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Fast, Good, Cheap, Pick Any Two

Posted on Thursday 19 June 2008

Tech legend has it that a self-confident engineer, when facing an ambitious product manager in a design meeting and realizing that said product manager had specced a product that did everything, cost next to nothing, and needed to be in the market in weeks, said something along the lines of, “I can build your product quickly, I can build it cheaply, I can build you a good product. Pick any two qualities you want, because nobody can build you a product with all three.”

I recall that the first time I heard it was at MCI Mail, which would put the timing sometime in the mid-80s. It was in exactly the context I described above. An engineer was asking a product manager to get a little bit more realistic about a particular product design.

I later came up with the corollary for wireless networks. Not quite as elegant as ‘Fast Good Cheap’ but every bit as valid. A given wireless system, regardless of protocol, frequency or power, had three variables: Base station radius, airlink data rate and the battery life of the terminal. The tradeoffs forced interesting choices in network and terminal (think handset) design. If you want a network that offers users a lot of bandwidth either you’re going to have to put in a lot of base stations or the users are going to be charging their handsets a lot. If you want to deploy a network with broad coverage and decent battery life in the handsets the bandwidth available to users will be low. These sorts of decisions are still made today.

Software and hardware designers have been working on ways to mitigate these restraints for years. Engineers have put in power saving circuits that essentially ‘woke up’ the terminals for 1/15 of a second, every second, to see if the network had an incoming message or call for the terminal. Users never knew that their terminals were asleep most of the time, but they were ecstatic at the battery life. Didn’t you ever wonder why a simple pager could last a month on a single penlight battery?

Where else have you seen similar ‘Fast Good Cheap’ choices?

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