Showing papers on "Noma published in 2014"

On the Performance of Non-Orthogonal Multiple Access in 5G Systems with Randomly Deployed Users

Abstract: 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.

On the Performance of Non-Orthogonal Multiple Access in 5G Systems with Randomly Deployed Users

Abstract: 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.

Cooperative Non-Orthogonal Multiple Access in 5G Systems

Abstract: Non-orthogonal multiple access (NOMA) has recently received considerable 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 the other users. This prior knowledge is fully exploited in this paper, where a cooperative NOMA scheme is proposed. 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 in practice.

Multi-User Proportional Fair Scheduling for Uplink Non-Orthogonal Multiple Access (NOMA)

Abstract: Non-orthogonal multiple access (NOMA) is a promising radio access technique for LTE release 13 and beyond. In this paper, we focus on the investigation of the system performance for uplink NOMA with an advanced successive interference cancellation (SIC) receiver applied in the base station side. In NOMA, more than one user can be multiplexed simultaneously in the same frequency bandwidth, which demands multi-user scheduling. In our study, we propose an enhanced proportional fair (PF) based scheduling scheme for non-orthogonal multiplexed users with contiguous resource allocation to retain the SC-FDM property. In order to reduce the scheduling complexity for non-orthogonal multiple access, a greedy consecutive resource allocation method is adopted. Moreover, since the interference condition becomes more complicated in NOMA, we consider the application of fractional frequency reuse (FFR) to NOMA to further enhance the performance of cell-edge users. In simulation results, the system performance of NOMA by using the proposed PF-based scheduling algorithm is evaluated. The results show that NOMA significantly enhances the uplink system performance compared to the conventional orthogonal multiple access.

System-level performance of downlink NOMA combined with SU-MIMO for future LTE enhancements

Abstract: This paper investigates the system-level performance of downlink non-orthogonal multiple access (NOMA) combined with single user MIMO (SU-MIMO) for future LTE (Long-Term Evolution) enhancements. The goal is to clarify the performance gains of NOMA combined with SU-MIMO transmission, taking into account the LTE radio interface such as frequency-domain scheduling, adaptive modulation and coding (AMC), and NOMA specific functionalities such as multi-user pairing/ordering and transmit power allocation. In particular, we propose practical schemes to efficiently combine NOMA with open-loop SU-MIMO (Transmission Mode 3: TM3) and closed-loop SU-MIMO (Transmission Mode 4: TM4) specified in LTE. Based on computer simulations, we compare NOMA performance gains for different granularities of scheduling and MCS (modulation and coding scheme) selection, for both genie-aided channel quality information (CQI) estimation and approximated CQI estimation, and using different number of power sets. Evaluation results show that NOMA can still provide a hefty portion of its expected gains even with approximated CQI estimation and limited number of power sets, and also when LTE compliant subband scheduling and wideband MCS are applied.

Considerations on downlink non-orthogonal multiple access (NOMA) combined with closed-loop SU-MIMO

Abstract: As a promising downlink multiple access scheme for further cellular enhancements toward 5G, non-orthogonal multiple access (NOMA) improves both cell average and cell-edge user throughput compared to orthogonal multiple access (OMA) in the cellular downlink. When NOMA is combined with multi-antenna technology in practice, some aspects are of great interest, such as error propagation (EP) of successive interference cancellation (SIC) receiver and user velocity. This paper investigates the system-level throughput of NOMA with closed-loop single-user multiple-input multiple-output (SU-MIMO) in the cellular downlink and clarifies the potential gains over OMA with SU-MIMO taking into account these practical aspects. Two EP models are presented into the NOMA with closed-loop (CL) SU-MIMO. Their impacts on performance of NOMA with CL SU-MIMO are investigated by system-level simulations with practical assumptions. Furthermore, impact of user velocity on performance gain of NOMA with CL SU-MIMO is also evaluated. Simulation results show that even with the worst case EP model, NOMA with CL SU-MIMO can still provide large performance gains for both low and high mobility scenarios.

Noma (cancrum oris) in the South African context

Abstract: Noma (cancrum oris) is a destructive necrotising disease affecting orofacial tissues predominantly of malnourished young children. It is characterised by a rapid acute onset which usually starts in the mouth, spreads intra-orally destroying soft tissue and bone and progresses to perforate the facial skin, causing disfigurement. Polybacterial anaerobic infection is critical too, but is not alone sufficient for the initiation of noma. Cofactors, first and foremost malnutrition, but also systemic viral and bacterial infections are crucial to the development of noma. A patient with necrotising stomatitis or noma must be admitted to hospital for antibiotic treatment, fluid and electrolytes as well as nutritional supplementation and general supportive treatment. The epidemiology of noma in the South African population is unknown, and the clinicopathological features are poorly characterised. Although worldwide there is no evidence that HIV infection is a strong risk factor for noma, HIV infection may play a substantial role in the pathogenesis of noma in South Africa.

