STBC

Diversity methods provide the receiver with independently faded copies of the transmitted signal with the expectation that at least one of these replicas will be received correctly. There are ranges of techniques available through which these faded copies can be recovered and used as part of arrangements for better reception. This paper proposes a method based on Space-Time Block Coding (STBC) with Multiple-Input Single-Output (MISO) and Multiple-Input Multiple-Output (MIMO) set-up for use in wireless channels. A special version of STBC called Alamouti code is used for exploiting the performance of MISO and MIMO in frequency-selective fading environment. Performance differences are observed with and without STBC in frequency selective faded channels. A comparison is made between the diversity gain of MISO and MIMO systems in terms of BER for two specific modulation schemes, namely BPSK and QPSK. The obtained results demonstrate that spatial diversity along with the power of STBC significantly improves the error performance in frequency selective wireless fading channels.

In this paper, Space Time Block Code (STBC), Spatial Multiplexing (SM) and hybrid model with OFDM are designed for Rayleigh fading channel. Combination of SM and STBC forms hybrid MIMO model. The performances of the above mentioned models with different modulations such as Quadrature Phase Shift Keying (QPSK) and Quadrature Amplitude Modulation (QAM) with multiple antennas are measured with respect to BER. In this paper, it is shown that Hybrid MIMO provides low BER. Thus, in wireless communication, hybrid model improves the data rate and link reliability.

The IEEE 802.16 standard is often referred to as WiMAX today. It represents a distillation of the most advanced technology and an industry consensus permitting equipment interoperability. It holds the promise of delivering high speed internet access to business and residential customers and to remote locations where traditional broadband services are unavailable. In the present work, the PHY specified for the Wireless MAN-OFDM case is studied and implemented. Various modulation techniques involved are explored and each of the performances enhancing techniques is evaluated with regard to its functionality in the system. The simulation results show that the Space-Frequency Coded system coupled with Reed-Solomon codes and Convolutional codes efficiently exploits diversity techniques.

This paper presents the bit error rate performance of the low density parity check (LDPC) with the concatenation of convolutional channel coding based orthogonal frequency-division-multiplexing (OFDM) using space time block coded (STBC). The OFDM wireless communication system incorporates 3/4-rated convolutional encoder under various digital modulations (BPSK, QPSK and QAM) over an additative white gaussian noise (AWGN) and fading (Raleigh and Rician) channels. At the receiving section of the simulated system, Maximum Ratio combining (MRC) channel equalization technique has been implemented to extract transmitted symbols without enhancing noise power. Keyword: AWGN LDPC MRC OFDM STBC

Multiple-input–multiple-output (MIMO) wireless systems use multiple antennas at transmitting and receiving end to offer improved capacity and data rate over single antenna systems in multipath channels. In this paper we have investigated the Spatial Multiplexing technique of MIMO systems. Here different fading channels like AWGN and Rician are used for analysis purpose. Moreover we analyzed the technique using high level modulations (i.e. M-PSK for different values of M). Detection algorithms used are Zero- Forcing and Minimum mean square estimator. Performance is analyzed in terms of BER (bit error rate) vs. SNR (signal to noise ratio).

The consistent demand for higher data rates and need to send giant volumes of data while not compromising the quality of communication has led the development of a new generations of wireless systems. But range and data rate limitations are there in wireless devices. In an attempt to beat these limitations, Multi Input Multi Output (MIMO) systems will be used which also increase diversity and improve the bit error rate (BER) performance of wireless systems. They additionally increase the channel capacity, increase the transmitted data rate through spatial multiplexing, and/or reduce interference from other users. MIMO systems therefore create a promising communication system because of their high transmission rates without additional bandwidth or transmit power and robustness against multipath fading. This paper provides the overview of Multiuser MIMO system. A detailed review on how to increase performance of system and reduce the bit error rate (BER) in different fading environmen...

In this thesis, the use of Space-Time Block Coding for the spectral co-existence of primary and secondary users in slow Rayleigh fading 2x2 cognitive radio channel employing asymmetric transmitter cooperation has been investigated, in favour of increasing spectral efficiency subject to some specific conditions. It is assumed that the primary channel is SISO throughout the thesis and the secondary is a MISO and MIMO channel in turn adopting spectrum overlay approach for co-existence. In other words, 2x2 SISO-MISO and SISO-MIMO cognitive radio channels have been investigated for spectrum sharing using overlay approach. In this context, by generalising the 2x2 cognitive radio channel, information theoretic achievable data rates by using the spectrally active regions of the radio spectrum in addition to inactive parts when available, for SISO-SISO, SISO-MISO, SISO-MIMO channel cases. Besides, the ergodic and outage capacity of the Space-Time Block Codes have also been investigated for various transmitter-receiver antenna configurations. Finally, the use of Space-Time Block Coding for spectrum sharing in SISO-MIMO cognitive radio channels have been investigated and the bit error rates for the secondary users have been obtained through software simulations, subject to coexistence-conditions.

