PhD Defense: “Coding Schemes for Energy Harvesting and Multi-User Communications,” Mehdi Dabirnia (EE), EE-314, 9AM December 18 (EN)

SEMINAR: “Coding Schemes for Energy Harvesting and Multi-User Communications”
Ph.D. Defence in Electrical and Electronics Engineering

The seminar will be on Monday, December 18, 2017 at 09:00, @EE-314

Many wireless communication and networking applications can benefit from energy harvesting and wireless energy transfer including wireless sensor networks, radio frequency identification systems and wireless body networks. Some of the advantages that energy harvesting provides for such applications include energy self-sufficiency, ability to implement them in hard-to-reach places, reducing the required battery size or even removing the battery completely from the wireless units. In such systems the required energy for the system operation is obtained from a renewable energy source such as solar, thermal or kinetic energy or from a man-made source such as radio frequency (RF) signals, artificial light, etc. While there has been decades of designs and developments of energy harvesting nodes from circuit and device engineering perspectives, only recent studies consider the specific constraints of these systems from a communications perspective, and significant challenges and problems still remain unsolved, particularly, at the physical layer.

With the motivation of addressing some of the above challenges, our main focus in this thesis is the design and analysis of capacity approaching coding schemes for several energy harvesting and multiuser scenarios; in particular, by exploiting nonlinear codes concatenated with low-density parity-check (LDPC) codes for these scenarios. First, novel code design approaches are studied for the joint energy and information transfer specifically, employment of nonlinear trellis codes (NLTCs) in serial concatenation with outer LDPC codes is proposed, and an algorithm is developed to design the NLTCs prior to optimizing the outer LDPC code using the EXIT analysis. The designed codes are shown to improve upon the off-the-shelf point-to-point (P2P) codes and outperform the alternative of utilizing linear codes with time switching and the reference scheme of concatenating LDPC codes with nonlinear memoryless mappers (NLMMs). This coding approach is then examined for the energy harvesting channel (EHC) implementing two decoding approaches at the receiver side wherein the first one ignores the memory in the battery state, while the second one incorporates this memory into the trellis. Compared with the P2P codes and the reference schemes, the newly designed codes consistently offer better performance. This code design approach is explored for the case of discrete memoryless interference channels (DMICs) implementing the Han-Kobayashi (HK) encoding and decoding strategy as well. A stability condition is derived for the concatenated coding scheme and it is utilized in the process of designing the outer LDPC code employing the EXIT analysis. It is demonstrated that the designed codes achieve rate pairs close to the optimal boundary of the HK subregion and outperform the single user codes with time sharing. Furthermore, code design principles are also investigated for the two-user Gaussian interference channel with fading employing trellis-based codes with short block lengths. Finally, the problem of designing explicit and implementable codes is studied for a two-user interference channel with energy harvesting transmitters, and a design framework is proposed employing similar techniques developed for the DMIC and EHC.