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In this paper, we propose novel criterion and novel power control schemes based on the capacity conservation ratio (CCR) by taking the Rayleigh fading effect into account using theoretical analysis. The CCR is defined as the ratio of the decreased capacity in the spectrum sharing to the original capacity of a system. We utilize the CCR as a novel metric for protecting a primary system (PS) from large...
This paper mostly concerned with the various packet size effect on performance of erasure correctable codes for cognitive radio. Among these types of codes we tried to simulate Raptor code to discover its suitability for assumed erasure channel in cognitive radio. The main target after supporting the functionality of coding-based cognitive radio would be finding the appropriate packet length that...
Cognitive radio is considered as the highly promising solution to the shortage problem of the frequency resource. In this report, we propose the dual-stage spectrum detection method for achieving the wideband, fast, and wide-dynamic-range spectrum detection. In addition, the success probability of detecting the vacant frequency spectrum and the detection time of it are evaluated by computer simulation...
This paper presents a new spectrum sensing scheme using an energy detector and multiple antennas. This scheme helps us finding the low level signals to realize a spectrum sharing in a primary and secondary system. The spectrum sensing by using multiple antennas has a problem that the channel state information of the primary signal is required for obtaining the diversity gain. However, the primary...
This paper evaluates the co-existence of a sensing information collection method, which collects the cooperative sensing information by using frequency based orthogonal narrow band signal overlaying to a primary system. In general, the cooperative sensing information is collected to a master node by using a different common channel with the primary system. However, the common channel decreases the...
This paper focuses on a primary and secondary spectrum sharing system with a modified MAC protocol at the secondary network. The assumed primary system is the wireless LAN (WLAN) operated with the protocol of IEEE 802.11 distributed coordination function (DCF). In such spectrum sharing system, it is required that the primary system is protected from the signals of the secondary system. In this paper,...
Cognitive radio system shares the frequency spectrum with the license system. As a result, the dramatic improvement of the frequency usage efficiency can be expected. Since the cognitive radio system is independent from the license system, it should recognize the wireless communication parameter of the license system, such as frequency, modulation scheme, and so on. Multiple-input multiple-output...
In the dynamic spectrum access (DSA) type of cognitive radios, secondary users need to detect the signals from the primary system prior to communicating in the sharing band. Hence, spectrum sensing is an important function for DSA. Key requirements for spectrum sensing in realistic radio environments are stable performance in detecting the primary signals as well as robustness against noise uncertainty...
Cognitive radio offers a tempting solution to increase the spectrum usage efficiency by proposing opportunistic usage of frequency bands among licensed users and secondary users. This paper focuses on mitigating the interference that may occur when the secondary user is unaware of the primary user's active period; known as hidden terminal problem. Path attenuation and shadowing effect are also considered...
In wireless ad hoc networks, the wireless link SNR varies due to fading after determining a multi-hop route. This causes a temporary link error and blocks the multi-hop packet transmission. A cognitive temporary-bypassing method and its protocol are proposed to improve transmission quality in wireless ad hoc networks. Packet success probability with this method has been analyzed for Rayleigh faded...
In this paper, we propose a soft decision based cooperative sensing method for cognitive radio (CR) in ad-hoc networks. A CR can sense a surrounding radio environment and adapt to the environment by the reconfigurability to achieve more effective frequency utilization. Observing the environment, CR should detect presence or absence of primary user and exploits this information to opportunistically...
The cognitive radio is a secondary wireless communication system that can overlap the frequency band assigned to the primary system by recognizing the frequency status. Ad-hoc cognitive radio is considered for realizing the cognitive radio by using multi-hop communication networks without giving the large interference toward the primary system. We have proposed the STBC distributed ARQ system applied...
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