The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
In this paper we consider the coexistence issue between OFDM-based WLANs of the 802.11a family and time-hopping ultra wideband (TH-UWB) systems. A general analytical expression is provided for the bit error rate (BER) of the OFDM transceiver operating in the presence of UWB interference and the interferences caused by the multipath propagation phenomenon on the 802.11a OFDM signal, comprising intersymbol...
Cooperative wireless communications offers a new dimension of diversity by emulating transmit antenna diversity to provide reliable communications. In cooperative diversity, single-antenna radios behave as relays between a source and destination, and the performance improvements are due to cooperation of the source and the relay. However, a misbehaving relay can degrade the envisaged performance improvements...
This paper studies efficient complex valued matrix manipulations for multi-user STBC-MIMO decoding. A novel method called Alamouti blockwise analytical matrix inversion (ABAMI) is proposed for the inversion of large complex matrices that are based on Alamouti sub-blocks. Another method using a variant of Givens rotation is proposed for fast QR decomposition of this kind of matrices. Our solutions...
Adaptive ARQ is applied to a wireless network, altering retransmission policy according to content importance. By a video deadline-aware buffer discard policy, repeated transmission of expired packets and buffer overflow are mitigated, helping to maintain video quality. Multiple deadlines are applied according to picture type. The combined policy is demonstrated for a bluetooth piconet achieving fast...
Unequal error protection is the key to future transport of multimedia data. The paper presents an overview of some new approaches realizing UEP properties in physical transport, especially multicarrier modulation, or with LDPC and turbo codes. For multicarrier modulation, a UEP bit-loading method is described allowing for an arbitrary number of classes, arbitrary SNR margins between the classes and...
Due to resource constraints, digital image transmissions are a significant challenge for image sensor based wireless sensor networks (WSN). In this paper, we propose a novel robust and energy-efficient scheme, called image component transmission (ICT) in WSN by providing various levels of reliability during image transmissions. Essential components such as the information for the positions of significant...
In this paper, we propose a cognitive radio-based multi-user resource allocation framework for mobile ad hoc networks using multi-carrier DS CDMA modulation over a frequency-selective fading channel. In particular, given pre-existing communications in the spectrum where the system is operating, in addition to potential narrow-band interference, a channel sensing and estimation mechanism is provided...
In this paper, we investigate the SNR and BER performance of an OFDM system under imperfect synchronization which is caused due to noise, Doppler shift and frequency selective fades in the channel. An analytical expression for BER is derived assuming BPSK modulation and numerical results are presented to show the effect and extent of the above channel impairments in OFDM downlinks.
In this paper, we focus on the security issue of a chaotic digital communication scheme called chaotic-pulse- position modulation. We design a third party intrusion scheme to test to see if CPPM is as secure as is claimed. Experiments are conducted with various chaotic maps, where CPPM is used to modulate the message at the transmitter and a Kalman filter fed with a polynomial approximation is used...
In this paper, we clarify the properties of thirty FM family codes through analyses of their coding rules. We then investigate combinations of these codes with several PRML techniques by simulating bit error rates. The results show that nine FM family codes yield a better SNR than does the conventional FM code at the bit error rate of 10??4.
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.