Alpha Omega Wireless Blog

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.

Over the years manufactures in the outdoor wireless bridge industry have migrated their designs of radio systems. In the past, most radios used in Point to Point microwave wireless were comprised of radio units that were mounted indoors. These radios hardware platforms required radios that were rack mounted indoors and had to use large coax (1/2" to 2 1/4" Heliax or LMR) or Elliptical Waveguide (requiring dehydrators) running out from the indoor radio unit up the tower (or to the roof top), connecting the antenna.

Because of the large amount of line loss, large cable or waveguide had to be used to compensate for the amount of line loss between the radio and the antenna (typical 6.1dB per 100ft with standard LDF 4-50 1/2" Heliax). To compensate for the line loss larger antennas also needed to be used in conjunction of the larger cable.

The advantages of this type of wireless backhaul radio system is that a technician can walk into a data room/closet or outdoor radio shelter to service the radio or replace it in event of a radio failure. But there are a lot of disadvantages with this set up:

1. The larger the cable/waveguide and antennas, the greater the cost of the overall system.
2. Less over gain of the radio system due to the line loss.
3. Greater infrastructure needed to support the loading of the larger antennas and cabling on the tower and/or mounts.
4. Costs with maintaining an in facility.
5. These types of radio systems typically have greater power consumption.
6. More points of failure to troubleshoot (dehydrators, couplers, cable, etc.)
   

The industry later came out with a split mount design radio system consisting of an indoor modem unit ("IDU" - typically a 1U rack mounted piece of hardware) and an outdoor RF Unit ("ODU") that mounts the actual radio RF component hardware directly onto the back of the antenna. This system typically uses a smaller IF (intermediate feed) coax cable to pass DC power and the data between the ODU to the IDU. The IF cable can be 1/2" coax or less. The advantages of this type of system are greater system gain (with virtually no loss between the radio and the antenna) and lower costs of system components (less cabling and no need for expensive waveguide or dehydrators). Still many of the same disadvantages still apply with the need for indoor space requirements and costlier power consumption.

Today the industry has migrated to full outdoor radio unit systems (FODU") comprised of a single outdoor unit mounted to the back of the antenna. These FODU's contain the RF components, modems, and network interface. The connection between the FODU and the network switch is typically outdoor shielded twisted pair (CAT-5e) or fiber. The FODU design has far greater advantages over the indoor radio or IDU+ODU spit mount designs:

1. FODU's consume a minimum of 20% less energy (typically use 25W to 30W DC).
2. Systems can be powered by solar or battery.
   
3. No equipment room or rack space needed.
4. Lower over all OPEX (operational expenditure costs).
5. Higher gain to virtually no loss between radio and antenna.
   
6. No cost for expensive coax or waveguide.
7. Single component which makes for simple troubleshooting
8. Easy to spare equipment.
9. Quicker and easier install and maintenance.
10. Easy to daisy chain radios at repeater sites or for dual radio set ups (1+1)
    

The argument that comes up with individuals that are use to the older way systems were designed is the fear of everything being up on the tower and not being able to service it. Most end-users are not tower certified and can't do their own servicing. In roof top applications this is a non-issue but it is true in a tower situation. But even with all indoor radio systems there is still the need for tower services for troubleshooting because the large number of potential points of failure of the system components that reside on the tower (e.g. the coax/waveguide, couplers, connectors, weather proofing, surge protection, antenna, etc.).

Troubleshooting an all indoor system or split mount design can take a lot of labor and have great costs associated to it. For example:

• a bad coupler on waveguide or moisture getting into the waveguide is very difficult and time consuming to identify.
  
• The same holds true for damaged coax (coax that might have been crushed or dinged during tower work on other existing systems).
• Blown or faulty surge protection.
• Worn or improper weather proofing.

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.

When evaluating wireless backhaul technology, the possibility of radio frequency interference disrupting a wireless network link poses a concern. Radio interference results from unwanted radio frequency (RF) signals disrupting system communications. Typically these signals are at or near the same frequency as the receive frequency of an established wireless system. Interference can degrade a radio system's performance and in some cases even prevent the system from functioning at all.

The source of interference is usually other transmitters that are very close in frequency to the impacted system. Interference can affect all types of radio frequencies, although the issue of interference in regards to outdoor wireless often occurs with license-exempt ("unlicensed wireless") systems operating in the 902-928MHz (spread spectrum), 2.4GHz, 5.3GHz, 5.4GHz, and 5.8GHz frequencies. Note: 60GHz millimeter wave, often used in gigabit wireles backhaul, is considered to be unlicensed but is extremely immune to interference due to its inherent features of having narrow beam widths and oxygen absorption over fairly short relative distance.

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

Point to point wireless links can be designed and deployed in either licensed microwave or un-licensed frequencies. Point to multipoint and mesh wireless systems typically operate in the un-licensed 2.4GHz, 5.3GHz, 5.4GHz, and 5.8GHz frequency bands. Some point to multipoint wireless systems can operate in licensed UHF/VHF, 900MHz, 3.65GHz (WiMax), and 4.9GHz (public safety) frequency bands.

Note: There are licensed 2GHz bands owned by various telecommunication carriers being used for WiMax applications. The 4.9GHz public safety band is not truly a licensed band. It's a license registration that gives permission for use of the frequency among agencies that can prove that it's being used for public safety. Multiple agencies can be approved in the same operating area. The FCC states that the various agencies must self coordinate. They must work together on their operating channels to avoid interference, with each other, but provides no guaranty.

Licensed RF transmitters communicate using a specific transmit and receive frequency combination that is selected and assigned to the user (licensee). Licensed microwave wireless systems operate within parts of the radio spectrum, such as: UHF/VHF, 900MHz, 2GHz, 3.65GHz (WiMax), 4.9GHz (public safety), 6GHz, 11GHz, 18GHz, 23GHz, and 80GHz (E-Band millimeter wave) as designated by the FCC.

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

Prior to deploying and operating a licensed frequency an end user is responsible for performing a frequency coordination, filing a public notice, and submitting an application (601 form) with the FCC to ensure that no one else is already operating on the same frequency or a frequency that will inject interference on existing systems. This process provides full disclosure of the frequency assignment and typically avoids interference from any existing licensee already assigned in the area. If licensed radios encounter interference, it is typically resolved with the assistance of the regulatory body.

With un-licensed systems it can never be guaranteed that a system will operate interference free and with any predictable reliability. Many manufactured systems can help overcome interference by having a good carrier to interference ratio inherent with the hardware and by proper design and installation.

With licensed microwave systems one can have a predictable reliability because of the lack of interference. Many licensed systems can be design and installed for 99.999% predictable reliability (meaning the system is predicted to have less than 5 min of outage time a year).

The major difference between licensed wireless and license-exempt systems is that licensed radio users have a regulatory body that will assist them in overcoming any interference issues that may arise, while license-exempt users must resolve interference issues without governmental assistance.