QoS aware adaptive resource allocation techniques for fair scheduling in OFDMA based broadband wireless access systems

A system based on orthogonal frequency division multiple access (OFDMA) has been developed to deliver mobile broadband data service at data rates comparable to those of wired services, such as DSL and cable modems. We consider the resource allocation problem of assigning a set of subcarriers and determining the number of bits to be transmitted for each subcarrier in OFDMA systems. We compare simplicity, fairness and efficiency of our algorithm with the optimal and proposed suboptimal algorithms for varying values of delay spread, number of users and total power constraint. The results show that the performance of our approach is appealing and can be close to optimal. We also consider another resource allocation scheme in which there is no fixed QoS requirements per symbol but capacity is maximized.     

System utility based resource allocation for multi-cell OFDM system

Utility based resource allocation strategy in multi-cell orthogonal frequency-division multiplexing (OFDM) system plays a critical role in next generation mobile communication systems. Based on the analysis of risk aversion utility functions, this article proposed the system utility based utility, which is named the customer satisfaction (CS) utility. Compared with the proportional fairness (PF) utility, the CS utility reflects the user demands better, and enables the system to adjust its resource allocation according to both the traffic requirements and the resource situation.     

一种基于比例公平的多跳OFDMA系统资源分配算法

为解决多跳OFDMA系统的资源分配问题,本文提出一种基于比例公平的资源分配算法,该算法将一个联合优化的问题分解为两个步骤,首先在等功率分配的条件下求出最优的子载波分配以及中继节点选择方案,然后再根据注水定理进行功率分配,以提高系统的性能.仿真结果表明,该算法能够在保障不同用户间公平性的条件下,有效地提高系统的容量.     

Proportional QoS adjustment for achieving feasible power allocation in CDMA systems

Resource management is the general topic of the present paper, particularly, we deal with capacity sharing for interference limited wireless networks by power control. Proportional reduction of the signal-to-interference ratio (SIR) requirements is suggested as the control mechanism to accommodate users in the case of overload. For this purpose, we carefully describe the geometrical structure and the asymptotic behavior of the set of feasible power vectors as a proportionality factor tends to its boundaries. In the case that there is no feasible power adjustment, the minimum proportional SIR reduction is determined under general power constraints. We conclude with developing a locally quadratic convergent algorithm for numerical computation of the optimum power assignment. The investigations provide both insight into the theoretical structure of optimum power allocation as well as a practical method for call admission control.     

Location-based QoS enhanced dynamic carrier allocation over multi-cell environments

It is well known that high multi-user and multi-carrier diversity gains can be achieved via the use of DCA (Dynamic Channel Allocation). However, there is no framework for analyzing the system performance of DCA algorithms over multi-cell environments. This paper presents a numerical analysis for measuring the performance gain for various DCA algorithms. Based on the analysis, an LQE (Location-based QoS Enhanced) DCA algorithm is proposed, in which a higher priority is assigned to users in the outer region for fairness by exploiting multi-carrier diversity. In the inner region, each carrier is allocated to a user with the best channel gain for higher throughput by exploiting multi-user diversity. In the simulation, we demonstrate that the proposed DCA algorithm is very effective from the perspective of fairness and throughput.     

A multi-cell graph based dynamic resource allocation scheme for multi-user wireless networks

Dynamic resource allocation being a computationally difficult problem, static spectrum management is more commonly used in large-scale networks. The combination of virtualization technologies, where powerful centralized allocation algorithms can be implemented, and recent advances in graph coloring algorithms prompts the revisiting of this view. We describe a new graph based framework to maximize the number of simultaneously communicating mobiles in a wireless network. Since the considered problem is NP-hard, we propose various heuristic algorithms and analyze their performance, in comparison with standard decentralized channel assignment strategies such as Fractional Frequency Reuse (FFR). We consider the LTE uplink and downlink with the WINNER channel as the reference model. We show that for blocking probabilities below 2%, our scheme typically increases the number of mobile users by 25%. For example with 25 base stations and 120 channels, running the resource allocation scheme takes one second on a PC and permits to increase the number of mobiles requiring one single channel each from 750 to 950, a 25% increase in efficiency compared to FFR.     

