Alpha Omega Wireless Blog

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

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

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

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

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

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

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

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.

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.

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. 

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.

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.

Wireless mesh networks, as a wireless backhaul technology, provide scalability, redundancy and reliability. Fixed wireless mesh can be deployed on existing infrastructure, such as: buildings, traffic signals, and light poles, saving a lot of capital expenditures on the costs of mounting structures. Most outdoor wireless bridge radios that support wireless mesh networking operate in unlicensed wireless bands of 2.4GHz, 5.3GHz, 5.4GHz, 5.8GHz, or the 4.9GHz Public Safety band. There are several really good manufactures of wireless mesh equipment (Firetide, Proxim Wireless, FluidMesh, Azalea Networks, etc.).

In a wireless mesh network, outdoor wireless bridge links are made up of a wireless mesh node that can send and receive wireless backhaul IP traffic. Wireless mesh nodes can function as a router, wireless access point, or a wireless gateway device. Through the relaying process, a packet of wireless data will find its way to its destination, passing through intermediate links providing reliable wireless backhaul communication. If one mesh node can no longer operate, the other mesh nodes can still communicate with each other, directly or through one or more intermediate links. Wireless mesh nodes can communicate with one or more nodes and can determine the best wireless backhaul path to transmit its traffic or perform load balancing on the network.

Wireless mesh networks can be configured in a star topology or be made up of multiple types of configuration topologies such as: point to multipoint wireless backhaul or as a point to point wireless Ethernet bridge. Wireless mesh radios provide the ultimate flexibility from a single device.

Wireless mesh radio platforms have become a popular wireless Ethernet bridge architecture. Wireless mesh first became prevalent in the push for Municipal Wi-Fi applications by the wireless mesh manufactures and by Municipal governments trying to get notarized by offering wireless internet access to their communities. Municipal Wi-Fi was driven mostly by local politicians trying to boost their political clout with very little understanding on the actual outdoor wireless bridge technology. Many of these projects failed because of the lack of having a good business model to offer wireless internet access and in most cases little or no RF engineering was performed (wireless site survey, spectrum analysis, wireless network design, etc.). Making matters worse many manufactures were guilty of over marketing the capabilities of their products (how many wireless mesh nodes that could be deployed before having to have a backhaul to avoid high latency and maintain adequate throughput on the networks) and by not educating their clients on the of potential wireless interference when using unlicensed wireless backhaul.

Many municipal agencies consulted their hardware manufacture, which understand their equipment, but do not have actual experience in deploying outdoor wireless Ethernet bridges, nor should they. They are manufactures not wireless installation services companies. As many Municipal agencies soon found out that the cost was more than anticipated as they were told that to solve any connectivity issues they needed to just add more devices.

The wireless mesh hardware platform was not the issue. The problem was the lack of proper RF planning (performing proper wireless site survey and spectrum analysis), wireless network design, and proper wireless installation. Wireless mesh is a good topology but as with any outdoor wireless backhaul it needs to be done by experienced wireless integrators.

Recently, fixed wireless mesh has found a new niche market to serve. The growth of outdoor IP video surveillance has made wireless mesh a cost effective solution. Mesh, as an outdoor wireless bridge technology, provides the ultimate scalability and flexibility in network design. Wireless video networks can be scaled over time and wireless backhaul using mesh can allow cameras to be placed almost anywhere. Manufactures like Firetide, Proxim, and Fluidmesh were early adopters by optimizing their wireless mesh platform for video backhaul and have done a good job marketing to the IP video marketplace.

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 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. 

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. 

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.

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.

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!

This week we attended two large trade shows in Las Vegas, the ISC West (focusing on the security and video surveillance industry) and CTIA (focusing on the telecommunication carriers and mobile industry).

The CTIA obviously is all about outdoor wireless backhaul. The main focus here was 4G, LTE and WiMax. Moving more application to mobile devices was the core theme. We didn't here much about anything really new or overly exciting though. This is probably because we hear so much about the mobile marketplace on a daily basis, so there wasn't any major unknown breakthroughs here.

