Interference Alignment (IA) and Coordinated Multi-Point (CoMP) with IEEE802.11ac feedback compression: testbed results

We have implemented interference alignment (IA) and joint transmission coordinated multipoint (CoMP) on a wireless testbed using the feedback compression scheme of the new 802.11ac standard. The performance as a function of the frequency domain granularity is assessed. Realistic throughput gains are obtained by probing each spatial modulation stream with ten different coding and modulation schemes. The gain of IA and CoMP over TDMA MIMO is found to be 26% and 71%, respectively under stationary conditions. In our dense indoor office deployment, the frequency domain granularity of the feedback can be reduced down to every 8th subcarrier (2.5MHz), without sacrificing performance.Comment: To appear in ICASSP 201

Low-resolution ADC receiver design, MIMO interference cancellation prototyping, and PHY secrecy analysis.

This dissertation studies three independent research topics in the general field of wireless communications. The first topic focuses on new receiver design with low-resolution analog-to-digital converters (ADC). In future massive multiple-input-multiple-output (MIMO) systems, multiple high-speed high-resolution ADCs will become a bottleneck for practical applications because of the hardware complexity and power consumption. One solution to this problem is to adopt low-cost low-precision ADCs instead. In Chapter II, MU-MIMO-OFDM systems only equipped with low-precision ADCs are considered. A new turbo receiver structure is proposed to improve the overall system performance. Meanwhile, ultra-low-cost communication devices can enable massive deployment of disposable wireless relays. In Chapter III, the feasibility of using a one-bit relay cluster to help a power-constrained transmitter for distant communication is investigated. Nonlinear estimators are applied to enable effective decoding. The second topic focuses prototyping and verification of a LTE and WiFi co-existence system, where the operation of LTE in unlicensed spectrum (LTE-U) is discussed. LTE-U extends the benefits of LTE and LTE Advanced to unlicensed spectrum, enabling mobile operators to offload data traffic onto unlicensed frequencies more efficiently and effectively. With LTE-U, operators can offer consumers a more robust and seamless mobile broadband experience with better coverage and higher download speeds. As the coexistence leads to considerable performance instability of both LTE and WiFi transmissions, the LTE and WiFi receivers with MIMO interference canceller are designed and prototyped to support the coexistence in Chapter IV. The third topic focuses on theoretical analysis of physical-layer secrecy with finite blocklength. Unlike upper layer security approaches, the physical-layer communication security can guarantee information-theoretic secrecy. Current studies on the physical-layer secrecy are all based on infinite blocklength. Nevertheless, these asymptotic studies are unrealistic and the finite blocklength effect is crucial for practical secrecy communication. In Chapter V, a practical analysis of secure lattice codes is provided

Preamble design using embedded signalling for OFDM broadcast systems based on reduced-complexity distance detection

The second generation digital terrestrial television broadcasting standard (DVB-T2) adopts the so-called P1 symbol as the preamble for initial synchronization. The P1 symbol also carries a number of basic transmission parameters, including the fast Fourier transform size and the single-input/single-output as well as multiple-input/single-output mode, in order to appropriately configure the receiver for carrying out the subsequent processing. In this contribution, an improved preamble design is proposed, where a pair of training sequences is inserted in the frequency domain and their distance is used for transmission parameter signalling. At the receiver, only a low-complexity correlator is required for the detection of the signalling. Both the coarse carrier frequency offset and the signalling can be simultaneously estimated by detecting the above-mentioned correlation. Compared to the standardised P1 symbol, the proposed preamble design significantly reduces the complexity of the receiver while retaining high robustness in frequency-selective fading channels. Furthermore, we demonstrate that the proposed preamble design achieves a better signalling performance than the standardised P1 symbol, despite reducing the numbers of multiplications and additions by about 40% and 20%, respectively

Joint Sparse Channel Recovery with Quantized Feedback for Multi-User Massive MIMO Systems

