DFT-s-OFDM for sub-THz Transmission -- Tracking and Compensation of Phase Noise

For future wireless communication technologies, an increase in capabilities such as throughput is strongly expected. Transmission in the sub-THz bands (>90 GHz) seems to be the potential solution to meet the ever-increasing capacity demands due to the large unexploited bandwidth. Oscillators used at these frequencies generate phase noise that induces critical distortions in the signal that must be addressed. The correlated nature of PN makes it difficult to overcome. Nowadays, there is a growing interest in considering the extension of multicarrier based waveforms of the 5G new radio for transmissions in the sub-THz bands. In this paper, we introduce a new algorithm called the interpolation filter (IF), which efficiently estimates and compensates PN effects on DFT-s-OFDM systems. Specifically, it is based on the use of stochastic properties of the PN and is compatible with the 3GPP phase tracking reference signal scheme. We highlight a performance improvement over known techniques when using high-order modulation.Comment: Paper accepted and will be presented at the IEEE CCNC 2023 Conference that will be held in Las Vegas from January 8th to 11th, 202

Channel estimation strategy for LPWA transmission at low SNR: application to Turbo-FSK

International audienceTurbo Frequency Shift Keying has been considered as a promising physical layer for low power wide-area network connectivity. Because of its constant envelope amplitude and the efficiency of its iterative receiver performance close to Shannon's limit can be achieved. However, results published so far in the literature for the waveform have assumed perfect channel estimation or Signal-to-noise (SNR) levels that are higher than the SNR levels considered for these applications. This paper analyzes a channel estimation strategy based on a specifically adapted pilot sequence. Simulations have been performed to evaluate the performance of the proposed approach. Performance loss induced by imperfect channel estimation algorithms is estimated

Performance Evaluation Of Multiband CSMA/CA With RTS/CTS For M2M Communication With Finite Retransmission Strategy

International audienceM2M communication is information exchange between machines and machines without any human interaction. M2M commu-nication based on cellular network suffers from the extremely large number of devices in service coverage. In cellular network case, the large number of devices lead to communication problem caused by collisions between the senders. In this work we study the collision probability, saturation throughput and packet error rate for the carrier sense multiple access collision avoidance (CSMA/CA) protocol with request to send and clear to send (RTS/CTS) mechanism in the case of frequency band division. We propose in this paper a modified version of CSMA/CA-RTS/CTS to be compatible with the band repartition technique and we prove that an important gain is introduced in terms of system performance especially for loaded networks. Different backoff stage numbers with different finite retransmission limit values are investigated. Simulations highlight that dividing the RTS band into independent channels reduces drastically the RTS collision probability and in particular the packet error rate. A gain in terms of saturation throughput is also demonstrated especially in charged networks mode

Turbo-FSK : une nouvelle technique de communication montante pour les réseaux longue portée basse consommation

National audienceThe Internet of Things aims to connect several billions of devices. Terminals are expected to be low cost, low power, and to be 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-decoding 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, showing a significant gain in performance is achieved even with small packet sizes.L'internet des objets a pour vocation de connecter des milliards de terminaux entre eux. Ces derniers doivent être bon marché, économes en énergie, et capables de communiquer même à très longue portée. Alors que les technologies actuelles de communications machine-to-machine ont tendance à utiliser les techniques de répétition ou d'étalement afin de répondre aux contraintes notamment en termes de sensibilité, ce papier propose une utilisation plus sophistiquée de la répétition dans une technique dénommée Turbo-FSK. Cette dernière implique l'utilisation d'une modulation orthogonale de fréquence FSK et d'un turbo décodage spécifique aux formes d'onde FSK au niveau du récepteur. On montre alors qu'une communication robuste est possible même avec un émetteur très simple, la complexité étant déportée au niveau du récepteur. Les résultats de simulations sont comparés à des techniques de références, dont celles utilisant la répétition, démontrant qu'un gain significatif est obtenu même avec des petites tailles de paquets

Analysis of Frequency Channel Division Strategy for CSMA/CA with RTS/CTS Mechanism

International audience—In this work we study the collision probability, saturation throughput and statistical delay for the carrier sense multiple access collision avoidance (CSMA/CA) protocol with request to send and clear to send (RTS/CTS) mechanism in the case of frequency channel division. We propose in this paper a modified version of CSMA/CA-RTS/CTS to be compatible with the channel repartition technique and we prove that an important gain is introduced in terms of system performance especially for loaded networks. Simulations highlight that dividing the channel into independent sub-channels reduces drastically the RTS collision probability. Moreover, a gain in terms of saturation throughput and delay is shown especially in dense networks. Index Terms—Carrier senses multiple access/collision avoid-ance (CSMA/CA), Frequency channel division, RTS/CTS, MAC protocol

Conflict Resolution by Matrix Reordering for DVB-T2 LDPC Decoders

International audienceLayered decoding is known to provide efficient and high-throughput implementation of LDPC decoders. However, the implementation of the layered architecture is not always straightforward because of the memory access conflicts in the a-posteriori information memory. In this paper, we focus our attention on a particular type of conflict introduced by the existence of multiple diagonal matrices in the DVB-T2 parity check matrix structure. We illustrate how the reordering of the matrix reduces the number of conflicts, at the cost of limiting the level of parallelism. We then propose a parity extending process to solve the remaining conflicts. Fixed point simulation results show coherent performance without modifying the layered architecture

Conflict resolution for pipelined layered LDPC decoders

International audienceMany of the current LDPC implementations of DVB-S2, T2 or WiMAX standard use the so-called layered architecture combined with pipeline. However, the pipeline process may introduce memory access conflicts. The resolution of these conflicts requires careful scheduling combined with dedicated hardware and/or idle cycle insertion. In this paper, based on the DVB-T2 example, we explain explicitly how the scheduling can solve most of the pipeline conflicts. The two contributions of the paper are 1) how to split the matrix to relax the pipeline conflicts at a cost of a reduced maximum available parallelism 2) how to project the problem of the research of an efficient scheduling to the well-known "Travelling Salesman Problem" and use a genetic algorithm to solve it