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LTU - Frequently Asked Questions


Overview


This article answers some of the most common questions about airFiber LTU. Click on the question that interests you to expand and collapse the answers. This article will be updated as more common questions are brought to our attention. If you feel that a question is missing, please click the feedback button at the bottom of the page and let us know! 


Frequently Asked Questions


Are LTU products compatible with other airMAX or airFiber products?
LTU is a completely new platform based on proprietary technology, which doesn't use 802.11 protocol, making it incompatible with 802.11n and 802.11ac devices. For that reason it is NOT compatible with airMAX M5 nor with airMAX 5AC.

On the other hand, although LTU is based on airFiber technology, it uses a different protocol for communication, making it incompatible with other 5GHz airFiber products such as AF-5X or AF-5/5U.
Does AF-5XHD support Point to MultiPoint (PtMP)?

airFiber 5XHD hardware is fully capable of Point-to-MultiPoint (PtMP) mode, but the current firmware version only supports Point-to-Point (PtP) mode. That being said, future firmware version will support Point to MultiPoint modes as well, once available it will be announced on our Community Blog.

What products are part of the LTU family?
LTU family is composed today of two products:

However, new products are coming this year.

What is the input voltage range of the airFiber LTU products?

Both AF-5XHD and the AF-LTU support any voltage from +18Vdc to +56Vdc.  Just make sure the PoE source can deliver at least 24 Watts to compensate any voltage drop because of cable length.

Does AF-5XHD support NxN mode?
The current firmware version doesn't support NxN mode (multiplexing). However, we are working on new firmware versions that will support NxN mode. Target for release is 2018.
What is the difference between the AF-5XHD and the AF-LTU?
There are four main differences:
  • Dual RJ45 port only available in the AF-5XHD. Both ports can be used for PoE IN and the Config port can be configured to also work as DATA port, but both RJ45 ports don't support bonding.
  • Connectorization: AF-5XHD comes with 3 RP-SMA ports, the one in the middle for GPS, and the other two for chain 0 and chain 1, for antennas like the RocketDish or AF-5G23/30/34-S45 antennas. On the other hand, the AF-LTU comes with a waveguide connector for waveguide antennas, like the PrismAP antennas. Also, the AF-LTU comes with a built-in GPS antenna.
  • Only the AF-5XHD offers IP67 protection (optional adapter could be required)
  • AF-LTU support Point-to-MultiPoint mode out of the box. AF-5XHD requires a new firmware (still under development) to support PtMP mode.
NOTE: AF-5XHD chains can work in V&H or Dual Slant polarization depending on the antenna you are using.
What are the differences between the AF-5X and the AF-5XHD

AF-5XHD includes all AF-5X features but NxN mode and TDD Frequency Split (both under development for the HD version), plus:

  • 1024QAM modulation on the entire 5GHz band (will soon support 4096QAM modulation)
  • Extended frequency range from 4800MHz to 6200MHz for licensed applications (only for International units)
  • Built-in Accelerometer for better alignment and tampering detection
  • Bluetooth for easier configuration from Smartphones
  • Up to 1+Gbps performance and 2,000,000pps processing power
  • More channel width options adding 60, 80 and 100MHz channels
  • Improved interference mitigation
  • Active Live airView (doesn't drop the wireless link for scan)
  • More powerful Web UI
  • Point-to-MultiPoint mode (in a future firmware version)
  • Dual PoE IN
  • Re-configurable Config port to operate as DATA port
  • Among many others
What antennas are compatible with each LTU product?
AF-5XHD supports connectorized RP-SMA MIMO antennas including but not limited to: AF-5G23-S45, AF-5G30-S45, AF-5G34-S45, RD-5G30, RD-5G30-LW, RD-5G34, AM-5AC21-60, AM-5AC22-45, AM-5G16-120*, AM-5G17-90*, AM-5G17-90A*, AM-5G19-120*, AM-5G20-90*, AM-M-V5G-TI, AM-V5G-Ti.

AF-LTU supports Ubiquiti waveguide antennas, including but not limited to: PrismAP-5-30, PrismAP-5-45, PrismAP-5-60, PrismAP-5-90 and LTU-Extend (27dBi dish) antennas.

* Supported antenna but not recommended.
What is the maximum number of CPE per AP in LTU PtMP mode?
The maximum number of active CPEs per AP in PtMP mode is 250 subscribers. However, if you want to offer high-speed services (over 50Mbps per customer) we highly recommend to limit the number of CPEs per AP to 100, or even lower if you offer a low oversell ratio.
What kind of services are supported in LTU networks?
Any IP-based service should work fine on LTU networks, including but not limited to:
  • High-Speed Internet
  • IPTV
  • VoIP
  • IP Video surveillance
  • Machine to Machine communication based on TCP/IP
What is the maximum link distance in Point to Point (PtP) and Point to MultiPoint (PtMP) Modes?
There's no strict limit on the platform. However, there are two factors that will determine the maximum link distance (always assuming clear Line of Sight):
  1. The antenna gain of each side (the higher the antenna gain the longer the link)
  2. Tx Power (the higher the Tx Power in most cases will allow longer distance links). This value is determined by your country and could vary depending on the frequency you are using.

Tips:

  • In order to simulate the expected link capacity for your link, please simulate it using our free link planning tool, https://airlink.ubnt.com
  • Always select the right country code for your installation, using a different country code could violate local telecommunication laws and involve high fines. 
What is the expected latency?
It depends on the Frame Length selected, but using the shortest Frame Length average latency will be 2-3ms under normal circumstances.
How do I synchronize my network?

GPS Sync only needs to be enabled in the Access Point, there's no need to enable it on the CPEs. Simply enable the GPS Sync option in the Wireless section and make sure Duty Cycle and Frame Length is the same in all the APs you wish to synchronize, like so: 

 Screen_Shot_2018-04-11_at_9.43.14_AM.png

Most of the data on my network is "download heavy", why can't I have higher ratios like 85/15 or 95/5 for example?

TCP-based download traffic requires TCP ACKs to be sent using the UL. In a PtMP network, there will be multiple TCP downloads going on, each requiring TCK ACKs being sent using the UL. Having enough time on the UL to allow multiple CPEs to send TCP acknowledgments, reduces the latency experienced by TCP, thereby increases the actual DL throughput.

 

As an example:

 

There are 50 clients connected to an AP. If 10 of these clients are simultaneously downloading and the UL allocation is extremely small like in 95/5, the UL time may only be enough to carry the TCP ACKs of one of the stations. The others will need to wait for their turn, which will arrive according to the TDD framing cycle. But during this time the TCP may stall its window and not send any further traffic until the ACKs are received. This causes underutilization of DL.

 

Hence extremely low UL allocations may end up reducing the effective throughput of the DL on larger PtMP networks.

Is GPS Sync built in or is there a cost associated with it?

GPS Sync is built in, there is no cost to use this technology.

Can I manage and monitor my LTU products with UNMS?

Yes, UNMS (version 0.12.0) offers basic monitoring for LTU products. Newer UNMS versions will support configuration of most important LTU settings. 

What is the maximum MTU size allowed by LTU products?

LTU products support Jumbo Frames up to 9000 bytes in the DATA interface. 

NOTE: ifconfig info will only display 1500 bytes because that command only shows MTU size for the interface connected to the CPU. Since DATA traffic pass through an ASIC, which is not displayed in the ifconfig command, it will not show real MTU size. Just make sure you set MTU value above 1600 and Jumbo Frames support will be enabled.
Does LTU support SNMP?

Yes, MIBs can be downloaded by clicking here.