Well, we've left the Analog and TDMA/GSM cocktail parties with a better understanding of how the technologies work.  There's still one more party to attend and it has been going on for quite some time now even though the host – CDMA – is the new kid on the block.  Before we get into the description of how CDMA actually works, however, it would be useful to provide a little historical background.

Back in the go-go days of cellular, when analog was all the rage and the StarTAC was the phone of the moment, it became clear that measures needed to be taken to increase the capacity of systems in order to accommodate the calling patterns that vastly exceeded the projected levels. 

Cellular companies were so strapped for capacity that they actually went back to the Federal Communications Commission and filed a formal request for additional spectrum called the "Analysis of Spectrum Requirements" (I ought to know… I wrote it while at Compucon, one of the premiere cellular consulting firms at that time), which was ultimately granted.  But adding more spectrum and more cell sites is costly – it's a lot less expensive to pack more conversations into the same radio space (a channel) than it is to continue to add equipment. 

The industry went back to the well again asking for more capacity and this time the FCC refused.  They said, in essence, "figure out a solution that doesn't require additional spectrum."  At that point the industry's tech folks collected their thoughts and decided to conform to a standard that used TDMA to get the job done.  Everyone was just about ready to sign off on that standard when a company that nobody had ever heard of before stuck their noses into the technical committees and said they had a better idea.

The company was Qualcomm and the technology was CDMA (Code Division Multiple Access).  The rest, as they say, is history.  Qualcomm rose to become one of the true powerhouses in the wireless industry and CDMA was selected – and not without a lot of criticism – by Verizon and Sprint for the bedrock of their networks. 

CDMA, as I pointed out in an earlier post, actually was developed in a most unusual manner – it was conceived and patented by a Hollywood movie starlet, Hedy Lamarr, during the second World War in an effort to protect the transmission of sensitive communications – and the fundamental method in its DNA, called "frequency hopping" allowed the transmissions between our military personnel to be secure.  A wonderful byproduct of this frequency hopping was the increased capacity of a radio channel. 

Now that you understand why CDMA was developed (to increase capacity of existing cellular systems) we can move on to how it works, so let's finish making the rounds of the cocktail parties (whew, it's been a long night!) and see how CDMA works. 

You'll recall that at the other cocktail parties there were rooms with a sign over them saying "Conversations held here" – this one is no different.  This time we get into the room and, unlike either the Analog party or the TDMA party, there are about 10 couples in the room and they are all talking at the same time.  But nobody's conversation infringes on the other because one couple is speaking French, another Italian, another English, another Mandarin, another Spanish and so on.  (That's why I refer to CDMA as the United Nations of wireless standards.)  So even though they can all actually hear each other they tune out the extraneous noise and tune into the other person with whom they are conversing. 

There is, of course, a limit to the number of couples that you can put into that room because as everyone continues to talk there is an ambient level of noise that continues rising that will, theoretically, drown out all of the conversations.  The trick is to keep the ambient noise balanced with the number of conversations and find a happy medium.  But so far, CDMA technology seems to be working well and has expanded the capacity on radio channels far, far beyond what they were originally capable of carrying.

Oh yes, the frogs.  Well, in the jungles of the rain forests in Puerto Rico – and now having been accidentally imported into Hawaii – lives a tiny frog no larger than the quarter-dollar coin in your pocket.  The coqui is tiny, indeed, but its communications capabilities are extraordinary.  Late at night, when all is otherwise quiet, these tiny creatures speak to each other across ponds using a natural version of TDMA and CDMA.  They wait until there is a very brief moment of time – a time slot, if you will – before they emit their own individual distinctive croak and, simultaneously, tune into the reciprocal croak at the other end, filtering out all other noises.  They're living in both cocktail parties at the same time. 

So, much to most people's surprise you can track the roots of these technologies – TDMA and CDMA – way beyond the need to extract more capacity from a given slice of radio spectrum.  Their DNA, in fact, has roots in World War II, a Hollywood starlet and a tiny reptile from the Puerto Rican rain forest.