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The VST-TDMA access protocol has shown to have many advantages over existing protocols in centralized (star) wireless network architectures. As most data-link layer protocols, it does not have a recovery feature as data integrity is supervised by the connection-oriented transport protocols. Nevertheless, VST-TDMA possesses the flexibility to easily incorporate a retransmission feature that allows...
In this paper, we improve throughput performance of a cognitive radio network through a proposed dual-level sensing strategy. Throughput performance of secondary users cannot be enhanced while providing higher priority to protect primary users from secondary user interference. Therefore, we propose a novel multiple access scheme based on dual-level sensing strategy by which both the interference protection...
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...
In this paper we treat the problem of identification of a subset of active users in a set of a large number of potentially active users. The users from the subset are activated randomly, such that the access point (AP) does not know the subset or its size a priori. The active users are contending to report their activity to the AP over a multiple access channel. We devise a contention algorithm that...
In this paper, we attempt to improve the efficiency of random access employed for a massive number of energy-constrained M2M devices to transmit their data to a base station (BS) by exploiting relaying and interference cancellation (IC). Each device transmits a single packet with a minimum required power, which is then forwarded by surrounding relay(s) to derive a benefit of IC at BS. While IC can...
Access reservation based on slotted ALOHA is commonly used in wireless cellular access. In this paper we investigate its enhancement based on the use of physical-layer network coding and signature coding, whose main feature is enabling simultaneous resolution of up to K users contending for access, where K ≥ 1. We optimise the slot access probability such that the expected throughput is maximised...
We consider a multiple access communication system where multiple users share a common collision channel. In this system, coordination among users is essential to resolve collision issues. However, each system user can only observe its own local traffic and the feedback from the channel. Without a centralized controller, it is challenging to design an efficient coordination protocol. We present a...
The cognitive radios (CR) utilize the spectrum resource without interfering the primary users (PU). Spectrum sensing, by which CR users detects the radio environment, is a critical technique in cognitive radios. Various collaborative spectrum sensing schemes are proposed to either improve sensing sensitivity or to reduce the sensing duration. However, most of the previous studies have not investigated...
In this paper, a modified S-MAC protocol incorporating a new back-off mechanism applicable to body sensor networks (BSNs) is proposed. The proposed protocol alleviates the drawback associated with the back-off mechanism which is currently utilized in the original S-MAC protocol in addition to its derivatives. Also, the cross-layer technique is used so as to achieve a better energy consumption and...
Spatial diversity for wireless transmission requires more than one antenna at the transmitter. However, mobile devices are usually limited by size, so installation of multiple antennas increases the hardware complexity significantly. Due to the omnidirectional nature of wireless signal, a data transmission between a source node and a destination node can be overheard by many other neighbor nodes....
We consider distributed detection applications for a fusion center that has a limited time to collect, weight and fuse local decisions to produce a global decision in a wireless sensor network that uses a random access protocol. When this time is not long enough to collect decisions from all nodes in the network, a strategy is needed for collecting those with the highest reliability. This is accomplished...
Random access techniques have traditionally been used for the design of efficient medium access control protocols for wireless networks where the entire bandwidth is provided to the users as a single channel to be accessed for communication. In this paper we analyze the broadcast performance of several random access techniques in a multi channel system, where users can dynamically access portions...
This paper considers the scenario in which a set of nodes share a common channel. Some nodes have a rechargeable battery and the others are plugged to a reliable power supply and, thus, have no energy limitations. We consider two source-destination pairs and apply the concept of cognitive radio communication in sharing the common channel. Specifically, we give high-priority to the energy-constrained...
This manuscript proposes a media access control method for a multipoint cyclic data gathering system, in which each node transmits its data to a base-station periodically. In the proposed method, by broadcasted ACK/NACK signals form the base-station, assignment of a proper time slot for each node is ensured once the node succeeds to transfer its data. As a solution of the difference of channel characteristic...
A critical shortage of spectrum resources and the underutilization of the licensed spectrum urge people to discover new approaches to efficiently utilize the spectrum resources. Opportunistic spectrum access (OSA) has been considered to be a good approach to exploit spectral resources and improve licensed spectral utilization. In this paper, based on this idea, we model and analyze one type of network...
Reliable event delivery at MAC, routing and transport level has been explored to great extent to provide improved throughput and route resilience in wireless sensor networks. The evolution of wireless sensor and actor networks (WSAN) have posed an extra constraint in terms of reliable event response. The reliable response is defined as the the in time event delivery from sensor nodes to actors and...
In multi-interface multi-channel (MIMC) based tactical ad hoc networks, QoS support is one of the main challenging issues for multi-hop transmissions. To support QoS in such a harsh environment, we propose a novel MAC scheme to minimize multi-hop as well as per-hop delay. The current IEEE 802.11 MAC protocols should contend to reserve the channel resource at every hop by each sender. The every-hop...
There are real challenges in both the IEEE 802.11 wireless local area network (WLAN) protocol and the medium access control (MAC)-functions providing the required quality-of-service, high throughput and minimum latencies. The IEEE 802.11 layer supports both the distributed coordination function (DCF) and the enhanced DCF (EDCF). The different access categories (AC) within the EDCF can enhance the...
Underwater acoustic networks (UWANs) have emerged as the primary tool to monitor and act upon the well-being of marine environment. However, the significantly slower propagation speed of acoustic signals, in contrast to RF signals, introduces the spatio-temporal uncertainty, which makes existing medium access control (MAC) solutions for terrestrial RF wireless networks unsuitable for UWANs. In this...
The Cognitive Radio (CR) technology is proposed for solving the spectrum underutilization problem and has gained great attention. By allowing unauthorized users to opportunistically access frequencies authorized to specific networks (called primary networks), the CR technology can increase the bandwidth utilization of the radio spectrum in a global perspective. In, the authors proposed a MAC protocol...
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