基于共享资源量的动态多资源公平分配策略

针对云计算共享系统中多资源分配问题,提出一种基于共享资源量的动态多资源公平分配策略。该策略根据不同用户资源需求和共享资源量建立一个线性规划模型,同时证明该模型满足公平分配的4个重要属性：动态帕累托最优、激励共享、动态无嫉妒性和防止策略性操作,而且给出一种改进的动态多资源公平分配算法来提高算法运行效率。实验结果表明,所提动态多资源公平分配策略能够在满足任务资源需求的同时,尽可能保证公平分配下最大化占优资源份额,并且改进的分配算法能够有效地提高资源的分配效率。     

基于博弈论的多小区OFDMA系统资源分配

立足于限制条件下实现多小区OFDMA系统容量最大或总传输功率最小的优化问题,比较分析了近年来提出的多种基于博弈论的资源分配算法。分析了纳什均衡点存在和唯一的条件,通过引入定价机制或虚拟裁判机制,使得到的解收敛于纳什均衡点。最后,探讨了联合中继节点或MIMO技术的多小区OFDMA系统资源分配算法,该算法能有效提高频谱效率,将成为未来研究的热点。     

Fair resource allocation with guaranteed statistical QoS for multimedia traffic in wideband CDMA cellular network

A dynamic fair resource allocation scheme is proposed to efficiently support real-time and non-real-time multimedia traffic with guaranteed statistical quality of service (QoS) in the uplink of a wideband code-division multiple access (CDMA) cellular network. The scheme uses the generalized processor sharing (GPS) fair service discipline to allocate uplink channel-resources, taking into account the characteristics of channel fading and intercell interference. In specific, the resource allocated to each traffic flow is proportional to an assigned weighting factor. For real-time traffic, the assigned weighting factor is a constant in order to guarantee the traffic statistical delay bound requirement; for non-real-time traffic, the assigned weighting factor can be adjusted dynamically according to fading, channel states and the traffic statistical fairness bound requirement. Compared with the conventional static-weight scheme, the proposed dynamic-weight scheme achieves capacity gain. A flexible trade-off between the GPS fairness and efficient resource utilization can also be achieved. Analysis and simulation results demonstrate that the proposed scheme enhances radio resource utilization and guarantees statistical QoS under different fairness bound requirements.     

Distributed resource allocation for rate-constrained users in multi-cell OFDMA networks

This letter addresses resource allocation in multi-cell OFDMA networks. It describes a heuristic for distributed sum power minimization under target data rate requirements. The proposed method establishes a set of target SINR per user and subcarrier, determined to reach the target data rate of each user, while avoiding power divergence situations. Power control can then be performed independently over each subcarrier. Compared to iterative water-filling, this method proves to be very efficient at any load in terms of resource consumption and users' rejection.     

Optimal resource allocation in multiservice CDMA networks

This paper addresses the problem of dynamic resource allocation in a multiservice direct-sequence code-division multiple-access (DS-CDMA) wireless network supporting real-time (RT) and nonreal-time (NRT) communication services. For RT users, a simple transmission power allocation strategy is assumed that maximizes the amount of capacity available to NRT users without violating quality of service requirements of RT users. For NRT users, a joint transmission power and spreading gain (transmission rate) allocation strategy, obtained via the solution of a constrained optimization problem, is provided. The solution maximizes the aggregate NRT throughput, subject to peak transmission power constraints and the capacity constraint imposed by RT users. The optimization problem is solved in a closed form, and the resulting resource allocation strategy is simple to implement as a hybrid CDMA/time-division multiple-access strategy. Numerical results are presented showing that the optimal resource allocation strategy can offer substantial performance gains over other conventional resource allocation strategies for DS-CDMA networks.     

