market, both licensed microwave links and unlicensed wireless Ethernet bridges, that can solve many connectivity issues. Th price of wireless backhaul has come way down in price and is more affordable than ever. The quality of outdoor wireless backhaul is better than most other methods of connectivity.

The main reason more organizations haven't turned to outdoor wireless backhaul is either it is just not feasible do to their locations or a lack of education on what can be done with today's technology. The first step is to get a Feasibility Study by a qualified outdoor wireless vendor. A good wireless integrator can outline the best solution and the cost benefits.

Tags: Licensed wireless, General, Un-lincesed Wireless, Wireless Industry, Wireless 101

Outdoor Wireless Installation Done Properly

Posted by Joe Wargo on Sun, Mar 28, 2010 @ 04:39 PM

Proper outdoor wireless installation is the most important element of a wireless backhaul system. Over the past decade I have troubleshot hundred's of wireless backhaul networks and 95% of the issues I have seen are due to improper wireless installation.

Many would argue that choosing the right outdoor wireless bridge equipment is the most important. I would agree that there are both good and bad outdoor wireless backhaul equipment on the market, but for the most part the majority of wireless backhaul manufactures build pretty reliable radio hardware. The biggest difference comes between Carrier/Enterprise grade (higher end, low latency, microwave equipment that typically have a 20+ year shelf life) and Value Line equipment (typically under $5K and using 802.11b/g/a/n chip sets). 

Others would say that proper wireless network design and choosing the right technology, e.g. licensed microwave links or unlicensed wireless backhaul systems, is the most important. There are pluses and minuses with both systems, such as: potential wireless interference on unlicensed wireless backhaul systems or the need for clear line-of-sight with a licensed microwave link. Both systems if installed properly can provide reliable networks. Proper wireless engineering will produce the optimum  wireless network design using the appropriate equipment.

Even with the best wireless network design and best outdoor wireless backhaul equipment on the market, improper wireless installation will prevent a wireless backhual network from truly working to its potential. Many times we hear clients say the system worked fine when it was first installed but it has degraded over time. This can be caused by many issue. There was no interference when the system was first installed. Trees or other obstructions are now in the path, either creating a complete Fresnel Zone blockage or partial encroachment on the first Fresnel Zone. Antennas could have come out of alignment. Cabling and connectors could be weathered or damaged. The list goes on. Just like a race car, it must be built properly and maintenanced to work optimally. 

Many outdoor wireless bridge systems we troubleshoot lack proper materials for cabling, mounting, and weather proofing. Over time these systems get effected by the weather and slowly degrade. Systems that are not weather proofed correctly can get damaged over time by water getting into the connections or cabling. Improper mounting can cause antenna systems to come out of alignment. Systems installed with out the proper amount of fade margin can also have periodic issues with weather (see my article "Does Weather Effect Wireless").

Wireless backhaul, whether you are talking about wireless mesh, WiMax, point to multipont wireless, or point to point wireless backhaul, systems can function with extreme reliability and predictability if installed correctly. 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 we see is organizations that are willing to rely on wireless technology for their primary connectivity but pinch pennies by choosing the cheapest and many times least experienced installation companies. Worst is when a manufacture convinces and end user with little to no experience installing an outdoor wireless bridge that they can do it themselves.


Wireless Installation Tower climber


The best wireless installers are those that have a lot of tower installation experience. They typically install systems to last for many years. They also don't want to lose revenue having to come back and climb a tower again to repair a bad installation. Even though many of the outdoor wireless systems seem straight forward or easy to install based on the manufactures operation manual, the fact remains that outdoor wireless installation is a skilled trade and best performed by professionals with years of experience. You can change the oil in your high end sports car but that doesn't mean you should!


Tags: Licensed wireless, General, Un-lincesed Wireless, Wireless Industry, Wireless 101