Analytical evaluation of average delay and maximum stable throughput along a typical two-way street for vehicular ad hoc networks in sparse situations

Intermittent connectivity is an intrinsic feature of vehicular ad hoc networks (VANETs) in sparse situations. This type of network is in fact an example of delay and disruption tolerant networks (DTNs). In this paper, we focus on a typical two-way street and analytically evaluate the maximum stable throughput and the average delay for packet forwarding along the street. To this end, we map the mobility patterns of the vehicles with different speeds onto suitable parameters of a BCMP queueing network and derive the location density of vehicles. Then, we employ another queueing network in order to model opportunistic multi-hop packet forwarding along the street with respect to the specifications of MAC and routing schemes. We propose a two-mode MAC scheme suitable for DTNs with predictable mobility patterns. We also consider the effect of vehicles’ velocities and opportunistic relaying for routing schemes. In our analysis, we evaluate the average delay and the maximum stable throughput for the proposed MAC and routing schemes. In the last part of the paper, we show the efficiency of the proposed analytical approach by some numerical results and confirm our analysis by simulation.     

LTE系统多小区上行联合功控算法

针对传统的小区内开环功率控制算法通常以提升本小区的吞吐量性能为目标，忽略了当前小区用户对邻小区用户同频干扰的问题，为提升边缘用户性能的同时兼顾系统整体性能，提出了一种LTE系统小区间上行联合功率控制（UJPC）算法。该算法采用单基站三扇区为系统模型，以最优化系统吞吐量比例公平函数为目标，首先根据最小信干噪比（SINR）约束值和用户最大发射功率这两个约束条件得到相应的数学优化模型，然后采用连续凸近似的方法求解优化问题得出各个基站所管辖的小区内所有用户的最优发射功率。仿真结果表明，与基准的开环功控方案相比，联合功控方案在保证系统平均频谱利用率的情况下能够较大幅度地提高小区边缘频谱利用率，其最佳性能增益能达到50%。     

Research on user pairing algorithm for LTE femtocell uplink

In this article,a new simulated annealing based bit error rate pairing scheduling(SA-BPS)algorithm for LTE femtocell uplink virtual multiple input multiple output(V-MIMO)systems is proposed,which uses Round Robin(RR)criterion to decide the first user,and simulated annealing(SA)algorithm with objective function of bit error rate(BER)is suggested to decide the pairing users.The SA-BPS is considered not only to be used for inner layer user pairing within femtocell user equipments(HUEs)to increase spectrum efficiency,but also to be used for cross layer user pairing between HUEs and macrocell user equipments(MUEs)to cancel the cross layer interference from MUEs to HUEs.As a growth control coefficient is used in SA-BPS to control the growth of average BER of users in the pairing group,rapid user BER deterioration can be prevented by adopting a proper coefficient.Simulation results show that,the SA-BPS outperforms RPS,DPS,and the conventional SA algorithm in terms of BER performance,whether used for inner layer user pairing or cross layer user pairing.Also,the mode switching signal to interference ratio(SIR)threshold between inner and cross layer user pairing are obtained by simulation in three cross layer interference power distribution scenarios.     

Research on user for LTE fem pairing algorithm tocell uplink

In this article, a new simulated annealing based bit error rate pairing scheduling （SA-BPS） algorithm for LTE femtocell uplink virtual multiple input multiple output （V-MIMO） systems is proposed, which uses Round Robin （RR） criterion to decide the first user, and simulated annealing （SA） Mgorithm with objective function of bit error rate （BER） is suggested to decide the pairing users. The SA-BPS is considered not only to be used for inner layer user pairing within femtocell user equipments （HUEs） to increase spectrum efficiency, but also to be used for cross layer user pairing between HUEs and macrocell user equipments （MUEs） to cancel the cross layer interference from MUEs to HUEs. As a growth control coefficient is used in SA-BPS to control the growth of average BER of users in the pairing group, rapid user BER deterioration can be prevented by adopting a proper coefficient. Simulation results show that, the SA-BPS outperforms RPS, DPS, and the conventional SA algorithm in terms of BER performance, whether used for inner layer user pairing or cross layer user pairing. Also, the mode switching signal to interference ratio （SIR） threshold between inner and cross layer user pairing are obtained by simulation in three cross layer interference power distribution scenarios.     

A uplink radio resource allocation scheme for localized SC-FDMA transmission in LTE network

The radio resource allocation is one of the most important issues to achieve effective wireless communication. In Long Term Evolution (LTE) network, single carrier frequency division multiple access (SC-FDMA) is applied as the transmission technology for uplink traffic. Most researches focus on maximizing the system throughput of SC-FDMA under changeable channel condition. However, users may require different quality of services (QoS) for different applications. This paper studies radio resource allocation for QoS users in localized SC-FDMA system. The proposed scheme divides allocation process into matching algorithm and radio resource assignment algorithm. The Gale–Shapley algorithm is applied to find the optimal matching between resource blocks (RB) and user equipment (UE) by considering channel conditions and the desired QoS. Then the resource assignment algorithm heuristically allocates bandwidth to UE by referring the matched RB under the constraint of carrier continuity. This paper modified the Recursive Maximum Expansion (RME) algorithm to effectively assign radio resource for UEs with different bandwidth demands. The performance of our proposed scheme is compared with the modified RME scheme through exhaustive simulations. The video streaming, VoIP, and FTP traffic types were adopted for simulations. Our simulation results show that the proposed scheme achieves better QoS satisfaction and system throughput than the RME-modified scheme.     

