In-band full-duplex (IBFD) backhauling is a potential technique for wireless backhauling of small cells that allows the use of same spectrum for the backhaul and access links of the small cell base stations (SBSs) concurrently, however, at the expense of backhaul interference and self-interference (SI). This paper investigates the problem of optimal access/backhaul spectrum allocation considering IBFD backhauling, out-of-band full-duplex (OBFD) backhauling (in which the access and backhaul transmissions take place on different spectrum), and the SBSs with the provisioning for hybrid IBFD/OBFD backhauling. We first formulate a problem to maximize the minimum achievable rate (i.e., minimum of the rates in the backhaul link and the access link) at the SBSs in a hybrid IBFD/OBFD setting. The solution of the centralized spectrum allocation problem, which serves as a benchmark for any sub-optimal solution, is provided by transforming the original problem into an epigraph form. As a special case of the formulated problem, we derive closed-form optimal solutions for the access/backhaul spectrum allocation of OBFD backhauling as well as IBFD backhauling. We then propose and comparatively analyze the performance of two distributed backhaul spectrum allocation schemes, namely, maximum received signal power (max-RSP) and minimum received signal power (min-RSP) schemes. For these schemes, we theoretically derive the number of allocated backhaul channels, minimum rate coverage probability, and average achievable rate of each SBS given its distance from the centralized wireless backhaul hub (WBH) for both IBFD and OBFD backhauling. Numerical results reveal that the optimal spectrum allocation rules can significantly vary for IBFD and OBFD backhauling. Optimal OBFD backhauling favors more backhaul spectrum for SBSs located far-away from the WBH. With IBFD backhauling, spectrum allocation for SBSs strongly depends on SI. With the reduction in SI, the optimal backhaul spectrum increases/decreases for nearby/farther SBSs. Simulation results comparing the optimal solution with the distributed spectrum allocation solutions based on max-RSP and min-RSP schemes are also presented.

Downlink Spectrum Allocation for In-Band and Out-Band Wireless Backhauling of Full-Duplex Small Cells

A node can provide a file to other nodes after downloading the file or data from the Internet. When more than one node have obtained the same file, this is considered a multisource transmission, in which all these nodes can act as candidate providers (sources) and transmit the file to a new request node (destination) together. In cases where there is negligible or no interference, multisource transmission can improve the download throughput because of parallel transmissions through multiple paths. However, this improvement is not guaranteed due to wireless interference among different paths. Wireless interference can be alleviated by the multiradio and multichannel technique. Because the source and multipath routing selections interact with channel assignment, the multisource transmission problem with multiradio and multichannel presents a significant challenge. In this paper, we propose a distributed joint source, routing, and channel selection scheme. The source selection issue can be concurrently solved via multipath finding. There are three sub-algorithms in our scheme, namely, interference-aware routing algorithm, channel assignment algorithm, and local routing adjustment algorithm. The interference-aware routing algorithm is used to find paths sequentially and is jointly executed with the channel assignment algorithm. After finding a new path, the local routing adjustment algorithm may be executed to locally adjust the selected paths so as to further reduce wireless interference. Extensive simulations have been conducted to demonstrate that our algorithms can effectively improve the network aggregate throughput, as well as reduce delay and packet loss probability.

Interference-Aware Multisource Transmission in Multiradio and Multichannel Wireless Network

This paper investigates a user-fairness relay selection (RS) problem for decode-and-forward (DF) full-duplex (FD) relay networks, where multiple users cooperate with multiple relays in each coherence time. We consider two residual self-interference (RSI) models with or without direct links. We propose a sub-optimal relay selection (SRS) scheme which requires only the instantaneous channel state information (CSI) of source-to-relay and relay-to-destination links. To evaluate the performance, the outage probability of SRS is derived for different scenarios depending on RSI models and the availability of direct links. To further investigate, asymptotic expressions are derived for the high-transmit power regime. For comparison purposes, 1) the average throughputs of the FD and half-duplex (HD) modes are derived; 2) non-orthogonal transmission is considered and its performance is discussed with approximations; and 3) the impact of imperfect CSI is investigated with the aid of analysis. While simulation results are provided to verify the analytical results, they reveal interesting fundamental trends. It turns out that a significant throughput degradation occurs with FD mode over HD mode when self-interference is fully proportional to the transmit power. Since all users can communicate in the same coherence time with the FD mode, these joint RS schemes are useful for user-fairness low-latency applications.

