Showing papers on "Noma published in 2015"
TL;DR: The concept of software defined multiple access (SoDeMA) is proposed, which enables adaptive configuration of available multiple access schemes to support diverse services and applications in future 5G networks.
Abstract: The increasing demand of mobile Internet and the Internet of Things poses challenging requirements for 5G wireless communications, such as high spectral efficiency and massive connectivity. In this article, a promising technology, non-orthogonal multiple access (NOMA), is discussed, which can address some of these challenges for 5G. Different from conventional orthogonal multiple access technologies, NOMA can accommodate much more users via nonorthogonal resource allocation. We divide existing dominant NOMA schemes into two categories: power-domain multiplexing and code-domain multiplexing, and the corresponding schemes include power-domain NOMA, multiple access with low-density spreading, sparse code multiple access, multi-user shared access, pattern division multiple access, and so on. We discuss their principles, key features, and pros/cons, and then provide a comprehensive comparison of these solutions from the perspective of spectral efficiency, system performance, receiver complexity, and so on. In addition, challenges, opportunities, and future research trends for NOMA design are highlighted to provide some insight on the potential future work for researchers in this field. Finally, to leverage different multiple access schemes including both conventional OMA and new NOMA, we propose the concept of software defined multiple access (SoDeMA), which enables adaptive configuration of available multiple access schemes to support diverse services and applications in future 5G networks.
2,512 citations
TL;DR: In this article, a cooperative NOMA scheme is proposed, where users with better channel conditions have prior information about the messages of other users, and an approach based on user pairing is also proposed to reduce system complexity.
Abstract: 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.
1,104 citations
TL;DR: Analytical results demonstrate that the use of SWIPT will not jeopardize the diversity gain compared to the conventional NOMA and 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.
Abstract: In this paper, the application of simultaneous wireless information and power transfer (SWIPT) to non-orthogonal multiple access (NOMA) networks in which users are spatially randomly located is investigated. A new cooperative 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.
595 citations
TL;DR: NOMA can be expected to efficiently exploit the near-far effect experienced in cellular environments and offer a better tradeoff between system efficiency and user fairness than orthogonal multiple access (OMA), which is widely used in 3.9 and 4G mobile communication systems.
Abstract: SUMMARY This paper presents our investigation of non-orthogonal multiple access (NOMA) as a novel and promising power-domain user multiplexing scheme for future radio access. Based on information theory, we can expect that NOMA with a successive interference canceller (SIC) applied to the receiver side will offer a better tradeoff between system efficiency and user fairness than orthogonal multiple access (OMA), which is widely used in 3.9 and 4G mobile communication systems. This improvement becomes especially significant when the channel conditions among the non-orthogonally multiplexed users are significantly different. Thus, NOMA can be expected to efficiently exploit the near-far effect experienced in cellular environments. In this paper, we describe the basic principle of NOMA in both the downlink and uplink and then present our proposed NOMA scheme for the scenario where the base station is equipped with multiple antennas. Simulation results show the potential system-level
518 citations
TL;DR: This letter proposes both optimal and low complexity suboptimal power allocation schemes to maximize the ergodic capacity of MIMO NOMA system with total transmit power constraint and minimum rate constraint of the weak user.
Abstract: Non-orthogonal multiple access (NOMA) is expected to be a promising multiple access technique for 5G networks due to its superior spectral efficiency. In this letter, the ergodic capacity maximization problem is first studied for the Rayleigh fading multiple-input multiple-output (MIMO) NOMA systems with statistical channel state information at the transmitter (CSIT). We propose both optimal and low complexity suboptimal power allocation schemes to maximize the ergodic capacity of MIMO NOMA system with total transmit power constraint and minimum rate constraint of the weak user. Numerical results show that the proposed NOMA schemes significantly outperform the traditional orthogonal multiple access scheme.
439 citations
11 May 2015
TL;DR: A novel NOMA transmitter and receiver design, where the signals of multi-users are jointly modulated at transmitter side and detected at receiver side is proposed and low complexity is achieved.
