支持实时多媒体业务QoS醮LTE下行调度研究

日益增长的多媒体业务要求下一代移动通信系统支持具有不同QoS要求的业务。针对LTE下行链路资源分配和调度问题,介绍了支持实时多媒体业务QoS调度算法的最新成果与进展,并对未来研究方向进行了分析展望。     

A multi‐cell adaptive resource allocation scheme based on potential game for ICIC in LTE‐A

Intercell interference coordination in Third Generation Partnership Project long‐term evolution‐advanced system has received much attention both from the academia and the standardization communities. Moreover, the network architecture of long‐term evolution‐advanced system is modified to take into account coordinated transmission. In this article, we study the dynamic resource allocation problem and potential game theory and propose a multicell adaptive distributed resource allocation algorithm based on potential game. The allocation process is divided into two steps; subchannel is allocated first, and then, transmitted power is optimized dynamically according to a novel pricing factor. Besides, existence and uniqueness of Nash equilibrium of the proposed game model are assured. As a result, intercell interference is well coordinated. Simulation results show that transmitted power is saved efficiently and system fairness is improved to a large extent, accompanied with good performance gain of total and cell‐edge throughputs. Copyright © 2013 John Wiley & Sons, Ltd.     

QoS‐aware routing and power control algorithm for multimedia service over multi‐hop mobile ad hoc network

This paper presents a QoS (quality of service) aware routing and power control algorithm consuming low transmission power for multimedia service over mobile ad hoc network. Generally, multimedia services need stringent QoS over the network. However, it is not easy to guarantee the QoS over mobile ad hoc network since its network resources are very limited and time‐varying. Furthermore, only a limited amount of power is available at mobile nodes, which makes the problem more challenging. We propose an effective routing and power control algorithm for multimedia services that satisfies end‐to‐end delay constraint with low transmission power consumption. The proposed algorithm supports the required bandwidth by controlling each link channel quality over route in a tolerable range. In addition, a simple but effective route maintenance mechanism is implemented to avoid link failures that may significantly degrade streaming video quality. Finally, performance comparison with existing algorithms is presented in respect to traditional routing performance metrics, and an achievable video quality comparison is provided to demonstrate the superiority of the proposed algorithm for multimedia services over mobile ad hoc network. Copyright © 2010 John Wiley & Sons, Ltd.     

A preemption‐based scheduling algorithm for WiMAX networks

Several scheduling techniques were designed for the base station (BS) of IEEE 802.16e wireless interoperability of microwave access networks. However, depending on the BS scheduler alone to determine the servicing order of each connection might affect the accuracy of the scheduling process because the BS does not necessarily have enough up‐to‐date information about the current state of the connections at the subscriber station. In this paper, we propose a preemption‐based scheduling algorithm that focuses on improving the quality of service requirements of real‐time service flow classes. The proposed algorithm incorporates two schedulers, one at the BS and another one at the subscriber station. We have implemented and integrated the proposed algorithm with the network simulator NS2 using the Network and Distributed Systems Laboratory wireless interoperability of microwave access module. Simulation results have shown that the proposed approach outperforms other scheduling algorithms in terms of enhancing the throughput and the average delay of real‐time quality of service classes. Copyright © 2013 John Wiley & Sons, Ltd.     

Traffic‐aware downlink power allocation in multiuser OFDM system

Multiuser orthogonal frequency division multiplexing (OFDM) is a promising technology to achieve high uplink/downlink (DL) capacities in the next generation broadband wireless networks such as WiMAX (Worldwide Interoperability for Microwave Access). In this paper, we investigate the DL adaptive power allocation (APA) in multiuser OFDM system from the perspective of cross‐layer design. Specifically, we formulate APA as an optimization problem with the traffic profile of each user asit a priori knowledge. To solve the optimization problem, we develop a fairness‐constrained optimal prioritized effective throughput (PET) strategy and the corresponding iterative algorithms, aiming at balancing the prioritized effective throughput and the linear or logarithmic user satisfaction‐based fairness. Simulation results show that our proposed APA optimization approach can achieve satisfying performance. Copyright © 2011 John Wiley & Sons, Ltd.     

