Space-time-frequency channel estimation for multiple-antenna orthogonal frequency division multiplexing systems

We propose a linear mean square error channel estimator that exploits the joint space-time-frequency (STF) correlations of the wireless fading channel for applications in multiple-antenna orthogonal frequency division multiplexing systems. Our work generalizes existing channel estimators to the full dimensions including transmit spatial, receive spatial, time, and frequency. This allows versatile applications of our STF channel estimator to any fading environment, ranging from spatially-uncorrelated slow-varying frequency-flat channels to spatially-correlated fast-varying frequency-selective channels.The proposed STF channel estimator reduces to a time-frequency (TF) channel estimator when no spatial correlations exist. In another perspective, the lower-dimension TF channel estimator can be viewed as an STF channel estimator with spatial correlation mismatch for space-time-frequency selective channels.Computer simulations were performed to study the mean-square-error (MSE) behavior with different pilot parameters. We then evaluate the suitability of our STF channel estimator on a space-frequency block coded OFDM system. Bit error rate (BER) performance degradation, with respect to perfect coherent detection, is limited to less than 2 dB at a BER of 10-5 in the modified 3GPP fast-fading suburban macro environment. Modifications to the 3GPP channel involves reducing the base station angle spread to imitate a high transmit spatial correlation scenario to emphasize the benefit of exploiting spatial correlation in our STF channel estimator

Flexible MIMO architectures: guidelines in the design of MIMO parameters

One of the multiple advantages of communicating through MIMO systems is their inherent ability to provide flexible configurations. Following this line of thought, in this paper we present a generic framework to study the degrees of freedom in the design of MIMQ communication systems (e.g.: code length, number of multiplexed streams, or receiver structure). Precisely, we focus our efforts to bridge the gap between the design of MIMO systems with full and no channel state information at the transmitter side and also with different complexiry degrees at ihe receiver side. For instance, we can establish a trade-off, not only between the achievable rates and the diversity or beamforming gains, but also between the rate and the robustness to uncertainties in the channel state information.Postprint (published version

The Optimization of HiperLAN/2 Baseband Transceiver Based Wavelet Signals with Multiple Antennas

The present trends in the improvement of high-data-rate wireless systems focus on the integration of multiple input, multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM), this paper investigates a new approach to the adaptation of the HiperLAN/2 Baseband Transceiver based on Haar orthonormal wavelets signals and the physical layer performance of wireless communications systems, as well as multi-antenna techniques, such as multiple-input, multiple-output (MIMO) systems. The use Alamouti-based orthogonal space-time block coding technique. In MATLAB/ Simulink modeling simulation proved that the performance of HiperLAN/2 Baseband Transceiver Based wavelet Signals has a significant degradation in the packet (PDU or PSDU) error rate (PER) compared to conventional HiperLAN/2 Baseband Transceiver due to the considerable channel models. Keywords: HiperLAN/2, OFDM, DWT, IDWT, MIMO, PER, C/N

Distributed space-time block coding in wireless cooperative communications.

