An Efficient Resource Allocation Strategy for Future Wireless Cellular Systems

Future mobile communication systems will be designed to support a wide range of data rates with complex quality of service matrix. It is becoming more challenging to optimize the radio resource management and maximise the system capacity whilst meeting the required quality of service from user?s point of view. Traditional schemes have approached this problem mainly focusing on resources within a cell and to large extent ignoring effects of multi-cell architecture. This paper addresses the influence of multi-cell interference on overall radio resource utilisation and proposes a novel approach, setting a new direction for future research on resource scheduling strategies in a multicell system. It proposes a concept called Load Matrix (LM) which facilitates joint management of interference within and between cells for allocation of radio resources. Simulation results show significant improvement in the resource utilization and o verall network performance. Using the LM strategy, average cell throughput can be increased as much as 30% compared to a benchmark algorithm. Results also show that maintaining cell interference within a margin instead of a hard target can significantly improve resource utilization.     

一种适用于W-CDMA系统的多业务无线资源调度算法

3G系统将以分组交换方式提供语音、数据、视频等具有不同QoS要求的多种业务，资源调度对保证系统服务质量和提高资源利用效率起关键作用．本文提出了一种基于业务类型、当前待发送负荷以及剩余延时限的时间调度策略和基于资源优化的资源调度策略，并使无线链路的传输质量与业务的优先级水平一致．通过系统仿真评价了算法的性能．     

Integrated Radio Resource Allocation for Multihop Cellular Networks With Fixed Relay Stations

Recently, the notion that a logical next step towards future mobile radio networks is to introduce multihop relaying into cellular networks, has gained wide acceptance. Nevertheless, due to the inherent drawbacks of multihop relaying, e.g., the requirement for extra radio resources for relaying hops, and the sensitivity to the quality of relaying routes, multihop cellular networks (MCNs) require a well-designed radio resource allocation strategy in order to secure performance gains. In this paper, the optimal radio resource allocation problem in MCNs, with the objective of throughput maximization, is formulated mathematically and proven to be NP-hard. Considering the prohibitive complexity of finding the optimal solution for such an NP-hard problem, we propose an efficient heuristic algorithm, named integrated radio resource allocation (IRRA), to find suboptimal solutions. The IRRA is featured as a low-complexity algorithm that involves not only base station (BS) resource scheduling, but also routing and relay station (RS) load balancing. Specifically, a load-based scheme is developed for routing. A mode-aware BS resource-scheduling scheme is proposed for handling links in different transmission modes, i.e., direct or multihop. Moreover, a priority-based RS load balancing approach is presented for the prevention of the overloading of RSs. Within the framework of the IRRA, the above three functions operate periodically with coordinated interactions. To prove the effectiveness of the proposed IRRA algorithm, a case study was carried out based on enhanced uplink UMTS terrestrial radio access/frequency-division duplex with fixed RSs. The IRRA is evaluated through system level simulations, and compared with two other cases: 1) nonrelaying and 2) relaying with a benchmark approach. The results show that the proposed algorithm can ensure significant gains in terms of cell throughput     

Cross-Layer Radio Resource Allocation for Multicarrier Air Interfaces in Multicell Multiuser Environments

Packet scheduling over shared channels is one of the most attractive issues for researchers dealing with radio resource allocation in wireless networks as modern systems' different traffic types, with different application requirements, need to coexist over the air interface. Recently, attention has been attracted to multicarrier techniques and the application of cross-layer approaches to the design of wireless systems. In this paper, a radio access network using a multicarrier air interface is considered in a multicell multiuser context. We propose a new cross-layer scheduling algorithm that manages channel, physical layer, and application-related information; we compare its performance with a previously published cross-layer strategy and with simpler well-known channel-aware or channel-unaware techniques and then discuss its optimization. We investigate the performance in terms of perceived user quality and fairness in the presence of mixed realistic traffic composed of H.264 video streaming with tight bounds on the delay jitter and file transfer protocol (FTP) data. To support video traffic, application-suited buffer-management techniques are also considered in conjunction with scheduling, and link adaptation is implemented at the physical layer to better exploit channel fluctuations. The role of scheduling and resource-allocation functionalities are discussed. It is shown that the cross-layer strategy proposed guarantees the same performance obtained by the previously published algorithm while reducing complexity. Moreover, under heavily loaded conditions, the cross-layer scheduling strategy provides a significant gain with respect to simple channel-aware or channel-unaware techniques.     

