This document discusses device-to-device (D2D) communications in cellular networks. It provides an introduction to D2D, outlines the advantages such as improved efficiency and performance, and challenges including interference management. The objectives of the project are to measure D2D performance with and without interference and compare using uplink and downlink resources. The document describes the simulation scenario and setup, which uses OFDM and Rayleigh fading. Results are presented and further work is proposed to expand the analysis to more complex scenarios.

1. By
Bekir Kendirci
Supervised By
Dr. H. Zhu
Device-to-Device(D2D)
Communications in Cellular
Networks

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. 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. 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. 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).

7. 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.

8. 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.

9. 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.

10. SIMULATIONS AND RESULTS

11. TRANSMITTER OF D2D

12. RECEIVER OF D2D

13. 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.

14. RESULTS

22. 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.