In this paper, we investigate rate splitting (RS) for an uplink non-orthogonal multiple access (NOMA) system with a pair of near and far users adopting cyclic prefixed single carrier transmissions. Frequency-domain equalization is applied to assist successive interference cancellation at the base-station. Two kinds of RS schemes, namely, fixed RS (FRS) and cognitive RS (CRS) schemes, are proposed to realize RS for uplink NOMA with the aim of improving user fairness and outage performance in delay-limited transmissions. Corresponding to the split data streams, transmit power is allocated in either a fixed or cognitive manner for the FRS and CRS schemes, respectively. Based on achievable rate region analysis, the benefits of applying RS to uplink NOMA for enhancing the user fairness and outage performance are revealed. A modified Jain’s index is proposed to measure the user fairness for the considered delay-limited transmissions. Closed-form expressions are derived for the outage probabilities of the paired users, respectively, whereas the preferred system parameters are chosen based on asymptotic outage probability expressions. The enhanced user fairness and superior outage performance of the proposed RS schemes are corroborated by Monte Carlo simulation results.

Rate Splitting for Uplink NOMA With Enhanced Fairness and Outage Performance

There is a growing demand for 5G applications in all fields of knowledge. Current applications, such as the Internet of Things, smart homes, and clean energy, require sophisticated forms of 5G waveforms. Researchers and developers are investigating the requirements of 5G networks for better waveform types, which will result in high spectrum efficiency and lower latency with less complexity in systems. This paper proposes an assessment of various 5G waveform candidates [filtered orthogonal frequency-division multiplexing (OFDM), universal filtered multicarrier (UFMC), filter bank multicarrier (FBMC), and generalized frequency-division multiplexing] under the key performance indicators (KPIs). This paper assesses the main KPI factors (computational complexity, peak-to-average-power ratio, spectral efficiency, filter length, and latency). Moreover, this paper compares and evaluates all KPI factors in various 5G waveforms. Finally, this paper highlights the strengths and weaknesses of each waveform candidate based on the KPI factors for better outcomes in the industry. In conclusion, the current review suggests the use of optimized waveforms (FBMC and UFMC) for better flexibility to overcome the drawbacks encountered by previous works. Regarding coexistence, FBMC and UFMC showed better coexistence with CP-OFDM in 4G networks with a new radio spectrum. The rapprochement between the above-mentioned waveforms has been called green coexistence and is due to the mix between one waveform in 4G networks and two waveforms in 5G networks based on the subcarrier and subband shaping (FBMC and UFMC).

Green Coexistence for 5G Waveform Candidates: A Review

This paper investigates the secrecy performance of a finite-sized in-band selective relaying system with $M$ transmitters connected via unreliable backhaul links, $N$ decode-and-forward relays, and $K$ collaborative eavesdroppers. To send the source message to the destination, a transmitter-relay pair that achieves the highest end-to-end signal-to-noise ratio is selected for transmissions, while the $K$ eavesdroppers combine all the received signals from the selected transmitter and relay using maximal ratio combining. The proposed model introduces backhaul reliability and eavesdropping probability parameters to investigate practical constraints on the transmitter-relay cooperation and eavesdropper collaboration, respectively. Closed-form expressions are derived for the secrecy outage probability, probability of non-zero achievable secrecy rate, and ergodic secrecy rate for non-identical frequency-selective fading channels with robust cyclic-prefixed single carrier transmissions. These results show that the asymptotic secrecy outage probability and probability of non-zero achievable secrecy rate are exclusively determined by the number of transmitters $M$ and their corresponding set of backhaul reliability levels. Under unreliable backhaul connections, it is found that the secrecy diversity gain is determined by $M$ , $N$ , and the number of multipath components in the frequency selective fading channels. Link-level simulations are conducted to verify the derived impacts of backhaul reliability and collaborative eavesdropping on the secrecy performance.

