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Wi-Fi vs Bluetooth vs LPWA: Range, Data Rate and Power

All three connect devices by radio, but they balance range, speed and power consumption differently. Wi-Fi is the IEEE 802.11 wireless LAN that connects PCs and smartphones to the internet at high speed. Bluetooth connects earphones, keyboards, wearables and similar devices directly over short distances of a few meters to tens of meters, and its low-power variant BLE (Bluetooth Low Energy) is also used in sensors that run on coin cells. LPWA is the umbrella term for IoT networks that give up speed to reach distances of several kilometers or more with battery life measured in years.

AspectWi-FiBluetoothLPWA
StandardsIEEE 802.11 (certified by the Wi-Fi Alliance)Specified by the Bluetooth SIG; includes classic BR/EDR and low-power BLE (Bluetooth Low Energy)An umbrella term: LoRaWAN and others in license-free bands, and LTE-M, NB-IoT and others in cellular bands
Frequency bands2.4 GHz and 5 GHz bands (also 6 GHz from Wi-Fi 6E)2.4 GHz bandMainly sub-GHz bands (920 MHz in Japan) or cellular bands
Typical rangeTens of meters indoorsA few meters to tens of meters (over 100 m with some power levels and modes)A few kilometers to more than ten kilometers (depending on line of sight and environment)
Typical data rateTens of Mbps to several Gbps (depending on the generation and conditions)Up to 1 to 2 Mbps for BLE (actual throughput is lower); up to 3 Mbps for BR/EDRA few hundred bps to a few hundred kbps (up to about 1 Mbps for LTE-M)
Power consumptionHigh; suited to devices on mains power or recharged oftenModerate for BR/EDR; BLE communicates briefly and sleeps, so some devices run for months to years on a coin cellVery low; with little data to send, several years to about 10 years on a battery is typical
TopologyStar around an access point, which connects to the LAN and the internetDirect one-to-one or one-to-many links with a smartphone or similar; also beacons using advertising, and meshStar from devices to base stations (gateways); small amounts of data, mainly from devices to the cloud
Use of the radio channelMainly OFDM (plus OFDMA from Wi-Fi 6) and MIMO; CSMA/CA coordinates transmissions, and RTS/CTS deals with hidden nodesFrequency hopping (79 channels of 1 MHz for BR/EDR, 40 channels of 2 MHz for BLE)Lowers the data rate so that signals near the noise level can still be received (LoRa chirp spread spectrum, narrowband modulation and others)
Licensing and serviceNo license needed; you install your own access pointNo license needed; devices connect directlyLoRaWAN and similar need no license and you can install your own gateway; LTE-M and NB-IoT use an operator's network under a service contract
Typical usesInternet access for PCs and smartphones, video streaming, networking appliances and camerasWireless earphones, keyboards and mice, smartwatches, beacons, healthcare devicesReading electricity, gas and water meters, sensors on farms and equipment, asset tracking

Figures are typical orders of magnitude and vary by process generation and product.

When to use which

Wi-Fi
When large amounts of data must be sent quickly or devices must connect directly to the internet. It suits devices on mains power or devices that are recharged.
Bluetooth
When connecting peripherals right next to a smartphone or PC. For sensors and wearables that must run long on batteries, use BLE.
LPWA
When small amounts of data must be sent far, from places without power, on batteries for years. It does not suit real-time control or sending images and video.

FAQ

Do Wi-Fi and Bluetooth interfere with each other in the 2.4 GHz band?

They share the 2.4 GHz band, so they can interfere. Bluetooth reduces the impact by frequency hopping, changing frequency constantly, and by adaptive frequency hopping, which avoids busy channels. Using Wi-Fi in the 5 GHz band avoids congestion in the 2.4 GHz band. Microwave ovens also emit in the 2.4 GHz band, so communication can be disrupted near one.

Why can LPWA reach so far with so little power?

It greatly lowers the data rate to increase the energy per bit and narrows the receive bandwidth to reduce noise, so weak signals can still be received. In addition, a sub-GHz band such as 920 MHz in Japan has about 8 dB less free-space path loss than the 2.4 GHz band when antennas of the same gain are compared, and diffracts more easily around buildings. Power consumption is low because devices send little data and sleep almost all the time.

How does BLE differ from classic Bluetooth?

BLE cuts power by keeping communication very short and switching the circuits off the rest of the time, which suits sensors and beacons that send small amounts of data intermittently. Classic Bluetooth (BR/EDR) has been used for continuous streams such as audio. Both use the 2.4 GHz band, but their protocols differ, so they cannot talk to each other directly (some devices support both).

How do Wi-Fi standard names map to generation names?

IEEE 802.11n is called Wi-Fi 4, 802.11ac Wi-Fi 5 and 802.11ax Wi-Fi 6; 802.11ax extended to the 6 GHz band is Wi-Fi 6E. 802.11ac uses only the 5 GHz band, while 802.11n and 802.11ax use both the 2.4 GHz and 5 GHz bands.

Check your understanding

With transmit and receive antenna gains of 0 dBi, which is closest to the free-space path loss when a 2.4 GHz radio wave (wavelength 0.125 m) travels 100 m through free space?

