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1.
蜂窝车联网(C-V2X)与车载自组织网络(VANET)的异构融合能够有效提高网络容量。然而,不同网络在非授权频段上共存而引起的信道冲突会导致系统吞吐量降低和用户接入时延增大,无法满足车联网用户对服务质量(QoS)的需求。针对该问题,该文提出一种基于用户个性化QoS需求的时频资源分配方法。首先,分别对C-V2X 和 VANET 的吞吐量和时延进行建模分析,刻画用户数据传输时间配置与吞吐量和时延的数学关系;然后,基于上述模型构建吞吐量-时延联合优化函数,根据用户的个性化QoS需求实现异构网络中吞吐量和时延的优化;最后,提出一种基于改进多目标粒子群优化的时延-吞吐量联合优化算法(DT-JOA)进行求解。仿真结果表明,该文所提网络资源分配算法可以有效地保证用户的个性化QoS需求,提升异构网络综合性能。  相似文献   

2.
蜂窝车联网(C-V2X)与车载自组织网络(VANET)的异构融合能够有效提高网络容量.然而,不同网络在非授权频段上共存而引起的信道冲突会导致系统吞吐量降低和用户接入时延增大,无法满足车联网用户对服务质量(QoS)的需求.针对该问题,该文提出一种基于用户个性化QoS需求的时频资源分配方法.首先,分别对C-V2X 和 VANET 的吞吐量和时延进行建模分析,刻画用户数据传输时间配置与吞吐量和时延的数学关系;然后,基于上述模型构建吞吐量-时延联合优化函数,根据用户的个性化QoS需求实现异构网络中吞吐量和时延的优化;最后,提出一种基于改进多目标粒子群优化的时延-吞吐量联合优化算法(DT-JOA)进行求解.仿真结果表明,该文所提网络资源分配算法可以有效地保证用户的个性化QoS需求,提升异构网络综合性能.  相似文献   

3.
In this paper, we address the problem of minimizing energy consumption in a CDMA-based wireless sensor network (WSN). A comprehensive energy consumption model is proposed, which accounts for both the transmit and circuit energies. Energy consumption is minimized by jointly optimizing the transmit power and transmission time for each active node in the network. The problem is formulated as a non-convex optimization. Numerical as well as closed-form approximate solutions are provided. For the numerical solution, we show that the formulation can be transformed into a convex geometric programming (GP), for which fast algorithms, such as interior point method, can be applied. For the closed-form solution, we prove that the joint power/time optimization can be decoupled into two sequential sub-problems: optimization of transmit power with transmission time serving as a parameter, and then optimization of the transmission time. We show that the first sub-problem is a linear program while the second one can be well approximated as a convex programming problem. Taking advantage of these analytical results, we further derive the per-bit energy efficiency. Our results are verified through numerical examples and simulations  相似文献   

4.
Nodes in vehicular ad-hoc network (VANET) are highly mobile, traversing in unpredictable and varying environment. Therefore, contention window size and transmission power should adapt according to the high mobility transmission environment. In this paper, we propose an adaptive VANET medium access control (MAC) layer with joint optimization for VANET (MACVS) which aims at minimizing average delay and maximizing packet success rate. An adaptive joint optimization with proposed threshold structure dynamic programming, with closed loop feedback control system, is designed to optimize contention window size and transmission power. Adaptive optimization is done based on road traffic conditions and transmission reliable distance range (depicted by interference and noise), by monitoring the continuous change and threshold of received signal strength to interference and noise ratio. Mathematical expressions have been developed for the MACVS optimization framework, and the produced analytical results show good agreement with the simulation results. Simulations with different arrival rates and urban map of city center show that the proposed MACVS with low complexity joint optimization effectively reduces end-to-end delay while achieving high packet success rate under various network traffic condition.  相似文献   

5.
刘韬 《电子学报》2016,44(2):301-307
本文将效用模型引入无线传感器网络的功率控制设计中,提出了一种基于效用模型的分布式功率控制机制(简称UMDPC).该机制建立了网络中所有传感器节点的功率与效用模型的对应关系,将链路可靠性、网络能耗归纳到统一的网络效用优化框架中,并证明该效用优化问题是凸优化问题,构造基于对偶分解的分布式的优化算法,获得网络效用最大化条件下各节点的优化发射功率.最后,通过模拟实验对所提机制及其实现算法的性能进行比较和评价.实验结果表明,本文所提机制最大化了网络的效用,提高了网络的能量利用效率.  相似文献   

