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
TD-LTE – Number of Uplink Timeslots Observed in Practice
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
Book Review – Impala
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.
2.4 GHz vs. 5 GHz Use In Practice Today
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.
The 5 GHz Wifi Band Has a 3GPP Band Number Now
License Assisted Access (LAA) is the term in 3GPP to potentially use the 5 GHz band, which is mostly used by Wifi networks today for LTE in the future. It looks like 3GPP has made a jump forward on the topic as the band has received a 3GPP band number in TS 36.101. It’s already in 3GPP Release 13 but a number of extensions in 3GPP Release 14 make it a special kicker.
Continue reading The 5 GHz Wifi Band Has a 3GPP Band Number Now
Book Review – Dealers Of Lightning
Last year I had a great time reading ‘The Innovators’ by Walter Isaacson, a wonderful book that spans computing history from Charles Babbage and Ada Lovelace to our days. There are a lot of stories inside the book and each can only be a short summary of events. That’s why I also enjoy reading books about particular parts of computing history, and ‘Dealers of Lightning’ by Michael Hiltzik on the history of personal computing at Xerox PARC is just one of those.
From Dipole to Active Antenna Systems and 4×4 MIMO
Recently, T-Mobile US has announced that they have switched on 4×4 MIMO support in their network and first smartphones are now supporting 4 simultaneous downlink streams. Quite an interesting announcement as most antennas and base station sites currently deployed by most operators do not yet support this. So let’s have a look at what has changed in recent years in base station technology.
Continue reading From Dipole to Active Antenna Systems and 4×4 MIMO
Cellular IoT – Part 10 – 10 Years Battery Lifetime
Another NB-IoT number floating around is that very power efficient NB-IoT devices should be capable to be driven from a small battery for more than 10 years without needing a recharge. Again, I wondered where this number comes from and which assumptions were made to declare that this is possible.
Continue reading Cellular IoT – Part 10 – 10 Years Battery Lifetime
Cellular IoT – Part 9 – 50.000 devices per cell
There is an interesting number floating around in various whitepapers and articles on IoT: NB-IoT supports 50.000 devices per sector per cell. So where does that number come from and is it realistic?
Continue reading Cellular IoT – Part 9 – 50.000 devices per cell
Elisa reports 5 GB data use on average per user per month, 13 GB during the olympics
Back in July, DNA/Elisa of Finland reported that their average user consumes 5 GB of data per month.
Personally I don’t do a lot of video streaming while I’m on LTE so my current data consumption on my smartphone is around 1.5 GB a month these days, so you can imagine how much streaming must be going on in Finland.