Extended Reach: the Fact File

Before discussing how to solve the problem, let’s understand it a little better. Why exactly is there a 100 m limit?

The 100 m distance limitation—as codified in the industry standards (namely, ANSI/TIA-568, ISO 11801 and other cabling standards for commercial buildings)—is based on the electrical limitations of twisted-pair copper cabling. As the signal travels from one end of the cable to the other, its strength is affected by certain parameters, primarily insertion loss. The longer the cable, the greater the insertion loss. Based on these performance parameters, the industry standardized on the 100 m distance. 

The distance limitation represents a worst case scenario for a given application and length when conducting a signal at the cable’s maximum frequency. It assumes a four-connector channel using a 90 m trunk and a 5 m patch cable at either end.

The limit was standardized in the 1990s and has stood the test of time even as higher-frequency applications and new cable constructions have entered the market. In that time, network equipment vendors cost-optimized their transceivers based on the 100 m limit—further solidifying it as the accepted distance boundary. 

Why have just one standard for distance?

It is interesting to note that the 100 m limit applies to all cable categories—from Category 2, introduced in 1991, to Category 7A, which debuted in 2010 as a steppingstone to 40 Gbps. The capabilities of the various generations of category cabling have steadily increased, but the distance limitation has remained constant. Why not develop standards for each generation of category Ethernet? The simple answer is that using a higher category cable on the same applications extends the supportable distance by only a few meters at best. But there’s more to it than that.

Having a different standard for each cable category provides marginal benefits; not doing so, however, creates multiple opportunities. Standardizing on 100 m for all cable types provides a uniform target for manufacturers—and facility architects involved in floor planning—and eliminates the need and cost to test and certify each cable type to a different standard. Moreover, it enables customers to mix and match cabling from different manufacturers and ensures interoperability with active network equipment. 

The effect of application and environment 

While cable type has minimal effect on supportable distances, the application has a greater effect. A good example is power over Ethernet (PoE). A PoE+ (PoE type 2) application can support up to 30 watts of power over 150 m or more. The maximum distance depends on the speed required. Not counting special designs such as those requiring SYSTIMAX® GigaREACH™ (see below), the maximum horizontal distance at 10 Mbps is 185 m; at 100 Mbps it drops to 150 m. The environmental conditions such as operating temperature will also have an impact on the maximum supportable distance.

This being said, the 100 m channel limit has a significant effect on how enterprise networks are designed and deployed. Network managers must support more devices located farther from power sources and have high confidence that it will work. So, what are their options?  

Another approach is to install an in-line PoE extender between the power source equipment and device. This divides the channel into two links—one on each side of the extender. Each link can span 100 m, enabling network designers to double the length of the channel while adhering to the standards.

However, a PoE extender (a.k.a. “repeater”) is subject to the power and bandwidth limitations of the PoE technology and cable medium used. This means it still needs local power and is limited as to the number of devices it can support. A PoE extender also requires dedicated space and, without careful tracking and location documentation, management and troubleshooting can be difficult. 

A third option for delivering power and data beyond the 100 m limit is to simply use a longer twisted-pair cabling link. While this method is not supported by the cabling standards, it is possible to use the application standards in conjunction with application testing to create a reliable link. Application standards help network designers gauge whether a specific application can run on a link segment, regardless of the cabling components used and the distance traversed. 

For a more detailed analysis of this approach and the use of application standards and application  testing, check out this article from Cabling Installation & Management.

Thoroughly vetted and correctly installed, the extended twisted-pair solution supports centralized management and efficient PoE delivery while reducing the number of link components and providing familiar RJ45 connectivity and installation.

UTG infrastructure enables a range of existing and next-generation network capabilities, from standardized applications such as connecting Wi-Fi access points (APs) or IP phones, to those with needs that go beyond the standards, like extended distance, power, and cybersecurity. 

Examples of UTG applications include:

• Building environmental control automation
• Security monitoring and surveillance
• Digital signage systems
• Enhanced PoE applications
• IoT devices and sensors
• Wi-Fi APs
• VoIP devices 

It will take time for the standards bodies to catch up to the extended-reach performance of the UTG infrastructure platform. Therefore, CommScope has worked alongside Anixter, UL and other third-party technology experts to validate all performance claims. These efforts have resulted in UTG-specific performance standards and UTG-rated infrastructure cabling solutions. Together, they support diverse applications, systems and devices on a common network.

