The Experts below are selected from a list of 126951 Experts worldwide ranked by ideXlab platform

J.j. Garcia-luna-aceves - One of the best experts on this subject based on the ideXlab platform.

  • Collaborative routing and Channel Access in heterogeneous wireless networks
    2010
    Co-Authors: J.j. Garcia-luna-aceves, Xin Wang
    Abstract:

    We consider the fundamental questions on how Channel Access interacts with the routing protocols in the wireless networks and propose corresponding cross-layer design solutions. Traditionally most wireless routing protocols work independently of the Channel Access method, even though it is not true that routing in wireless networks occurs over a pre-existing network topology and the transmission over one link does not impact the transmissions over other links, as it can be done in a wired network. A comprehensive understanding on the essentials of protocol interaction is indispensable to the design and optimization of protocol stacks, tailored to the unique dynamic environments in wireless networks. In this thesis, we first present an approach that takes advantage of multi-packet reception (MPR) to reduce the negative effects of multiple Access interference and therefore increase the capacity of an wireless network. We analyze the performance upper bound of joint routing and scheduling for wireless networks that embrace interference by using MPR. We formulate the optimization problem under a deterministic model and seek to maximize the aggregate network throughput subject to minimum rate requirements. We then propose a polynomial-time heuristic algorithm aimed at approximating the optimal solution to the joint routing and Channel Access problem under MPR. We show the effectiveness of our heuristic algorithm by comparing its performance with the upper bound. Second, we propose a novel analytical model that captures the functionality of the routing protocols together with the characterization of the performance of the medium Access control protocol (MAC). It reveals the interplay between the protocol functionality and network parameters, and provides new insight on the routing and Channel Access protocol design for wireless networks. Third, we present the CROWN (Collaborative ROuting, scheduling and frequency assignment for Wireless Networks) scheme. CROWN is a cross-layer optimization approach for spectrum-agile nodes to adjust their spectrum allocation and transmission scheduling according to the underlying traffic demands. Instead of choosing the optimal route based on predetermined transmission scheduling and frequency assignment results, CROWN incorporates the efficiency of the underlying frequency assignment and scheduling information into the routing metric calculation, so that the route with the maximal joint spatial and frequency reuse is selected. Simulation results show that CROWN efficiently exploits the frequency diversity and spatial reuse features of spectrum-agile radios.

  • Channel Access using opportunistic reservations and virtual MIMO
    Computer Networks, 2009
    Co-Authors: Xin Wang, J.j. Garcia-luna-aceves, Hamid R. Sadjadpour
    Abstract:

    We propose ORCHESTRA, a Channel-Access protocol that uses reservations and virtual MIMO to provide high throughput and bounded Channel-Access delays. The Channel-Access process is divided into a contention-based Access period and a scheduled Access period. To attain high throughput, nodes build a Channel schedule using the contention-based Access period, and utilize the spatial multiplexing gain of virtual MIMO links in the scheduled Access period. To attain bounded Channel-Access delays, nodes reserve time slots through opportunistic reservations. We evaluate the performance of ORCHESTRA through numerical analysis and simulations, and show that it results in much better throughput, delay, and jitter characteristics that simply using MIMO nodes together with scheduled Access (i.e., NAMA) or contention-based Access (i.e., IEEE 802.11 DCF).

  • ICCCN - Channel Access Using Opportunistic Reservations and Virtual MIMO
    2008 Proceedings of 17th International Conference on Computer Communications and Networks, 2008
    Co-Authors: Xin Wang, J.j. Garcia-luna-aceves, Hamid R. Sadjadpour
    Abstract:

    We propose ORCHESTRA, a Channel Access protocol that uses reservations and virtual MIMO to provide high throughput and bounded Channel Access delays. Channel Access process is divided into a contention-based Access period and a scheduled Access period. To attain high throughput, nodes build the Channel schedule using the contention-based Access period, and utilize the spatial multiplexing gain of virtual MIMO links in the scheduled Access period. To attain bounded Channel Access delays, nodes reserve time slots through opportunistic reservations. We evaluate the performance of ORCHESTRA through numerical analysis and simulations, and show that it results in much better throughput, delay, and jitter characteristics than simply using MIMO nodes together with scheduled Access (i.e., NAMA) or contention-based Access (i.e., IEEE 802.11 DCF).