  1. A40 dB
  2. B60 dB
  3. C80 dB
Show answer and explanation

Answer: C. 80 dB

Free-space path loss is the rate at which power weakens between isotropic antennas as it spreads out spherically with distance, given by L = (4πd/λ)². With d = 100 m and λ = 0.125 m, 4πd/λ ≈ 1.0×10⁴, so L = 20·log₁₀(1.0×10⁴) ≈ 80 dB. In dB, the loss grows by about 6 dB each time the distance doubles and by 20 dB each time it increases tenfold. In this formula, at the same distance the loss is larger at higher frequency (shorter wavelength).

Which frequency band does an IEEE 802.11ac (Wi-Fi 5) wireless LAN use?

  1. AOnly the 2.4 GHz band
  2. BBoth the 2.4 GHz and 5 GHz bands
  3. COnly the 5 GHz band
Show answer and explanation

Answer: C. Only the 5 GHz band

Each IEEE 802.11 standard specifies the bands it uses. 802.11b and 802.11g use the 2.4 GHz band, 802.11a and 802.11ac use the 5 GHz band, and 802.11n (Wi-Fi 4) and 802.11ax (Wi-Fi 6) use both the 2.4 GHz and 5 GHz bands. 802.11ax extended to the 6 GHz band is called Wi-Fi 6E. Even on an access point supporting both 2.4 GHz and 5 GHz, 802.11ac communication takes place only on the 5 GHz side.

Which describes the RTS/CTS mechanism used to mitigate the hidden node problem in wireless LANs?

  1. AA terminal that wants to transmit sends a request to send (RTS), and the access point returns a clear to send (CTS); nearby terminals that receive the CTS refrain from transmitting for the duration of that exchange
  2. BA terminal monitors the received signal while transmitting and stops immediately if it detects a collision
  3. CAll terminals transmit at maximum power so that their signals reach one another
Show answer and explanation

Answer: A. A terminal that wants to transmit sends a request to send (RTS), and the access point returns a clear to send (CTS); nearby terminals that receive the CTS refrain from transmitting for the duration of that exchange

The hidden node problem occurs when signals from both terminals reach the access point, but the terminals cannot hear each other because of distance or obstacles. Unaware of each other's transmissions, they judge the channel to be free, transmit at the same time and collide at the access point. With RTS/CTS, the CTS returned by the access point states how long the exchange will take, and terminals that receive the CTS refrain from transmitting for that time. The RTS/CTS exchange costs efficiency, so it can be configured to be used only when sending large frames.

  1. Which describes Bluetooth Low Energy (BLE)?
  2. Which is a characteristic of LPWA (low-power wide-area) wireless communication used in IoT?
  3. Take the thermal noise power density at 290 K as −174 dBm/Hz. For a receiver with a bandwidth of 1 MHz and a noise figure of 6 dB that needs an S/N of 10 dB to demodulate, which is closest to the receiver sensitivity (the minimum signal power that can be received)?

Practice Wireless Communication Basics questions

Key terms explained

Wi-Fi
The common name for wireless LANs based on the IEEE 802.11 standards; the name shows that a device is certified by the industry group Wi-Fi Alliance. It mainly uses the 2.4 GHz, 5 GHz and 6 GHz bands and connects devices to a LAN through access points. Access to the air is coordinated with CSMA/CA, and speed and efficiency come from OFDM, MIMO and, from Wi-Fi 6 (802.11ax), OFDMA. Traffic is encrypted with WPA2 or WPA3.
Bluetooth Low Energy (BLE)
The variant of the 2.4 GHz short-range wireless technology Bluetooth that emphasizes low power consumption. By keeping communication time very short and shutting down circuits the rest of the time, devices can run a long time even on coin cells. It is used in beacons that periodically send short signals called advertisements, in wearables, sensors and more. It cannot communicate directly with classic Bluetooth (BR/EDR).
LPWA (low-power wide-area)
A general term for wireless communication intended to send small amounts of data, such as sensor readings, from devices that run on batteries for years to places several kilometers or more away. Keeping the transmission rate low allows even weak signals to be received, extending the range. Some, such as LoRaWAN, use license-exempt bands (such as the 920 MHz band in Japan), while others, such as LTE-M and NB-IoT, use mobile phone bands.
OFDM (orthogonal frequency-division multiplexing)
A scheme that splits data across many mutually orthogonal subcarriers, modulates each at a low symbol rate and sends them in parallel. Setting the subcarrier spacing to the reciprocal of the symbol length lets the subcarriers be separated without interfering even though their spectra overlap. It is robust against multipath and is used in wireless LANs, 4G LTE, 5G NR, digital terrestrial broadcasting and more.
Hidden node problem
A problem in wireless LANs that occurs when signals from two terminals both reach the access point but the terminals cannot hear each other because of distance or obstacles. Unaware of each other's transmissions, they transmit at the same time and collide at the access point. It is mitigated by RTS/CTS, in which the CTS returned by the access point makes nearby terminals hold off transmitting.
Free-space path loss (FSPL)
The rate at which radio power weakens as it spreads out spherically with distance between isotropic antennas in free space with no obstacles or reflections. It is given by L = (4πd/λ)², and in dB it grows by about 6 dB each time the distance doubles and by 20 dB each time it increases tenfold. It is used as the reference propagation loss in link budget calculations.
Link budget
A calculation that adds up the gains and losses from transmit power to received power to estimate the power reaching the receiver and the margin over the power needed for reception (the sensitivity). It is done in dB and dBm by adding and subtracting terms such as transmit power + antenna gains − propagation loss − cable loss. The same approach is used for power budgets in optical communication as well as radio.

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