Category: Uncategorized

These days I see a lot of talk in the press about rising wireless data consumption. To make things more spectacular, things don't double, no they rise by 100% (or by 200% or by 400% [insert your own % here]). Sounds much more dramatic, no? But what's even worse is that without a base from which the rise is calculated, it's completely meaningless. And usually that base is not given.

Here's an example: Let's say network use was 1%. Doubling that brings the network use to 2%. That's a lot isn't it? 100% more but the network is still sitting around doing pretty much nothing. But 100% more…(Note: Agreed, I've selected the other extreme for my example here…)

Also, such numbers kind of suggest that things will continue to grow at the same rate or even faster and the numbers are set in a light that suggests operators are in real trouble in the very near future. But that's also a wrong assumption. At some point everybody has 5 phones, several 3G dongles, etc. and bandwidth needs will mainly grow with more use from the same number of people and devices. And how much growth that requires is a different story again.

But one thing is clear, mobile operators need to increase the capacity of their networks over time to keep up with the demand. But then that's not much different from what fixed line operators do to keep up with the demand for high speed Internet connections. Maybe they have to do even more with digging up roads, putting new fibers in, etc. From a different point of view they are even doing the ground work for wireless network capacity extensions as they will also benefit from the fibers in the ground.

Changes over time tend to blend in into everyday work unless you really think about them. Just recently, I came across a list of network vendors I wrote down in 2005 to give readers examples of big wireless network infrastructure vendors. The list read:

• Siemens, Nortel, Ericsson, Alcatel and Nokia

Obviously the list is not exhaustive and not in a particular order. Powerhouses in 2005, no?

Now it's 2010 and four out of those five no longer exist in that form or shape. Today the list would read:

• Ericsson, Nokia Siemens Networks, Huawei, Alcatel-Lucent

Predictions for 2015, anyone?

I can still remember the days when 3GPP Release 99 was the latest and greatest with the introduction of UMTS and data rates of 384 kbit/s. It's not that long ago really, and it's incredible how much has changed since then. As I went through the feature descriptions I drew up a list of which features I personally think are the most important ones in each release:

Release 4

• Even today, Release 4 is still synonymous with the definition of the Bearer Independent Core Network (BICN) or, in other words, the virtualization of the circuit switched network.

Release 5

• Introduction of the IMS which has continued to be developed throughout all following releases
• The specification of High Speed Downlink Packet Access (HSDPA). I think this is one of the single most important features ever specified. Without it, UMTS would look entirely different today.

Release 6

• Introduction of High Speed Packet Uplink (HSUPA)

Release 7

• Specification of HSPA+ with 64QAM and MIMO
• Enhancements to conserve battery power and to make state changes quicker for a better browsing experience. Also referred to as Continued Packet Connectivity
• HSUPA 16QAM for a faster uplink
• Extended Cell Range. Wasn't that done for Australia?

Release 8

• The LTE baseline release
• Definition of Dual Carrier HSDPA
• Simultaneous use of 64QAM and MIMO on a single carrier
• Single Radio Voice Call Continuity to hand-over voice calls from a packet to a circuit switched bearer
• Femtocell definition (Home NodeBs)
• Small but Important: ICE (In Case of Emergency) information storage on the SIM card and retrieval in a standardized way to help first responders to contact your family and friends in case something has happened to you.

Release 9

• Separate dual carriers to simultaneously transmit downlink data in the 900 and 2100 MHz band.
• Dual carrier in the uplink
• Inclusion of the European Digital Dividend band

Release 10

• Information on the content of Release 10 is still sketchy at this time. The one thing that is clear at this point that it will contain the baseline for LTE Advanced.

Agreed, a very very short list considering the dozens and dozens of features in each release. So, what have I been missing that will really make an impact? Do you have other favorites?

While waiting out in the open for the tram on my daily commute I like browsing the web and reading my favourite blogs on the mobile phone. Not so these days, however, it's just not a lot of fun in sub-zero temperatures. So I prefer wearing gloves and keeping my hands in my pockets. In noticed, though, that the battery gets a bit warm while surfing if I can't resist which at least helps a bit. So what about a little built in heating at the back of the mobile? Yes, the battery would drain faster but it would be usable in sub-zero temperatures. Yes, I am only half joking here, but I am not quite convinced it's just a stupid idea. I wonder why Nokia, coming from a Nordic country never had the idea. Well, maybe with the temperatures there even heatable mobiles wouldn't help in winter 🙂

Here's a link to an interesting video produced by 3GPP during the September 2009 plenary meeting in Seville, Spain. In the video the plenary chairmen of Service Architecture (SA), GERAN (GSM/GPRS/EDGE radio access), RAN (UMTS and LTE radio access) and CT (Core Network and Terminals) give their opinion on the state of the industry, where 3GPP is heading and the main features currently discussed for Release 9. And from a procedural point of view you get short insights in how 3GPP meetings a run and how many people attend.

