Macro Offload, Voice over LTE and Bzeek

Macro network offload has been one of the hot topics at the recent Mobile World Congress in Barcelona. 3G and LTE femtocells are one interesting way to move voice and data traffic from cellular macro networks to fixed line connectivity in homes and offices. Another equally interesting possibility is Wi-Fi and it has some advantages as well.

Wi-Fi is the air interface of choice today for office- and home networking and is widely supported on smartphones as well. However, it still misses some features for the purpose:

First, what's still missing are intelligent clients on mobile devices that automatically switch over to Wi-Fi whenever available. In an ideal case the IP address and all open TCP and UDP connections would be kept when switching between the 3G / LTE macro network and Wi-Fi. For seamless switching, an IP sec tunnel or similar would be required on the Wi-Fi side. It would also be a good remedy for the inherent security issues of non-encrypted hotspots. Not impossible but also not straight forward to implement either.

Another thing that is missing is voice capabilities over Wi-Fi. One the one hand this would help to offload further traffic from the macro network. On the other hand, Wi-Fi networks could be used as an extension in areas where the macro network can't reach.

And finally, what comes to my mind is that Wi-Fi networking is very diverse. While the phone could be pre-configured for a network operator's Wi-Fi and the private Wi-Fi at home, using a wireless network at a friends house or at another office requires some user interaction. Not the best thing to make this work.

While built in intelligent “switching applications” are likely to be only a matter of time before they appear, the other two things are a bit more tricky to pull off. On the voice front, VoLGA and its brother technology GAN (Generic Access Network) might hold an interesting answer. Kineto demonstrated their Voice over LTE via Generic Access solution over a real LTE network in Barcelona and since it's based on GAN, it can easily be adapted for Wi-Fi as well. VOLGA for voice calls while the mobile device has LTE coverage, GAN while the Wi-Fi network is near and standard circuit switched voice calls while under 2G or 3G coverage, all seamlessly integrated into the device without too much effort. From application layer down to the protocols, all is the same, independently from the access technology. Only the lowest layers require adaptation. A straight forward solution.

And for using Wi-Fi at a friends house seamlessly, Bzeek might hold the answer. The software from an Israeli start-up company transforms your PC at home into an access point to share your Wi-Fi network with friends.

Interesting possibilities, but agreed, it's still early days when it comes to intelligent off-load.

3G vs. Wi-Fi – Then and Now

The battle continues… I can still remember, it must have been 5 or 6 years ago when there was a big debate over which system would win, UMTS or Wi-Fi. It was a strange debate, as even then it was clear that Wi-Fi aimed at homes and hotspots while UMTS aimed for wide area coverage. The whole municipal Wi-fi wave only came and went a couple of years later. Today, Wi-Fi is used ubiquitously in homes and as far as the Wi-Fi hotspots in Europe and elsewhere go, they are held mostly alive by high roaming charges and better coverage where no 3G in-house coverage is available. Also, there are some niche opportunities like for example in trains. I'd say it's a peaceful co-existence today.

As mobile networks are getting more and more traffic these days, the discussion seems to stir up again, this time against the background of whether UMTS femtos or Wi-Fi is better for 3G macro network offloading. In the end, I'm sure peaceful co-existence will prevail. Once femots are nicely integrated together with today's Wi-Fi access points that include an access device (think DSL, coax or fiber modem), the re-merger of fixed and wireless network operators will open the door to femto acceptance in homes. And as far as public hotspots are concerned I think combined devices also make the most sense, especially if the Wi-Fi hotspot operator is also a UMTS network operator.

So even in this area, I see a peaceful coexistence for both technologies in the long run.

