Time to first call (A warm start metric for femtocells)

Standby Switch One of the interesting statistics from recent femtocell trials has been that over 20% of customers turn them off overnight. How does this affect the design of the femtocell switch-on process, and will this be a metric by which femtocells are judged?

 

An analogy with printers


Many computer users now have personal printers, either inkjet or laser, which are used less frequently those in busy offices. There was a period during the introduction of these devices where the time they took to startup was significant.

Laser printers were particularly tedious, because the internal mechanism needs to be extremely hot to work properly. There were also various startup checks to be made, both mechanical and electronic.

Time to first print became a very competitive metric where other aspects might be very similar. As a result, significant engineering effort went in to designing and optimising the aspects which took the most time.

Many laser printers are now well under 20 seconds from cold start to starting to print, which makes them comparable with inkjet.

We are also used to almost instant use on demand from many other items of equipment – our cars, lawnmowers, dishwashers, GPS receivers, TVs etc.

(If anything, I’d grumble that my PC takes a long time to startup and become useful, although that can be partially worked around by hibernating it. I understand Windows 7 should improve things.)

What happened with mobile phones

Those with a long memory might recall the early days of GSM phones, when they also took a fair amount of time to startup, perform a full scan of available basestations and networks, register and go online.

After a while, handsets got better. This was partly due to various optimisations in the standards themselves, but also because of some sensible internal improvements.

It’s extremely common for handsets to be switched off and on in exactly the same location, so the first thing to do is to look for the same cellsite at the same frequency that was last in use and simply re-register rather than performing a complete re-scan.

It’s effectively a “warm-start”.

Femtocell Warm Starts

A femtocell may take 10-15 minutes to conduct a full environment assessment and work out the best frequency/mode to use in operation from a cold start.

Some (but not all) will then continuously monitor and adapt to the changing radio environment, for example if you open the window or an external site goes offline.

After being switched on in the morning, a femtocell could perform a “warm start” and check whether its immediate environment has changed. If not, it could then go online fairly quickly and be ready to make/receive calls.

I guess a timeframe similar to starting up my PC would be a reasonable goal.

Auto-Power Save?

A UK satellite TV company remotely updated all it's 9 million set-top boxes so that they automatically hibernate into standby mode, unless they are actively being used - both during the day or night time. This is estimated to save customers around £20 million (approx $30M) in energy costs.

I think femtocells are less appropriate to switch to standby during the day - some may argue its not sensible overnight because you can't be contacted in an emergency if your mobile phone is the only number you use. Indeed, it may be better to link the domestic femtocell with being active to the times you are in the home (i.e. evening/overnight) and switch itself off during the day. Business/enterprise femtocells could then be switched off overnight when the office is empty.

Maybe someone will figure out a way to automatically switch the femtocell on/off when you enter/exit the house (bearing in mind that more than one person may share the residence or office).

Feature Priorities

I’m sure there are plenty of potential features on the roadmap for femtocell vendors. Whilst this may not be top of the list, I hope it’s in there somewhere. Partly to give the customer a good experience, but also to be environmentally friendly in encouraging them to turn off when not in use for reasonable periods.

Do you have a suggested feature for our femtocell vendor’s roadmap. Make a suggestion below (you can comment anonymously if you prefer).


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