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Friday, June 6, 2008

What If Single Frequency

In my last post, I praised the move of GE Health lobbying FCC for a dedicated freq band for body area network (BAN) that requires ultra low power, low cost, privacy etc. Here I'd like to take a detailed look of the benefits that single frequency operation will bring to wireless sensor networking.

1. No need to worry about frequency jam. Frequency hopping scheme and the related strict synchronization are largely unnecessary. The protocol will then mainly deal with cross-talking and peer network co- existing. This is a save of about 10k code just for a point to point connection.

2. Because of fixed frequency, TDMA kind of channelization would become one of the few options, which is relatively easy and does not demand much computation. Low cost MCU could be used.

3. Network topology can be more flexible and easy to achieve. Searching a network and establish a link would become easy and fast. Robustness can be guaranteed to certain extend simply by data acknowledgment and resending.

4. RF design and signal filtering can be optimized to that particular narrow band, simplifying the design and saving a lot hardware cost.

Many proprietary protocols serving a market niche, , like ANT, Z-Wave and the Nordic Semiconductor's wireless desktop, some even in the 2.4GHz crowded band, realize what is "good enough" and what can be traded-off through their own practice and through learning lessons from its competition standards. These solutions, though have frequency agility, are not build it in their chips, but offered through reference designs or application notes. They all have achieved better marketing performance.

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