Non-orthogonal multiple access (NOMA) is an essential enabling technology for the fifth generation (5G) wireless networks to meet the heterogeneous demands on low latency, high reliability, massive connectivity, improved fairness, and high throughput. The key idea behind NOMA is to serve multiple users in the same resource block, such as a time slot, subcarrier, or spreading code. The NOMA principle is a general framework, and several recently proposed 5G multiple access schemes can be viewed as special cases. This survey provides an overview of the latest NOMA research and innovations as well as their applications. Thereby, the papers published in this special issue are put into the content of the existing literature. Future research challenges regarding NOMA in 5G and beyond are also discussed.

A Survey on Non-Orthogonal Multiple Access for 5G Networks: Research Challenges and Future Trends

As a promising downlink multiple access scheme for further LTE enhancement and future radio access (FRA), this paper investigates the system-level performance of non-orthogonal multiple access (NOMA) with a successive interference canceller (SIC) on the receiver side. The goal is to clarify the potential gains of NOMA over orthogonal multiple access (OMA) such as OFDMA, taking into account key link adaptation functionalities of the LTE radio interface such as adaptive modulation and coding (AMC), hybrid automatic repeat request (HARQ), time/frequency-domain scheduling, and outer loop link adaptation (OLLA), in addition to NOMA specific functionalities such as dynamic multi-user power allocation. Based on computer simulations, we show under multiple configurations that the system-level performance achieved by NOMA is superior to that for OMA.

System-level performance evaluation of downlink non-orthogonal multiple access (NOMA)

In the fifth generation (5G) of wireless communication systems, hitherto unprecedented requirements are expected to be satisfied. As one of the promising techniques of addressing these challenges, non-orthogonal multiple access (NOMA) has been actively investigated in recent years. In contrast to the family of conventional orthogonal multiple access (OMA) schemes, the key distinguishing feature of NOMA is to support a higher number of users than the number of orthogonal resource slots with the aid of non-orthogonal resource allocation. This may be realized by the sophisticated inter-user interference cancellation at the cost of an increased receiver complexity. In this paper, we provide a comprehensive survey of the original birth, the most recent development, and the future research directions of NOMA. Specifically, the basic principle of NOMA will be introduced at first, with the comparison between NOMA and OMA especially from the perspective of information theory. Then, the prominent NOMA schemes are discussed by dividing them into two categories, namely, power-domain and code-domain NOMA. Their design principles and key features will be discussed in detail, and a systematic comparison of these NOMA schemes will be summarized in terms of their spectral efficiency, system performance, receiver complexity, etc. Finally, we will highlight a range of challenging open problems that should be solved for NOMA, along with corresponding opportunities and future research trends to address these challenges.

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A Survey of Non-Orthogonal Multiple Access for 5G

The present invention is designed to provide a user terminal, a radio base station and a radio communication method of novel structures that can achieve a good communication environment. A radio base station non-orthogonal-multiplexes downlink signals for a plurality of user terminals over a given radio resource, a user terminal having received the downlink signals for the plurality of user terminals decodes downlink signal for another user terminal, judges whether or not the downlink signal for the other user terminal has been successfully received, based on the decoding result of the downlink signal, reports a judgement result as to whether or not the downlink signal for the other user terminal has been successfully received and a judgement result as to whether or not a downlink signal for the user terminal has been successfully received, to the radio base station, and then the radio base station executes retransmission control of downlink signals based on reports from the user terminal.

User terminal, radio base station and radio communication method

This paper investigates the system-level performance of downlink non-orthogonal multiple access (NOMA) with power-domain user multiplexing at the transmitter side and successive interference canceller (SIC) on the receiver side. The goal is to clarify the performance gains of NOMA for future LTE (Long-Term Evolution) enhancements, taking into account design aspects related to the LTE radio interface such as, frequency-domain scheduling with adaptive modulation and coding (AMC), and NOMA specific functionalities such as error propagation of SIC receiver, multi-user pairing and transmit power allocation. In particular, a pre-defined user grouping and fixed per-group power allocation are proposed to reduce the overhead associated with power allocation signalling. Based on computer simulations, we show that for both wideband and subband scheduling and both low and high mobility scenarios, NOMA can still provide a hefty portion of its expected gains even with error propagation, and also when the proposed simplified user grouping and power allocation are used.

System-level performance of downlink NOMA for future LTE enhancements

We propose a pseudo-inverse minimum mean squared error (MMSE) based QR decomposition (QRD) M-algorithm (QRD-M) for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. The proposed algorithm can effectively mitigate the detrimental effect of MIMO channel ill-conditions on the bit error rate (BER) performance. As a result, the number of retained branches (M value) can be reduced to half of the original QRD-M algorithm in Kyeong Jin Kim and R.A. Iltis (2002) in order to achieve the same performance for both the uncoded and coded systems. The detection complexity is therefore greatly reduced

Pseudo-Inverse MMSE Based QRD-M Algorithm for MIMO OFDM

Non-orthogonal Access with Random Beamforming and Intra-beam SIC for Cellular MIMO Downlink

PROBLEM TO BE SOLVED: To provide a transmitter capable of transmitting at least part of control information by using a preamble part and to provide a receiver and a random access control method. SOLUTION: The transmitter is provided with: a random access channel generating means for generating a random access channel comprising the preamble part including at least part of the control information; and a transmission means that applies either of consecutive frequency allocation and discontinuous intermittent frequency allocation to each user and transmits the random access channel by a variable multi-bandwidth. COPYRIGHT: (C)2008,JPO&INPIT

Transmitter and receiver, and random access control method

PROBLEM TO BE SOLVED: To provide a radio communication device which can realize a beam pattern excellently suppressing interference waves even in a radio communication environment where the communication of up and down links is asymmetrical. SOLUTION: A radio communication device is provided with an array antenna deriving a pair of reception signals from a plurality of antenna elements, a means estimating an arriving direction of a path, a means calculating a pair of first weighting coefficients concerning a plurality of paths, a means calculating a pair of second weighting coefficients per path on the basis of the arriving direction of path estimated, a weighting means multiplying the first or the second weighting coefficient by the reception signal according to an angle expansion between paths, a means calculating a pair of weighting coefficients which determine a beam pattern of a transmission signal, and a means multiplying the weighting coefficient by a signal to be transmitted. According to the angle expansion between paths, a weighting coefficient realizing a different beam pattern is calculated. COPYRIGHT: (C)2005,JPO&NCIPI

Higuchi Kenichi

Papers

Pseudo-Inverse MMSE Based QRD-M Algorithm for MIMO OFDM

Non-orthogonal Access with Random Beamforming and Intra-beam SIC for Cellular MIMO Downlink

Transmitter and receiver, and random access control method

Radio communication device and method

A Study on Transmission Power Control Considering Inter-Cell Interference for Non-orthogonal Access with MMSE-SIC in Cellular Uplink