Author: Martin

Mobile Network VoIP capacity

One of my favorite topics is cellular network capacity. I posted an example a while back on the 1 kb/s 3G surfer. At the time I excluded VoIP as part of my application mix as it increases network traffic quite a bit. Today I found some interesting material which sheds some light on this part of the story:

Wireless Networks have a particular problem with Voice over IP. While traditional circuit switched traffic was optimized on all layers of the protocol stack to be transferred as efficiently over the air interface as possible, achieving the same effect for Voice over IP is very difficult due to the decoupling of the different network layers on the IP protocol stack. Thus, a VoIP call today consumes at least four times as much bandwidth on the air interface than a circuit switched voice call. In other words, if everybody started to use VoIP over wireless today, network capacity for voice calls would shrink to only a quarter of what it is today.

Now Ericsson has released an interesting slidepack on the topic which targets the non geek investment community but which nevertheless contains some interesting numbers on wireless network enhancements and optimization for VoIP in the future: As described above, Ericsson’s slide pack shows on page three that  UMTS networks today could only provide 20% of the voice capacity with VoIP compared to standard voice calls. So that’s close to my number above. With HSPA (I think they  refer to HSDPA + HSUPA) capacity increases to 70% if IP robust header compression (ROHC) is used. They then go on to claim that with efficient signaling (whatever that is…) and improved scheduler (what improvements?) and optional GRAKE2 (again what is that?) VoIP capacity can be pushed to 140% of today’s standard voice capacity. Finally the next evolution of UMTS called LTE (Long Term Evolution) targets 200% of current voice traffic for VoIP in the same bandwidth.

Not sure what the improvements are they are talking about as they don’t give any further explanations but it seems we are getting somewhere in due time. VoIP VoIP Hurray!

2006 – Year of the Quitter at MoJo

Debi a.k.a. Mobile Jones has discovered that a lot of people seem to quit one thing or the other this year. She wanted to join the pack and has quit smoking. Good idea 🙂 In a recent podcast recording she asked me what I would quit this year (has it become kind of an obsession with her)? Well, I might just quit blog reading…………… on the PC. My blog reader program (Resconews) on the mobile phone is almost good enough to let me do all my blog reading while on the go. Not much is missing in the software. So what will you quit this year?

Quicktime Pro converts video to .3gp format

Mp4_1
Sometimes I download video podcasts I would like to watch and which would also be suitable for watching while on the go on my Nokia N70 mobile. The built in Realplayer, however, does not recognize a lot of different video formats so most of the time, attempts to play such video podcasts on the mobile phone are not very successful. Now I’ve discovered that Apple’s Quicktime player in it’s pro version is able to export video format into the .3gp format which is used by most mobile phones. I gave it a try with a 20 minutes news show which I downloaded as MPEG-4. Reformating to .3gp format took about 3 minutes and the 20MB input file produced a 13MB output file. To my very positive surprise the phone’s built in Realplayer instantly recognized the file and played the 20 minutes video file flawlessly.

Some Thoughts on Mobile GeoTagging

Geoloc
Experimenting with my newly acquired Bluetooth GPS receiver, Python and S60 phone to come up with a tracking and network measurement software, some further thoughts have sprung up about what could be done with the location data. Once the GPS device is embedded in the phone it’s easy to store the exact location as part of the ‘exif’ data of pictures taken with the built in camera. It’s already got a name: GeoTagging.  Here are some ideas what I would like to do with it:

Automatically geotag my pictures I upload to Flickr from the mobile phone via Shozu: Flickr could then be enhanced to detect the geo location in the picture and offer a link directly below a picture to a mapping site such as Google Maps / Google Earth or the Yahoo equivalent. The user clicks on the link and a map of the location where the picture was taken pops up. The photo site could also go through its database to see if other users have taken pictures in the surroundings and show provide a link on the map to those pictures.

Enrich my private picture archive with location information: How about adding some geo functionality in Nokia’s Lifeblog!? The software could detect the geoinformation in a picture and open up my locally installed Google Earth and show me the location. Beyond that the user could create ‘location sets’ of let’s say all pictures taken during a vacation or a trip. Lifeblog could then open Google Earth to show which route I was taken and provide a link back to my pictures at every location a picture was taken.

Enhanced eMail program that detects geotags in pictures: Let’s say I want to show a friend where I am. So I take a picture which has an embedded geotag and use my mobile phone’s eMail client to send the picture. When he receives the picture the eMail program or external picture viewer should detect the geotag and again offer me a link to either my locally installed mapping software (e.g. Google Earth) or a web link to an online service to see where the picture was taken.

The beauty of these solutions is the ease of use for both creator and consumer of the picture. No user interaction is required to geotag the picture as the phone automatically puts the GPS coordinates into the picture. Once programs and websites support geotags there’s also no complicated user interaction required to use the information. Just click on a link or a button and ‘voila’, a map pops up to bring you closer to the image.

