MIMO-OFDM Transceiver Research Articles

Joint Symbol Level Precoding and Combining for MIMO-OFDM Transceiver Architectures Based on One-Bit DACs and ADCs

Herein, a precoding scheme is developed for orthogonal frequency division multiplexing (OFDM) transmission in multiple-input multiple-output (MIMO) systems that use one-bit digital-to-analog converters (DACs) and analog-to-digital converters (ADCs) at the transmitter and receiver, respectively, as a means to reduce the power consumption. Two different one-bit architectures are presented. In the first, a single user MIMO system is considered where the DACs and ADCs of the transmitter and the receiver are assumed to be one-bit and in the second, a network of analog phase shifters is added at the receiver as an additional analog-only processing step with the view to mitigate some of the effects of coarse quantization. The precoding design problem is formulated and then split into two NP-hard optimization problems, which are solved by an algorithmic solution based on the Cyclic Coordinate Descent (CCD) framework. The design of the analog post-coding matrix for the second architecture is decoupled from the precoding design and is solved by an algorithm based on the alternating direction method of multipliers (ADMM). Numerical results show that the proposed precoding scheme successfully mitigates the effects of coarse quantization and the proposed systems achieve a performance close to that of systems equipped with full resolution DACs/ADCs.

Single-Carrier Modulation Versus OFDM for Millimeter-Wave Wireless MIMO

This paper presents results on the achievable spectral efficiency and on the energy efficiency for a wireless multiple-input-multiple-output (MIMO) link operating at millimeter wave frequencies (mmWave) in a typical 5G scenario. Two different single-carrier modem schemes are considered, i.e., a traditional modulation scheme with linear equalization at the receiver, and a single-carrier modulation with cyclic prefix, frequency-domain equalization and FFT-based processing at the receiver; these two schemes are compared with a conventional MIMO-OFDM transceiver structure. Our analysis jointly takes into account the peculiar characteristics of MIMO channels at mmWave frequencies, the use of hybrid (analog-digital) pre-coding and post-coding beamformers, the finite cardinality of the modulation structure, and the non-linear behavior of the transmitter power amplifiers. Our results show that the best performance is achieved by single-carrier modulation with time-domain equalization, which exhibits the smallest loss due to the non-linear distortion, and whose performance can be further improved by using advanced equalization schemes. Results also confirm that performance gets severely degraded when the link length exceeds 90-100 meters and the transmit power falls below 0 dBW.

Design of pipeline R2MDC FFT for implementation of MIMO OFDM transceivers using FPGA

In this paper, an area-efficient low power Fast Fourier Transform (FFT) processor is proposed for Multi Input Multi Output--Orthogonal Frequency Division Multiplexing (MIMO-OFDM) that consists of a modified architecture of radix-2 algorithm which is described as Radix-2 multipath delay commutation (R2MDC). Orthogonal frequency-division multiplexing is a popular method for high-data-rate wireless transmission. OFDM may be combined with multiple antennas at both the access point and mobile terminal to increase diversity gain and/or Enhance system capacity on a time-varying multi path fading channel, resulting in a multiple-input multiple-output OFDM system. This paper describes the design of R2MDC FFT for implementation of MIMO OFDM transceiver using FPGA targeted to future wireless LAN systems. The proposed system is pipeline Radix 2multipath delay commutation FFT has been designed for MIMO OFDM. The MIMO OFDM transceivers have been designed according to the proposed OFDM parameters. A low-power efficient and full-pipeline architecture enables the real-time operations of MIMO OFDM transceivers. The FPGA board has been developed to verify their circuit behavior and implementation of MIMO OFDM Transceivers.

Coarse Grained ADRES Based MIMO-OFDM Transceiver with New Radix- $${2}^{5}$$ 2 5 Pipeline FFT/IFFT Processor

Software defined radio (SDR) is an adaptive radio that sense and adjust the operating parameters based on the environment. MIMO-OFDM technique based SDR transceiver is an advanced technique over the conventional radio system in terms of complex adaptation strategies. To improve the performance of the OFDM architecture, a new algorithm was developed for FFT/IFFT unit called the radix-$${2}^{5}$$25 modified booth encoding algorithm. This paper describes the system-on-chip (SoC) implementation of MIMO-OFDM transceiver architecture for SDR. This architecture design is based on the concept of reusing the same software and hardware modules to handle different algorithms with the help of dynamic reconfigurable system. It provides a greater flexibility in the operation of reconfigurable system; also it can able to add new abilities into it, without adding additional hardware. The SoC functional verification of this transceiver circuit was carried out in the Xilinx Virtex 5 FPGA, on top of the ADRES reconfigurable SoC architecture. The result shows that the proposed method provides a greater performance by two times than the previous works. It had provided a high throughput (2.4 Gsample/s) with low latency (2.941 ns) and less area utilization (27k logic gates).