6.
Modern wireless communication networks frequently have lower application throughput due to higher number of collisions and subsequent retransmission of data packets. Moreover, these networks are characterized by restricted computational capacity due to limited node‐battery power. These challenges can be assessed for deploying fast, reliable network design with resource‐restrained operation by means of concurrent optimization of multiple performance parameters across different layers of the conventional protocol stack. This optimization can be efficiently accomplished via cross‐layer design with the aid of network coding technique and optimal allocation of limited resources to wireless links. In this paper, we evaluate and analyze intersession coding across several source–destination pairs in random access ad hoc networks with inherent power scarcity and variable capacity links. The proposed work addresses the problem of joint optimal coding, rate control, power control, contention, and flow control schemes for multi‐hop heterogeneous networks with correlated sources. For this, we employ cross‐layer design for multiple unicast sessions in the system with network coding and bandwidth constraints. This model is elucidated for global optimal solution using CVX software through disciplined convex programming technique to find the improved throughput and power allocation. Simulation results show that the proposed model effectively incorporates throughput and link power management while satisfying flow conservation, bit error rate, data compression, power outage, and capacity constraints of the challenged wireless networks. Finally, we compare our model with three previous algorithms to demonstrate its efficacy and superiority in terms of various performance metrics such as transmission success probability, throughput, power efficiency, and delay.  相似文献   

7.
A new medium access protocol which exploits the physical layer capability of multiuser detection is proposed to help in improving the throughput/delay performance of ad-hoc networks. When more than one node has packets buffered for a common node in the neighborhood, all such nodes can simultaneously transmit their packets to the common receiver after reserving their surrounding channel. This is achieved in our protocol by extending the (sender-initiated) CSMA/CA collision avoidance framework by the receiver-initiated medium access technique and incorporating the transmission power control. We analyze the improvement in the throughput that can be achieved over the basic sender-initiated collision avoidance protocol in the network. Since the throughput improvement via multi-packet reception is influenced by the network layer activity as well, the performance of our protocol rolls back to that of the basic sender-initiated protocol in case of no coordination from the network layer. For the evaluation of performance of our protocol we simulate ad-hoc networks for different network topologies and traffic configurations. We observe the scheme to be capable in significantly improving the throughput/delay performance of the network.  相似文献   

8.

To attain high quality of service (QoS) with efficient power consumption with minimum delay through Wireless Local Area Network (WLAN) through mesh network is an important research area. But the existing real-time routing system involves multiple hops with time varying mobility channels for fastest data propagation is greatly degraded with power utilization factor through congestion traffic queue. Required allocation and resource management through desired access points plays vital roles in which multiple hops demands delay rates by interconnected data nodes. In order to achieve high throughput with minimum delay the QoS in real-time data communication have to be concentrated by using Viterbi decoder with convolution codes. By undertaking IEEE 802.11 WLAN physical layers afford multiple transmission rates by engaging various modulations and channel coding schemes, major point arises to pinpoint the desired transmission rate to enhance the performance. Because each node exhibits different dynamic characteristics based on the token rings passed from the server to the end links. In order to validate the real-time traffic with power consumption and average delay communication, an improved Viterbi decoder is designed with convolution codes to determine accurate channel estimation based on learning the utilization ration of the needed to execute the current wireless channel optimization. The proposed methodology can attain accurate channel estimation without additional implementation effort and modifications to the current 802.11 standard. And each node is capable to choose the optimized transmission rate, so that the system performance can be improved with very minimum power with high packet transmission ratio with minimum traffic rate to improve QoS. The proposed scheme also offers an appealing combination of the allocation of transmission rate and the current link condition. Based on the basic relationship between them, the proposed decoding scheme maximizes the throughput with periodic learning of channel variation and system status.

  相似文献   

9.
赵方圆  韩昌彩  李媛 《信号处理》2013,29(4):480-485
为最大化无线自组织网络的吞吐量,提出一种自适应的协作路由算法。在算法中,协作分集技术与路由选择相结合,通过在路由的每一跳选择最佳的中继节点协作发送节点传输信息来改善网络吞吐量。首先通过目的序列距离矢量路由协议(DSDV)初步建立最短路由路径,在每条链路的发送节点和接收节点根据邻节点表选出公共邻居节点,建立候选中继集合;进一步,每一跳根据链路吞吐量,在候选中继集合中自适应选择最多两个中继来协助发送节点进行传输,并根据选出的中继节点数动态分配节点发射功率。在保证系统发射功率一定的情况下,最大化网络吞吐量。仿真结果表明,在相同的发射功率下,相对于非协作路由DSDV算法,采用固定数量中继的协作路由算法提高了整个网络的吞吐量,而自适应的协作路由算法可进一步提高吞吐量;同时仿真了网络吞吐量与网络规模和节点最大移动速度的变化关系。   相似文献   