Putting cell towers in place is one thing, optimizing their coverage quite another. Today, a lot of planning is required in advance to make sure all required neighboring cell information and handover parameters are available, antennas are installed and configured with the correct angle in order not to create too much interference in the coverage area of neighboring cells, etc. etc. With adding yet another radio layer with LTE, things are not getting any easier if everything has to be done by hand and later-on check and refined with drive tests. Furthermore, networks are never static as new cells added, as frequency plans change, etc., so frequent quality checks like drive tests are required.

To reduce the amount of work required, 3GPP is working on a standard for LTE to be a bit more self-organizing, self-correcting and reporting issues that can't be fixed automatically to maintenance. A number of papers have been written to cover the current state in 3GPP on this topic, for example by Nomor back in 2008 (see here) and by 3G Americas recently (see here). In the 3GPP archives, the following technical report might be of interest to you on which the subsequent standardization is based on:

3GPP TR 36.902: Self-configuring and self-optimizing network (SON) use cases and solutions

With 3GPP Release 9, time has come to put things into Technical Specification (TS) documents. These can be found in the 3GPP 32-series starting with TS 32.500. Here's a list (no exhaustive) of documents that sound especially interesting:

• 3GPP TS 32.500: "Telecommunication management; Self-Organizing Networks (SON); Concepts and requirements"

• 3GPP TS 32.501 and 36.502: "Self-Configuration of Network Elements; Concepts and Integration Reference Point (IRP) Requirements" and "Information Service (IS)"

• 3GPP TS 32.503: A CORBA framework for SON

• 3GPP TS 32.511: Automatic Neighbour Relation (ANR) management

• 3GPP TS 32.521, 32.522, 32.523: SON stage 1, stage 2 and stage 3

• 3GPP TS 32.541, 32.542, 32.543: Self Healing stage 1, stage 2 and stage 3

Quite an impressive list and the whitepapers mentioned above list the following features that are thought of in 3GPP:

• Self-configuration: Retrieve basic operation parameters from a centralized configuration server when the cell is first activated.

• Automatic Neighbor Relation (ANR): Mobile devices can report cells to the base station they are currently served by that are not in the neighbor list. This information can then be used by the network to automatically establish neighbor relationships for handovers.

• Coverage and Capacity Optimization: Interference between cells due to too much overlap ov the coverage area and the opposite, coverage holes, are one of the main enemies of every network planner. Such conditions are usually detected with drive tests. Here SON aims to use mobile device and base station measurements to detect these issues. While interference can potentially be reduced automatically, unintended coverage holes can sometimes only be fixed with additional base stations. In such a case the equipment could at least notify the network operator.

• Energy Saving: Reduce transmission power in case it is not needed, automatic shutdown and re-initialization of femtocells when the user arrives in or leaves the coverage area of the femto.

• Physical Cell ID configuration: This is a very short id that mobile devices can read without decoding the full broadcast channel. Only 504 IDs are available so they are not unique. Therefore, an auto-configuration is highly desirable. Again, the mobile is required to report to the network which cells it sees for the configuration process.

• Handover optimization: By analyzing the failure causes of handovers, coverage holes or wrong handover decisions can be detected and changed.

• Load Balancing: If a cell already experiences high load from many users, send users at the cell edge to nearby cells.

• Random Access Channel Optimization: The random access channel (RACH) is needed for the initial communication between non synchronized mobile devices and the network. Depending on the load, the number of resources dedicated to the RACH can be changed dynamically.

Quite a list! Interesting though that for the moment, all actions pretty much focus on LTE only. Lots of potential therefore for the future to extend SON functionality to the interworking with GSM and UMTS networks. In that regard I wonder if in the future network vendors will manage to offer an integrated SON an general management functionality for GSM, UMTS and LTE.

Ideally in a world where base stations are (auto-) software configurable on the fly for whatever air interface technologies are required at a certain place at a certain time. Advanced multi-mode base stations, but that's another topic…

Just a little note today on the availability of ITU standards. While I don't need them often, every now and then they are a great help to find the answer to some really nitty gritty circuit switched telecommunication network questions, both fixed and mobile. Most of them are available from the ITU web page. Not quite as open as 3GPP standards, i.e. the latest updates and additions seem to require some form of registration and/or payment, but for most purposes it should do.

