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I'm thinking of building a signal beacon designed to be used indoors. The transfer speed isn't critical but range and penetrative ability are. Does anyone know if Bluetooth 4 or 802.11b/g/n might be better for this application? In both cases, there won't be an external antenna. I know antenna length affects WiFi signal strength, but how about Bluetooth?

I also know Apple chose Bluetooth for their iBeacons, but I think their decision focused on energy saving instead.

Thanks

Kar
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  • The range depends on the frequency used (2.5 GHz or 5 GHz for example), the presence other disturbing signals in the same frequency band, the materials the building is constructed from (metal, concrete = bad). An internal antenna or a longer antenna does not mean you will get a stronger signal. You could but the antenna would direct it, so stronger on one side, weaker on other side. – Bimpelrekkie Jul 02 '15 at 07:14
  • Sure. It'll be 2.5ghz. So I wonder if Bluetooth or WiFi could penetrate through (brick, concrete) walls better. – Kar Jul 02 '15 at 07:19
  • Both are 2.5 GHz so... – Bimpelrekkie Jul 02 '15 at 07:49
  • The frequency doesn't solely determine range and penetrability, right? Different versions of Bluetooth alone provide different ranges. – Kar Jul 02 '15 at 07:52
  • Well, it's an important factor ! But also there's datarate, modulation type, antenna radiation pattern, channel used. Properties of both transmitter and receiver. It depends on many factors. In general WiFi is more suited to longer range but if there's a lot of interference from other devices, bluetooth might work better as it does frequency hopping which Wifi does not. You cannot determine beforehand which will work better in your situation. You will have to try it out. – Bimpelrekkie Jul 02 '15 at 07:59

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Well, "I'm thinking of building a signal beacon designed to be used indoors."
Indoor can be an 3 bedroom apartment or an entire factory or a huge parking lot.

Majority of the Bluetooth Low Energy module manufacturers claim to have achieved a 100 m line-of-sight range with On-chip (No external) antenna. I have evaluated 3 different BLE modules from one the most reputed wireless solution providers, and have managed to communicate to about 90 m line-of-sight and 75 m with walls and pillars in between.
All this while, the company WiFi was ON and there were many a guys with cellular phones with their Bluetooth turned ON.

Bluetooth protocol divides the band into 79 channels (each 1 MHz wide) and changes channels up to 1600 times per second. Bluetooth implements Adaptive Frequency Hoping. Read the story from Horse's mouth itself: Bluetooth standard page: Bluetooth Basics

Interference:

Bluetooth technology's adaptive frequency hopping (AFH) capability was designed to reduce interference between wireless technologies sharing the 2.4 GHz spectrum. AFH works within the spectrum to take advantage of the available frequency. This is done by the technology detecting other devices in the spectrum and avoiding the frequencies they are using. This adaptive hopping among 79 frequencies at 1 MHz intervals gives a high degree of interference immunity and also allows for more efficient transmission within the spectrum. For users of Bluetooth technology this hopping provides greater performance even when other technologies are being used along with Bluetooth technology.

Range: Range is application specific and although a minimum range is mandated by the Core Specification, there is not a limit and manufacturers can tune their implementation to support the use case they are enabling. Range may vary depending on class of radio used in an implementation:

+ Class 3 radios – have a range of up to 1 meter or 3 feet
+ Class 2 radios – most commonly found in mobile devices – have a range of 10 meters or 33 feet
+ Class 1 radios – used primarily in industrial use cases – have a range of 100 meters or 300 feet

Adaptive Frequency Hopping (AFH) is a built-in coexistence feature that is found in most Bluetooth devices today. With AFH, a Bluetooth radio scans the operating band for interference and adapts its frequency hopping patterns to avoid DSSS channels. This decreases interference (and therefore increases performance) between Bluetooth and Wi-Fi radios.

Speaking of 802.11 solutions, the kind of modulation 802.11b inhibit is DSSS and that of 802.11g is DSSS/OFDM, so they can control their interference and susceptibility to interference by using signaling methods.

So, to answer your real question "Does anyone know if Bluetooth 4 or 802.11b/g/n might be better for this application?"
I'd say, "It depends on what and how is the indoor term used. Be assured, interference is well managed and not an issue to fret about."

WedaPashi
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