A Survey: Non-Orthogonal Multiple Access with Compressed Sensing Multiuser Detection for mMTC <s>  <s> Novel low-density signature (LDS) structure is proposed for transmission and detection of symbol-synchronous communication over memoryless Gaussian channel. Given N as the processing gain, under this new arrangement, users' symbols are spread over N chips but virtually only dv < N chips that contain nonzero-values. The spread symbol is then so uniquely interleaved as the sampled, at chip rate, received signal contains the contribution from only dc < K number of users, where K denotes the total number of users in the system. Furthermore, a near-optimum chip-level iterative soft-in-soft-out (SISO) multiuser decoding (MUD), which is based on message passing algorithm (MPA) technique, is proposed to approximate optimum detection by efficiently exploiting the LDS structure. Given beta = K/N as the system loading, our simulation suggested that the proposed system alongside the proposed detection technique, in AWGN channel, can achieve an overall performance that is close to single-user performance, even when the system has 200% loading, i.e., when beta = 2. Its robustness against near-far effect and its performance behavior that is very similar to optimum detection are demonstrated in this paper. In addition, the complexity required for detection is now exponential to dc instead of K as in conventional code division multiple access (CDMA) structure employing optimum multiuser detector. <s> BIB001 </s> A Survey: Non-Orthogonal Multiple Access with Compressed Sensing Multiuser Detection for mMTC <s>  <s> Based on the bestseller "3G Evolution - HSPA and LTE for mobile broadband" and reflecting the ongoing success of LTE throughout the world, this book focuses on LTE with full updates including LTE-Advanced to provide a complete picture of the LTE system. Overview and detailed explanations are given for the latest LTE standards for radio interface architecture, the physical layer, access procedures, broadcast, relaying, spectrum and RF characteristics, and system performance. Key technologies presented include multi-carrier transmission, advanced single-carrier transmission, advanced receivers, OFDM, MIMO and adaptive antenna solutions, advanced radio resource management and protocols, and different radio network architectures. Their role and use in the context of mobile broadband access in general is explained. Both a high-level overview and more detailed step-by-step explanations of the LTE/LTE-Advanced implementation are given. An overview of other related systems such as GSM/EDGE, HSPA, CDMA2000, and WIMAX is also provided. This book is a 'must-have' resource for engineers and other professionals in the telecommunications industry, working with cellular or wireless broadband technologies, giving an understanding of how to utilize the new technology in order to stay ahead of the competition. The authors of the book all work at Ericsson Research and have been deeply involved in 3G and 4G development and standardisation since the early days of 3G research. They are leading experts in the field and are today still actively contributing to the standardisation of LTE within 3GPP. Includes full details of the latest additions to the LTE Radio Access standards and technologies up to and including 3GPP Release 10Clear explanations of the role of the underlying technologies for LTE, including OFDM and MIMO Full coverage of LTE-Advanced, including LTE carrier aggregation, extended multi-antenna transmission, relaying functionality and heterogeneous deploymentsLTE radio interface architecture, physical layer, access procedures, MBMS, RF characteristics and system performance covered in detail <s> BIB002 </s> A Survey: Non-Orthogonal Multiple Access with Compressed Sensing Multiuser Detection for mMTC <s>  <s> As a promising downlink multiple access scheme for future radio access (FRA), this paper discusses the concept and practical considerations of non-orthogonal multiple access (NOMA) with a successive interference canceller (SIC) at the receiver side. The goal is to clarify the benefits of NOMA over orthogonal multiple access (OMA) such as OFDMA adopted by Long-Term Evolution (LTE). Practical considerations of NOMA, such as multi-user power allocation, signalling overhead, SIC error propagation, performance in high mobility scenarios, and combination with multiple input multiple output (MIMO) are discussed. Using computer simulations, we provide system-level performance of NOMA taking into account practical aspects of the cellular system and some of the key parameters and functionalities of the LTE radio interface such as adaptive modulation and