Author: Martin

While well dimensioned 3G networks are offering fast Internet access today, some somewhat underdimensioned networks show the first signs of overload. Some industry observers argue that the answer is to introduce tiered subscriptions, i.e. the user gets a guaranteed bandwidth or a higher bandwidth if he pays more. But I am not sure that this will work well in practice for two reasons: The first reason is that when some users are preferred over others in already overloaded cells, the experience for the majority gets even worse. And second, if such higher priced subscrptions get more popular because the standard service is no good, it won’t be possible at some point to statisfy even these subscribers. So such gold subscriptions just push out the problem a bit in time but otherwise don’t help a lot. There is just no way around sufficient capacity or your subscibers will migrate to network operators who have made their homework. So instead of only investing in QoS subscription management I would rather also invest in analysis software that reports which cells are often overloaded. That gives the operator the ability to react quickly and increase the bandwidth in the areas covered by such cells. Having said all of this, what do you think?

Here I am, back in Italy and again using my 3 UK SIM for Internet access, since there are no data roaming charges between 3 networks in different countries. Very interesting and also a bit depressing to see the performance throughout the day. Sunday morninig 8 am seems to be a pretty quiet time and I easily got 1.5 MBit/s in downlink. Evenings seem to be high time, with data rates dropping to less than 300 kbit/s and long page loading times due to lots of lost packets. I am pretty sure it’s not a cell overload since the Wind UMTS network at the same locations easily gives me 1 MBit/s and no packet loss in direct comparison. So the bottleneck is either the link back to the home network or the GGSN in the UK .

While it’s good to see the networks being used and affordable data roaming in place, I’d appreciate sufficient capacity in the core network.

Since I travel a lot, I often stay in hotels. One thing in hotel rooms I could live without is the TV set, as I never have the desire nor the time to watch anything anyway. In recent years, however, I've noticed that good old cathode ray tube TV's are giving way to TFT TV's. Last week I took a closer look and noticed that these TV's usually also have a VGA or DVI input. Excellent, now I can finally put them into good use and connect them to my notebook as a second screen. All that is needed is a VGA or DVI cable, which I will take with me from now on. The picture on the left shows how my typical hotel setup looks like. Screen 1, screen 2 and a 3.5G HSPA modem for Internet connectivity. Almost as good as at home 🙂

In a comment to a recent blog entry somebody left a link to an interesting S60 utility that records power consumption and other interesting technical information while Noka NSeries and other S60 based devices execute programs. Running in the background, one can perform actions and see the impact on power consumption. The picture on the left for example shows power consumption during different states during mobile web browsing.

The left side of the graph (click to enlarge) shows power consumption while a web page is loaded, i.e. while the device is in Cell-DCH / HSPA state. Power consumption is at almost 2 watts during this time. Once no more data is transferred, the mobile is set into Cell-FACH state by the network which requires much less power. However, the 0.8 watts is still significant. After about 30 seconds of inactivity the network releases the physical bearer and only maintains a logical connection. In this state, power requirements drop to about 0.2 watts which is mostly used for driving the display and the background light. When the device is locked and the background light is switched off, the graph almost drops to the bottom, i.e. to less than 0.1 watts.

An excellent tool to gain a better understanding of power requirements of different actions and processes!

I am on the road quite often and, as most of you have figured out in the meantime, a heavy user of 3G networks for Internet access. While I generally like the experience some network outages like this two and a half day nationwide full Internet access blackout in the Vodafone Germany network recently sends shivers down my spine. After all, we are not talking about a third class operator but one that claims to be a technology leader in the sector. As I use Vodafone Internet access a lot I was glad I was only impacted for half a day, having been in a DSL save haven for the rest of the time. If I had been on the road, however, this would have been a major disaster for me.

