5G EN-DC: What is Single Uplink?

The abbreviation EN-DC (eUTRAN New Radio – Dual Connectivity) indicates that in this type of 5G deployment, 4G LTE and 5G NR will be used simultaneously. However, it looks like that the combination of some frequency bands might prove to be a bit problematic due to self interference as laid out in this interesting whitepaper recently published by Keysight (see page 4).

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VDSL and G.Fast Coexistence

A few days ago, there’s been a great talk about G.Fast at the Local Chaos Computer Club chapter (C4, Cologne) by Stefan Förster of NetCologne. Here’s a link to the video of the talk (in German). I was particularly interested, because NetCologne recently announced that they have finished their G.fast trial (using the existing telephony copper wiring in buildings) and are about to start commercial service. This sounds like great news and I had quite a number of questions in my mind, including how G.fast can coexist with VDSL Vectoring that the the national incumbent offers in Cologne today.

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5G – Supplementary Uplink for EN-DC?

I couple of days ago I was wondering what Supplementary Uplink (SUL) for 5G is all about, if it is supported for EN-DC (simultaneous LTE+5G data transmission) and what potential benefits it might have.

I can pretty much understand how SUL would help for 5G standalone operation, let’s say on 3.x GHz. The problem here is the limited uplink transmission power of mobile devices which will be the limiting factor when it comes to cell range. The idea of SUL is to add an uplink transmission path on a lower frequency band that can reach farther. Also, it could increase 5G uplink transmission speeds, because I assume that in TDD operation, most operators will give as much of the 3.x GHz carrier capacity as possible to the downlink.

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Telefonica Germany Blocks Data Roaming On Ships

One thing that I think borders on modern (digital) piracy are the charges for data roaming on board of (some) ships. Cellular on-board networks are often connected via satellite and typically, 1 MB of data transfer, which is barely enough to load the front page of a web site these days, is charged in steps 1 euro per 50 kb. In other words, a single web page costs 20 euros to download. No sane being on this planet would ever want to do that so I assume that 99.9% of the revenues generated that way are from people who’s mobile automatically registered to the on-board network when it looses contact to the land based network for a while.

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What Happens When a User Runs Out Of Disk Space On Ubuntu?

Full Disk StatsWhy would anyone ever need then 640k of RAM? How could one ever fill a terabyte disk? There are orders of magnitude between those questions but both limits were easily surpassed just a few years after those questions have been asked. At the moment, a user of one of the computers I administer is approaching the second limit and I am not so sure my attempts of preventive persuasion to move some data to another disk is having the desired effect. So what happens when the disk that holds the user’s directory becomes full? Will programs just freeze? Will the computer still boot? Will suspend/resume still work? Will the user still be able to logon? Will the world come to an end?

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LTE at Sea

LTE - Measurement 1I recently took an overnight trip on a ferry from Gothenburg, Sweden to Kiel, Germany. While they were advertising free Wifi on board, which, not to my surprise, totally failed during the trip, I was looking forward to finding out, if and when I could reach the land based LTE network and get connected. As the ship ventured quite far from land, I wasn’t very hopeful that things would work well.

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DSL, Vectoring and Line Length

Vectoring SNRAfter the line of my neighbor has been switched to a different port in the street side DSLAM and mine followed a couple of days later, I finally have a stable DSL line again. There are many factors influencing the maximum uplink and downlink speed that can be achieved over a copper wire and since I’m pretty much as far away from the DSLAM as is possible in the center of Cologne, I think my line characteristics and performance gives interesting insights of what’s possible in densely populated areas.

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5G EN-DC: Flow Control Between 4G and 5G

One thing I’ve been wondering for some time now is how in 5G EN-DC, user data is split between the 4G and 5G base station in a way that takes changing RF conditions into account. It’s no good to just assign a certain data rate to the 4G and 5G side when a split bearer is initially established, as achievable speeds over the air interface can change very quickly. In other words, there must be some sort of throttling mechanism.

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Long Before The Matrix – Die Welt Am Draht

Long before ‘The Matrix’ (the movie) was released in 1999, there were a number of other books and movies about people living virtual lives in virtual worlds. A couple of months ago I was recommended to watch ‘Die Welt Am Draht‘ (link to Wikipedia in German and English). A 1973 movie by Rainer Werner Fassbinder, available on Youtube (see here for a trailer with English subtitles), it is about worlds simulated in computers occupied by conscious beings that are unaware that they are just a simulation. Well, that is, all except a few and those that are, are quite unable to deal with their knowledge. Sounds very much like Matrix but 25 years earlier! The movie is based on the book Simulacron-3, written in 1964 by Daniel F. Galouye and seems to be quite faithful to the book’s original story.

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