In the internet world, there are a large number of different smart devices connecting to the Internet. IoT devices are battery-powered, with minimal computing and storage resources. There are various communication challenges, which are as follows: 
  1. Addressing and identification: Many devices are connected to the internet, So this device can be identified through a unique address, on the basis of communication. So we need a large addressing space and a unique address for each smart object. 
  2. Low power communication: communication of data between devices is a power-consuming task, especially, wireless communication. So, we need a solution that provides communication with low power consumption. 
  3. Routing protocols with low memory requirements and efficient communication patterns.
  4. High-speed and non-lossy communication. 
  5. Mobility of smart things. 

IoT devices connect to the Internet through the IP (Internet Protocol) stack. The IoT devices can also connect locally through non-IP networks, which consume less power, and connect to the Internet via a smart gateway. Bluetooth, RFID, and NFC are non-IP communication and are limited in range (up to a few meters). So their applications are limited to small personal area networks. Personal area networks (PAN) are being widely used in IoT applications such as wearables connected to smartphones. The communication technologies used in the IoT world are IEEE 802.15.4, low power WiFi, 6LOWPAN, RFID, NFC, Sigfox, Lora WAN, and other proprietary protocols for wireless networks. 

Communication in IoT

Near Field Communication (NFC) 

Near Field Communication is a very short-range wireless communication technology, through which mobile devices can interact with each other over a distance of a few centimeters only. Data can be transferred between two NFC-enabled devices in seconds provided the devices are close to each other. This technology is based-on-RFID. NFC operates over a frequency band of 13.56 MHz, which is the same as high-frequency RFID. There are two modes of operation: active and passive. In the active mode, both the devices generate magnetic fields, while in the passive mode, only one device generates the field and the other uses load modulation to transfer the data. The strength of adjacency between devices is that it is very convenient for secure transactions such as payments.

Wireless Sensor Networks (WSN) 

The disadvantage of non-IP technologies such as RFID, NFC, and Bluetooth is that their range is very small. So, they cannot be used in many applications, where a large area needs to be monitored through many sensor nodes deployed in diverse locations. A wireless sensor network (WSN) consists of ten thousand sensor nodes connected using wireless technologies, They collect data and communicate it to the gateway. devices that relay. the informal to the cloud over the Internet. The communication between nodes in a WSN may be dir Or multihop. Gateway nodes have. sufficient power and processing resources, The network topologies used in a WSN are a star, a mesh, and a hybrid network. Most of the communication in WSN is based on the JEEE 802.15.4 standard. The use of WSN is as follows:- 
  • Weather monitoring systems use WSNs in which the nodes collect temperature humidity and other data which is aggregated and analyzed. 
  • Indoor air quality monitoring systems use WSNS to collect data on the indoor air quality and concentration of various gases. 
  • Surveillance systems use WSNS for collecting Surveillance data (such as motion detection data)
  • Structural health monitoring systems use WSNS to monitor the health of structures (buildings, bridges) by collecting vibration data from sensor nodes de deployed at various points in the structure. 

Bluetooth Low Energy (BLE) 

Bluetooth Low Energy, also known as "Bluetooth Smart," was introduced by the Bluetooth Special Interest. Group. It has a short-range and consumes low energy. The BLE protocol stack is similar to the stack used in classic Bluetooth technology. It has 2 parts: Controller and host. The physical and link layer are implemented in the controller. The controller is typically a SOC (System on Chip) with a radio, The functionalities of upper layers are included in the host. BLE is not compatible with classic Bluetooth. The difference between BLE and classic Bluetooth is that BLE supports the transfer of small packets of data very quickly with a data rate of 10 MBPS. 

There are two types of devices in BLE: master and slave. The master acts as a central device that can connect to various slaves. For an eg. A phone or PC act as the master and mobile devices such as a thermostat, fitness tracker, smartwatch, or any monitoring device act as slaves. In these cases, slaves must be very power efficient. Therefore, to save energy, slaves are by default in sleep mode and wake up periodically to receive packets from the master. 

In classic Bluetooth, if the data transfer is not in the running stage, but the connection is on all the time, it supports 79 data channels (10 MHz channel bandwidth) and a data rate of I million symbols/s, while, BLE supports 40 channels with 20 MHz channel bandwidth (double of classic Bluetooth) and 1 million symbols/s data rate.

Low Bower WiFi

The WiFi Alliance has recently introduced "WIFI Halow" which is based on the IEEE 802.11 ah standard. It consumes lower power as compared to traditional WiFi devices and also has a longer range. So this protocol is comfortable for IoT. The range of WIFI Halow is nearly twice that of traditional WiFi. 

Like other WiFi devices, WiFi HaLow also supports IP connectivity which is important for IoT applications for an eg: IEEE 802.11 ah standard was developed to deal with wireless sensor networks, where devices are energy-constrained and require relatively long Fangs communication. IEEE 802.11ah operates in the sub-gigahertz band (900 MHz). Because of the relatively lower frequency, the range is longer since higher frequency waves suffer from higher attenuation. IEEE 802.11ah is also designed to support large star-shaped networks, where a lot of stations are connected to a single access point. 

Integration of RFID and WSN

RFID and wireless sensor networks (WSN) are both important technologies in the IoT. RFID can only be used for object identification but WSN is a long-time technology. RFID is inexpensive and uses very little power. So its integration with WSN is very useful. 

Integration of RFID tags with sensors: RFID tags with sensing capabilities are called sensor tags. These sensor tags sense data from the environment and then the RFID reader can read this sensed data from the tag. In this case, simple RFID protocols are used, where there is only single-hop communication. 

Integration of RFID tags with WSN nodes: The communication capabilities of sensor tags are limited to a single hop. To extend its capabilities, the sensor tag is equipped with a wireless transceiver, a little bit of Flash memory, and computational capabilities such that it can initiate communication with other nodes and wireless devices. The nodes are connected to form a wireless mesh network. In these networks, sensor tags can communicate with each other over a large range. With additional processing capabilities at a node, we can reduce the net amount of data communicated and thus increase the power efficiency of the WSN. 

Integration of RFID readers with WSN nodes: This type of integration is also done to increase the range of RFID tag readers. The readers are equipped with wireless transceivers and microcontrollers so that they can communicate with each other and therefore, the tag data can reach a reader, which is not in the range of that tag. It takes advantage of multi-hop communication of wireless sensor network devices. The data from all the RFID readers in the network ultimately reaches a central gateway or base station that processes the data or sends it to a remote server.