Multiuser Resource Allocation Research Articles

Cross-layer multiuser resource allocation for video communication over OFDM networks

In this paper, we propose a resource allocation algorithm to transmit multiple video bitstreams over multiuser orthogonal frequency division multiplex (OFDM) networks. The proposed algorithm explores a low-complexity rate-distortion function and diversity of multiuser OFDM systems subject to constraints on delay and limited system resources. A set of relative importance is imposed in resource allocation to assure that each user can achieve the required data rate and the quality of service. We first present a simple and effective rate-distortion function including a temporal error propagation effect and relative importance. Then we propose the cross-layer multiuser resource allocation algorithm that consists of subcarrier assignment and power allocation for minimizing the overall video distortion. The proposed subcarrier assignment algorithm utilizes the subgradient method adopting a shadow price mechanism by assuming equal power distribution for each user. Based on the result of subcarrier assignment, the power allocation algorithm maximizes the sum of distortion reduction while the relative importance for each user is maintained. In simulation results, the proposed resource allocation algorithm outperforms the time division multiple access (TDMA) and the previous resource allocation algorithm maximizing the sum capacity in terms of the worst received video quality among users. The proposed algorithm achieves PSNR gain by 1.0 – 3.0 dB , compared to the previous resource allocation algorithm considering rate-distortion function. It is shown that the proposed resource allocation algorithm distributes the video distortion among users more fairly with relative importance compared to the previous algorithms.

Cognitive Radio Based Multi-User Resource Allocation in Mobile Ad Hoc Networks Using Multi-Carrier CDMA Modulation

In this paper, we propose a cognitive radio based multi-user resource allocation framework for mobile ad hoc networks using multi-carrier DS CDMA modulation over a frequency-selective fading channel. In particular, given preexisting communications in the spectrum where the system is operating, in addition to potential narrow-band interference, a channel sensing and estimation mechanism is provided to obtain information such as subcarrier availability, noise power and channel gain. Given this information, both frequency spectrum and power are allocated to emerging new users (i.e., cognitive radio users), based on a distributed multi-user resource allocation framework, in order to satisfy a target data rate and a power constraint of each cognitive radio user, while attempting to avoid interference to the existing communications as well as to minimize total power consumption of the cognitive radio users.

A Multi-Server Scheduling Framework for Resource Allocation in Wireless Multi-Carrier Networks

Multiuser resource allocation has recently been recognized as an effective methodology for enhancing the power and spectrum efficiency in OFDM (orthogonal frequency division multiplexing) systems. It is, however, not directly applicable to current packet-switched networks because most existing packet- scheduling schemes are based on a single-server model and do not serve multiple users at the same time. In this paper, we propose a cross-layer resource allocation algorithm based on a novel multi-server scheduling framework to achieve overall high system power efficiency in packet-switched OFDM networks. Our contribution is four fold: (i) we propose and analyze a MPGPS (multi-server packetized general processor sharing) service discipline that serves multiple users at the same time and facilitates multiuser resource allocation; (ii) we present a MPGPS-based joint MAC-PHY resource allocation scheme that incorporates packet scheduling, subcarrier allocation, and power allocation in an integrated framework; (iii) by investigating the fundamental tradeoff between multiuser-diversity and queueing performance, we present an A-MPGPS (adaptive MPGPS) service discipline that strikes balance between power efficiency and queueing performance; and (iv) we extend MPGPS to an O-MPGPS (opportunistic MPGPS) service discipline to further enhance the resource utilization efficiency.

A Pricing Mechanism for Resource Allocation in Wireless Multimedia Applications

We consider the problem of multiuser resource allocation for wireless multimedia applications deployed by autonomous and noncollaborative wireless stations (WSTAs). Existing resource allocation solutions for WLANs are not network-aware and do not take into account the selfish behavior of individual WSTAs. Specifically, the selfish WSTAs can manipulate the network by untruthfully representing their private information (i.e., video characteristics, experienced channel conditions, and deployed streaming strategies). This often results in inefficient resource allocations. To overcome this obstacle, we present a pricing mechanism for message exchanges between the WSTAs and the Central Spectrum Moderator (CSM). The messages represent network-aware resource demands and corresponding prices. We prove that the message exchanges reach the Nash equilibrium and that the resulting equilibrium messages generate allocations which are efficient, budget balanced, and satisfy voluntary participation. The simulation results verify that these properties hold when the WSTAs behave strategically. Additionally, we evaluate the impact of initial prices and network congestion level on the convergence rate of message exchanges.

Joint Uplink and Downlink Optimization for Real-Time Multiuser Video Streaming Over WLANs

In this paper, a network-aware and source-aware video streaming system is proposed to support interactive multiuser communications within single-cell and multicell IEEE 802.11 networks. Unlike the traditional streaming video services, the strict delay constraints of an interactive video streaming system pose more challenges. These challenges include the heterogeneity of uplink and downlink channel conditions experienced by different users, the multiuser resource allocation of limited radio resources, the incorporation of the cross-layer design, and the diversity of content complexities exhibited by different video sequences. With the awareness of video content and network resources, the proposed system integrates cross-layer error protection mechanism and performs dynamic resource allocation across multiple users. We formulate the proposed system as to minimize the maximal end-to-end expected distortion received by all users, subject to maximal transmission power and delay constraints. To reduce the high dimensionality of the search space, fast multiuser algorithms are proposed to find the near-optimal solutions. Compared to the strategy without dynamically and jointly allocating bandwidth resource for uplinks and downlinks, the proposed framework outperforms by 2.18~7.95 dB in terms of the average received PSNR of all users and by 3.82~11.50 dB in terms of the lowest received PSNR among all users. Furthermore, the proposed scheme can provide more uniform video quality for all users and lower quality fluctuation for each received video sequence.

