QoS based fair resource allocation in multi-cell TD/CDMA communication systems

Abstract-In a wireless multimedia code division multiple access (CDMA) system, the resources in terms of transmission rate and power should be efficiently distributed to each user to guarantee its quality-of-service (QoS) requirements. In, this paper, a resource allocation algorithm which combines packet scheduling and power assignment is proposed to achieve efficient resource utilization under QoS constraints. The packet scheduling is based on the fair packet loss sharing (FPLS) principle, and the power assignment is determined by the received power limited (RPL) scheme. 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 with QoS satisfaction. The RPL scheme minimizes the received power for each packet. Given the propagation path loss, it in turn minimizes the transmitted power as well. The intercell interference from the scheduled packets is also limited in order to increase the system capacity.     

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.     

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 Bandwidth Management in Single-Hop Ad Hoc Wireless Networks

Distributed weighted fair scheduling schemes for Quality of Service (QoS) support in wireless local area networks have not yet become standard. Therefore, we propose an Admission Control and Dynamic Bandwidth Management scheme that provides fairness and a soft rate guarantee in the absence of distributed MAC-layer weighted fair scheduling. This scheme is especially suitable for smart-rooms where peer-to-peer multimedia transmissions need to adapt their transmission rates co-operatively. We present a mapping scheme to translate the bandwidth requirements of an application into its channel time requirements. The center piece of our scheme is a Bandwidth Manager, which allots each flow a share of the channel, depending on the flow's requirements relative to the requirements of other flows in the network. Admitted flows control their transmission rates so they only occupy the channel for the fraction of time allotted to them. Thus co-operation between flows is achieved and the channel time is fair shared. As the available channel capacity changes and the traffic characteristics of various flows change, the Bandwidth Manager dynamically re-allocates the channel access time to the individual flows. Our simulation experiments show that, at a very low cost and with high probability, every admitted flow in the network will receive at least its minimum requested share of the network bandwidth. We also present extensive testbed experiments with our scheme using a real-time audio streaming application running between Linux laptops equipped with standard IEEE 802.11 network cards.     

Soft QoS provisioning using the token bank fair queuing scheduling algorithm

Future-generation wireless packet networks will support multimedia applications with diverse QoS requirements. Much of the research on scheduling algorithms has been focused on hard QoS provisioning of integrated services. Although these algorithms give hard delay bounds, their stringent requirements sacrifice the potential statistical multiplexing performance and flexibility of the packet-switched network. Furthermore, the complexities of the algorithms often make them impractical for wireless networks. There is a need to develop a packet scheduling scheme for wireless packet-switched networks that provides soft QoS guarantees for heterogeneous traffic, and is also simple to implement and manage. This article proposes token bank fair queuing (TBFQ), a soft scheduling algorithm that possesses these qualities. This algorithm is work-conserving and has a complexity of O(1). We focus on packet scheduling on a reservation-based TDMA/TDD wireless channel to service integrated real-time traffic. The TBFQ scheduling mechanism integrates the policing and servicing functions, and keeps track of the usage of each connection. We address the impact of TBFQ on mean packet delay, violation probability, and bandwidth utilization. We also demonstrate that due to its soft provisioning capabilities, the TBFQ performs rather well even when traffic conditions deviate from the established contracts.     

Credit-based slot allocation for multimedia mobile ad hoc networks

This paper studies resource management for multimedia mobile ad hoc networks (MANET). In particular, we focus on providing fair scheduling with quality-of-service (QoS) support for MANET. We consider two types of flows: guaranteed and best effort flows. The goal is to satisfy the QoS requirements of guaranteed flows and to provide global fairness for best effort flows. In this paper, a credit-based fair scheduling mechanism called credit-based slot allocation protocol (CSAP) is proposed. In CSAP, nodes are logically grouped into clusters, each with a scheduler. Each scheduler assigns time slots to nodes in its cluster based on the first tier algorithm. The node scheduled to send at the next time slot then in turn assigns the time slot to a relayed flow determined by the second-tier algorithm. Each multihop flow is treated as multiple single-hop flow segments. These segments are then correlated such that a downstream segment will not be allocated a slot unless the upstream segments have all been allocated. We evaluate the performance of CSAP by simulations. The results show that CSAP meets the QoS requirements of guaranteed flows, provides global fairness for best effort flows, and improves overall system throughput.     

