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In cognitive radio networks, dynamic spectrum access is achieved by allowing secondary users (SUs) to probe the spectrum and utilize available channels opportunistically. Spectrum probing mechanisms should be efficient and fast to avoid harmful interference with primary users (PUs). Periodic probing has been commonly adopted as a default spectrum probing mechanism. In this paper, we attempt to study...
We present an analytical framework to assess the effectiveness of different combinations of medium access control (MAC) protocols for multichannel opportunistic spectrum access (OSA) ad hoc networks. As a performance metric we focus on average link layer throughput, and investigate dedicated control channel (DCC) and hopping control channel (HCC) MAC protocol abstractions. For DCC and HCC protocol...
Opportunistic Spectrum Sharing (OSS) has recently attracted increasing interest. We analytically model a wireless network that allows opportunistic spectrum sharing and analyze its performance through a queueing theoretic framework. The OSS system consists of the secondary users opportunistically sharing a set of spectrum resources with the primary users over a coverage area. The secondary users equipped...
The IEEE 802.15.4 standard is poised to become the global standard for low data rate, low energy consumption wireless sensor networks (WSN). By assigning the same sets of contention access parameters for all data frames and nodes, the contention access period (CAP) of the slotted IEEE 802.15.4 medium access control (MAC) currently provides a priority-independent channel access functionality and no...
We provide a simple and accurate analytical model for multi-cell IEEE 802.11 WLANs. Our model applies if the cell radius, R, is much smaller than the carrier sensing range, Rcs. We argue that, the condition Rcs >> R is likely to hold in a dense deployment of access points (APs). We develop a scalable cell level model for such WLANs with saturated nodes as well as for TCP-controlled long file...
In this paper, we will investigate the spectrum handoff schemes for the cognitive radio networks. Spectrum handoff occurs when the primary users appear and the secondary users are using this particular primary user's licensed channel. We compare two major types of spectrum handoff schemes. One is the reactive-sensing spectrum handoff, where the target channel for spectrum handoff is selected or sensed...
A random periodic spectrum sensing scheme is proposed for cognitive radio networks. The sensing period is extended to a general form as a random variable. A generalized Markov analytical model for sensing period optimization is presented, and the optimal sensing period to maximum rewards generated by the channel is derived. Numerical examples show that sensing period does affect the maximum rewards...
This paper analyzes the performance of a MAC scheme for low-rate wireless sensor networks that makes use of distributed queues to improve radio channel utilization. Analytical values first for the throughput performance, and later for the energy consumption are derived as a function of the system parameters. The obtained results show that the proposed scheme outperforms IEEE 802.15.4 MAC in terms...
Cognitive radio technology necessitates accurate and timely sensing of primary users' activity on the chosen set of channels. Reduction of sensing error may be accomplished through random selection in which idle and active channels are assigned different probabilities of being selected for sensing. The paper presents a probabilistic analysis of this policy and investigates the range of values in which...
Two critical issues in wireless sensor networks are cooperation of nodes and the limited availability of energy within network nodes. A widely employed energy-saving technique is to place nodes in sleep mode, corresponding to low-power consumption as well as to reduced operational capabilities. This causes a node may try to maximize the benefits it gets from the network without participating to its...
This paper proposes a decentralized cognitive radio based multi-channel MAC protocol for dynamic access spectrum (DSA) networks. In our proposed MAC protocol, each secondary user is equipped with a cognitive radio-based transceiver and multiple channel sensors. With the help of the two-way handshakes of control packets, the proposed MAC protocol enables the secondary users to opportunistically utilize...
Cognitive radio (CR) has the potential for resolving the spectrum scarcity issue in wireless communications. A CR device can establish unharmful links in the spectrum of the legacy system. Among many enabling functions for CR, spectrum handoff can restore CRpsilas connection when the primary user appears in the occupied channel. In this paper, we study three types of spectrum handoff for the link...
In this paper, we address the issue of transmission power control (TPC) in wireless ad hoc networks. Power control plays an important role in energy saving and network performance enhancement. However, the existing TPC schemes either face the problem of hidden and exposed terminal or have additional hardware requirements. We propose a novel distributed power control protocol, called Receiver Initiated...
In this paper, we propose an enhancement to the IEEE 802.11 distributed coordination function (DCF). The enhancement improves the level of channel spatial reuse; thus, it improves overall network data throughput in dense deployments. Our modification, named the location-enhanced DCF (LED), incorporates location information in DCF frame exchange sequences so that stations sharing the communication...
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