Ambient Backscatter Communication Systems With MFSK Modulation

Ambient Backscatter Communications Systems with MFSK Modulation

Abstract: The ambient backscatter communication is a newly rising paradigm for Internet of Things networks, which enables the connection of low-cost devices. This paper proposes a novel MFSK modulation for the Tag of ambient backscatter communications systems, and the corresponding detectors are designed depending on the capability of the Reader. In the case the Reader is not capable of removing the direct interference from the ambient source, a maximum likelihood detector is proposed. In another case, leveraging on the frequency shift feature of the MFSK modulation, the Reader can remove the direct interference. Then a simple energy detector is proposed, and the closed-form expressions for the symbol error rate and outage probability of the system are derived. The findings of the paper suggest that the proposed MFSK modulation outperforms the popular on-off keying modulation, and the impact of modulation order on the SER performance depends heavily on the operating bit signal to noise ratio. Moreover, it is shown that, it is desirable to place the Tag close to the Reader in terms of minimizing the outage probability.

Existing system:

Responding to this, novel ideas were proposed to remove the interference in the literature. In particular, for OFDM ambient signals, the cyclic prefix feature was exploited to remove the direct-link interference. Another effective approach to handle the direct-link interference is to adopt frequency shift keying (FSK) modulation. 1 In, proof of- concept demonstration of using frequency shift keying schemes was conducted, yet the analytical performance remains largely unknown.

Later in, the pseudo-FSK and frequency-shifted BPSK modulation schemes were proposed and different types of detectors were derived depending on the available knowledge of the structure of the ambient RF signals.

Proposed system: Most of the works on ambient backscatter systems adopt the on-off keying (OOK) modulation to simplify the design and implementation of the low-cost and lowcomplexity Tag, where the Tag transmits the information bits by switching between two possible operation modes depending on whether to reflect the incident ambient RF signals. To enable reliable information detection, various detectors have been proposed. In, a semi-coherent detector was devised. To circumvent the channel state information (CSI) requirement of the semi-coherent detector, the works proposed novel non-coherent detectors by utilizing the idea of differential modulation. In, the authors proposed the Manchester coding scheme, which resolved the practical issue of non uniform input distribution. To improve the communication range and rate, the works proposed the three states coding and multi-antenna schemes, respectively.

Advantages: Due to this desirable feature, ambient backscatter communications systems have recently drawn considerable interests from both the academia and industry.

Most of the works on ambient backscatter systems adopt the on-off keying (OOK) modulation to simplify the design and implementation of the low-cost and lowcomplexity Tag, where the Tag transmits the information bits by switching between two possible operation modes depending on whether to reflect the incident ambient RF signals.

Disadvantages:

This paper has studied the problem of reliable symbol detection for ambient backscatter communications systems with MFSK modulation. In particular, depending on the assumption of Reader, different detectors, i.e., ML and energy detector have been proposed.

In addition, the SER and outage probability of the energy detectors are derived, and the optimal designs of the several key parameters are discussed.

Modules: Maximum likelihood: A general MFSK modulation scheme is proposed for the Tag. Depending on whether the Reader is capable of removing the direct interference from the ambient RF signals, two different types of detectors are proposed. In particular, for the case where the Reader cannot remove the direct interference, an optimal maximum likelihood (ML) detector is proposed. For the case where the Reader can remove the direct interference, a simple energy detector is proposed. A closed-form expression involving only elementary functions is derived for the symbol error rate (SER) of MFSK energy detector, which not only enables efficient evaluation of the SER performance, but also facilitates the design and optimization of several key system parameters. In addition, the outage probability of MFSK energy detector is derived.

Internet of things: With the explosive growth of Internet of Things (IoT) networks, cost-effective maintenance of the enormous number of low-cost devices such as recharging/replacing the batteries has emerged as one of the key challenges for building future green and sustainable IoT networks. To tackle this issue, one of the promising approaches is to adopt ambient backscatter communications, which enables the ambient backscatter devices, usually referred to as Tag, to modulate the information over the ambient radio frequency (RF) signals without requiring active transmitting RF components. As such, the Tag can be made battery free, which will greatly facilitate the deployment of IoT networks. Due to this desirable feature, ambient backscatter communications systems have recently drawn considerable interests from both the academia and industry.

Channel state information: Most of the works on ambient backscatter systems adopt the on-off keying (OOK) modulation to simplify the design and implementation of the low-cost and lowcomplexity Tag, where the Tag transmits the information bits by switching between two possible operation modes depending on whether to reflect the incident ambient RF signals. To enable reliable information detection, various detectors have been proposed. In, a semi-coherent detector was devised. To circumvent the channel state information (CSI) requirement of the semi-coherent detector, the works proposed novel non-coherent detectors by utilizing the idea of differential modulation. In, the authors proposed the Manchester coding scheme, which resolved the practical issue of non uniform input distribution. To improve the communication range and rate, the works proposed the three states coding and multi-antenna schemes, respectively.

Frequency shift keying: Responding to this, novel ideas were proposed to remove the interference in the literature. In particular, for OFDM ambient signals, the cyclic prefix feature was exploited to remove the direct-link interference. Another effective approach to handle the direct-link interference is to adopt frequency shift keying (FSK) modulation. In, proof of- concept demonstration of using frequency shift keying schemes was conducted, yet the analytical performance remains largely unknown.

Later in, the pseudo-FSK and frequency-shifted BPSK modulation schemes were proposed and different types of detectors were derived depending on the available knowledge of the structure of the ambient RF signals.