Scheduling schemes for multimedia service in wireless OFDM systems

Scheduling schemes play a key role in the system performance of broadband wireless systems such as WLANs/WMANs. Maximal SNR and round robin are two conventional scheduling strategies that emphasize efficiency and fairness, respectively. The proportional fair scheme provides a trade-off between efficiency and fairness, and has been well studied in TDMA and CDMA systems. In this article we extended the PF scheduling scheme to OFDM-based BWSs (OPF). In addition, we propose three variations: adaptive OPF (AOPF), multimedia AOPF (MAOPF), and normalized MAOPF (NMAOPF) in order to meet the QoS requirements for multirate services in multimedia systems. The adaptive modulation and coding schemes in time varying and frequency selective fading are considered. The system performances of the algorithms are compared in terms of efficiency (throughput and mean packet delay) and fairness (user satisfaction rate and average user rate). Joint physical and media access control layer simulation results show that AOPF and MAOPF can improve throughput at the cost of fairness, and NMAOPF can provide the highest throughput without losing fairness.     

A Unified Architecture for the Design and Evaluation of Wireless Fair Queueing Algorithms

Fair queueing in the wireless domain poses significant challenges due to unique issues in the wireless channel such as location-dependent and bursty channel errors. In this paper, we present a wireless fair service model that captures the scheduling requirements of wireless scheduling algorithms, and present a unified wireless fair queueing architecture in which scheduling algorithms can be designed to achieve wireless fair service. We map seven recently proposed wireless fair scheduling algorithms to the unified architecture, and compare their properties through simulation and analysis. We conclude that some of these algorithms achieve the properties of wireless fair service including short-term and long-term fairness, short-term and long-term throughput bounds, and tight delay bounds for channel access.     

A slotted CDMA protocol with BER scheduling for wireless multimedianetworks

In future wireless multimedia networks, there will be a mixture of different traffic classes which have their own maximum tolerable bit error rate (BER) requirements. In this paper, a novel medium access control (MAC) protocol called wireless multimedia access control protocol with BER scheduling (in short form, WISPER) for CDMA-based systems is proposed. WISPER utilizes the novel idea of scheduling the transmission of multimedia packets according to their BER requirements. The scheduler assigns priorities to the packets, and performs an iterative procedure to determine a good accommodation of the highest-priority packets in the slots of a frame so that packets with equal or similar BER requirements are transmitted in the same slots. The proposed WISPER protocol has been validated using a software emulator on the cellular environment. Performance evaluation results based on the implementation are also included     

QoS-, Queue-and Channel-Aware Packet Scheduling for Multimedia Services in Multiuser SDMA/TDMA Wireless Systems

With the growing demand for wireless multimedia services and continuing emergence of new multimedia applications, it is necessary for the network to provide various levels of quality of service (QoS) while maximizing the utilization of channel resources. This paper presents an adaptive queuing model and a novel cross-layer packet scheduling algorithm for providing differentiated QoS and effective channel utilization in a space-division-multiple-access/time-division-multiple-access (SDMA/TDMA) system. At the medium access control (MAC) layer, we take into consideration the heterogeneous and bursty nature of multimedia traffic and provide for QoS requirements. At the physical (PHY) layer, we exploit the randomness of the physical channel by incorporating opportunistic scheduling and adopting adaptive modulation and coding (AMC). Performance results obtained by simulations show that by employing the proposed queuing model and packet scheduling algorithm, the system is able to provide for diverse QoS and achieve high throughput.     

