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Modern communication system is restricted by the underwater communication. the underwater acoustic channel is probably one of the most complex environments for data communication, the main reasons of bit-error-rate in underwater acoustic communication are serious multipath fading and Dopppler shift, the direction of underwater acoustic communication's development is the data transmission with low...
In this paper, an adaptive path number selection mechanism is proposed to improve the accuracy of the frequency channel response obtained from the pilot-based channel estimation approach for QAM modulated MIMO-OFDM systems. The 2×2 space-frequency block code-dedicated short-range communication (2×2 SFBC- DSRC) system and a six-path channel model are considered as an example of the MIMO-OFDM system...
Many communication signals exhibit cyclostation-arity with some cycle frequencies and the cycle frequencies are related to signal parameters such as symbol rates, carrier frequencies. Dandawate proposed a statistical test to check the presence of cyclostationarity using a single cycle frequency. And recently, the statistical test has been applied to spectrum sensing. For most modulated communication...
This paper investigates the throughput performance of a CSMA/CA based network of land mobile radios (LMR) over a Rayleigh fading FM channel. The throughput calculations are based on the medium access (MAC)/physical (PHY) cross-layer characteristics for the distributed digital radios (DDR). From PHY-layer perspective, the effects of additive white Gaussian noise (AWGN), Rayleigh fading and push-to-talk...
Symbol rate is one of the most important parameters of digital modulation signals. The estimation of symbol rate is deeply researched by the use of the cyclic autocorrelation. The paper deduced that the amplitudes of MPSK signals’ cyclic autocorrelation values reach maximum when the delay was a half of the symbol rate, and then put forward a new algorithm of estimating symbol rate. Simulations show...
Orthogonal frequency division multiplexing (OFDM) is the modulation scheme of choice for digital video broadcasting-handheld (DVB-H), which is required to operate under high mobility conditions resulting in significant Inter-carrier Interference (ICI). To mitigate ICI, several cancellation schemes have been proposed but they require reliable channel information at the receiver which is quite challenging...
Orthogonal frequency division multiplexing (OFDM) is the modulation scheme of choice for digital video broadcasting-handheld (DVB-H) which is required to operate under high mobility conditions resulting in significant Inter-Carrier Interference (ICI). Under these conditions, the conventional one-tap per subcarrier channel estimation and equalization is suboptimal since it does not account for ICI...
This paper proposes a new space-frequency (SF) code construction scheme that can fully exploit both spatial and frequency diversities while providing great coding advantage and maintaining high bandwidth efficiency for MIMO-OFDM system operating in frequency-selective channels. The proposed SF code construction method is based on a class of trellis codes, where the trellis branches are labeled with...
This paper explores the attributes, layering models and objective functions in cross layer designs for mobile ad hoc wireless networks by taking all the statistical characteristics and constraints from the physical (PHY) layer, media access control (MAC) layer and network (NET) layer into consideration. This paper reviews the entire network optimization across all the PHY/MAC/NET layers. At the PHY...
Ultra-wideband (UWB) systems possess several distinct features such as very high data rate, large multipath or frequency diversity and improved ranging precision while requiring low-power low-complexity transceivers. Among the different modulation schemes, differential PSK is an attractive option because it does not require channel estimation, and hence reduces implementation complexity. This paper...
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...
While two-dimensional (2-D) orthogonal variable spreading factor (OVSF) codes were proposed for multicarrier direct-sequence code-division multiple-access (MC/DS-CDMA) systems in order to eliminate multiple-access interference, the number of orthogonal sequences (or code cardinality) was restricted by the number of carrier frequencies. Non-orthogonal 2-D frequency-time-spreading (FTS) codes were then...
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