Comparison of WiFi, Bluetooth Low Energy and Zigbee for wireless data transfer

We are surrounded by technologies that help us in sending and receiving information wirelessly. The information can be of varied type, size and importance ranging from a sensor reading in a control system to large data files like images, audio and videos. Due to these variations in information to be transferred and the context of transfer, there has to be different types of technologies to be used in different scenarios. Some of these technologies are WiFi, Bluetooth Low Energy, ZigBee, NFC, ANT, Nike+. Here we will explore the first three options, first with a brief overview and then a comparative study with respect to utility of transferring large files.

Wifi, Bluetooth Low Energy (BLE), Zigbee - A brief overview

Wifi

Wifi, short for Wireless Fidelity, is a wireless technology that uses radio frequency to transmit data across devices through air. Technically, Wifi is based on IEEE 802.11 standard and has several variants that include 802.11a, 802.11b, 802.11g, 802.11n and 802.11ac. These mentioned versions were released progressively through time which signifies incremental improvements in standards, in terms of speed and range. The following table summarizes the specifications in different variants.

The most common version of Wifi is the most recent one i.e. 802.11ac and you will find this in mostly all the mobiles, laptops and other devices taking leverage of WiFi.

Bluetooth Low Energy

Bluetooth Low Energy (BLE) is a low power variant of the widely known wireless transfer technology Bluetooth and is marketed as Bluetooth Smart. The low power consumption is achieved by changing the data protocol to create low duty cycle transmissions. BLE is aimed at very low power applications that can run off a coin cell battery for several months.

BLE uses the same 2.4 GHz ISM band radio frequencies as used by classic Bluetooth but with a much simpler modulation system. It uses frequency hopping to counter narrow band interference problem and uses forty 2 MHz wide channels for data transfer which ensures greater reliability over small distances.

BLE was merged with the classic Bluetooth standard and was launched as Bluetooth 4.0 in July 2010. Recently a more powerful version of BLE namely Bluetooth 5.0 was launched.

BLE 4.0 can achieve a maximum data transfer rate of 1Mbps while its successor BLE 5.0 is capable of 2Mbps. Although the range of bluetooth devices depend upon various factors such as surroundings, radio performances and antennas, surroundings play the most crucial variable. Outdoors in an open field, BLE 4.0 can give us a range of about 100 m while BLE 5.0 can do up to 400m but a realistic real world estimate of range can be taken of about 15-20m.

BLE since its inception supported Star type topology which is dynamic enough to support nodes dropping off and coming onto as they move out and in to range but cannot be extended to large areas as possible with mesh type topology. To counter this shortcoming, in July 2017, Bluetooth Mesh was announced which would extend the range of BLE.

Zigbee

ZigBee is a standard that defines a set of communication protocols for limited data rate and limited range of wireless networking. It is based on IEEE 802.15.4 standard and is used for two way communication between sensors and control systems.

It has a low data rate of about 250 kbps and operates at frequencies of 868 MHz, 902 to 928 MHz and 2.4 GHz. Zigbee technology is ideal for applications involving low power, low cost, low data rate and longer battery life. The modulation techniques in ZigBee depend upon the frequency of operation. For the 868 and 915 MHz bands the form of modulation is Binary Phase Shift Keying. For the 2.4 GHz band, Offset Quadrature Phase Shift Keying (O-QPSK) is employed.

ZigBee can work in Star as well as Mesh Topology. Due to its simplicity, Star topology is used frequently. In cases where the area of operation has to increase and more reliability is required, a Mesh topology is used which consist of a variety of nodes placed as needed, and nodes within range being able to communicate with each other to form a mesh.

A comparative study

Now that we know a bit about Wifi, BLE and ZigBee, we are ready to draw a comparison between these technologies through three main parameters (Speed, Transmission Range, Power Consumption) with a special focus on transfer of large data objects like images, audio, etc. wherever applicable.

Speed

Speed is one of the most important and discussed upon parameter in deciding on the best alternative for an application. Out of the three, ZigBee has the lowest data transfer rate of about 250 kbps and is ideal for applications like sending sensor data through a control system. BLE does better in speed, with a maximum data rate of 2Mbps which makes it appropriate for sending small amounts of data like GPS coordinates, acceleration details etc. but is still not appropriate for sending large files. WiFi on the other hand is optimized for large data transfers giving speeds of up to 1000Mbps and finds its application in sharing large data files, streaming videos etc.

Thus, in case of large data objects from speed point of view, WiFi is our go to option.

Transmission Range

Transmission range is another important factor considered to shortlist the technology for our application. Although ZigBee in isolation has a very limited range but it supports Mesh topology (Routed Mesh) that enables it to cover large areas thus making it an ideal candidate for IOT applications like home automation. The newest version of Bluetooth also announced the mesh network topology (Flooded mesh, a more complicated approach to meshing) but still would cover areas less as compared to a routed ZigBee mesh. WiFi on the other hand only supports Star and peer to peer topologies which limits it's range to a maximum of 150m.

If you have devices exchanging a lot of large object data, neither ZigBee nor BLE would be appropriate despite of their topologies due to their low data rate, thus making WiFi the optimal choice.

Power Consumption

Both, BLE and ZigBee were designed as low-power technologies and were aimed at devices and applications which were required to run over large intervals of time without intervention. Although power consumption depends upon the application, both of these technologies offer comparable power consumption and can last for months or even years. WiFi on the other hand consumes a lot more power than ZigBee and BLE and is used for more heavy duty applications due to its high transfer rate.

On a uniformly scaled application, the power consumption of BLE, ZigBee and WiFi were respectively 72 microwatts, 90 microwatts and 0.2 Watt. WiFi consumes a lot of power and even consuming power if it is idle. The power efficiency figures speak out in favour of WiFi due to its high data transfer rate. (75 nJ/bit, 360 nJ/bit, 5.25 nJ/bit)

Conclusion

The three technologies WiFi, BLE and ZigBee are used in different applications selected by the requirements.

• For an application that requires modest data transfer and a limited range of operation with a long battery life, BLE is the way to go. One of the possible scenarios may be to automate a limited closed area for example a car with features of automatic unlocking etc. once the user is close to it.
• If the requirements boil down to low data transfer over a long range with a long battery life then ZigBee is the way to go. A possible scenario would be to automate a large building using mesh networking of ZigBee.

If the application requires large amount of data transfer then a compromise on range and battery has to be made, thus making WiFi the only realistic option to consider.

This concludes our comprehensive overview of these fascinating technologies. Do you want to know something about other wireless technologies that we missed or did not discuss comprehensively? Express your curiosity! Just log in or register to comment below!