In-band Emission Interference in D2D-enabled Cellular Network: Modelling, Analysis, and Mitigation

Device to device (D2D) links density is expected to increase dramatically in future networks. The D2D user equipments (DUEs) reuse frequency resources to cover the next generation D2D-enabled cellular network requirements. The cellular user equipments (CUEs) and DUEs experience in-band emission interference (IEI) from DUEs that use adjacent frequencies.

In this thesis, the IEI impact in D2D-enabled cellular network is investigated comprehensively. In the first part, the IEI from the DUEs to cellular links is initially mitigated for all time slots. An open loop power control (OLPC)-based scheme is introduced for the D2D discovery scenario to mitigate the IEI and compared with recent proposed methods. The scheme defines time slots to boost the DUEs transmission power, where the IEI is mitigated and the D2D link performance is improved. A simulation system is used to evaluate the IEI impact. The IEI from DUEs to cellular links is mitigated without taking into account the proposed power control can affect the DUEs that use the same frequency resource and the constraints can affect the D2D link performance.

Therefore, the second part expands the IEI investigation, where the D2D-enabled cellular network is modelled by taking into account the IEI interferers using the stochastic geometry tool. The IEI impact is analysed and mitigated for all time slots by taking into account the D2D links performance. The IEI impact is evaluated theoretically in terms of coverage probability and data rate for cellular link side, successful probability and data rate for D2D link side. The IEI intra-cell and IEI inter-cell are investigated separately to detect the dominant part of IEI. The expected reuse factor of the D2D resource blocks (DRBs) is derived to examing the number of DUEs that can be served when the IEI is or is not taken into account.

Following, a power-density based (PDB) strategy is proposed to mitigate the IEI by controlling the number of DUEs that use each DRB, and by allocating predefined DRBs to the DUEs that cause lowest interference power at the serving BS. The thinning process and Poisson hole process (PHP) are employed to remodel the network. The performance improvement can be achieved by employing this strategy is evaluated. The optimal DRBs setting is found that mitigates the IEI and improves the cellular link performance. Furthermore, the optimal power allocation (OPA) algorithm is proposed to mitigate the IEI by calculating the optimal DUEs transmission power profile that maximizes the DUEs sum rate and maintains the interference level at the BS below a predefined threshold. The performance improvement that can be achieved by employing this algorithm is also evaluated.

It is concluded that, in a D2D-enabled cellular network, the IEI impact is significant and needs to be considered to evaluate the performance of the future network accurately. Thus, the proposed model can be used to represent and evaluate the future network. Also, by employing the PDB strategy, the IEI can be mitigated effectively if the D2D links performance has higher priority than the number of DUEs required to be served for D2D discovery and transmission data scenarios. In case the required number of served DUEs in one time slot cannot be covered by PDB, the OPA algorithm and the OLPC-based strategy can be used for D2D data transmission and D2D discovery scenarios, respectively.