Cisco EPC3010 EuroDOCSIS Modem

This is a basic teardown of my old cable modem.

The EPC3010 was the basic modem supplied by Get.no, a former cable internet/TV supplier that was bought out by Swedish telecom giant Telia.

EuroDOCSIS 3.0

EuroDOCSIS is a European adaptation of the American DOCSIS standard for providing digital network services over a relatively standard cable TV network.

A version 3.0 system provides around 1 Gbit/s download and 200 Mbit/s upload, this bandwidth is shared among all consumers on a single network. It is not uncommon for e.g. apartment buildings to have one or more networks to provide sufficient bandwidth. This was quite good when introduced (2006 or so), but is starting to show its age these days.

The standard is extensive, requiring all elements in the chain to be suitable for this purpose, in particular the issue with doing two way communications over a cable TV network is that older networks have unidirectional distribution amplifiers. To implement a two way system each distribution amplifier has a diplexer, separating plant-consumer and consumer-plant traffic, allowing the "return channel" to be transmitter back to the cable provider.

Version 3.0 and earlier were intended to support interoperability with cable TV (analog, and later digital DVB-C or similar in Europe). As such they operate with a concept of channels, whose bandwidth is still compatible with 1950s era TV channel bandwidths. EuroDOCSIS uses European TV channel bandwidths (8 MHz) as opposed to American ones (6 MHz), there may be other minor differences as well.

A fundamental limit of DOCSIS is in the allocation of frequencies, which affect e.g. the amplifiers. In v3.0 there are only 4 return channels allocated, and a significantly higher amount of forward channels, resulting an asymmetrical bandwidth. There is also typically a limitation on the complexity of the return channel modulation complexity; higher complexity modulations increase bandwidth but drive up modem costs. The plant end of the link is shared so is generally allowed to be more expensive.

At the time of writing Telia is working on introducing DOCSIS 3.1 (something they market as Hybrid-Fiber). The fiber-part connotes the speed of the link, allowing for 1000/500 Mbps or so per consumer (competitive with current common fiber link speeds for consumers). The total bandwidth of DOCSIS 3.1 is around 10/1-2 Gbit/s, and it still uses a limited set of channels.

DOCSIS 4.0 is even more current but not yet being installed in Norway to my knowledge; this standard offers 10/6 Gbit/s by removing the legacy TV channel support and allocating the entire cable bandwidth to data traffic. This likely requires far higher distribution system complexity, possibly eliminating the concept of signal splitters entirely and instead moving to a directly wired network. It is at this point that replacing the final 10 meters of coax cable with fiber might start to make sense.

For reference a fully built fiber system can (at present) do around 400 Gbit/s symmetrically per wavelength, so claims of "fiber speed" are temporary at best. Common and cheaper PON fiber systems offer performance similar to DOCSIS networks however.

The EPC3010

My EPC3010 is from around 2012, though I probably got it in 2014 or 2015. I went through a fair amount of these for a while, primarily due to power supply failures. At some point I simply replaced the power supply with a 3 A rated one, which kept it working since.

This is a pure modem, with a single Ethernet port, per some de facto standard it is reachable at address 192.168.100.1 provided your router sets up proper routing tables.

Typical gateway latency with this modem was around 5 ms on a good day, which is quite good, the replacement modem I have increased this to 10 ms.

I had issues over a few months/years with periodically high latency solved by rebooting the modem, and upon finally contacting Telia I was offered a new Sagencom modem (actually a router, but it has bridge mode). I was then told I could throw the Cisco in the trash, and (paraphrasing) that they under no circumstances wanted that piece of trash back.

The teardown pictures are shown in the gallery above.

The power supply circuitry is built using MP2307 DC/DC converters, these are pretty decent and offer synchronous rectification, improving efficiency. Capacitors still look fine.

The main boy is a Broadcom BCM3380 "QAMLink" SoC. This device includes the entire RF-chain except for an external diplexer and LNA for the receive path.

This device is limited to 8 downstream and 4 upstream channels, which is likely what limits the total performance to up to 320/160 Mbit/s. This is marginal for download, given my current nominal 250 Mbit/s download, but well within margins for my pathetic 20 Mbit/s upload rate. It is worth mentioning that this less than 10% upload rate is their extended upload package, the standard package offers 10 Mbit/s.

The new Sagencom appears to support 16 or more downstream channels, likely making it capable of 1 Gbit/s downloads in theory.

The RF diplexer is pretty standard, using a BCM3410 LNA as expected.