A novel QoS‐aware MAC protocol for voice services over IEEE 802.11‐based WLANs

With the pervasive growth in the popularity of IEEE 802.11‐based wireless local area networks (WLANs) worldwide, the demand to support delay‐sensitive services such as voice has increased very rapidly. This paper provides a comprehensive survey on the medium access control (MAC) architectures and quality of service (QoS) provisioning issues for WLANs. The major challenges in providing QoS to voice services through WLAN MAC protocols are outlined and the solution approaches proposed in the literature are reviewed. To this end, a novel QoS‐aware wireless MAC protocol, called hybrid contention‐free access (H‐CFA) protocol and a call admission control technique, called traffic stream admission control (TS‐AC) algorithm, are presented. The H‐CFA protocol is based on a novel idea that combines two contention‐free wireless medium access approaches, that is, round‐robin polling and time‐division multiple access (TDMA)‐like time slot assignment, and it increases the capacity of WLANs through efficient silence suppression. The TS‐AC algorithm ensures efficient admission control for consistent delay‐bound guarantees and further maximizes the capacity through exploiting the voice characteristic that it can tolerate some level of inconsecutive packet loss. The benefits of the proposed schemes are demonstrated in the simulations results. Copyright © 2008 John Wiley & Sons, Ltd.     

A green scheduling with adaptive spatial division multiple access grouping for multi‐user coordinated multi‐point networks

Multi‐User Coordinated Multi‐Point (MU‐CoMP), which couples CoMP with Multi User‐Multiple Input Multiple Output (MU‐MIMO), appears as a promising solution to enhance the Long Term Evolution‐Advanced (LTE‐A) system performance. However, some challenging issues in MU‐CoMP networks require more investigation. First, the set of users transmitting under CoMP mode should be properly identified. Secondly, time‐frequency resource should be efficiently partitioned between CoMP and non‐CoMP users in order to improve the system radio capacity. Thirdly, a fair and green scheduler is much needed for a more energy efficient system. This paper deals with these three issues. We propose an adaptive transmission mode selection according to the total load in the cluster and to users' quality of service. The adequate size of the Spatial Division Multiple Access users' groups is also analyzed. We finally propose a new scheduling algorithm to further enhance the radio capacity and the energy consumption in the cluster. Simulations results showed that significant improvements are obtained in terms of total system throughput and outage probability in the cluster with our proposed scheme. Moreover, energy efficiency has increased by four times with our proposed scheduling algorithm as compared to commonly used schedulers. Copyright © 2015 John Wiley & Sons, Ltd.     

Adaptive Resource Allocation for Uplink Carrier Aggregation Scheme in LTE‐A‐Type Networks

Carrier aggregation is an essential feature in the Long Term Evolution‐Advanced (LTE‐A) system, which allows the scalable expansion of the effective bandwidth to be delivered to user equipment (UE) through the concurrent use of radio resources across multiple component carriers (CCs). This system's optimal radio‐resource use has received much attention under simultaneous access (SA) scenarios for multiple CCs (m‐CCs). This letter establishes how many CCs a UE should simultaneously connect to maintain maximum uplink capacity. Under the m‐CC LTE‐A system, the spectral efficiency of the m‐CC SA scheme (m≥2) is compared with that of CC selection (CCS). Numerical results reveal that the 2‐CC SA scheme outperforms CCS and performs almost equally to the m‐CC SA scheme (m≥3).     

A universal frequency reuse scheme in LTE‐A heterogeneous networks

Effective inter‐cell interference mitigation has been extensively studied because of its outstanding cell‐edge signal quality improvement capability. Conventional static inter‐cell interference coordination strategies, including fractional frequency reuse and soft frequency reuse, have received much attention owing to their effectiveness in mitigating interference and low complexity in implementation. However, they are less effective when dealing with dense uneven traffic distributions and dynamic traffic demands and thus incur low spectrum utilization in some cells and spectrum shortage in others. This paper proposes a universal frequency reuse scheme in a two‐layer Long Term Evolution‐Advanced heterogeneous network to ensure good throughput for all user equipment (UE), especially UEs at cell edge. The proposed scheme allows each cell to use all the spectrum resources, limited by an orderly regulation of all sub‐bands. This scheme minimizes the potential occurrence probability of inter‐cell co‐sub‐band interference through an intra‐cell sub‐band resource management. Furthermore, a graph‐theoretic based sub‐band allocation algorithm is developed to optimize UE throughput performance, especially for the cell‐edge low signal to interference noise ratio UEs. A comprehensive performance comparison among different frequency reuse schemes is conducted by considering performance metrics, including cell‐edge throughput, average throughput, and signal to interference noise ratio cumulative distribution function. Simulation result shows that the universal frequency reuse scheme outperforms other two schemes significantly. Copyright © 2016 John Wiley & Sons, Ltd.     