Cheng Ho Ting.Thesis (M.Phil.)--Chinese University of Hong Kong, 2005.Includes bibliographical references (leaves 90-93).Abstracts in English and Chinese.Abstract --- p.iAcknowledgement --- p.ivChapter 1 --- Introduction --- p.1Chapter 1.1 --- Overview of Wireless Cooperative Communications --- p.1Chapter 1.2 --- Motivation --- p.2Chapter 1.3 --- Distributed Space-Time Block Coding --- p.4Chapter 1.4 --- Imperfect Channel Estimation --- p.4Chapter 1.5 --- Time-Varying Channels --- p.4Chapter 1.6 --- Outline of the thesis --- p.5Chapter 2 --- Background Study --- p.6Chapter 3 --- Distributed Space-Time Block Coding --- p.13Chapter 3.1 --- Introduction --- p.13Chapter 3.2 --- System Model --- p.13Chapter 3.3 --- BER Analysis by Characteristic Equations --- p.16Chapter 3.4 --- BER Analysis by Error Terms --- p.18Chapter 3.4.1 --- Non-fading R→D link --- p.19Chapter 3.4.2 --- Fading R→D link --- p.19Chapter 3.5 --- Performance --- p.20Chapter 3.5.1 --- Accuracy of Analytical Expressions --- p.20Chapter 3.5.2 --- Observation of Second-order Diversity --- p.21Chapter 3.6 --- Summary --- p.22Chapter 4 --- Distributed Space-Time Block Coding with Imperfect Channel Estimation --- p.31Chapter 4.1 --- Introduction --- p.31Chapter 4.2 --- System Model --- p.32Chapter 4.3 --- BER Analysis --- p.32Chapter 4.3.1 --- Non-fading R→D link --- p.33Chapter 4.3.2 --- Fading R→D link --- p.34Chapter 4.4 --- Numerical Results --- p.34Chapter 4.5 --- Summary --- p.36Chapter 5 --- Distributed Space-Time Block Coding with Time-Varying Channels --- p.43Chapter 5.1 --- Introduction --- p.43Chapter 5.2 --- System Model --- p.44Chapter 5.3 --- Pilot Symbol Assisted Modulation (PSAM) for DSTBC --- p.45Chapter 5.4 --- Reception Methods --- p.48Chapter 5.4.1 --- Maximum-Likelihood Detection (ML) in [29] --- p.48Chapter 5.4.2 --- Cooperative Maximum-Likelihood Detection (CML) --- p.50Chapter 5.4.3 --- Alamouti's Receiver (AR) --- p.51Chapter 5.4.4 --- Zero-forcing Linear Detection (ZF) --- p.51Chapter 5.4.5 --- Decision-feedback Detection (DF) --- p.52Chapter 5.5 --- BER Analysis for Time-varying Channels --- p.53Chapter 5.5.1 --- Quasi-Static Channels (p = 1) --- p.53Chapter 5.5.2 --- ZF: Uncorrelated Channel (p = 0) --- p.54Chapter 5.5.3 --- ZF: General Channel --- p.55Chapter 5.5.4 --- DF: General Channel --- p.56Chapter 5.6 --- Numerical Results --- p.57Chapter 5.7 --- Summary --- p.60Chapter 6 --- Conclusion and Future Work --- p.74Chapter 6.1 --- Conclusion --- p.74Chapter 6.2 --- Future Work --- p.76Chapter 6.2.1 --- Design of Code Matrix --- p.76Chapter 6.2.2 --- Adaptive Protocols --- p.77Chapter A --- Derivation of (3.23) --- p.79Chapter B --- Derivation of (3.30) and (3.32) --- p.83Chapter C --- Derivation of (4.9) and (4.13) --- p.85Chapter D --- Derivation of (5.68) --- p.88Bibliography --- p.9

Distributed space time block coding in asynchronous cooperative relay networks

The design and analysis of various distributed space time block coding schemes for asynchronous cooperative relay networks is considered in this thesis. Rayleigh frequency flat fading channels are assumed to model the links in the networks, and interference suppression techniques together with an orthogonal frequency division multiplexing type transmission approach are employed to mitigate the synchronization errors at the destination node induced by the different delays through the relay nodes. Closed-loop space time block coding is first considered in the context of decode-and-forward (regenerative) networks. In particular, quasi orthogonal and extended orthogonal coding techniques are employed for transmission from four relay nodes and parallel interference cancellation detection is exploited to mitigate synchronization errors. Availability of a direct link between the source and destination nodes is studied, and a new Alamouti space time block coding technique with parallel interference cancellation detection which does not require such a direct link connection and employs two relay nodes is proposed. Outer coding is then added to gain further improvement in end-to-end performance and amplify-and-forward (non regenerative) type networks together with distributed space time coding are considered to reduce relay node complexity. Novel detection schemes are then proposed for decode-and-forward networks with closed-loop extended orthogonal coding which reduce the computational complexity of the parallel interference cancellation. Both sub-optimum and near-optimum detectors are presented for relay nodes with single or dual antennas. End-to-end bit error rate simulations confirm the potential of the approaches and their ability to mitigate synchronization errors. A relay selection approach is also formulated which maximizes spatial diversity gain and attains robustness to timing errors. Finally, a new closed-loop distributed extended orthogonal space time block coding solution for amplify-and-forward type networks which minimizes the number of feedback bits by using a cyclic rotation phase is presented. This approach utilizes an orthogonal frequency division multiplexing type transmission structure with a cyclic prefix to mitigate synchronization errors. End-to-end bit error performance evaluations verify the efficacy of the scheme and its success in overcoming synchronization errors