Performance Evaluation of Non-Orthogonal Multiple Access Combined with Opportunistic Beamforming

Abstract: Non-orthogonal multiple access (NOMA) utilizing power domain and advanced receiver is a promising technique for future radio access. Multi-antenna techniques have been deeply studied during the past decade to boost system performance by virtue of spatial multiplexing and/or spatial diversity. It is of great interest to study how to efficiently and effectively combine the two techniques together for further system performance improvement. This paper investigates on the combination of NOMA with opportunistic beamforming (OBF), which has been proposed as a practical multi-antenna transmission scheme with good performance and very limited feedback. The key design issues of NOMA with OBF are investigated including precoding, transmission power assignment, user feedback and scheduling. Furthermore, a method to improve the system performance with OBF is proposed by utilizing historical information. The performance of NOMA with OBF is investigated by system-level simulations with very practical assumptions and parameters in order to provide insights into the suitability of combining OBF with NOMA for future radio access. Simulation results show the proposed method is effective and NOMA with OBF is a promising scheme for future wireless communication systems.

Impact of rank optimization on downlink non-orthogonal multiple access (NOMA) with SU-MIMO

Abstract: Non-orthogonal multiple access (NOMA) is a promising radio access technique for further cellular enhancements toward the 5th generation (5G) mobile communication systems. Single-user multiple-input multiple-output (SU-MIMO) is one of the key technologies in long term evolution (LTE) /LTE-Advanced systems. It is proved that NOMA combined with SU-MIMO techniques can achieve further system performance improvement. In this paper, we focus on the impact of rank optimization on the performance of NOMA with SU-MIMO in downlink. Firstly, a geometry based rank adjustment method is studied. Secondly, an enhanced feedback method for rank adjustment is discussed. The simulation results show that the performance gain of NOMA improves with the proposed two rank adjustment methods. Compared to orthogonal access system, large performance gains can be achieved for NOMA, which are about 23% for cell average throughput and 33% for cell-edge user throughput.

Evaluations of downlink non-orthogonal multiple access (NOMA) combined with SU-MIMO

Abstract: Non-orthogonal multiple access (NOMA) is a promising radio access technique for further cellular enhancements toward 5G. Single-user multiple-input multiple-output (SU-MIMO) is one of the key technologies in LTE /LTE-Advanced systems. Thus, it is of great interest to study how to efficiently and effectively combine NOMA and SU-MIMO techniques together for further system performance improvement. This paper investigates the combination of NOMA with open-loop and closed-loop SU-MIMO. The key issues involved in the combination are presented and discussed, including scheduling algorithm, successive interference canceller (SIC) order determination, transmission power assignment and feedback design. The performances of NOMA with SU-MIMO are investigated by system-level simulations with very practical assumptions. Simulation results show that compared to orthogonal multiple access system, NOMA can achieve large performance gains both open-loop and closed-loop SU-MIMO, which are about 23% for cell average throughput and 33% for cell-edge user throughput.

Performance of MIMO-NOMA Downlink Transmissions

Abstract: In this paper, a non-orthogonal multiple access (NOMA) downlink scenario is considered, in which all nodes are equipped with multiple antennas. A new design of precoding and detection matrices for multiple-input-multiple-output (MIMO) downlink transmissions is proposed and its performance is analyzed by using the criteria of outage probabilities and diversity orders. To further enlarge the performance gap between MIMO-NOMA and conventional orthogonal multiple access schemes, user pairing is applied to NOMA and its impact on the system performance is characterized. Finally computer simulation results are provided to facilitate the performance evaluation of MIMO- NOMA and also demonstrate the accuracy of the developed analytical results.

Effect of joint detection and decoding in non-orthogonal multiple access

Abstract: Non-orthogonal multiple access (NOMA) can share the same frequency band with multiple mobile devices. In the conventional NOMA scheme, the possible pairs of users are limited and this limitation restricts the amount of capacity improvement. This is because the receiver only for the near user cancels the signal of the other user and then detect the desired signal. In this paper, a joint detection and decoding scheme in the far user of the NOMA downlink is proposed and its constellation constrained capacity (CCC) is evaluated through numerical analysis. The proposed scheme allows the pairing of users with the difference of the propagation losses of less than 8dB. The possible number of user pairs in the NOMA system then increases and a larger total capacity may be achievable.