Performance Evaluation of the IEEE 802.16 MAC for QoS Support

The IEEE 802.16 is a standard for broadband wireless communication in metropolitan area networks (MAN). To meet the QoS requirements of multimedia applications, the IEEE 802.16 standard provides four different scheduling services: unsolicited grant service (UGS), real-time polling service (rtPS), non-real-time polling service (nrtPS), and Best Effort (BE). The paper is aimed at verifying, via simulation, the effectiveness of rtPS, nrtPS, and BE (but UGS) in managing traffic generated by data and multimedia sources. Performance is assessed for an IEEE 802.16 wireless system working in point-to-multipoint (PMP) mode, with frequency division duplex (FDD), and with full-duplex subscriber stations (SSs). Our results show that the performance of the system, in terms of throughput and delay, depends on several factors. These include the frame duration, the mechanisms for requesting uplink bandwidth, and the offered load partitioning, i.e., the way traffic is distributed among SSs, connections within each SS, and traffic sources within each connection. The results also highlight that the rtPS scheduling service is a very robust scheduling service for meeting the delay requirements of multimedia applications     

Self-coordinating localized fair queueing in wireless ad hoc networks

Distributed fair queueing in a multihop, wireless ad hoc network is challenging for several reasons. First, the wireless channel is shared among multiple contending nodes in a spatial locality. Location-dependent channel contention complicates the fairness notion. Second, the sender of a flow does not have explicit information regarding the contending flows originated from other nodes. Fair queueing over ad hoc networks is a distributed scheduling problem by nature. Finally, the wireless channel capacity is a scarce resource. Spatial channel reuse, i.e., simultaneous transmissions of flows that do not interfere with each other, should be encouraged whenever possible. In this paper, we reexamine the fairness notion in an ad hoc network using a graph-theoretic formulation and extract the fairness requirements that an ad hoc fair queueing algorithm should possess. To meet these requirements, we propose maximize-local-minimum fair queueing (MLM-FQ), a novel distributed packet scheduling algorithm where local schedulers self-coordinate their scheduling decisions and collectively achieve fair bandwidth sharing. We then propose enhanced MLM-FQ (EMLM-FQ) to further improve the spatial channel reuse and limit the impact of inaccurate scheduling information resulted from collisions. EMLM-FQ achieves statistical short-term throughput and delay bounds over the shared wireless channel. Analysis and extensive simulations confirm the effectiveness and efficiency of our self-coordinating localized design in providing global fair channel access in wireless ad hoc networks.     

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.     

Latency-rate servers: a general model for analysis of trafficscheduling algorithms

We develop a general model, called latency-rate servers (ℒℛ servers), for the analysis of traffic scheduling algorithms in broadband packet networks. The behavior of an ℒℛ server is determined by two parameters-the latency and the allocated rate. Several well-known scheduling algorithms, such as weighted fair queueing, virtualclock, self-clocked fair queueing, weighted round robin, and deficit round robin, belong to the class of ℒℛ servers. We derive tight upper bounds on the end-to-end delay, internal burstiness, and buffer requirements of individual sessions in an arbitrary network of ℒℛ servers in terms of the latencies of the individual schedulers in the network, when the session traffic is shaped by a token bucket. The theory of ℒℛ servers enables computation of tight upper bounds on end-to-end delay and buffer requirements in a heterogeneous network, where individual servers may support different scheduling architectures and under different traffic models     

A QoS Aware Dynamic Scheduling Scheme Using Fuzzy Inference System for IEEE 802.16 Networks

Providing quality of service (QoS) for diverse multimedia services is an important issue in IEEE 802.16 (WiMAX) networks. A scheduling mechanism that satisfies the QoS requirements has become more important for multimedia networks. In addition, scheduling algorithms for wireless networks are much more complex than that of wired networks because of channel quality variations and radio resource limits. This paper introduces a QoS Aware Scheduling System, based on fuzzy logic, for traffic management in WiMAX point-to-multi-point (PMP) networks. The proposed method attempts to guarantee delay and throughput QoS criteria. It considers QoS criteria and radio quality of each user in decision making processes. A series of simulation experiments have been carried out to evaluate the performance of the proposed scheduling system. The results show that the proposed method performs effectively to achieve QoS criteria and attains significant system performance for different types of traffic.     