Abstract: Non-orthogonal multiple access (NOMA) is one of the promising radio access techniques for further cellular enhancements toward 5G Compared to orthogonal multiple access (OMA) such as orthogonal frequency-division multiple access (OFDMA), large performance gains were confirmed via system-level simulations However, NOMA link-level simulations and the design of the receiver remain of great importance to validate NOMA performance gains In this paper, we evaluate downlink NOMA link-level performance with multiple receiver designs and propose a novel NOMA transmitter and receiver design, where the signals of multi-users are jointly modulated at transmitter side and detected at receiver side The predominant advantage of the proposed scheme is that at receiver side interference cancellation to the interference signal is not needed, thus low complexity is achieved The performances of codeword-level SIC, symbol-level SIC and the proposed receiver are evaluated and compared with ideal SIC Simulation results show that compared with ideal SIC, downlink NOMA link-level performance depends on actual receiver design and the difference in the power ratio split between the cell edge user and cell center user In particular, it is shown that codeword-level SIC and the proposed receiver can both provide a good performance even when the power ratio difference between the cell center user and cell edge user is small and with real channel estimation
139 citations
01 Sep 2015
TL;DR: Based on a realistic indoor channel conditions, NOMA is applied to indoor VLC channels and demonstrated its superior performance over orthogonal frequency division multiple access (OFDMA).
Abstract: Providing multiple access support to visible light communication (VLC) systems requires new networking architecture. Non-orthogonal multiple access (NOMA) is a proposed multiple access technique for future cellular systems. In this work, based on a realistic indoor channel conditions, we apply NOMA to indoor VLC channels and demonstrate its superior performance over orthogonal frequency division multiple access (OFDMA).
137 citations
Patent•
27 Mar 2015TL;DR: In this article, the authors present a protocol instruction that indicates an OMA transmission or a NOMA transmission based on the metrics and determines a first modulation and coding scheme for a first UE and a second MCS for a second UE.
Abstract: Apparatuses and methods for Non-Orthogonal Multiple Access (NOMA) communication are discussed. An example Evolved NodeB (eNB) includes a memory, a processor, and a transmitter circuit. The processor evaluates an orthogonal multiple access (OMA) metric and a NOMA metric, generates a protocol instruction that indicates an OMA transmission or a NOMA transmission based on the metrics, and determines a first modulation and coding scheme for a first UE and a second MCS for a second UE. The transmitter circuit receives the protocol instruction and transmits a first data signal and a first downlink control information (DCI) message associated with the first UE, and a second data signal and a second DCI message associated with the second UE. When the protocol instruction indicates NOMA transmission, the data signals are power multiplexed, the DCI messages indicate the data signals are transmitted via NOMA, and the first DCI message indicates the second MCS.
98 citations
01 Oct 2015
TL;DR: The goal is to clarify the benefits of NOMA over orthogonal multiple access (OMA) such as OFDMA adopted by Long-Term Evolution (LTE), also its combination with MIMO is discussed.
Abstract: Non-orthogonal multiple access (NOMA) has been attracting a lot of attention as a promising downlink multiple access scheme for LTE enhancements and 5G. This paper introduces an overview of the concept, performance evaluation gains and our experimental trials related to NOMA. The goal is to clarify the benefits of NOMA over orthogonal multiple access (OMA) such as OFDMA adopted by Long-Term Evolution (LTE), also its combination with MIMO is discussed. Using computer simulations, NOMA performance gains are assessed from both link-level and system-level perspectives. Also, our NOMA test-bed and the measurement results are explained. Our evaluation results and measurements show that NOMA provides higher gains compared to OFDMA. These gains are more than 30%.
95 citations
TL;DR: In a wireless downlink scenario with user pairing, the developed analytical results show that NOMA can outperform TDMA not only in Terms of the sum rate but also in terms of each user's individual rate, particularly when the difference between the users' channels is large.