Noma and cervicofacial necrotizing fasciitis: clinicopathological differentiation and an illustrative case report of noma.

Abstract: Noma predominantly affects malnourished young children. The pathogenesis of noma is complex and multifactorial, involving interaction between local polybacterial infection on the one hand, and malnutrition, immunosuppression, or systemic bacterial or viral infections on the other hand. Noma is considered to be an opportunistic disease, but the immediate cause is uncertain. Immunosuppression associated with a high HIV load may be an important risk factor in South Africa. Cervicofacial necrotizing fasciitis, on the other hand, occurs mainly in adults. It is frequently a consequence of an odontogenic infection and is characterized by an irregular pattern of rapidly spreading necrosis of fascia, muscle, and skin. We present an unusual case of noma in a 32-year-old malnourished HIV-seropositive female with AIDS in whom, within a period of 3 days, the initial intraoral necrotizing process spread rapidly and caused circular full thickness perforating destruction of the lower lip. Prompt diagnosis and tr...

A Survey on Non-orthogonal Multiple Access Schemes

Abstract: In this paper, we make a survey on non-orthogonal multiple access (NOMA) schemes, which could be a promising candidate as a downlink wireless access scheme for future 5G radio access technology. To enhance the spectrum efficiency, NOMA adopts a successive interference cancellation (SIC) receiver as the baseline receiver scheme for robust multiple access. In order to get a better tradeoff between the system spectrum efficiency measured by the total user throughput and the user fairness measured by cell-edge user throughput, fractional frequency (FFR) and resource management schemes have been applied to NOMA with SIC. Furthermore, multi-antenna/site technologies with a proposed NOMA/MIMO scheme using SIC and an interference rejection combing (IRC) receiver to get a further user capacity is discussed in some related papers. Finally, it is shown that even in relay channel, NOMA is still effective for system throughput enhancement.

A Novel Interference Cancellation Technique for Non-Orthogonal Multiple Access (NOMA)

Abstract: In this paper, a novel interference cancellation (IC) technique is proposed for asynchronous non-orthogonal multiple access (NOMA) systems. The bit error rate (BER) performance of an uplink NOMA system with the proposed IC technique is presented. Numerical and simulation results have shown that NOMA with the proposed asynchronous IC technique outperforms NOMA with a conventional-IC technique for uplink transmissions. It is also shown that employing iterative IC provides significant performance gain in NOMA and the number of required iterations depends on the modulation level and the received power ratio between users.

Noma affected children from Niger have distinct oral microbial communities based on high-throughput sequencing of 16S rRNA gene fragments.

Abstract: We aim to understand the microbial ecology of noma (cancrum oris), a devastating ancient illness which causes severe facial disfigurement in>140,000 malnourished children every year. The cause of noma is still elusive. A chaotic mix of microbial infection, oral hygiene and weakened immune system likely contribute to the development of oral lesions. These lesions are a plausible entry point for unidentified microorganisms that trigger gangrenous facial infections. To catalog bacteria present in noma lesions and identify candidate noma-triggering organisms, we performed a cross-sectional sequencing study of 16S rRNA gene amplicons from sixty samples of gingival fluid from twelve healthy children, twelve children suffering from noma (lesion and healthy sites), and twelve children suffering from Acute Necrotizing Gingivitis (ANG) (lesion and healthy sites). Relative to healthy individuals, samples taken from lesions in diseased mouths were enriched with Spirochaetes and depleted for Proteobacteria. Samples taken from healthy sites of diseased mouths had proportions of Spirochaetes and Proteobacteria that were similar to healthy control individuals. Samples from noma mouths did not have a higher abundance of Fusobacterium, casting doubt on its role as a causative agent of noma. Microbial communities sampled from noma and ANG lesions were dominated by the same Prevotella intermedia OTU, which was much less abundant in healthy sites sampled from the same mouths. Multivariate analysis confirmed that bacterial communities in healthy and lesion sites were significantly different. Several OTUs in the Orders Erysipelotrichales, Clostridiales, Bacteroidales, and Spirochaetales were identified as indicators of noma, suggesting that one or more microbes within these Orders is associated with the development of noma lesions. Future studies should include longitudinal sampling of viral and microbial components of this community, before and early in noma lesion development.

