Hard Handoff

14 years ago last week I started a new job at Telecom Mobile as a Cellular Engineer back in the days when that meant running around the country installing new cellsites. These days with that kind of title I'd be splicing genes...


One of the things I learned in the first week (other than sneezing next to one of my new colleagues got me banished to the other end of the floor) was the concept of handoff.

Handoff is part of the magic that makes mobile telephony work. It is the mechanism that allows a mobile to move from cell to cell while maintaining the call. Its what makes it 'mobile'. The only hitch was that 'maintaining the call' was a bit of a euphemism. The way it worked was that the system would detect that call quality was declining (or in the digital systems the mobile would detect that an adjacent cell had better quality characteristics), work out where the the best cell for the call might be, prepare a spare channel on the new cell and tell the mobile to tune to that channel.The mobile tunes to the new channel (leaving the call on the old one behind) and all things going well(there is NO such thing as perfect engineering) the call would be resumed on the new cell on the new channel.There was a noticeable break in the conversation while this process occurred - I used to think of it as a hopeful period where you'd hope that the system and the mobile had all got their act together.

I learned that belief was quite important in this process and spent a lot of time driving around testing the network, listening for breaks in calls and hoping that the calls would stay up. I guess that would be why I wasn't the best engineer - too much hope and belief!

That type of handoff is a hard handoff - breaks the connection before it makes the new one. The CDMA systems these days have a much more reliable and secure way of making handoffs work - the mobile stays in contact with a number of cells so never breaks the conversation until it gets to the edge of the system. That's a soft handoff - much better for customers but not so much fun for engineers. No so much hope and belief required.

I've initiated my own hard handoff this week and resigned from Telecom. The reason its a hard handoff is that I haven't got a new role to move to. I know what I want to do - which is to lead a company that makes a real difference for customers - and once I decided that, it would have been mercenary to look for that while I was here. Hence the resignation.

Mobile phones don't have their own emotions - but if they did they'd feel a mixture of uncertainty every time they went through a handoff. But over-riding all of that they'd be hopeful and optimistic. They'd believe that they could do it. And they'd just let go of what had been good for them and trust that they'd find something better.