Achievable Sum Rates of Half- and Full-Duplex Bidirectional OFDM Communication Links

While full-duplex (FD) transmission has the potential to double the system capacity, its substantial benefit can be offset by the self-interference (SI) and non-ideality of practical transceivers. In this paper, we investigate the achievable sum rates (ASRs) of half-duplex (HD) and FD transmissions with orthogonal frequency division multiplexing (OFDM), where the non-ideality is taken into consideration. Four transmission strategies are considered, namely HD with uniform power allocation (UPA), HD with non-UPA (NUPA), FD with UPA, and FD with NUPA. For each of the four transmission strategies, an optimization problem is formulated to maximize its ASR, and a (suboptimal/optimal) solution with low complexity is accordingly derived. Performance evaluations and comparisons are conducted for three typical channels, namely symmetric frequency-flat/selective and asymmetric frequency-selective channels. Results show that the proposed solutions for both HD and FD transmissions can achieve near optimal performances. For FD transmissions, the optimal solution can be obtained under typical conditions. In addition, several observations are made on the ASR performances of HD and FD transmissions.Comment: To appear in IEEE TVT. This paper solves the problem of sum achievable rate optimization of bidirectional FD OFDM link, where joint time and power allocation is involve

Full-Duplex Operations in Wireless Powered Communication Networks

In this paper, a wireless powered communication network (WPCN) consisting of a hybrid access point (H-AP) and multiple user equipment (UEs), all of which operate in full-duplex (FD), is described. We first propose a transceiver structure that enables FD operation of each UE to simultaneously receive energy in the downlink (DL) and transmit information in the uplink (UL). We then provide an energy usage model in the proposed UE transceiver that accounts for the energy leakage from the transmit chain to the receive chain. It is shown that the throughput of an FD WPCN using the proposed FD UEs can be maximized by optimally allocating the UL transmission time to the UEs by solving a convex optimization problem. Simulation results reveal that the use of the proposed FD UEs efficiently improves the throughput of a WPCN with practical self-interference cancellation (SIC) capability at the H-AP. With current SIC technologies reducing the power of the residual self-interference to the level of background noise, the proposed FD WPCN using FD UEs achieves 18% and 25 % of throughput gain as compared to the conventional FD WPCN using HD UEs and HD WPCN, respectively.Comment: 7 pages, 7 figure

Auditory Processing in Children with Specific Language Impairments: Are there Deficits in Frequency Discrimination, Temporal Auditory Processing or General Auditory Processing?

Background/Aims: Specific language impairment (SLI) is believed to be associated with nonverbal auditory (NVA) deficits. It remains unclear, however, whether children with SLI show deficits in auditory time processing, time processing in general, frequency discrimination (FD), or NVA processing in general. Patients and Methods: Twenty-seven children (aged 8-11) with SLI and 27 control children (CG), matched for age and gender, were retrospectively compared with regard to their performance on five NVA skills in terms of just noticeable differences (JND) and time order judgments (TOJ). JND was used for FD, intensity discrimination, and gap detection, while TOJ was used for FD and clicks. Results: Children with SLI performed significantly worse than the CG only on the FD tasks (JND and TOJ). The other nonverbal tasks showed no significant intergroup differences. Additionally, moderate associations were found between the FD tasks and phonological skills, as well as between FD tasks and language scores. Conclusion: Children with SLI appear to have restricted FD skills compared to controls, but there was no evidence for a common NVA deficit or reduced temporal auditory abilities. Copyright (C) 2009 S. Karger AG, Base

The response of two legume crops (hyacinth bean and Kidney bean) to the parasitism of field dodder (_Cuscuta campestris_)

Abstract: Microscopic examinations and chemical studies were performed to study the response of two legume crops, hyacinth bean (_Lablab purpureus L._) Sweet and kidney bean (_phaseolus vulgaris L._) to the filed dodder (FD) (_Cuscuta campestris Yuncker_) parasitism. Hyacinth bean, showing no effective resistance mechanisms,was found to be a highly susceptible host to FD. However, kidney bean, displaying resistant reactions towards the parasitism of FD,was found to be an incompatible host.The possible reasons for the resistance of kidney bean to FD were anatomical (hypersensitivity) and chemical (high contents of phenolic acids and lignin) stimulated defence mechanisms, which developed during the actual intrusion of FD haustorial cells inside its tissues

On the use of semi-distributed and fully-distributed urban stormwater models

Urban stormwater models comprise four main components: rainfall, rainfall-runoff, overland flow and sewer flow modules. They can be considered semi-distributed (SD) or fully distributed (FD) according to the rainfall-runoff module definition. SD models are based on sub-catchments units through which rainfall is applied to the model and at which runoff volumes are estimated. In FD models, the runoff volumes are estimated and applied directly on every element of a twodimensional (2D) model of the surface. This poster presents a comparison of SD and FD models based on two case studies: Zona Central catchment at Coimbra, Portugal, and Cranbrook catchment at London, UK. SD and FD modelling results are compared against water depth and flow records in sewers, and photographic records of a flood event. In general, FD models are theoretically more realistic and physically-based, but the results of this study suggest that the implementation of these models requires higher resolution (more detailed) elevation, land use and sewer network data than is normally used in the implementation of SD models. Failing to use higher resolution data for the implementation of FD models could result in poor-performing models. In cases when high resolution data are not available, the use of SD models could be a better choice

Passive Loop Interference Suppression in Large-Scale Full-Duplex Cellular Networks

Loop interference (LI) in wireless communications, is a notion resulting from the full-duplex (FD) operation. In a large-scale network, FD also increases the multiuser interference due to the large number of active wireless links that exist. Hence, in order to realize the FD potentials, this interference needs to be restricted. This paper presents a stochastic geometry model of FD cellular networks where the users and base stations employ directional antennas. Based on previous experimental results, we model the passive suppression of the LI at each FD terminal as a function of the angle between the two antennas and show the significant gains that can be achieved by this method. Together with the reduction of multiuser interference resulting from antenna directionality, our model demonstrates that FD can potentially be implemented in large-scale directional networks.Comment: to appear in Proc. IEEE SPAWC 201