L.P. Linde

A cost-effective wideband MIMO channel sounder and initial co-located 2.4 GHz and 5.2 GHz measurements

A cost-effective, experimental MIMO channel sounder is presented, capable of performing measurements with up to eight transmit and eight receive elements over 80 MHz of system bandwidth. The system provides the wideband channel transfer matrix for both indoor and outdoor wireless communication scenarios, allowing direct measurement of key MIMO system parameters. The system is described, fundamental hardware building blocks are outlined, and post-processing data algorithms are presented. Initial investigations on the effect of frequency scaling and array configuration at 5.2 GHz and 2.4 GHz are also presented.

Bit error probability for a M-ary QAM OFDM-based system

Results and the general expression for the bit error rate (BER) of M-ary QAM for single carrier systems are well known, but are not readily available for M-ary QAM combined with orthogonal frequency division multiplexing (OFDM). In this paper, a generalized closed-form BER expression of M-ary QAM OFDM is empirically derived and verified in the presence of additive white Gaussian noise (AWGN), using a Monte Carlo simulation. Theoretical BER graphs up to 1024-QAM over up to 256 subchannels are also presented.

Turbo-coded/multi-antenna diversity combining scheme for DS/CDMA systems

In this paper the performance of a combined turbo coded and antenna diversity scheme to synchronous direct-sequence code-division multiple-access (DS/CDMA) communication over fading mobile radio channels is considered. Turbo codes have a built in structure that is suitable for diversity techniques to improve the quality of communications. The binary input data to a rate 1/(M+1) multiple turbo encoder produces M+1 coded bits, which, in turn, are assigned through suitable puncturing patterns to M different antennas and transmitted from each antenna simultaneously. The novelty of the transmission scheme, is that the original single-antenna rate-1/2 turbo coded system is transformed into a more powerful rate-1/(M+1) turbo code. The bit error rate performance of the proposed combined antenna and turbo coding diversity combining scheme is studied by means of simulation for a quadrature phase-shift keying (QPSK) DS/CDMA system on a non-frequency selective Rayleigh fading channel. Employing the turbo-coded/multi-antenna diversity combining scheme it is shown that lower bit error rate performance can be achieved, compared to a conventional single antenna scheme employing the same coding strategy.

On the convexity of the LCCM cost function for DS-CDMA blind multiuser detection

The linearly constrained constant modulus algorithm (LCCMA) applied to blind DS-CDMA multiuser detection was widely considered in the last few years. In some papers, global convergence of the linearly constrained constant modulus (LCCM) algorithm was incorrectly claimed, after which corrections were published by other authors (see the Introduction section for references). In this letter, analysis of the LCCM criterion is extended to prove convexity of the LCCM cost function between any point and the global minimum, subject to certain conditions, by using the definition of a continuous convex function.

Performance evaluation of a QPSK system employing complex spreading sequences in a fading environment

Due to the availability of potentially large sets of sequences with good correlation characteristics, the interest in the implementation of complex spreading sequences (CSS) in code division multiple access (CDMA) systems, has increased dramatically. In this paper, the simulated bit error rate (BER) performance of a synchronous balanced quadrature phase shift keying (QPSK) CDMA system, employing different classes of CSS, is presented for Gaussian and multipath fading channel conditions.

Fading correlation and its effect on the capacity of space-time turbo coded DS/CDMA systems

This paper considers the performance evaluation of a space-time turbo processing system employing a combined turbo coded and antenna transmission diversity scheme for DS/CDMA communication systems. In this combined coding/signalling scenario the turbo coder structure is exploited for a novel space-time processing approach. The binary input data to a rate 1/(M+1) multiple turbo encoder produces M+1 coded bits, which, in turn, are assigned through suitable puncturing patterns to M different antennas and transmitted from each antenna simultaneously. The novelty of the transmission scheme, is that the original single-antenna rate-1/2 turbo coded system is transformed into a more powerful rate-1/(M+1) turbo code. The bit error rate performance of a QPSK DS/CDMA system employing a short-frame space-time turbo-coded transmission scheme and RAKE diversity receiver is studied by means of simulation. It is shown that with the proposed system, employing M transmit antennas and an L-branch RAKE receiver, lower bit error rate performance can be achieved, compared to a conventional single antenna scheme. The latter results are achieved even in the presence of correlated fading conditions.

A class of bandlimited complex spreading sequences with analytic properties

This paper describes the construction and correlation properties of a new class of analytic, bandlimited complex (ABC) spreading sequences. The sequences are loosely based on the well known Frank-Zadoff-Chu (FZC) sequences and are constructed by placing some constraints on the phases of the FZC sequences. The new class of spreading sequences are shown to have analytical properties, while retaining reasonable correlation properties. In particular, the analytic properties of the sequences facilitate the use of spreading sequences with double the length in CDMA systems. Furthermore, the sequences have a constant signal envelope making them ideal for applications were a peak-to-mean signal power ratio of one is desirable.

Performance of a synchronous balanced QPSK CDMA system using complex spreading sequences in AWGN

Due to the availability of potentially large sets of sequences with good correlation characteristics, the interest in the implementation of complex spreading sequences (CSS) in code division multiple access (CDMA) systems, has increased dramatically. In this paper, the bit error rate (BER) performance of a synchronous balanced quadrature phase shift keying (QPSK) CDMA system employing different classes of CSS, is presented.

Power and spectrally efficient four-dimensional super-orthogonal WCDMA building block for next generation wireless applications

This letter introduces a versatile multi-code multidimensional super-orthogonal wideband code division multiple access (MC-MD-SO- WCDMA) multi-layered-modulation (MLM) scheme, employing families of root-of-unity filtered (RUF) generalized-chirp-like (GCL) constant-envelope complex spreading sequences (GCL-CE-CSS), including recently derived families of super-orthogonal (SO) GCL-CE-CSS with zero cross-correlation (ZCC) properties. The latter sequences facilitate multi-user-interference (MUI) free demodulation and detection. It is shown that the resulting MC-MD-SO-WCDMA signal simultaneously exhibits a spectrally efficient minimum (Nyquist) bandwidth output power spectral density (PSD) and a near constant instantaneous power output signal, yielding significant spectral and power efficiency advantages over existing single and multi-carrier multi-level quadrature-amplitude-modulated (M-QAM) WCDMA and OFDM modulation standards.

Performance evaluation of Viterbi decoded Reed-Solomon block codes in additive white Gaussian noise and flat fading channel conditions

Much attention has been given to the decoding of linear block codes by means of trellis decoding algorithms, such as the BCJR and Viterbi algorithms. Not only do these algorithms support soft input decoding, but also the application of channel state information for improved decoding performance in fading channel environments. This paper presents a performance evaluation, based on an extensive simulation study, of Viterbi decoded Reed-Solomon block codes under additive white Gaussian noise and flat fading channel conditions. Special attention is given to the influence of channel state information on the bit error rate performance of Viterbi decoded Reed-Solomon block codes in flat fading channels with varying Doppler frequencies and line-of-sight signal strengths.