By Masood Shariff, CommScope
Wireless networking technology in the enterprise requires cabling, and there are several solutions offered by wireless networking vendors. Which one makes the most sense? In this article we’ll look at the pros and cons of coaxial cabling, optical cabling, and Category 6 or Category 6A cabling for wireless networking.
Which wireless?
In many cases, the choice of cabling will be dictated by the type of wireless system being deployed. Enterprise WiFi systems typically use balanced twisted-pair cabling such as Category 6 or Category 6A, while distributed antenna systems (DAS) for mobile phone coverage can use coaxial cabling, Category 6/6A, or fiber. Small cells are another option for mobile phone coverage in smaller (less than 50,000 square feet) enterprise buildings, and these connect with Category 5e or fiber.
While it seems beneficial to integrate these disparate wireless solutions on one network with a common cabling infrastructure like Category 6/6A or fiber, or even on the same network as the one used for data in the enterprise, such integration is complicated for many reasons, some of which are discussed below.
Disparate antenna placements - WiFi, DAS, and small cell networks may have different placement maps for access points. For example, a typical WiFi system might have access points laid out in a grid with cells 18 meters wide, while a high-power DAS might have antennas located in cells that can be up to 200 or more meters wide. Even low-power DAS antennas may have much larger coverage areas than wireless access points (WAPs), though in the 5-GHz band, the difference is not that significant. Readers should refer to TIA TSB-162-A for more details, and look for TIA TSB-5018, which has been approved for publication.
Different protocols - Legacy WiFi uses CSMA/CA protocol, while DAS uses digitized RF, and small cells use IP/Ethernet packet data. Running multiple protocols over the same cabling infrastructure is complicated but possible.
Low-power digital DAS and small cell technology use structured cabling. Currently, high-power digital DAS uses coaxial cabling. On the network switch level, there are several factors influencing the choice of cabling. First, it depends on the technology used. Some small cell systems use the same Ethernet switch as IT. So running on the same IT Ethernet LAN is possible using VLAN protocol. However, since the operator owns the cellular frequency band, operator agreement is required especially for maintenance purposes. Other technologies such as digital DAS and remote radio head (RRH) do not use Ethernet switches even though the equipment has Ethernet ports. So running over the same IT Ethernet LAN is not possible except where a bypass card is provided.
Requirements for enterprise cabling
Wireless or not, network managers consider several factors when selecting cabling systems within an enterprise, including suitability for the application, cost, familiarity, and longevity.
Application suitability - Naturally, the cabling system should support the wireless application. As wireless LANs move to 802.11ac (with a top data rate of 6.9 gigabits per second) and DAS platforms move to carrying 4G, and eventually 5G, traffic at up to 10 Gbits/sec and possibly more, network managers will need cabling that can handle these higher data rates. For twisted pair, the industry is rapidly converging on Category 6A cabling as the most suitable media to support wireless access points.
Cost - Twisted-pair (copper) cabling systems are lower cost than equivalent fiber systems when the associated active equipment and installation costs are also included in the cost comparison. The cost of the fiber cabling or twisted-pair cabling alone is comparable but installation labor rates are higher for fiber systems. Overall, there is a significant cost premium for fiber solutions over copper solutions.
Familiarity - Enterprise IT managers are very familiar with using twisted-pair cabling systems and the introduction of coaxial cabling systems to support wireless systems complicates design, support and maintenance processes.
Longevity - Generally speaking, IT managers should put in the best cabling systems on day one. Cabling infrastructure has multi-generational utility; they can support today’s applications as well as the next one or two generations forward. Using Category 6A and fiber allows IT managers to provision for the future needs of wireless applications and migrate upwards without ripping and replacing cabling infrastructure.
Cabling systems compared
Since fiber and Category 6/6A are the two cabling types that meet all enterprise buying criteria, we will focus on these and compare their capabilities.
Category 6 cabling provides performance of up to 250 MHz over distances of up to 100 meters. For the 100-meter maximum channel distance specified in standards, Category 6 cabling can support Ethernet speeds up to 1 Gbit/sec. Although it can also support the emerging 2.5-Gbit/sec and 5-Gbit/sec Ethernet speeds, because it lacks alien-crosstalk specification, some use cases may not be supported or may be distance-limited.
Category 6A cabling delivers performance of up to 500 MHz over distances of up to 100 meters. For the 100-meter maximum channel distance specified in standards, Category 6A cabling is the media of choice in new installations to support Ethernet speeds higher than 1 Gbit/sec, including full support of 2.5 Gbits/sec, 5 Gbits/sec and 10 Gbits/sec.
Both Category 6 and Category 6A use standard RJ-45 connectors and support Power over Ethernet (PoE), which delivers 13 or 25 (PoE Plus) watts of power over 100 meters. Many WAPs can be powered this way, eliminating the necessity of providing a local power source at each WAP location. Some small cells also use PoE. When supporting PoE, Category 6A is often preferred due to the lower temperature rise in cable bundles.
Multimode fiber is typically used for the backbone cabling in wireless network deployments in enterprises, as it supports run lengths of up to 550 meters. Newer deployments often use laser-optimized 50/125-micron multimode fiber (Om3 or Om4). Fibers that meet this designation provide sufficient bandwidth to support 10-Gigabit Ethernet up to 300 meters for Om3 and up to 400 meters for Om4. When using multimode fiber to the WAP, power for the WAP, small cell or distributed antenna unit must be provided separately.
Masood Shariff is a senior principal engineer in the systems engineering group of CommScope (www.commscope.com). He represents CommScope in the ISO WG3 committee, as well as several TIA TR-42 subcommittees. He served as chair of TR-42.7 for many years. Currently he serves as chair of the committee revising TSB-162, covering cabling guidelines for wireless access points; and as chair of the committee that developed the TIA-5016 Physical Network Security standard.