We have a book exchange shelf at work where people can put books they no longer need and can take out other books in exchange. Recently I found the “Cellular Travel Guide”, a 1000+ page book published in 1993 that is about how to roam in the US with your mobile phone. A fascinating historical read that takes you back 20 years to a mobile world that hardly seems real from today’s perspective.
Continue reading The Cellular Travel Guide – Back in Time to 1993
I have an 802.11ac wave 1 capable router at home that supports an 80 MHz channel in the 5 GHz band. Unfortunately all my PCs are only 802.11abgn capable and the best I ever got out of the 40 MHz channel to which 11n devices are limited on 5 GHz through one wall was around 70 Mbit/s. I always thought it should have been more, given that my Thinkpad X230 with an Intel 6205 Wi-Fi card was pretty much on the high end of the price scale in 2013. So when I recently had a chance to put a current Skylake based Dell E5570 notebook with an Intel 8260 802.11ac chip in the same physical location I expected to see around twice that throughput as it can make use of the full 80 MHz channel. What I measured, however, took me quite by surprise.
Continue reading An 802.11ac vs. 802.11n Speed Comparison in a Real Life Scenario
I’ve been doing a lot of intercontinental traveling lately. Especially during day flights and for the long jet lag nights where nothing productive springs to mind it’s good to have an entertaining book at hand. For a long time I was a bit despaired when it came to techno thrillers because most main stream writers just don’t get the technology right. But then I’ve found ‘Indie’ (independent) authors and lots of interesting books that get the technology right. My latest discovery is Andrew Updegrove’s ‘The Alexandria Project’.
3GPP is putting a lot of meat on the bones these days to the 5G New Radio (NR) study item. In the recent edition of TS 38.801 (Study on New Radio Access Technology) I read that the base station in 5G New Radio (NR) will be referred to as gNB. Unfortunately it is not mentioned what the ‘g’ actually stands for!?
Continue reading 3GPP 5G NR – What’s the ‘g’ in gNB all about?
Back in 2014 I had a peak experience in global roaming. LTE was becoming available everywhere I went across the globe, my smartphone supported most LTE bands in Europe, the US and Asia and my mobile network operator of choice started a global roaming offer. While the roaming offer ‘only’ includes 150 MB for a week for around 12 Euros (infinitely re-bookable) it has made me independent of crappy Wifi connectivity at hotels and meeting venues and of the hassle organizing a local SIM card. Unfortunately since that time my operator had to make a few exceptions to that global data roaming offer and Vietnam, the country I recently visited was unfortunately among them. At 80 cents per 50 kbytes of data, switching mobile data on even only for checking emails was absolutely out of the question.
In an earlier post I had a a look at the different options for Cellular IoT (NB-IoT) when it comes to connectivity. One of the options is to use the cellular control plane to forward the raw data without wrapping it into IP data packets (NIDD, Non-IP data delivery). At the time I wondered a bit whether that would be a good idea. But perhaps it actually is!?
The LTE air interface uses Orthogonal Frequency Division Multiplexing (OFDM) to transmit many slow data streams (1200 in a 20 MHz carrier) in parallel to achieve a very high overall speed. OFDM is not exclusive to LTE, it is used in many other systems such as Wifi and DSL as well. For more details have a look at this post from back in 2007. One thing not contained in that earlier post is how each of the 1200 slow data streams is actually transmitted. In good signal conditions 64QAM is used in the LTE downlink direction. So what is 64QAM and how does it work? Continue reading An Introduction to QAM Modulation for LTE
When I was recently in China, it was an ideal opportunity to have a look at the ratio of downlink and uplink timeslots in a real network. The standard is quite flexible in this regard and offers many options so I was not quite sure which option would actually be used in practice. Continue reading TD-LTE – Number of Uplink Timeslots Observed in Practice
It’s been a while since I read a good techno-thriller with a believable plot from an author that gets the technology right. William Hern’s Chronos is a book I enjoyed and so was The Billion Dollar Heist by Ben Lovejoy and Marc Russinovich’s novels like Rouge Code are also great examples. Now I’ve found another author and book that falls into this category, Andrew Diamond with his latest book Impala.
In a previous post I’ve looked at 3GPP band 46, the band number assigned in 3GPP Release 13 to the 5 GHz band currently mostly used by Wifi only. So how pristine is this beachfront property today? Let’s have a look at my place in Cologne and compare it with use of the 2.4 GHz band.