Novel transmission schemes for application in two-way cooperative relay wireless communication networks

Recently, cooperative relay networks have emerged as an attractive communications technique that can generate a new form of spatial diversity which is known as cooperative diversity, that can enhance system reliability without sacrificing the scarce bandwidth resource or consuming more transmit power. To achieve cooperative diversity single-antenna terminals in a wireless relay network typically share their antennas to form a virtual antenna array on the basis of their distributed locations. As such, the same diversity gains as in multi-input multi-output systems can be achieved without requiring multiple-antenna terminals. However, there remain technical challenges to maximize the benefit of cooperative communications, e.g. data rate, asynchronous transmission, interference and outage. Therefore, the focus of this thesis is to exploit cooperative relay networks within two-way transmission schemes. Such schemes have the potential to double the data rate as compared to one-way transmission schemes. Firstly, a new approach to two-way cooperative communications via extended distributed orthogonal space-time block coding (E-DOSTBC) based on phase rotation feedback is proposed with four relay nodes. This scheme can achieve full cooperative diversity and full transmission rate in addition to array gain. Then, distributed orthogonal space-time block coding (DOSTBC) is applied within an asynchronous two-way cooperative wireless relay network using two relay nodes. A parallel interference cancelation (PIC) detection scheme with low structural and computational complexity is applied at the terminal nodes in order to overcome the effect of imperfect synchronization among the cooperative relay nodes. Next, a DOSTBC scheme based on cooperative orthogonal frequency division multiplexing (OFDM) type transmission is proposed for flat fading channels which can overcome imperfect synchronization in the network. As such, this technique can effectively cope with the effects of fading and timing errors. Moreover, to increase the end-to-end data rate, a closed-loop EDOSTBC approach using through a three-time slot framework is proposed. A full interference cancelation scheme with OFDM and cyclic prefix type transmission is used in a two-hop cooperative four relay network with asynchronism in the both hops to achieve full data rate and completely cancel the timing error. The topic of outage probability analysis in the context of multi-relay selection for one-way cooperative amplify and forward networks is then considered. Local measurements of the instantaneous channel conditions are used to select the best single and best two relays from a number of available relays. Asymptotical conventional polices are provided to select the best single and two relays from a number of available relays. Finally, the outage probability of a two-way amplify and forward relay network with best and Mth relay selection is analyzed. The relay selection is performed either on the basis of a max-min strategy or one based on maximizing exact end-to-end signal-to-noise ratio. MATLAB and Maple software based simulations are employed throughout the thesis to support the analytical results and assess the performance of new algorithms and methods

