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Multi-Dwelling Unit (MDU) Network

Althea is well suited for a Multi-Dwelling Unit (MDU) network. This topology works well for apartment buildings, townhomes, multi-tenant office buildings, and similar properties. The primary characteristics of an MDU are residents/tenants of a building, generally sharing interior walls and/or a common roof. Some MDUs are pre-wired while others will require separate wiring.

This article will explore both a simple MDU existing in a single building and a complex MDU, spread amongst a campus of buildings.

Simple MDU

For the purpose of this article, a simple MDU example is a single building with one set of exterior walls, many interior walls, and a single flat roof.

ROOF/MPOE Components

Backhaul: For a simple MDU, a typical arrangement is to install a non-penetrating roof mount on the flat roof, with a single incoming radio. A 60 GHz radio, like this one, or a 24 GHz radio will function best in this capacity, but a 5GHz radio can work in a pinch. The radio should ideally be a Point-to-Point, not a station on a Point-to-MultiPoint. This radio will serve as the wireless backhaul. If it is financially feasible to get a Dedicated Internet Access (DIA) fiber connection to the building, this is even better. In either case, the backhaul should be capable of handling at least 200 Mbps symmetrical traffic, with low latency.

Note: A basic CPE radio, like a Litebeam, is not suited to handle a whole building’s worth of traffic. A radio with a fast enough CPU to saturate the link capacity is required.

TELECOM CLOSET/ENCLOSURE Components

Router: Immediately downstream of the backhaul radio or fiber, you will have an Althea router. For the purposes of this article, we’ll refer to this as the “central relay router”. The minimum spec for this would be a Linksys 3200ACM or Linksys 32X. Those routers will smoothly handle the traffic from about 10 downstream users. If the building has more than 10 downstream users (or has very heavy data throughput requirements), we recommend a more powerful router, such as a Protectli with i7 CPU instead. This router will be the bottleneck for the whole building, so you want it to be fast enough to handle the traffic it needs to process and forward. Typically this router does not need WIFI, but there may be some situations where WIFI is useful (such as future maintenance, or connecting wireless security cameras).

This router can be owned and operated by the building owner, the ISP, or a 3rd party such as a managed IT firm. It can be configured to earn income as a relay router within the Althea network.

If this router is offline for any reason, the rest of the building will be offline as well.

Switch: Immediately downstream of the Althea router, you will likely need a switch (unless your Althea router has enough internal ports). This switch should be plugged into a MESH port on the Althea router. It will simply function as a ‘port expander’, providing more ports for your downstream users to plug into.

Both managed and unmanaged switches will work in this context. An unmanaged switch is simpler and less expensive, but may result in slightly slower performance if there are many downstream devices. A managed switch provides more options for segregating traffic, which may be important in some business environments. A managed switch may also provide slightly better performance, but in most cases this is fairly negligible.

Firewall: Since Althea routers encrypt all traffic end-to-end (and operate a firewall at the exit node), no firewall is needed. In fact, adding a firewall is likely to break the network, as it might block the ports that Althea routers need to communicate with each other.

Misc: We highly recommend an uninterruptible power supply (UPS, a.k.a. backup battery) system be installed to provide continuous power to all components in the network cabinet. If the UPS system has a webGUI, it can be plugged into a MESH port on the Althea router and accessed remotely via Althea Operator Tools: Antenna Dash feature. This enables easy remote access (no VPN needed!). More information regarding the Op Tools Antenna Dash feature can be found here. If the UPS system has its own cloud management software, you can instead plug it into a LAN port on the Althea router to provide it with standard internet access, and use that cloud software normally.

If the enclosure is outdoors or in a poorly ventilated space, you may also need to add fans or some other climate control system. Generally basic 12V DC computer fans are sufficient, and if sound dampening is important, opt for larger 80 - 120mm fans when possible.

Electrical Grounding: It is vitally important that all of the network equipment have a proper electrical ground. Many older buildings are grounded improperly, so in some cases you may need to install your own grounding solution (i.e. a grounding rod outside, with a ground cable running to the network cabinet). Consult with a local electrician and your local electrical code for grounding requirements. If you install network equipment without a proper ground, it is likely to fail prematurely and suddenly, due to electrical surges and/or buildup of static electricity.

Cabling: Downstream of the switch, the building will need cabling running to each unit. If you are running new cabling, we recommend shielded CAT6 cabling, such as Shireen DC-2021. This spec of cabling supports up to 10 Gbps, so it helps to future-proof the building. The shielding also helps protect the cabling from interference from nearby AC electrical cabling, as often the data and power cabling needs to be run side by side. Also consult your local code, as some buildings may require Plenum rated cabling (this refers to a fire safety rating in the cable’s insulation, as some cabling can release toxic gases in a fire). Note that the cabling can also go ‘out, around, and in’ meaning that the bulk of the cabling can be on the outside of the building as needed.

If the building has existing cabling, check the spec of the cabling, which should be printed in small lettering along the side. CAT5E is likely OK to use as-is. CAT5E is rated for up to 1 Gbps, but in many cases it is installed improperly, or a very cheap grade of cable is used, and the real-world speeds are much slower. You can use a tool like iperf to test the speed of a cable from end to end, and you can use cable testers as well to test continuity.

If the building has CAT5 (not CAT5E) cabling, this should be avoided. CAT5 cabling has a maximum throughput of 11 Mbps, and in the real world it is often much less. So it may be appropriate to use for low throughput devices like printers, but it won’t work well for Althea routers.

