When mounting APs to ceiling channel rails, an optional channel adapter AIR-CHNL-ADAPTER is used. The channel adapter comes in a two-pack and is attached to the ceiling grid clip.

Ports are easily accessible. Mode button is recessed and requires a tool such as a paperclip to engage.

Note the vent holes below the ports, avoid using chemicals or solvents around the AP as the ingress of such materials have the potential to cause damage to the device.

AP 1850 has similar physical dimensions as other Cisco APs but with a few differences in physical appearance, most of which are cosmetic changes to distinguish the different models. The mounting options and bracket configurations are identical and interchangeable between Cisco 1140, 1600, 1700, 1850, 2600, 2700, and 3700 series APs.

Different installation options are available depending upon the requirements of the customer. Brackets are available from Cisco as well as third-party companies. During the ordering process, the customer may choose one of two brackets (but not both). Each bracket is a zero-dollar ($0) option at the time of configuration. If the customer does not choose a bracket, the selection default is AIR-AP-BRACKET-1, which is the most popular for ceiling installations. The other choice is a universal bracket that carries part number AIR-AP-BRACKET-2.

If the AP needs to be mounted directly to a ceiling on the grid work, then AIR-AP-BRACKET-1 is flush mounted and has the lowest profile. However, if the AP is mounted to an electrical box, other wiring fixture, inside a NEMA enclosure, or wall mounted, then AIR-AP-BRACKET-2 is a better choice. The extra space in the bracket allows for wiring, and the extra holes line up with many popular electrical boxes. When mounting the bracket to the ceiling grid work, some ceiling tiles are recessed. For this reason, two different styles of ceiling clips, such as recessed and flush rails are available

When the AP needs to be wall-mounted, the installer should understand that walls can be a physical obstacle to the wireless signal. Therefore, maintaining 360 degree coverage may be compromised by the wall. If the wall is an outside wall and/or the goal is to send the signal in an 180-degree pattern instead, a directional antenna, often referred to as a “patch” antenna, may be a better choice assuming that the AP 1850e is used.

Avoid wall-mounting APs with internal antennas, such as the AP 1850i, unless you use the optional Oberon right-angle mount (Figure 1). The internal antenna model is designed to mount to a ceiling to provide 360-degree coverage. If wall-mounted in a non-ceiling orientation, the signal may penetrate the floor above and below causing unintended coverage. This results in additional and needless roaming access when a mobility client, for example a user with Wi-Fi phone, walks by on an adjacent floor.

Instead, use the AP 1850e (with dipoles or patch antennas) or use an optional wall mount that puts the AP 1850i or AP 1850e into a ceiling type orientation when mounted to a wall.

Note	APs with internal antennas such as the AP 1850i that are wall mounted should use the Oberon mounting bracket unless roaming is not an issue, for example, hotspot, kiosk, or small venue scenario.

Oberon model 1029-00 is a right angle mount works with “i” and “e” models to put the AP in the right antenna orientation. If the unit is an “e” model with dipoles that can be mounted (far right), then an Oberon wedge mount is not required.

See http://www.oberonwireless.com/WebDocs/Model1029-00_Spec_Sheet.pdf.

The AP 1850 series is rated for installation in the Plenum area (UL-2043). Many customers prefer to locate the AP in such a way that nothing is visible on the ceiling. In some cases, this is preferred for aesthetic reasons, so customers may install the AP above a drop ceiling. This may also be preferred in high theft areas such as classrooms or in areas where policy dictates that nothing can be visible on the ceiling.

To meet this hard requirement, optional T-Bar hangar accessories such as Erico and Cooper, can be used (Figure 1). These accessories are manufactured by third-party companies. The Erico Caddy 512a, the Cooper B-Line BA50a, or similar T-Bar Grid T-Bar hangars can be used.

For more information, see:

www.erico.com

www.cooperindustries.com

Note

Installing APs above the ceiling tiles must be done only when mounting below the ceiling is not an option. The tiles must not be conductive; such installations will degrade advanced RF features such as voice and location, so verify coverage and performance. Always, try to mount the AP as close to the inside middle of the tile as possible, and avoid areas with obstructions

Customers needing to install the APs in harsh environment such as sporting areas, stadiums, open garden areas, or warehouse freezers, where it may be exposed to weather, may use a NEMA type enclosure.