Downlink cross‐layer scheduling strategies for long‐term evolution and long‐term evolution‐advanced systems

The most recent trend in the Information and Communication Technology world is toward an ever growing demand of mobile heterogeneous services that imply the management of different quality of service requirements and priorities among different type of users. The long‐term evolution (LTE)/LTE‐advanced standards have been introduced aiming to cope with this challenge. In particular, the resource allocation problem in downlink needs to be carefully considered. Herein, a solution is proposed by resorting to a modified multidimensional multiple‐choice knapsack problem modeling, leading to an efficient solution. The proposed algorithm is able to manage different traffic flows taking into account users priority, queues delay, and channel conditions achieving quasi‐optimal performance results with a lower complexity. The numerical results show the effectiveness of the proposed solution with respect to other alternatives. Copyright © 2013 John Wiley & Sons, Ltd.     

Leveraging multiuser diversity for adaptive hybrid satellite‐LTE downlink scheduler (H‐MUDoS) in emerging 5G‐satellite network

In order to achieve ubiquitous coverage and service continuity in future 5G network, satellite‐based access is the best solution to complement the terrestrial LTE‐A. In light of this, we introduce a channel‐aware hybrid scheduling technique on the basis of satellite‐LTE spectrum sharing. According to the user‐experienced channel, base stations (eNodeB) and the satellite will work cooperatively. The eNodeB mainly provides service in urban area for high density population. Meanwhile, the satellite will perform either offloading, providing service for under‐served users, or extra coverage for users in rural and remote areas having no coverage of eNodeB. Leveraging the multiuser diversity, we implement a new metrics computation method for hybrid satellite‐LTE downlink scheduler (H‐MUDoS). Compared with other existing schedulers, simulation results clearly demonstrate the high performance of H‐MUDoS in terms of spectral efficiency in addition to improvement of the quality‐of‐service requirements and capacity maximization.     

Integrated power saving for relay node and user equipment in LTE‐A

By introduction of relay nodes, LTE‐Advanced can provide enhanced coverage and capacity at cell edges and hot‐spot areas. The authors have been researching the issue of power saving in mobile communications technology such as WiMax and Long Term Evolution (LTE) for some years. Based on the previous idea of load‐based power saving, two strategies each with associated schemes to integrated relay nodes and user equipment in power saving are proposed in the paper. Simulation study shows the benefit of the proposed schemes in terms of better power saving than the standard‐based scheme at the cost of moderately increased delay. Extended discussion about the impact of different load distribution among user equipments and the impact of a worse backhaul link on power saving is also presented in the paper. Copyright © 2015 John Wiley & Sons, Ltd.     

QoS‐Guaranteed Multiuser Scheduling in MIMO Broadcast Channels

This paper proposes a new multiuser scheduling algorithm that can simultaneously support a variety of different quality‐of‐service (QoS) user groups while satisfying fairness among users in the same QoS group in MIMO broadcast channels. Toward this goal, the proposed algorithm consists of two parts: a QoS‐aware fair (QF) scheduling within a QoS group and an antenna trade‐off scheme between different QoS groups. The proposed QF scheduling algorithm finds a user set from a certain QoS group which can satisfy the fairness among users in terms of throughput or delay. The antenna trade‐off scheme can minimize the QoS violations of a higher priority user group by trading off the number of transmit antennas allocated to different QoS groups. Numerical results demonstrate that the proposed QF scheduling method satisfies different types of fairness among users and can adjust the degree of fairness among them. The antenna trade‐off scheme combined with QF scheduling can improve the probability of QoS‐guaranteed transmission when supporting different QoS groups.     

