What is device-to-device communication?
Device-to-device communication is an advanced data transmission technology developed to increase the efficiency of the network. In LTE-Direct, D2D communication-enabled devices can interact with each other using a secure transmission protocol similar to the devices communicate with the base station.
Where D2D is required
In order to have stable communication and uninterrupted service, mobile devices must be within the proximity of the base station. Proximity doesn’t only refer to physical distance, often referenced as signal strength received at a mobile device (UE).
Due to higher interference from surroundings and sometimes due to signal-blocking physical structures like concrete walls or locations like basements, received signal strength would be lower than required. Device-to-device communication technology is the best solution to improve the signal proximity scenario.
If any device is connected to the mobile network, it can act as a relay station to other device(s) not under direct proximity of base station to establish a connection to the core network.
How does D2D communication works?
Device-to-device communication can be achieved in multiple modes of operation depending on the scenarios. According to the situation, most suitable operation mode will be chosen to establish efficient transmission.
Scenario 1: If two devices are in proximity, they can start communicating, like sharing data. This helps to improve data rate, reduce power consumption of devices, and reduce total load reduction of base stations. The control will be handled by the base station.
Scenario 2: During the absence of an active mobile network connection or insufficient signal reception, D2D-enabled devices can establish an alternative communication interface with their surrounding devices, which are connected to mobile base stations. It will help the node with no coverage to maintain a connection to the mobile network.
Scenario 3: Multiple devices can connect to a device that has an active connection to the base station and further extend this network by adding connections to more devices. All devices in this small mobile cloud will receive the same data in the form of advertising or messages from the source.
Scenario 4: In this case, multiple devices are offloaded to a Wi-Fi data connection for communication. Control signals to devices (UE) will be handled by the base station. Wi-Fi offloading offers a much higher data rate, less power consumption, and avoids traffic overload of base stations.
Other Scenarios: Device-to-device communication can be efficiently implemented for machine-to-machine communication where each machine can talk to other machines in its proximity. D2D communication is used in vehicle-to-vehicle communication and peer-to-peer communication applications in the same way. In all these cases, one node will connect to the main base station (transmitting station), and other devices form a small network to communicate with each other.
Standardization Groups for LTE and WLAN
LTE Proximity Services (ProSe) handles two tasks
- Device-to-device discovery: responsible for physical proximity, signal-to-noise ratio, delay, density, and load.
- Device to Device communication: it initiates communication between devices under its proximity.
- Infrastructure Service Discovery Study Group: centralized protocol for WLAN network based on Point Coordination Function (PCF) access mechanism.
Advantages of D2D communication
- Increased network efficiency
- Less power consumption and long battery life
- Efficient traffic load management
- The connection can be established even during the absence of a network
- Network extension without adding complex hardware like base stations
- Applications of D2D communication
- Public safety and security services
- Machine to machine peer to peer communication
- Vehicle-to-vehicle communication and autonomous driving applications
- Cellular offloading (to WLAN network for faster data transfer)
- Gaming and local social networking
- Content distribution, local advertisement, and location-aware services
- Local area emergency broadcast and warning messages
Limitations of D2D communication
Complex algorithms are required to handle devices without interference efficiently. Signal transmission power to a particular device needs to be increased from the base station to overcome surrounding interference.
D2D communication is a proximity-based protocol; thus, the distance between devices is limited due to power requirements.
Device compatibility and network capability are necessary to support D2D protocol.
Despite the fact that D2D communication effectively improves network efficiency, it also raises concerns about security and privacy. High-level encryption techniques and transmission protocols have to be implemented to protect information concerning users.
Significance in future applications
Device to device communication is one the effective ways to improve network efficiency, and the suggested technique (LTE-Direct) to offload base station traffic in LTE advanced and future networks. D2D communications are significant in applications like self-driving cars, machine-to-machine communications, and other Internet of Things applications.
5G technology will make use of D2D communication for a wide range of applications. The Internet of Things will connect billions of smart things (devices and sensors) to the Internet. D2D communication can be implemented in IoT applications for low-power mesh networking and smart sensor clouds.
Mission-critical applications are among the most significant applications of D2D communication. During an emergency situation, network availability might be limited or unavailable. D2D communication enables users to connect to the nearest devices and interact with each other even during the absence of a mobile network.