A couple of days ago I wrote about the slow startup time of UMTS during mobile web browsing when the air interface connection is in disconnected state. Looks like my idea of establishing radio bearers early for example when unlocking the phone is not necessary as a couple of enhancements are already foreseen to address this issue:

The first feature is the Cell- and URA-PCH Radio Resource Control (RRC) states. Already defined in the very early stages of the UMTS development they are still not used by most operators today. The major difference to going to RRC disconnected during a prolonged time of inactivity is that all logical radio bearers remain allocated and also the logical signaling link from the Radio Network Controller to the SGSN in the core network remains in place.  So instead of going through the procedures for RRC establishment, authentication, ciphering, radio bearer setup and radio bearer reconfiguration for high speed, the mobile device simply goes back to Cell-FACH state by sending a data packet. And from there, a radio bearer reconfiguration takes the link back to the high speed channels.

So instead of over two seconds, the procedure takes from the disconnected state today, the time necessary to get out of Cell- or URA-PCH state to the high speed channel should be similar to the time it takes from Cell-FACH to high speed today, which is less than a second. That's very close to the times already achieved with the good old GPRS/EDGE air interface. There might be an impact on power consumption with the Cell- and URA-PCH states. However, like in idle state, only the paging channel needs to be observed so this is likely to be a small trade-off.

The second feature is the Enhanced Cell-FACH state that is part of the Continuous Packet Connectivity feature which I've reported on here, here and here. That should reduce the time even further as the radio connection doesn't have to make a detour over a dedicated channel.

All very nice, now it just has to come!

A quick note to myself today that might be helpful for you as well on LTE System Information Messages. SI's have existed since the days of GSM (and probably before) and inform mobile devices about all important parameters of how to access the network and how to find neighboring cells. Here's an overview of those that have been defined for LTE so far. For details see 3GPP TS 36.331 Chapter 6.3. Compared to GSM and UMTS, the amount of parameters inside seems quite a bit less bloated:

• Master Information Block: Most essential parameters

• SIB 1: Cell access related parameters and scheduling

• SIB 2: Common and shared channel configuration

• SIB 3: Parameters required for intra-frequency cell reselections

• SIB 4: Information on intra-frequency neighboring cells

• SIB 5: Information inter-frequency neighboring cells

• SIB 6: Information for reselection to UMTS (UTRAN) cells if no suitable LTE cell is available

• SIB 7:  Information for reselection to GSM (GERAN) cells if no suitable LTE or UMTS cell is available

• SIB 8: Information for reselection to CDMA2000 systems (mostly for North America)

• SIB 9: Home eNodeB name – for future LTE femtocell applications

• SIB 10 + 11: ETWS (Earthquake and Tsunami Warning System) information

• SIB 12: Commercial Mobile Alerting System (CMAS) information. Never heard about this before!?

After noticing that the Nokia E75 announces SIP AMR-WB capabilities I did some follow up work to see where it is standardized and how universal it is. According to Wikipedia, AMR-WB is specified in ITU G.722.2. Several bit rates are available and what I can see in 3GPP, codec rates up to 12.65 kbit/s are used in wireless. Makes sense as that is a similar maximum bit rate as for EFR (Enhanced Full Rate) or AMR-FR (Adaptive Multi Rate – Full Rate) in GSM and UMTS today, i.e. the same air interface bandwidth is required as for todays codecs.

To be able to use AMR-WB in wireless networks, transcoders need to be deactivated in the network. The features for this are Tandem Free Operation (TFO) and Transcoding Free Operation (TrFO) in GSM and UMTS respectively. For details on those see a blog entry I wrote back in 2006 (!). Interestingly enough, this blog entry is still very popular so it looks like quite a number of people are working on this.

So what about fixed line networks? Here, my picture gets a bit sketchier but I'll try to put the pieces together here. If you have different/additional info, please let me know. The successor to the current cordless digital standard (DECT) is called Cat-iq. Again according to Wikipedia, the wideband voice standard used here G.722 at 64 kbit/s. G.722 is the big brother of G.722.2 and they don't seem to be compatible. Also, it seems that the wideband codec can only be used over an IP link, i.e. the phone must be connected to a SIP VoIP provider. On this thread, Frank-Christian Kroegel mentions that ISDN can also be used for the wideband codec but it seems that is not done in practice yet. And anyway, except for Germany and a few other countries, ISDN is not widely deployed anyway. 

So it looks like wideband voice is going different ways in fixed and mobile networks for the moment. That's a pity but who knows, with fixed and wireless networks operators merging again these days, things might change in the future. I wonder how long it will take to have a wideband voice future besides with Skype?