Graph‐based resource allocation algorithms for multiuser downlink MIMO‐OFDMA networks

Multiuser multiple‐input multiple‐output orthogonal frequency division multiple access (MIMO‐OFDMA) is considered as the practical method to attain the capacity promised by multiple antennas in the downlink direction. However, the joint calculation of precoding/beamforming and resource allocation required by the optimal algorithms is computationally prohibitive. This paper proposes computationally efficient resource allocation algorithms that can be invoked after the precoding and beamforming operations. To support stringent and diverse quality of service requirements, previous works have shown that the resource allocation algorithm must be able to guarantee a specific data rate to each user. The constraint matrix defined by the resource allocation problem with these data rate constraints provides a special structure that lends to efficient solution of the problem. On the basis of the standard graph theory and the Lagrangian relaxation, we develop an optimal resource allocation algorithm that exploits this structure to reduce the required execution time. Moreover, a lower‐complexity suboptimal algorithm is introduced. Extensive simulations are conducted to evaluate the computational and system‐level performance. It is shown that the proposed resource allocation algorithms attain the optimal solution at a much lower computational overhead compared with general‐purpose optimization algorithms used by previous MIMO‐OFDMA resource allocation approaches. Copyright © 2012 John Wiley & Sons, Ltd.     

SRGH: A secure and robust group‐based handover AKA protocol for MTC in LTE‐A networks

Machine‐type communication (MTC) is defined as an automatic aggregation, processing, and exchange of information among intelligent devices without humans intervention. With the development of immense embedded devices, MTC is emerging as the leading communication technology for a wide range of applications and services in the Internet of Things (IoT). For achieving the reliability and to fulfill the security requirements of IoT‐based applications, researchers have proposed some group‐based handover authentication and key agreement (AKA) protocols for mass MTCDs in LTE‐A networks. However, the realization of secure handover authentication for the group of MTCDs in IoT enabled LTE‐A network is an imminent issue. Whenever mass MTCDs enter into the coverage area of target base‐station simultaneously, the protocols incur high signaling congestion. In addition, the existing group‐based handover protocols suffer from the huge network overhead and numerous identified problems such as lack of key forward/backward secrecy, privacy‐preservation. Moreover, the protocols fail to avoid the key escrow problem and vulnerable to malicious attacks. To overcome these issues, we propose a secure and robust group‐based handover (SRGH) AKA protocol for mass MTCDs in LTE‐A network. The protocol establishes the group key update mechanism with forward/backward secrecy. The formal security proof demonstrates that the protocol achieves all the security properties including session key secrecy and data integrity. Furthermore, the formal verification using the AVISPA tool shows the correctness and informal analysis discusses the resistance from various security problems. The performance evaluation illustrates that the proposed protocol obtains substantial efficiency compared with the existing group‐based handover AKA protocols.     

The effects of shadow‐fading on QoS‐aware routing and admission control protocols designed for multi‐hop MANETs

Providing quality‐of‐service (QoS) assurances in a mobile ad hoc network (MANET) is difficult due to node mobility, contention for channel access, a lack of centralised coordination, and the unreliable nature of the wireless channel. QoS‐aware routing (QAR) and admission control (AC) protocols comprise two of the most important components of a system attempting to provide QoS guarantees in the face of the above‐mentioned difficulties. This paper presents a comparative study, utilising a realistic shadow fading channel, of the performance of several state‐of‐the‐art amalgamated QAR‐AC protocols, which are designed for providing throughput guarantees to applications. The advantages and drawbacks of their particular features are highlighted. For an environment where link quality varies rapidly, the results of the study highlight the ineffectiveness of previously‐proposed methods of relying merely on the success of route discovery to perform AC, of relying on the exceeding of the MAC layer retransmission count for link failure detection, of existing congestion detection schemes and of careful re‐admission of data sessions rather than fast re‐routing after shadowing‐induced link failures. Based on the lessons learnt, design guidelines for future QAR and AC protocols operating in a mobile shadow‐fading‐afflicted environment are presented. Copyright © 2010 John Wiley & Sons, Ltd.     

Frame‐based adaptive uplink scheduling algorithm in orthogonal frequency division multiple access‐based Worldwide Interoperability for Microwave Access networks

Because the orthogonal frequency division multiple access physical resource available for scheduling in Worldwide Interoperability for Microwave Access networks is frame by frame, an uplink scheduler located at the base station must efficiently allocate available resources to the subscriber stations in response to constant or bursty data traffic on a per‐frame basis. Available resources for real‐time and nonreal‐time traffics, called frame‐based adaptive bandwidth allocation and minimum guarantee and weight‐based bandwidth allocation, respectively, are proposed in this paper. Moreover, both short‐term and long‐term bandwidth predictions for traffic are incorporated so that the long‐term bandwidth prediction can have sustainable throughput requirement, and the short‐term bandwidth prediction can meet the objectives of low delay and jitter. For the scenarios studied, it shows that system performance of the proposed algorithm is better than the hybrid (earliest deadline first + weighted fair queuing + FIFO) algorithm in terms of packet delay, jitter, throughput, and fairness. Copyright © 2011 John Wiley & Sons, Ltd.     