  • Networking - Election based hybrid Channel Access
    NETWORKING 2007. Ad Hoc and Sensor Networks Wireless Networks Next Generation Internet, 2007
    Co-Authors: Xin Wang, J.j. Garcia-luna-aceves
    Abstract:

    We propose an Election based Hybrid Channel Access (EHCA) protocol for ad hoc network to achieve high throughput and bounded Channel Access delay at the same time. EHCA reduces the contentions during the Channel scheduling formation through fair node elections, which are based on the topology information. Only the elected nodes contend for the Channel and broadcast the scheduling result. Numerical analysis and simulation results show that EHCA outperforms alternative designs.

  • Distributed dynamic Channel Access scheduling for ad hoc networks
    Journal of Parallel and Distributed Computing, 2003
    Co-Authors: Lichun Bao, J.j. Garcia-luna-aceves
    Abstract:

    Three types of collision-free Channel Access protocols for ad hoc networks are presented. These protocols are derived from a novel approach to contention resolution that allows contending entities to elect one or multiple winners for Channel Access in any given contention context (e.g., a time slot) in a distributed fashion. The only required information for each entity is the identifiers of its neighbors one and two hops away in the wireless network. The new protocols are shown to be fair and capable of achieving maximal utilization of the Channel bandwidth. The delay and throughput characteristics of the contention resolution algorithms are analyzed, and the performance of the three types of Channel Access protocols is studied by simulations and compared with that of optimal static scheduling algorithms.

Xuesheng Zhou - One of the best experts on this subject based on the ideXlab platform.

  • Throughput Analysis of LAA and Wi-Fi Coexistence Network With Asynchronous Channel Access
    IEEE Access, 2018
    Co-Authors: Zhenzhou Tang, Xuesheng Zhou
    Abstract:

    The licensed-assisted Access (LAA) technology has been proposed as a promising solution to increase the network capability by extending the frequency bands for long term evolution networks. The performance evaluation of the LAA systems has been extensively studied in recent years. However, most existing works did not consider the fact that Wi-Fi stations and LAA equipments are typically not synchronized in such a heterogeneous network. They are not aligned in time domain because of different time-slot durations, Channel Access back off, and contention window sizes. Therefore, in this paper, we investigate the throughput performance of the LAA and Wi-Fi coexisting networks with asynchronous Channel Access. To deal with the asynchronism, we first introduce the concept of the heterogeneous network superframe based on the fact that the timing relation between LAA and Wi-Fi systems will be restored to a fixed pattern after a busy slot. Thereafter, we model the LAA and Wi-Fi Channel Access behaviors in superframes as 2-D Markov chains, respectively. Based on the Markov chains and the structure of the superframe, we analyze the throughput performance by fully considering the asynchronism of the heterogeneous Channel Access. The accuracy of our theoretical analysis is validated by numerical results. Meanwhile, we have also investigated the effects of the number of LAA equipments, Wi-Fi stations, and the maximum contention window size upon the system throughput.

Dongbo Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Throughput and Channel Access Statistics of Generalized Selection Multiuser Scheduling
    IEEE Transactions on Wireless Communications, 2008
    Co-Authors: Jinghua Jin, Dongbo Zhang
    Abstract:

    To provide a near-optimal low-complexity solution to parallel multiuser scheduling in code-division multiple-Access (CDMA), we propose generalized selection multiuser diversity (GSMuD) schemes with multi-code Channel assignment and analyze their performance. The proposed GSMuD (Lc, L) schemes rank a total of L users awaiting transmissions by their signal-to- noise ratios (SNRs) and select the Lc (1les Lc les L) users with the largest absolute (or normalized) SNRs for parallel Channel Access, which achieve near-optimal sum rate with a low scheduling complexity. The sum and individual Channel throughput rates, second order statistics, fairness, and Channel Access statistics of the proposed GSMuD schemes are derived, taking into account different types of generalized fading Channels. Compared to the round robin (RR) scheduling without SNR ranking, the GSMuD with normalized SNR ranking achieves a substantially higher sum rate while maintaining fairness. GSMuD also significantly improves the Channel Access performance and the degree of fairness than selective multiuser diversity (SMuD), which selects one best user only at each time slot.

