A fair optimization scheduling scheme for IEEE 802.16 networks in multimedia applications

IEEE 802.16 networks are designed based on differentiated services concept to provide better Quality of Service (QoS) support for a wide range of applications, from multimedia to typical web services, and therefore they require a fair and efficient scheduling scheme. However, this issue is not addressed in the standard. In this paper we present a new fair scheduling scheme which fulfills the negotiated QoS parameters of different connections while providing fairness among the connections of each class of service. This scheme models scheduling as a knapsack problem, where a fairness parameter reflecting the specific requirements of the connections is defined to be used in the optimization criterion. The proposed scheduler is evaluated through simulation in terms of delay, throughput and fairness index. The results show fairness of the scheduling scheme to all connections while the network guarantees for those connections are fulfilled.     

Dynamic fair scheduling with QoS constraints in multimedia wideband CDMA cellular networks

A class of dynamic fair scheduling schemes based on the generalized processor sharing (GPS) fair service discipline, under the generic name code-division GPS (CDGPS), is proposed for a wideband direct-sequence code-division multiple-access (CDMA) cellular network to support multimedia traffic. The CDGPS scheduler makes use of both the traffic characteristics in the link layer and the adaptivity of the wideband CDMA physical layer to perform fair scheduling on a time-slot by time-slot basis, by using a dynamic rate-scheduling approach rather than the conventional time-scheduling approach. Soft uplink capacity is characterized for designing an efficient CDGPS resource allocation procedure. A credit-based CDGPS (C-CDGPS) scheme is proposed to further improve the utilization of the soft capacity by trading off the short-term fairness. Theoretical analysis shows that, with the C-CDGPS scheme, tight delay bounds can be provided to delay-sensitive traffic, and short-term unfairness can be bounded so that long-term weighted fairness for all users can still be satisfied. Simulation results show that bounded delays, increased throughput, and long-term fairness can be achieved for both homogeneous and heterogeneous traffic.     

Enhanced fair earliest due date first scheduling strategy for multimedia applications in LTE downlink framework

Guaranteeing a certain delay threshold for delay‐sensitive applications in long term evolution (LTE) cellular communication system is a very challenging mission. By implementing an optimal scheduling strategy, this mission will be achieved. In this article, a novel scheduler is introduced in order to meet a predefined level of service quality by guaranteeing a specific delay threshold for delay‐sensitive applications in LTE cellular systems. The proposed scheduler assigns the available resource blocks (RBs) to active user equipments (UEs) tacking into consideration several attributes. The expiration date of each packet, the channel quality, the average data rate previously achieved by each UE, and the number of dropped packets for each UE compared with the average number of packets totally dropped are all considered in the proposed scheduler working mechanism. Consequently, the proposed scheduling strategy reduces the number of packets dropped for multimedia applications, and at the same time maximizes the overall throughput of the network. Simulation results are provided to study and evaluate the performance of the proposed scheduling strategy. A comparative study is presented between the proposed strategy and the most recent scheduling techniques. The obtained results prove that the proposed scheduling strategy has considerably acceptable and appreciated results compared with the results of the state‐of‐the‐art scheduling techniques.     

多媒体云计算下的大规模数据流调度方法研究

传统的多媒体数据流调度方法在云平台环境下,未考虑服务器信息调度的差异性,容易形成数据调度冲突,调度效率低。为了解决上述分析的问题,通过构建多媒体云计算下数据流调度平台,实现对多路大规模多媒体数据流的合理调度,利用多级分层结构将多媒体云计算下的多服务器大规模数据流调度过程划分成管理层面、控制层面以及数据层面,可确保将数据包均匀的分配给各个服务器,充分发挥云计算下的多服务器可并行处理的特性,增强数据流的调度质量。对调度平台的软件框架进行了详细的描述,依据该软件框架的多层次实现大规模数据流调度优化,分析了大规模数据流调度的具体实现过程,并给出大规模数据流调度平台软件代码的设计。实验结果表明,所提方法增强了多媒体云计算下的大规模数据流调度的并发性能,提高数据流调度质量。     

Adaptive rate-controlled scheduling for multimedia applications

We present a framework for integrated scheduling of continuous media (CM) and other applications. The framework, called ARC scheduling, consists of a rate-controlled on-line CPU scheduler, an admission control interface, a monitoring module, and a rate adaptation interface. ARC scheduling allows threads to reserve CPU time for guaranteed progress. It provides firewall protection between threads such that the progress guarantee to a thread is independent of how other threads actually make scheduling requests. Rate adaptation allows a CM application to adapt its rate to changes in its execution environment. We have implemented the framework as an extension to Solaris 2.3. We present experimental results which show that ARC scheduling is highly effective for integrated scheduling of CM and other applications in a general purpose workstation environment. ARC scheduling is a key component of an end system architecture we have designed and implemented to support networking with quality of service guarantees. In particular, it enables protocol threads to make guaranteed progress     

