Multiple Antennas For Reception Research Articles

Theoretical Performance Evaluation of UHF-RFID Systems With Multi-Antenna Maximum-Likelihood Decoding

Radio frequency identification (RFID) is a technique that enables autonomous identification of objects using tiny and cheap transponders (tags). Therefore, its use increases, especially in the area of logistics. However, in dense applications scenarios with many tags multiple tags may transmit their data at the same time, leading to collisions. These collisions, especially in case of UHF RFID, significantly reduce the system throughput. The use of multiple input–multiple output (MIMO) is one candidate to achieve a high throughput even in case of tag collisions. Within this paper, we therefore analyze the performance of maximum-likelihood decoding for UHF RFID with multiple reception antennas. We especially take into account the impact of the FM0 channel encoding used by the EPCglobal Class-1 Gen-2 standard, the most common UHF RFID standard in the area of logistics. The channel characteristics of passive RFID systems follow the so-called double or backscatter Rayleigh distribution, which makes the performance analysis a challenging task. We use two methodologies to analyze the performance in this. First, we derive an upper bound symbol error probability (SEP) based on the pairwise error probability (PEP). The second technique depends on the exact evaluation of the SEP by taking into account all probabilities of errors between symbols. We finally compare the accuracy of both methodologies with simulation results. These results show that the PEP analysis converges with increasing number of antennas, and the exact analysis gives accurate results even with only two receive antennas.

Physical Layer Security of a Dual-Hop Regenerative Mixed RF/UOW System

Ensuring physical layer security is a crucial task in conventional and emerging communication systems, which are typically characterized by stringent quality of service and security requirements. This also accounts for wireless technologies in the context of the Internet of Things paradigm, which are expected to exhibit considerably increased computational complexity. Based on this, the present contribution investigates the secrecy outage performance of a dual-hop decode-and-forward (DF) mixed radio-frequency/ underwater optical wireless communication (RF/UOWC) system. Such wireless network configurations are particularly useful in efficient and demanding scenarios, such as military communications. Therefore, our analysis considers one single-antenna source node (S) communicating with one legitimate destination node (D) via a DF relay node (R) equipped with multiple antennas for reception. Particularly, the relay receives the incoming signal from S via an RF link, applies selection-combining (SC) technique, fully decodes it, re-encodes it, and then forwards it to the destination via a UOWC link. The communication is performed under the eavesdropper's attempt to intercept the S - R hop (RF side). In this context, a closed-form expression for the secrecy outage probability is derived along with a thorough asymptotic analysis in the high SNR regime, based on which the achievable diversity order is provided. The offered results provide useful insights on the impact of some key system and channel parameters on the secrecy outage performance, such as the number of eavesdroppers, the number of relay antennas, fading severity parameters of RF links, and water turbulence severity of the UOWC link. The conducted analysis shows that the secrecy outage probability is dominated only by the R-D link in the high SNR regime, regardless of the S-R parameters, such as the number of relay antennas and the average SNR at the relay branches. The offered analytic results are corroborated with respective results from computer simulations. Since these parameters are closely related with the computational complexity at the involved terminals, the offered insights are useful for the design and computationally sustainable operation of such systems.

Dual-Hop Mixed RF-UOW Communication System: A PHY Security Analysis

In this paper, the secrecy performance of a dual-hop mixed radio-frequency/underwater optical wireless communication (RF-UOWC) system is investigated. The considered system consists of one single antenna source node (S) communicating with one destination node (D), considered as the legitimate receiver, through an amplify-and-forward relay node equipped with multiple antennas for reception. Specifically, the relay receives the incoming signal from S via an RF link, applies maximal-ratio combining technique, amplifies the output combined signal with either a fixed gain or variable gain, and then forwards it to the destination via an UOWC link. The transmission protocol is performed under the eavesdropper's attempt to overhear the RF link (i.e., S-R). We derive exact closed-form expressions for the system's average secrecy capacity and the intercept probability in terms of Meijer's G-function as well as the univariate and bivariate Fox's H-functions. A complexity analysis is also performed to analyze the evaluation time of the derived analytical formulas as well as Monte Carlo simulation method complexity. Our derived analytical formulas present an efficient tool to depict the impact of some system and channel parameters on the secrecy performance, namely, the number of relay antennas, the number of eavesdropping nodes, relay gain, fading severity of RF links, and water turbulence severity of the UOWC link.

A CMOS front-end for RFID transponders using multiple coil antennas

A front-end architecture for inductive RFID transponders using multiple coil antennas for reduced orientation sensitivity is presented. The front-end uses multiple antennas for reception and one antenna for transmission. A select function identifies the antenna that is most favorably oriented toward the reader for transmission by comparing the DC charge-up phases of multiple DC generation blocks during power-up of the transponder. Design, simulations and measurement results of a front-end manufactured in 0.35 $$\upmu$$μm CMOS for 125 kHz FSK modulation are presented for a pulsed RFID system as well as an architecture for cascaded DC generation. This paper also includes a design example of a coil antenna for spherical transponders using three independent orthogonal windings.

Signal Reception for Space-Time Differentially Encoded Transmissions over FIR Rich Multipath Channels

With sophisticated signal and information processing algorithms, air interfaces with space-time (ST) coding and multiple reception antennas substantially improve the reliability of wireless links. This paper proposes a new receiver algorithm for differential ST coded transmissions over the finite-impulse-response (FIR) rich multipath fading channels. The symbol detection introduced in this paper is a deterministic subspace-based approach in a multiple-input and multiple-output (MIMO) system framework. The receiver (i) operates in a blind fashion without estimating the channel or its inverse and (ii) is able to work with a small number of signal samples and hence can be applied in the quasistatic channels. The proposed scheme employs multiple antennas at both sides of the transceiver and exploits both the antenna diversity and the multiple constant modulus (MCM) characteristics of the signaling. The receiver is able to blindly mitigate the intersymbol interference (ISI) in a rich multipath propagation environment, and this has been verified through the extensive Monte Carlo simulations.