Cisco 1500 Series Outdoor Access Point - Antenna Config

[dot1x]

Could someone advise if we could use Top and Bottom antenna ports of any 1500 Series AP with external antenna in 5GHz for Point to Point/Multipoint links?

For example, if I have 1532E, could we use Bottom 2 Ports with a Dual Band Directional Antenna AIR-ANT2588P3M-N= to run in 5GHz band, and top 2 Ports with 5GHz Directional Antenna AIR-ANT5114P2M-N= Is it possible to use the ports in this way?

[Ric Beeching]

The feature is called flexible antenna but doesn't quite meet your requirements. If you are trying to go for something like 5Ghz backhaul and 5Ghz on different antennas that will not work. If you were to do 5Ghz backhaul and then 2.4Ghz for client access using the flexible setup, that is possible.

Check out the 1532 setup guide:

https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/7-6/b_1532_dg/b_1532_dg_chapter_01.html#concept_893ED444B7764D57996AF54887C7C930

Flexible Antenna-Port Configuration

There are two terms that are used when referring to Antenna Band Mode Configurations:

• Dual Antenna Band Mode – The bottom two ports, port 1 and port 2, are used for dual band 2.4 GHz/5 GHz Dual Radiating Element (DRE) antennas.
• Single Antenna Band Mode – The top two ports, port 3 and port 4, are used for 5 GHz Single Radiating Element (SRE) antennas while the bottom two ports, port 1 and port 2, are used for 2.4 GHz SRE antennas.

[dot1x]

Hi Ric,

I did check the setup guide for 1532, but was a bit confused if we use dual band antennas, the top ports will be unused.

Thanks for your input.

Is this even possible with any outdoor AP?

I remember something like this in an indoor AP 3800 series, where both radios can be used in 5GHz.

  Dual 5-GHz mode: Both radios inside the access point operate on the 5-GHz band, maximizing the benefits of 802.11ac Wave 2 and increasing client device capacity.

Reference: https://www.cisco.com/c/en/us/products/collateral/wireless/aironet-3800-series-access-points/datasheet-c78-736498.html

[Ric Beeching]

It's because the AP ultimately only has one chipset per band so you can't use the top and bottom for both concurrently, you'd effectively need an AP that  has two separate 5Ghz chipsets for this to work like what you have referenced. Unfortunately the AP would also need to support such features which is not the intenton of the flexible/XOR radio on those APs. They are there to provide extra client density/connectivity for 'normal' client connectivity.

Depending on your budget, I've often deployed the 1532 and other outdoor APs as the backhaul bridge with another AP attached in local/flex mode directly to the ethernet port of the 1532. You can then serve dual-band clients with that AP.

Ric

[dot1x]

Thanks Ric, I got your point.

Could you please have a look at the attached picture?

I'm looking at 1562E as it has 802.11AC Data Rates.

Site A is the main site.

If I use 1562E with AIR-ANT5180V-N omnidirectional for Site B and C (each 120m from Site A) LOS.

and AIR-ANT5114P2M-N= for site D (600m from Site A) LOS.

Would these antennas cover the required distance with LOS?

Would I need 2x1562E at site A, 1 for site D and other for sites B and C?

Is this design good enough?

[Ric Beeching]

It's tricky to assist with these sorts of things without doing site surveys, link budget calculations etc but I can offer some points against the proposal:

• In most cases omni-directional APs for bridge links are not recommended because you end up with a lot of wasted energy at the RF output.
• Point-to-multipoint links will result in a drop in performance for both links C and B as they are sharing a cell.
• If points B and C are using omnis as well then the link could be very poor on the send as well as receive... I'd expect pretty poor performance there.
• The link between A and D is theoretically feasible providing LoS is clear and it is all setup correctly... I have helped setup similar links of that distance or more.

To save on antennas costs, the 1562D looks quite useful as it offers directional antennas built-in to the AP. The gain is less than the 5114 (10 vs 14 dB).

I'd look into 6 x 1562D and have 3 separate point-to-point links personally but I am absolutely not an expert in bridge links and this is purely an opinion. :)

[dot1x]

I appreciate your honest opinion :)

Is it possible to have omnidirectional antenna at location A and directional antennas at location B and C?

Also, is this possible:

As there are 2 ports for 5GHz, can we have 2 different directional antennas on each single port and direct them to site B and C each?

I understand, I won't have MIMO capabilities then, but is this even possible to use each antenna port as SISO?

[Ric Beeching]

Unfortunately I'm going to have to crush your hopes there and recommend against either approach.

The communications are bi-directional and having mis-matched antennas at each end will likely cause you  more headaches then resolving any issues now. You are likely to end up with uni-directional links in that scenario and the cell will still be reduced due to sharing the omnidirectional part of it.

Unless the AP in question is specifically designed for SISO / antenna separation then attaching different antennas to different radios is possibly the worst thing you could ever do. The APs rely on the antenna send/receive diversity and make use of all physical connections to amplify the signal in both directions. By attempting to use one antenna for link A and another for link B you'll just confuse the hell out of it and likely suffer extremely poor performance.

Ric

[dot1x]

Thanks for detailed comment on my each question.

So, bottom line would be to use point to poin links having 3 APs at site A?

[Ric Beeching]

For best performance  on this setup, pretty much. I'm not saying omni-directionals aren't possible but 120m is a long way.. depends also on your far-side hardware too. If you have some spare APs you could always survey it and see how it goes? Again, very tricky without doing some testing and calculations, particularly as the far-side requirements will also influence how much you throughput you need.

Ric

[dot1x]

I'd be using same AP at each site 1562E.

Also, there's line of sight between all the sites.

What do you reckon, 8dBi omni wouldn't cover 120m LOS?

[Ric Beeching]

It might cover it, it might not but there's all the reasons above plus we haven't even covered off throughput and far-side requirements which will be large factors on top of the link. If you are going to deploy 1562s then I wouldn't waste $ on the E's + antennas when you can buy 1562Ds and achieve better performance :). 

[dot1x]

8-10 users at each site using emails, internet, and a few CCTV Cameras.

So, your suggestion would be to go with 6x1562Ds?

[Ric Beeching]

If it were me I would do some link calculations (google for wireless link budget calculators) then, if the funding was available, I would purchase at least 2 of those 1562D APs and survey each link with them using iPerf throughput testing (connect a laptop to each end of the bridge and use the free iPerf tool).

Alignment and tuning of the radios is key for these setups. What you're trying to achieve is too complicated to simply say 'yep this will work'. 8-10 users is low but the cameras might suffer if the links aren't consistent. On the other hand they may be fine! Easiest way is to test :).

Ric

[dot1x]

Thanks Ric for your time and input.