Simulations of Implementation of Advanced Communication Technologies

Wireless communication systems have seen significant advancements with the introduction of 3G, 4G, and 5G mobile standards. Since the simulation of entire systems is complex and may not allow evaluation of the impact of individual techniques, this thesis presents techniques and results for simulating the performance of advanced signaling techniques used in 3G, 4G, and 5G systems, including Code division multiple access (CDMA), Multiple Input Multiple Output (MIMO) systems, and Low-Density Parity Check (LDPC) codes. One implementation issue that is explored is the use of quantized Analog to Digital Converter (ADC) outputs and their impact on system performance. Code division multiple access (CDMA) is a popular wireless technique, but its effectiveness is limited by factors such as multiple access interference (MAI) and the near far effect (NFE). The joint effect of sampling and quantization on the analog-digital converter (ADC) at the receiver\u27s front end has also been evaluated for different quantization bits. It has been demonstrated that 4 bits is the minimum ADC resolution sensitivity required for a reliable connection for a quantized signal with 3- and 6-dB power levels in noisy and interference-prone environments. The demand for high data rate, reliable transmission, low bit error rate, and maximum transmission with low power has increased in wireless systems. Multiple Input Multiple Output (MIMO) systems with multiple antennas at both the transmitter and receiver side can meet these requirements by exploiting diversity and multipath propagation. The focus of MIMO systems is on improving reliability and maximizing throughput. Performance analysis of single input single output (SISO), single input multiple output (SIMO), multiple input single output (MISO), and MIMO systems is conducted using Alamouti space time block code (STBC) and Maximum Ratio Combining (MRC) technique used for transmit and receive diversity for Rayleigh fading channel under AWGN environment for BPSK and QPSK modulation schemes. Spatial Multiplexing (SM) is used to enhance spectral efficiency without additional bandwidth and power requirements. Minimum mean square error (MMSE) method is used for signal detection at the receiver end due to its low complexity and better performance. The performance of MIMO SM technique is compared for different antenna configurations and modulation schemes, and the MMSE detector is employed at the receiving end. Advanced error correction techniques for channel coding are necessary to meet the demand for Mobile Internet in 5G wireless communications, particularly for the Internet of Things. Low Density Parity Check (LDPC) codes are used for error correction in 5G, offering high coding gain, high throughput, low latency, low power dissipation, low complexity, and rate compatibility. LDPC codes use base matrices of 5G New Radio (NR) for LDPC encoding, and a soft decision decoding algorithm is used for efficient Frame Error Rate (FER) performance. The performance of LDPC codes is assessed using a soft decision decoding layered message passing algorithm, with BPSK modulation and AWGN channel. Furthermore, the effects of quantization on LDPC codes are analyzed for both small and large numbers of quantization bits

Spectral Efficiency and Outage Performance Evaluation of Measured Vehicular Communication Radio Channels