LTE上行信道交织与解交织的研究及DSP实现

详细分析了PUSCH信道交织的具体过程,并根据定点TMS320C6455的特点,提出了一种简单的PUSCH信道交织与解信道交织实现方案.将程序在CCS3.3中运行,利用MATALAB软件验证了该方案的可行性和高效性.     

Analytical solution methods for the fuzzy weighted average

For the fuzzy weighted average (FWA), despite various discrete solution algorithms and their improvements, attempts at analytical solutions are very rare. This paper provides an analytical solution method for the FWA based on the conclusions of the Karnik–Mendel (KM) algorithm. Compared with the two current popular kinds of α-cut based computational methods for the FWA (mathematical programming transformations and direct iterate computations), our method is precise, and, has a concise structure, efficient computation process, and sound theoretical proofs. We propose two algorithms for computing the analytical solution of the FWA. Two numerical examples illustrate our proposed approach.     

The effect of system response delay and delay variability on inexperienced videotex users

To test the effects of system response delay and delay variability on users of videotex it was decided to experiment in a context close to that of the service under consideration. Accordingly 165 subjects were drawn from the general public to try videotex in a series of four experiments. An emphasis on performance-related outcome measures was deemed inappropriate. Accordingly, a strategy using stepwise multiple regression followed by factor analysis selected 11 important variables from an original 38. Then these were clustered into four linear combinations or scales labelled session length, passivity, speed of response and difficulty. All four experiments failed to find any significant effects due to mean response delay. Two of the three experiments that tested ranges of randomized delay with rectangular distributions found significant disruptive effects on users. These results replicate earlier studies, and extend their generality to the context of naive users of videotex. The results also support the concept of using response-style scales rather than performance measures in non-work settings, and they contribute to the construct validity of the scales.     

基于网络控制系统平均时延的模糊控制器设计

针对网络控制系统(NCS)中的随机时延问题,根据实际网络时延的分布情况,提出一种新的具有随机时廷的网络控制系统的建模方法--离散T-S模型,并在此基础上应用并行分布补偿原理(PDC)设计模糊控制器.同时提出一种新的模糊控制系统隶属函数的确定方法,利用Lyapunov定理和线性矩阵不等式(LMI)研究系统的稳定性问题,给出了基于LMI的模糊控制器的设计方法.最后通过仿真实例验证了该控制方法能使具有时延的网络控制系统稳定.     

Analytical models for availability evaluation of edge and fog computing nodes

The Journal of Supercomputing - Although cloud computing environments increase availability, reliability, and performance, many emerging technologies demand latency-aware networks for real-time...     

无线传感器网络中平均时延约束的自适应休眠机制

针对流量动态变化的无线传感器网络,提出了具有平均时延约束的自适应休眠机制.在休眠阶段,节点采取自适应地周期性休眠和苏醒来节省能量且保证平均传输延迟.在苏醒周期的节点没有数据发送或者收到目的地址为其他节点的RTS/CTS帧后进入休眠周期.通过建立马尔科夫链模型分析可得到该机制中平均时延约束下休眠周期的优化值.     

Joint optimization of delay and cost for microservice composition in mobile edge computing

World Wide Web - With the development of software technology, some complex mobile and Internet-of-Things (IoT) applications can be constituted by a set of microservices. At present, mobile edge...     

Low complexity cell search scheme for LTE and LTE-advanced mobile technologies

In this paper, we propose a novel method to accomplish the cell search procedure in Long Term Evolution (LTE) and LTE-Advanced (LTE-A) mobile systems. By means of detecting the cyclic prefix (CP) configuration in the time domain, it is possible to reduce both the inter symbolic interference (ISI) and the inter carrier interference (ICI) prior to the detection of dedicated synchronization signals (SS) involved in cell search procedure. Thus, the SS detection is efficiently performed in the frequency domain while the implementation complexity is reduced, since the proposed architecture minimizes the necessity of matched filters. Results show that cell search procedure is successfully accomplished while keeping the cell search time in the range of 3–5 radio frames.     

