Non-orthogonal multiple access (NOMA) has been considered as a study-item in 3GPP for 5G new radio (NR). However, it was decided not to continue with it as a work-item, and to leave it for possible use in beyond 5G. In this paper, we first review the discussions that ended in such decision. Particularly, we present simulation comparisons between the Welch-bound equality spread multiple access (WSMA)-based NOMA and multiuser multiple-input-multiple-output (MU-MIMO), where the possible gain of WSMA-based NOMA, compared to MU-MIMO, is negligible. Then, we summarize the 3GPP discussions on NOMA, and propose a number of methods to reduce the implementation complexity and delay of both uplink (UL) and downlink (DL) NOMA-based transmission, as different ways to improve its efficiency. Here, particular attention is paid to reducing the receiver complexity, the cost of hybrid automatic repeat request as well as the user pairing complexity. As demonstrated, different smart techniques can be applied to improve the energy efficiency and the end-to-end transmission delay of NOMA-based systems.

No abstract

In this paper we study some statistical properties of a multicarrier signals using the order statistics. Analytical expressions for the probability density function of different order statistics of a sampled OFDM system is presented. We then find the amount of power which is clipped from each order of the signal when the signal is passed through a clipping nonlinearity. This is used to represent the relevance of peak-to-average power ratio (PAPR) to evaluate the effect of nonlinearity on the performance of a multicarrier system. The agreements between the theoretical results and the simulated ones demonstrate the validity of the analysis. We will also study different metrics for the signal envelope variations in terms of the sensitivity of each metric to amplitude nonlinearities. In the end the performance of an OFDM system with selected mapping based on different metrics is evaluated and compared with each other.Index Terms-Multicarrier signals, nonlinearity, peak to average power ratio (PAPR), cubic metric (CM).

No abstract

No abstract

No abstract

Among the key differentiators of 6G compared to 5G will be the increased emphasis on radio based positioning and sensing. These will be utilized not only for conventional locationaware services and for enhancing communication performance, but also to support new use case families with extreme performance requirements. This paper presents a unified vision from stakeholders across the value chain in terms of both opportunities and challenges for 6G positioning and sensing, as well as use cases, performance requirements, and gap analysis. Combined, this motivates the technical advances in 6G and guides system design.

One of the major drawbacks of multicarrier modulation is the large envelope fluctuations which either require an inefficient use of high power amplifiers or decrease the system performance. Peak-to-average power ratio (PAPR) is a very well known measure of the envelope fluctuations and has become the cost function used to evaluate and design multicarrier systems. Several PAPR-reducing techniques have been proposed with the aim to alleviate back-off specifications or increase the system performance. Besides the fact that these techniques have varying PAPR-reduction capabilities, power, bandwidth and complexity requirements, it is interesting to notice that the performance of a system employing these techniques has not been fully analyzed. In this paper we, first, develop a theoretical framework for both PAPR and the distortion introduced by a nonlinearity, and then simulate an OFDM system employing several well known PAPR-reducing techniques from the literature. By means of the theoretical analysis and the simulation results we will show the relation between PAPR and the performance of OFDM systems when a clipping device is present and we will evaluate the real performance improvement capabilities of the PAPR-reducing methods. The agreement between the theoretical and the simulation results demonstrate the validity of the analysis.