Currently, Wi-Fi and Bluetooth provide some D2D communications functionality, but because these work in unlicensed band, the interference can be come uncontrollable. Another drawback is that unlike cellular network, they cannot provide security and QoS guarantee.
One of the features of 5G network is support for device-to-device (D2D) communications. When a device communicates via the base station, it is operating at the macro cell level; if a device communicates directly with another device, it is operating at the device level. In congested areas and at the cell edge, devices can create an ad hoc mesh network so that they can communicate with each other. There are four types of device level communication.
- Device relaying with BS-controlled link information. This is for a device that is at the cell edge, where the signal strength might be poor. The device communicates with the BS by relaying information through another device. Doing this helps the device to maintain a high QoS and battery life. The BS communicates with the relaying device for partial or full control link formation.
Device relaying with BS-controlled link information (Gupta and Jha, 2015) 
- Direct D2D Communication with BS-controlled link information. The source and destination devices exchange data without involving the BS, but the BS controls the link formation between them.
Direct D2D Communication with BS-controlled link information (Gupta and Jha, 2015) 
- Device relaying with device-controlled link formation. The BS is not involved in the link formation or any communication purpose. The source and destination devices are responsible for synchronizing communications using relays between them.
Device relaying with device-controlled link formation (Gupta and Jha, 2015) 
- Direct D2D communication with device-controlled link formation. The source and destination devices communicate directly with each other and the link formation is controlled by the devices without any assistance from the BS. Utilisation of resources should be done in such a way that it limits interference with other devices at the device and macro cell levels.
Direct D2D communication with device-controlled link formation (Gupta and Jha, 2015) 
Security and privacy must be maintained when routing data via another user's device. With closed access, a device maintains a list of reliable / trusted devices (e.g., devices from your office, devices that have been certified by a third party), which it can communicate with at the device level. Otherwise, communications are done at the macro cell level. With open access, a device can act as a relay for other devices without any restrictions.
When devices communicate via the BS, the BS handles the resource allocation and call set up — this centralised approach eases interference management. With D2D communications, resource allocation between devices are not supervised by a centralised entity (BS). Resource allocation at the device level might affect macro cell users because they are working in the same licensed band. Therefore, a dualistic network has to be considered, which involves different interference management and resource allocation schemes. Among the schemes used are resource pooling, non-cooperative game (or bargaining game), admission control and power allocation, cluster partitioning and relay selection.
Source
- A. Gupta and R.K. Jha, "A Survey of 5G Network: Architecture and Emerging Technologies", IEEE Access, Volume 3, 2015
- M.N. Tehrani, M. Uysal, H. Yanikomeroglu, "Device-to-Device Communication in 5G Cellular Networks: Challenges, Solutions and Future Directions", IEEE Communications Magazine, Volume: 52, Issue 5, 2014
No comments:
Post a Comment