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Multi-User Relay Selection for Full-Duplex Radio

We propose a novel joint user and full-duplex (FD) relay selection (JUFDRS) scheme to enhance physical layer security in a multi-user multi-relay network. In this scheme, the user and the FD decode-and-forward relay are selected such that the capacity of the end-to-end user-relay-destination channel is maximized to ensure the highest quality of cooperative transmission. To fully examine the benefits of the JUFDRS scheme, we derive a new closed-form expression for the secrecy outage probability. We show that the JUFDRS scheme significantly outperforms the joint user and half-duplex relay selection (JUHDRS) scheme when the self-interference at the FD relay can be reasonably suppressed. This result indicates that adopting the FD technique at relays can effectively enhance the physical layer secrecy performance in the multi-user multi-relay network.

/pdf/physical-layer-security-enhancement-in-multi-user-multi-full-atapy272ln.pdf

Physical layer security enhancement in multi-user multi-full-duplex-relay networks

Abstract Helical polymers such as poly(phenylacetylene)s (PPAs) are interesting materials due to the possibility of tuning their helical scaffold (sense and elongation) once they have been prepared and by the presence of external stimuli. The main limitation in the application of PPAs is their poor photostability. These polymers degrade under visible light exposure through a photochemical electrocyclization process. In this work, it was demonstrated, through a selected example, how the photochemical degradation in PPAs is directly related to their dynamic helical behavior. Thus, while PPAs with dynamic helical structures show poor photostability under UV/Vis light exposure, poly‐(R)‐1, bearing an enantiopure sulfoxide group as pendant group and designed to have a quasi‐static helical behavior, shows a large photostability due to the restricted conformational composition at the polyene backbone, needed to orient the conjugated double bonds prior to the photochemical electrocyclization process and the subsequent degradation of the material.

/pdf/photostability-and-dynamic-helical-behavior-in-chiral-poly-2tpcibpi.pdf

Photostability and Dynamic Helical Behavior in Chiral Poly(phenylacetylene)s with a Preferred Screw‐Sense

We investigate the outage probability of a variablegain amplify-and-forward (AF) relay network. A multi-source multi-relay network is considered with one destination and twoway traffic, where each node is equipped with two antennas and works on a full-duplex (FD) transmission mode. Meanwhile, the number of sources and relays is M and N, respectively. The residual self-interference, leaking from the full-duplex node's output to its input, exists in each node, and selective combing is performed at the source and the destination. In particular, we propose a practical joint source-relay selection scheme for this network, aiming to harvest selective diversity and power gain for reliable transmission. Unlike the existing schemes, we take the direct link from the source to the destination into consideration; therefore, it bears the potential to improve system stability. The proposed scheme only needs the local channel state information (CSI), and can be operated in a distributed manner. Furthermore, we derive a tight closed-form lower bound for the outage probability with the proposed scheme, and a simple asymptotic expression is also obtained with clear insights into the achievable diversity order. Our analysis shows that full cooperative diversity gain is achievable with the proposed scheme, and the selection on sources provides additional power gain. Finally, numerical results consolidate our theoretical analysis and show the effectiveness of the proposed scheme.

Joint source-relay selection in two-way full-duplex relay network

Novel highly efficient absolute optical resolution method by serial combination of two asymmetric reactions from acetylene monomers having racemic substituents.

The invention relates to joint destination relay selection and antenna selection in a full duplex relay network. In the relay network, the united destination node, relay node and relay antenna selection operation steps are as follows that (1), a source node SN calculates signal-to-noise ratio SNRs of direct transmission links from the SN to destination node DNs and selects the optimum DN according to the SNRs; and (2), two antennas exist at each RN, each antenna can work in a sending or receiving mode, the optimum DN feeds back channel state information from two antennas at each relay node to the optimum destination node to the RN, each RN obtains the channel state information from the SN to each antenna of the relay node, and on the basis of the received CSI, each RN calculates a signal-to-interference-plus-noise ratio SINR of a relay link when the two antennas of the relay node work in the sending/receiving or receiving/sending mode and selects the sending/receiving mode of the relay antenna according to the SINR of the relay link. According to the joint destination relay selection and antenna selection, the partial CSI is utilized, the system complexity is reduced, the optimum DN, the optimum RN and the antenna working mode are selected, and the system performance is improved.

Yanan Tang

Papers

Joint source-relay selection in two-way full-duplex relay network

Novel highly efficient absolute optical resolution method by serial combination of two asymmetric reactions from acetylene monomers having racemic substituents.

Joint Destination-Relay Selection and Antenna Mode Selection in Full-Duplex Relay Network