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MIMO Systems

In recent years, it was realized that the MIMO communication systems seems to be inevitable in accelerated evolution of high data rates applications due to their potential to dramatically increase the spectral efficiency and simultaneously sending individual information to the corresponding users in wireless systems. This book, intends to provide highlights of the current research topics in the field of MIMO system, to offer a snapshot of the recent advances and major issues faced today by the researchers in the MIMO related areas. The book is written by specialists working in universities and research centers all over the world to cover the fundamental principles and main advanced topics on high data rates wireless communications systems over MIMO channels. Moreover, the book has the advantage of providing a collection of applications that are completely independent and self-contained; thus, the interested reader can choose any chapter and skip to another without losing continuity

Novel multiuser detection and multi-rate schemes for multi-carrier CDMA

A large variety of services is [sic] expected for wireless systems, in particular, high data rate services, such as wireless Internet access. Users with different data rates and quality of service (QoS) requirements must be accommodated. A suitable multiple access scheme is key to enabling wireless systems to support both the high data rate and the integrated multiple data rate transmissions with satisfactory performance and flexibility. A multi-carrier code division multiple access (MC-CDMA) scheme is a promising candidate for emerging broadband wireless systems. MC-CDMA is a hybrid of orthogonal frequency division multiplexing (OFDM) and code division multiple access (CDMA). The most salient feature of MC-CDMA is that the rate of transmission is not limited by the wireless channel\u27s frequency-selective fading effects caused by multipath propagation. In MC-CDMA, each chip of the desired user\u27s spreading code, multiplied by the current data bit, is modulated onto a separate subcarrier. Therefore, each subcarrier has a narrow bandwidth and undergoes frequency-flat fading. Two important issues for an MC-CDMA wireless system, multiuser detection and multi-rate access, are discussed in this dissertation. Several advanced receiver structures capable of suppressing multiuser interference in an uplink MC-CDMA system, operating in a frequency-selective fading channel, are studied in this dissertation. One receiver is based on a so-called multishot structure, in which the interference introduced by the asynchronous reception of different users is successfully suppressed by a receiver based on the minimum mean-square error (MMSE) criterion with a built-in de-biasing feature. Like many other multiuser schemes, this receiver is very sensitive to a delay estimation error. A blind adaptive two-stage decorrelating receiver based on the bootstrap algorithm is developed to combat severe performance degradation due to a delay estimation error. It is observed that in the presence of a delay estimation error the blind adaptive bootstrap receiver is more near-far resistant than the MMSE receiver. Furthermore, a differential bootstrap receiver is proposed to extend the limited operating range of the two-stage bootstrap receiver which suffers from a phase ambiguity problem. Another receiver is based on a partial sampling (PS) demodulation structure, which further reduces the sensitivity to unknown user delays in an uplink scenario. Using this partial sampling structure, it is no longer necessary to synchronize the receiver with the desired user. Following the partial sampling demodulator, a minimum mean-square error combining (MMSEC) detector is applied. The partial sampling MMSEC (PS-MMSEC) receiver is shown to have strong interference suppression and timing acquisition capabilities. The complexity of this receiver can be reduced significantly, with negligible performance loss, by choosing a suitable partial sampling rate and using a structure called reduced complexity PS-MMSEC (RPS-MMSEC). The adaptive implementation of these receivers yields a superior rate of convergence and symbol error rate performance in comparison to a conventional MMSEC receiver with known timing. All the above receiver structures are for a single-rate MC-CDMA. Three novel multi-rate access schemes for multi-rate MC-CDMA, fixed spreading length (FSL), coded FSL (CFSL) and variable spreading length (VSL), have been developed. These multi-rate access schemes enable users to transmit information at different data rates in one MC-CDMA system. Hence, voice, data, image and video can be transmitted seamlessly through a wireless infrastructure. The bit error rate performance of these schemes is investigated for both low-rate and high-rate users