VLSI IMPLEMENTATION OF CHANNEL ESTIMATION FOR MIMO-OFDM TRANSCEIVER

In this study the VLSI architecture for MIMO-OFDM transceiver and the algorithm for the implementation of MMSE detection in MIMO-OFDM system is proposed. The implemented MIMO-OFDM system is capable of transmitting data at high throughput in physical layer and provides optimized hardware resources while achieving the same data rate. The proposed architecture has low latency, high throughput and efficient resource utilization. The result obtained is compared with the MATLAB results for verification. The main aim is to reduce the hardware complexity of the channel estimation.

A Low Power VLSI Implementation of 2X2 MIMO OFDM Transceiver with ICI-SC Scheme

A Low Power VLSI Implementation of 2X2 MIMO OFDM Transceiver with ICI-SC Scheme

VLSI Design of Pipelined R2MDC FFT for MIMO OFDM Transceivers

VLSI Design of Pipelined R2MDC FFT for MIMO OFDM Transceivers

Systematic MIMO OFDM transceiver implementation for MPSoCs: a nucleus based approach

In this paper, we analyze the potential as well as the limitations of multiprocessor system-on-chip (MPSoC) platforms when implementing software defined radio (SDR) applications for wireless communications. Suitable MPSoCs contain a potentially heterogeneous multi-core computing cluster and can be further equipped with application specific accelerators. The physical layer of a MIMO OFDM transceiver, for which the IEEE 802.11n standard serves as reference, is investigated in this work. To maintain portability, the platform independent algorithmic kernels (Nuclei) are identified first. In the following case study, efficient implementations (Flavors) of these Nuclei are implemented on an MPSoC platform. Resultant algorithmic performance (e.g., frame-error-rate) as well as the system performance (e.g., latency and throughput) are discussed.

On the Design of MIMO-OFDM Transceivers via Geometric Mean Decomposition

The Geometric Mean Decomposition (GMD) based transceiver design has gained huge attention in the recent past as it provides an optimal solution in terms of BER and capacity. GMD technique has been widely adopted for the joint transceiver design as it converts the MIMO channel into identical and parallel SISO channels hence avoiding the necessity for bit loading and also achieves minimized bit error rates (BER). In this paper, we have explored the possibility of utilizing these positives of GMD for MIMO-OFDM transceiver designs, which is unavailable in the current literature. This paper considers the design of a linear Precoder and a DFE under perfect CSIT and CSIR. Using GMD, both MMSE and ZF based transceiver designs are proposed for MIMO-OFDM system. The performance of the proposed systems has been compared with other types of transceiver designs based on SVD and QR decomposition. The robustness of these proposed systems against the channel imperfections have also been analyzed.

Component-based waveform development: the Nucleus tool flow for efficient and portable software defined radio

With the advent of multi-processor systems on chip (MPSoCs) and due to the complexity and variety of modern wireless standards, academia and industry are moving towards software defined radio (SDR) solutions. It is the goal of the SDR approach to allow designers to describe a radio standard or waveform by means of a high level language. This allows faster waveform development cycles and makes it easier to migrate waveforms across different platforms. Out of many software paradigms, component-based software engineering (CBSE) is an attractive match for SDR, especially for baseband applications. It abstracts waveforms in the traditional way algorithm designers think of their applications and guarantees a high degree of portability. However, existing CBSE approaches for SDR have not been able to close the gap between specification and implementation so as to achieve the computational performance and the energy efficiency of handcrafted solutions. The main reason for this gap is that these flows rely on traditional compilers to lower the high level specification to the platform. The work presented in this paper builds on the Nucleus Concept (Ramakrishnan et al., IEEE Military Communications Conference (MILCOM 2009) [28]) in which computationally intensive kernels and their implementation characteristics on the target platform are known. This information allows a tool to close the performance gap, and thus enables efficient component-based SDR development. In this paper we present such a flow and its supporting environment, which includes state-of-the-art tools for system level design. The flow is demonstrated on a MIMO OFDM transceiver.