Over the past few years the ISC West has become a hot bed of outdoor wireless backhaul integration. The Security and Video marketplace has moved to IP technologies. This is exciting to watch a complete industry, whether you are talking about Access Control, Video Surveillance, Asset Tracking, Perimeter Detection, etc. This move to IP has been taking place over the last several years and the industry is pretty much fully there. This year there wasn't many new innovative product announcements. Probably the best new items were fully POE powered camera housings from Video Alarm, using a single 802.3af powered CAT-5e cable to power both the IP camera and the heater / blower housing. Pretty cool and very effecient. 

Most every manufacture was incorporating Wi-Fi or 900MHz into their product lines. Again, nothing amazing since other industries have been using these frequencies for years.  There were a few interesting Perimeter Detection manufactures using microwave radio technology that was very interesting. 

This year nothing gave us the WOW factor, but it was nice to see more and more wireless technologies being incorporated into other industries and applications.

The main common theme though was that we need more bandwidth utilizing wireless backhaul technologies. This is extremely important in the mobile industry where everything is moving to the handset. The one thing though that was crystal clear is the need for more support from the FCC to open up some more spectrum. Everyone is throwing RF out there everywhere trying to create broadband wireless backhaul. The unlicensed wireless spectrum are going to get over used and saturated in the near future.

Question 5: Is Wireless True Ethernet Throughput?

Answer: Yes!

Wireless point to point bridge networks can provide true usable Ethernet throughput from T1 speeds to over GigE Full Duplex (gigabit wireless). Wireless Point to Multipoint networks can provide T1 speeds up to 170Mbps+ aggregate throughput. Wireless mesh Networks can provide up to 25Mbps+ aggregate throughput. These are true usable throughputs.

Note: When evaluating wireless backhaul systems it is important to cut through all the marketing and look at the actual specifications of a chosen system. Many times we see the product marketing rounding up actual values or using the data burst rates of a radio system, rather than the actual usable data throughput.

Outdoor wireless backhaul networks can provide true low latency, high speed native  Ethernet connectivity. Think of wireless connectivity just as invisible copper or fiber. The value of wireless networks is that they can provide a more direct path of connectivity. This is true when looking at point to point wireless bridges. In the case of leased line connectivity, a clients network path may go through multiple CO's (central offices) or multiple switching locations in order to create a land line point to point network. 

A great example of this happens when some one sets up a Spanning Tree Network using wireless backhaul as a redundancy solution. Many times in this environment the network wants to converge over the outdoor wireless brdige network because it provides a more direct path (hence a lower cost average). As they say the most direct path between two points is a straight line. Also, wireless backhaul networks can have <1ms of latency, even over long distances (up to 50 miles). In most STP networks the wireless bridge network needs to be given a higher cost value in order to keep the network from automatically converging over it. Another value is that wireless point to point and point to multipoint wireless networks can provide connectivity where traditional copper or fiber cannot be installed. 

Many of the "Value Line" outdoor wireless bridge systems (e.g. the lower cost unlicensed wireless systems that use Wi-Fi chip sets) do have a distinction between the radio's data rates and the usable throughput. These radios, common among wireless mesh and point to multipoint wireless backhaul systems, do add packet headers to the IP packets that get passed across the wireless link. Commonly we see manufactures state a radio is 54Mbps, when in reality the true usable throughput is typically under 27Mbps aggregate. This is for several reasons: the radios operate in TDD (Time Division Duplexing) and they are using Wi-Fi radios that add overhead to the packet stream by encapsulating the IP packets and by sending out beacon requests.

Traditional microwave outdoor wireless backhaul systems, such as licensed microwave links, can offer true carrier grade Full Duplex (simultaneous up-link and down-link) Ethernet connectivity and can even offer traditional wayside TDM circuits. Often referred to as Carrier Grade systems, these radio systems do not carry the same overhead as Wi-Fi based radios systems. So these radio systems provide true usable Ethernet and TDM throughput. These systems can provide traditional native 100Mbps Full Duplex Ethernet connectivity or even expand up to over true GigE (Gbps) Full Duplex just like fiber.

Outdoor wireless backhaul can also provide scalable throughputs in between 10Mbps and GigE (gigabit wireless). For example, 200Mbps Full Duplex on a particular network segment which can then be spit into two 100Mbps Full Duplex segments. Wireless backhaul systems can also provide inherent security and added encryption, Layer 2 connectivity, QOS, VLAN tagging, etc.