LTE小区搜索中一种新的SSS检测算法

主要研究了SSS检测, 提出一种新的SSS检测算法。该算法首先利用滑动平均窗修正接收的PSS处估计出的信道频率响应, 并用修正后的信道频率响应对接收的SSS序列进行信道补偿; 其次, 算法对信道补偿后的序列进行实数提取操作, 消除虚部数据干扰; 最后算法联合两个连续的SSS接收序列进行检测进一步提高检测性能。TDD和FFD两种模式下的仿真结果表明：该算法可以较好地实现SSS检测且比现有几种SSS检测算法在低信噪比（SNR<0 dB）条件下具有更好的检测性能。     

LTE小区搜索中定时与频偏估计算法研究

在长期演进（LTE）的小区搜索中,定时同步与频偏估计是一个非常重要的同步过程。基于分段相关算法,提出了一种改进算法。利用分段相关算法具有抗频偏的优点结合差分运算,并采用对接收端信号进行累积处理方法,提高了定时同步精度。将本地PSS信号累积相加的结果与接收信号进行相关运算,有效降低了算法的运算量。同时利用本地PSS信号与接收PSS信号的相关性,提出一种有效的频偏估计算法。理论分析与仿真实验表明,与传统算法相比,提出的定时与频偏估计算法有效提高了估计精度,减小了运算量。     

化工不稳定时滞过程鲁棒控制的解析设计

针对化工不稳定时滞过程,提出一种两自由度控制结构.首先基于鲁棒H2最优性能指标,设计给定值跟踪控制器;然后根据系统稳态运行时的抗负载干扰要求,在过程输入与输出端之间设计控制闭环,利用其反馈通道上的扰动观测器抑制负载干扰,通过提出期望的闭环余灵敏度函数的方法,反向确定扰动观测器,同时给出了该控制闭环保证鲁棒稳定性的充要条件.仿真实例验证了该控制结构的优越性.     

An LP approach to full-order and reduced-order state estimations of positive Markov jump systems with delay

In this paper, the problems of full-order and reduced-order positive state estimations are developed for discrete-time positive Markov jump linear systems with delay. By establishing a positive time-delay system for 1-moment function of the state vector, delay-dependent necessary and sufficient exponential stability conditions are first derived based on a comparison technique for positive systems. Then, on the basis of the derived stability conditions, the problems of designing positive state observers in full-order and reduced-order for positive Markov jump systems with delay are addressed. The existence conditions of positive observers and the design schemes are formulated in terms of linear programming problems which can be effectively solved by various optimisation algorithms to obtain the observer parameters. Finally, three numerical examples with simulations are given to validate the analysis and design results.     

Minimum hop flow assignment and routing subject to an average message delay constraint

An algorithm for minimum hop flow assignment and routing in message-switched networks subject to an average message delay constraint is developed and illustrated. The development is based on an analysis of the original problem formulation in terms of the minimum achievable average message delay as a function of the average number of hops. From this analysis, it is found that the problem can be solved via successive application of a modified flow deviation method in which average message delay is minimized subject to a constraint on the average number of hops. The resulting algorithm is simple and efficient. It obtains the desired solution directly if one exists or shows that no solution is possible, the latter occurring when there is no feasible flow assignment and routing which can satisfy the delay constraint. An example involving a network with 10 nodes, 36 links and 40 commodities is given, and directions for future research are indicated.     

Exponential stabilisation for time-varying delay system with actuator faults: an average dwell time method

The issue of exponential stabilisation for a class of special time-varying delay switched systems resulting from actuator faults is considered in this article. The time-varying delay is assumed to belong to an interval and can be a slow or fast time-varying function. A hybrid state feedback strategy is redesigned to guarantee the system stable since the original controller is unavailable for some actuators failures. A class of switching laws incorporating the average dwell time method is proposed so that the special switched system with interval time-varying delay is exponentially stable. New delay-range-dependent stabilisation conditions using state feedback controllers are formulated in terms of linear matrix inequalities (LMIs) by choosing appropriate Lyapunov–Krasovskii functional without neglecting some useful knowledge on system states. Parameterised characterisations of the controllers are given in terms of the feasibility solutions to the LMIs. Two numeral examples are given to demonstrate the applicability and the effectiveness of the proposed method.     

Analytical design of two-degree-of-freedom control scheme for open-loop unstable processes with time delay

This paper proposes an analytical two-degree-of-freedom control scheme for open-loop unstable processes with time delay, which leads to the remarkable improvement of regulatory capacity for both of reference input tracking and load disturbance rejection. Firstly a conventional proportional or plus derivative controller is deliberately employed for stabilizing the setpoint response. Then the setpoint tracking controller is analytically derived in terms of the integral-squared-error (ISE) performance specification. By proposing the desired closed-loop complementary sensitivity function for rejecting load disturbances, the corresponding controller, i.e. disturbance estimator, is inversely figured out. Hence the nominal setpoint response is decoupled from the load disturbance response by virtue of the open-loop control manner for the setpoint tracking. In consequence, both of them can be optimized simultaneously and separately. At the same time, robust stability analysis for the proposed control structure is provided in the presence of the process multiplicative uncertainty. Accordingly the on-line tuning rule for the single adjustable parameter of each controller is suggested to cope with the process unmodeled dynamics in practice. Finally, several illustrative examples are included to demonstrate the superiority of the proposed method.