Development and Outdoor Evaluation of an Experimental Platform in an 80-MHz Bandwidth 2×2 MIMO-OFDM System in 5.2-GHz Band

The IEEE802.11ac task group has announced the use of a wider channel that extends the channel bandwidth to more than 80MHz. We present an experimental platform consisting of a baseband and a RF unit in a 2×2 MIMO-OFDM system for the wider channel and report its system performance results from a field experiment. The MIMO-OFDM transceiver in the baseband unit has been designed to detect real-time MIMO and provides a maximum data rate of 600Mbps. OFDM tends to cause high peak PAPR for wider channels and distorts the power amplifier performance in the RF unit. We have improved the non-linear distortion by optimizing the OFDM preamble and evaluated its performance by conducting a simulation integrated with baseband processing and a RF. In the field experiment, our platform tested the communication performance in a farm and a passage environment.

Application layer ARQ for protecting video packets over an indoor MIMO-OFDM link with correlated block fading

The quality of experience (QoE) of IP-packetized streaming video is affected by both packet loss and packet delay variations. When the network delivering the video content contains a wireless link, occasional deep fades give rise to bursts of packet losses. In order to maintain a sufficient video QoE at the end user, video packets must be protected against losses by means of a suitable form of error control. In this contribution, we consider an indoor radio MIMO-OFDM transceiver operating over a Rayleigh block-fading channel with arbitrary correlation in the time and frequency dimensions, which makes use of an application layer Automatic Repeat reQuest (ARQ) protocol to provide additional protection of the video content against packet loss. We analyze the resulting residual packet loss performance, under a latency constraint imposed by the requirement of a small TV channel switching delay. This analysis makes direct use of the fading characterization (correlation functions in time and frequency dimensions) of the indoor environment, rather than relying on a Markov model that only approximately describes the packet loss process. Numerical results are obtained by Monte Carlo integration combined with an efficient importance sampling technique devised for the problem at hand. Assuming a 2.4 GHz wireless link, we point out how to select the system parameters (number of antennas, number of retransmissions) in order to achieve a residual packet loss performance yielding a satisfactory QoE for HDTV transmission.

Symbol-wise beamforming for MIMO-OFDM transceivers in the presence of co-channel interference and spatial correlation

In MIMO-OFDM communications over channels subject to co-channel interference, beamforming (BF) is conventionally applied independently to all subcarriers. Whilst this approach maximises mutual information, it is highly computationally complex. Symbol-wise BF considerably reduces the complexity by carrying out BF in the time domain. In this paper, we generalise symbol-wise BF to take co-channel interference into account. Maximising the mutual information is infeasible in this case and instead, we propose a novel iterative algorithm that maximises the SINR before OFDM demodulation. Computer simulations show that the performance loss relative to subcarrier-wise BF reduces with decreasing frequency selectivity or increasing spatial correlation.

A Real-Time 4-Stream MIMO-OFDM Transceiver: System Design, FPGA Implementation, and Characterization

When designing complex communication systems, such as MIMO-OFDM transceivers, prototypes have become an important tool for understanding the implementation trade-offs and the system behavior. This paper presents a real-time FPGA prototype for a 4-stream MIMO-OFDM transceiver capable of transmitting 216 Mbit/s in 20 MHz bandwidth. The paper covers all parts of the system from RF to channel decoding and considers both algorithm and implementation aspects. In particular, we discuss the initial parameter estimation, channel estimation, MIMO detection, parameter tracking, and channel decoding. FPGA implementation results are reported along with measurements that demonstrate the throughput of spatial multiplexing with four spatial streams.

A road to future broadband wireless access: MIMO-OFDM-Based air interface

Orthogonal frequency-division multiplexing is a popular method for high-data-rate wireless transmission. OFDM may be combined with multiple antennas at both the access point and mobile terminal to increase diversity gain and/or enhance system capacity on a time-varying multipath fading channel, resulting in a multiple-input multiple-output OFDM system. In this article we give a brief technical overview of MIMO-OFDM system design. We focus on various research topics for the MIMO-OFDM-based air interface, including spatial channel modeling, MIMO-OFDM transceiver design, MIMO-OFDM channel estimation, space-time techniques for MIMO-OFDM, and error correction code. The corresponding link-level simulation results are encouraging, and show that MIMO-OFDM is a promising road to future broadband wireless access.