Note

Some APs may not be certified for outdoor deployments in a NEMA enclosure. This varies around the world, for example some regulatory agencies permit AP outdoor NEMA enclosures if the AP is indoors such as a freezer or garden area but may prohibit its usage outdoors. This seems to vary with regard to weather radar compliance, UNII-1 compliance, and so on. Check with your Cisco account team or the communications regulatory agency that has jurisdiction in your area.

Third-party sources for NEMA type enclosures include:

www.oberonwireless.com

www.sparcotech.com

www.terra-wave.com

When using a NEMA type enclosure, ensure that the cables exit out of the bottom of the enclosure so that rain and moisture do not run down the cable into the enclosure. Also, the color of the enclosure may affect the heat rating; for example, a black enclosure gets much hotter in the sun than a white one. You may also want to use a pressure vent to prevent moisture accumulation.

While the AP 1600, 1700, 1850, 2600, and 3600 work fine with CAT-5e cable, for newer cable installations, it is recommended that the customers use CAT6a. Because, CAT6a is the cabling required by the 10GE standard.

Whenever practical/possible, ensure that the antenna cable runs as short as possible. Cisco offers low loss (LL) and ultra low loss (ULL) cables, which have the same characteristics as Times Microwave LMR-400 and LMR-600.

Cisco cables carry the part number AIR-CAB (Aironet Cable) and its length parameter. For example, a 20 Ft length of LL cable with RP-TNC connector is Cisco AIR-CAB-020LL-R. These heavy black cables are not Plenum rated and are primarily for outdoor use or manufacturing areas.

If you have an Wi-Fi device such as an AP and you are going to use another AP in the vicinity on a different channel, it is recommended that you space each AP apart by approximately 6 ft (2 meters). Avoid clustering the APs or the antennas from different APs together, because this could cause degradation in performance. This recommended distance is based on the assumption that both devices operate in the unlicensed band and do not transmit RF energy more than 23 dB, that is, 200 mW. If higher power is used, space the APs farther apart.

If you have other devices that transmit, especially if they operate in the same frequency ranges, for example, frequency hopping legacy APs or other devices that operate close in frequency to those of the AP (think below or above the 2.4 and 5 GHz band), you should consider moving or separating the devices as far as you can. After you have done this, check for interference by testing both devices at the same time under heavy utilization (load) and then characterize each system independently to see how much, if any, degradation exists.

Warning

To comply with FCC, EU, and EFTA RF exposure limits, antennas should be located at a minimum of 7.9 inches (20 cm) or more from the body of all persons. For more information, see the Declarations of Conformity section in the Cisco Aironet 1850 Series Access Points Hardware Installation Guide.

When installing APs near electrical or telecommunications equipment, keep all wiring and metal away from the antennas and avoid placing the antennas near electrical lines. Do not route wiring electrical or Ethernet in the near field (6-15 inches) from the antenna. Try to refrain from installing the AP in the electrical closet, because the best place for the AP is as close to users as possible/practical. If you have remote antenna cables from such a closet, you may be required to use Plenum rated cable (see local fire/safety regulations for more on this).

Below are a few URLs for understanding interference:

http://www.cisco.com/en/US/prod/collateral/wireless/ps9391/ps9393/ps9394/prod_white_paper0900aecd807395a9_ns736_N etworking_Solutions_White_Paper.html

http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps10981/white_paper_c11-609300.html

Elevator coverage can sometimes be accomplished by placing APs in the near field of an elevator, typically on each floor near the elevator door. Because, elevators often have metal doors and the shafts are often concrete or contain other materials that degrade Wi-Fi coverage. It is important to check the coverage inside the elevator. Though such coverage can be challenging, it is often do-able, especially if the elevator is only a few floors.

