Wireless Packet Scheduling Algorithm Research Articles

A performance evaluation framework for packet scheduling algorithms in wireless system

SUMMARYThe question of how to evaluate wireless packet scheduling algorithms with a comprehensive consideration of different performance metrics is investigated in this paper. By studying the intrinsic relationship between system throughput and fairness, a performance evaluation problem for packet scheduling algorithms in a wireless system is formulated. Through the use of nonlinear programming method, the performance evaluation framework for weighted‐type packet scheduling algorithms can be established. The performances of some typical packet scheduling algorithms for multiuser wireless communications are also evaluated in this framework as examples. Copyright © 2011 John Wiley & Sons, Ltd.

A Low-Complexity QoS-Aware Proportional Fair Multicarrier Scheduling Algorithm for OFDM Systems

Orthogonal frequency-division multiplexing (OFDM) systems are the major cellular platforms for supporting ubiquitous high-speed mobile applications. However, a number of research challenges remain to be tackled. One of the most important challenges is the design of a judicious packet scheduler that will make efficient use of the spectrum bandwidth. Due to the multicarrier nature of the OFDM systems, the applicability and performance of traditional wireless packet-scheduling algorithms, which are usually designed for single-carrier systems, are largely unknown. In th.is paper, we propose a new quality-of-service (QoS)-aware proportional fairness (QPF) packet-scheduling policy with low complexity for the downlink of multiuser OFDM systems to allocate radio resources among users. Our proposed algorithm is based on a cross-layer design in that the scheduler is aware of both the channel (i.e., physical layer) and the queue state (i.e., data link layer) information to achieve proportional fairness while maximizing each user's packet-level QoS performance. The simulation results show that the proposed QPF algorithm is efficient in terms of average system throughput, packet-dropping probability, and packet delay, while maintaining adequate fairness among users with relatively low scheduling overhead.

Bandwidth-Guaranteed Fair Scheduling with Effective Excess Bandwidth Allocation for Wireless Networks

Traffic scheduling is key to the provision of quality of service (QoS) differentiation and guarantees in wireless networks. Unlike its wireline counterpart, wireless communications pose special channel-specific problems such as time-varying link capacities and location-dependent errors. These problems make designing efficient and effective traffic scheduling algorithms for wireless networks very challenging. Although many wireless packet scheduling algorithms have been proposed in recent years, issues such as how to improve bandwidth efficiency and maintain goodput fairness with various link qualities for power-constrained mobile hosts remain unresolved. In this paper, we devise a simple wireless packet scheduling algorithm called bandwidth-guaranteed fair scheduling with effective excess bandwidth allocation (BGFS-EBA), which addresses these issues. Our studies reveal that BGFS-EBA effectively distributes excess bandwidth, strikes a balance between effort-fair and outcome- fair, and provides a delay bound for error-free flows and transmission effort guarantees for error-prone flows.

Temporal fairness guarantee in multi-rate wireless LANs for per-flow protection

Wireless LAN technologies such as IEEE 802.11a and 802.11b support high bandwidth and multi-rate data transmission to match the channel condition (i.e., signal to noise ratio). While some wireless packet fair queuing algorithms to achieve the per-flow throughput fairness have been proposed, they are not appropriate for guaranteeing QoS in multi-rate wireless LAN environments. We propose a wireless packet scheduling algorithm that uses the multistate (multi-rate) wireless channel model and performs packet scheduling by taking into account the channel usage time of each flow. The proposed algorithm aims at per-flow protection by providing equal channel usage time for each flow. To achieve the per-flow protection, we propose a temporally fair scheduling algorithm called Contention-Aware Temporally fair Scheduling (CATS) which provides equal channel usage time for each flow. Channel usage time is defined as the sum of the packet transmission time and the contention overhead time due to the CSMA/CA mechanism. The CATS algorithm provides per-flow protection in wireless LAN environments where the channel qualities of mobile stations are dynamic over time, and where the packet sizes are application-dependent. We also extend CATS to Decentralized-CATS (D-CATS) to provide per-flow protection in the uplink transmission. Using an NS-2 simulation, we evaluate the fairness property of both CATS and D-CATS in various scenarios. Simulation results show that the throughput of mobile stations with stable link conditions is not degraded by the mobility (or link instability) of other stations or by packet size variations. D-CATS also shows less delay and less delay jitter than FIFO. In addition, since D-CATS can coordinate the number of contending mobile stations, the overall throughput is not degraded as the number of mobile stations increases.

Wireless Packet Scheduling Algorithm for OFDMA System based on Time-utility and Channel State

In this paper, we propose an urgency- and efficiencybased wireless packet scheduling (UEPS) algorithm that is able to schedule real-time (RT) and non-real-time (NRT) traffics at the same time while supporting multiple users simultaneously at any given scheduling time instant. The UEPS algorithm is designed to support wireless downlink packet scheduling in an orthogonal frequency division multiple access (OFDMA) system, which is a strong candidate as a wireless access method for the next generation of wireless communications. The UEPS algorithm uses the time-utility function as a scheduling urgency factor and the relative status of the current channel to the average channel status as an efficiency indicator of radio resource usage. The design goal of the UEPS algorithm is to maximize throughput of NRT traffics while satisfying quality-of-service (QoS) requirements of RT traffics. The simulation study shows that the UEPS algorithm is able to give better throughput performance than existing wireless packet scheduling algorithms such as proportional fair (PF) and modifiedlargest weighted delay first (M-LWDF), while satisfying the QoS requirements of RT traffics such as average delay and packet loss rate under various traffic loads.

WFI optimized PWGPS for wireless IP networks

The worst-case fairness index (WFI) has proved to be an important metric in the provision of fairness and bounded delay in both wired and wireless networks. A feature of wireless links is location dependent burst errors that result in degraded WFI. This paper firstly analyzes the provision for WFI with existing wireless packet scheduling techniques, and based on this, a WFI optimized Packetized Wireless Generalized Processor Sharing (PWGPS) is proposed. This wireless packet scheduling algorithm aims to improve the accuracy of traditional PWGPS and reduce the WFI for real time traffic in wireless IP networks system. The detailed algorithm and simulation results are given. Analysis and simulations show that the WFI optimized PWGPS proposed can improve the WFI for real time flow while at the same time maintain low complexity.

A distributed fair scheduling scheme in wireless LAN

This paper proposes an algorithm named WLFVC, which is a fully distributed wireless packet scheduling algorithm based on LFVC (Leap Forward Virtual Clock), to provide streams with fairness, especially in the short time scale. This algorithm is able to allocate bandwidth to streams proportional to their weights. Thus, better delay and jitter performance can be achieved. Since collisions and wireless link error degrade the performance of MAC protocols in the WLAN environment, WLFVC also takes them into consideration. Finally, this algorithm works in a fully distributed way and it can coexist with other stations that only support DCF (Distributed Coordination Function).