The impact of new wireless standard on structured cabling

The newly published IEEE 802.11ac Very High Throughput wireless LAN standard has far-reaching implications with respect to cabling infrastructure design.

Users can expect their current wireless speeds to increase by switching to 802.11ac gear with 1.3 Gbps data rate capability that is available today. In addition, 256-QAM modulation, 160 MHz channel bandwidth and a maximum of eight spatial streams can theoretically deliver 6.93 Gbps in the future. For the first time, the specification of high-performance cabling supporting access layer switches and uplink connections is critical to achieving multigigabit throughput and fully supporting the capacity of next-generation wireless access points.

Key cabling design strategies to ensure that the wired network is ready to support 802.11ac wireless LANs addressed in this article include:

• Specifying category 6A or higher performing horizontal cabling in combination with link aggregation to ensure immediate support of the 1.3 Gbps theoretically achievable data rate deliverable by 802.11ac 3-stream wireless access points (WAPs) and routers available today.
• Installing a minimum of 10 Gbps capable balanced twisted pair copper or multimode optical fibre backbone to support increased 802.11ac uplink capacity.
• Utilising a grid-based zone cabling architecture to accommodate additional WAP deployments, allow for rapid reconfiguration of coverage areas and provide redundant and futureproof connections.
• Utilising a grid-based zone cabling architecture to accommodate additional WAP deployments, allow for rapid reconfiguration of coverage areas and provide redundant and futureproof connections.
• Using solid conductor cords, which exhibit better thermal stability and lower insertion loss than stranded conductor cords, for equipment connections in the ceiling or in plenum spaces where higher temperatures are likely to be encountered.
• Recognising that deploying Type 2 PoE to remotely power 802.11ac wireless access points can cause heat to build up in cable bundles:
  - Shielded systems are more thermally stable and support longer channel lengths (ie, less length de-rating is required at elevated temperatures to satisfy TIA and ISO/IEC insertion loss requirements) when deployed in high-temperature environments.
  - A larger number of shielded cables may be bundled without concern for excessive heat build-up within the bundle.
  - Siemon’s shielded class EA/category 6A and class FA/ category 7A cabling systems inherently exhibit good heat dissipation and are qualified for mechanical reliability up to 75°C, which enables support of the Type 2 PoE application over the entire operating temperature range of -20 to 60°C.
• Specifying IEC 60512-99-001-compliant connecting hardware ensures that contact seating surfaces are not damaged when plugs and jacks are unmated under 802.11ac remote powering current loads.

What’s in a name?

The latest 802.11ac wireless LAN technology goes by many names, including:

• 5 GHz Wi-Fi - for the transmit frequency.
• Gigabit Wi-Fi - for the short-range data rate of today’s three spatial stream implementation.
• 5G Wi-Fi - for 5th generation (ie, 802.11a, 802.11b, 802.11g, 802.11n, and 802.11ac).
• Very high throughput Wi-Fi - from the title of the application standard.

No matter what you call it, the fact is that the increasing presence and capacity of mobile and handheld devices, the evolution of information content from text to streaming video and multimedia, combined with limits on cellular data plans that encourage users to ‘off-load’ to Wi-Fi are all driving the need for faster Wi-Fi networks.

As Wi-Fi becomes the access media of choice, faster wireless LAN equipment will play an important role in minimising bottlenecks and congestion, increasing capacity and reducing latency, but only if the cabling and equipment connections can support the additional bandwidth required. The Wi-Fi Alliance certified the first wave of production-ready 802.11ac hardware in June 2013 and adoption of 802.11ac is anticipated to occur more rapidly than any of its 802.11 predecessors. Today, 802.11ac routers, gateways and adapters are widely available to support a range of 802.11ac-ready laptops, tablets and smartphones. In fact, sales of 802.11ac devices are predicted to cross the 1 billion mark (to total 40% of the entire Wi-Fi enabled device market) by the end of 2015.