ABSTRACT Orthogonal space-time block codes (STBCs) are known to orthogonalise the multiple-input multiple-output (MIMO) wireless channel, thus reducing the space-time vector detection to a simpler scalar detection problem. The capacity of STBCs over correlated Rayleigh and Ricean flat-fading MIMO channels under different adaptive transmitting techniques is studied. Three adaptive schemes known as optimal power and rate allocation, total channel inversion with fixed rate policy and its truncated variant are studied. Taking into account the effect of channel correlation, closed-form expressions are obtained for the capacity of orthogonalised Rayleigh and Ricean MIMO channels under these adaptive transmission techniques in order to avoid Monte-Carlo simulations

Almouti published the error performance of the 2x2 space-time transmit diversity scheme using BPSK. One of the key techniques employed for correcting such errors is the Quadrature amplitude modulation (QAM) because of its efficiency in power and bandwidth.. In this paper we explore the error performance of the 2x2 MIMO system using the Almouti space-time codes for higher order PSK and M-ary QAM. MATLAB was used to simulate the system; assuming slow fading Rayleigh channel and additive white Gaussian noise. The simulated performance curves were compared and evaluated with theoretical curves obtained using BER tool on the MATLAB by setting parameters for random generators. The results shows that the technique used do find a place in correcting error rates of QAM system of higher modulation schemes. The model can equally be used not only for the criteria of adaptive modulation but for a platform to design other modulation systems as well.

Cooperation diversity schemes employing space-time block coding (STBC) techniques have been proposed for wireless networks to increase systems capacity and coverage, by allowing multiple relay nodes distributed in space to assist the transmission between a given pair of terminals. Conventional relaying strategies, such as amplify-and-forward (A&F) and decode-and-forward (D&F), are designed by considering unidirectional communications via relays, which are referred to as one-way relay channels. Recently, it has been shown that, when there is consistent traffic in both directions, the use of two-way relaying protocols, which explicitly account for the bidirectional nature of the data flow, can potentially improve the network performance. In this paper, capitalizing on randomized STBC, a coding rule which has been originally developed for D&F one-way relay channels, fully decentralized cooperative communication schemes are proposed for both A&F and D&F relays, where each relay is unaware of both the effective STBC being employed by the other nodes and the number of cooperating stations. Numerical results are provided to highlight the effectiveness of the proposed two-way relaying schemes in comparison to their one-way counterparts.

Cooperative Relaying is deemed as one of the most promising techniques in the current research in terms of providing superior space coverage and robust performance. In this paper, we focus on cooperative wireless networks employing Space Frequency Block ...

Wireless designers constantly seek to improve the spectrum efficiency/capacity, coverage of wireless networks and link reliability. In this direction, Space-time wireless technology that uses multiple antennas along with appropriate signaling and receiver techniques that offers a powerful tool for improving the wireless performance is used in this thesis work. A special version of STBC called 'Alamouti code' is used. PSK modulation scheme is used for modulation of data. In this thesis work, the Space-Time Block Codes (STBC) is used in WLAN wireless network that uses multiple numbers of antennas at both transmitter and receiver. The STBC which includes the Alamouti Scheme for 2 transmit antenna and a different number of receiving antenna has been studied, simulated and analyzed. The simulation has been done in MATLAB. Throughput and several parameter performance has been analyzed using the MATLAB.A sample image is transmitted to compare the performance of various parameters like RMSE, PSNR, MAE etc. All the parameters are plotted against SNR (in dB) values ranging from-18 to 30. Various observations being made for the improvement in various parameters with increasing SNR and/or with changing diversity scheme. AWGN channel is used here for communication of sampled image data.

Wireless communication systems always demand higher data rates and better quality of service (QoS). Transmission reliability in a wireless channel with high path loss, time-varying multipath fading and power and bandwidth limitations, is a testing issue. Multiple-input multiple-output (MIMO) systems can reduce the effect of these channel interferences and achieve reliable signal transmission at high data rate. Space-time block code (STBC) is a coding scheme for the use of multiple transmits antennas providing a simple transmit diversity scheme. In certain MIMO fading environments, the offered channel capacity can be very low, where despite rich local scattering and uncorrelated transmit and receive signals, the system has a single degree of freedom. This effect has been termed as keyhole or pinhole effect. This contribution analyzes the average symbol error rate (SER) performance of MIMO systems employing orthogonal STBC with M-PSK constellations over fading channels in the presence...

The performance analysis of Alamouti space time block code (STBC) based orthogonal frequency division multiplexing (OFDM) is often analyzed on the assumption that the channel is constant over Alamouti code period (two consecutive OFDM symbol block). But when the channel is fast fading, this assumption does not hold good and causes co-channel interference (CCI). Hence, the simple Alamouti detection method is not sufficient to recover the original transmitted signal from the mixed transmitted signals at the receiver side. In this paper, we investigate several detection methods for cancelling the effect of CCI which includes SIC, ZF and DF. Finally, the performances of the above detection method are compared on the basis of symbol error rate (SER) for different mobile speed.

