基于星上处理的卫星ATM中ABR 业务拥塞控制算法研究

卫星ATM是近年来通信领域的研究热点,拥塞控制是其中很关键的一个问题.本文主要研究基于星上处理的卫星ATM网的ABR流量控制,它通过对流量的长时预测来达到控制目的.由于卫星信道的大延时,无法实现精确的长时预测,因而将预测结果直接用于ABR的拥塞控制效果不甚理想.将长时预测同动态利用因子控制的方法结合之后,在链路效率、信元丢失率、不同连接数目和暂态响应等方面都取得很好的结果.     

Radio resource management across multiple protocol layers in satellite networks: a tutorial overview

Satellite transmissions have an important role in telephone communications, television broadcasting, computer communications, maritime navigation, and military command and control. Moreover, in many situations they may be the only possible communication set‐up. Trends in telecommunications indicate that four major growth market/service areas are messaging and navigation services (wireless and satellite), mobility services (wireless and satellite), video delivery services (cable and satellite), and interactive multimedia services (fibre/cable, satellite). When using geostationary satellites (GEO), the long propagation delay may have great impact, given the end‐to‐end delay user's requirements of relevant applications; moreover, atmospheric conditions may seriously affect data transmission. Since satellite bandwidth is a relatively scarce resource compared to the terrestrial one (e.g. in optical transport networks), and the environment is harsher, resource management of the radio segment plays an important role in the system's efficiency and economy. The radio resource management (RMM) entity is responsible for the utilization of the air interface resources, and covers power control, handover, admission control, congestion control, bandwidth allocation, and packet scheduling. RRM functions are crucial for the best possible utilization of the capacity. RRM functions can be implemented in different ways, thus having an impact on the overall system efficiency. This tutorial aims to provide an overview of satellite transmission aspects at various OSI layers, with emphasis on the MAC layer; some cross‐layer solutions for bandwidth allocation are also indicated. Far from being an exhaustive survey (mainly due to the extensive nature of the subject), it offers the readers an extensive bibliography, which could be used for further research on specific aspects. Copyright © 2005 John Wiley & Sons, Ltd.     

Simulation and analysis of software defined cognitive frequency hopping multi beam satellite system

Traditional multi-beam satellites cannot adapt to the changing traffic because of the fixed bandwidth and cannot adjust dynamically for the traffic load.In the future,the multi-beam broadband satellite system must have great flexibility and can be dynamically adjusted according to the change of the traffic flow.Beam hopping for multi-beam broadband satellite network system has been proposed to improve the traditional multi-beam broadband satellite network system performance,whose principle is to assign different beams to different time slots,rather than the allocation of bandwidth,so that in each time slot,the entire available bandwidth is allocated to each beam,and the time window is periodically applied to the beam selection system ,in the full band hopping mode,the band can be selected optimally in the duration of each beam to meet user transmission bandwidth and delay requirements.With the development of cognitive radio technology,cognitive beam hopping for multi-beam satellite system can further improve the efficiency of spectrum utilization,to meet the growing shortage of spectrum resources,to achieve large-capacity high-bandwidth broadband satellite network system,and to support the rising user service capacity and the transmission efficiency of user services under different load conditions.In addition,software definition technology is also used in satellite networks,which could achieve effective management of satellite resources to improve the utilization of satellite resources.In this paper,the principle of software-defined cognitive hopping multi-beam broadband satellite network system is discussed.The spectrum utilization efficiency and throughput are analyzed,which can be used as a reference for broadband satellite network system design.     

Application of a new explicit‐rate ABR traffic controller

In broadband integrated communication systems, the classical method of max–min fair‐rate allocation for traffic control does not support the weighted‐rate guarantee. The weighted‐rate guarantee is necessary for available‐bit rate (ABR) service models. This fact motivates that the weighted max–min (WMM) fair‐rate allocation for the ABR traffic is widely studied. However, the combination of close‐loop feedback control with WMM algorithm has not appeared in the previous research. In this paper, a practical WMM fair‐rate allocation model is proposed. This scheduling scheme combines and integrates the congestion avoidance using proportional control (CAPC) and the weighted max–min fair‐rate allocation. This model is designed to achieve higher utilization and also bounded delay for ABR traffic flow control. In the system under analysis, the performance of this new weighted traffic scheduler is evaluated. The system presented in this paper is also compared with WMM and CAPC methods. Copyright © 2001 John Wiley & Sons, Ltd.     

