Why does Wi-Fi have so much more bandwidth than Bluetooth? [closed]

Question

While researching wireless communication protocols for a potential application, I came across this page on Wikipedia which lists throughput rates for both Bluetooth and 802.11 networks: http://en.wikipedia.org/wiki/List_of_device_bit_rates

Here is a relevant selection from the link:

• 1 Mbps - Bluetooth 1.1
• 3 Mbps - Bluetooth 2.0+EDR
• 24 Mbps - Bluetooth 3.0, Bluetooth 4.0
• 54 Mbps - 802.11a
• 600 Mbps - 802.11n

Why does Bluetooth have so little throughput compared to the Wi-Fi standards?

Is it simply because the standard set by the governing body intentionally sets a lower data transfer rate in order to allow hardware costs to stay low?

Is it possible we could get a "Bluetooth 5" with bandwidth on the order of 802.11a or 802.11n, or is there some deliberate design decision that results in low transfer rates (e.g. sacrificing speed in favor of low power consumption)?

Edit: to be clear, I understand that the listed data rates are theoretical maximums and do not reflect real world performance.

Collis

Answer 1

Both Bluetooth and WLAN [802.11] operates on ISM band 2.4GHz. additionally WiFi has a version that operates on 5 Ghz band too.

1] Why WiFi has more bandwidth or speed than Bluetooth?

Because WiFi is designed to have more speed than Bluetooth. The factor which makes the difference is power usage. Bluetooth is designed as a technology that uses very low amount of power. So data rates are restricted in the PHY [physical layer used by Bluetooth] to achieve this low power usage. Basically Bluetooth's PHY layer uses low data rate's because low data rate require very little power.

WiFi is designed as a wireless rival of Ethernet. So bandwidth [speed] matters. So WiFi's physical layer [PHY] is designed to have higher data rates. Higher data rates means more power, this also means your devices battery power will be drained faster.

2] Is it possible to have Bluetooth-5 with more bandwidth than 802.11-n?

Absolutely possible, if Bluetooth protocol stack is placed on top of a higher bandwidth PHY, Bluetooth will achieve higher bandwidth.

There is a technology called AMP [Alternate MAC PHY] as part of Bluetooth spec 4.0 [if my memory is correct], where Bluetooth protocol stack sits on top of WLAN [802.11] MAC. This approach was to solve Bluetooth's bandwidth problem. AMP is not used by many people today I guess.

3] PHY Data rates and achievable data rates

The rates advertised [54 mbps - 802.11 a] is the maximum raw throughput achievable at PHY level , in "ideal channel conditions". Which means in labs. typically when we use it in real world, there will be interference and so retries. This will reduce the bandwidth. also the protocol stack layer and applications on top of PHY will add latency on top of it. typically with a best performing implementation of 802.11a , the maximum achievable application level throughput in real world scenarios is around 40 MBPS.

Hope it helps. I am happy to answer more, if you got more questions on this.

Haruspicy

Thank you for your detailed answer! Do you have any sources you can cite regarding the design decisions? – Collis

I don't have any resources on top of my head now. But you can always google to find some. Bluetooth and WiFi specifications are available to download. Again there are lots of books explaining these technologies. If you don't have much expertise in reading Specifications, I suggest you to read books. books explain technologies well. "Bluetooth - Connect without cables" is a very famous book about Bluetooth. I don't remember any WiFi book, but please google. And don't hesitate to ask , I am happy to answer what I know. – Haruspicy

@Haruspicy 1. Bluetooth has lower speed than WiFi not because of power but because of narrower channels. Lower power affects the range, not speed. 2.Bluetooth over WiFi is called BTHS (Bluetooh High-Speed) and it's an extension of BT v3.0. – Gabriel

Answer 2

There are many differences between Bluetooth and WiFi protocols, most of them affect the throughput. However, the most important factor is the channel bandwidth. Bluetooth operates at 1MHz channels, while WiFi uses 20MHz and 40MHz channels, effectively providing much better throughput. Both BT and WiFi have power saving schemes (and many other properties) which affect the throughput but these are secondary to channel width.

Gabriel

How does the channel bandwidth affect the throughput? My guess was that a transmission frequency of X hz means X * (some scale value) bits can be transmitted per second. Is that more or less correct? – Collis

Also, why would one choose a 1MHz channel instead of a 20MHz channel for data transmission? – Collis

There is a carrier band, e.g. 2.4GHz. On top of this band, channels are defined. Each transmission is performed on a specific channel. The wider the channel is, the more data can be transferred per second. Think of it as per unit of time the transmission uses a larger portion of the available medium. E.g., a 20MHz WiFi channel can occupy the 2.400-2.420GHz. But a 1MHz BT channel will occupy only the 2.400-2.401GHz range. It's like a wider road can pass more traffic than a narrow one. – Gabriel

Regarding the choice of channel width - that's a question to the BT standards committee :) – Gabriel

I suppose the heart of my question is really this: "what, if anything, is gained by selecting a narrower channel?" Are there no well-known benefits, or is generally regarded as an arbitrary decision made by the BT standards committee? – Collis

I would guess it's mostly related to regulations. The RF ranges are an expensive resource which can't be used wastefully. Otherwise there would be a havoc in the air and interferences between various RF standards would make the communication unfeasible. – Gabriel

What do you mean with 10 MHz or 20 MHz channels? Isn't the operating frequency 2.4 Ghz as explained above? Thanks – Armour

@Lupocci - 2.4GHz is the baseband frequency and operating frequencies are represented by channels where each channel occupies a predefined width. E.g. in legacy WiFi channels can be either 20MHz or 40MHz-wide. So for example (purely artificial), we can have a 20MHz channel between 2390MHz and 2410MHz. – Gabriel

The newer WiFi standards use a modulation called OFDM, in which data is effectively sent over tens or hundreds of closely spaced channels in parallel. On each channel, WiFi uses more different transmission power levels to encode more data. More channels requires more power, separating the channels requires additional computation, and more different transmission power levels also requires more power. So the difference stems from energy usage and simplicity, and simplicity = smaller (cheaper/less power hungry) chips. – Brakeman

@Brakeman WiFi channels are not OFDM "channels" – Gabriel

@Gabriel no, indeed. Wikipedia calls it multiple closely spaced carrier frequencies. I guess you could say that OFDM divides up its channel into many narrow sub-channels. – Brakeman