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In this paper, we propose Opportunistic Carrier Prediction (OCP) that jointly addresses exposed terminal and hidden terminal problems in wireless networks. OCP is based on the rationale that past interference information can be a good indicator for the outcome of future packet delivery. Each OCP sender maintains a summary of past interference information and opportunistically accesses the channel...
This work evaluates opportunistic relaying in the presence of thermal noise as well as interference, when channel sensing is conducted reactively, in slow fading environments. The studied scenario employs a single gateway that provides access towards several destinations with weak links and exploits a network of intermediate relays. In sharp contrast to prior art, no inter-relay channel state information...
When both a high-priority and a low-priority system share a common frequency band, the low-priority station must sense the presence of the high-priority system, and if required, postpone its transmission or reduce its transmit power to avoid possible interference. To compensate, transmission opportunities of the low-priority system should be ensured as much as possible. Using a transmission scheme...
IEEE 802.22 is the first worldwide wireless standard based on Cognitive Radio (CR) for Wireless Regional Area Networks (WRAN). Usually, Secondary Users (SUs) have to be interrupted periodically for spectrum sensing so as to avoid interference to Primary Users (PUs) operating in the licensed bands. Such interruptions of data transmission, however, impair the Quality of Service (QoS) of SUs. Dynamic...
To maximize the gain of multi-hop transmissions, we have to let the number of hops as small as possible, decreasing multi-hop transmission delay. In this paper, we propose how the average number of hop counts can be reduced in wireless multi-hop networks by constructing a few long-range edges that can act as if they were highways in the networks. For this purpose, we adopt the concept of small-world...
The electromagnetic (EM) spectrum is the lifeblood of wireless communications and services. Accessing the spectrum has become ever-increasingly problematic. This is due to the current practices of frequency management based on pre-planned and static frequency allocation and assignments that can no longer accommodate explosive demands for EM spectrum. Without a paradigm shift in spectrum management,...
Cognitive radio (CR) is an effective technology for flexible utility of radio spectrum and has received increasing attention so far. To ensure reliable spectrum sensing, quiet periods (QPs) are allocated during which all secondary users cease transmission and perform spectrum sensing. Such that, regular transmission will be interrupted periodically and the system quality of service (QoS) could be...
The spectrum scarcity, which is a serious problem in wireless communication, shows the extreme importance of spectrum sensing technologies. For the traditional spectrum sensing algorithms, they are very difficult to have a good tradeoff between accuracy and simplicity. This paper is based on the application of Goertzel algorithm to the cyclostationary feature detector, which makes fast-searching and...
Ever since the Federal Communications Commision (FCC) announced that it would open the television (TV) spectrum for opportunistic access, there has been an increased interest in industry as well as academia to come up with proposals that would fit the criteria laid by FCC. To this end, IEEE 802.22 Working Group (WG) is formulating the first worldwide standard for cognitive radio to operate in the...
Distributed spectrum sensing (DSS) enables a Cognitive Radio (CR) network to reliably detect licensed users and avoid causing interference to licensed communications. The data fusion technique is a key component of DSS. We discuss the Byzantine failure problem in the context of data fusion, which may be caused by either malfunctioning sensing terminals or Spectrum Sensing Data Falsification (SSDF)...
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