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PART II

Cabling and Wireless Installation Articles 3-23-2015

Last year I wrote an article (May 2014 http://oberonwireless.com/news/blog) on IEEE 802.11ac compliant products –suggesting that products built to this standard would feature “wired like” speeds, data rates beyond 1 Gig, unprecedented user density, scalability in large venues, and better client battery life. All this new capability is provided by larger swaths of bandwidth available in the 5 GHz band and sophisticated modulation and coding schemes enabled by advanced signal processing techniques. I described in that article that 802.11ac is being rolled out in two waves, actually referred to as Wave 1 and Wave 2. I also described that Wave 2 products will engage, for the first time, Multi-User Multiple Input-Multiple Output, or MU-MIMO, technology. MU-MIMO has the ability to significantly advance data throughput. In this article I will discuss Wave 2 data rates in more detail, compared to Wave 1 and prior technologies, and implications on the wireline network. I will also attempt to make a forecast of requirements for planning cabled infrastructure into the next decade.

 

Bandwidth for 802.11ac

One of the big advances in 802.11ac (both Wave 1 and Wave 2) is that it specifies use of the 5-6 GHz band only. That does not mean that 802.11ac products may not support legacy 2.4 GHz products, but it does mean that moving forward Wi-Fi networks will operate most effectively in the 5-6 GHz band, and avoid the crowded band at 2.4 GHz, which is shared with microwave ovens and other interference sources. The 5-6 GHz band provides over 500 MHz of bandwidth available providing for up to 25 20-MHz channels, or 12 40-MHz channels, or 6 80-MHz channels, and, for the first time 2 160 MHz channels as shown in the chart below. In the future, the FCC may free up an additional 240 MHz of bandwidth in this band for Wi-Fi use.

Figure 1 -Current FCC Channel Plan – Courtesy of Peter Lane, Aruba Networks- Atmosphere 2015

Figure 1 -Current FCC Channel Plan – Courtesy of Peter Lane, Aruba Networks- Atmosphere 2015

Figure 2 -Potential future FCC Channel Plan– Courtesy of Peter Lane, Aruba Networks- Atmosphere 2015
Figure 2 -Potential future FCC Channel Plan– Courtesy of Peter Lane, Aruba Networks- Atmosphere 2015


IEEE 802.11ac Wave 1 and Wave 2

The table below outlines some of the advances of 802.11ac Wave 1 and Wave 2 over the prior technology, 802.11n.

Technology

802.11n

802.11ac Wave 1

802.11 Wave 2

Modulation Type

64 QAM

256 QAM

256 QAM

Spatial Streams

Up to 4

Up to 8

Up to 8

Max. channel size

40 MHz

80 MHz

160 MHz

MIMO

SU-MIMO

SU-MIMO

MU-MIMO

Table 1 - 802.11n, 802.11ac Wave 1 and Wave 2 capabilities
 
I won’t get into the details of the modulation type other than to say that the higher QAM number provides for more bits of information to be encoded into a given piece of bandwidth. The spatial streams (or SS) improve data rates by actually encoding data into separate transmitted waveforms and recombining these wave forms at the receiver. This is an oversimplification, but again, the higher the number of SSs the higher the date rate. Typical 802.11ac APs will exploit only 4 of the 8 spatial streams. A larger number of spatial streams would require more transmitters and antennas. Of course the wider bandwidth available for use by 802.11ac (80 MHz and 160 MHz Very High Throughput or VHT) will increase data rate

Single User MIMO (SU-MIMO) and Multi-User MIMO (MU-MIMO)

I think the most intriguing introduction by Wave 2 is Multi-User Multiple Input Multiple Output or MU-MIMO, an advance over SU-MIMO. SU-MIMO was introduced with the 802.11n generation products. With SU-MIMO, a device can transmit multiple spatial streams from multiple antennas at once, but only directed to a single device or address. The multiple spatial streams can improve the reception and throughput to a device, but only one at a time (see figure 3).

802.11ac Wave 1 products still engage SU-MIMO, but Wave 2 introduces MU-MIMO. MU-MIMO provides the ability for the Access Point (AP)to transmit to several clients simultaneously. Using advanced signal processing and beam-forming, the AP creates a “beam” to each individual client. In fact, the AP can create a beam to several clients, at the same time, on the same frequency channel. This transition to MU-MIMO is anticipated to yield up to 33% increase in data capacity at the access point, in Wave 2 over Wave 1.

FIGURE 3 SU-MIMO versus MU-MIMO; the number of client spatial stream cannot exceed the number of spatial streams offered by the AP
FIGURE 3 SU-MIMO versus MU-MIMO; the number of client spatial stream cannot exceed the number of spatial streams offered by the AP  

How Many Clients can a MU-MIMO AP Communicate with Simultaneously

802.11ac Wave 2 permits up to 8 spatial streams. However, in practice, wave 2 products will support 4 spatial streams, while expanding the channel width from 80 MHz to 160 MHz. The total number of clients an AP can support simultaneously is dependent on the number of spatial streams demanded by the client devices. For example, a 4SS (spatial stream) AP can support four 1SS clients (such as smart phones, figure 4a) or one 2SS client (tablets) plus two 1SS clients (figure 4b). The total number of client spatial streams must not exceed the maximum number of spatial streams supported on the AP.
           