Abstract: In this paper, a new evaluation criterion is developed to investigate the performance of non-orthogonal multiple access (NOMA) from an information theoretic point of view. In particular, the relations among the capacity region of the broadcast channel and two rate regions achieved by NOMA and time-division multiple access (TDMA) are first illustrated. Based on these relations, a new evaluation criterion is proposed for NOMA in wireless fading scenarios, where the key idea is to compare NOMA with TDMA statistically in terms of not only the sum rate but also the individual rates. In a wireless downlink scenario with user pairing, the developed analytical results show that NOMA can outperform TDMA not only in terms of the sum rate but also in terms of each user’s individual rate, particularly when the difference between the users’ channels is large. The optimal power allocation for a special case of NOMA user pairing is also established.
86 citations
01 Oct 2015
TL;DR: The goal is to clarify the benefits of NOMA over orthogonal multiple access (OMA) such as OFDMA adopted by Long-Term Evolution (LTE), also its combination with MIMO is discussed.
Abstract: As a promising downlink multiple access scheme for LTE enhancements and 5G, non-orthogonal multiple access (NOMA) has been attracting a lot of attention in recent years. This paper introduces an overview of the concept, performance evaluation gains, our ongoing experimental trials and current standardization status. The goal is to clarify the benefits of NOMA over orthogonal multiple access (OMA) such as OFDMA adopted by Long-Term Evolution (LTE), also its combination with MIMO is discussed. Using computer simulations, NOMA performance gains are assessed from both link-level and system-level perspectives. Also, our NOMA testbed and the measurement results are explained. Finally, we summarize the current status of ongoing standardization of downlink NOMA, which is currently under study in 3GPP LTE Release 13.
11 May 2015
TL;DR: Based on computer simulations, it is shown that for both macrocell and small cell deployments, NOMA can still provide a larger throughput performance gain compared to that for OMA.
Abstract: Non-orthogonal multiple access (NOMA) is a promising multiple access scheme for further improving the spectrum efficiency compared to that for orthogonal multiple access (OMA) in the 5th Generation (5G) mobile communication systems. All of the existing evaluations for NOMA focus on the macrocell deployment since NOMA fully utilizes the power domain and the difference in channel gains, e.g., path loss, between users, which is typically sufficiently large in macrocells. Currently, small cells are becoming important and being studied for future Long-Term Evolution (LTE) enhancements in order to improve further the system performance. Thus, it is of great interest to study the performance of NOMA for small cell deployment under various environments. This paper investigates the system level performance of NOMA in small cells considering practical assumptions such as the single user multiple-input multiple-output (SU-MIMO) technique, adaptive modulation and coding (AMC), feedback channel quality indicator (CQI). Some of the key NOMA specific functionalities, including multi-user paring and transmit power allocation are also taken into account in the evaluation. Based on computer simulations, we show that for both macrocell and small cell deployments, NOMA can still provide a larger throughput performance gain compared to that for OMA.
TL;DR: The achievable system-level gains of NOMA are shown promising even when practical considerations were taken into account, and future enhancements of spectrum efficiency in lower frequency bands for downlink of 5G system are presented.
Abstract: Multiple access (MA) technology is of most importance for 5G. Non-orthogonal multiple access (NOMA) utilizing power domain and advanced receiver has been considered as a promising candidate MA technology recently. In this paper, the NOMA concept is presented toward future enhancements of spectrum efficiency in lower frequency bands for downlink of 5G system. Key component technologies of NOMA are presented and discussed including multiuser transmission power allocation, scheduling algorithm, receiver design and combination of NOMA with multi-antenna technology. The performance gains of NOMA are evaluated by system-level simulations with very practical assumptions. Under multiple configurations and setups, the achievable system-level gains of NOMA are shown promising even when practical considerations were taken into account.
TL;DR: All recent articles on noma from January 2003 to August 2014 are reviewed and briefly update the latest information related to the topic to prevent the disease and provide an early intervention.
