Martin – Page 39 – WirelessMoves

Antenna Games & Anti-Static Bags

When working on radio related things in a lab, there are usually shielded boxes with antenna connectors and attenuators, so it’s easy to simulate bad RF conditions. That’s quite useful when testing how devices behave under such conditions. Recently, I wanted to see how a router with an LTE modem behaves when RF is bad from home, so I had to come up with a different approach: Anti-static bags.

My ffmpeg Cheat Sheet for Video Transcoding

One of the reasons I bought a used Z440 workstation with a 6 core Xeon CPU and an Nvidia graphics card back in December was to offload and speedup occasional video transcoding tasks. As I wrote at the time, I could get a speed-up of up to 8x over my X250 notebook. Since then I have found further parameter improvements for ffmpeg and in some scenarios, my speed-up is now over 30x compared to running the same task on my notebook.

Wondershaper, SSH and the TOS field

In the previous post, I’ve been looking at Wondershaper, a great script that uses the Traffic Control (tc) command to counter buffer bloat situations. The main mechanism to do that is to set the maximum transmission and reception rate of an interface slightly below the available line rate, and thus prevent large transmission buffers to fill up and create unacceptable delay. But Wondershaper does a lot more, such as preferring packets of interactive SSH session over other data packets. When I had a look at how this is done, I was quite surprised that the packets were not preferred based on their TCP port number.

Wondershaper In Action

In well-built networks with lots of capacity on all links between source and destination, even fully loaded links behave nicely and packet delay remains acceptable. In some scenarios, however, particularly when the bandwidth on the last leg is low, and packet buffers on some routers in the network are overdimensioned, packet delay becomes a real issue. When transferring larger files, bufferbloat quickly sets in, and applications such as interactive shell sessions, web browsing and voice calls become unusable. When I was recently faced with such a situation, I found an interesting traffic shaping tool that fixed the problem: Wondershaper.

3G Switch-Off and Conversations

In just 6 weeks from now, two of the three German wireless network operators will switch-off their 3G networks. This has long been in the cards and gave me a bit of a worry. This is because I run LineageOS on my personal smartphone, and since it has a somewhat esoteric chipset from a LineageOS point of view, its unlikely to ever receive a software update with the Voice over LTE (VoLTE) stack activated.

Remotely – Part 2

In my first post on the topic, I’ve given an introduction to ‘Remotely‘, an open source and self-hostable remote support solution for Windows and Linux. I came away quite impressed but noted that in my virtualized setup, the connection to a supported device was often interrupted due to unknown reasons. Also, I hadn’t yet tried to run the dockerized Remotely server behind a reverse proxy, which would be a nice thing to have to benefit from https encryption and automatic Letsencrypt certificate updates. Since then, I had the time to work on my setup some more, and here are the results.

Voice over NR Whitepapers

Now that the non-Standalone (NSA) flavor of 5G has been pretty much established around the globe, it is likely that more focus is put on the 5G standalone (SA) flavor of the technology. In effect that means two things: Instead of using LTE as an anchor for a 5G air interface connection, 5G can stand on it’s own feet. This requires a 5G core network (5GC) with a radically new service based architecture. One existing application that needs to be supported over 5G SA and the 5G core network is of course voice. This means that Voice over LTE (VoLTE) needs to evolve to Voice over NR (VoNR). Rohde & Schwarz has recently published great whitepaper on the topic which I liked very much, so I thought I’d say a few words about the topic here.

Remote Support with a Self-Hosted Remotely Instance

I’m always on the lookout for solutions to improve my remote working and support capabilities and recently came across ‘Remotely‘, an open source and self-hostable remote support solution for Windows and Linux. Self-hosted and open source, hm, sounds interesting, I thought, just what I like for privacy and confidentiality reasons. So I had a closer look!

Stress Testing Guacamole

In the previous post, I had a look at Guacamole, an open source client-less remote desktop gateway. It’s a cool piece of software and I have already used it with 12 people connecting to the same number of workstations in the cloud. In this setup, the central Guacamole server that I equipped with 8 vCPUs hardly required any CPU resources at all. However, most of the time, not much was changing on the remote desktops, so my scenario was not very demanding. So while that’s good to know, I wanted to know the limits of my 8 vCPU setup, so I stress tested my setup. A fun experience!

Command Line Heroes – Season 7

Wow, it’s only a year ago since I was three years late to the ‘Command Line Heroes‘ podcast. In case you haven’t seen my post then, ‘Command Line Heroes’ is a podcast about, well, the title says it all. Ever since it’s first season, the show’s host Saron Yitbarek has looked at people and coding related topics, and it’s hard not to listen to a new episode the second it pops-up in my podcasting app. Season 7 has just started, so I thought I’d mention it here, and it is all about how the Internet became what it is today. Highly recommended, as it’s a wonderful mix of history and thoughts how the past has shaped what we are working with today.