Figure 4a – four 1SS clients connected to 4SS AP        Figure 4b- two 1SS and one 2SS client connected to 4SS AP Credit for figure 3&4: Cisco will ride the 802.11ac Wave2, Bill Rubino, Cisco Mobility blog

Figure 4a – four 1SS clients connected to 4SS AP. Figure 4b- two 1SS and one 2SS client connected to 4SS AP Credit for figure 3&4: Cisco will ride the 802.11ac Wave2, Bill Rubino, Cisco Mobility blog

Wave 2 802.11ac product will be available in 2015, and mostly as client devices. Look for a rapid rollout of Wave 2 APs in 2016, with the following promised capabilities:
•    Wired-like experience at higher speed, noticeably faster connectivity for the end user
•    Higher density deployments enabled through clients getting on and off the network faster
•    Significantly better client battery life
•    Wide selection of client devices now available with integrated 802.11ac

Wave 2 Anticipated Data Rates

The important question for cabling professionals is “what is the data rate that the cabled infrastructure needs to support?” The answer is complicated because it is dependent on the makeup of client devices, bands engaged, and other factors. But I will work through a couple of scenarios to demonstrate some of the considerations

First of all it is important to distinguish the “Over The Air” or OTA data rate versus the TCP throughput at the Ethernet connector. The OTA data rate is often the data rate listed in the AP spec sheet.  But the TCP throughput at the Ethernet Connector (which is the value the cabling professional is most interested in) is typically 70% less than the OTA data rate. Table 2 shows the OTA data rate for different scenarios. Most smart phones are only 1 SS, and tablets and laptops are 2 SS. So the other scenarios (S33 and 4 SS clients) are perhaps futuristic. Table 3 shows the TCP throughput at the Ethernet connector for these scenarios.

Over the Air data rate at the AP (Mb/s)

 

1SS Client

2SS Client

3SS Client

4SS Client

3 SS VHT 80 MHz AP

433 Mb/S

867

1300

N/A

4 SS VHT 80 MHz AP

433

867

1300

1733

3 SS VHT 160 MHz AP

867

1733

2600

N/A

4 SS VHT 160 MHz AP

867

1733

2600

3466

Table 2 -802.11 ac Wave 2 Over The Air Data Rates.  Courtesy of Peter Lane, Aruba Networks- Atmosphere 2015

TCP Throughput at the AP (Mb/s)

 

1SS Client

2SS Client

3SS Client

4SS Client

3 SS VHT 80 MHz AP

303 Mb/S

607

910

N/A

4 SS VHT 80 MHz AP

303

607

910

1213

3 SS VHT 160 MHz AP

607

1213

1820

N/A

4 SS VHT 160 MHz AP

607

1213

1820

2426

Table 3- 802.11 ac Wave 2 TCP throughputs at the Ethernet connector. Courtesy of Peter Lane, Aruba Networks- Atmosphere 2015

The great thing about MU-MIMO is that 3 individual client devices can be pushing data to/from the AP instantaneously. So a new chart needs to be created that shows scenarios wherein multiple clients are connected instantaneously. There is some loss in efficiency in this scenario, so, for example TCP throughput in a 3SS VHT 160 MHz AP serving (3) individual 1 SS client device is lower than 3 X 607 Mb/s. It’s actually about 75% of 3 x 607 Mb/s, which is 1, 365 Mb/s. Table 4 shows some scenarios for TCP throughput at the AP with different client scenarios. Again, when using MU-MIMO, the throughput is 75% or less of the additive throughput for individual clients.

MU-MIMO Best Case TCP Throughput at the AP (Mb/s)

 

3 individual 1SS Clients

2 1SS + 1 2SS Clients

3 SS VHT 80 MHz AP

683 Mb/S

622

3 SS VHT 160 MHz AP

1365

1244

     
 

4 individual 1SS Clients

2 individual 2SS Clients

4 SS VHT 80 MHz AP

910

789

4 SS VHT 160 MHz AP

1821

1578

Table 4- 802.11 ac Wave 2 TCP throughputs at the Ethernet connector, for different client scenarios - Courtesy of Peter Lane, Aruba Networks- Atmosphere 2015

In my opinion, the VHT 160 MHz will rarely be used in enterprise environments because of how inefficiently it uses the available spectrum (just look at the unused spectrum when using the 160 MHz channel in figure 1). Most enterprise users will continue to use 20, 40 and 80 MHz channels, and there is good evidence that the 20 MHz channel may be the best to use in high density environments like auditoriums, classrooms and stadiums. Given this, the data rate at the Ethernet connector will not exceed about 910 Mb/s as shown in the chart above (4 individual 1 SS clients connected to 4SS AP.  

