Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE credits
In current cellular networks the demand of traffic is rapidly increasing and new techniques need to be developed to accommodate future service requirements. Device-to-Device (D2D) communications is one technique that has been proposed to improve the performance of the system by allowing devices to communicate directly without routing traffic through the base station. This technique has the means to improved performance and support new proximity based services.
Nowadays new applications based on geographical proximity are becoming more and more popular suggesting that D2D communications will have a high de- mand in the near future. Thus the study of the scalability of D2D communications is of paramount importance.
We define the scalability of D2D communications underlay cellular networks as the maximum number of D2D links that can share the cellular resources while assuring QoS to both D2D links and cellular users.
In this thesis we study the scalability of D2D communication underlay cellu- lar networks in a multi-cell environment. We propose interference coordination schemes to maximize the number of D2D links while assuring QoS to D2D links and cellular users.
Three interference coordination schemes have been proposed considering dif- ferent levels of available channel state information (CSI). The first scheme is called no CSI centralized (N-CSIC) scheme and it is based on a centralized solution where no CSI is needed. The second is partial CSI distributed (P-CSID) scheme and it is based on a distributed solution where partial CSI is available. The last scheme is named full CSI optimal (F-CSIOp) scheme and it is achieved by formulating an optimization problem considering full CSI to be available.
Extensive mathematical and numerical analysis is conducted to develop and evaluate the proposed schemes. The results show that F-CSIOp scheme offers the best performance followed by the P-CSID and finally N-CSIC, thus a clear relationship is found between complexity and performance.
The P-CSID offers a practical solution for a low complexity interference co- ordination scheme that achieves good scalability and capacity for a wide range of strict QoS requirements. Moreover the results show that further improvement can be achieved if proper selection of the involved parameters is done along with the implementations of closed loop power control (CLPC) schemes.
The N-CSIC scheme provides a good solution for low SINR values of D2D links when the QoS of cellular users is low. Thus it is a good candidate for applications like sensor networks or M2M communications where the SINR requirements are rather low and there are no primary users to impose more interference constraints.
Finally we conclude that good scalability and capacity can be achieved with the proposed low complexity interference coordination schemes for D2D communications and provide interesting topics for future research.
2014. , 57 p.