Advantages of D2D communication | Disadvantages of D2D communication

This page covers advantages and disadvantages of D2D communication used in LTE and 5G NR. It mentions benefits or advantages of D2D communication and challenges or disadvantages of D2D communication.

What is D2D communication?

The D2D i.e. Device to Device communication feature allows communication between two UEs (User Equipments) with or without the network (i.e. Access Point (AP) or Base Station (BS)). The devices can be cell phones or vehicles. The devices should be in close proximity to communicate using direct link.

It has been introduced in LTE specification as extension where as in 5G, it is explored as integral part of overall wireless access solution. The short range wireless technologies which use D2D communication are WiFi direct, Bluetooh, LTE direct etc.

In this technique, network authorizes the two devices to communicate directly with each other under its control. In D2D, network has control over devices and it allows operator to determine traffic routing between direct path and network path. Hence during unavailability of network, devices can communicate directly.

D2D is classified mainly in two types viz. Inband D2D and Oueband D2D. In Inband D2D, same licensed spectrum is used for both cellular communication and D2D communication. In Outband D2D, D2D uses unlicensed spectrum where cellular communication does not take place.

There are two types of communication in D2D viz. single hop and multi-hop. In single hop communication, tranmitting UE and receiving UE connect with each other directly. In multi hop communication, intermediate UEs act as relays either between "BS and UE" or between "two UEs".

There are many use cases of D2D which include local data services, data offloading, coverage extension, M2M communication etc.

Benefits or advantages of D2D communication

Following are the benefits or advantages of D2D communication:
➨It offers ultra low latency communication. Hence it offers more reliable connectivity between devices.
➨It solves network capacity issue of cellular system due to direct device connectivity without involving network.
➨It extends coverage. For example, If any UE#1 is at the cell edge, it receives poor signal from network. In this scenario, another nearby UE#2 provide better signals to UE#1 and consecutively extends the coverage.
➨Using D2D, one UE#1 provides service to the other UE#2. For example, if there are two UEs viz. UE#1 and UE#2 connected with the BS or eNB. If the connection from UE#2 breaks with BS, UE#1 serves as relay to provide information to UE#2.
➨D2D connectivity makes operators more flexible as it allows to offload traffic to devices from the core network. This increases spectral efficiency and reduces energy and cost per bit.
➨In 5G, D2D uses mmwave frequencies which allows many D2D links to operate simultaneously due to its robustness against multi user interference.
➨D2D communication offers stronger security than conventional cellular communication as data are not stored at central location.

Challenges or disadvantages of D2D communication

Following are the challenges or disadvantages of D2D communication:
➨UEs get themselves synchronized using periodic broadcasts from BS. In certain situations, it is difficult for UEs to communicate due to synchronization issue. For example, UEs belong to different BSs or some UEs are in the coverage and some are outside or all UEs lie outside coverage.
➨Peer discovery algorithm used in D2D is challenging in multicell network in which getting cooperation from adjacent BSs is difficult.
➨Interference management is crticial task in D2D. In Inband D2D communication, cellular link and D2D link interfere with each other. In Outband D2D communication, D2D links interfere with each other as well as with other devices using the same band. UEs transmit low power to reduce the interference but at the cost of QoS (Quality of Service).
➨The most common issue with cellular operators is how to charge the users.
➨Though D2D provides better security, it is prone to attacks such as eavesdropping, IP spoofing, denial of service, malware attack etc.