High rise elevators are more challenging because roaming issues are problematic; the client is cycling through a large number of APs quickly. Some companies that do in-elevator advertising put a patch antenna on the floor inside the shaft and a patch antenna on the bottom of the elevator car, while other companies use leaky coaxial cable running on the side of the shaft.

When installing any Wi-Fi equipment inside the elevator cars or shafts, local regulations need to be followed. Because, many times such installations are prohibited either for safety reasons or because the building owner or local fire department may prohibit the same. Only elevator repair persons or contractors who have experience with this kind of work should be in those areas.

When the AP negotiates 802.3at (high power), it always tries first to negotiate using Cisco Discovery Protocol (CDP). If the negotiation fails, the AP will attempt to negotiate using Link Layer Discovery Protocol (LLDP). LLDP is a vendor-neutral method for advertising device identity and capabilities.

So, the AP 1850 first uses CDP to get 20.9 W and reserve that amount of power. If CDP fails, the same process starts using LLDP. So, a non CDP response time out (often approaching 60 seconds) would need to occur before the LLDP negotiation starts. In both cases, the requirement is obtain 20.9 W power.

If the AP has enough power, it shows Full Power in the PoE settings. See Figure 1.

However, if the power source equipment such as PoE switch, mid-span, or injector lacks the ability to properly negotiate high power, go to “ANY” mode and take whatever power the device can provide, which would likely be 15.4 W (802.3af).

If the power source is limited to 15.4 W (802.3af), then the AP negotiates and reserves 15.4 W.

The AP functions with the available power sourcing. If the power is not enough to be fully functional, then the AP makes an effort to shut down and re-negotiate to be able to function at 15.4W. Also, the AP indicates LOW or MEDIUM power on the controller and functions at reduced capability. See Table 1.

Note	If the power source does not support Cisco Discovery Protocol, for example third party switch, then uncheck its usage. See Table 1.

The internal antennas are rated at 3 dBi at 2.4 GHz and 5 dBi at 5 GHz.

For an overview of 802.11ac, see the technical white paper at the following URL:

http://www.cisco.com/c/en/us/products/collateral/wireless/aironet-3600-series/white_paper_c11-713103.html

Currently in the US, there are 25 (20 MHz) channels, 12 (40 MHz) channels, and 6 (80 MHz) channels. 802.11ac (Wave-2) supports 160 MHz channels but currently there are only two channels available. This is likely to get better, because the Federal Communications Commission and other regulatory bodies realize the need for more unlicensed spectrum and are actively working to free up more spectrum.

Let us take a look at the frequencies available and how the channel bonding would work.

Right now in the US, there are only four 80 MHz channels but this is likely to improve.

Future of spectrum allocation?

• In the US, there are currently 25/12/6/2 channels with bandwidth 20/40/80/160 MHz channels.

• With the opening up of 5.35 – 5.47 GHz and 5.85 – 5.925 GHz, the number of channels increases to 34/16/8/3.

• If the industry manages to take back the TDWR channels, the number increases to 37/18/9/4.

So, as time progresses, you should see additional channels becoming available.

Most clients (USB) that are emerging are 2 spatial stream, and by using 80 MHz bonding, you can achieve up to 866 Mbps. Figure 1 shows the Netgear A6200 client card.

Note	The software reports channel is 36 (this is where the channel bonding starts). On a spectrum analyzer, you can see that the actual channels in use are 36, 40, 44, and 48.

Note	For clients to link at 80 MHz, you have to set the channel width to 80 MHz on the AP.

Devices such as Samsung Galaxy S4, ZTE’s Grand Memo, HTC One, and new notebooks such as the Apple 2013 Macbook Pro are the first to market 802.11ac devices. It is expected that integrated notebooks and tablets (those devices often supporting 2 and 3 spatial streams) will start to become a commonplace.

Currently, Cisco’s test bed for interoperability has the following configuration types.

Interoperability matrix for APs, Clients and security types tested with the below clients.