So why does the TIA TSB-162A recommend use of Category 6A cabling, capable of 10Gb/s data rates ? 802.11ac Wave 2 client devices will be rolling out in 2015, so it appears that a 1 Gb/s cabled infrastructure is adequate for 2015, but what will happen beyond this year? I already mentioned that the FCC can potentially add another 50% to current bandwidth at 5 GHz, and manufactures can (will) begin to manufacture 8 Spatial Stream APs which, when connected to 8 individual 1 SS clients, will require 1.8Gb/s TCP throughout. Modulation, coding, and beamforming techniques will continue to advance, providing higher data rates. Also, APs designed according to the IEEE 802.11ad standard at 60GHz will require ~5 Gb/s TCP throughput connectivity.  

Given that the cabling infrastructure should be designed to last 10-15 years, what would be the anticipated requirement for wiring WAPS from 2015 through 2025? One approach is to look at data rates for prior technologies and how these have advanced over the last two decades. Figure 4 shows a chart plotting the over the air data rate (OTA) and TCP throughput, as a function of technology and approximate timeframe (year) of widespread adoption.  This graph is very “approximate” but one can see that in 2015, we are right at the 1 Gb/s threshold, and with widespread adoption of 802.11ac Wave 2 over the next few years we will clearly be beyond the 1 Gb/s TCP throughput requirement.  I use the IEEE 802.11ad standard to forecast TCP throughput in 2025 (although theses products are currently available) at 5 Gb/s, but I actually think this is on the low side. Given the factors I mentioned above, I think we will be going beyond the 10 Gb/s threshold in less than 10 years, perhaps even 5 years.
 

Figure 5 –Data rate versus technology and approximate year of widespread adoption
Figure 5 –Data rate versus technology and approximate year of widespread adoption  

Cabling and Installation Considerations for 802.11ac

Given that new Wi-Fi deployments with 802.11ac will be mission critical, it is all the more important to plan for effective cabling, location and positioning of access points. The antennas will be required to effectively create spatial streams and beam-form to multiple clients. WAPS should be positioned to achieve optimum antenna coverage and performance, and may be located densely to serve high densities of client devices.  Some important considerations are as follows :

  1. Per TIA TSB-162A – provide at least one Category 6A cable to each AP location. Many designers are prudently planning on two cables to each AP location.
  2. Plan for APs to serve no more than 25 clients, per TIA 4966- Standard for Educational Facilities. Thus, a classroom for 100 students will require at least 4 APs. (Many very high density installations may require up to 100 client to connect to a AP, but this is a special case).
  3. Mount APs in the ceiling if possible, in a high location above obstructions where possible.
  4. Do not mount APs above suspended ceilings; the ceiling tiles and gridwork attenuate and disrupt the signal.

Oberon Model 1064 locking ceiling mount for Cisco AP   Model 1057 with wireless transparent dome

APs are ideally secured in the ceiling or other high location with antennas unobstructed by ceiling tiles or ceiling grid- Oberon Model 1064 locking ceiling mount for Cisco AP. Model 1057 with wireless transparent dome

5)    Mount access points in the preferred horizontal orientation, whether in the ceiling or on the wall, rather than flat on the wall. All leading AP manufacturers recommend this.

Oberon Model 1012 locking right angle surface mount bracket for access points   Oberon Model 1008 beam clamp bracket and paintable vanity cover

APs should be mounted in the preferred horizontal orientation to achieve best antenna pattern coverage -Oberon Model 1012 locking right angle surface mount bracket for access points. Oberon Model 1008 beam clamp bracket and paintable vanity cover

6)    In auditoriums and classrooms, it may be beneficial to use directive antennas to provide zones of coverage

Oberon Model 1013 articulating antenna and AP mount for auditoriums and classrooms   Paintable vanity cover for 1013

Oberon Model 1013 articulating antenna and AP mount for auditoriums and classrooms. Paintable vanity cover for 1013.


7)    In auditoriums, stadiums, and large classrooms, it may not be possible to mount APS in the ceiling. An alternative is to mount APs underneath seating to achieve the density required. APs should be properly protected in this environment.

Oberon Model 1020 compact NEMA 4 enclosure for underseat installation of AP
Oberon Model 1020 compact NEMA 4 enclosure for underseat installation of AP


8)    Physically protect the AP and antenna from the environment

Oberon Model 1016 (left) non metallic lockbox for WiFi WAPS   Oberon Model 1015 (right) non metallic lockbox for WiFi WAPS

Oberon Model 1016 (left) and 1015 (right) non metallic lockboxes for WiFi WAPS


9)    Plan for high density AP installations. A professional installation will provide the physical security, code compliance, and aesthetics mandated by the installation environment

Oberon Model 1043- economical hard ceiling installation kit for high density WiFi installationsOberon Model 1043- economical hard ceiling installation kit for high density WiFi installations

Oberon Model 1043- economical hard ceiling installation kit for high density WiFi installations

Oberon Model 1044- economical suspended ceiling installation kit for high density WiFi installations     Oberon Model 1044- economical suspended ceiling installation kit for high density WiFi installations
Oberon Model 1044- economical suspended ceiling installation kit for high density WiFi installations

Oberon’s wireless AP mounting and enclosure solutions are designed by wireless experts, and provide a means to securely, conveniently, and aesthetically mount the AP while optimizing antenna and WiFi performance.

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