基于双层分级的无线城域网资源分配方案

未来移动通信系统,诸如IEEE802.16旨在能够传送多种具有不同QoS要求的多媒体业务。为了保证业务的QoS,需合理设计调度器的结构和相应的调度算法。针对IEEE802.16宽带无线接入系统中的双层分级带宽分配体系结构,结合总调度器分配算法优点,采用了更适用于分类调度器且不同于参考文献的分配算法,旨在能够针对不同QoS等级的业务提供不同的调度方案,更好地满足用户的QoS要求。     

基于TG-PF的LTE-A中继蜂窝网络下行分层调度方法

设计了一种中继蜂窝网络的分层调度模型,将中继蜂窝小区的资源调度过程分为高层调度和低层调度两部分,分别由基站和中继站完成。所设计模型中,高层调度和低层调度分别采用PF算法和保障吞吐量的比例公平（TG-PF算法）,该算法充分利用了最大载干比（Max C/I）算法和比例公平（PF）算法的优势,能够有效地提升小区边缘的吞吐量,以满足中继蜂窝小区的系统吞吐量和调度公平性要求。仿真结果表明,所提方法能够以较低的调度公平性牺牲换取小区边缘吞吐量的较大提升。     

End to end QoS provisioning multimedia wireless/mobile networksusing an adaptive framework

This article presents a framework for multimedia networking in a wireless and mobile environment. We consider both multimedia application needs as well as networking requirements, and try to bridge these paradigms using an adaptive framework. Central to this framework is the concept of representing a multimedia connection in terms of multiple substreams each with their own specified QoS requirement and making network elements (switching and access points), services, and protocols (signaling, control, routing) aware of the QoS requirements of such substreams. As resource availability in the wireless and mobile network fluctuates, the network selects and schedules substreams in order to present the information content with an acceptable quality at a receiver (or each receiver in case of multicast connections). This is done while achieving a reasonable utilization efficiency of network resources and sharing them in a fair manner     

Wide-band TD-CDMA MAC with minimum-power allocation and rate- and BER-scheduling for wireless multimedia networks

A wide-band time-division-code-division multiple-access (TD-CDMA) medium access control (MAC) protocol is introduced in this paper. A new minimum-power allocation algorithm is developed to minimize the interference experienced by a code channel such that heterogeneous bit-error rate (BER) requirements of multimedia traffic are satisfied. Further, from analysis of the maximum capacity of a time slot, it is concluded that both rate and BER scheduling are necessary to reach a maximum capacity. Based on the new minimum-power allocation algorithm as well as on rate and BER scheduling concepts, a new scheduling scheme is proposed to serve packets with heterogeneous BER and quality of service (QoS) requirements in different time slots. To further enhance the performance of the MAC protocol, an effective connection admission control (CAC) algorithm is developed based on the new minimum-power allocation algorithm. Simulation results show that the new wide-band TD-CDMA MAC protocol satisfies the QoS requirements of multimedia traffic and achieves high overall system throughput.     

Downlink Wireless Packet Scheduling with Deadlines

Next-generation cellular wireless communication networks aim to provide a variety of quality-of-service (QoS)-sensitive packet-based services to downlink users. Included among these are real-time multimedia services, which have stringent delay requirements. Downlink packet scheduling at the base station plays a key role in efficiently allocating system resources to meet the desired level of QoS for various users. In this paper, we employ dynamic programming (DP) to study the design of a downlink packet scheduler capable of supporting real-time multimedia applications. Under well-justified modeling reductions, we extensively characterize structural properties of the optimal control associated with the DP problem. We leverage intuition gained from these properties to propose a heuristic scheduling policy, namely, Channel-Aware Earliest Due Date (CA-EDD), which is based on a "quasi- static" approach to scheduling. The per-time-slot implementation complexity of CA-EDD is only O(K) for a system with K downlink users. Experimental results show that CA-EDD delivers up to 50 percent of performance gains over benchmark schedulers. CA-EDD achieves these performance gains by using channel and deadline information in conjunction with application layer information (relative importance of packets) in a systematic and unified way for scheduling.