MU-MIMO (Multi-User Multiple Input and Multiple Output) has been considered as a fundamental technology for simultaneous communications between a base station and multiple users. This is because it can generate a large virtual MIMO channel between a base station and multiple user terminals with effective utilization of wireless resources. As a method of implementing MU-MIMO downlink, Block Diagonalization (BD) was proposed in which the transmission weights are determined to cancel interference between multiple user terminals. On the other hand, Block Maximum Signal-to-Noise ratio (BMSN) was proposed which determines the transmission weights to enhance the gain for each user terminal in addition to the interference cancellation. As a feature, BMSN has a pseudo-noise for controlling the null depth to the interference. In this paper, to enhance further the BMSN performance, we propose the BMSN algorithm that has the pseudo-noise determined according to receiver SNR. As a result of computer simulation, it is confirmed that the proposed BMSN algorithm shows the significantly improved performance in evaluation of bit error rate (BER) and achievable bit rate (ABR).

In this paper, the optimum combination of optical pseudo-noise (PN) code and modulation scheme to achieve high total data transmission rate is presented. Moreover, the bit error rate (BER) performance of a wireless OCDMA system using chip-level detection is evaluated through theoretical analysis in the multi-user case. It is shown that, in a wireless OCDMA system with chip-level detection, the total data transmission rate of a multi-pulse pulse position modulation (MPPM) systems with optical pseudo-noise code generated by an M-sequence is better than that of an MPPM system with optical orthogonal code and that of an MPPM system with an extended prime code sequence. Moreover, the total data transmission rate of an MPPM/SIK system using modified pseudo orthogonal M-sequence sets can achieve more than 1.0 [bit/chip].

This paper proposes a channel estimation technique which uses a postfixed pseudo-noise (PN) sequence combined with zero padding to accurately estimate the channel impulse response for mobile orthogonal frequency division multiplexing (OFDM) communications. The major advantage of the proposed techniques is the periodical insertion of PN sequences after each OFDM symbol within the original guard interval in conventional zero-padded OFDM or within the original cyclic prefix (CP) in conventional CP-OFDM. In addition, the proposed technique takes advantage of null samples padded after the PN sequences for reducing inter-symbol interference occurring with the information detection in conventional pseudo-random-postfix OFDM. The proposed technique successfully applies either (1) least-squares algorithm with decision-directed data-assistance, (2) approximate least-squares estimation, or (3) maximum-likelihood scheme with various observation windows for the purpose of improving channel estimation performance. Some comparative simulations are given to illustrate the excellent performance of the proposed channel estimation techniques in mobile environments.

In this paper, we present a new approach to the construction of a set of binary sequences with a zero-correlation zone. The set consists of n pairs of binary sequences and the length of each binary sequence is n2(m+2) for some integers m and n. The Hadamard sequences with length n are used to construct the set. Any sequence in the set has 2(m+1) subsequences, each of length 2n. The author proves that any two subsequences are orthogonal if they belong to different pairs of binary sequences in the set.

A rapid Pseudo-Noise (PN) acquisition scheme is proposed. The proposed scheme consists of a phase alignment detector and Voltage Controlled Clock (VCC) loop. The VCC loop is used to control the phase update of the local PN signal. It has an auxiliary signal that provides the loop with two stable locking points as well as the direction of each phase update. The performance of the proposed scheme is evaluated by simulation. Results show that the proposed scheme acquires the phase two to three times faster than the conventional coherent serial scheme, and 1.5 times faster than of that in [10], at a small amount of additional hardware.

It is concluded from numerical examples for the well-known linear PN sequence families of a large range of periods that the mean-square cross-correlation value between sequences is the dominating parameter to the average signal-to-noise power ratio performance of an asynchronous direct-sequence (DS) code-division multiple-access (CDMA) system. The performance parameters derived by Pursley and Sarwate are used for numerical evaluation and the validity of conclusion is supported by reviewing the other related works. The mean-square periodic cross-correlation takes the equal value p (code period) for the known CDMA code families. The equal mean-square cross-correlation performance results from the basic results of coding theory.