粒子群优化的时频联合资源分配算法

针对航空通信环境中正交频分多址系统的资源分配问题,在信道资源有限的约束条件下,以最大化用户节点的效用总和为目标,提出了一种基于粒子群优化(PSO)的时频联合资源分配算法.该算法采用离散变量来编码粒子位置,并针对离散空间构建新的基于概率信息的粒子速度和位置更新算法.仿真结果表明:所提出的资源分配算法在效用总和、公平性等方面优于现有资源分配算法.     

Scheduling algorithms for multicast traffic in TDM/WDM networks with arbitrary tuning latencies

We consider all-optical Time Division Multiplexing (TDM)/Wavelength Division Multiplexing (WDM) broadcast and select networks with slotted operation. Each network access node is equipped with one fixed transmitter and one tunable receiver; tuning times are not negligible with respect to the fixed size slot time. We discuss efficient scheduling algorithms to assign TDM/WDM slots to multicast traffic in such networks. The problem is shown to be NP-hard; thus, heuristic algorithms based on the Tabu Search meta-heuristic are proposed, and their performance are assessed using randomly created request matrices based on two types of multicast traffic patterns. We show that significant advantages can be obtained by using these novel algorithms with respect to simpler greedy algorithms, even when restricting CPU times to realistic values to make the algorithms of practical use.     

Multi-hop multicast path construction in modern wireless relay networks

In recent years, multicast over wireless access networks has become a popular research topic. However, if relay nodes are supported in such a network, forming an efficient multicast topology becomes a challenging task. Since existing works fail to solve this problem satisfyingly, we in this paper propose a multi-hop multicast routing scheme for modern wireless relay networks. First, we formulate this important problem as Multi-Hop Multicast Maximization (MHMM), which involves forming a resource allocation of the base-station and relay stations in order to maximize the number of recipients with the given resource budget and channel conditions. To solve MHMM, we propose a heuristic called Multi-Hop Path Selection (MHPS). We prove that MHMM is NP-complete, and also analyze MHPS’s computational complexity and its worst-case performance. The results of simulations conducted to evaluate the heuristic’s performance demonstrate that, under variant conditions, MHPS utilizes bandwidth resources and relay nodes effectively such that it significantly outperforms all existing approaches. Moreover, its performance difference to the optimum is bounded. To the best of our knowledge, MHPS is the only scheme that focuses on this important issue and achieves such a satisfactory performance.     

基于非合作博弈的OFDMA-WLAN系统资源分配算法研究

为满足无线局域网中基于正交频分多址技术(OFDMA-WLAN)的多用户通信需求,提出了一种基于非合作博弈的资源分配策略,利用博弈论这一有效工具对无线网络服务质量的资源分配问题进行研究,同时将用户对信道质量的不同需求转化为多用户对不同信道资源分配的非合作博弈竞争问题。此外,还将纳什均衡问题(NEP)细分为数个变分不等式子问题,通过凸优化函数对这些子问题分别求解。数值分析结果表明,所提算法在资源分配的公平性和数据传输率方面达到了更好的折中。     

A novel radio resource allocation scheme for IEEE 802.16e multicell networks

In this paper,we propose a new media access control (MAC) protocol,which is compatible with the IEEE 802.16e-2005 Orthogonal Frequency Division Multiple Access (OFDMA) wireless interface.In this protocol,the same radio resource can be shared by neighboring cells in the wireless mesh network (WMN) and collisions can be reduced in the overlapping areas.This protocol consists of two schemes: a downlink transmission and an uplink transmission.For downlink transmission we use a cross layer adaptive radio resourc...     

An optimal scheduling algorithm for an agent-based multicast strategy on irregular networks

This paper describes an agent-based approach for scheduling multiple multicast on wormhole switch-based networks with irregular topologies. Multicast/broadcast is an important communication pattern, with applications in collective communication operations such as barrier synchronization and global combining. Our approach assigns an agent to each subtree of switches such that the agents can exchange information efficiently and independently. The entire multicast problem is then recursively solved with each agent sending message to those switches that it is responsible for. In this way, communication is localized by the assignment of agents to subtrees. This idea can be easily generalized to multiple multicast since the order of message passing among agents can be interleaved for different multicasts. The key to the performance of this agent-based approach is the message-passing scheduling between agents and the destination processors. We propose an optimal scheduling algorithm, called ForwardInSwitch to solve this problem. We conduct extensive experiments to demonstrate the efficiency of our approach by comparing our results with SPCCO, a highly efficient multicast algorithm reported in literature. We found that SPCCO suffers link contention when the number of simultaneous multiple multicast becomes large. On the other hand, our agent-based approach achieves better performance in large cases.     