基于 QoS 保障的密集 WLAN 多维资源分配算法

针对密集无线局域网覆盖环境,以提升网络性能为目标,提出了一种多维无线资源分配方法。通过网络覆盖衡量参数、干扰衡量参数和QoS衡量参数联合评估网络性能,建立了网络性能与资源分配向量之间的优化目标函数,进而采用禁忌搜索的方法求解目标函数后得到最优多维资源分配向量,包括所用AP、信道和功率分配向量。仿真结果表明,所提算法提升了网络性能,更好地保证了用户QoS需求。     

Effect of channel estimation errors in TD/CDMA systems employingjoint detection

Hybrid TD/CDMA systems are being considered for third generation wireless systems TDD components. An evaluation is presented of the impact of channel estimation errors on the performance of TD/CDMA systems employing joint detection. It is verified that such errors cause a significant degradation in bit error rate     

Power distribution/allocation in multirate wideband CDMA systems

A unified approach for power distribution and allocation in a multirate wideband CDMA system is investigated. It is shown that the traffic demand and the background disturbance fully govern the feasibility of the system and the optimal power distribution solutions, where the traffic demand is specified by the user QoS requirement, data rate, and spread spectrum bandwidth; the background disturbance includes the background noise and the intercell interference. Closed form expressions of the optimal power allocation, subject to power constraints in the practical system design, are derived. Convergent conditions are applied to evaluate the capacity region of the system. Numerical examples are provided to illustrate the applications of the obtained theoretical results.     

Virtual partitioning resource allocation for multiclass traffic in cellular systems with QoS constraints

Resource allocation is a vital component of call-admission control that determines the amount of resource to assign to new and handoff connections for quality-of-service (QoS) satisfaction. In this paper, we present approximate analytical formulations of virtual partitioning resource-allocation schemes for handling multiclass services with guard channels in a cellular system. Resource-allocation models for best effort and guarantee access with preemption for best effort traffic and virtual partition with preemption for all classes are investigated. The analytical models, derived using a K-dimensional Markov chain, are solved using preemption rules for these schemes. Call-level grade of service, such as new-call-blocking probability, handoff-call-blocking probability, and system utilization, and packet-level QoS, such as packet-loss probability, are used as performance metrics. The performances of fast and slow mobile users are evaluated analytically and by simulation. The analytical and simulation results show excellent agreement. A method to maximize system utilization through joint optimization of call-/packet-level parameters is proposed. Numerical results indicate that significant gain in system utilization is achieved.     

多小区边缘用户集中式资源分配策略

针对传统频率复用方案无法适应小区边缘负载变化的问题,提出一种多小区边缘用户集中式调度策略,可以在避免产生干扰的同时动态适应每个小区的负载分布情况,并结合一种基于匈牙利算法的资源分配算法来保证用户的速率要求和系统吞吐量。仿真证明,该方案相较其他方案在用户满意度和吞吐量上都有较大的提升。     

多蜂窝上行链路通信系统性能分析

考虑存在来自其他蜂窝的不同功率同信道干扰的多用户上行链路,分析了多天线基站采用多用户调度和最大比合并接收时的系统性能。在期望信号和干扰信号分别经历Nakgami-m和Rayleigh衰落时,运用基于概率密度函数的性能分析法推导了系统中断概率的闭合表达式。仿真结论显示,系统中断概率的解析曲线与数值仿真结果一致,系统性能随着天线数和用户数的增大而提升,多天线和多用户分集增益明显,干扰功率有较大差异时系统中断概率性能有所下降。     

A resource allocation strategy for distributed MIMO multi-hop communication systems

An extended form of multi-hop communication systems is introduced which allows the application of multiple-input-multiple-output (MIMO) capacity enhancement techniques over spatially separated relaying mobile terminals to drastically increase end-to-end capacity. An explicit resource allocation strategy is deduced in terms of fractional bandwidth and power allocations to each relaying hop over ergodic Rayleigh flat fading channels employing orthogonal frequency-division multiple-access (FDMA)-based relaying.     

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.