Abstract: Noma is a gangrenous infection primarily affecting under developed countries The aim of this paper was to review all recent articles on noma from January 2003 to August 2014 and briefly update the latest information related to the topic A literature search was done on PUBMED using the keywords "noma/cancrum oris" Noma is commonly seen in malnourished children There has been an increased incidence of noma in HIV patients Apart from these, noma has also been reported in association with cyclic neutropenia, herpetic stomatitis, leukemia, Down's syndrome and Burkett's disease Treatment of acute noma includes transfusion of blood and intravenous fluids, administration of antibiotics, putting the patient on a high protein diet and debridement of necrotic areas Surgical phase is usually initiated 6 to 18 months after a period of quiescence Although, the mortality rate associated with noma has reduced significantly with the advent of modern generation antibiotics, the functional, cosmetic and psychological challenges associated with the destruction of soft or hard tissues still remains a huge challenge Adequate steps must be implemented by the government or medical professionals to prevent the disease and provide an early intervention
08 Jun 2015
TL;DR: Simulation results show that the proposed user selection algorithm and the power schedule scheme can improve the sum-rate of NOMA based downlink multi-user system.
Abstract: As a promising multiple access techniques for 5th generation (5G) wireless systems, non-orthogonal multiple access (NOMA) has received many attentions recently. In this paper, we study the NOMA based downlink multi-user beamforming system, where the base station (BS) tries to transmit information to multiple user clusters and each beam serves one user cluster compromising of two users simultaneously. User selection algorithm is proposed to reduce the interference and improve the system information rate. Moreover, we also provide the user power schedule scheme to guarantee the advantage of the proposed NOMA downlink multi-user beamforming system. Simulation results show that the proposed user selection algorithm and the power schedule scheme can improve the sum-rate of NOMA based downlink multi-user system.
TL;DR: The state of the art in open source SDR is introduced and non-orthogonal multiple access (NOMA) is one of the candidate radio access techniques for improving spectral efficiency in the 5G mobile network through multiplexing users in the power domain.
Abstract: With the rapid advent of various new applications and services, the anticipated use of bandwidth and frequency resources is beyond expectation in future mobile networks. To maximize spectral efficiency, novel radio access techniques need to multiplex users in the most suitable combinations of frequency and radio resources. Non-orthogonal multiple access (NOMA) is one of the candidate radio access techniques for improving spectral efficiency in the 5G mobile network through multiplexing users in the power domain, which has never been explored in past and current communications systems. While the concept of NOMA was proposed several years ago, the performance of NOMA has only been verified in theory but not in practice. In this article, we first introduce the state of the art in open source SDR. Due to the high flexibility and reconfigurability of open source SDR, we choose general-purpose-processor-based SDR to implement our NOMA system, which is based on an open source LTE program. Over-the-air experiments are carried out on the designed NOMA system for the purpose of performance evaluation, and to demonstrate its potential in future 5G mobile networks.
Posted Content•
TL;DR: In this article, the authors provide a systematic treatment of NOMA, from its combination with multiple-input multiple-output (MIMO) technologies, to cooperative and non-orthogonal multiple access (NOMA) and cognitive radio.
Abstract: As the latest member of the multiple access family, non-orthogonal multiple access (NOMA) has been recently proposed for 3GPP Long Term Evolution (LTE) and envisioned to be an essential component of 5th generation (5G) mobile networks. The key feature of NOMA is to serve multiple users at the same time/frequency/code, but with different power levels, which yields a significant spectral efficiency gain over conventional orthogonal MA. This article provides a systematic treatment of this newly emerging technology, from its combination with multiple-input multiple-output (MIMO) technologies, to cooperative NOMA, as well as the interplay between NOMA and cognitive radio. This article also reviews the state of the art in the standardization activities concerning the implementation of NOMA in LTE and 5G networks.
28 Aug 2015
TL;DR: An iterative multiuser detection and decoding (MUDD) and a novel subcarrier and power allocation algorithm is proposed for NOMA scheme that maximizes the users' weighted sum-rate and achieves the system spectral efficiency upper-bound.