CAT3 (a.k.a. telephone cable) cannot be used, it is simply too slow, and doesn’t have enough wire pairs to support the Ethernet standard.

Many buildings are pre-wired with COAX (a.k.a. cable, what is used for cable TV and internet). COAX can be used with Althea networks, it just requires COAX media converters at either end of the cable. To get the most out of it, you’ll want MoCA 2.5 adapters at either end of the COAX cabling, to convert between COAX and Ethernet. These adapters can be fairly expensive, but the total cost may still be less than rewiring the whole building. The use or replacement of COAX should be handled on a case-by-case basis.

END USER UNITS

Each unit in the building will have one endpoint Althea router. Many users may refer to this as a ‘modem’, which is technically incorrect, but hey, work with what people know. This Althea endpoint router will connect to the building’s wiring with a MESH port. This will allow the endpoint router to talk with the central relay router, and negotiate an internet connection. The endpoint router will also pay the relay fee to the central relay router (if configured to a non-zero amount) for data usage. The endpoint router should only need a single MESH connection to the building wiring, the rest of the ports can be LAN for the user’s hardwired devices (TV, game system, desktop PC, etc).

WIFI:

WIFI in an MDU can be challenging, because the units are likely packed tightly together, so WIFI interference is likely. Some suggestions to help mitigate this are as follows:

  • Check the Althea Operator Tools router tab for detailed information about the WIFI devices. You’ll find information about the user’s device signal strength, noise floor, packet failures/retries, etc. This data can help you determine if the problem is localized to the user’s WIFI environment, or some other issue unrelated to WIFI (such as a faulty cable).
  • Alternate WIFI channels between adjacent units. If the units are all in a row (like townhouses), follow a pattern like this - Unit 1, Channel 36; Unit 2, Channel 100; Unit 3, Channel 149; Unit 4, Channel 36; Unit 5, Channel 100; Unit 6, Channel 149; etc. Basically just try to space out the channel reuse as much as possible. Note that some routers only support 2 channels.
  • 5 GHz WIFI has much lower range (and lower wall penetration) than 2.4 GHz WIFI. Consider disabling 2.4 GHz WIFI on routers that don’t need it. Some older devices only support 2.4 GHz WIFI, so if the user has older devices this may not be an option.
  • Hardwire as many devices as possible, especially heavy data use devices like smart TVs and gaming systems.
  • Consider using endpoint routers that have weaker WIFI antenna gain, to limit the range and subsequent interference from each one.
  • Be mindful of the proximity of WIFI routers in adjacent units. For example, it is a common and logical cabling technique to run CAT cabling into a single wall, then add Ethernet outlets on either side of the wall for Units 1 and 2. This means that the routers plugged into those Ethernet outlets are likely to be back to back, with only the shared wall separating them. In this scenario, make sure that both routers are broadcasting on different WIFI frequencies, and move the routers further away from the wall where feasible.

Building-wide 3rd party WIFI Mesh:

In some cases, a building-wide WIFI Mesh may be desirable. This entire mesh could be treated as a single Althea endpoint, which makes sense if the mesh is to be used for building monitoring systems like security cameras. In this situation, the central WIFI mesh node would be plugged into the LAN port of an Althea router (which could be either an endpoint router or the central building router, depending on the billing requirements).

Althea WIFI Mesh:

There is support for an Althea WIFI Mesh, in which each Mesh node operates as a separate Althea endpoint and wirelessly connects to nearby Althea nodes. The benefit to this approach is that each WIFI mesh node has its own separate billing. The downside to this approach is that the overall performance is much slower, as each WIFI mesh node needs to dedicate some of its WIFI time allocation to communicating with other nodes (and not with the user devices). We consider this approach experimental.

Complex MDU

For the purpose of this article, a complex MDU will consist of a ‘campus’ of multiple buildings, each with separate exterior walls, separate roofs, and likely walkways between structures.

A more complex MDU is best approached as a collection of simple MDUs. Everything written above still applies, but an extra layer of networking is required to interconnect the buildings to one another.

Wireless bridges:

To connect existing buildings, likely the most cost-effective solution is wireless bridges. Assuming the distance between buildings is relatively small (much less than a mile/kilometer), a 60 GHz wireless bridge is an excellent option. They are generally inexpensive and perform very well under short distance and perfect line-of-sight environments. Each building could host one or more 60 GHz radio on a non-penetrating roof mount, or wall mounted as needed. CAT6 or better cabling is highly recommended, as many of these products can exceed 1 Gbps throughput, so you want your cabling to handle 10 Gbps throughput. You can think of a wireless bridge as just a long Ethernet cable, so Althea routers can interconnect with wireless bridges via MESH ports.

Underground cabling:

In some situations such as new construction, trenching underground cabling in conduit is a better solution. Note that CAT6 cable has a maximum length of 330 ft / 100 m, so in many situations fiber is needed to cover greater distances between buildings. We recommend keeping CAT6 below 250 ft / 77 m whenever possible. Conduit is highly recommended, so the cabling can be maintained and replaced in the future if needed. Consult your local building codes regarding underground low voltage (CAT6) or non-electrical (fiber) cabling.

Aerial cabling:

Aerial cabling is also a possibility, with the same maximum length restrictions. Aerial cabling is generally more exposed to environmental damage, so underground cabling is preferred whenever possible.