Presence Of Strong Co-channel Interference Research Articles

Blind Equalization in the Presence of Co-channel Interference Based on Higher-Order Statistics

An improved blind channel equalization method is proposed based on the generalized eigenvector algorithm (GEA) in this paper. This new method can blindly equalize the desired signal in the presence of strong co-channel interference. The basic idea underlying the improved GEA method is that higher-order cumulants can be sensitive to frequency offset. By exploiting this property of higher-order statistics, blind equalizer can be designed to equalize the desired signal with known frequency offset while suppressing the interference with a different frequency offset. Simulation results are shown to demonstrate the effectiveness of the proposed method.

Blind User Detection in Doubly Dispersive DS/CDMA Fading Channels

In this work, we consider the problem of detecting the presence of a new user in a direct-sequence/code-division-multiple-access (DS/CDMA) system with a doubly-dispersive fading channel, and we propose a novel blind detection strategy which only requires knowledge of the spreading code of the user to be detected, but no prior information as to the time-varying channel impulse response and the structure of the multiaccess interference. The proposed detector has a bounded constant false alarm rate (CFAR) under the design assumptions, while providing satisfactory detection performance even in the presence of strong cochannel interference and high user mobility.

Wimax Performance Impacts in Multi-Cell Deployments

This paper presents the application of the multiple antenna schemes beamforming (BF) and Multiple Input Multiple Output (MIMO) in the broadband wireless access system WiMAX. The evaluation considers the competing performance demands on link robustness and peak data rate. Configurations for both uplink and downlink are discussed. We conclude that future wireless communications will rely on diverse and adaptive multiple antenna schemes to meet their requirements, in particular in the presence of strong co-channel interference.

Spatio-temporal channel identification and equalization in the presence of strong co-channel interference

We address the problem of identifying and equalizing communication channels in the presence of strong co-channel interference (CCI). In this paper, we consider the interference and noise as colored noise with unknown covariance. In addition to the finite alphabet property of the information sequence and the inherent algebraic structure of the data model, we show empirically that potential improvement in sequence detection and channel estimation accuracy can be achieved from temporal diversity where the channel outputs are observed from a tapped delay line. To exploit these underlying structures and constraints under a common framework, the proposed algorithm optimizes a weighted least-squares cost function using an iterative re-weighting alternating mimization procedure. Numerical examples are presented and show that the proposed algorithm is capable of achieving reliable channel identification and equalization in the presence of strong CCI at moderate SNR.

Adaptive detection for shallow-water acoustic telemetry with cochannel interference

Adaptive decision feedback equalization (DFE) has recently been used to enable high-rate data transmission through shallow-water acoustic channels. This adaptive receiver successfully tracks and suppresses intersymbol interference due to a dispersive multipath channel. However, acoustic modems which are used for network applications must also contend with interference due to cochannel signals from proximal modems. In this work, we propose and evaluate a multiuser receiver with cochannel interference suppression. The advantages of this multiuser receiver in the presence of strong cochannel interference are shown by a performance comparison to a bank of the single-user DFEs described above. Conclusions are supported in part by the demodulation of experimental data for two simultaneous cochannel signals and by a steady-state performance analysis.

Adaptive processing of communication signals in shallow water acoustic telemetry networks

Underwater acoustic communications have received much attention in recent years leading to the development of powerful and reliable receiver algorithms for signal processing in a variety of ocean environments. With the feasibility of high-speed coherent underwater communications established, the focus of current research is shifting to more demanding communication scenarios, as encountered in underwater acoustic networks. The problem of signal detection in highly variant shallow water environments, in the presence of strong cochannel interference from other acoustic modems in the network is addressed. The signals of different users occupy the same bandwidth, making the respective channel responses and the underlying data symbols sequences the only distinction among distorted replicas observed at the receiver. The performance of a single-sensor decision-feedback equalizer (DFE) is compared to the performance of a centralized multiuser receiver that jointly performs adaptive equalization and interference cancellation, and a decentralized multi-sensor DFE that performs spatial signal combining and multichannel equalization. Performance at different receiver structures was tested on real data collected at a one-mile range in the Woods Hole harbor, from two closely separated sources. Excellent results were obtained at signal-to-interference ratios as low as −10 dB, showing the performance improvement of proposed techniques over DFE in a network scenario.