Introduction of IEEE 802.15.4 Technology
IEEE 802.15.4 is a low-cost, low-data-rate wireless access technology for devices that are operated or work on batteries. This describes how low-rate wireless personal area networks (LR-WPANs) function.
1. Standardization and alliances –
It specifies low-data-rate PHY and MAC layer requirements for wireless personal area networks (WPAN).
IEEE 802.15. Protocol Stacks include –
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- ZigBee IP
- Wireless HART
2. Physical Layer-
This standard enables a wide range of PHY options in ISM bands, ranging from 2.4 GHz to sub-GHz frequencies. IEEE 802.15.4 enables data transmission speeds of 20 kilobits per second, 40 kilobits per second, 100 kilobits per second and 250 kilobits per second. The fundamental structure assumes a 10-meter range and a data rate of 250 kilobits per second. To further reduce power usage, even lower data rates are possible. IEEE 802.15.4 regulates the RF transceiver and channel selection, and even some energy and signal management features, at the physical layer. Based on the frequency range and data performance needed, there are now six PHYs specified. Four of them employ frequency hopping techniques known as Direct Sequence Spread Spectrum (DSSS).
3. MAC layer –
The MAC layer provides links to the PHY channel by determining that devices in the same region will share the assigned frequencies. The scheduling and routing of data packets are also managed at this layer. The 802.15.4 MAC layer is responsible for a number functions like:
- Beaconing for devices that operate as controllers in a network.
- used to associate and dissociate PANs with the help of devices.
- The safety of the device.
- Consistent communication between two MAC devices that are in a peer-to-peer relationship.
Several established frame types are used by the MAC layer to accomplish these functions. In 802.15.4, there are four different types of MAC frames:
- frame of data
- Frame for a beacon
- Frame of acknowledgement
- Frame for MAC commands
4. Topology –
Networks based on IEEE 802.15.4 can be developed in a star, peer-to-peer, or mesh topology. Mesh networks connect a large number of nodes. This enables nodes that would otherwise be out of range to interact with each other to use intermediate nodes to relay data.
5. Security –
For data security, the IEEE 802.15.4 standard employs the Advanced Encryption Standard (AES) with a 128-bit key length as the basic encryption technique. Activating such security measures for 802.15.4 significantly alters the frame format and uses a few of the payloads. The very first phase in activating AES encryption is to use the Security Enabled field in the Frame Control part of the 802.15.4 header. For safety, this field is a single bit which is assigned to 1. When this bit is set, by taking certain bytes from its Payload field, a field known as the Auxiliary Security Header is formed following the Source Address field.
6. Competitive Technologies –
The IEEE 802.15.4 PHY and MAC layers serve as a basis for a variety of networking profiles that operate in different IoT access scenarios. DASH7 is a competing radio technology with distinct PHY and MAC layers.
Advantages of IEEE 802.15.4 :
IEEE 802.15.4 has the following advantages –
- cheap cost
- long battery life,
- Quick installation
- extensible protocol stack
Disadvantages of IEEE 802.15.4 :
IEEE 802.15.4’s drawbacks include –
- IEEE 802.15.4 causes interference and multipath fading.
- doesn’t employ a frequency-hopping approach.
- unbounded latency
- interference susceptibility
Applications of IEEE 802.15.4 :
IEEE 802.15.4 Applications –
- Wireless sensor networks in the industry
- Building and home automation
- Remote controllers and interacting toys
- Automotive networks