coding (AMC) and frequency-domain scheduling. We show under multiple configurations that the system-level performance achieved by NOMA is higher by more than 30% compared to OMA. <s> BIB003 </s> A Survey: Non-Orthogonal Multiple Access with Compressed Sensing Multiuser Detection for mMTC <s>  <s> In this letter, the performance of non-orthogonal multiple access (NOMA) is investigated in a cellular downlink scenario with randomly deployed users. The developed analytical results show that NOMA can achieve superior performance in terms of ergodic sum rates; however, the outage performance of NOMA depends critically on the choices of the users' targeted data rates and allocated power. In particular, a wrong choice of the targeted data rates and allocated power can lead to a situation in which the user's outage probability is always one, i.e. the user's targeted quality of service will never be met. <s> BIB004 </s> A Survey: Non-Orthogonal Multiple Access with Compressed Sensing Multiuser Detection for mMTC <s>  <s> 5G is envisioned to support unprecedented diverse applications and services with extremely heterogeneous performance requirements, i.e., mission critical IoT communication, massive machine-type communication and Gigabit mobile connectivity. This imposes enormous challenges to fulfil the key performance requirements, in particular, mission critical IoT communication, which calls for a dramatic paradigm change in 5G. This paper presents vision and challenges of mission critical IoT scenarios and the enabling technologies in 5G. Several research opportunities are given as example for inspiration purpose. <s> BIB005 </s> A Survey: Non-Orthogonal Multiple Access with Compressed Sensing Multiuser Detection for mMTC <s>  <s> Non-orthogonal multiple access (NOMA) has received considerable recent attention as a promising candidate for 5G systems. A key feature of NOMA is that users with better channel conditions have prior information about the messages of other users. This prior knowledge is fully exploited in this letter, where a cooperative NOMA scheme is proposed. The outage probability and diversity order achieved by this cooperative NOMA scheme are analyzed, and an approach based on user pairing is also proposed to reduce system complexity. <s> BIB006 </s> A Survey: Non-Orthogonal Multiple Access with Compressed Sensing Multiuser Detection for mMTC <s>  <s> In this paper, the application of simultaneous wireless information and power transfer (SWIPT) to nonorthogonal multiple access (NOMA) networks in which users are spatially randomly located is investigated. A new co-operative SWIPT NOMA protocol is proposed, in which near NOMA users that are close to the source act as energy harvesting relays to help far NOMA users. Since the locations of users have a significant impact on the performance, three user selection schemes based on the user distances from the base station are proposed. To characterize the performance of the proposed selection schemes, closed-form expressions for the outage probability and system throughput are derived. These analytical results demonstrate that the use of SWIPT will not jeopardize the diversity gain compared to the conventional NOMA. The proposed results confirm that the opportunistic use of node locations for user selection can achieve low outage probability and deliver superior throughput in comparison to the random selection scheme. <s> BIB007 </s> A Survey: Non-Orthogonal Multiple Access with Compressed Sensing Multiuser Detection for mMTC <s>  <s> The proliferation of smartphones/mobile devices that support a wide range of broadband applications and services has driven the volume of mobile data traffic to an unprecedented high level, requiring a next generation mobile communication system, i.e., the fifth generation (5G). Millimeter wave bands, due to the large available spectrum bandwidth, are considered as one of the most promising approaches to significantly boost the capacity. In this paper, we define a typical use case envisaged in the early stage of the 5G system rollout, where users can experience 100M+ data rate in the target area and at the same time enjoy services demanding extremely high data rates, such as virtual reality and ultra-high definition video. We then break down the use case into four different traffic types: web browsing, content sharing, virtual reality experience and ultra-high definition video, and derive and analyze the distributions of the required instantaneous data rates for each individual traffic type. Finally, we consider the case where multiple users with mixture of traffic types are simultaneously active and analyze the overall data rate and bandwidth requirements