Mobile Multitasking

David Wood recently wrote an interesting post on why he thinks multitasking on mobile devices is not only nice to have but rather despite still not all smartphones support it today. However, Symbian based devices have supported this for many years and it's one of the reasons why I'm a Nokia N- and Eseries fan boy. But let's put it to the test, which programs am I running simultaneously on my mobile (see picture on the left):

  • Profimail to receive e-mail.
  • The phone configuration utility. Always running so I can get quickly to some often used functions such as 2G/3G network selection, call forwarding, etc.
  • Nokia maps. Especially important when traveling
  • Opera Mini
  • The clock and alarm application
  • A counter application that shows my data usage
  • The SMS program
  • The screenshot program

Screenshot0010And sometimes there's also the music player, the podcast client, the calender, the address book and more running in the background in addition to the list above. Not necessarily because they all need to run but because there is no need to quit them as they don't consume resources while they sit in the background and by letting them run I can get to them really fast and pick up from where I left them.

Returning to the last state is a really important feature for me, especially with the maps application and Opera Mini. In Opera Mini it's a joy to instantly return to it after doing something else and to be able to quickly go back several pages without a new reload. And as far as the maps application is concerned it's great to see where I was last and to have a new GPS fix within a couple of seconds.

Sure, to some degree this can be 'simulated' by saving the state of the application before it is quit. However, returning to the application and restoring the state costs time. But why simulate it when you can have the real thing?

Multi-SIM for the Hyperconnected

As more and more people use cellular networks not only to make phone calls but also to access the Internet, the desire to use more than one connected device at the same time is on the rise. The problem: Paying a basic fee for each device and then maybe again for Internet access is often financially not very attractive. But even if you cross that bridge and end up with a couple of gigabytes included for one device and another couple of gigabytes for another device, in the end, you might not even use all the data included in one bucket despite having two devices.

A solution for some cases is a 3G to Wi-Fi Router which works well when devices are close together and you want to share access with a group of people. However, it doesn't work so well when on the move and using several devices at once. But here's an interesting solution:

I found out recently that most German operators offer so called “Multi-SIM” cards. All SIM cards, usually up to three, are registered to the same phone number and can be active simultaneously. Incoming calls are forwarded to all switched-on devices and and the call can be accepted or rejected with any of them.

I've had a look at the fine print of one operator and here, Internet use with a single monthly bucket, even simultaneously on more than one device, is explicitly allowed! Some operators want a one time activation charge for each SIM card, but monthly charges for all SIM cards on a single contract range between very modest and free. Very nice! This will solve a big issue for people with netbooks that have a built in 3G adapter and who want to use a smartphone or other wireless device at the same time. Throw a further slim phone into the equation that can be used with the thrid SIM card and the Multi-SIM approach becomes even better.

But that's Germany, are there similar offers in other countries?

Internet Access on Thalys High Speed Trains – What Happened?

Back in June last year I wrote a post on my very positive experiences with the satellite based Internet access on board the Thayls high speed trains. Multi-megabit speeds, it was a joy to use it. Now, only a little bit more than half a year later the system is not much more than a shadow of its former self. During my past 4 trips, the system was down twice. And the other two times when it was available, speeds could be measured in bits per second and it was impossible to use it. What's going on Thalys? Have you reduced your overall bandwidth to reduce the monthly bill or has the service become so popular you are chocked by the demand? Either way, it's unusable and not worth paying for…

Oh and by the way, I thought long before writing this post but I couldn't let my very positive review stand on it's own, it just doesn't reflect reality anymore.

With VDSL, Wi-Fi Is Now The Bottleneck

Interesting to see how the bottleneck of my Internet connection at home has been shifting recently. With my new 25 MBit/s VDSL connection I am having difficulties shuffling peak data rates over my Wi-Fi network. So far with a 6 MBit/s ADSL connection that was no problem even for my notebook with a 802.11g adapter and a throughput of 21 MBit/s under the best of conditions.

For a 25 MBit/s downlink and 5 MBit/s uplink, however, that's not enough anymore. I've upgraded to 802.11n but even so I find it difficult to really squeeze the 25 MBit/s out of the wireless link. The 2.4 GHz band is quite crowded and the Wi-Fi access point is in another room so I don't get the signal conditions necessary for the highest transmission rates. I've tried the 5 GHz band that both the access point and the notebook support but the attenuation of the walls between my office and the router make the throughput even worse.