改进的正比公平调度算法

3GPP从R6版本开始,开展了对高速上行分组接入(HSUPA)技术的研究和标准制定工作。基于基站(NodeB)的调度算法是HSUPA的三大技术之一,对它的研究能有效地改善HSUPA系统性能,使系统的上行资源得以更充分的利用。在简述HSUPA中基于NodeB的典型调度算法的基础上,它针对用户的公平性给出了三种改进的正比公平调度算法,并在吞吐量和公平性上与典型调度算法进行仿真对比,仿真验证了当各个信道的衰落特性差别很大时,与正比公平调度算法相比,改进的正比公平调度算法有效地提高了用户的公平度,改善了系统性能。     

Channel predictive proportional fair scheduling

Recent work on channel modeling and prediction has shown the feasibility of predicting the mobile radio channel, quite accurately, several milliseconds ahead in time for realistic Doppler spreads. Motivated by these results we consider opportunistic scheduling algorithms that exploit both current and future channel estimates. We demonstrate how this extra channel information can be used to improve the scheduling. Simulations show that the proposed algorithm can improve the inherent tradeoff between throughput, fairness and delay. The current approach builds on proportional fair scheduling but can also be generalized to other criteria.     

A proportional fair scheduling for multicarrier transmission systems

This letter extends the proportional fair (PF) scheduling proposed in the high data rate (HDR) system to multicarrier transmission systems. It is known that the PF allocation (F. P. Kelly et al. (1998)) results in the maximization of the sum of logarithmic average user rates. We propose a PF scheduling that assigns users to each carrier while maximizing the sum of logarithmic average user rates.     

Instability of the proportional fair scheduling algorithm for HDR

In this letter, we study the Proportional Fair scheduler that has been proposed for scheduling in the high data rate (HDR) wireless data system. We consider a single basestation transmitting to a set of mobile users. In each time slot, the scheduler has to decide on a mobile to which it will transmit data. The decision is based on information that the basestation receives about the time-varying channels between itself and the mobiles. We focus on deciding whether or not Proportional Fair is stable in a situation with finite queues and a data arrival process. That is, we wish to decide if Proportional Fair keeps all queues bounded whenever this is feasible. There are, in fact, multiple versions of Proportional Fair, depending on how it treats small queues. In this letter, we consider six different versions and show that all are unstable for one simple example.     

Adaptive proportional fair scheduling with global-fairness

Wireless Networks - In practical communication systems, there are always multiple subscribers competing for limited resources, such as time and frequency, hence effective user scheduling is...     

Proportional fair scheduling with reduced feedback

An opportunistic feedback technique is proposed for proportional fair (PF) scheduling in a downlink multi-user system. This technique requires each mobile station, the scheduling metric of which is higher than a threshold, to send one-bit feedback for PF scheduling. The scheduler determines the optimal modulation and coding scheme for a scheduled user based on channel quality indicator (CQI) update, which is sent on a longer period than the scheduling period. The simulation results indicate that PF scheduling with the proposed update scheme can achieve similar performance as PF scheduling with full CQI feedback. The feedback overhead can be reduced in comparison with typical PF scheduling provided that an optimal CQI update period is chosen.     

一种抑制小区间干扰的比例公平调度算法

针对LTE-Advanced系统中小区间干扰及用户公平性问题,提出了基于多小区联合预编码和静态功率控制的比例公平(MCPPC-PF)调度算法。通过干扰空间迫零和静态控制发射功率的方法抑制小区间干扰,并结合比例公平(PF)调度算法,提高用户的公平性。仿真结果表明,与传统算法相比,MCPPC-PF算法提升系统容量的同时还提高了用户的公平性;与基于多小区联合预编码和静态功率控制的最大化吞吐量调度算法相比,MCPPC-PF算法在系统容量损失了4.6%的情况下,边缘用户容量提高了约45%。     

Dynamic bandwidth allocation with fair scheduling for WCDMA systems

Dynamic bandwidth allocation (DBA) will play an important role in future broadband wireless networks, including the 3G and 4G WCDMA systems. A code-division generalized processor sharing (CDGPS) fair scheduling DBA scheme is proposed for WCDMA systems. The scheme exploits the capability of the WCDMA physical layer, reduces the computational complexity in the link layer, and allows channel rates to be dynamically and fairly scheduled in response to the variation of traffic rates. Deterministic delay bounds for heterogeneous packet traffic are derived. Simulation results show that the proposed CDGPS scheme is effective in supporting differentiated QoS, while achieving efficient utilization of radio resources.     