I wonder if the company that delivered the equipment that paralyzed the Vodafone network for two and a half days has to pay for the caused damage!? If it’s a small company then such a prolonged outage with millions of euros in lost revenue can easily put them out of business. And that doesn’t even consider the image loss for all parties involved and the financial loss of companies relying on Vodafone to provide Internet access. The name of the culprit was not released to the press but those working in the industry know very well what happened. Hard times for certain marketing people on the horizon…

Vodafone is certainly not alone facing such issues as I can observe occasional connection issues with other network operators as well. These, however, are usually short in nature and range from a couple of minutes to an hour or so. Bad enough.

To me, this shows several things:

• There is not a lot of redundancy built into the network.
• Disaster recovery and upgrade procedures are not very well thought trough as otherwise such prolonged outages would not happen.
• Short outages might be caused by software bugs and resetting devices.
• I think we might have reached a point where capacity of core network nodes have reached a level that the failure of one device triggers nationwide outages.

So maybe operators should start thinking in earnest about reversing the trend a bit and consider decentralization again to reduce the effect of fatal equipment failures. And maybe price should not be the only criteria to be considered in the future. Higher reliability and credible disaster recovery mechanisms which do not only work on paper might be worth something as well. An opportunity for network vendors to distinguish themselves?

Recently I spoke to a sales engineer of Kathrein, a prominent German antenna maker that develops and produces all sorts of antenna equipment from TV antennas to sophisticated cellular network antennas. I can still remember how simple antennas were 10 years ago when GSM was first deployed: In many places simple dipol antennas were used and sometimes funny looking trident antennas (that’s how I call them anyway, I am sure they have a more scientific name…). In the meantime we have mostly moved to bipolar antennas that offer a main and diversity output to the base station. On top of that, lots of other things have been developed which are either now being deployed or waiting for that 4G bandwidth push that requires sophisticated antenna features:

Dual band antennas, e.g. 900 + 2100 MHz in one standard casing for sites with GSM and UMTS base stations: Such antennas give themselves away with four connectors at the bottom.

Wideband antennas, e.g. 2.1 – 2.5 GHz to support UMTS and LTE with a single antenna: I am sure those will be in high demand once LTE is deployed in the 2.5 GHz range.

Cable reduction: To reduce the number of expensive coax copper cables between the base station and the antennas, combiners have been developed to combine the signals of several base stations, send them through a single cable and then separate them again before they go into the different antennas.

Remote Electrical Tilt (RET): The size of a cell mostly depends on the angle of the antenna at the rooftop. The more it is tilted towards the ground, the smaller the coverage area. When a new base station is installed to increase the availble capacity in an area, it is necessary to change the tilt of neighboring antennas to reduce interference. Also as capacity in the network increases, it is also sometimes necessary to change the tilt of antennas to improve the overall coverage and bandwidth distribution. Manually changing the tilt of an antenna for these scenarios is expensive and sometimes simply not possible. This is where RET comes in. Instead of physically changing the angle of the antenna, RET changes it by increasing the lengths of the different antenna elements inside the antenna casing. This way, the overall antenna can be electrically tilted by around 10 degrees. Practically, changing the antenna lengths is done with an electrical motor that drives a spindle inside the antenna casing which can change the antenna lenghts of the different modules. The electrical motor is an add on module at the bottom of the antenna.

Antenna auto adjust: It can also be imagined that RET is used in the future to automatically ajust antenna angles based for example on the time of day. This could help to increase coverage in certain areas at certain times of the day by decreasing the cell size. Things could be pushed even further by linking the RET mechanism to the load of the cell and increase the tilt when the cell gets busy to offload some of the borader traffic to neighboring cells.

MIMO and Beamforming: And then there is Multiple Input, Multiple Output and beamforming for further bandwidth increases that requires several antennas at the rooftop. In practice, they are again included in a single casing to look like a single antenna to the outside. The first 2×2 MIMO systems will use little crossed antenna elements that send each MIMO channels with a vertial and a horizontal polarization.

All highly interesting and shows how important antennas have become for increasing bandwidth in the future. Thanks to Kathrein for the interesting information!