Bargaining Strategies for Networked Multimedia Resource Management

Multiuser multimedia applications such as enterprise streaming, surveillance, and gaming are recently emerging, and they are often deployed over bandwidth-constrained network infrastructures. To ensure the quality of service (QoS) required by the delay-sensitive and bandwidth intensive multimedia data for these applications, efficient resource (bandwidth) management becomes paramount. We propose to deploy the well-known game theoretic concept of bargaining to allocate the bandwidth fairly and optimally among multiple collaborative users. Specifically, we consider two bargaining solutions for our resource management problem: the Nash bargaining solution (NBS) and the Kalai-Smorodinsky bargaining solution (KSBS). We provide interpretations for the two investigated bargaining solutions for multiuser resource allocation: the NBS can be used to maximize the system utility, while the KSBS ensures that all users incur the same utility penalty relative to the maximum achievable utility. The bargaining strategies and solutions are implemented in the network using a resource manager, which explicitly considers the application-specific distortion for the bandwidth allocation. We show that the bargaining solutions exhibit important properties (axioms) that can be used for effective multimedia resource allocation. Moreover, we propose several criteria for determining bargaining powers for these solutions, which enable us to provide additional flexibility in choosing solution by taking into consideration the visual quality impact, the deployed spatiotemporal resolutions, etc. We also determine the complexity of these solutions for our application and quantify the performance of the proposed bargaining-based resource strategies for different scenarios.

Recent advances in video communications for 4G wireless systems

In recent years, there has been a rapidly increasing demand for the development of advanced interactive multimedia applications such as video telephony, video games, and TV broadcasting. However, these applications are always stringently constrained by current wireless system architectures due to the need for high data rates for video transmission. To better serve this need, 4G broadband mobile systems are in planning and are expected to increase the mobile data transmission rates and bring higher spectral efficiency, lower cost per transmitted bit, and increased flexibility of mobile terminals and networks. The new technology strives to eliminate the distinction between video over wireless and video over wireline networks. In the meantime, great opportunities are provided for proposing novel wireless video protocols and applications, and developing advanced video coding and communications systems, and algorithms for the next-generation video applications that can take maximum advantage of the 4G wireless systems. This special issue was proposed under such background to bridge the gap between the current system constraints and proposed system capabilities. By nature, this special session is not able to cover all the important development or provide a complete overview of the state-of-the-art in this vast area. However, we select eight articles from plenty of high-quality submissions to focus on the most attractive topics in the area such as cross-layer optimized resource allocation, wireless video streaming, video source coding for mobile applications, and wireless video delivery. We hope that these articles serve the purposes of encouraging more researchers to dig deeper into this rich land and to overcome the barriers that constrain today the advanced multimedia applications. In wireless networks, due to the fluctuation of power and bandwidth constraints and random timevarying fading effect, the resource allocation has to be performed dynamically during communications to satisfy the stringent quality of service (QoS) requirements. Therefore, cross-layer design methodologies become natural choices to guarantee reliable and high-quality end-to-end performance. In this issue, two papers are invited on the topic of cross-layer optimized resource allocation. In the first article by Peshala V. Pahalawatta et al. entitled ‘Review of content aware resource allocation schemes for video streaming over wireless networks,’ the wireless video streaming is reviewed from a rate-distortion resource allocation aspect, that is, how to achieve an effective cross-layer design that efficiently manages the limited system resources while taking into account the timevarying wireless channel conditions as well as the varying media content for delivery. The article discusses two well-known scenarios for video streaming one is a downlink case that the video has been pre-encoded and the scheduler adapts to channel conditions and controls the source rate by either packet dropping or scalable coding, and the other is a real-time point-to-point video streaming where the transmitting device has control over the coding and network parameters so that the source coding parameters can be jointly determined along with the transmission power and bandwidth allocation. The second article by Kai Yang et al. entitled ‘Multiuser resource allocation for video transmission over a chipinterleaved multicarrier system’ proposes a system for scalable downlink video transmission over emerging 4G wireless networks where protected bitstreams are sent from the server to potentially thousands of clients over a multicarrier system with two-layer interleaving

Advances in smart antennas - Dynamic multiuser resource allocation and adaptation for wireless systems

Driven by the increasing popularity of wireless broadband services, future wireless systems will witness a rapid growth of high-data-rate applications with very diverse quality of service requirements. To support such applications under limited radio resources and harsh wireless channel conditions, dynamic resource allocation, which achieves both higher system spectral efficiency and better QoS, has been identified as one of the most promising techniques. In particular, jointly optimizing resource allocation across adjacent and even nonadjacent layers of the protocol stack leads to dramatic improvement in overall system performance. In this article we provide an overview of recent research on dynamic resource allocation, especially for MIMO and OFDM systems. Recent work and open issues on cross-layer resource allocation and adaptation are also discussed. Through this article, we wish to show that dynamic resource allocation will become a key feature in future wireless communications systems as the subscriber population and service demands continue to expand