Abstract: Non-Orthogonal Multiple Access (NOMA) is a promising multiple access technique for 5G wireless networks. In uplink NOMA, more than one user can use the same subcarrier, which increases the system throughput and fairness. Due to the non-orthogonality among the users, joint processing is required at the receiver to retrieve the users' signals. In this paper, we propose solutions to optimize the receiver and the radio resource allocation of uplink NOMA. First, we propose an iterative multiuser detection and decoding (MUDD) to improve the performance of the multiuser detector by utilizing the information derived by the channel decoder. In addition, a novel subcarrier and power allocation algorithm is proposed for NOMA scheme that maximizes the users' weighted sum-rate. The link-level performance evaluation has shown that the proposed iterative MUDD approach brings about 4.5 dB and 9.8 dB performance improvements at block error rate equal to 10−2 comparing to conventional multiuser detection, for QPSK and 16QAM modulations, respectively. Furthermore, the system-level results show that the proposed resource allocation algorithm achieves the system spectral efficiency upper-bound, making NOMA significantly outperforms OFDMA in terms of spectral efficiency and fairness.
28 Dec 2015
TL;DR: The diversity of both the near and far users is analyzed to demonstrate that the use of SWIPT will not jeopardize the diversity order compared to the conventional NOMA, and new analytical expressions for outage probability are derived.
Abstract: In this paper, the application of simultaneous wireless information and power transfer (SWIPT) to non-orthogonal multiple access (NOMA) is investigated. A new cooperative SWIPT NOMA protocol is proposed in which near NOMA users which are close to the source act as energy harvesting relays to help far NOMA users. By assuming that all users are spatially randomly located in the network, new analytical expressions for outage probability are derived both for the near and far users, in order to characterize the performance of the proposed protocol. The diversity of both the near and far users is analyzed to demonstrate that the use of SWIPT will not jeopardize the diversity order compared to the conventional NOMA. Numerical results are also provided to verify the accuracy of the developed analytical results.
05 Oct 2015
TL;DR: A user-pairing based suboptimal scheme for uplink multiple-access is proposed by combining NOMA and OMA to facilitate the massive-access scenes and shows only a little throughput loss comparing to the optimal transmission scheme in information-theoretic perspective.
Abstract: Non-orthogonal multiple access (NOMA) scheme is a key technique towards the 5th generation (5G) of wireless communication networks due to its higher spectral efficiency comparing to its orthogonal multiple access (OMA) counterpart However, the complexity of conventional NOMA scheme is extremely high in massive-access scenes In this paper, we propose a user-pairing based suboptimal scheme for uplink multiple-access by combining NOMA and OMA to facilitate the massive-access scenes Furthermore, a user-pairing algorithm with O(nlogn) complexity is also derived According to the Monte Carlo simulation, the proposed scheme shows only a little throughput loss comparing to the optimal transmission scheme in information-theoretic perspective
03 Dec 2015
TL;DR: Simulation results show the proposed HARQ algorithm is effective and can achieve better performance than the existing algorithm and the (wrong, correct) is the dominate case in NOMA HARQ and thus is of most importance for enhanced NOMa HARQ design.
Abstract: Non-orthogonal multiple access (NOMA) utilizing power domain and advanced receiver has been considered as a very promising candidate radio access technology for future wireless communication systems. Hybrid automatic repeat request (HARQ), as an indispensable part of link adaptation, plays a very important role in reliable high speed packet data service through exploiting retransmission diversity and channel coding gain. In this paper, we investigate HARQ design for downlink NOMA with single user-multiple input multiple output (SU-MIMO). The impacts of user pairing, precoding matrix adaptation and transmission power assignment (TPA) ratio adaptation in retransmission on NOMA performance are investigated. An enhanced HARQ algorithm is proposed, where opportunistically HARQ combining is applied and the TPA of retransmission considers HARQ combining gain of the retransmission user. It is found that HARQ probability of NOMA is much higher than that of OMA and flexible retransmission strategies could increase performance gain of NOMA. Furthermore, it found the (wrong, correct) is the dominate case in NOMA HARQ and thus is of most importance for enhanced NOMA HARQ design. Simulation results show the proposed HARQ algorithm is effective and can achieve better performance than the existing algorithm.
03 Dec 2015
TL;DR: The simulation results show that performance gains of NOMA can be improved with SIC processing at cell-edge UEs, and indicates that more advanced receiver can be considered for cell- edge UE to achieve upper-bound performance.
