Browsing by Subject "Interference channel"

Now showing 1 - 3 of 3

Open Access
Coding schemes for energy harvesting and multi-user communications
(2017-12) Dabirnia, Mehdi
Many wireless communication and networking applications can bene t from energy harvesting and wireless energy transfer including wireless sensor networks, radio frequency identi cation systems and wireless body networks. Some of the advantages that energy harvesting provides for such applications include energy self-su ciency, 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, arti cial 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 speci c constraints of these systems from a communications point of view, and signi cant 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 speci cally, 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 o -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 rst 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 o er 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.
Open Access
Secrecy capacity results for a secure NOMA-based cognitive radio network with an external eavesdropper
(Elsevier, 2020) Mehr, K. Adli; Niya, J. M.; Seyedarabi, H.; Nobar, S. K.
In this paper, we investigate a secure cognitive radio network (CRN), which deploys non-orthogonal multiple access (NOMA) to deliver a mixed multicast and unicast traffic to the intended receivers, while keeping them secret from the eavesdroppers. This model represents a cognitive interference channel with an external eavesdropper (CIC-EE). In this model, there are one pair of primary nodes, one pair of secondary nodes, and an external eavesdropper. The primary transmitter multicasts a confidential message to both primary and secondary receivers, while trying to keep it secret from the eavesdropper. The secondary transmitter helps the primary user to deliver its message in exchange of transmission opportunity. The secondary message is unicasted to the secondary receiver, while concealing it from both primary receiver and the eavesdropper. This scenario models a NOMA-based overlay cognitive radio paradigm with an external eavesdropper. For this scenario, the achievable rate-equivocation region is obtained and its optimality is shown for a class of degraded channels. Then, the results obtained for the discrete memoryless channel are extended to the Gaussian channel model. Furthermore, by deploying numerical examples, a comparison is made between the proposed secure NOMA-based scheme, its orthogonal multiple access (OMA) based counterpart, and a cognitive interference channel without an external eavesdropper. It is shown that the NOMA-based method achieves significantly higher rates than its OMA based counterpart.
Open Access
Short block length code design for interference channels
(IEEE, 2016) Sharifi, S.; Dabirnia, Mehdi; Tanç, A. K.; Duman, Tolga M.
We focus on short block length code design for Gaussian interference channels (GICs) using trellis-based codes. We employ two different decoding techniques at the receiver side, namely, joint maximum likelihood (JML) decoding and single user (SU) minimum distance decoding. For different interference levels (strong and weak) and decoding strategies, we derive error-rate bounds to evaluate the code performance. We utilize the derived bounds in code design and provide several numerical examples for both strong and weak interference cases. We show that under the JML decoding, the newly designed codes offer significant improvements over the alternatives of optimal point-to-point (P2P) trellis-based codes and off-the-shelf low density parity check (LDPC) codes with the same block lengths.