1. 1. By Bekir Kendirci Supervised By Dr. H. Zhu Device-to-Device(D2D) Communications in Cellular Networks
2. 2. CONTENT OVERVIEW OF DEVICE-TO-DEVICE A.INTRODUCTION B.ADVANTAGES C.CHALLENGES OBJECTIVES OF PROJECT TECHNICAL ISSUES SCENARIO SIMULATION and RESULTS FURTHER WORKS
3. 3. OVERVIEW OF DEVICE-TO-DEVICE A.INTRODUCTION Device to device (D2D) communications are when two user equipments are close enough to each other, the devices may communicate directly or via base station assistance. D2D technology enables a direct link (uplink or downlink resources) between user equipments (UEs) without help of base station.
4. 4. B.ADVANTAGES Efficient and improved performance for UEs such as battery life, energy consumption. Lower latency can be achieved. Higher data rates can be achieved. D2D communication provides offloading in cellular networks so workload of the base stations are reduced thus network can be used more effectively. D2D can increase resource utilization and also extend coverage of cellular network.
5. 5. C.CHALLENGES Interference management for communication network. Radio resource allocation and resource management. Mode of D2D ; licensed or unlicensed and network assisted or unassisted Distance between UEs, distance between base station and D2D pairs. Choosing frequency resource for direct link of D2D pair (uplink or downlink).
6. 6. OBJECTIVES OF PROJECT Measuring efficiency of D2D performance. D2D performance without and with interferences from each other and base station. Radio resource management: comparison of dowlink and uplink resources for D2D direct link. Frequency reuse for D2D pairs in the cell by diving cell into sectors.
7. 7. TECHNICAL ISSUES Orthoganal Freqeuncy Division Muliplex (OFDM) with 256-fft is used . Quadrature Amplitude Modulation(QAM) with 4,16 and 64 modulation orders. Fading Rayleigh is used as channel One cell scenario with D2D pairs, base station and cellular user. Interference from D2D pairs, base station and cellular user. Downlink and uplink frequency resources. Sample time is 5.21 us.
8. 8. SCENARIO D2D pair 1 D2D pair 4 CEU1 CEU2 CEU3 Interference : Signal : Interference from BS : Interference from CUE: D2D communication scenario in a cell for downlik or uplink resources.
9. 9. SIMULATIONS AND RESULTS
10. 10. TRANSMITTER OF D2D
11. 11. RECEIVER OF D2D
12. 12. CHANNEL Multipath Rayleigh Fading and Additive White Gaussian Noise affect the system. Approximately no doppler shift Channel effect is normalized by dividing it with complex gain magnitude of Rayleigh channel.
13. 13. RESULTS
14. 14. FURTHER WORKS D2D communication can be examined by more cell scenarios. D2D devices can be combined with difference technologies such as MIMO. More realistic number of users and scenarios can be built. Different enviroments can be examined instead of using Rayleigh Channel, for example Nakagami Channel can be used Adaptive modulation techniques can be added to model.