Abstract: Non-orthogonal multiple access (NOMA) utilizing transmit power difference and advanced successive interference canceller (SIC) receivers has been considered as a candidate radio access technology for future wireless communication systems. Single-user multiple-input multiple-output (SU-MIMO) is one of the key technologies in Long-Term-Evolution (LTE) systems. Thus, it has been proved to combine with NOMA for further system performance improvement. In previous studies, SIC receiver is adopted at cell center users (UEs), while SIC processing is not taken into account at cell-edge UEs, considering the feasibility of UE receiver and control signaling overhead. However, it may put limitation on the performance of NOMA. To further enhance the performance of NOMA with SU-MIMO, advanced receiver can be considered at cell-edge UEs. In this paper, we investigate the impact of applying the SIC receiver at cell-edge UEs in downlink NOMA with SU-MIMO. The detail SIC detection schemes at cell-edge UE will be discussed, including ideal SIC processing and non-ideal SIC processing. The simulation results show that performance gains of NOMA can be improved with SIC processing at cell-edge UEs. It indicates that more advanced receiver can be considered for cell-edge UE to achieve upper-bound performance.
TL;DR: The end of neglect of noma can lead to the elimination of this horrific childhood disease, a biological indicator of multiple human rights violations, including the right to food.
Patent•
19 Oct 2015
TL;DR: In this paper, an eNodeB (eNB), user equipment (UE) and method of providing a quasi-orthogonal multiple access (QOMA) resources are generally described.
Abstract: An eNodeB (eNB), user equipment (UE) and method of providing a quasi-orthogonal multiple access (QOMA) resources are generally described. The UE receives allocation of orthogonal multiple access (OMA) and non-OMA (NOMA) resources. The UE transmits data up to a maximum NOMA rate and NOMA Modulation and Coding Scheme (MCS) using the NOMA resources without receiving an explicit transmission grant from the eNB. The eNB may allocate multiple NOMA regions associated with different maximum rates, MCSs, number of UEs, UE types, applications and sizes. If the data exceeds the NOMA conditions or the UE is unable to transmit data using the allocated NOMA resources or does not receive an acknowledgement from the eNB regarding reception of the transmitted data, the UE may request an explicit grant of the OMA resources from the eNB and, upon receiving an allocation of the OMA resources, subsequently transmit the data using the allocated OMA resources.
TL;DR: A case of noma is reported in an immunocompetent man who presented to an urban hospital in the United States, with the highest incidence occurring in the noma belt, which extends from sub-Saharan West Africa to central Sudan.
Abstract: Noma, also known as cancrum oris or the face of poverty, is a rapidly progressive polymicrobial opportunistic infection resulting in orofacial gangrene and eventually death if untreated. The etiopathogenesis of the disease has been attributed to extreme malnutrition, dehydration, and inadequate oral hygiene.1, 2 Noma is primarily observed among children younger than 6 years in countries with a low human development index, with the highest incidence occurring in the noma belt, which extends from sub-Saharan West Africa to central Sudan.3 Cases in adults and citizens of high income countries are exceedingly rare and have been limited to those with immunodysfunction.4, 5, 6 We report a case of noma in an immunocompetent man who presented to an urban hospital in the United States.
01 Oct 2015
TL;DR: It is shown that for the non-full buffer case, NOMA can still provide a large performance gain compared to that of orthogonal multiple access (OMA) in particular for small packet sizes, and it is also shown that under full buffer traffic model, α-fair gradient scheduler is able to trade-off between average user packet throughput and 5% user packets throughput; however, this does not hold for the case of non- fullbuffer traffic model.
