Alpha Omega Wireless Blog

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

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

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

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

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

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

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

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

More to come in Part 2...

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

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

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

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

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

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

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

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.

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

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

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

  

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

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