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Decentralized cognitive radio networks (CRN) require efficient channel access protocols to enable cognitive secondary users (SUs) to access the primary channels in an opportunistic way Without any coordination. In this paper, we develop a distributed spectrum access protocol for the case where the SUs aim to maximize the total system throughput while competing for spectrum resources. To model the...
Distributed medium access control protocols can be classified into contention-based and contention-free protocols. In this paper, we analyse a contention-free distributed protocol where nodes make reservations on a first-come first-served basis. We evaluate the impact of this first-come first-served approach on the fairness regarding throughput and delay, by means of the ECMA-368. This standard establishes...
A new cross-layer design taking advantage of OFDMA in ad hoc networks is presented. OFDMA technology is exploited at the physical layer to improve data rate through multiuser diversity and to enhance network throughput by enabling multiple concurrent transmissions over orthogonal subchannels, each consisting of a group of tones. A new tone-assignment algorithm is presented that takes advantage of...
This paper investigates open vs. closed access in the uplink of femtocell networks, for the particular case of orthogonal multiple access protocols like TDMA or OFDMA. Open access reduces near-far interference and provides an inexpensive way to expand the capacity of the operator's network. Additionally, with a cap on the amount of resources allocated to the cellular users, open access ensures the...
In this work, a new approach for dynamically allocating high priority probability and high priority slots in PR-ALOHA (Reserved ALOHA with Priority) was introduced. The Dynamic Slot Allocation (DSA) algorithm in PR-ALOHA is performed by dynamically allocating the number of high priority slots and high priority probability based on the available traffic. The performance of the system with DSA algorithm...
This paper reports a study concerning the assessment of cooperation effects at MAC layer in DVB-RCS systems. In particular, a modified resource allocation mechanism has been considered in order to implement a Selective Forwarding cooperation scheme within a group of sources working in a land-vehicular scenario. The achieved results are presented in terms of aggregated average throughput for different...
Coexistence between networks is an emerging challenge in the 60 GHz unlicensed band. An approximate analytical formulation of the saturated throughput of a cognitive IEEE 802.15.3c MAC in the directional contention access period (D-CAP) in the presence of contention time allocation period (CTAP) is presented in this paper. The analytical framework is formulated for N devices, including the pico-net...
In this paper, we propose a new 802.16 Qos scheduling architecture based on GPSS, integrating some kinds of existing scheduling algorithms. Then we design a simulation experiment to validate the effectiveness of the Qos scheduling architecture using Anylogic. The simulation results prove the new QoS architecture is effective, which can not only meet the delay requirement of real time applications,...
One of the major concerns in wireless sensor networks (WSNs) is improving the network lifetime. This paper addresses the problem of energy saving in an IEEE 802.15.4a large-scale full mesh WSNs based on UWB technology. It presents a network architecture to facilitate resource sharing and to ensure load and energy balancing. With a particular focus on medium access control (MAC) protocols, we propose...
In this paper, a queue aware game theoretic cross-layer scheme is introduced for multiuser orthogonal frequency division multiple access (OFDMA) wireless systems. A joint scheduling process that combines an adaptive modulation (AM) at the physical layer (PHYL) along with a discrete Markov modulated Poisson process (dMMPP) at the medium access control (MAC) layer, is devised. Moreover, relied on this...
Multimedia communications over the Internet have undergone considerable growth in recent years thanks to various mature technologies. However, the well-known wireless standard IEEE 802.11 cannot provide adequate bandwidth and jitter for multimedia communications. In this paper, a dual-mode access scheme with QoS features is proposed to solve the asymmetric link problem resulting from the 802.11 distributed...
For a three node cooperative wireless network with an overall transmission power constraint, we present an adaptive cross-layer design framework for maximization of a single user throughput using the power allocation ratio among the source and relay nodes, the packet length, and the modulation level as optimization variables. The design framework integrates automatic repeat request (ARQ) at the MAC...
This paper investigates resource allocation and scheduling schemes based on utility theory in a multiuser OFDM home power line communication (PLC) network since utility can evaluate network performance in terms of the level of users' satisfaction from network resource provision. The proposed cross-layer scheme consists of two phases: subcarrier allocation at the physical (PHY) layer and scheduling...
Fast reservation list-to-send (FRLS) medium access control (MAC) protocol is proposed to apply to wireless networks with long propagation delay. In the protocol, a central control node (CCN) is applied to allocate the channel resources of two channels, and all the nodes transmit packets over the two channels without collision. Packet train transmission mechanism ensures that a number of packets are...
In this paper we focus on minimizing the long-term average power consumption of a single transmitter providing Quality of Service (QoS) enabled traffic to a single receiver. Both the transmitting and receiving stations are equipped with multiple antennas. First, we present a general {Kx M} system model where K is the number of independently buffered QoS streams and M is the number of parallel channels...
This paper proposes an efficient uplink scheduling algorithm that can perfectly support various VoIP CODECs with VAD/DTX/CNG in M-WiMAX considering the variants of silence duration between different voice users, solving the problems of uplink resources wastes and overwhelmingly large overhead that caused during silence period. In our proposed algorithm, efficient schemes is proposed to implement the...
Node cooperation has been demonstrated promising in ameliorating system performance for wireless networks. To effectively and efficiently provision quality-of-service (QoS) at the packet level in wireless mesh networks (WMNs) supporting heterogeneous traffic, medium access control (MAC)-layer resource allocation and service differentiation are imperative. In this paper, we propose a low-complexity...
We consider achieving max-min fairness in 802.11e based multi-hop wireless networks. We propose an approach which makes use of the TXOP mechanism in combination with an automatic contention window size tuning algorithm based on channel state sensing. Simulation results show that the proposed approach can provide a good approximation to per-flow max-min fairness and that this is achieved regardless...
Recently, there has been a growing interest in monitoring aqueous environments using Underwater Acoustic Sensor Networks (UASNs). In these networks, the Medium Access Control (MAC) protocols are responsible for coordinating the access from active nodes into the acoustic channel, which is characterized by high propagation delay and low data rate, which is challenging for system synchronization, energy...
The cooperative communication has recently gained momentum in the research community. This technique utilizes the notion of relay, as an intermediate node between the source and the destination, to enhance the overall system performance. In this paper we explored the benefits of adaptive cooperation, in which the relay adapts its relaying process in response to channel conditions and type of data...
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