PhD Student, Monash University


Telecommunication becomes an essential part of our life, which without it we can not live anymore since all of our daily lives is strictly depended on it. Can you assume a day without active telecommunication systems, i.e., no phone, no tv, no internet, no GPS, no reliable travel, and etc? Moreover, the quality of a reliable, fast and global telecommunication is a goal, which scientist currently working on it and as you can see around yourself, we have a huge progress in these terms compared to a couple of years ago. However, we need more reliable, green and faster telecommunication, as today society is participating actively in the network, and demand for sending and receiving data is higher than ever and even would be higher than now, so we have to find solutions to increase the data rate.

When you use your mobile phone, it seems that you can actually speak and listen simultaneously, which is not what is really happening. In reality, you can suppose that you have two Walkie-talkies in your hand, which using one you can speak and by using another you can listen to the other side of the line. Each Walkie-talkie represents a half-duplex link, which by using two of them, somehow you can have an artificial full-duplex link, i.e., speak and listen simultaneously.

With progress in telecommunication technology, now we are going to have the genuine full-duplex technology. By having a genuine full-duplex network, the speed of communication becomes almost double, which is a huge progress in the telecommunication industry. However, Having a full-duplex link has its own challenges, which the most dominant one is self-interference. Since we speak and listen into one link at the same time, it causes our speak leaking into listening port. Note that conventional artificial full-duplex technology uses two different half-duplex links to avoid this self-interference, i.e., twice resources, twice price, and everything become twice, which with genuine full-duplex we cut them all off to one link and the price will become half. On the other hand, with the same cost and resource, we can get double speed.

Finally, in order to be able to benefit from this technology one needs to cope with this self-interference, which we have stepped in, and proposed an adaptive scheduling algorithm which can take care of this self-interference and able us to use this full-duplex technology and benefit from a huge speed increase in telecommunication systems.


Interference Exploitation in Full Duplex Communications: Trading Interference Power for Both Uplink and Downlink Power Savings

Abstract: This paper considers a multiuser full-duplex (FD) wireless communication system, where a FD radio base station (BS) serves multiple single-antenna half-duplex (HD) uplink and downlink users simultaneously. Unlike conventional interference mitigation approaches, we propose to use the knowledge of the data symbols and the channel state information (CSI) at the FD radio BS to exploit the multi-user interference constructively rather than to suppress it. We propose a multi-objective optimisation problem (MOOP) via the weighted Tchebycheff method to study the trade-off between the two desirable system design objectives namely the total downlink transmit power minimisation and the total uplink transmit power minimisation problems at the same time ensuring the required quality-of-service (QoS) for all users. In the proposed MOOP, we adapt the QoS constraints for the downlink users to accommodate constructive interference (CI) for both generic phase shift keying (PSK) modulated signals as well as for quadrature amplitude modulated (QAM) signals. We also extended our work to a robust design to study the system with imperfect uplink, downlink and self-interference CSI. Simulation results and analysis show that, significant power savings can be obtained. More importantly, however, the MOOP approach here allows for the power saved to be traded off for both uplink and downlink power savings, leading to an overall energy efficiency improvement in the wireless link.

Pub.: 30 Mar '17, Pinned: 25 Aug '17

Optimal Power Allocation for a Full-Duplex Multicarrier Decode-Forward Relay System with or without Direct Link

Abstract: This paper addresses power allocation problems for a dual-hop full-duplex multicarrier decode-forward relay system with or without a direct link from the source to the destination. The full-duplex relay has a residual self-interference proportional to its transmitted power. We consider two schemes of decode-forward at the relay: carrier-wise decode-forward (CDF) and group-wise decode-forward (GDF). For the CDF scheme, we consider problems of optimal power allocation subject to system-wise total power constraint, node-wise individual power constraint and system-wise rate constraint, respectively. All these problems are shown to be equivalent to convex problems, and fast algorithms for finding the exact solutions are developed. For the GDF scheme, we focus on the case of node-wise individual power constraint. This problem is non-convex for which we develop fast algorithms for finding locally optimal solutions. Using the algorithms developed in this paper, we are able to show that the system capacity with optimal power allocation based on either CDF or GDF is higher than that of the half-duplex relay (HDR) system at power levels where HDR outperforms the direct transmission via the direct link. Furthermore, the system capacity based on GDF is consistently higher than that of HDR for all power levels while both have the same degree of freedom. This paper also shows new insights of algorithmic development, which should be useful for other related problems.