So Yahoo, Flicker, Shozu, Nokia and all others, it’s time for some products 🙂

A True World Band GSM and UMTS Data Card

Sierra
In an ideal world, the same radio frequencies would be used for wireless systems worldwide and a device bought on one continent would just work as well on another. Unfortunately, this is not quite the reality.

Countries in Europe, Asia and Africa use the 900 and 1800 MHz band for GSM while UMTS uses the 2100 MHz band. Consequently phones sold in these regions usually support these frequencies. Most phones also support GSM on 1900 MHz which is used in North America but lack the ability for GSM 850 and UMTS 1900 MHz which are also essential for this part of the world. So people visiting North America are always handicapped as in-house and rural coverage is sometimes a problem due to the missing 850 MHz band. UMTS does not work at all…

For people living in North America the situation is vice versa when they travel. Their phones support the 850 MHz band for GSM and the 1900 MHz for GSM and UMTS. These phones usually also support the 1800 MHz band which is one of the frequencies used for GSM in the rest of the world. However 900 MHz GSM and 2100 MHz UMTS is missing…

But hope is on the horizon. Sierra Wireless will launch a Quad Band GSM – Dual Band UMTS data card soon which will support GSM/GPRS/EDGE 850,900,1800 and 1900 as well as UMTS in both the 2100 MHz and 1900 MHz bands. Thus, such worries will be a thing of the past. Let’s hope the technology ends up in mobile phones soon. Nokia for example should have a great interest in this if they want to improve their position in the North America market. Even one of their latest flagship mobile, the N80 does not support both UMTS bands. There’s one for the world market with 2100 MHz UMTS support and another verison with 1900 MHz support for North America. Time to change this!

The question remains why mobile phone manufacturers are so reluctant to produce ‘world band’ phones!? Is the extra hardware cost so much higher than the overhead of producing  and maintaining different hardware and software versions?

A side note: The story is about to be continued. UMTS for the 900 MHz and is already specified and it seems only a matter of time before some countries will start using it. Also, I wonder when UMTS will make it’s appearance in the 850 MHz band.

S60, Python, a GPS receiver, and Google Earth

Googlemaps
Now that most work for the book is done, I have some time to experiment. I recently started to take a closer look at Python for the S60 mobile phone OS and what you can do with it. As I am pretty much into wireless networks, I wanted to have an application that tracks the network coverage where I go for later analysis. I am also quite interested in location based services and a firm believer that these services will only really take off once the GPS receiver is built into the phone. Combining these two interests with a little bit of programming and a recently bought Nokia LD-3W Bluetooth GPS receiver resulted in the following little quality time project:

The Python script I am currently working on queries the GPS receiver, measures the network signal quality and outputs the information in Google Earth format for visualization on the PC. The script is not quite finished yet but the  basic functionality of logging location and signal quality and visualize the data in Google Earth already works. The picture on the left (click to enlarge) shows a result of a 20 minutes test drive. While the line is green, network reception is good. Blue indicates average and red symbolizes a weak signal. Should you be one of the five people on this planet who does similar things and are interested in the source, let me know.

5G New Radio Q&A

All answers have been held as short as possible and require an understanding and study of the corresponding chapter of the book.

Answer 1:

The basic concept of the 5G Non-Standalone architecture is to add a 5G NR cell as a speed booster to an existing LTE radio and core network. It is different from LTE carrier aggregation as the 5G cell acts independently from the LTE part of the connection. Data is transmitted over LTE and 5G NR simultaneously.

Answer 2:

TDD = Time Division Duplex, e.g. used in band n78. Uplink and downlink are transmitted over the same channel. FDD = Frequency Division Duplex, typically used in frequency bands in Europe < 3 GHz. Uplink and Downlink are separated in the frequency domain, i.e. they use different channels. Hence, uplink and downlink are transmitted simultaneously.

Answer 3:

In 5G NSA, data is transmitted over LTE and 5G NR at the same time. Typically the 5G gNB receives the data, splits a apart of it away and forwards it to the LTE part of the connection while it transfers another part itself.

Answer 4:

In the uplink direction LTE and 5G use different frequencies and one transmitter in the UE is required for each channel as data is transferred simultaneously over both legs of the connection in the uplink direction.

Answer 5:

In 5G NR, a UE does not necessarily need to support the full channel bandwidth and can be assigned only a part of the channel on the frequency axis. Also, a network might decide to assign different bandwidth parts to a UE to conserve power with a narrow BWP while only small amounts of data are transferred.

Answer 6:

The CORESET is the Control Region Set, i.e. the control regions the UE has to monitor on the channel for uplink and downlink assignments.

Answer 7:

Dynamic Spectrum Sharing (DSS) can be used to transmit LTE and 5G NR on the same channel. This way, the channel can serve older LTE only mobiles and newer 5G NR mobiles. This is done by transmitting the control channels of LTE and 5G NR in the channel at different times and by using several methods and signaling alignments for 5G NR devices to only notice the 5G transmissions while LTE devices only see the LTE signaling channels and reference signals.

