Presence Of Partial-band Interference Research Articles

Leveraging spatial diversity to mitigate interference in underwater acoustic communication networks

Many acoustic channels suffer from interference which is neither narrowband nor impulsive. This relatively long duration partial band interference can be particularly detrimental to system performance. We survey recent work in interference mitigation and orthogonal frequency division multiplexing (OFDM) as background motivation to develop a spatial diversity receiver for use in underwater networks. The network consists of multiple distributed cabled hydrophones that receive data transmitted over a time-varying multipath channel in the presence of partial band interference produced by interfering active sonar signals as well as marine mammal vocalizations. In operational networks, many dropped messages are lost due to partial band interference which corrupts different portions of the received signal depending on the relative position of the interferers, information source and receivers due to the slow speed of propagation.

Signal Diversity Modification Method to Overcome Partial Band Interference in Frequency Hopping Spread Spectrum Communication System

In this paper, a cost effective solution is proposed toovercome the Partial Band Interference problem in FrequencyHopping Spread Spectrum (FHSS) communication system. Thenumber of Hops per symbol per bit parameter value is modifiedto develop the cost effective solution. The Bit Error Rate (BER)versus Signal to Noise Ratio (SNR) or Eb/N plot is taken toanalyse the FHSS communication system performance properlyin the presence of Partial Band Interference. The entire abovespoken FHSS communication system modelling, simulation andperformance analysis are implemented and analysed usingMATLAB.

Antijam performance of FFH/BFSK with noise-normalization combining in a nakagami-m fading channel with partial-band interference

The bit error rate (BER) performance of a noncoherent fast frequency-hopped binary orthogonal frequency-shift-keying (FFH/BFSK) spread spectrum noise-normalization combining receiver is evaluated in the presence of partial-band interference (PBI) and additive white Gaussian noise (AWGN) over independent frequency-nonselective slowly Nakagami-m fading channels. It is shown from the analytical results, and verified by simulation, that a higher diversity level greatly improves the worst-case performance of the noise-normalization receivers over Rayleigh or more severe fading channels, while a lower diversity level is preferred for less severe fading channels. In the former case, a full band strategy is optimal for the interferer and a partial-band strategy is more disruptive in the latter case

THE EFFECT OF PARTIAL BAND INTERFERENCE ON MULTI-CARRIER DS-CDMA SYSTEMS

ABSTRACTIn this paper, a multi-carrier signaling technique is applied to a direct sequence code division multiple access (DS-CDMA) system. This type of signaling has the desirable properties of lower chip rate, exhibiting a narrow band interference suppression effect, along with robustness to fading, without the need of either an explicit RAKE receiver or an interference suppression filter. Band limited spreading waveforms are used to prevent self-interference. The system performance over a frequency selective Rayleigh channel is evaluated analytically and through computer simulation, in the presence of partial band interference.

Optimal diversity allocation in multiuser communication systems. II. Optimization

For pt.I see ibid., vol.47, no.1828-36 (1999). In Part I, a class of multicarrier systems was proposed to study the effect of the method of diversity allocation on the performance of coherent multiuser communication systems operating over fading channels. In this paper, optimization over the proposed class of systems is considered for a fixed number of users per unit bandwidth. The first case studied is a system where the only noise not attributable to users in the system is additive white Gaussian noise. It is observed that either a system employing exclusive allocation, where users are allocated time-bandwidth resources that are not simultaneously shared with other users, or a system employing maximum resource sharing, where all users simultaneously share time-bandwidth resources, is optimal. Next, the preferable of these two extreme forms of resource allocation is determined. For any reasonable signal-to-noise ratio (SNR) and user density, it is shown that the system employing exclusive resource allocation is optimal in a single-cell environment with perfect subchannel separation at the receiver. Finally, the optimization is repeated in the presence of partial-band interference (PBI). Once again, either a system employing exclusive resource allocation or a system employing a maximum resource sharing scheme is observed to be optimal. The presence of the PBI increases the range of user densities and SNRs where a system employing a maximum resource sharing scheme is optimal, particularly when the probability of a particular time-bandwidth slot experiencing interference is high.

Analysis of a multicarrier DS-CDMA code-acquisition system

We present two code-acquisition schemes for a multicarrier direct-sequence code-division multiple-access system, one that uses equal gain combining and the other that uses selection combining. The code-acquisition performance of the two multicarrier systems, as well as that of a single-carrier system, are analyzed in both nonfading and Rayleigh fading channels under the assumption that the receiver is chip-synchronized; the effect of partial-band interference (PBI) on the performance is also included. It is demonstrated that in an additive white Gaussian noise channel, the single-carrier system has a better code-acquisition performance than both multicarrier systems. However, in a Rayleigh fading channel, the code-acquisition performance of a multicarrier system with equal gain combining is better than that of the single-carrier system, while a multicarrier system with selection combining has the same performance as the single-carrier system. Further, the presence of PBI more severely affects the code-acquisition performance of the single-carrier system than those of both multicarrier systems. Finally, the code-acquisition performance of a multicarrier system with equal gain combining is always better than that of the selection combining system.

Performance of multicarrier DS CDMA systems

In this paper, we apply a multicarrier signaling technique to a direct-sequence CDMA system, where a data sequence multiplied by a spreading sequence modulates multiple carriers, rather than a single carrier. The receiver provides a correlator for each carrier, and the outputs of the correlators are combined with a maximal-ratio combiner. This type of signaling has the desirable properties of exhibiting a narrowband interference suppression effect, along with robustness to fading, without requiring the use of either an explicit RAKE structure or an interference suppression filter. We use bandlimited spreading waveforms to prevent self-interference, and we evaluate system performance over a frequency selective Rayleigh channel in the presence of partial band interference; we also compare system performance with that of a single-carrier RAKE system.