On the other hand, you first need to find a host on the Internet that delivers data at such high speed. In practice to really saturate the line several things need to go on in parallel. Not too difficult with kids using the connection, too I suppose…

Some GSM, UMTS and LTE Measurement Units

Even when a mobile device just sits there and seemingly doesn't doesn't do a whole lot it is nevertheless quite busy every now and then internally to check the signal strength and quality of the current cell and those around it to make sure it never looses contact to the network even if the user roams around. I've recently came across a good description of which values are actually measured in this book and thought I'd put together an ultra brief summary:

GSM

Here, the world is still quite simple. Once the mobile has found a cell it keeps monitoring it's received signal power and computes the Received Signal Strength Indicator (RSSI) over the complete carrier frequency (200 kHz). Neighboring cells use different frequencies and the same value is calculated for those as well.

UMTS

Here, things get a bit more complicated as all cells use the same frequency. As a result not only the received signal strength is important but also the general noise level on the carrier. In the end, what good does it do to you when the overall signal level is strong but most of it is interference? That's why there are three values: 

  • RSCP: The Received Signal Code Power: That's the power level the pilot channel of a cell is received with and usually expressed in dBm (mW on a logarithmic scale). With this parameter, different cells using the same carrier can be compared and handover or cell reselection decisions can be taken.
  • RSSI: In UMTS that's the signal power over the complete 5 MHz carrier which includes all components received, including the signals from the current and neighboring cells on the same frequency.
  • EcNo: That's the received energy per chip (Ec) of the pilot channel divided by the total noise power density (No). In other words the EcNo is the RSCP divided by the RSSI. And again in other words: The better this value the better can a signal of a cell be distinguished from the overall noise. The EcNo is usually expressed in dB as it's a relative value. The value is negative as the RSCP is smaller than the total received power. As the RSCP this value can be used to compare different cells on the same carrier and handover or cell reselection decisions can be taken.

LTE

LTE networks also use the same carrier frequency in neighboring cells so again the signal level and interference are important:

  • RSRP: That's the Received Power of the Reference Signal.
  • RSSI: That's the total received power including Interference from neighboring cells and other sources.
  • RSRQ: That's the Reference Signal Received Quality and equals the RSRP divided by the RSSI. The better this value the better can the signal of the cell be received against the interference generated by other cells.

Quite a lot of similarities between UMTS and LTE from a high level point of view even though the values are measured in quite a different way due to the different air interface natures (WCDMA vs. OFDMA).

A Strange Call – Skype and Mobile Handsfree

This is the strangest setup of a conference call I have been in for a while: A Skype video session with high quality audio over speakers and a third person, also on the other end, part of the conversation over a mobile phone as part of the call via loudspeaker/hands-free mode. The person on the other end of the line didn't even realize I was not in the room but a thousand kilometers away. On my end, the speech quality of the hands-free mode on the other end was also pretty much the same as if the phone was on my end. Speaks for Skype's audio codec and the echo cancellation of all devices.

Task Reversal

Observation of the day:

In the past, I 'had to' do many things at home because I could not do them while commuting, because I couldn't take a sufficiently small computer with me and had no Internet connection.

Today, I 'don't do' the same things at home because I can as well do them while commuting with a netbook and a 3G Internet connection.

In other words a total reversal of thinking and behavior. And to the better I think!

3GPP Release Overviews

And here a quick not to myself and to all of those who sometimes need an overview of all the functionalities that have been changed and added in the different 3GPP Releases since Release 99. Here's a link to one document per Release which contains a 'short' one page description of each new work item and the updated TS and TR documents behind it. I know, there are also whitepapers available on the net describing the different 3GPP releases and they are probably much easier to read. However, they usually don't contain references to the specification documents and they don't contain all the features.