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Background Bamboo is a very important forest resource. However, the prolonged vegetative stages and uncertainty of flowering brings difficulties in bamboo flowers sampling. Until now, the flowering mechanism of bamboo is still unclear. Results In this study, three successive stages of flowering buds and the corresponding vegetative buds (non-flowering stage) from Lei bamboo (Phyllostachys violascens) were collected for transcriptome analysis using Illumina RNA-Seq method. We generated about 442 million clean reads from the above samples, and 132,678 unigenes were acquired with N50 of 1080 bp. A total of 7266 differentially expressed genes (DEGs) were determined. According to expression profile and gene function analysis, some environmental stress responsive and plant hormone-related DEGs were highly expressed in the inflorescence meristem formation stage (TF_1) while some floral organ development related genes were up-regulated significantly in floral organs determination stage (TF_2) and floral organs maturation (TF_3) stage, implying the essential roles of these DEGs in flower induction and maturation of Lei bamboo. Additionally, a total of 25 MADS-box unigenes were identified. Based on the expression profile, B, C/D and E clade genes were more related to floral organs development compared with A clade genes in Lei bamboo. Conclusions This transcriptome data presents fundamental information about the genes and pathways involved in flower induction and development of Lei bamboo. Moreover, a critical sampling method is provided which could be benefit for bamboo flowering mechanism study.

In this paper, we propose a novel dynamic manager selection scheme for vehicles platooning systems and investigate the corresponding resource allocation in the finite blocklength regime, to meet the ultra-reliable and low-latency communication (URLLC) requirements of safety-related data. To the best of our knowledge, this is the first work to investigate the impact of finite blocklength on communications of vehicles platooning systems. By taking into account the factors of communication and the changes in the platoon structure, the proposed dynamic platoon manager selection scheme enables a significant performance enhancement over the conventional fixed manager scheme where the head vehicle in the platoon acts as a manager. Based on the proposed platoon manager selection scheme, a joint resource allocation and coding rate optimization algorithm is proposed to minimize the intra-platoon groupcast latency. Thanks to the closed-form expression of the optimal coding rate and transmission power derived, the proposed optimization algorithm achieves optimal performance in terms of the intra-platoon groupcast latency and converges within only 3 iterations, with a significant complexity reduction over exhaustive search.

We propose an unmanned aerial vehicle (UAV) ground base station (GBS) coordinated NOMA scheme where UAV and GBS jointly serve the cell-edge users. To the best of our knowledge, this is the first work to investigate air-ground BSs coordination for UAV-assisted NOMA systems, by taking advantage of the interference between UAV and GBS. Therefore, the proposed UAV-GBS coordinated NOMA scheme achieves much higher sum rate of cell-edge users than the non-coordinated UAV-assisted NOMA schemes where interference is suppressed as much as possible. The proposed scheme also outperforms GBSs coordinated NOMA due to more flexible and cost-effective interference management, thanks to the deployment of low-cost UAV BS. We conduct joint optimization of power allocation, user scheduling and UAV trajectory for the UAV-GBS coordinated system. A closed-form optimal solution to power allocation is derived. In addition, a dedicated successive interference cancellation (SIC) ordering approach is proposed. It is proven that the selection of a cell-center user with higher SIC order contributes to a higher rate of cell-edge user, based on which an SIC order based user scheduling algorithm for both cell-center and cell-edge users is presented.

Time synchronization is crucial for wireless sensor networks (WSNs) since it maintains data consistency, coordination, and enables other fundamental operations. Over the last decade, a number of powerful time synchronization algorithms have been proposed for clock accuracy optimization by using signal processing techniques. However, most of these algorithms attempt to estimate the clock phase offset and skew and do not correct the node's local clock at every timing packet exchange before the clock parameters are jointly estimated, which reduces the network synchronization accuracy during the estimation of clock parameters and limits the applicability of the synchronization algorithms for some practical sensor networks where a global time scale is consistently required. Motivated by this, this paper investigates the synchronization scheme of having inactive nodes overhearing the pairwise sender-receiver time synchronization based on acknowledgement with clock correction at every synchronization. Assuming exponential random delays, the maximum likelihood estimators (MLEs) of clock skew and the corresponding approximate Cramer-Rao lower bounds (CRLBs) for active and overhearing nodes are derived. In addition, we also consider a linear synchronization model that the clock skew is directly estimated. Simulation results verify the efficiency of the clock skew estimators.