All performance claims and UTG ratings are independently tested and verified by UL laboratories for optimal application assurance and design on a single building platform. The results are based on real-world, definitive application testing and UTG-exclusive testing protocols. Based on UL’s testing, CommScope’s UTG solutions outperform non-UTG cabling.

Customers deploying UTG infrastructure solutions enjoy a similar level of application support available through CommScope’s SYSTIMAX Application Assurance program. This support provides the design capabilities and performance helps building owners and enterprises need to migrate with confidence. In fact, the UTG program is highly complementary with the SYSTIMAX Application Assurance program, and we believe we can build on it to extend beyond what we currently support.  

CommScope continues to focus on innovation and continual improvement, investing almost $200 million in R&D, including investments in our SYSTIMAX solutions. These investments, combined with a UL verification program to validate emerging and enhanced technologies, give our customers the satisfaction of knowing their CommScope products and solutions are indeed best-in-class. 

 

For more information on CommScope’s UTG infrastructure portfolio:

Application guide: Utility grade infrastructure (UTG)

Brochure: Utility grade infrastructure solutions

Insertion loss (attenuation)—the reduction in the electrical signal strength as it propagates along the transmission path—is present in all media types. It determines the maximum distance over which a transmitted signal can be resolved and, therefore, the maximum distance two devices can be separated while maintaining communication.

Usually expressed in decibels per unit length (e.g., dB/1,000 feet), insertion loss is a measure of how much the signal’s amplitude is weakened or reduced in amplitude as the signal traverses the cable. It also increases as the cable’s operating temperature increases.

In a copper wire, insertion loss is caused by two main factors:

Copper loss is related to the thickness of the cable’s copper conductor; the thicker the conductor, the lower the insertion loss. While you can reduce insertion loss by increasing the conductor size, that would increase cabling costs and reduce your options for properly mating the conductor to the right jacks and/or plugs. In reality, an oversized conductor is unnecessary for the vast majority of installations that are less than 100 m in length.

Dielectric loss (dissipation) is related to the electrically lossy properties of the cable’s insulation and jacketing. The choice of these materials impacts insertion loss and the cable’s performance during safety tests such as those that characterize flammability and smoke release. Tradeoffs between electrical and safety performance often dictate the materials needed, which can complicate compliance with regional safety standards such as those for plenum-rated and low-smoke-zero-halogen (LSZH) rated environments.

It’s important to note that there are other factors, such as resistance and heat, that can influence insertion loss. For example, the maximum allowed insertion loss for Category 6A (at 500 MHz) is 42.8 dB, compared to Category 6 (at 250 MHz), which is 31.1 dB. This is also why links involving smaller-gauge wires with more resistance—and where the ambient temperature is above 20°C (68°F)—can require length de-rating. The higher the insertion loss, the shorter the reach must be for a signal at the far end of the link to be understandable. This is a key reason why insertion loss has such an important impact on the supported distance.

Propagation delay is the time needed for a signal initiated at one end of the channel to be received at the opposite end. In twisted-pair cabling, this time interval is impacted by the cable’s length and operating frequency (previously discussed) as well as a third factor: nominal velocity of propagation (NVP). NVP is a relative measure of the signal’s speed compared to the speed of light in a vacuum (c). Typical structured wiring cables exhibit an NVP of 0.6 c to 0.9 c, meaning the signal travels at 60–90% the speed of light in a vacuum.

A cable’s maximum NVP is dictated, in part, by physical characteristics such as the number and tightness of twists in a pair of strands. As the number of twisted pairs in a cable bundle increases, the chances of disparities in the twists among pairs also increase. The difference in propagation speeds between the fastest and slowest pairs is known as the “propagation delay skew.” As propagation delay skew grows, the more difficulty the network equipment has in reading the signal. Extended cable lengths can exacerbate this issue.   

When we compare the different categories’ performances in light of the aforementioned parameters, it’s easy to understand the advantage of Cat 6A when we need to go farther than the standard 100 m:

• At 100 MHz, Category 5e has an insertion loss maximum of 24 dB, while Category 6 is at 21.3 and Category 6A is at 20.9 (per TIA channel specifications). Remember: The lower the dB for insertion loss, the better.  
• Common 6A cable and cordage gauge is larger (thicker) than for other categories, which improves insertion loss, resistance and SNR parameters.
• Cable heating is lower for 6A when transmitting the same current and wattage for PoE purposes, which makes possible larger cable bundles.
• As previously mentioned, first-class 6A solutions are carefully tuned up to provide lower signal reflection.
• All of the above advantages, combined with the inherently superior performance for alien crosstalk, make Cat 6A the perfect choice.