Pub.: 07 Feb '17, Pinned: 25 Aug '17

Resource Optimization and Power Allocation in In-band Full Duplex (IBFD)-Enabled Non-Orthogonal Multiple Access Networks

Abstract: In this paper, the problem of uplink (UL) and downlink (DL) resource optimization, mode selection and power allocation is studied for wireless cellular networks under the assumption of in-band full duplex (IBFD) base stations, non-orthogonal multiple access (NOMA) operation, and queue stability constraints. The problem is formulated as a network utility maximization problem for which a Lyapunov framework is used to decompose it into two disjoint subproblems of auxiliary variable selection and rate maximization. The latter is further decoupled into a user association and mode selection (UAMS) problem and a UL/DL power optimization (UDPO) problem that are solved concurrently. The UAMS problem is modeled as a many-to-one matching problem to associate users to small cell base stations (SBSs) and select transmission mode (half/full-duplex and orthogonal/non-orthogonal multiple access), and an algorithm is proposed to solve the problem converging to a pairwise stable matching. Subsequently, the UDPO problem is formulated as a sequence of convex problems and is solved using the concave-convex procedure. Simulation results demonstrate the effectiveness of the proposed scheme to allocate UL and DL power levels after dynamically selecting the operating mode and the served users, under different traffic intensity conditions, network density, and self-interference cancellation capability. The proposed scheme is shown to achieve up to 63% and 73% of gains in UL and DL packet throughput, and 21% and 17% in UL and DL cell edge throughput, respectively, compared to existing baseline schemes.

Pub.: 17 Jun '17, Pinned: 25 Aug '17

Optimal Power Allocation Strategies in Full-duplex Relay Networks

Abstract: In this work, we consider a dual-hop, decode-and-forward network where the relay can operate in full- duplex (FD) or half-duplex (HD) mode. We model the residual self-interference as an additive Gaussian noise with variance proportional to the relay transmit power, and we assume a Gaussian input distribution at the source. Unlike previous work, we assume that the source is only aware of the transmit power distribution adopted by the relay over a given time horizon, but not of the symbols that the relay is currently transmitting. This assumption better reflects the practical situation where the relay node also forwards signaling traffic, or data originated by other sources. Under these conditions, we identify the optimal power allocation strategy at the source and relay, which in some cases coincides with the half duplex transmission mode. In particular, we prove that such strategy implies either FD transmissions over an entire frame, or FD/HD transmissions over a variable fraction of the frame. We determine the optimal transmit power level at the source and relay for each frame, or fraction thereof. We compare the performance of the proposed scheme against reference FD and HD techniques, which assume that the source is aware of the symbols instantaneously transmitted by the relay. Our results highlight that our scheme closely approaches or outperforms such reference strategies.

Pub.: 04 Aug '17, Pinned: 25 Aug '17

Multicarrier Relay Selection for Full-Duplex Relay-Assisted OFDM D2D Systems

Abstract: In this paper, we propose a full-duplex orthogonal frequency-division multiplexing (OFDM) device-to-device (D2D) system in two-hop networks, where multiple full-duplex decode-and-forward (DF) relays assist the transmission from D2D user equipment (DUE) transmitter to DUE receiver. By such a transmission mechanism, the signal transmitted by the DUE transmitter does not need to go through a base station (BS). Meanwhile, due to the adoption of underlay D2D communication protocol, power control mechanisms are thereby necessary to be applied to mitigate the interference to conventional cellular communications. Based on these considerations, we analyze the outage performance of the proposed system, and derive the exact expressions of outage probabilities when bulk and per-subcarrier relay selection criteria are applied. Furthermore, closed-form expressions of outage probabilities are also obtained for special cases when the instantaneous channel state information (CSI) between BS and cellular user equipments (CUEs) is not accessible, so that a static power control mechanism is applied. Subsequently, we also investigate the outage performance optimization problem by coordinating transmit power among DUE transmitter and relays, and provide a suboptimal solution, which is capable of improving the outage performance. All analysis is substantiated by numerical results provided by Monte Carlo simulations. The analytical and numerical results demonstrated in this paper can provide an insight into the full-duplex relay-assisted OFDM D2D systems, and serve as a guideline for its implementation in next generation networks.

Pub.: 10 Aug '17, Pinned: 25 Aug '17