This letter presents a requirement for a spatial correlation reduction to enhance 2×2 MIMO channel capacity, which considers variations in SNR and channel matrix components. The simulation results clarify that correlation reduction requirement of |γ_{s, max}|≤0.7 is effective to enhance channel capacity.

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In the wireless communications, packet collisions due to the interfering signals are significant issue. Since the wireless local area network (WLAN) may not detect packets collision while transmitting the signals, right/wrong of the reception will be judged by the reply of the acknowledgment (ACK) frame. Therefore, the WLAN of transmission efficiency is very low and approximately 60%. In this paper, a novel access control scheme is proposed for the collision detection which utilizes multiple-input multiple-output (MIMO) technology. The proposed scheme improves transmitting efficiency compared to the conventional scheme. Via a computer simulation, it is confirmed that the proposed scheme achieves the transmitting efficiency of over 90%.

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The use of variable-length error control codes is a natural choice in transmission systems with variable-length data sequences. These systems also employ constrained sequence codes (often called line codes) to ensure that the transmitted symbol sequence is balanced and contains sufficient timing information to facilitate reliable demodulation. We outline how low density parity check convolutional codes (LDPC-CC’s) can be integrated with guided scrambling (GS) constrained sequence codes in a manner that supports variable length sequences and limits the detrimental effects of error extension during GS decoding by placing the LDPC-CC decoder before the GS decoder within the receiver. We present spectra and bit error rate results that demonstrate the advantage of this approach.

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In this paper, space-time block coding (STBC) is applied to single-carrier distributed antenna network (SC-DAN). By using the frequency-domain STBC coded joint transmit/receive diversity (FD-STBC-JTRD) for the downlink while using the well-known frequency-domain space-time transmit diversity (FD-STTD) for the uplink, the diversity order is given by the product of the number of distributed antennas and that of mobile terminal (MT) antennas. It is shown by computer simulation that the downlink and uplink can achieve almost the same bit error rate (BER) performance and that by increasing the number of distributed antennas, the BER performance can be significantly improved while keeping the MT complexity low.

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We propose an intra-node arrayed optical amplifier (AOA) to improve the OSNR of received signals by reducing the insertion loss of multi-degree ROADM nodes. Our AOA shares a pump laser between several EDFAs with the aim of reducing the module size and manufacturing cost compared with the size and cost when only arraying discrete EDFA modules. We confirmed the feasibility of our fabricated AOA experimentally. The experimental results show that the pump power was properly distributed to each EDFA and the OSNR of the received signals was successfully improved for 128-Gbit/s PDM-QPSK signal transmission systems.

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In this paper, a novel ICI reduction technique, with the combination of RF delay circuit and simple digital signal processing, is proposed. Proposed OFDM is compatible to existing OFDM systems and has 100% frequency efficiency. BER performance of proposed system is analyzed under the indoor multipath channel of 60GHz by computer simulation. Simulation results in LOS multipath channels shows proposed technique enables BER of 1.0E-05 without forward error correction (FEC) for both QPSK and 16QAM modulation schemes under the presence of phase noise and frequency shift.

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Cooperative spectrum sensing can detect the primary signal more reliably via exploiting spatial diversity, which usually requires extra common reporting channel for cognitive radios to exchange local sensing decision. In this letter, we propose a conservative cooperative spectrum sensing scheme, which can utilize the licensed channel for transmitting local sensing decision with limited interference to primary users. The new scheme can save the common reporting channel without sacrificing ROC performance and mitigate total interference probability compared with conventional cooperative sensing scheme.

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