[ES] Los sistemas cooperativos para entornos vehiculares tienen la capacidad de mejorar tanto la seguridad en carretera, como la gestión del tráfico. Tienen como base la norma del estándar de comunicaciones inalámbrico de red de área local (Wireless Local Area Network, WLAN) para el uso comunicaciones vehiculares (Vehicle-to-Vehicle/Infrastructure, V2I), denominada IEEE 802.11p, la cual se está desarrollando actualmente, y que dará lugar a la nueva tecnología de comunicaciones entre vehículos e infraestructura WAVE (Wireless Access in Vehicular Environments). Funcionando en el rango de frecuencias de 5.850 a 5.925 GHz, los sistemas WAVE adoptan la técnica de multiplexación OFDM (Orthogonal Frequency Division Multiplexing) y alcanzan tasas de transmisión de datos en el rango de 6 a 27 Mbps. El estudio del canal es clave para conocer el efecto de las condiciones de propagación reales sobre la transmisión. Habrá que tener en cuenta que en entornos de comunicaciones vehiculares se da la propagación con línea de visión directa (Line of Sight, LoS), por lo que a la hora de caracterizar el canal, habrá que considerar tanto el desvanecimiento Rayleigh como el desvanecimiento Ricean. Este estudio se hará a partir del procesado de la función de transferencia del canal obtenido para diferentes escenarios durante la campaña de medidas realizada en Lund, Suecia. en 2007 por la Universidad Técnica de Viena. El sistema radio utilizado considera múltiples antenas, es decir, el canal es Multiple-Input Multiple-Output (MIMO), dado que gracias a la diversidad consigue un mayor rendimiento. De cara a analizar el efecto de las condiciones de propagación sobre el rendimiento alcanzable, se caracterizará el canal mediante el Power Delay Profile (PDP) y el perfil de Path Loss. A continuación se estudiarán más en detalle los canales MIMO con desvanecimiento Ricean, cruciales para las comunicaciones Vehicle-to-Vehicle, (V2V). En estos canales hay una tasa de datos crítica (RCRIT) dependiente de una relación señal a ruido (Signal-to- Noise Ratio, SNR) bajo la cual la transmisión de datos con cero outage es posible, de manera que el canal se comporta como un canal con ruido aditivo gaussiano (Additive White Gaussian Noise, AWGN). Se analizará la tanto eficiencia espectral en términos de capacidad ergódica y como la probabilidad de outage del canal vehicular para diferentes valores de relación señal a ruido.[EN] Roadway-vehicle cooperative systems will lead to improve driving safety. These systems relay on a wireless local area network (WLAN) standard for automotive use, called IEEE 802.11p, which is under development in order to implement Wireless Access in Vehicular Environments (WAVE). Operating at 5.850¿5.925 GHz, WAVE systems adopt orthogonal frequency-division multiplexing (OFDM) and achieve data rates of 6¿27 Mbps. The development of efficient vehicle-to-vehicle (V2V) communications systems requires an understanding of the underlying radio propagation channels in order to analyze the real impact of real-world propagation conditions. Vehicular communication channels are non-stationary, because the conditions of the channel vary abruptly due to the speed of the vehicles. The studied wireless communication scenario is predominantly Line of Sight (LoS) propagation scenario, therefore Rayleigh fading and Ricean fading have to be considered for channel characterization. The reference data to be analyzed have been obtained from a channel sounding campaign carried out by the Vienna University of Technology in Lund, Sweden in 2007. The radio system used for this campaign is a multiple-input multiple-output (MIMO) system. Radio channel parameters such as the power delay profile and the path loss are going to be analyzed in order to study the impact of real-world propagation conditions. Reliability in Ricean MIMO channel is going to be more deeply characterized, as it is crucial for safety related V2V applications. In such channels, there is a SNR-dependent critical data rate (RCRIT) below which signaling with zero outage is possible, and hence the fading channel behaves like an AWGN channel. For the vehicular time variant channel spectral efficiency is going to be evaluated in terms of ergodic capacity and outage performance is also going to be studied by means of outage probability.Alonso Gómez, A. (2009). Spectral Efficiency and Outage Performance Evaluation of Measured Vehicular Communication Radio Channels. http://hdl.handle.net/10251/27442.Archivo delegad

Optimal cross layer design for CDMA-SFBC wireless systems

The demand for high speed reliable wireless services has been rapidly growing. Wireless networks have limited resources while wireless channels suffer from fading, interference and time variations. Furthermore, wireless applications have diverse end to end quality of service (QoS) requirements. The aforementioned challenges require the design of spectrally efficient transmission systems coupled with the collaboration of the different OSI layers i.e. cross layer design. To this end, we propose a code division multiple access (CDMA)-space frequency block coded (SFBC) systems for both uplink and downlink transmissions. The proposed systems exploit code, frequency and spatial diversities to improve reception. Furthermore, we derive closed form expressions for the average bit error rate of the proposed systems. In this thesis, we also propose a cross layer resource allocation algorithm for star CDMA-SFBC wireless networks. The proposed resource allocation algorithm assigns base transceiver stations (BTS), antenna arrays and frequency bands to users based on their locations such that their pair wise channel cross correlation is minimized while each user is assigned channels with maximum coherence time. The cooperation between the medium access control (MAC) and physical layers as applied by the optimized resource allocation algorithm improves the bit error rate of the users and the spectral efficiency of the network. A joint cross layer routing and resource allocation algorithm for multi radio CDMA-SFBC wireless mesh networks is also proposed in this thesis. The proposed cross layer algorithm assigns frequency bands to links to minimize the interference and channel estimation errors experienced by those links. Channel estimation errors are minimized by selecting channels with maximum coherence time. On top, the optimization algorithm routes network traffic such that the average end to end packet delay is minimized while avoiding links with high interference and short coherence time. The cooperation between physical, MAC and network layers as applied by the optimization algorithm provides noticeable improvements in average end to end packet delay and success rat