Traffic and Interference Adaptive Scheduling for Internet Traffic in UMTS

In this paper we propose a scheduling strategy for the radio resources management when transmitting Internet traffic over third-generation systems. More precisely, we consider the UMTS Terrestrial Radio Access Network (UTRAN) Time Division Duplex (TDD) mode standardized by ETSI. UTRAN TDD uses a hybrid solution of code and time division multiple access, called TD-CDMA. In UMTS systems a key issue in developing access methodologies for the available spectrum is an optimal management of the rare radio resources. In this paper we present a fair and efficient scheduling algorithm that adapts its behavior to traffic and interference conditions. Specifically, our scheduling algorithm is able to manage the radio resources taking into account both the traffic fluctuations in the uplink and downlink direction and the variations of the system interference. The goal of our scheduler is the data-throughput maximization for an efficient utilization of available radio resources. The effectiveness of our scheduling algorithm is shown by exploiting analytical tools.     

Efficient radio resource management for wireless multimedia communications: a multidimensional QoS-based packet scheduler

Future wireless multimedia systems will support a variety of services with diverse range of capabilities and bit rates. For these systems, it is highly desired for real-time conversational and non-real-time services to efficiently share the available channels and bandwidth in an optimized way. The partitioned resource shaping with either fixed or a slow changing dynamic, proposed for conventional packet scheduling techniques, proves difficult and inefficient under fast-changing dynamics of radio channel and traffic. By taking into account almost all the aspects (dimensions) of quality-of-service (QoS) provisioning, the proposed unified fast dynamic multidimensional QoS-based packet scheduler (MQPS) in this paper elegantly and efficiently encapsulates features of many possible packet scheduling strategies. MQPS applies an optimization and tuning mechanism to packet scheduling weights to adopt the most appropriate packet scheduling and channel assignment strategy in response to the varying traffic and radio channel conditions. As an example, the technique is applied to a high-speed downlink packet access (HSDPA) system. It is shown that MQPS provides significantly better performance than existing techniques by satisfying all the requirements of a successful QoS provisioning to maximum possible level simultaneously.     

基于满意度准则采用混合波束成型预编码的调度方法

为了满足未来无线宽带网络中多种服务质量(QoS)要求业务并存的需求,该文提出一种多天线下行系统中结合混合波束成型预编码技术基于满意度的调度方法。该调度方法联合考虑用户的QoS要求及其信道质量,灵活地使用随机波束成型和迫零波束成型预编码技术,并通过惩罚机制避免特定用户占用超出其需求的带宽,更有效地为用户分配令其满意的资源,使各种QoS要求的用户获得满意的服务。仿真结果证明,与现有的方法相比,该文提出的方法在保证用户服务质量的同时,能更好地利用系统资源。     

ORCA-MRT: an optimization-based approach for fair scheduling in multirate TDMA wireless networks

This paper presents an optimization-based approach to solve the wireless fair scheduling problem under a multirate time division multiple access (TDMA)-based medium access control (MAC) framework. By formulating the fair scheduling problem as an assignment problem, the authors propose the optimal radio channel allocation for multirate transmission (ORCA-MRT) algorithm for fair bandwidth allocation in wireless data networks that support MRT at the radio link level. The key feature of ORCA-MRT is that while allocating transmission rate to each flow fairly, it keeps the interaccess delay bounded under a certain limit. The authors investigate the performance of the proposed ORCA-MRT scheduler in comparison to another recently proposed multirate fair scheduling algorithm. They also propose two channel prediction models and perform extensive simulations to investigate the performance of ORCA-MRT for different system parameters such as channel state correlation, number of flows, etc.     

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.     

Cross-layer scheduling strategy for UMTS downlink enhancement

This article describes the benefits of including cross-layer information in the scheduling mechanism of a UMTS downlink channel. In particular, the information obtained from the fast power control algorithm is used to properly schedule transmissions. A prioritization function that exploits the short-term channel variations is proposed. This strategy is shown to be a feasible approach to improve system performance in terms of capacity and delay. This enhancement is obtained as a benefit of intrinsic multi-user diversity. The proposal is applicable within the current UMTS radio resource management framework.     