Congestion management techniques for disruption‐tolerant satellite networks

Delay and disruption‐tolerant networks are becoming an appealing solution for extending Internet boundaries toward challenged environments where end‐to‐end connectivity cannot be guaranteed. In particular, satellite networks can take advantage of a priori trajectory estimations of nodes to make efficient routing decisions. Despite this knowledge is already used in routing schemes such as contact graph routing, it might derive in congestion problems because of capacity overbooking of forthcoming connections (contacts). In this work, we initially extend contact graph routing to provide enhanced congestion mitigation capabilities by taking advantage of the local traffic information available at each node. However, since satellite networks data generation is generally managed by a mission operation center, a global view of the traffic can also be exploited to further improve the latter scheme. As a result, we present a novel strategy to avoid congestion in predictable delay‐ and disruption‐tolerant network systems by means of individual contact plans. Finally, we evaluate and compare the performance improvement of these mechanisms in a typical low Earth orbit satellite constellation.     

量子保密通信网络骨干链路流量规划

量子保密通信网络是一种新兴的安全网络。如何通过合理的流量规划方法提升量子保密通信网络骨干链路的带宽利用率、提升网络性价比是一个新问题。分析了量子保密通信网络流量规划的特殊性,给出了一种流量规划模型,可以实现下列 3 个方面的目标：在确定网络骨干链路密钥分发带宽的情况下,可以实现用户广域加密通信带宽的规划;借助路由规划可以提升用户广域加密通信带宽和量子链路密钥分发带宽的利用率;可以实现对网络瓶颈量子链路密钥分发带宽的合理调整。最后,通过数值模拟示例演示了本文所提出的流量规划方法的应用。     

基于智能网络的租户服务质量保证技术

在多租户虚拟网络环境中,用户对于网络服务的多样性以及性能的稳定性需求并不会随着网络架构和运营模式的升级而削弱,用户需求之间的差异性和动态性对于不同切片间资源的分配和调度效率提出了新的挑战.针对多租户虚拟网络的特殊环境,首先提出了QVR(QoS-Virtual Routing)流量调度算法,同时将用户流量调度与网络虚拟资...     

Buffer and bandwidth allocation for TCP data traffic: experimental results

This paper discusses the dimensioning of buffers and the bandwidth allocation for data traffic in the ATM network. Data traffic is notoriously complex and bursty, making such dimensioning a difficult task. However, the COMBINE project, when dimensioning their InterWorking Units (IWUs), adopted a Poissonian packet arrival model, based upon the argument that burstiness at timescales higher than that of a packet arrival are a problem to be tackled by flow control at higher layers. This paper presents experimental results from the COMBINE testbed that show that this hypothesis was justified and that good TCP goodput was obtained based upon this dimensioning approach, due to TCP's ability to adapt to network congestion. However, it is also shown that it was the TCP algorithm that was ultimately responsible for controlling the packet loss ratio in the network and not the bandwidth allocation or buffer size. The results highlight the importance of taking into account the mutual influence between the ATM layer and the transport layer congestion control algorithms.     

Class Dependent Traffic Allocation in a LEO Satellite Network

Traffic allocation strategy becomes a significant factor in optimization of bandwidth usage of telecommunication resources, especially with increasing use of broadband applications. Allocation strategy in dynamic LEO (Low Earth Orbital) satellite communication network is studied, to improve their Quality of Service (QoS). Traffic allocation control is performed to provide a near optimal utilization of their Inter Satellite Links (ISLs). A combination of two algorithms is used to allocate traffic in ISLs. Empirical analysis is performed to examine performance of the proposed algorithm, GALPEDA. Result shows that the proposed algorithm is useful for traffic allocation of multiclass traffic in LEO satellite communication.     

Adaptive low‐priority transfer for high bandwidth and delay product networks

As the exponential growth of the Internet, there is an increasing need to provide different types of services for numerous applications. Among these services, low‐priority data transfer across wide area network has attracted much attention and has been used in a number of applications, such as data backup and system updating. Although the design of low‐priority data transfer has been investigated adequately in low speed networks at transport layer, it becomes more challenging for the design of low‐priority data transfer with the adaptation to high bandwidth delay product networks than the previous ones. This paper proposes an adaptive low‐priority protocol to achieve high utilization and fair sharing of links in high bandwidth delay product networks, which is implemented at transport layer with an end‐to‐end approach. The designed protocol implements an adaptive congestion control mechanism to adjust the congestion window size by appropriate amount of spare bandwidth. The improved congestion mechanism is intent to make as much use of the available bandwidth without disturbing the regular transfer as possible. Experiments demonstrate that the adaptive low‐priority protocol achieve efficient and fair bandwidth utilization, and remain non‐intrusive to high priority traffic. Copyright © 2016 John Wiley & Sons, Ltd.     

