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EDN Europe's Editor Graham Prophet posts a selection of comments and insights prompted by the many items of industry news and rumour that cross the editorial desk or are gathered on his frequent travels to interviews, press conferences and events around Europe - and further afield - and somehow never find their way to the magazine or the web site, recovering some of the information otherwise lost in the noise level...

Thursday, March 20, 2008

Minimising MIMO misery

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A conversation today with Anritsu’s Jonathon Borril, on the subject of testing MIMO. He’s been finding there’s a bit of, not so much confusion, as misunderstanding when it comes to testing MIMO systems – an increasing concern as data speeds increase in WCDMA, and looking forward to LTE. Some users, Jonathon says, expect to see multi-port RF test sets in the MIMO test context, and don’t entirely appreciate how much of the process of evaluating a MIMO configuration takes place at the algorithmic level. In a two-channel set-up you can verify that each of your individual channels is doing what it should in purely RF terms, and then move to the protocol level to check out the MIMO performance: you don’t need the full 2-channel RF set-up, up-and-running throughout.
This seems intuitively correct; after all, with MIMO, you put two radio channels on the same frequency through the same space – but nothing mysterious happens to the two signals in the ether, getting more than one channel’s worth of data out of the link depends on the algorithms that dynamically characterise the shifting multi-path channel between the transmitter(s) and receiver(s), and exploit the ability to use each sub-path independently.
There may be a “crossing of traditional boundaries” thing going on here – Jonathon says that the key to MIMO performance lies not in the higher (layer 3) levels of the protocol, or in the RF hardware – though they both matter – but in the protocol-layer-1, direct-control of the RF system, level. So it’s right in the middle between the areas of expertise of two different test regimes, according to the way things have been done in the 2- or 2.5-G world.
I’m going to look at this as a possible subject for a future issue of the magazine; what would you like to see such an article cover?

Related entries in: Communications | Test & Measurement |

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