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In this paper, we will propose a framework for computing detection (Pd) and false alarm (Pfa) probabilities for chip-time differential transmitted-reference (Tc-DTR) receivers over frequency-selective multipath fading channels further impaired by narrow-band interference (NBI). We will show that, when compared to similar non-coherent receiver architectures, Tc-DTR offers an intrinsic robustness to...
We consider a cognitive radio network in which a set of base stations make opportunistic spectrum access to support wireless subscribers within their covering cells. The spectrum of interest is divided into independent channels licensed to the primary users. Channel assignment and power control must be carried out in the cognitive network so that no excessive interference is caused to the primary...
Statistics that are obtained from the demodulator are used in a direct-sequence spread-spectrum receiver to provide an estimate of the signal-to-noise ratio. We evaluate the applicability to spread-spectrum multiple-access systems of an SNR estimator that was proposed previously for SNR estimation in systems for which the only disturbance is thermal noise. The proposed estimate does not require the...
As the world becomes increasingly dependent on dynamic and up-to-the-moment information, we recognize that broadband networks must be able to convey this information timely and wirelessly, to and from users in motion. Varieties of 802.11 compliant equipment and other types of broadband wireless equipment have been proposed for, and in some areas, being used to meet this need. There have been questions...
A critical aspect of spectrum sensing involves determining the number and type of transmitters in the band of interest. We present a technique that exploits a combination of temporal and frequency-based analysis to enable significantly more accurate frequency offset measurements than would be possible with frequency domain measurements alone, thus enabling improved RF fingerprinting for frequency...
This paper introduces and analyzes scale-time offset robust modulation (STORM) for use in code division multiaccess (CDMA) systems using spread quadrature phase shift keying (QPSK) to increase the capacity of a CDMA network. Since current commercial CDMA systems have dedicated spectrum, the capacity is primarily limited by the interference of other CDMA users; thus, power control and multiuser interference...
This paper considers a synchronous DS-CDMA system where channel state information at the base station is acquired via uplink training and channel feedback is used to provide the terminals with the optimal uplink signatures. We examine the tradeoffs involved in the proportioning of a resource block between training, data, and feedback symbols, with linear (matched filter and minimum mean-square error)...
In this paper, we present a single-carrier (SC) waveform with smart antenna and frequency domain equalization (FDE) technologies to effectively combat both urban multipath and radio interference. It is designed to be power efficient, spectrally efficient, high quality, and capable of operating at vehicular speeds with long range. It can work on a small form factor device to support transport of streaming...
We study a distributed algorithm for adjusting beamforming vectors in a peer-to-peer wireless network with multiple-input multiple-output (MIMO) channels. Each transmitter precoding matrix has rank one, and a linear minimum mean squared error (MMSE) filter is applied at each receiver. Our objective is to maximize the total utility summed over all users, where each user's utility is a function of the...
The techniques of Terminal transmit adaptation are critical for achieving maximal channel throughput when the link loss exhibits large variation. In this paper, some technical issues regarding transmit power control and mode adaptation in satellite communication (SATCOM) systems are addressed. The transmit adaptation is explored in terms of optimizing the link availability. The analysis extends the...
Dynamic spectrum access can enable secondary network users to access unused spectrum, or whitespace, which is found between the transmissions of primary users in a wireless network. The main design objectives for secondary user access strategy are to be able to ??scavenge?? spatio-temporally fragmented whitespace opportunities while limiting the amount of interference caused to the primary users....
Frequency hopping provides some protection against multiple access interference in random-access ad hoc networks. Power control and the use of short routing hops can further reduce interference by promoting spatial reuse. If the network is fully connected, frequency hopping and power control alone may be sufficient to allow good throughput without the use of routing. This approach is particularly...
We introduce complete analytical characterization of the nonlinear interference that results when passing more than one high-order modulation carrier through the same nonlinear transponder HPA. Based on this analysis, a novel Volterra filter is proposed that models nonlinear intersymbol interference (ISI) and adjacent channel interference (ACI). Our focus is on adaptive algorithms so that the solutions...
Efficient use of spectrum requires an accurate determination of interference effects. In this paper, we introduce a radio to radio (R2R) factor that quantifies the interference effects of one radio waveform on another based on multiple waveform properties instead of solely on intermediate frequency (IF) signal power. The R2R factor is formulated as a dimensionless correction term in the victims communication...
Cognitive radio (CR) is a revolutionary wireless mobile communication technology. Smart users can use the CR technology to sense the surrounding environment, search for available spectrum resources and access spectrum dynamically. Differential frequency hopping (DFH) is known as an effective FH technique for increasing data rate of HF communication system. In this study, the cognitive radio technology...
A key enabling functionality in implementing Cognitive Radio is to reliably detect the licensed users. In recent literature, cooperation among spectrum sensing terminals is suggested to offer reliable sensing performance. We consider the problem that the presence of malfunctioning or malicious sensing terminals will severely degrade the performance of cooperative spectrum sensing. In this paper, we...
A typical military airborne networking scenario involves small groups of relatively closely-spaced aircraft which fly as a unit to perform a common mission. These aircraft need to maintain very long data links with other aircraft in the presence of strong interference from hostile jammers. Due to the physical separation of the aircraft, the time difference of arrival can often be greater than the...
Active topology management in the future airborne networks (AN) can provide improved overall network throughput, efficiency, and scalability and is critical due to the high degree of platform dynamics involved. The RF links that form an airborne network must be established and reconfigured rapidly in response to aircraft joining and leaving the network, aircraft changing flight paths, and to changes...
We consider multi-constrained power, rate and channel allocation crafted for low power consumption, delay tolerant traffic, and under interfering link conditions that may be used in a cognitive radio system. Specifically, an iterative distributed algorithm, based on a sum-power constrained sum-rate maximization with upper (and lower) per user and channel power and rate constraints, as well as upper...
The capacity of a multipoint MIMO wireless network is interference-limited. In order to increase the system capacity, MIMO precoding at the transmitter and decoding at the receiver can be employed so that interference among different nodes is eliminated or suppressed. In this paper, we propose precoding/decoding techniques based on an iterative zero-forcing approach. By utilizing the extra degrees...
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