QoS-oriented packet scheduling for wireless multimedia CDMA communications

In the third-generation (and beyond) wireless communication systems, there will be a mixture of different traffic classes, each having its own transmission rate characteristics and quality-of-service (QoS) requirements. In this paper, a QoS-oriented medium access control (MAC) protocol with fair packet loss sharing (FPLS) scheduling is proposed for wireless code-division multiple access (CDMA) communications. The QoS parameters under consideration are the transmission bit error rate (BER), packet loss, and delay requirements. The MAC protocol exploits both time-division and code-division statistical multiplexing. The BER requirements are guaranteed by properly arranging simultaneous packet transmissions and controlling there transmit power levels, whereas the packet loss and delay requirements are guaranteed by proper packet scheduling. The basic idea of FPLS is to schedule the transmission of multimedia packets in such a way that all the users have a fair share of packet loss according to their QoS requirements, which maximizes the number of the served users under the QoS constraints. Simulation results demonstrate effectiveness of the FPLS scheduler, in comparison with other previously proposed scheduling algorithms.     

Approximate fair bandwidth sharing in high-speed multimedia networks

Existing fair-queuing algorithms use complicated flow management mechanisms, thus making them expensive to deploy in current high-bandwidth networks. In this paper we propose a scalable SCORE (stateless core) approach to provide fair bandwidth sharing for a traffic environment composed of TCP and UDP flows. At an edge router, the arrival rates of each flow are estimated, each packet then being labelled with this estimate. The outgoing link’s fair share at a router is estimated based on UDP traffic. Probabilistic dropping is used to regulate those flows that send more than the fair share. At a core router, all the functions performed by an edge router are repeated, excluding the flow rate estimation. The simulation results show that the degree of fairness achieved by the proposed solution is comparable to that of other algorithms, but with a lower implementation cost.     

Distributed fair scheduling in a wireless LAN

Fairness is an important issue when accessing a shared wireless channel. With fair scheduling, it is possible to allocate bandwidth in proportion to weights of the packet flows sharing the channel. This paper presents a fully distributed algorithm for fair scheduling in a wireless LAN. The algorithm can be implemented without using a centralized coordinator to arbitrate medium access. The proposed protocol is derived from the Distributed Coordination Function in the IEEE 802.11 standard. Simulation results show that the proposed algorithm is able to schedule transmissions such that the bandwidth allocated to different flows is proportional to their weights. An attractive feature of the proposed approach is that it can be implemented with simple modifications to the IEEE 802.11 standard.     

无线接入网络自适应公平调度算法

研究了无线接入网络环境下自适应公平调度模型,讨论了服务区分的必要性和无线网络调度补偿方法,设计了一种二级结构的服务区分自适应公平调度算法,算法能够区分不同服务类型,公平分配网络资源。对于链路造成的暂时性服务中断给予了多级服务补偿,并通过分组级的公平资源分配,保障服务质量和流队列的平滑降级。     

Designing a fair scheduling mechanism for IEEE 802.11 wireless LANs

A fair scheduling mechanism called distributed elastic round robin (DERR) is proposed in this letter for IEEE 802.11 wireless LANs operated in a distributed manner. To quantify the fairness, we not only derive its fairness bound, but also observe the fairness through ratios of throughput and weight using a simulation approach. By numerical comparisons among DERR, distributed deficit round robin (DDRR), and IEEE 802.11e, we demonstrate that DERR outperforms the other two mechanisms in performance and fairness.     

Adaptive opportunistic fair scheduling over multiuser spatial channels

We consider the problem of opportunistic fair scheduling (OFS) of multiple users in downlink time-division multiple-access (TDMA) systems employing multiple transmit antennas and beamforming. OFS is an important technique in wireless networks to achieve fair bandwidth usage among users, which is performed on a per-frame basis at the media access control layer. Multiple-transmit-antenna beamforming provides TDMA systems with the capability of supporting multiple concurrent transmissions, i.e., multiple spatial channels at the physical layer. Given a particular subset of users and their channel conditions, the optimal beamforming scheme can be calculated. The multiuser opportunistic scheduling problem then refers to the selection of the optimal subset of users for transmission at each time instant to maximize the total throughput of the system subject to a certain fairness constraint on each individual user's throughput. We propose discrete stochastic approximation algorithms to adaptively select a better subset of users. We also consider scenarios of time-varying channels for which the scheduling algorithm can track the time-varying optimal user subset. We present simulation results to demonstrate the performance of the proposed scheduling algorithms in terms of both throughput and fairness, their fast convergence, and the excellent tracking capability in time-varying environments.     

The specification of the temporal behaviour for multimedia scheduling

In this paper, we present a timing model for describing the temporal behaviour of a multimedia application. This timing model is based on the so called temporal profiles. After illustrating such a notion through examples, we specify formally temporal profiles and the scheduling problem through a relation between temporal profiles.