When using a Wifi network at home for voice telephony everything’s great and shiny as long as there is enough bandwidth for the call. But when you are stuck on a Wifi connected to a slow DSL line that has only little uplink capacity and someone else on the network starts uploading cat images, things … Continue reading Simulating Delay and Packet Loss
One approach to deploying LTE without packet switched voice call functionality at the beginning is to instruct mobile devices to use a 2G and 3G network when the user makes or receives a voice call and return to LTE afterwards. This solution is referred to as CS fallback and has been specified in 3GPP TS … Continue reading CS-Fallback – An Introduction
I heard somewhere, but forgot exactly where, that the German C-Netz mobile network back in the 1980's was the first network that separated subscription from device via a SIM card. Since then we've come a long way and all major mobile network standards these days have implemented the concept. From my point of view this … Continue reading Decomissioned SIM Cards
In an ideal world you take your notebook wherever you want and that built in 3G modem or USB dongle gives you access anywhere. That pretty much works today while you stay in the country of the network operator you are with. As soon as you move out of the country, however, hyper expensive roaming … Continue reading A Prepaid Broadband SIM without an APN
I've arrived in Florida and since I will stay for a couple of days I went to the AT&T store around the corner to get a prepaid SIM for mobile Internet access. Good timing on AT&T's side since they introduced an unlimited mobile Internet access package for $19.99 per month just a couple of weeks … Continue reading Online with an AT&T Prepaid SIM
After some basic tests to see how HSDPA performs in a number of different networks I’ve now moved to a number of somewhat more complicated scenarios. The last article in this technical series on HSDPA focused on network and terminal HSDPA behavior for an incoming call. This article shows how the network behaves when several … Continue reading Network Behavior For Several Simultaneous Users In An HSDPA cell
Both WiMAX and the UMTS successor technology LTE use Orthogonal Frequency Division Multiplexing (OFDM) as the core modulation technology on the air interface in downlink direction. In uplink direction, however, the two systems go different ways. While WiMAX uses OFDMA (Orthogonal Frequency Division Multiple Access), the 3GPP (3rd Generation Partnership Project) standardization group has decided … Continue reading An Introduction To SC-FDMA Used By LTE In Uplink Direction
The Times ran an interesting article this week about new data tariffs introduced by mobile operators. While mostly highlighting prices for contracts, they also mention at the end of the article that Orange and T-Mobile U.K. are also offering web access via their prepaid pay as you go SIMs. That’s great news for three reasons: … Continue reading U.K. Operators Now Offer Mobile Access To The Internet With Prepaid SIMs
I’ve dedicated well over 15 months of my quality time into my latest project and now it’s finally done and available in book stores around the world: Therefore, I am proud to announce general availability of the book to this blog "Communication Systems for the Mobile Information Society", published by John Wiley & Sons. If … Continue reading The Book to this Blog: A Solid Introduction to Wireless
It’s March 2024 and for the first time in 5 years (thank you Covid pandemic), I was in the US again. So far, so good, but there is one significant difference this time, at least from a technical point of view: For the first time ever, I’m roaming with Verizon! Most travelers won’t even notice, … Continue reading Roaming Report – Part 1 – Roaming with Verizon – A First!