Diversity order analysis of orthogonal space–time block coding over keyhole fading channels with antenna selection

Summary The combination of Linear Dispersion Space‐Time Block Codes (LD‐STBCs) and Multiband Orthogonal Frequency Division Multiplexing Ultra‐WideBand (MB‐OFDM UWB) technologies has been proposed in the literature to improve the error performance and data rate. Recently, it has been shown that the LD codes allow the repetitions of data symbols conjugates. They cause a transformation of the Multiple‐Input Multiple‐Output (MIMO) channel that requires a Widely Linear (WL) filtering. However, proposed LD‐STBC MB‐OFDM UWB system does not take this issue into account. In this paper, we propose a Widely Linear Minimum Mean Square Error (WLMMSE) channel estimator for LD‐STBC MB‐OFDM UWB systems. The proposed channel estimator proceeds to WL estimation instead of linear one. Via simulation results, we prove that the LD‐STBCs provide significant performance gain for MB‐OFDM UWB system compared to Single‐Input Single‐Output (SISO) configuration. We show also that the proposed WLMMSE channel estimator outperforms the LMMSE one. This performance improvement is observed for both proper and improper signal constellations. Additionally, the computational complexity of our proposal is comparable with that of LMMSE estimator. Copyright © 2016 John Wiley & Sons, Ltd.

Section: Introductionmentioning

confidence: 99%

Widely linear channel estimation for LD‐STBC MB‐OFDM UWB systems

Hajjaj

Chainbi

Bouallègue

2016

“…A MIMO system is more beneficial than single-input single-output (SISO) [2] because of its reduction in transmit power and increase in channel capacity. Polarization diversity is a technique to improve spectrum efficiency in mobile communications using different frequencies of adjacent cell base stations [3], [4]. Therefore, several studies have been carried out to design MIMO antenna with different structures.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, several studies have been carried out to design MIMO antenna with different structures. Polarization diversity is a technique to improve spectrum efficiency in mobile communications using different frequencies of adjacent cell base stations [3], [4]. A printed antenna fed by coplanar waveguide (CPW) is one of the structures that have gained much interest in recent years.…”

Section: Introductionmentioning

confidence: 99%

Dual‐polarized MIMO antenna system for WiFi and LTE wireless access point applications

Moradikordalivand

Rahman

Leow

et al. 2014

In this paper, a dual-polarized multiple-input multiple-output (MIMO) antenna system suitable for indoor wireless access point is proposed. The presented MIMO antenna system consists of two coplanarwaveguide-fed monopole antennas with orthogonally polarized modes. According to the closely spaced structure of the MIMO antenna system, the mutual coupling between the ports is a big challenge. Therefore, a new structure of parasitic element is introduced in order to improve the mutual coupling between the ports. For the purpose of validating the simulated results, the antenna prototype has been fabricated and measured; the comparison of the results shows that there is an acceptable agreement between the measurement and simulation results. The proposed design covers the frequency bands of WiFi (2.4 GHz), Worldwide Interoperability for Microwave Access (2.3 and 2.5 GHz), and Long-Term Evolution (LTE; 1.5 and 2.6 GHz) applications with a reflection coefficient less than À10 dB and a mutual coupling coefficient better than À15 dB. The MIMO antenna system provides an envelope correlation coefficient less than 0.15, polarization diversity gain more than 9.985 dB, and quasi-omnidirectional pattern within the expected frequency band. In addition, LTE downlink throughput measurements show that the proposed antenna system delivers data rates close to the theoretical maximum for quadrature phase shift keying, 16 quadrature amplitude modulation (QAM), and 64-QAM modulations. coefficients (S 12 and S 21 ) without CSPE are above À9 dB, indicating low isolation between the ports. The coupling coefficients (S 12 and S 21 ) with CSPE are À17 dB, justifying that good isolation between ports has been achieved. S-parameter resultsIn order to validate the simulated results obtained from CST Microwave Studio, the prototype has been fabricated and measured. The performance of the fabricated antenna is tested using a vector network analyzer to determine the reflection coefficient, isolation, voltage standing wave ratio, and bandwidth of the proposed antennas as well their operating frequency. Figure 4. Parametric study on the gap between ring number 3 and stepped line.Figure 5. Simulated S-parameter of the proposed MIMO antenna (a) without CSPE and (b) with CSPE. 5 of 11 DUAL-POLARIZED MIMO ANTENNA SYSTEM

“…Spatial multiplexing enhances the capacity of a wireless communication system by increasing the data rate by a factor which is proportional to the minimum of the number of the transmit and number of receive antennas [1][2][3]. In a spatial multiplexing scheme, the transmitted data is first broken down into multiple substreams, and the substreams are simultaneously transmitted from multiple antennas over a MIMO channel.…”

Section: Introductionmentioning

confidence: 99%

“…The receiver processes the signal to recover the substreams and assemble the original transmitted data stream. Spatial multiplexing enhances the capacity of a wireless communication system by increasing the data rate by a factor which is proportional to the minimum of the number of the transmit and number of receive antennas [1][2][3].…”

Section: Introductionmentioning

confidence: 99%

Design of reduced complexity feedback precoding for MIMO‐OFDM

Ghirmai

2014

Beamforming technique is applied to significantly increase the performance of a MIMO system, if the channel information (CI) of the communication system is available at the transmitter. For the transmitter to obtain the entire CI, however, a considerable reverse-link bandwidth is required. To save the bandwidth, a limited-rate closed-loop system, therefore, uses a predetermined codebook which is derived from the CI. The codebook consists of a finite number of precoders out of which the index of the best one is transmitted from the receiver to the transmitter using only a few bits saving substantial bandwidth. However, the amount of bits that need to be fed back can still be significantly large for MIMO-OFDM systems when the precoding matrix index (PMI) for each subcarrier should be transmitted. Such per-subcarrier precoding scheme has high feedback overhead and also incurs huge computational cost to determine the best PMI for each subcarrier. We, therefore, propose a per-band precoding scheme that precodes a band (group) of subcarriers by only one precoder. More importantly, we develop, for the proposed per-band scheme, reduced-complexity precoding selection methods that lead to the design of efficient receivers. The effectiveness of the proposed scheme is investigated through computer simulations. 143When a MIMO transmitter obtains a channel information (CI), the performance of the communication system can be further enhanced [4][5][6]. The availability of the CI enables the transmitter to precode the data and beamform the transmitted signal in such a way that the signal eigen modes match to those of the channel modes [7]. Applying precoding decomposes the signal into orthogonal spatial eigen modes and it effectively decouples the channel into parallel subchannels that transmit independent signals. Such decoupling of the channel provides the ability to adapt the allocation of power to the eigen modes of the signal according to the strength of their corresponding channel modes [8,9]. Therefore, it is well known that precoding, or beamforming, along with an optimal power allocation scheme, water-filling, enables a MIMO system to achieve maximum capacity [10,11].In cellular time-division-duplex systems, the transmitter may be able to derive the forward CI, using the principle of reciprocity, from the estimates of the reverse channel. In cellular frequencydivision duplex systems, however, because reciprocity does not apply, the forward CI cannot be derived from the estimates of the reverse channel. An alternative approach would be to send back CI from receiver to transmitter over an additional reverse channel [12]. Feeding back the entire CI to the transmitter, however, would require a high-rate reverse channel which demands considerable additional transmission resource. Reducing the amount of feedback overhead has been a subject of a lot of research work, and, therefore, several methods have been proposed in the literature [13,14].A limited-feedback closed-loop MIMO system employs a codebook to represent the CI tha...