Wonjae Shin

Non-orthogonal multiple access (NOMA) is a potential enabler for the development of 5G and beyond wireless networks. By allowing multiple users to share the same time and frequency, NOMA can scale up the number of served users, increase spectral efficiency, and improve user-fairness compared to existing orthogonal multiple access (OMA) techniques. While single-cell NOMA has drawn significant attention recently, much less attention has been given to multi-cell NOMA. This article discusses the opp

In this letter, two novel coordinated beamforming techniques are developed to enhance the performance of non-orthogonal multiple access combined with multiple-input multiple-output communication in the presence of inter-cell interference. The proposed schemes successfully deal with inter-cell interference, and increase the cell-edge users' throughput, which in turn improves user fairness. In addition, they increase the number of served users, which makes them suitable for 5G networks where massi

The interference alignment (IA) is a promising technique to effectively mitigate interferences in wireless communication systems. To show the potential benefits of such an IA scheme, this letter focuses on a two-cell multiple-input multiple-output (MIMO) Gaussian interfering broadcast channels (MIMO-IFBC) with M transmit antennas and N receive antennas. It corresponds to a downlink scenario for cellular networks with two base stations (BSs) with M transmit antennas per BS, and two users with N r

This paper focuses on interference issues arising in the downlink of a heterogeneous network (HetNet), where small cells are deployed within a macrocell. Interference scenario in a HetNet varies based on the type of small cell access modes, which can be classified as either closed subscriber group (CSG) or open subscriber group (OSG) modes. For these two types of modes, we propose hierarchical interference alignment (HIA) schemes, which successively determine beamforming matrices for small cell

A two-way relaying system using the physical-layer network coding (PNC) does not cause the spectral loss induced by the half-duplex signaling. Furthermore, when the total power, which is limited, is properly distributed to transmission nodes in such a system, the system capacity will be enhanced significantly. In this paper, we propose an optimal power allocation in the two- way relay channel employing the PNC protocol. The optimal power allocation is obtained by maximizing the achievable sum- r

A new relay-aided non-orthogonal multiple access (NOMA) technique is proposed for multi-cell uplink cellular networks in which each cell supports K single-antenna users by its respective base station (BS) equipped with N(4Z ≪K) antennas. Cooperative relaying transmission is used to accommodate more than one user per orthogonal resource block in the context of interference-limited cellular networks. With the proposed relayaided NOMA, an Alamouti structure of the desired symbol can further be gene

Near maximum-likelihood(ML) detections with reduced complexity are promising techniques for coded multiple- input multiple-output (MIMO) systems. Particularly, the QRM- MLD algorithm is often considered in practical applications since it can easily control receiver's complexity. However, it provides inaccurate log likelihood ratio (LLR) values due to the limited number of candidate symbol vectors. To overcome the problem, this paper presents an efficient LLR computation algorithm. The proposed a

A cooperative wireless-powered communication network protocol is proposed, in which user far away from a hybrid access point (H-AP) is capable of harvesting wireless powers by overhearing the uplink signals of users that are relatively nearer to the H-AP, in addition to downlink signal broadcast by the H-AP. In this setting, time allocations for the downlink transmission of the H-AP and the uplink transmission for the users are jointly optimized for two different purposes. First, the weighted su

Non-orthogonal multiple access (NOMA) is a potential enabler for the development of 5G and beyond wireless networks. By allowing multiple users to share the same time and frequency, NOMA can scale up the number of served users, increase the spectral efficiency, and improve user-fairness compared to existing orthogonal multiple access (OMA) techniques. While single-cell NOMA has drawn significant attention recently, much less attention has been given to multi-cell NOMA. This article discusses the

In this paper, we investigate an interference management scheme relying on multiple antennas in heterogeneous networks with a mixed macro and pico deployment. Our main contribution is to propose a new interference alignment scheme for the heterogenous network. Specifically, our scheme successively creates transmit beamforming vectors for the pico base stations (BSs) and for the macro base station (BS) using the fact that the macro BS and pico BSs have different number of transmit antennas and di

Envisioned to be a component of 5G cellular networks, non-orthogonal multiple access (NOMA) can accommodate more users and has superior spectral efficiency compared to the conventional orthogonal multiple access schemes. NOMA, however, intensifies inter-cell interference since its power allocation strategy is biased toward cell-edge users. To deal with this problem in a multi-cell multiple-input multiple-output (MIMO) communication network, a new interfering channel alignment based NOMA techniqu

In this paper, we propose a new retrospective interference alignment for two-cell multiple-input multiple-output (MIMO) interfering multiple access channels (IMAC) with M receive antennas per base station (BS) and K users per cell each with N transmit antennas. The key idea of the retrospective IA lies in interference-purification during phase 1 and 2, and interference-repetition during phase 3. On the basis of the proposed method, we show that the achievable sum degrees of freedom (sum-DoF) is

This paper studies full-duplex (FD) cellular networks in which a base station (BS) operated in FD mode with multiple antennas supports multiple uplink and downlink users simultaneously in the same wireless channel. Two typical FD cellular scenarios are considered, one with half-duplex (HD) users and the other with FD users along with the FD BS. For both the cases, a novel constructive method is developed for finding a closed-form interference alignment (IA) solution, named <italic xmlns:mml="htt

This paper proposes a novel relay-aided successive aligned interference cancellation (RaSAIC) method for a 2 × K X channel with L full-duplex relays, each of which is fully connected to the channel. The core idea of the RaSAIC is to apply a cooperative relays' precoding technique that aligns interference signals at unintended receivers while creating an Alamouti structure for the desired signals. With the proposed cooperative relay transmission technique, it is shown that both the optimal sum de

Abstract To enable accurate and reliable indoor localization in a multi‐building environment, a novel constrained convolutional neural network (CNN)‐based indoor localization system (C‐CNNLoc) is proposed using WiFi fingerprinting approach. The proposed network has a sequential structure that firstly classifies a building, followed by estimating the user's location coordinate within the pre‐detected building. Furthermore, the location accuracy is improved by introducing a new loss function that