A technology evolution

The enhanced throughput of 802.11ac devices is facilitated by an evolution of existing and proven 802.11n Wi-Fi communication algorithms. Like 802.11n, 802.11ac wireless transmission utilises the techniques of beamforming to concentrate signals and transmitting over multiple send and receive antennas to improve communication and minimise interference (often referred to as multiple input, multiple output or MIMO). The signal associated with one transmit and one receive antenna is called a spatial stream and the ability to support multiple spatial streams is a feature of both 802.11ac and 802.11n. Enhanced modulation, wider channel spectrum and twice as many spatial streams are the three key technology enablers that support faster 802.11ac transmission rates while ensuring backward compatibility with older Wi-Fi technology.

802.11ac devices will transmit exclusively in the less crowded 5 GHz spectrum. This spectrum supports higher transmission rates because of more available non-overlapping radio channels. It is considered ‘cleaner’ because there are fewer devices operating in the spectrum and less potential for interference. One disadvantage of operating in this spectrum is that 5 GHz signals have a shorter transmission range and have more difficulty penetrating building materials than 2.4 GHz signals. Designing a flexible cabling infrastructure that can accommodate the addition of future WAPs and enable rapid reconfiguration of coverage areas can save headaches later. Figure 2 depicts a recommended zone cabling approach utilising enclosures that house consolidation points (CPs) with spare port capacity to facilitate connections to equipment outlets (EOs) that are positioned in a grid pattern.

In addition, because most WAPs are located in the ceiling or in plenum spaces where higher temperatures are likely to be encountered, the use of solid conductor cords that exhibit better thermal stability and lower insertion loss than stranded conductor cords is recommended for all equipment connections in high-temperature environments. Refer to ISO/IEC 24704 and TIA TSB-162-A for additional design and installation guidelines describing a grid-based cabling approach that maximises WAP placement and reconfiguration flexibility.

The implications of speed

In 802.11n and 802.11ac, channels that are 20 MHz wide are aggregated to create the ‘pipe’ or ‘highway’ for wireless transmission. 802.11ac technology allows radio transmission over either four or eight bonded 20 MHz channels supporting maximum throughput of 433 and 866 Mbps, respectively. In addition, 802.11ac can accommodate up to eight antennas and their associated spatial streams for an unprecedented maximum theoretical data speed of 6.93 Gbps.

Note that, unlike full duplex balanced twisted-pair BASE-T type Ethernet transmission where throughput is fixed in both the transmit and receive orientations, the speed specified for wireless applications represents the sum of upstream and downstream traffic combined.

Figure 1: Example grid-based WAP zone cabling deployment design.

Because of the variables of channel bandwidth and number of spatial streams, 802.11ac deployments are highly configurable. In general, the lower end of the throughput range will be targeted for small handheld devices with limited battery capacity such as smartphones; the middle of the throughput range will be targeted towards laptops; and the highest end of the throughput range will be targeted at specialised and outdoor applications where there is less device density compared with indoors.

Wireless LAN provider Aruba Networks suggests that manufacturers will leapfrog 4-stream 802.11n products in favour of 802.11ac products. The bottom line is that end users can reasonably expect their current wireless speeds to at least double by switching to 802.11ac gear that is available today and more than quadruple when second wave products become available.

When comparing wireless capabilities, it is important to keep in mind that the maximum realisable data rate is impacted by the number of wireless users, protocol overhead and the spatial distribution of end-user devices from the access point.

Transfer data collected for first-generation wireless products confirms that the 802.11ac 3-stream data rate at relatively close range to a single device is roughly on par with that achievable with a wired Gigabit Ethernet (1000BASE-T) link. In some cases, the 802.11ac wireless data transfer rate was fast enough to saturate the 1000BASE-T copper balanced twisted-pair cabling link provided between the 802.11ac router and the server.

Greater than 1 Gbps wireless data rate capability has serious implications related to wired media selection for router to server and other uplink connections. For example, two 1000BASE-T connections may be required to support a single 802.11ac WAP (this is often referred to as link aggregation) if 10GBASE-T uplink capacity is not supported by existing equipment (refer to Figure 1, which depicts two horizontal link connections to each equipment outlet). As 802.11ac equipment matures to support 2.6 Gbps and even higher data rates, 10 Gbps uplink capacity will become even more critical. Moreover, access layer switches supporting 802.11ac deployments must have a minimum of 10 Gbps uplink capacity to the core of the network in order to sufficiently accommodate multiple WAPs.