... The receiver is equipped with m (2.0 receive antennas. We generalize the MMSE-IC algorithm given for a two user scheme with flat fading channel in [6] for a multi-user scheme and use it for interference suppression and signal detection for the STBC MIMO-OFDM scheme. ...

— The hottest issue of next generation communication systems is data throughput improvement for any wireless channel conditions. MIMO systems are the key techniques for the next generation communication systems. BLAST systems achieve high data rates with acceptable BER performance over a good channels state while STBC systems can achieve better BER performance even for bad-state channels but with lower data rates than BLAST. Hybrid BLAST-STBC systems is the effective solution to achieve a good tradeoff between STBC and BLAST systems since it improves the BER performance and keep them robust over a special MIMO channel state compared with the conventional BLAST system. This paper will study and compare the hybrid BLASTSTBC systems BER performance and capacity at ML receiver with both BLAST and STBC systems. MATLAB software has been used as the main platform for system simulation.

Abstract: In this paper Enhancement detail for the two main applications of Long Term Evolution (LTE) these are fixed and Mobile LTE. Fixed LTE will send the data from a single point-to-multipoint like user's houses and companies. While full mobility achieved by Mobile LTE to cellular networks. This done at very high broadband data rate comparted with other broadband networks like WiMax and Wi-Fi. The two types of LTE above are used in planning of a proper network which offers better throughput wireless broadband connectivity with lower cost. This work present a new proposed structures for LTE based on Space Time Block Coding (STBC-LTE) and Discrete Wavelets Transform (DWT) as multicarrier. The purpose of these new proposed structures is to improve the performance of bit error rate (BER) compared with the conventional STBC-LTE that use fast Fourier transform (FFT) as multicarrier. In addition, the new proposed structures with more than three transmits antennas and DWT was used ...

This work explores the performances of Space-Time and Space Frequency Coded Orthogonal Frequency Division Multiplexing (OFDM) with simple two branches transmit diversity scheme. The combination of multiple-antenna and orthogonal frequency division multiplexing (OFDM) provides reliable communications over frequency selective fading channels. We focus on the application of space-time block codes (STBC) and space-frequency block codes (SFBC) in OFDM systems over time-varying and frequency-selective channels. SFBC transmitter shows superior performance in fast varying channels while STBC shows better performance in frequency selective channels. A switching technique is presented that selects an appropriate transmission scheme between the STBC and SFBC assuming Rayleigh fading model.

Sensor networks require robust and efficient communication protocols to maximise the network lifetime. Radio irregularity, channel fading and interference results in larger energy consumption and latency for packet transmission over wireless channel. Cooperative multi-input multi-output (MIMO) schemes when incorporated in wireless senor network (WSN) can significantly improve the communication performance. An inefficiently designed medium access control (MAC) protocol however, may diminish the performance gains of MIMO operation. Hence, this paper proposes a distributed threshold based MAC protocol for cooperative MIMO transmissions using space time block codes (STBC). The protocol uses a thresholding scheme that is updated dynamically based on the queue length at the sending node to achieve lesser energy consumption and minimise latency ensuring the stability of transmission queues at the nodes. STBC and code combining techniques are applied to utilise the inherent spatial diversity in wireless cooperative MIMO systems. Simulation results are provided to evaluate the performance of the proposed protocol and are compared with fixed group size cooperative MIMO MAC protocols with and without STBC coding. Results show that the proposed protocol outperforms point to point communication as well as cooperative MIMO MAC protocols that use fixed group sizes. STBC technique for the proposed MAC protocol provides significant energy savings and minimises the packet delay by leveraging MIMO diversity gains.

ABSTRACT In this paper, we propose to reduce the complexity of both the Approx-Log-MAP algorithm as well as of the Max-Log-MAP algorithm conceived for generalized PSK/QAM detection, where only a reduced-size subset of the PSK/QAM constellation points is taken into account for producing a single soft-bit output. Although the detectors of Gray-labelled low-order PSK/QAM schemes generally produce near-horizontal EXIT curves, our proposed detectors exploit the a priori LLRs gleaned from a channel decoder in order to retain the optimum detection capability for all PSK/QAM constellations. Furthermore, we demonstrate in this paper that the widely applied MIMO schemes including V-BLAST and STBC, which invoke the proposed soft PSK/QAM detectors may also benefit from our reduced-complexity design. Our simulation results confirm that a near-capacity performance may be achieved by the proposed detectors at a substantially reduced detection complexity.

MIMO-STBC-OFDM systems mitigate inter symbol interference and frequency-selective fading caused by multi-path propagation in modern high-data-rate wireless communication. Error correction codes use redundancy to correct errors that still occur. No systematic analysis of their performance using a common link configuration is found in the literature. We fill this gap in this simulation study using a common MIMO-STBC-OFDM communication link, transferring data at a symbol rate of 100 Mbps. We find that (a) for all code rates, low-density parity-check code performs best with BPSK and to an extent with QPSK and (b) 1/2-rate convolutional code works well for all symbol mapping schemes.