Multi-user Fair Scheduling in the Downlink of CDMA Packet Systems

A fair scheduling algorithm is proposed to improve the system throughput while maintaining the fairness in the downlink of a code-division multiple access (CDMA) system employing AMC and multicodes. R. Kwan and C. Leung suggested an optimal scheduling to maximize the total throughput based on simultaneous transmissions strategy. In this letter, we extend the optimal scheduling so that some degree of fairness can be maintained. We formulate a mixed-integer nonlinear programming problem to assign the radio resources such as the transmit power and codes to several users effectively. The result shows that the proposed algorithm provides a significant throughput gain over PF scheduling with one-by-one transmission at the same level of fairness     

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.     

GPRS中分组调度算法

主要讨论通用无线分组业务（GPRS）调度算法。首先介绍了一些常用分组调度算法，给出了GPRS中服务质量（QoS)定义和GPRS中选择分组调度算法原则，并根据对GPRS特性和三种算法性能的分析与比较，提出了一种新的基于延迟约束分组调度算法。通过仿真发现，新算法可在满足延迟要求基础上以较小复杂度获得比其余算法更高的资源利用率。     

Provisioning multimedia wireless networks for better QoS: RRM strategies for 3G W-CDMA

Third-generation mobile communication systems will bring a wide range of new services with different quality of service requirements and will open the ability to exploit radio resource management functions to guarantee a certain target QoS, to maintain the planned coverage area and to offer a high-capacity while using the radio resources in an efficient way. RRM functions impact the overall system efficiency and the operator infrastructure cost, so they will definitively play an important role in a mature 3G scenario. In order to provide some insight into radio resource management (RRM) strategies implementation, a range of representative case-studies with several innovative algorithms are presented and supported by simulation results in a realistic UMTS Terrestrial Radio Access Network scenario as devised in the 3GGP standardization forum. In particular, a decentralized uplink transmission rate selection algorithm in the short term, a congestion control mechanism to cope with overload situations, and downlink scheduling for layered streaming video packets are proposed.     

An on-line learning algorithm for energy efficient delay constrained scheduling over a fading channel

In this paper, we consider the problem of energy efficient scheduling under average delay constraint for a single user fading channel. We propose a new approach for on-line implementation of the optimal packet scheduling algorithm. This approach is based on reformulating the value iteration equation by introducing a virtual state called post-decision state. The resultant value iteration equation becomes amenable to online implementation based on stochastic approximation. This approach has an advantage that an explicit knowledge of the probability distribution of the channel state as well as the arrivals is not required for the implementation. We prove that the on-line algorithm indeed converges to the optimal policy.     

Radio Link Buffer Management and Scheduling for Wireless Video Streaming

In this paper we compare strategies for joint radio link buffer management and scheduling for wireless video streaming. Based on previous work in this area [8], we search for an optimal combination of scheduler and drop strategy for different end-to-end streaming options including timestamp-based streaming and ahead-of-time streaming, both with variable initial playout delay. We will show that a performance gain versus the two best drop strategies in Liebl et al. [8], i.e. drop the HOL packet or drop the packet with the lowest priority starting from HOL, is possible: Provided that some basic side-information on the structure of the incoming video stream is available, a more sophisticated drop strategy removes packets from an HOL group of packets in such a way that the temporal dependencies usually present in video streams are not violated. This advanced buffer management scheme yields significant improvements for almost all investigated scheduling algorithms and streaming options. In addition, we will demonstrate the importance of fairness among users when selecting a suitable scheduler, especially if ahead-of-time streaming is to be applied: Given a reasonable initial playout delay at the streaming media client, both the overall achievable quality averaged over all users, as well as the individual quality of users with bad channel conditions can be increased significantly by trading off fairness with maximum throughput of the system.     

Scheduling and power control for MAC layer design in multihop IR‐UWB networks

Recently, a number of researchers have proposed media access control (MAC) designs for ultra‐wideband (UWB) networks. Among them, designs based on scheduling and power control seem to be of great promise, particularly for quality‐of‐service (QoS) traffic. We investigate the efficiencies of many different choices for scheduling and power allocation for QoS traffic in a multihop impulse radio (IR)‐UWB network, with the objective of achieving both high spectral efficiency and low transmission power. Specifically, we compare different scheduling schemes employing a protocol interference‐based contention graph as well as a physical interference‐based contention graph. We propose a relative distance to determine adjacency in the protocol interference‐based contention graph. Using our improved protocol interference model with graph‐based scheduling, we obtained better performance than the physical interference‐based approach employing link‐by‐link scheduling. Copyright © 2009 John Wiley & Sons, Ltd.     