Power consumption

Although 802.11ac radio chips are more efficient than prior generation wireless chips, they are doing significantly more complex signal processing and the amount of power required to energise 802.11ac devices is higher than for any previous 802.11 implementation. In fact, 802.11ac WAPs are unable to work within the 13 W budget of Type 1 Power over Ethernet (PoE) and must be supported by either a direct DC power adapter or 30 W Type 2 PoE remote power. (Note that some 802.11ac products may be able to draw power from two Type 1 PoE connections, but this is an impractical and fairly uncommon implementation.) While safe for humans, Type 2 PoE remote power delivery, at an applied current of 600 mA per pair, can produce up to 10°C temperature rise in cable bundles and create electrical arcing that can damage connector contacts. Heat rise within bundles has the potential to cause bit errors because insertion loss is directly proportional to temperature. In extreme environments, temperature rise and contact arcing can cause irreversible damage to cable and connectors. Fortunately, the proper selection of network cabling, as described next, can eliminate these risks.

The wired infrastructure

Existing wireless access devices, client devices and the back-end network and cabling infrastructure may need to be upgraded in order to fully support 802.11ac and Type 2 power delivery. In addition, 802.11ac’s 5 GHz transmission band requires relatively dense WAP coverage areas and existing 802.11n grid placement layouts may not be sufficient. For both new and existing wireless deployments, now is the time to seriously consider the wired cabling uplink infrastructure.

Under all circumstances, the equipment outlets, patch panels and other connecting hardware used in the channel should comply with IEC 60512-99-001 to ensure that critical contact seating surfaces are not damaged when plugs and jacks are unmated under 802.11ac remote powering current loads.

Designing a cabling infrastructure to robustly support 802.11ac deployment requires consideration of the switch, server and device connection speeds commonly available today as well as strategies to support redundancy, equipment upgrades and future wireless technologies. A grid-based category 6A zone cabling approach using consolidation points housed in zone enclosures is an ideal way to provide sufficient spare port density to support 1000BASE-T link aggregation to each 802.11ac WAP as necessary, while also allowing for more efficient port utilisation when 10GBASE-T equipment connections become available. Zone cabling is highly flexible and enables rapid reconfiguration of coverage areas and conveniently provides additional capacity to accommodate next-generation technology, which may require 10GBASE-T link aggregation. Additional WAPs can be easily incorporated into the wireless network to enhance coverage with minimal disruption when spare connection points in a zone cabling system are available. This architecture is especially suited to deployment in financial, medical and other critical data-intensive environments because redundant 10GBASE-T data and backup power connections provided to each WAP can safeguard against outages.

Siemon recommends that each zone enclosure supports a coverage radius of 13 m with 24 port pre-cabled consolidation points available to facilitate plug-and-play device connectivity. For planning purposes, an initial spare port capacity of 50% (ie, 12 ports unallocated) is recommended. Spare port availability may need to be increased and/or coverage radius decreased if the zone enclosure is also providing service to building automation system (BAS) devices and telecommunications outlets (TOs). Backbone cabling should be a minimum design of 10 Gbps capable balanced twisted pair copper or multimode optical fibre media to support 802.11ac uplink capacity.

Conclusion

A killer app forces consumers to stop and question legacy views about broadly deployed operating platforms or systems. IEEE 802.11ac is a dual-edged killer app in that it requires both 10GBASE-T and Type 2 remote powering for optimum performance - swiftly making the wait-and-see stance concerning 10GBASE-T adoption in support of LAN applications a position of the past. A properly designed and deployed zone cabling architecture utilising thermally stable shielded category 6A or higher cabling products engineered to withstand the maximum TIA and ISO/IEC ambient temperature of 60°C, plus the associated heat rise generated by 600 mA Type 2 PoE current loads, will ensure that your cabling infrastructure is a killer app enabler