10.
The IEEE 802.11 standard inherently supports multiple data rates at the physical layer. Various rate adaptation mechanisms have been proposed to exploit this multirate capability by automatically adapting the transmission rate to best utilize the wireless spectrum. This study is primarily motivated by the observation that in a wireless network, a multihop high-rate path can potentially achieve better throughput and delay than using a single-hop low-rate path for transmission. Specifically, this paper introduces a relay-aided media access (RAMA) protocol by taking advantage of the existence of such multihop high-rate links. This is demonstrated by replacing one low-rate link with two high-rate links using a relay node. One of the key novelties in the proposed RAMA protocol is that the transmission from the immediate relay node to the destination node is free of contention. Results from analysis and simulations show that RAMA can significantly improve performances in terms of both throughput and delay.  相似文献   

11.
为了满足车联网中不同应用的服务质量(Quality of Service, QoS)要求,提出了一种基于网络切片技术的车联网频谱资源分配方案。该方案考虑数据接入控制,通过联合优化频谱资源块(Resource Block, RB)分配和车辆信号发射功率控制,在安全服务切片低时延高可靠性的约束下,最大化信息娱乐服务切片的平均和吞吐量。将车联网资源管理建模为一个混合整数随机优化问题,利用李雅普诺夫(Lyapunov)优化理论将该优化问题分解为接入控制和RB分配与功率控制两个子问题,并分别对其进行求解,得到每个时隙的接入控制和资源分配方案。仿真结果表明,所提出的资源分配方案能够有效提高信息娱乐服务切片的平均和吞吐量,并且可以通过调整引入的控制参数值来实现吞吐量和时延的动态平衡。同时,与已有方案相比,该方案具有更好的时延性能。  相似文献   

12.
In a relay‐assisted cellular network, the transmission mode (either direct transmission or relaying) and the transmit power of the source and relay nodes affect not only transmission rates of individual links but also the rates of other links sharing the same channel. In this paper, we propose a cross‐layer design that jointly considers the transmission mode/relay node selection (MRS) with power allocation (PA) to optimize the system rate. We first formulate an optimization problem for a cellular system, where the same frequency channel can be reused in different cells. A low complexity heuristic MRS scheme is proposed on the basis of the link and interference conditions of the source and potential relay nodes. Given the transmission mode and relay node (if the relaying mode is chosen) of each link, the transmit power of the source and relay nodes can be solved by geometric programming. This method for MRS and PA can achieve a close‐to‐optimum performance, but implementing the PA requires heavy signalling exchanged among cells. To reduce the signalling overheads, we finally proposed a heuristic and distributed method for MRS and PA inspired by some asymptotic analysis. Numerical results are conducted to demonstrate the rate performance of the proposed methods.Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

13.
李校林  周冰  卢清 《电讯技术》2015,55(1):73-79
在MU-Co MP-JT(Multi-User Coordinated Multiple-Points Joint Transmission)联合资源分配问题中,传统的迫零预编码矩阵会使得每根天线发送功率互不相同,当Co MP节点发射功率仅满足总功率约束时性能损失不明显,而当Co MP节点分布在不同的地理位置时将受到单节点功率约束,这势必会降低系统功率利用率。为了进一步提升系统吞吐量,基于对偶分解理论提出了一种联合预编码优化的资源分配算法。该算法以最大化用户权重速率为目标,将原优化问题分解成若干个优化的子问题,不同子问题对应不同接收天线数的联合优化问题。当子信道的发送天线数大于接收天线数时,通过多次迭代计算得到预编码矩阵,并且预编码矩阵会随着拉格朗日因子的变化而变化。仿真结果表明所提联合预编码优化的联合资源分配算法能够明显提升系统吞吐量,且提高天线功率利用效率。  相似文献   

14.
The mismatch of transmission ability causes the discontinuous transmission of video services in fiber-wireless access network,aimed at this problem,an QoE-aware video distribution mechanism was proposed.According to the structural characteristics of fiber-wireless access network,link state information and scalable video coding structure was considered,a QoE evaluation mode was established,and the particle swarm optimization algorithm was used to select optimal video transmission rate.Then the node transmission capacity and the node matching degree was analyzed,transmission path for the services was selected,so as to ensure the reliable transmission of services.The results show that the proposed mechanism can effectively improve the utilization rate of network resources and reduce network congestion while improving the quality of the user experience.  相似文献   