to support such a scenario. Keywords—5G; extreme data rate, immersive experience, millimeter wave, small cells, usage distribution functions <s> BIB008 </s> A Survey: Non-Orthogonal Multiple Access with Compressed Sensing Multiuser Detection for mMTC <s>  <s> Non-orthogonal multiple access (NOMA) is one of the promising radio access techniques for performance enhancement in next-generation cellular communications. Compared to orthogonal frequency division multiple access, which is a well-known high-capacity orthogonal multiple access technique, NOMA offers a set of desirable benefits, including greater spectrum efficiency. There are different types of NOMA techniques, including power-domain and code-domain. This paper primarily focuses on power-domain NOMA that utilizes superposition coding at the transmitter and successive interference cancellation at the receiver. Various researchers have demonstrated that NOMA can be used effectively to meet both network-level and user-experienced data rate requirements of fifth-generation (5G) technologies. From that perspective, this paper comprehensively surveys the recent progress of NOMA in 5G systems, reviewing the state-of-the-art capacity analysis, power allocation strategies, user fairness, and user-pairing schemes in NOMA. In addition, this paper discusses how NOMA performs when it is integrated with various proven wireless communications techniques, such as cooperative communications, multiple-input multiple-output, beamforming, space-time coding, and network coding among others. Furthermore, this paper discusses several important issues on NOMA implementation and provides some avenues for future research. <s> BIB009 </s> A Survey: Non-Orthogonal Multiple Access with Compressed Sensing Multiuser Detection for mMTC <s>  <s> Nonorthogonal multiple access (NOMA) represents a paradigm shift from conventional orthogonal multiple-access (MA) concepts and has been recognized as one of the key enabling technologies for fifth-generation mobile networks. In this paper, the impact of user pairing on the performance of two NOMA systems, i.e., NOMA with fixed power allocation (F-NOMA) and cognitive-radio-inspired NOMA (CR-NOMA), is characterized. For F-NOMA, both analytical and numerical results are provided to demonstrate that F-NOMA can offer a larger sum rate than orthogonal MA, and the performance gain of F-NOMA over conventional MA can be further enlarged by selecting users whose channel conditions are more distinctive. For CR-NOMA, the quality of service (QoS) for users with poorer channel conditions can be guaranteed since the transmit power allocated to other users is constrained following the concept of cognitive radio networks. Because of this constraint, CR-NOMA exhibits a different behavior compared with F-NOMA. For example, for the user with the best channel condition, CR-NOMA prefers to pair it with the user with the second best channel condition, whereas the user with the worst channel condition is preferred by F-NOMA. <s> BIB010 </s> A Survey: Non-Orthogonal Multiple Access with Compressed Sensing Multiuser Detection for mMTC <s>  <s> 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. <s> BIB011
low latency communication (URLLC), and (iii) massive machine type communication (mMTC). The enhanced mobile broadband is characterized by ubiquitous coverage with peak data rate of 20 Gbps and a latency of less than 10 ms BIB008 . The ultra-reliable and low latency communication is focused on enabling a variety of mission critical applications and tactile Internet applications, such as autonomous vehicle, remote industrial control and remote manufacturing with a latency requirement of less than 1 millisecond BIB005 . The mMTC aims at providing connectivity to massive low power and low data rate Internet of Things (IoT) devices which will open up enormous business opportunities in, e.g., building automation, smart agriculture, smart cities, fleet management, etc. It is expected that the number of such devices will rise to 50 billion by 2020 BIB001 which will result in the number of connections increased to one million per square kilometer  . In order to accommodate such huge number of devices, the network capacity needs to be significantly improved. The current orthogonal multiple access (OMA) such as time division multiple access (TDMA), frequency division multiple access (FDMA) and code division multiple access (CDMA) serves a single user in each orthogonal resource block. Therefore, the maximum number of simultaneously supported devices in an OMA scheme is limited by the number of orthogonal resources. For example, in orthogonal CDMA where orthogonal codes are assigned to the users, the