On the effects of traffic mixtures in direct broadcast satellite networks

In this paper we present a multi‐criterion control simulation in a realistically complex environment of a satellite network, involving non‐symmetric up and downlinks. Direct broadcast satellite (DBS) networks carrying heterogeneous traffic is characterized with challenges, such as high traffic burstiness, wireless channel dynamics, and large, but limited capacity. On the other hand, there are system characteristics that can be leveraged to address these challenges such as in centralized topology, different levels in quality of service (QoS) and priorities, availability of side information about channel conditions, flexibility in delivery of delay insensitive traffic, etc. We have developed an adaptive resource allocation and management (ARAM) system that takes the advantage of such characteristics to maximize the utilization of the available capacity on the forward DBS link, while maintaining QoS in the presence of channel effects and congestion in the network. Since variable‐bit‐rate (VBR) video traffic is given priority over available‐bit‐rate (ABR) data traffic in the ARAM concept, in this paper we investigate the impact of the fraction of VBR load in overall load. Copyright © 2002 John Wiley & Sons, Ltd.     

Estimation and Prediction‐Based Connection Admission Control in Broadband Satellite Systems

We apply a “sliding‐window” Maximum Likelihood (ML) estimator to estimate traffic parameters of On‐Off source and develop a method for estimating stochastic predicted individual cell arrival rates. Based on these results, we propose a simple Connection Admission Control (CAC) scheme for delay sensitive services in broadband onboard packet switching satellite systems. The algorithms are motivated by the limited onboard satellite buffer, the large propagation delay, and low computational capabilities inherent in satellite communication systems. We develop an algorithm using the predicted individual cell loss ratio instead of using steady state cell loss ratios. We demonstrate the CAC benefits of this approach over using steady state cell loss ratios as well as predicted total cell loss ratios. We also derive the predictive saturation probability and the predictive cell loss ratio and use them to control the total number of connections. Predictive congestion control mechanisms allow a satellite network to operate in the optimum region of low delay and high throughput. This is different from the traditional reactive congestion control mechanism that allows the network to recover from the congested state. Numerical and simulation results obtained suggest that the proposed predictive scheme is a promising approach for real time CAC.     

业务优先级感知的网络流量调度机制

针对网络中业务数据流过大、分布不均匀所造成的网络拥塞,提出一种优先级感知的动态网络流量调度机制.利用令牌桶算法,根据业务优先级的不同为不同业务分配不同速率的令牌,以实现业务优先级的划分;综合考虑业务的优先级及用户节点剩余缓存空间,对不同的业务采取不同的处理方式;同时,以流量到达因素、服务因素及节点缓存为指标定义了一种网络流量调度机制性能指标——分组丢失率.数值结果表明,所提机制可以对网络中业务优先级进行合理的划分,从而有效利用网络资源,预防网络拥塞,提升网络性能,为用户提供更加稳定可靠的网络服务.     

Active intra-ONU scheduling with proportional guaranteed bandwidth in long-reach EPONs

The unused slot remainder (USR) problem in Ethernet Passive Optical Networks and long-reach Passive Optical Networks (LR-PONs) results in both a lower bandwidth utilization and a greater packet delay. In a previous study by the current group, an Active intra-ONU Scheduling with predictive queue report scheme was proposed for resolving the USR problem by predicting the granted bandwidth in advance based on the arrival traffic estimates of the optical network units (ONUs). However, it was found that the higher bandwidth prediction error in the proposed scheme prevents the network performance from being improved. Accordingly, the present study proposes a non-predictive-based ONU scheduling method designated as Active intra-ONU Scheduling with proportional guaranteed bandwidth (ASPGB) to improve the performance of LR-PONs. In the proposed method, the maximum guaranteed bandwidth of each ONU is adapted dynamically in accordance with the ratio of the ONU traffic load to the overall system load. Importantly, the proposed dynamic bandwidth allocation approach reduces the dependence of the network performance on the granted bandwidth prediction since the maximum guaranteed bandwidth determined by the Optical Line Terminal more closely approaches the actual bandwidth demand of each ONU. To solve the idle time problem arising in the event of an excess bandwidth reallocation, ASPGB is integrated with an improved early allocation (IEA) algorithm (a kind of Just-In-Time scheduling). The simulation results show that the IEA-ASPGB scheme outperforms previously published methods in terms of bandwidth utilization and average packet delay under both balanced and unbalanced traffic load conditions.     

A bandwidth assignment algorithm on a satellite channel for VBR traffic

Variable bit rate (VBR) video is currently by far the most interesting and challenging real-time application. A VBR encoder attempts to keep the quality of video output constant and at the same time reduces bandwidth requirements, since only a minimum amount of information has to be transferred. On the other hand, as VBR video traffic is both highly variable and delay-sensitive, high-speed networks (e.g. ATM) are generally implemented by assigning peak rate bandwidths to VBR video applications. This approach may, however, be inefficient in a satellite network based on a TDMA scheme. To overcome this problem, we have designed a demand assignment satellite bandwidth allocation algorithm in TDMA, named V2L-DA (VBR 2-Level Demand Assignment), which manages the VBR video traffic according to a dynamic bandwidth allocation algorithm. In this paper we discuss how to tune the proposed algorithm in order to optimize network utilization when MPEG-1 VBR video traffic is being transmitted. Our results indicate that most of the time only 40% of the peak rate bandwidth is needed to satisfy the VBR source, so the remaining 60% of the peak rate bandwidth can be used to transmit the datagram traffic queued in the network stations. © 1997 John Wiley & Sons, Ltd.     