We investigate a downlink multi-cell non-orthogonal multiple access (NOMA) system with coordinated base stations (BSs) and propose a joint resource allocation (RA) scheme alongside adaptive user association to green the system. To the best of our knowledge, this is the first work to investigate joint allocation of subchannels and power for coordinated NOMA systems, while the previous work on RA for coordinated orthogonal multiple access (OMA) systems is not applicable. A serving channel gain based joint RA (SCG-JRA) algorithm is proposed, based on the theoretical proof that the total transmission power is mono-decreasing with respect to the SCGs of non-coordinated users. As for user association, an adaptive fuzzy logic (FL) based multi-criterion approach is proposed to achieve higher robustness against the combined effect of shadowing, fading and inter-cell interference, compared to the previous single-criterion based approaches. Numerical results show that the proposed SCG-JRA with adaptive FL based user association significantly outperforms the previous RA schemes assisted by single-criterion user association, in terms of energy efficiency (EE) and total transmission power, enabling a greener system.

The overhearing mechanism in time synchronization has been an active research area for wireless sensor networks (WSNs), for it can save a significant amount of energy by exploiting the wireless medium broadcast property. Recently, based on acknowledgment (ACK) mechanism, a synchronization scheme has been proposed for practical WSNs that the timestamps can be directly inserted into the data frame and the corresponding ACK, instead of dedicated synchronization packet. Consequently, the overhead of time synchronization could be further reduced. Motivated by this, in this letter, we analyze the synchronization of inactive nodes overhearing the pairwise synchronization on the basis of ACK mechanism, and present a linear estimation algorithm of clock frequency offset with the nodes' clock adjusted at every synchronization. Furthermore, assuming Gaussian delays, the linear estimation for frequency offset and the corresponding Cramer-Rao lower bound are derived. Simulation results verify that the estimator is efficient.

Combining non-orthogonal multiple access (NOMA) with coordination techniques among base stations (BSs) is a promising solution to enhance spectral efficiency and alleviate inter-cell interference of cell-edge users in 5th generation (5G) networks. In this paper, we consider a multi-cell NOMA network with coordinated BSs in the downlink, and investigate its user coordination mode selection and resource allocation to achieve a green system. A fuzzy logic (FL) based multi-criterion scheme is proposed for user coordination mode selection. It is more robust against shadowing and fading than the previous selection schemes that classify coordinated and non-coordinated users by a single criterion. Also, the FL ranking list is fed into subcarrier allocation, leading to significant reduction in searching complexity of subcarrier allocation. A dramatic performance enhancement is achieved over the previous schemes based on single-criterion, in terms of transmission power and energy efficiency.

We propose a novel low-complexity resource allocation scheme to provide a tradeoff between energy efficiency (EE) and spectral efficiency (SE) for multicarrier non-orthogonal multiple access (NOMA) systems with the constraint of user fairness. The proposed optimization approach provides high degree of freedom, as the tradeoff of EE and SE can be optimal by assigning their corresponding weights. Also, a closed-form expression is derived for subchannel power allocation with user fairness, requiring no high-complexity search. A suboptimal power allocation approach is proposed on each subchannel for NOMA user pairing. Numerical results show that the proposed NOMA system provides higher EE and SE than the state-of-art methods, while requiring low complexity.

Bamboo flowering is a complicate phenomenon for its long period and unpredictability. In this study, three successive stages of flowering buds from flowering bamboo (Lei bamboo, Phyllostachys violascens) plants and the corresponding vegetative buds of non-flowering plants were collected for transcriptome analysis. By using Illumina RNA-Seq method, about 442 million clean sequence reads were generated from the above samples and assembled into 317,273 transcripts with N50 of 1,968 bp, then acquired 132,678 unigenes with N50 of 1,080 bp, about 44.18% of the unigenes annotated in at least one database. 7,266 differentially expressed genes (DEGs) were determined through GO and KEGG analysis. Some DEGs were involved in plant hormone signal transduction and circadian rhythm pathways, which were highly expressed in the former and middle flower development stages, respectively. Our paper presents a useful data and a critical sampling method for studying flowering mechanism in bamboo.