Answer 8:

The LTE eNB and 5G NR gNB have independent schedulers and communicate over the X2 interface which each other. This way, handovers can be made independently as only the X2 connection is switched. In practice it often occurs that the LTE and 5G NR parts are served by different sites. The uplink/downlink data is split/combined at one of the two sites.

Answer 9:

The idea behind the Service Oriented Architecture is to leverage container technology in combination with microservices and stateless communication to build a highly adaptable, configurable and scalable 5G core network.

Answer 10:

5G registration management is performed by the Access Management Function and deals with authentication of subscribers and managing their presence in the network. Session management on the other hand is managed by the Session Management Function and deals with the establishment with user plane bearers between the mobile device and an external network such as the Internet.

Answer 11:

In RRC-Idle state, no active connection exists between the mobile device and the gNB over the air interface. Also, the signaling connection and the user data tunnel to the core network have been removed. In RRC-Inactive state, only the air interface connection is removed while the connection between the gNB and the core network remains in place. This significantly reduces signaling when connectivity needs to be restored.

Answer 12:

The idea of Network Slicing is to have a single end to end network and serve devices with different requirements in different ways. On the air interface, different parts of the channel can use different configurations. One part of the channel could be used for fast Internet access, while another part, that is configured differently could be used for slow but very reliable communication. Other parts of the network can be sliced in a similar manner.

Mobile Monday Paris May 2006 – Pictures and Thoughts

Momoparis
Another Mobile Monday Paris took place last night at the Zen Factory in Paris close to the Place de la République. Again a fabulous event, lots of good discussions with people coming to the event and very interesting presentations. For pictures of the event, see my Flickr picture set of the evening.

First speaker of the evening was Stephane Delbecque of Yahoo France presenting Yahoo’s Connected Life vision. Focus of the presentation was Yahoo’s partnering with the Fifa to bring the football world championship to mobile phones all around the world.

Next, Didier Lesteven of Medialive presented their product which protects digital content on the way from the content provider to the consumer. This is done by their product by stripping out 1% of a media flow which is then protected and sent to the consumer in a secure way.

Afterward Philippe Coup-Jambet of Mobitype gave an overview of their moblogging platform that lets you create your own blog from your mobile phone and also acts as a mobile RSS aggregator. The product is currently in a first trial phase with the public launch expected this summer. The service will be free and is funded by ads which are put into the generated pages. I specifically liked the options of having the top 24h hour posts in one menu as that is missing in my current mobile RSS software.

Presentation number four was by Vincent Berge of the PACA Mobile Center, a new parisian institution in Marseilles that offers a platform for Java developers to test their products on a multitude of different phones.

And finally, Catherine Ramus made sure the evening was not only about technology in itself but also about combining technology with art and her presentation was about how to use 2D bar codes in a museum to get video stream art right on your mobile phone.

Great presentations, thanks very much to the presenters, I really enjoyed the evening! The presentations might end up on the official Mobile Monday France website in a couple of days and you can check them out here.

The Mobile Internet’s 5th birthday

T39j Only 5 years ago, the Internet started to get mobile for me with the launch of the first GPRS networks in Germany and the advent of the first GPRS capable phones. What a different world it was compared to today.

I must have been one of the first GPRS users of the network because at this time and phones and networks were in a shaky beta phase at best. The Ericsson T-39 (first picture on the left) was my first GPRS phone. Equipped with a tiny monochrome display, it could bundle two timeslots to give me a blazing download speed of 25 kbit/s. For web browsing I used a Palm III, also with a monochrome display and one of the first embedded web browsers available at the time. Again, pretty much a beta experience but I loved it.

Yesterday, 5 years later, I was sitting in one of Paris’ best cafés, enjoying good company, an ice cream and discussing mobile lifestyle: Instead of bringing a magazine with me to browse through, my Nokia N70 is always with me ready to take pictures, videos and to connect me to people and the Internet. Here I was, reading the latest news using the Opera browser on the phone, when my eMail client informs me of a new eMail of my publisher in which he informs me that the shipping date for my next book will be July 14th. Great! A little while later, I uploaded some pictures in the background to Flickr which I took in the afternoon while reading some interesting blog entries in the mobile RSS reader at the same time. On the network side, UMTS is much more stable than GPRS was only 5 years ago and data rates have improved from the 25 kbit/s of 5 years ago to 384 kbit/s today.

So what are we in for in 5 years from now? Network speeds will certainly be beyond 8 MBit/s in downlink and 2-3 MBit/s in uplink direction. Prices for mobile data will (hopefully) be at a level to attract the general audience and in combination with the increased bandwidth and services such as video up- and download, LDA applications using the Internet connection and built in GPS receivers will make the application landscape even richer.