  • ICC - Channel Access Statistics of Parallel Multiuser Scheduling
    2007 IEEE International Conference on Communications, 2007
    Co-Authors: Dongbo Zhang
    Abstract:

    Generalized selection multiuser diversity (GSMuD) is a new scheduling scheme which provides a near-optimal low-complexity solution to parallel Access multiuser scheduling. In this scheme, a total of L users awaiting transmissions are ranked by their signal-to-noise ratios (SNRs) and the Nc (1 les Nc les L) users with the largest absolute (or normalized) SNRs are selected for parallel Channel Access. In this paper, we analyze the second order statistics (including the level crossing rate and average fade duration) and Channel Access performance (including the average Channel Access rate, the average Access time, and the average waiting time) of the proposed GSMuD scheme, taking into account different types of generalized fading Channels. Simulation results verify the derived analytical formulas. Numerical results show that compared to the selective multiuser diversity (SMuD), the GSMuD significantly improves the Channel Access rate and Access time, and reduces the Access waiting time. The presented results will be useful for the cross-layer design of multiuser parallel scheduling systems.

Yu-chia Chang - One of the best experts on this subject based on the ideXlab platform.

  • Performance evaluation of wireless sensor network with hybrid Channel Access mechanism
    Journal of Network and Computer Applications, 2009
    Co-Authors: Prasan Kumar Sahoo, Jang-ping Sheu, Yu-chia Chang
    Abstract:

    In this paper, a hybrid Channel Access mechanism is proposed for the wireless sensor network that considers the Channel Access procedure of IEEE 802.15.4 and combines the binary exponential backoff mechanism of IEEE 802.11 due to packet collision of nodes after successful Channel assessment. Taking the backlogged nodes due to collision, an extended linear feedback model is developed and a discrete-time Markov chain model is designed to analyze the successful and failure probabilities of the system model of the wireless sensor network. Besides, an energy consumption model for the one hop wireless sensor network is developed based on our models and hybrid Channel Access mechanism. Extensive performance analysis are done to study the effect of binary exponential contention window on energy consumption of the nodes and it is verified that our simulation results totally match with the theoretical results for different size of contention windows and node numbers.

Yuguang Fang - One of the best experts on this subject based on the ideXlab platform.

  • Deterministic Priority Channel Access Scheme for QoS Support in IEEE 802.11e Wireless LANs
    IEEE Transactions on Vehicular Technology, 2009
    Co-Authors: Sunmyeng Kim, Rongsheng Huang, Yuguang Fang
    Abstract:

    The enhanced distributed Channel Access (EDCA) of IEEE 802.11e has been standardized to support quality of service (QoS) in wireless local area networks (LANs). The EDCA statistically supports the QoS by differentiating the probability of Channel Access among different priority traffic and does not provide the deterministically prioritized Channel Access for high-priority traffic, such as voice or real-time video. Therefore, lower priority traffic still affects the performance of higher priority traffic. In this paper, we propose a simple and effective scheme called deterministic priority Channel Access (DPCA) to improve the QoS performance of the EDCA mechanism. To provide guaranteed Channel Access to multimedia applications, the proposed scheme uses a busy tone to limit the transmissions of lower priority traffic when higher priority traffic has packets to send. Performance evaluation is conducted using both numerical analysis and simulation and shows that the proposed scheme significantly outperforms the EDCA in terms of throughput, delay, delay jitter, and packet drop ratio under a wide range of contention level.