Secrecy Performance of Finite-Sized In-Band Selective Relaying Systems With Unreliable Backhaul and Cooperative Eavesdroppers

The harsh propagation environment at millimeter-wave (mmW) frequencies can be countered by using large antenna arrays, which can be steered electronically to create directional beams. Knowledge of the key channel characteristics in this environment, including the delay spread, the coherence time, and the coherence bandwidth, plays a significant role in optimal adaptation of the transmission waveform. In this paper, we focus on analyzing the delay spread of a directional mmW channel. A high delay spread causes inter-symbol interference (ISI), which can be mitigated by concatenating cyclic prefixes (CPs) to data symbols at the expense of lower spectral efficiency. Considering a single mmW link, whose transmitter (Tx) and receiver (Rx) are equipped with uniform planar arrays (UPAs), we study the impact of various beamforming attributes (e.g., antenna-array size, beamwidth, beam direction, and beam misalignment) on the average and root-mean-square delay spread. We use detailed simulations with accurate 3GPP channel models and conduct extensive experiments using a $4\times 8$ UPA at 28 GHz to verify our analysis. Based on this analysis, we study the optimal beamforming configuration at the Rx for a given Tx beamformer so as to maximize the spectral efficiency. Our proposed beam selection method finds the best Rx beam direction that results in a low delay spread and high signal-to-noise ratio (SNR). Our extensive simulation and experimental results verify that this method significantly improves the spectral efficiency, almost doubling the data rate in some cases.

Impact of Beamforming on Delay Spread in Wideband Millimeter-wave Systems

The fifth generation of mobile communications (5G) provides advanced features which were not witnessed ever before. Its data rates, end to end latency, and several other performance parameters are absolutely exemplary. Extremely high data rates and low latency are very much suitable for applications related to multimedia communication. In fact, multimedia streaming is a priority area for 5G. The main requirements of multimedia streaming are fulfilled by 5G technologies. In this article, we analyze 5G features for high-speed streaming. Real-time streaming was not a popular application over mobile platforms in the previous mobile generations. However, these streaming related issues will be resolved in 5G. We go through the modern day streaming requirements and their infrastructure. The high bandwidths required in the core network of the 5G will be provided by the fast networking facilities of optical networks. In the access part MIMO and large constellation for modulation will serve the high speed streaming requirements. In this article, we logically correlate the advanced 5G features with high-speed streaming requirements.

An Overview of High Speed Streaming in 5G

Ultra broadband mobile communication is a key requirement of fifth generation (5G) wireless cellular networks. To fulfill this requirement much larger bandwidth is needed which can be delivered in millimeter band from 30 to 300 GHz. Beam formed transmission over a massive MIMO (m-MIMO) structure is an essential element of a millimeter wave (mmwave) system to compensate the large air propagation loss. This however requires new air interface design to overcome hardware limitations tied to m-MIMO and mmwave, particularly for higher frequencies above 40 GHz. In this paper a block-wise single carrier (BWSC) waveform with low peak-to-average ratio (PAPR) is proposed to lower the cost of massive number of RF components needed to realize an m-MIMO structure for mmwave. Same as OFDM, data-based cyclic prefix (CP) is attached to every BWSC block to enable frequency domain equalization (FDE). Evaluations have been conducted to demonstrate the advantage of data-CP BWSC over orthogonal division multiplexing (OFDM) and null-CP single carrier waveform in terms of some key performance measures such as system efficiency, adjacent channel leakage ratio (ACLR), inter-symbol inference (ISI) and PAPR.

Single Carrier Waveform Solution for Millimeter Wave Air Interface

Described is an apparatus comprising an interface to receive channel output; and a decoder to decode the channel output. The decoder may comprise a plurality of decoding paths, wherein a first decoding path and a second decoding path may comprise a common decoding segment.

Eren Sasoglu

Papers

Single Carrier Waveform Solution for Millimeter Wave Air Interface

Multi-path decoding of a polar code using in parallel permuted graphs of the polar code