An optimization approach to the synthesis of multichiparchitectures

An optimization approach to the high level synthesis of VLSI multichip architectures is presented in this paper. This research is important for industry since it is well known that these early high level decisions have the greatest impact on the final VLSI implementation. Optimal application-specific architectures are synthesized here to minimize latency given constraints on chip area, I/O pin count and interchip communication delays. A mathematical integer programming (IP) model for simultaneously partitioning, scheduling, and allocating hardware (functional units, I/O pins, and interchip busses) is formulated. By exploiting the problem structure, using polyhedral theory, the size of the search space is decreased and a new variable selection strategy is introduced based on the branch and bound algorithm. Multichip optimal architectures for several examples are synthesized in practical cpu times. Execution times are comparable to previous heuristic approaches, however there are significant improvements in optimal schedules and allocations of multichips. This research breaks new ground by 1) simultaneously partitioning, scheduling, and allocating in practical cpu times, 2) guaranteeing globally optimal architectures for multichip systems for a specific objective function, and 3) supporting interchip communication delay, interchip bus allocation, and other complex interface constraints     

A Noise-Robust Convex-Optimized Positioning System Based on Code-Aided RSS Estimation and Virtual Base Station Transform

Parallelization of Digital Signal Processing (DSP) software is an important trend in Multiprocessor System-on-Chip (MPSoC) implementation. The performance of DSP systems composed of parallelized computations depends on the scheduling technique, which must in general allocate computation and communication resources for competing tasks, and ensure that data dependencies are satisfied. In this paper, we formulate a new type of parallel task scheduling problem called Parallel Actor Scheduling (PAS) for MPSoC mapping of DSP systems that are represented as Synchronous Dataflow (SDF) graphs. In contrast to traditional SDF-based scheduling techniques, which focus on exploiting graph level (inter-actor) parallelism, the PAS problem targets the integrated exploitation of both intra- and inter-actor parallelism for platforms in which individual actors can be parallelized across multiple processing units. We first address a special case of the PAS problem in which all of the actors in the DSP application or subsystem being optimized are parallel actors (i.e., they can be parallelized to exploit multiple cores). For this special case, we develop and experimentally evaluate a two-phase scheduling framework with three work flows that involve particle swarm optimization (PSO) — PSO with a mixed integer programming formulation, PSO with simulated annealing, and PSO with a fast heuristic based on list scheduling. Then, we extend our scheduling framework to support the general PAS problem, which considers both parallel actors and sequential actors (actors that cannot be parallelized) in an integrated manner. We demonstrate that our PAS-targeted scheduling framework provides a useful range of trade-offs between synthesis time requirements and the quality of the derived solutions. We also demonstrate the performance of our scheduling framework from two aspects: simulations on a diverse set of randomly generated SDF graphs, and implementations of an image processing application and a software defined radio benchmark on a state-of-the-art multicore DSP platform.     

Uplink power control for TDMA portable radio channels

Power control based on signal-to-interference ratio (SIR) has been proposed as a technique for managing co-channel interference in frequency reuse radio systems. Recently, new autonomous power control methods were introduced to achieve near-optimum performance without difficult centralized control proposed earlier. The achievable performance from preliminary studies appears promising for providing significant increase in spectrum efficiency. However, the implementation of the SIR-based power control algorithms remains challenging. In this paper, implementation of power control that indirectly depends on SIR is discussed. As an example, a simple closed-loop power control algorithm for the portable transmitter is introduced for TDMA portable radio systems. While it may appear specific for the system considered, the underlying principle and parameters required (i.e., error indicator, received power level, and signal quality indicator) are common to the implementation of digital demodulation circuitry. Computer simulations indicate that SIR level is maintained at a level suitable for sustaining desirable performance. Furthermore, when the power-control updating period is short, as in the specific system considered, moderate-rate short-term fading can be tracked and mitigated