Spring is one of the best times of the year to be at the Côte d’Azur in France. While the weather and landscape is great, France is really missing attractive prices for Internet access over 3G. Not really affordable for post-paid customers, nothing is available for pre-paid customers at all. A good opportunity to use my Vodafone Germany prepaid SIM card for Internet access via the WebSessions roaming offer.
Vodafone’s partner network in France is SFR and according to their web page, they’ve got HSDPA deployed in some parts of the network. Accordingly my speed expectations where high. And indeed, when I activated the 3G connection my data card showed that HSDPA is available in the network. Speed tests performed over several days revealed however, that the downlink speed is artificially limited to around 45 kBytes/s. The limitation is certainly not the air interface as the signal strength was good and speeds I measured in Germany and Italy were much higher.
It’s hard to tell from a users point of view exactly where the bottleneck is. It could be that Voda’s Home Location Register (HLR) in Germany and SFRs SGSN in France can not exchange the QoS profile correctly which subsequently leads to the throttling of my connection. It could also be that there is a limitation on the IP link used for forwarding my packets between the SFR network and the Vodafone Germany network. It’s also possible that the SFR SGSN or the Vodafone GGSN is unilaterally limiting my speed. In practice this means that HSDPA does not give me a great advantage in the SFR network over a 3G UMTS device as the speeds are the same. Due to this I was not sure if the connection was HSDPA at all. Subsequent tests described below showed, however, that the data card really got an HSDPA and not UMTS bearer.
After getting a 384 kbit/s uplink bearer in Italy and Germany I was also disappointed about the ‘meager’ uplink speed of only 128 kbit/s in the SFR network. It’s likely that this is no interoperability or throttling problem but a general network limitation of the SFR radio network. Either they haven’t activated the higher bearer option or it’s not yet available in the current software version of their radio network. Whichever it is they should consider upgrading or switching on the option as the difference is remarkable.
Round Trip Delay Times
One of the indicators that the data card got an HSDPA bearer and not a UMTS bearers were the round trip delay times. With the data card I got a round trip time of about 170 ms. HSDPA usually delivers a round trip time to an external host of around 120 ms (100 ms to the first hop). The additional delay is most likely due to international roaming which means that my data is tunneled from SFR into Vodafone Germany’s network before entering the Internet via Vodafone’s GGSN. With a Nokia N93 3G ‘only’ terminal I got round trip times of around 380 ms. I am not quite sure why there are an additional 200 ms of dealy as UMTS is usually only around 50 ms slower.
Radio Ressource Management
On the positive side I noted that the HSDPA radio resource management was more advanced than what I experienced in the TIM network in Italy and the Vodafone network in Germany. While the HSDPA bearer is active, the above mentioned round trip times to an external host of about 170 ms can be observed. In Cell_FACH state, which TIM and Voda’s network in Germany might not support yet, round trip delay time s were around 360 ms. This reduced activity state was only entered after around 45 seconds. After about 60 seconds the connection is put into Idle, Cell_PCH or URA_PCH state from which it takes around 800 ms to get back into active state. This is a lot quicker then the 2 seconds observed in Vodafone’s network in Germany and TIM’s network in Italy.
Skype, VoIP and IPSec
I tried Skype and my companies VoIP client over both HSDPA and UMTS and got crystal clear connections. Also, my IPSec tunnel worked fine between the notebook and my company. Very well!
Except for the artificially throttled speed, my experiences in the SFR network with the HSDPA card were very positive. I should also note, however, that some Wifi operators such as Orange have moved forward a bit as well and are now offering 10 hours online for 15 euros. The 10 hours can be distributed over 30 days. For 15 euros, one can stay online for several days if the connection is only used for a couple of hours a day. For me a Vodafone 24h WebSession for 15 Euros is still better because I am online for more than 10 hours a day. Also, I need access at different locations throughout the day which is difficult with Wifi hotspots. People with less online time and stationary use, however, might find a 10h over 30 days for the same price more attractive. Also, they are not limited to 50MB of traffic per WebSession Vodafone intends to introduce in September.
P.S. For more articles on this topic, click on the HSDPA link next to the date below