• Integrated Devices – Shipping

  • Apple - Macbook Air

  • Intel Dual Band Wireless - AC 7260

  • Samsung S4

  • HTC ONE

  • ZTE Grand Memo

• USB Clients - Shipping

  • LinkSys AE6000 1x1

  • Asus – USB-AC53 2x2

  • NetGear – A6200 2x2

  • Belkin P-F9L1106 - 2x2

  • D-Link DWA-182 – 2x2

  • Buffalo ac866 – 2x2

  • Edimax EW-7822AC– 2x2

• Ethernet to 802.11ac Bridges - Shipping

  • LinkSys (Belkin) WUMC710

  • Buffalo WLI-H4-D1300

• List for identifying new 802.11ac hardware:

  http://wikidevi.com/wiki/List_of_802.11ac_Hardware

Some early observations show that USB clients can appear to be a bit slow in performance depending on drivers, USB port versions, and so on. Also, it is observed that some clients have trouble in maintaining an 80 MHz bandwidth in the Dynamic Frequency Selection (DFS) bands. Table 1 lists the clients that had reasonable success during testing.

Wi-Fi is a highly variable technology and there are many factors that could impact performance. Few examples are: environment, client, channel, AP placement, and client distance from the AP.

This section lists some examples of installations that are not recommended. It is very difficult to provide good Wi-Fi service with a poor installation. Always try to avoid metal and clutter.

When mounting devices, the AP should be level and secured so that it does not sway or move. Keep the AP away from metal objects and try to place it as close to the users as possible.

Remember, the best place for an AP is as close to the users as possible. Avoid metal or conductive objects in the near field (they cause the radio waves to become directional and increases nulls (dead spots)). If you must mount the AP in a high ceiling, look at directional antennas to direct (angle down) the signal to the intended target area and always mount dipoles in the correct orientation.

Tip	When mounting antennas outside, always mount with the WIRES DOWN and never obstruct or put weather proofing material over the drain holes.

With 802.11n, a device can transmit multiple spatial streams at once, but only directed to a single address. For individually addressed frames, only a single device (or user) gets data at a time. This is referred to as Single-User MIMO (SU-MIMO). With the advent of 802.11ac Wave-2, a new technology is defined, called Multi-User MIMO (MU-MIMO). Using this technology, an AP can use its antennas and radio systems to transmit to different clients, all at the same time over the same frequency spectrum.

MU-MIMO with the AP 1850 is limited to a maximum of 3 spatial streams simultaneously.

To send data to user 1, the AP forms a strong beam towards user 1, shown as the top right lobe of the blue curve (Figure 3). At the same time the AP minimizes the energy for user 1 in the direction of user 2 and user 3. This is called “null steering” and is shown as the blue notches. In addition, when the AP sends data to user 2, it forms a beam towards user 2, and forms notches (nulls) towards users 1 and 3, as shown by the red curve. The yellow curve shows a similar beam towards user 3 and nulls towards users 1 and 2. In this way, each of users 1, 2, and 3 receives a strong copy of the desired data that is only slightly degraded by interference from data for the other users.

For all this to work properly, especially the deep nulls, the AP has to know the wireless channel from itself to all of the users very accurately. Because the channel changes over time, the AP has to keep measuring the channel, which adds overhead.

Meanwhile, the client receives its desired signal distorted by some interference from the signals intended for other users. This interference makes the highest constellations such as 256QAM infeasible within an MU-MIMO transmission.

In summary, MU-MIMO allows an AP to deliver appreciably more data to its associated clients, especially for small form-factor clients (often BYOD clients) that are limited to a single antenna. If the AP transmits to two or three clients, the effective speed increase varies from a factor of unity (no speed increase) up to a factor of two or three times, according to wireless channel conditions.

You cannot configure to use MU-MIMO, the clients will advertise this capability and the AP will put them into groups.

Challenges of Multi-User MIMO

• Requires precise (CSI) channel state information to maintain deep nulls so that each MU-MIMO client can properly decode its data without too much interference from the other clients.

• MU-MIMO CSI, pre-coding group data adds overhead as does their acknowledgments and so on.

• Rate adaptation is slow – Wave-2 clients to be integrated into new laptops, tablets, and phones but this moves slowly.

• MU-MIMO is a new technology and needs to develop and mature. So, issues such as lower end clients may be sensitive to MU grouping overhead and client driver version issues.