Turbo-FSK: A new uplink scheme for low power wide area networks

Abstract

International audienceThe Internet of Things aims to connect several billions of devices. Terminals are expected to be low cost, low power, and able to achieve successful communication at long range. While current Machine-to-Machine technologies tend to use spreading factors to meet the required specifications, we propose a more sophisticated use of redundant waveforms in a scheme called Turbo-FSK. This scheme involves Frequency-Shift-Keying (FSK) modulation at the transmission, and a turbo-decoder dedicated to the FSK waveforms at the receiver. Highly robust communication is achieved with a mere transmitter, as complexity is deported on the receiver side. Results are compared to common modulations using spreading factors, a significant gain in performance is achieved even with small packet sizes

A Comparison of Physical Layers for Low Power Wide Area Networks

“…A recent scheme has been proposed, using orthogonal modulations and turbo decoding at the receiver side [9]. This scheme allows for a better use of redundancy than in pure repetition scheme, and achieves an interesting energy efficiency gain.…”

“…Orthogonality of the transmitted codewords is one of the key feature of this scheme, which offers a great performance gain compared to simple repetition schemes. Detailed explanations about the transmitter and the receiver's computations can be found in [9].…”

“…We consider the widely known Turbo Code (TC) standardized by the Universal Mobile Telecommunications System (UMTS) [7,8] combined with a common modulation and a SF as a potential physical layer for LPWA. Our recent work [9] pointed out that if the repetition scheme allows a decrease of the required Signal-to-Noise Ratio (SNR) of a specific modulation, it does not increase the energy efficiency of the system (which can be expressed in terms of energy per bit to noise spectral density ratio, denoted E b /N 0 ). This is a consequence of the information rate reduction implied by the use of the SF.…”

“…Redundancy should be used more efficiently by the receiver, by means of turbo processing. The scheme proposed in [9], dedicated to LPWA networks, combines orthogonal modulation with turbo processing, and achieves very promising level of performance.…”

“…In this paper, we propose a comparison of four different schemes: the 802.15.4k standard [5], OSSS with a Hamming code, the TC UMTS from [7,8] with a common modulation (Binary Phase Shift Keying (BPSK) or M -ary orthogonal modulation), and the Turbo-FSK scheme proposed in [9]. All of them perform at a low spectral efficiency, aim a high energy efficiency, and would be suitable for uplink communication in the context of LPWA networks.…”