A study on a receiver‐based management scheme of access link resources for QoS‐controllable TCP connections

Although the bandwidth of access networks is rapidly increasing with the latest techniques such as DSL and FTTH, the access link bandwidth remains a bottleneck, especially when users activate multiple network applications simultaneously. Furthermore, since the throughput of a standard TCP connection is dependent on various network parameters, including round‐trip time and packet loss ratio, the access link bandwidth is not shared among the network applications according to the user's demands. In this thesis, we present a new management scheme of access link resources for effective utilization of the access link bandwidth and control of the TCP connection's throughput. Our proposed scheme adjusts the total amount of the receive socket buffer assigned to TCP connections to avoid congestion at the access network, and assigns it to each TCP connection according to characteristics in consideration of QoS. The control objectives of our scheme are (1) to protect short‐lived TCP connections from the bandwidth occupation by long‐lived TCP connections, and (2) to differentiate the throughput of the long‐lived TCP connections according to the upper‐layer application's demands. One of the results obtained from the simulation experiments is that our proposed scheme can reduce the delay of short‐lived document transfer perceived by the receiver host by up to about 90%, while a high utilization of access link bandwidth is maintained. Copyright © 2006 John Wiley & Sons, Ltd.     

A congestion reduction mechanism using D2D cooperative relay for M2M communication in the LTE‐A cellular network

The Long Term Evolution‐advanced cellular network is designed for human‐to‐human communication. When a large number of machine‐to‐machine (M2M) devices are trying to access the network simultaneously, it leads to a low random access (RA) successful rate and high congestion problem, which may cause the waste of radio resources, packet loss, latency, extra power consumption, and the worst, M2M service error. There is an urge to propose an efficient method for M2M communication on the LTE‐A network to resolve the congestion problem. In this paper, we propose a congestion reduction mechanism, which can analyze and model the RA procedure on the Long Term Evolution‐advanced network, to find out the collapse point in the RA procedure and then design a scheme named device‐to‐device cooperative relay scheme to relieve the congestion problem. Meanwhile, this work also adds a relay access barring algorithm to improve performance and an RA resource separation mechanism for human‐to‐human communication. The proposed method can effectively reduce the network congestion problem. Simulation results show that the network throughput and the congestion can be significantly improved using the proposed mechanism. Copyright © 2016 John Wiley & Sons, Ltd.     

Efficient packet scheduling for heterogeneous multimedia provisioning over broadband satellite networks: An adaptive multidimensional QoS‐based design

With their inherent broadcast capabilities and reliable extensive geographical coverage, the broadband satellite networks are emerging as a promising approach for the delivery of multimedia services in 3G and beyond systems. Given the limited capacity of the satellite component, to meet the diverse quality of service (QoS) demands of multimedia applications, it is highly desired that the available resources can be adaptively utilized in an optimized way. In this paper, we draw our attention on the development and evaluation of an efficient packet scheduling scheme in a representative broadband satellite system, namely satellite digital multimedia broadcasting (SDMB), which is positioned as one of the most attractive solutions in the convergence of a closer integration with the terrestrial mobile networks for a cost‐effective delivery of point‐to‐multipoint services. By taking into account essential aspects of a successful QoS provisioning while preserving the system power/resource constraints, the proposed adaptive multidimensional QoS‐based (AMQ) packet scheduling scheme in this paper aims to effectively satisfy diverse QoS requirements and adaptively optimize the resource utilization for the satellite multimedia broadcasting. The proposed scheme is formulated via an adaptive service prioritization algorithm and an adaptive resource allocation algorithm. By taking into account essential performance criteria, the former is capable of prioritizing contending flows based on the QoS preferences and performance dynamics, while the latter allocates the resources, in an adaptive manner, according to the current QoS satisfaction degree of each session. Simulation results show that the AMQ scheme achieves significantly better performance than those of existing schemes on multiple performance metrics, e.g. delay, throughput, channel utilization and fairness. Copyright © 2008 John Wiley & Sons, Ltd.