While this may seem like a downer, remember that you should have passion for the research you work on (most of the time), so you should be excited to think up new experiments or different ways to consider that data you have collected. Even when I'm lying in bed about to fall asleep, I am sometimes ruminating about aspects of my experiment I could modify or what information I could do a literature search on to gain new insights. A PhD program is quite the commitment and rarely lives up to expectations – but it is well worth the time and effort you will spend for something that truly excites you.
Advanced Single-Carrier and Multi-Carrier OFDM transceivers (Transmission protocols, Frequency Diversity, Optimal selection of OFDM parameters, OFDM-based multiple access schemes). Advanced Multiple-Antenna Techniques (Diversity-Multiplexing Tradeoff, Hybrid MIMO systems, MIMO-OFDM). Relaying and Cooperative Communications (Types of relaying, architectures, performance). Spectrum Management (Cognitive Networks, Sensing and Allocation Algorithms, Carrier Aggregation). LTE-Advanced (Evolution from 3G to 4G and beyond, Targets and IMT-Advanced Requirements, LTE Radio Access, Supported Transmission Modes). Towards 5G (HetNets, Small-cells). Wi-Fi ( family of standards, Super G Technology). Wired Standards (ADSL-VDSL). Satellite communication standards (DVB-S2, DVB-S2X extension, Hybrid terrestrial/satellite networks and applications).