maximum number of connected devices cannot exceeds the spreading factor. This orthogonality constraint makes the OMA schemes highly spectral inefficient for mMTC in 5G. Figure 1 shows resource allocation in OMA schemes where the resources assigned to the users are orthogonal to each other. Due to this orthogonality constraint, the current OMA based long term evolution (LTE) BIB002 can only support a fraction of the anticipated number of devices for future mMTC with its control channel element  . Furthermore, the sporadic transmission of small data packets in mMTC requires minimum control signaling overhead whereas LTE has a high cost of signaling overhead and high channel access latency for small data transmission. Therefore, connecting massive number of resource constrained devices to the network requires a paradigm shift in the multiple access technique. Non-orthogonal multiple access (NOMA) is a promising technique for massive connectivity which has attracted tremendous interest of researchers from both academia and industry. The NOMA schemes assign non-orthogonal resources to the users and therefore enable system overloading, i.e., allowing users to more efficiently share the same resources. The overloading capability of NOMA scheme is characterized by the overloading factor, which is the ratio of the total number of nodes to the total available orthogonal resources. At the receiver, advanced multiuser detection (MUD) techniques are deployed to separate the users. The NOMA schemes can be categorized into two main groups: the power domain NOMA and the code domain NOMA. Note that node and user are used interchangeably in this paper. In power domain NOMA, the users are assigned with different power levels which enable them to share the available resources, i.e., time, frequency or code BIB003 BIB009 . At the receiver, successive interference cancellation (SIC) is used for multiuser detection, which differentiates the users according to the assigned power levels. The resource allocation in power domain NOMA is shown in Figure 2 . It is depicted that at a given frequency, more than one users can transmit using different power levels. It is shown analytically in BIB004 that the NOMA outperforms the OMA techniques in terms of outage performance and ergodic sum rate. However, the user data rate and allocated power should carefully be chosen as the outage performance critically depends on them. NOMA improves the bandwidth efficiency; however, the fact that the cell-edge users, i.e., the users that are far from the BS, have poor channel conditions than the cell-centered users, i.e., users which are closer to the BS, causes performance degradation to the cell-edge users. This effect is mitigated by using cooperative NOMA BIB006 . In cooperative NOMA, the users having better channel conditions are paired with users having poor channel conditions. Figure 3 depicts a downlink scenario of cooperative NOMA in which a pair of users receives the superimposed signal in the first time slot. In the second time slot the cell-centered user acts as a relay and forwards the received signal to the cell-edge user. The whole task is completed in two time slots using cooperative NOMA which would take three time slots in cooperative OMA  . Cooperative NOMA improves the performance gain of NOMA; however, due to the extra process of relaying, the cell-centered users suffer from battery drainage. In machine type communication, the battery life is of significant importance as the MTC devices are mostly low power and the batteries once installed are rarely changed. To cope with this issue, in BIB007 , the concept of wireless energy transfer, i.e., the transfer of energy from the source to the destination through the air, is combined with cooperative NOMA. The proposed protocol is named as cooperative non-orthogonal multiple access with simultaneous wireless information and power transfer (cooperative SWIPT NOMA). In cooperative SWIPT NOMA, the cell-centered users harvest energy from the base station, which is used for the extra step of relaying, hence, reduces the battery drainage. Another variation in power domain NOMA is the introduction of cognitive radio (CR) concept BIB010 BIB011 . The conventional power domain NOMA ensures the user fairness; however, it cannot strictly guarantees the user's quality of service (QoS) targets. CR-NOMA ensures users QoS targets by designing power allocation policy according to the users QoS requirements. Although the power domain NOMA schemes outperform the OMA schemes, they have higher computational complexity due to the use of SIC. Furthermore, at low SNR the performance gain of power domain NOMA is insignificant BIB004 .