15.
In this paper, the effect of transmission power on the throughput capacity of finite ad hoc wireless networks, considering a scheduling-based medium access control (MAC) protocol such as time division multiple access (TDMA) and an interference model that is based on the received signal-to-interference-plus-noise ratio (SINR) levels, is analyzed and investigated. The authors prove that independent of nodal distribution and traffic pattern, the capacity of an ad hoc wireless network is maximized by properly increasing the nodal transmission power. Under the special case of their analysis that the maximum transmission power can be arbitrarily large, the authors prove that the fully connected topology (i.e., the topology under which every node can directly communicate with every other node in the network) is always an optimum topology, independent of nodal distribution and traffic pattern. The present result stands in sharp contrast with previous results that appeared in the literature for networks with random nodal distribution and traffic pattern, which suggest that the use of minimal common transmission power that maintains connectivity in the network maximizes the throughput capacity. A linear programming (LP) formulation for obtaining the exact solution to the optimization problem, which yields the throughput capacity of finite ad hoc wireless networks given a nodal transmit power vector, is also derived. The authors' LP-based performance evaluation results confirm the distinct capacity improvement that can be attained under their recommended approach, as well as identify the magnitude of capacity upgrade that can be realized for networks with random and uniform topologies and traffic patterns.  相似文献   

16.
陈秉试 《通信技术》2015,48(3):289-294
针对基于802.11p的车载自组织网络(VANET, Vehicular Ad hoc Network)的吞吐量最优化问题,采用启发式搜索优化的思想,在数据传输方面提出了改进的搜索者优化算法(ISOA, Improved Seeker Optimization Algorithm)。该算法通过对节点发送概率的最优化实现节点平均吞吐量的最大化;通过对吞吐量变化的检测调整发送概率,实现对通信环境变化的自适应性;通过对在VANET场景下传统SOA的改进,提高了搜索全局最优解的成功率。仿真结果表明,ISOA较传统算法在环境变化自适应性方面更好,在收敛速度及准确度等方面性能也更优。  相似文献   

17.
In this paper, we address the rate control problem in a multihop random access wireless network, with the objective of achieving proportional fairness amongst the end-to-end sessions. The problem is considered in the framework of nonlinear optimization. Compared with its counterpart in a wired network where link capacities are fixed, rate control in a multihop random access network is much more complex and requires joint optimization at both the transport and link layers. This is due to the fact that the attainable throughput on each link in the network is “elastic” and is typically a nonconvex and nonseparable function of the transmission attempt rates. Two cross-layer algorithms, a dual-based algorithm and a penalty-based algorithm, are proposed in this paper to solve the rate control problem in a multihop random access network. Both algorithms can be implemented in a distributed manner, and work at the link layer to adjust link attempt probabilities and at the transport layer to adjust session rates. We prove rigorously that the two proposed algorithms converge to the globally optimal solutions. Simulation results are provided in support of our conclusions.  相似文献   

18.
栾鹏  朱江  高凯 《电讯技术》2016,56(9):990-994
针对浮标卫星通信系统中卫星覆盖范围广、接入链路传播时延差异大的场景结构引起的统一延迟分配协议中端到端时延长、吞吐率低的问题,提出了一种基于位置信息的时隙分配协议。协议中卫星通过获取浮标位置信息来控制时隙分配的起点,实现时隙离散分配,增大可用传输时隙长度,同时降低传输时延。 OPNET 仿真结果表明所提出的时隙分配协议可以显著提高单信道传输模式下的网络吞吐量,并有效降低单信道与双信道模式下浮标卫星通信系统接入时的端到端时延。  相似文献   

19.
Spatial reuse TDMA has been proposed as an access scheme for multi-hop radio networks where real-time service guarantees are important. The idea is to increase capacity by letting several radio terminals use the same time slot when possible. A time slot can be shared when the radio units are geographically separated such that small interference is obtained. In reuse scheduling, there are several alternative assignment methods. Traditionally, transmission rights are given to nodes or to links, i.e., transmitter/receiver pairs. We present a comparison of these two approaches and show that both have undesirable properties in certain cases, e.g. link assignment gives a higher delay for low traffic loads but can achieve much higher throughput than node assignment. Furthermore, we propose a novel assignment strategy, achieving the advantages of both methods. Simulation results show that the proposed method can achieve the throughput of link assignment for high traffic loads as well as the lower delay characteristics of node assignment for low traffic loads.  相似文献   

20.
该文提出了支持多输入多输出(MIMO)链路的Ad hoc网络的链路激活型拓扑未知多址接入协议。该协议利用正交拉丁方来为网络链路分配传输时隙,保证每个链路在1帧中至少有1个时隙可以成功传输。推导了该协议的平均吞吐量,并以最大化平均吞吐量为准则给出了选择协议参数的方法。数值结果表明,与已有链路激活型和节点激活型拓扑未知协议相比,本文的协议可以提高网络节点的吞吐量。  相似文献   

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