Abstract: For the past few years, we proposed non-orthogonal multiple access (NOMA) as a promising multiple access scheme for further improvement of spectrum efficiency for LTE enhancements and the 5th generation mobile communications system (5G). Currently, the system performance of NOMA, considering practical assumptions, different deployment scenarios and NOMA specific functionalities, including multi-user pairing, transmit power allocation, and combination with MIMO is being evaluated and discussed in academia, industry, and standardization [5-16]. In addition, the most of existing evaluations for NOMA focus on the full buffer traffic model, which is widely adopted for the evaluation of mobile radio access system. However, further investigations with non-full buffer traffic model are also important to clarify the system performance of NOMA for different types of the traffic. This paper investigates the system-level performance of NOMA with non-full buffer traffic model for different levels of packet arrival rates and sizes. In addition, the impact of the scheduling algorithm such as α-fair gradient scheduler, which controls the fairness level of the resource allocation, is also discussed. Based on computer simulations, we show that for the non-full buffer case, NOMA can still provide a large performance gain compared to that of orthogonal multiple access (OMA) in particular for small packet sizes. It is also shown that under full buffer traffic model, α-fair gradient scheduler is able to trade-off between average user packet throughput and 5% user packet throughput; however, this does not hold for the case of non-full buffer traffic model.
01 Nov 2015
TL;DR: Simulation results shows that proposed scheme achieves superior spectral efficiency as compare to conventional NOMA, and reduces number of decoding steps at NomA users, cell edge interference reduces as no power is allocated to cell edge users and hence is more energy efficient as compared to conventionalNOMA.
Abstract: Non-orthogonal multiple access (NOMA) is a promising candidate for 5G networks. NOMA achieves superior spectral efficiency than conventional orthogonal multiple access (OMA), as in NOMA multiple users can use the same time and frequency resources. Multiple-Input-multiple-output is a promising technique that can enhance system performance. In this paper we present a multiple antenna based NOMA, known as spatially modulated NOMA. In proposed scheme different users are multiplexed in power domain while cell edge users are multiplexed in spatial domain. The information to cell edge users are conveyed using antenna indices thereby reduces number of decoding steps at NOMA users, cell edge interference reduces as no power is allocated to cell edge users and hence is more energy efficient as compare to conventional NOMA. Simulation results shows that proposed scheme achieves superior spectral efficiency as compare to conventional NOMA.
01 Dec 2015
TL;DR: An alternate receiver structure for downlink NOMA based on parallel interference cancellation (PIC) is proposed, along with some design consideration factors, and the simulation results show that the proposed receiver outperforms that with SIC and hence is a promising Receiver structure for future 5G downlinkNOMA.
Abstract: Non-orthogonal multiple access (NOMA) is considered as a promising multiple access scheme for 5G downlink transmission In this paper, we first review the existing downlink NOMA with successive interference cancellation (SIC) and then highlight some of the critical performance limiting factors related to SIC which can result in the performance degradation of NOMA In order to alleviate the problems posed by SIC, we propose an alternate receiver structure for downlink NOMA based on parallel interference cancellation (PIC), along with some design consideration factors The simulation results show that the proposed receiver outperforms that with SIC and hence is a promising receiver structure for future 5G downlink NOMA
TL;DR: A case of clinically diagnosed cancrum oris in a 2-year old child in sub-saharan Africa that was conservatively managed by wound care and hyperalimentation is presented.
TL;DR: Grouping users can reduce both the inter-user interference and residual interference due to the SIC error, so it can outperform conventional NOMA system, especially in case that the number of users and the S IC error increase.
Abstract: Non-orthogonal multiple access (NOMA) where all users share the entire time and frequency resource has paid attention as one of the key technologies to enhance the spectral efficiency and the total throughput. Nevertheless, as the number of users and SIC error increase, the inter-user interference and the residual interference due to the SIC error also increase, resulting in performance degradation. In order to mitigate the performance degradation, we propose grouping-based NOMA system. In the proposed scheme, all users are divided into two groups based on the distance between the BS and each user, where one utilizes the first half of the bandwidth and the other utilizes the rest in the orthogonal manner. On the other hand, users in each group share the spectrum in the non-orthogonal manner. Grouping users can reduce both the inter-user interference and residual interference due to the SIC error, so it can outperform conventional NOMA system, especially in case that the number of users and the SIC error increase. Based on that, we also present the hybrid operation of the conventional and the proposed NOMA systems. In numerical results, the total throughput of the proposed NOMA systems is compared with that of the conventional NOMA systems with regard to the number of users and SIC error. It is confirmed that the proposed NOMA system outperforms the conventional NOMA system as the number of users and the SIC error increase.