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The transmitter side precoding shows excellent performance for multiuser multiple input multiple output (MIMO) wireless systems. However, joint transmitter and receiver design might achieve further improvement. The optimum precoding and decoding matrices can be solved iteratively. In this paper, we propose a modified joint iterative algorithm, based on minimum mean square error (MMSE) criterion in...
Cellular radio systems are often limited due to the presence of cochannel interference. Basically, radio systems may be operated by utilizing asynchronous or synchronous downlink transmission from all base stations in the system, where synchronization between terminals and their serving base station is mandatory in both concepts. We provide a comparison between the theoretical achievable spectral...
We propose a method for concurrent OFDM fine time synchronization to different stations with propagation delay differences, and a receiver based delay difference compensation method for MMSE channel estimation, which are needed to enable cooperative MIMO-OFDM transmission. Cyclic prefix removal is done dynamically with respect to the closest station, which allows for intersymbol interference free...
The complex sphere decoding algorithm has optimal bit error ratio performance for uncoded multiple-input multiple-output (MIMO) systems. The computational and hardware complexities of this algorithm increase significantly for detection of 64-QAM modulated signal streams. In this paper two modifications to the original sphere decoding algorithm are proposed that reduce both computational complexity...
The context of this paper is interception, thus nothing is known on emission. This paper addresses the problem of time-varying multiple input multiple output channel estimation and tracking with Kalman filter for Alamouti scheme. Generally, Kalman filter must be initialized by training sequences, but in interception systems, such sequences don??t exist. So, we propose in this paper to use blind source...
Breadth-first search sphere decoding (SD) is considered as one of the most promising methods for multiple-input multiple-output (MIMO) detection due to its low computational complexity, capability of providing fixed throughput and pipelining features. However, the performance of the conventional breadth-first search SD is significantly degraded if the number of candidate symbols kept at each level...
Multiple antennas are known to increase the link throughput by providing a multiplexing gain which scales with the number of antennas. Especially in cellular systems, multiple antennas can be exploited to achieve higher rates without the need for additional base station (BS) sites. In this direction, this paper investigates the multi-antenna capacity scaling in a cellular system which employs multicell...
A frequency offset estimation algorithm based on relativity of time-domain PN sequence is proposed in this paper. The form of this algorithm under multi-path fading channel is also given. The performance of the algorithm using different parameters is studied through theoretical analysis and simulation. The high performance of this algorithm using under both AWGN channel and multi-path fading channel...
In this paper, we introduce further our recently designed family of L2 orthogonal space-time codes for CPM. With their advantage of maintaining both the constant envelope properties of CPM, the diversity of Space-Time codes and moreover orthogonality, and thus reduced decoding complexity, these codes are also full rate, even for more than two transmitting antennas. The issue of power efficiency for...
In this paper we present the mutual information of a bit-interleaved V-BLAST space-time architecture. We assume interference cancellation by successive detection using MMSE equalizers without decoding of the channel codes. The mutual information is dependent on the MIMO channel realization and the detection order. However, the mutual information is very similar to that of an AWGN channel when plotted...
The purpose of the present paper is to investigate the MIMO performance of the L-band multi-port Eleven antenna. Both a single- and dual-polarized lab model are investigated, both having 4 ports per polarization. The 4 ports per polarization are normally combined in a 180 deg hybrid to produce sum and difference patterns, but we investigate them here as individual ports in an antenna for a MIMO system...
Standardization work is nearly complete on long term evolution (LTE) of the UMTS Terrestrial Radio Access and Radio Access Network which is aimed for commercial deployment in 2010. Goals for the evolved system include support for improved system capacity and coverage, high peak data rates, low latency, reduced operating costs, multi-antenna support, flexible bandwidth operations and seamless integration...
In smart antenna downlink systems, the beamforming is severely affected by antenna gain and phase mismatch as well as mutual coupling effects. We propose an eigen-structure based approach to estimate the gain and phase of each antenna sensor and mutual coupling coefficients between antenna sensors. By preprocessing the transmission signal in base station with the estimated parameters, the gain and...
Cognitive radio (CR) is currently being seen as the future for wireless communications. Fundamental to the operation of a CR is the detection of presence of legacy communication. Energy detector (ED) is a simple and effective signal sensing method. However, the ED requires accurate estimation of the noise power. Any error in the estimation, which is common in practice, affects its performance. In...
In order to detect the presence of the primary user signal, spectrum sensing is a fundamental requirement to achieve the goal of cognitive radio (CR). This ensures the efficient utilization of the spectrum. Cyclostationary detection is the preferred technique to detect the primary users receiving data within the communication range of a CR user at very low SNR. In this work, we investigate the performance...
Ultrawideband transmission systems have a potential of low complexity, low power consumption, and low cost. These properties and low emission levels make it well-suited for wireless body networks. We propose a special spread spectrum transmission technique with a novel comb filter based energy detection receiver. It can cope with the problems of multipath propagation, low SNR and strong narrow band...
Ultra-wide band (UWB) communication shows great potential for low-power communication for wireless sensor or body area network (BAN) applications. In particular, noncoherent receivers can be implemented with very low complexity. However, impulse radio and low duty cycle signaling involve stringent requirements on timing recovery. Standard synchronization algorithms might not be applicable due to constraints...
This contribution deals with the Turbo-like noncoherent data-aided (e.g., no blind) synchronization of Ultra-Wideband Impulse-Radio (UWB-IR) terminals operating over broadband channels affected by multipath fading with ??a priori?? unknown number of paths. The synchronizer we develop achieves the data-aided joint estimate of the number of paths and their arrival times without requiring any a priori...
In this paper we propose and analyze an approach to improve the convergence rate of blind equalizers for nonstationary signals using wavelet transformation. Transform domain adaptive filters are famous for their improved convergence rate over the conventional least mean square (LMS) algorithm and also facilities for noise reduction without giving much increase in the computational cost; on the other...
Time reversal (TR) is a transmission technique that relies on pre-processing the signal at the transmitter (TX) by filtering it through a filter, the impulse response of which is a time reversed and phase conjugated version of the channel impulse response (CIR) to the target receiver (RX). TR is known to have remarkable temporal and spatial focusing properties. Specifically temporal focusing indicates...
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