OFDMA无线mesh网中公平资源分配算法

为了兼顾用户间公平性的同时最大化总的端到端速率,并克服现有分配算法在实际中难以实现的缺点,提出了一种新的分级资源分配算法.该算法首先根据有限的信息基于纳什议价解(NBS)进行粗分配(CA);其次根据完整的子载波增益信息排序方法进行细分配(FA).仿真结果表明,该算法不仅获得与基于最大速率准则的算法相近的总的端到端速率,而且保证了用户间的公平性;同时,该算法能以更低的复杂度获得与现有算法相近的端到端速率.     

Resource allocation by genetic algorithm with fuzzy inference

Assuming that a make-to-order manufacturing company has customer orders, the addressed capacity allocation problem is a due-date assignment problem for multiple manufacturing resources. The purpose of this study is to develop an intelligent resource allocation model using genetic algorithm and fuzzy inference for reducing lateness of orders with specific due dates. While the genetic algorithm is responsible for arranging and selecting the sequence of orders, the fuzzy inference module conveys how resources are allocated to each order. Experimental results showed that the proposed model has solved the capacity allocation problem efficiently.     

Power allocation for OFDM-based cognitive heterogeneous networks

In this paper,the capacity maximization and the spectrum utilization efficiency improvement are investigated for the Pico cells in broadband heterogeneous networks.In frequency-reuse model,the users attached to Macro base station are usually viewed as primary users,and those attached to Pico base station should be regarded as cognitive radio(CR) users.As both the primary users and the CR users communicate in parallel frequency bands,the performance of the system is limited by the mutual inter-carrier interference(ICI).In order to control ICI and maximize the achievable transmission rate of the CR users,an effective power allocation scheme is proposed to maximize the transmission rate of the CR users under a given interference threshold prescribed by the primary users.By transforming this suboptimal solution into an innovative matrix expression,the algorithm is easier to perform in practice.The simulation results demonstrate that the proposed algorithm provides a large performance gain in Pico cell capacity over the non-cooperative and equal power allocation schemes.     

Efficient resource allocation scheme for multi-service based on interference mitigation in LTE-Advanced networks

The exponential growth of various services demands the increased capacity of the next-generation broadband wireless access networks, which is toward the deployment of femtocell in macrocell network based on orthogonal frequency division multiple access. However, serious time-varying interference obstructs this macro/femto overlaid network to realize its true potential. In this article, we present a macro services guaranteed resource allocation scheme, which can mitigate various dominant interferences and provide multiple services in macro/femto overlaid Third-Generation Partnership Project Long Term Evolution-Advanced networks. We model our multiple services resource allocation scheme into a multiobjective optimization problem, which is a non-deterministic polynomial-time （NP）-hard problem. Then, we give a low-complexity algorithm consisting of two layers based on chordal graph. Simulation results verify that the proposed scheme can achieve better efficiency than the previous works and raise the satisfaction ratio of Guaranteed Bit Rate （GBR） services while improving the average performance of non-GBR services.     

OFDMA系统功率控制技术研究及改进算法*

在分析现有功率控制算法的基础上,针对基于路损功率补偿算法中存在的系统吞吐量和小区干扰水平互为矛盾的问题,提出了一种基于差分路损补偿功率控制的改进算法。通过数值仿真证明,该算法具有更好的提高系统吞吐量和降低小区干扰水平的优点,能够使两者达到最佳折中,从而对于提高频谱效率具有更强的性能,并且该方法简单、可操作性强,具有一定的实现价值。     

Performance analysis of a threshold based distributed channel allocation algorithm for cellular networks

Rapid advances of the handheld devices and the emergence of the demanding wireless applications require the cellular networks to support the demanding user needs more effectively. The cellular networks are expected to provide these services under a limited bandwidth. Efficient management of the wireless channels by effective channel allocation algorithms is crucial for the performance of any cellular system. To provide a better channel usage performance, dynamic channel allocation schemes have been proposed. Among these schemes, distributed dynamic channel allocation approaches showed good performance results. The two important issues that must be carefully addressed in such algorithms are the efficient co-channel interference avoidance and messaging overhead reduction. In this paper, we focus on our new distributed channel allocation algorithm and evaluate its performance through extensive simulation studies. The performance evaluation results obtained under different traffic load and user mobility conditions, show that the proposed algorithm outperforms other algorithms recently proposed in the literature.     

Design and Analysis of a Backbone Architecture with TDMA Mechanism for IP Optical Networking

This paper presents a new technique for constructing IP over photonic systems. The use of lable switching is assumed in the IP routers, while a new routing architecture is introduced to transport IP packets across an optical backbone network. The architecture is based on a two-level TDMA structure with wavelength division multiplexing (WDM). Many IP-based network applications such as high-resolution image, distributed database, and real-time video/audio service generally require high-speed transmissions in WAN/LAN. The network traffic in these applications usually exhibits traffic locality. As a result, traditional TDMA is not efficient for such traffic. Consequently, based on the traffic parameters such as locality and loading, an architecture named a PG (Partition-Group) Network is proposed. Furthermore, the interleaved control slot (ICS) with cross-group section (CGS) or non-cross-group section (NCGS) for reducing collisions is also presented. The slot reuse can be easily achieved by using the ICS scheme, and the slot utilization of the network can be improved within the high traffic locality.     