Comprehensive bandwidth utilization and polling mechanism for XGPON

For an efficient utilization of the upstream bandwidth in passive optical network, a dynamic bandwidth assignment mechanism is necessary as it helps the service providers in provisioning of bandwidth to users according to the service level agreements. The scheduling mechanism of existing schemes, immediate allocation with colorless grant and efficient bandwidth utilization (EBU), does not assign the surplus bandwidth to a specific traffic class and only divides it equally among the optical network units (ONUs). This results in overreporting of ONU bandwidth demand to the optical line terminal and causes wastage of bandwidth and increase in delays at high traffic loads. Moreover, the EBU also assigns the unused bandwidth of lightly loaded ONU queues to the overloaded queues through an Update operation. This Update operation has a flaw that it borrows the extra bandwidth to a queue in the current service interval, if the queue report is higher than its service level agreement and refunds in next service interval. This borrow‐refund operation causes reduced bandwidth allocation to the lower priority classes and increases their delay and frame loss. This study improves both these weaknesses. The simulation results show that the proposed scheme uses bandwidth efficiently and reduces mean upstream delay of type‐2 (T2) traffic class by 38% and type‐3 (T3) up to 150% compared to immediate allocation with colorless grant at a cost of up to 10% higher delay for T2. However, T4 performance improves by 400% compared to EBU with slight increase in delay for T2 traffic class. Overall, it shows a balanced performance for all the traffic classes and minimizes the bandwidth waste per cycle as well as the frame loss rate.     

Bandwidth utilization efficiency enhancement for OFDM‐based WSN

Normally IEEE 802.16 (WiMAX) is used for mainly downlink traffic applications. However in the upper tier of 2‐tier (WiMAX‐WiFi) wireless sensor network, the uplink bandwidth faces bottlenecks for high throughput. In this paper, a solution has been proposed for this limitation of uplink bandwidth allocation through the use of queuing theoretic performance modeling. A Markov‐modulated Poisson process traffic model has been formed for orthogonal frequency division multiple access‐based transmission along with discrete time Markov chain system model for queuing. A downlink traffic pattern has been defined for wireless sensor network nodes. Analytical methods are used to estimate the performance parameters like throughput, delay, and probability of packet drop for resource allocation. An algorithm is formulated to find out minimum resource requirement for downlink and to transfer rest of the resources to uplink bandwidth allocation, for throughput enhancement. Uplink frame utilization is determined through another discrete time Markov chain model for adaptive triggering between the proposed maximum and the normal downlink to uplink ratio operations, for efficient distribution of bandwidth resources. Algorithm and simulation results prove outstanding improvement in the uplink throughput around 50%, without degrading the downlink throughput.     

基于OFDM-PON动态带宽分配算法研究

正交频分复用是一种多载波调制技术,用于解决各种无线和有线通信系统中因信道色散引起的符号间干扰问题。近年来的研究表明,OFDM在无源光网络方面有广泛地应用前景。文中以OFDM-PON为对象,对其传输性能、动态带宽分配算法进行了研究。提出了基于传统CP算法的改进算法,使OFDM-PON系统的上行带宽分配性能得到改善。经过建模仿真证明,系统上行业务时延和链路利用率都得到了提高。     

An optimal solution to resource allocation among soft QoS traffic in wireless network

Optimization theory and nonlinear programming method have successfully been applied into wire‐lined networks (e.g., the Internet) in developing efficient resource allocation and congestion control schemes. The resource (e.g., bandwidth) allocation in a communication network has been modeled into an optimization problem: the objective is to maximize the source aggregate utility subject to the network resource constraint. However, for wireless networks, how to allocate the resource among the soft quality of service (QoS) traffic remains an important design challenge. Mathematically, the most difficult comes from the non‐concave utility function of soft QoS traffic in the network utility maximization (NUM) problem. Previous result on this problem has only been able to find its sub‐optimal solution. Facing this challenge, this paper establishes some key theorems to find the optimal solution and then present a complete algorithm called utility‐based allocation for soft QoS to obtain the desired optimal solution. The proposed theorems and algorithm act as designing guidelines for resource allocation of soft QoS traffic in a wireless network, which take into account the total available resource of network, the users’ traffic characteristics, and the users’ channel qualities. By numerical examples, we illustrate the explicit solution procedures.Copyright © 2013 John Wiley & Sons, Ltd.