Oral medicine case book 65: Necrotising stomatitis

Abstract: Necrotising stomatitis is a fulminating anaerobic polybacterial infection affecting predominantly the oral mucosa of debilitated malnourished children or immunosuppressed HIV-seropositive subjects. It starts as necrotising gingivitis which progresses to necrotising periodontitis and subsequently to necrotising stomatitis. In order to prevent the progression of necrotising stomatitis to noma (cancrum oris), affected patients should be vigorously treated and may require admission to hospital. Healthcare personnel should therefore be familiar with the signs and symptoms of necrotising gingivitis/necrotising periodontitis, of their potential sequelae and of the need for immediate therapeutic intervention.

Noma neonatorum in a four month old baby with pseudomonas sepsis

Abstract: Sri Lanka Journal of Child Health , 2014; 43 (2): 110-111 (Key words: Noma; cancrum oris; noma neonatorum) DOI: http://dx.doi.org/10.4038/sljch.v43i2.7016

Acute gangrenous gingivitis--early stage noma.

Abstract: A 3-yearold boy presented with fever for 20 days. On day 5 of fever, he developed oral and angular mucosal ulcerations and redness. Blood counts showed a granulocytopenia. There was rapid progressive blackening of the labial and lingual surfaces of the gums and loosening of teeth for last 3 days (Fig. 1 and 2). We made a clinical diagnosis of acute necrotizing/gangrenous gingivitis. Acute necrotizing gingivitis, an early lesion of noma, begins as an inflammation of the marginal interdental papillae, to subsequently involve the mucosal surfaces of

Surgical options in the treatment of noma

Abstract: In the acute phase of noma, the role of surgery is minor and the treatment consists in the realisation of local or regional flaps and sometimes the management of haemorragia. For reasons social and economic reconstruction of the loss of substance should be conducted on site. The treatment consists of surgical excision of fibrous tissue, the removal of the ankylosis and the closure of the PDS by local flaps, or free pediculated. Because of the extreme variety of loss of substance (PDS) and the multiple surgical options, a systematic and eventually, the standardization of the surgical approach in the treatment of sequelae of noma is essential.

OPTIONS CHIRURGICALES DANS LA PRISE EN CHARGE DU NOMA Surgical options in the treatment of noma

Abstract: In the acute phase of noma, the role of surgery is minor and the treatment consists in the realisation of local or regional flaps and sometimes the management of haemorragia. For reasons social and economic reconstruction of the loss of substance should be conducted on site. The treatment consists of surgical excision of fibrous tissue, the removal of the ankylosis and the closure of the PDS by local flaps, or free pediculated. Because of the extreme variety of loss of substance (PDS) and the multiple surgical options, a systematic and eventually, the standardization of the surgical approach in the treatment of sequelae of noma is essential. Keywords : Noma, flap, loss of substance

Noma chez une enfant : une observation au Tchad Noma in a 4 year-old girl: a case report from Chad

Abstract: This case report describes a 4-year-old girl in Chad with noma, also called cancrum oris. This acute gangrenous stomatitis has a combined morbidity-mortality rate that can reach 70%. It occurs worldwide but is most common in sub- Saharan Africa in children aged 2 to 16 years. Its pathogenesis is uncertain, but several bacteria including Fusobacterium necrophorum, Prevotella intermedia and Pseudomonas aeruginosa may be responsible for the development of noma, which develops over the oral lesions these bacteria cause. Poverty is its most important risk factor. Due to its rapid course and high lethality, it requires emergency treatment with antibiotics, daily dress- ing of the lesion, and nutritional rehabilitation. Surgical removal of the remaining necrotic tissue can be followed by reconstructive procedures. Physical and speech therapy should be initiated to prevent functional complications.

[Noma in a 4 year-old girl: a case report from Chad].

Abstract: This case report describes a 4-year-old girl in Chad with noma, also called cancrum oris. This acute gangrenous stomatitis has a combined morbidity-mortality rate that can reach 70%. It occurs worldwide but is most common in sub-Saharan Africa in children aged 2 to 16 years. Its pathogenesis is uncertain, but several bacteria including Fusobacterium necrophorum, Prevotella intermedia and Pseudomonas aeruginosa may be responsible for the development of noma, which develops over the oral lesions these bacteria cause. Poverty is its most important risk factor. Due to its rapid course and high lethality, it requires emergency treatment with antibiotics, daily dressing of the lesion, and nutritional rehabilitation. Surgical removal of the remaining necrotic tissue can be followed by reconstructive procedures. Physical and speech therapy should be initiated to prevent functional complications.