Frequency synchronization and phase offset tracking in a real-time 60-GHz CS-OFDM MIMO system

The performance of an Orthogonal Frequency-Division-Multiplexing (OFDM)-based 60-GHz system can be strongly degraded due to carrier frequency impairment and Phase Noise (PN). In this paper we present a practical approach to the design of a frequency synchronization and phase offset tracking scheme for a 60-GHz, Non-Line-of-Sight (NLOS) capable wireless communication system. We first analyse the architecture of the 60-GHz system and propose a simple algorithm for Carrier Frequency Offset (CFO) estimation on the basis of numerical investigations. Then, we explore pilot based and blind tracking methods for mitigation of Residual Frequency Offset (RFO) and Common Phase Error (CPE). Provided are also analysis and implementation results on an Altera Startix III FPGA

Joint calibration of frequency selective time variant I/Q-imbalance and modulator DC-offset error in broadband direct-conversion transmitters

Recently, much attention has been paid to frequency selective I/Q-imbalance, which can seriously limit the performance of broadband direct-conversion transceivers and degrade the baseband pre-linearization of the power amplifier in the transmitter. This paper addresses the issue of joint calibration of frequency selective I/Q-imbalance and modulator DC-offset error in the transmitter. The presented parameter estimation requires no pilot signal, making the calibration "semi-blind" and standard-independent. The proposed digital pre-equalization is very simple. Moreover, the I/Q-imbalance is modeled as slowly time-variant and a seamless I/Q-imbalance and DC-offset error parameter tracking algorithm is developed. The effectiveness of the proposed algorithms is verified by numerical simulations

Throughput maximization of a hybrid dynamic frame aggregation and block-ACK scheme for 60 GHz high speed communications

Recently, a strong demand on high data rate wireless communication can be observed. The development of multi-gigabit wireless transmission systems has become very attractive. For achieving such data rates, the exploitation of 60 GHz mm wave is a very promising technical approach and has been adopted in IEEE 802.15.3c. Except for physical layer (PHY) designs, the Medium Access Control (MAC) layer design is also crucial for the achievable system throughput (TP). Among the MAC functionalities, the acknowledgment (ACK) mechanism is a very important component affecting the transmission reliability and efficiency. Based on the ACK-mechanisms in 802.15.3c, this paper proposes a Hybrid Dynamic Frame Aggregation and Block-ACK (HD-FABA) scheme, which can further enhance the transmission efficiency and the system throughput. A theoretical model is developed to enable efficient parameter optimization and throughput maximization. In this way, the system can adaptively adjust its parameters according to the PHY conditions, so that the PHY data rate is exploited at best. The effectiveness of the proposed scheme was verified by numerical simulations

Semi-blind iterative joint estimation of frequency selective I/Q-imbalance and modulator offset error in direct-conversion transmitters

The compensation of frequency selective I/Q-imbalance and modulator (MOD) offset error can improve the performance of direct-conversion transmitters significantly. For effective compensation of these two effects, the parameter estimation is crucial. In many applications, ``semi-blind'' estimation is desired i.e. not dedicated pilot signals but the communication signals are used for estimation. Conventionally, Least-Square Estimation (LSE) is applied. However, if the communication signal has spectral gaps (e.g. due to oversampling), the LSE will suffer from ill-conditioned matrix problem, which results in severe estimation error. To overcome this problem, we propose an Iterative Frequency Domain Estimation (IFDE) technique, which operates adaptively according to the spectral characteristic of the communication signal and can provide good calibration performance. The effectiveness of the IFDE and its advantage over conventional LSE are verified by numerical simulations

Preamble Based Joint CFO, Frequency-Selective I/Q-Imbalance and Channel Estimation and Compensation in MIMO OFDM Systems

A very promising technical approach for future wireless communication systems is to combine MIMO OFDM and Direct (up/down) Conversion Architecture (DCA). However, while OFDM is sensitive to Carrier Frequency Offset (CFO), DCA is sensitive to I/Q-imbalance. Such RF impairments can seriously degrade the system performance. For the compensation of these impairments, a preamble-based scheme is proposed in this paper for the joint estimation of CFO, transmitter (Tx) and receiver (Rx) frequency-selective I/Q-imbalance and the MIMO channel. This preamble is constructed both in time- and frequency domain and requires much less overhead than the existing designs. Moreover, Closed-Form Estimators (CLFE) are allowed, enabling efficient implementation. The advantages and effectiveness of the proposed scheme have been verified by numerical simulations

Method for Determining Beamforming Parameters in a Wireless Communication System and to a Wireless Communication System

A method for determining a beamforming vector or a beamforming channel matrix in a communication system including a transmitting station and a receiving station, and a communication system are described. The transmitting and receiving stations include respective antenna groups and respective codebooks include a plurality of predefined beamforming vectors for the antenna group

Smart RF Signal Processing for Advanced Transmitters: From Theory to Practice

Multi-band multi-standard Base Stations (BS) are believed to be one promising solution to manage the coexistence of different technological standards (e.g. 2G/3G/4G) with reasonable installation and operation costs. Except for multi-technology baseband (BB) units and multi-band/broadband RF-frontends e.g. antenna and Power Amplifier (PA), the realization of such BSs requires sophisticated cooperation between digital BB and analog components to reduce frontend costs and to enhance energy efficiency, flexibility and transmission quality. Such a concept is called “Smart RF”. In this paper, we investigate the prototype implementation of practical digital signal processing techniques for performance enhancement of the RF-frontends and analog BB components in multi-band multi-standard transmitters. These techniques include the digital compensations of I/Q-imbalance, modulator (MOD) DC-offset and PA nonlinearity. A prototype platform is described where realtime impairment compensation circuits are implemented. Practical implementation issues incl. complexity and synchronization are discussed. Finally, experimental measurements are presented, which verify the effectiveness of the implemented Smart RF techniques

An NLOS-capable 60 GHz MIMO demonstrator: System concept & performance

In this paper we present a 60 GHz 2 × 2 MIMO demonstrator which has been developed to accomplish robust line-of-sight as well as non-line-of-sight indoor transmission. The physical layer concept is based on Code-Spread Orthogonal Frequency Division Multiplexing (CS-OFDM) and Alamouti Space-Time Coding (STC) to make maximum use of both frequency and space diversity. The highly modular, reconfigurable hardware implementation comprises commercial FPGA platforms and selfdeveloped extension modules up to fully integrated TX/RX 60 GHz frontends in III-V technology.We present results of transmission experiments conducted in a small office environment, which exemplary illustrate the capabilities and the performance of the presented approach

Maximum directivity beam-former at 60 GHz with optical feeder

We present an optically controlled 60 GHz array antenna which may be used as a smart antenna in an envisaged broadband mobile communication system. The desired field patterns of the antenna were synthesized using the maximum directivity beam-forming algorithm which enables an optimum radio link to a selected mobile terminal to be created while the signals of other terminals are suppressed by the nulls of the antenna's field distribution. The 60 GHz signals were generated by optically heterodyning the signals of two laser diodes. The field distribution of the antenna was formed by a silica based photonic beam-forming network. The experimentally obtained data confirmed the calculated field patterns

Photonisch gesteuerte Antennenarrays fuer zellulare Breitband-Funknetz Abschlussbericht

With 3,5'' diskAvailable from TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman