Sequans

About: Sequans is a company organization based out in Reading, United Kingdom. It is known for research contribution in the topics: Communication channel & MIMO. The organization has 73 authors who have published 126 publications receiving 1066 citations.

Co-channel interference cancellation in reuse-1 deployments of WiMAX system

Abstract: In order to maximize the spectral efficiency, the current wireless systems tend to allocate the same frequency resources to different users, which causes the so-called Co-Channel Interference (CCI) on the signal received by the mobile user. If not handled appropriately, CCI may seriously degrade the communication performance. Therefore, for more reliable performance, robust transceiver techniques are required. In this paper, we consider WiMAX systems as example and propose a CCI cancellation method at the mobile user side based on a realistic cell-edge scenario. Particular attention is given to improve the performance during handover which is inevitable in reuse-1 networks. By using the conventional receiver structure with small additional processing, it is shown by simulations that the proposed method improves the performance significantly when a strong CCI is present.

Power-Domain NOMA or NOMA-2000?

Abstract: Non-Orthogonal Multiple Access (NOMA) has been a hot research topic in recent years, because it is widely advocated that this technique represents a promising technology for 5G cellular networks and beyond. The NOMA literature today is heavily based on the so-called Power-Domain NOMA (PD-NOMA), which requires a strong power imbalance between the signals assigned to different users. Also, the focus in the literature has been on the derivation of achievable rates, which represent an information theoretic measure. In contrast, the signal-to-noise ratio (SNR) degradation that is caused by multiuser interference at practical bit error rate (BER) values has not attracted much attention. In some recent papers, the present authors revived an early NOMA concept, which had been rather overlooked in the recent NOMA literature. This concept, which we refer to as NOMA-2000, consists of superposing the signals of two user groups with different signal waveforms rather than the signals of two users. In our earlier papers, performance of NOMA-2000 was investigated in various conditions, but no comparisons were provided with PD-NOMA. The purpose of this paper is to compare the BER performances of the two schemes using several values of the power splitting factor between users. The results confirm that PD-NOMA suffers a strong SNR degradation and that NOMA-2000 provides substantially better performance in general.

A BER Analysis of NOMA on Rician Fading Channels

Abstract: Non-Orthogonal Multiple Access (NOMA) has been a hot research topic over the past years. The general trend in the NOMA literature is the so-called Power-Domain NOMA (PD-NOMA), which requires a strong power imbalance at the receiver between the superposed signals. Also, the focus in the literature has been on the derivation of information theoretic results, and practical bit error rate (BER) has not attracted much attention. In recent papers, some of the present authors revived an early NOMA concept, which we refer to as NOMA-2000. Performance of NOMA-2000 was investigated on AWGN channels and Rayleigh fading channels, and it was found that in most cases this technique significantly outperforms PD-NOMA. The purpose of this paper is to compare the BER performances of the two schemes on Rician fading channels, which provide a more accurate representation of the radio channel in dense urban environments. The results confirm that on Rician channels too PD-NOMA suffers a strong SNR degradation with static resource allocation and that NOMA-2000 provides substantially better performance. But with dynamic resource allocation and user pairing, both techniques achieve good performance as long as the channel overloading factor does not exceed some limit.

New signal design for enhanced spatial modulation with multiple constellations

Abstract: In this paper, we introduce a new signal design for the Enhanced Spatial Modulation (ESM) concept, which was recently proposed by the present authors. The basic idea of ESM is to convey information bits not only by the indexes of the active transmit antennas, but also by the types of the multiple constellations used. Design of the original ESM schemes involved one or more secondary modulations, which were derived using a single step of geometric interpolation in the signal constellation plane. In the new design, we go one step further in the interpolation process and derive additional modulations leading to a significant increase of the number of active antenna and modulation combinations used. A design example is given for 10 bits per channel use (bpcu) transmission using four transmit antennas two of which are active at a time. The new design is compared to conventional multi-stream spatial modulation (MSM) and to our previously proposed ESM scheme. The analysis and the simulation results confirm a signal-to-noise ratio (SNR) gain of 2.2 dB over MSM and 0.4 dB over ESM when the three schemes are operated at the same spectral efficiency.

Cell search method for a downlink channel of an OFDMA transmission system

Abstract: A cell search method in a multiple carrier wireless network includes a step of trying to select, among a list of candidate couples [carrier frequency; bandwidth], at least one candidate associated with at least one cell of the multiple carrier wireless network. The cell search method includes: a step of obtaining and ordering an initial list of possible candidate couples [carrier frequency; bandwidth] according to the multiple carrier wireless network; a step of reducing the initial list, delivering a reduced list, the reduced list including only candidates compatible with a predetermined communication mode of the multiple carrier wireless network, through a differential cross correlation of the candidate couples [carrier frequency; bandwidth] of the initial list; a cell search step in which a cross-correlation is performed by testing all time/frequency hypothesis for at least one candidate of the reduced list of candidates, delivering synchronisation information.