Robust semidefinite relaxations for a quadratic OFDMA resource allocation scheme

This paper proposes two robust binary quadratically constrained quadratic programs (BQCQP) for wireless Orthogonal Frequency Division Multiple Access (OFDMA) networks. The first one is based on a scenario uncertainty approach from Kouvelis and Yu [1] and the second is based on an interval uncertainty approach from Bertsimas and Sim [2]. Both robust models allow to decide what modulations and what sub-carriers are going to be used by a particular user in the system depending on its bit rate requirements. Thus, we derive two robust semidefinite relaxations to compute lower bounds. Our numerical results show, in average near optimal integrality gaps of 4.12% and 1.15% under the scenario and interval approach when compared to the optimal solution of the problem derived by linearizing the two quadratic models with Fortet linearization method. Some comparison between the two robust approaches is also provided.     

An opportunistic resource allocation approach for mixed QoS and non-QoS connections in OFDMA wireless networks

An opportunistic resource allocation approach is proposed to guarantee both fair resource allocation and high system throughput under combinations of QoS and non-QoS connections in OFDMA networks. This approach features dynamic connection classification and packet prioritization based on real-time network conditions and QoS constraints. A classifier is first employed to prioritize QoS connections by observing the channel state of each subscriber station and the utilization of network resources. It performs a finite-horizon Markov decision process with dynamic rules affected by system load. The transmission order of packets is then determined by an opportunistic multiservice scheduler according to the QoS requirements of connections and the output of the classifier. Having the scheduling result, an allocator assigns slots to the scheduled packets, and its output is linked back to the connection classifier through a resource usage observer for all subscriber stations. The sub-channel allocation problem is also solved by cooperation between the slot allocator and the packet scheduler. Results of numerical analysis and NS2 simulation confirm the advantages claimed above. The same conclusion can also be drawn from the comparison with several existing approaches in terms of system throughput, service successful ratio, average spectral efficiency, and system revenue.     

下一代WLAN分组目标唤醒时间调度改进方案

密集WLAN(Wireless Local Area Network,无线局域网)中,大规模站点同时接入信道引起激烈竞争,从而导致网络性能急剧下滑.IEEE工作组着手研发下一代WLAN标准IEEE 802.11ax,该标准结合基于正交频分复用多址技术提出了上行多用户随机接入和广播目标唤醒时间(Target Wake T...     

OFDMA中继系统下行链路公平资源分配算法研究*

为了公平有效地在OFDMA中继系统下行链路进行资源分配,提出了基于效用函数的资源分配算法,并根据凸优化问题的原始分解理论,提出了相应的分布式求解算法,得到了相关问题的全局最优解。理论分析和数值仿真结果表明,提出的资源分配算法具有较低的系统复杂度,可以使系统效用函数最大,从而在保证用户公平性的前提下,使系统的和速率容量最大。     

An adaptive sub-carrier and power allocation algorithm with QoS guarantee for OFDMA system

This paper presents an adaptive sub-carrier and power allocation scheme for orthogonal frequency division multiple access （OFDMA） systems according to their different quality of service （QoS） requirements and traffic type. The algorithm maximized the transmission data rate while satisfying total power constraint and a certain bit error rate （BER） requirement. A greedy algorithm known to be the most efficient algorithm for this problem can provide a high quality optimal solution, but has the disadvantage of incurring a long computation time. This problem should be solved in a real-time environment. The proposed algorithm not only avoids the high complexity but also provides considerable universality and flexibility for both the fixed rate voice data and variable rate multimedia data of the broadband wireless communication. It mainly consists of two steps. The first is the allocation of sub-carriers and power alternately to the real-time user. The second is the residual resource distribution to the non-real-time users. The simulation results demonstrate that the scheme has computational advantages over the conventional algorithms while providing the QoS guarantee.     

Improving routing distance for geographic multicast with Fermat points in mobile ad hoc networks

In mobile ad hoc networks (MANETs), each node has the ability to transmit, receive, and route packets, and also moves through the field either randomly or in accordance with a pre-planned route. For enhancing the performance of MANETs, reducing the routing distance is a primary concern. For either ad hoc or static networks, the problem of minimizing the overall routing distance during multicasting is NP-complete. Therefore, it is difficult to determine an optimal solution. This paper presents an efficient geographic multicast protocol, designated as GMFP, based on the use of Fermat points. The objective of GMFP is to improve the overall routing distance for multicast tasks. Through a series of simulations, it is shown that GMFP outperforms the conventional Position-Based Multicast protocol and FERMA protocol in terms of the total routing distance, the packet transmission delay, the packet delivery ratio, and the node energy consumption. The performance improvements provided by GMFP are apparent as the scale of the network topology increases.