Next Generation Wireless Multiple Access Technology OFDMA and SC - FDMA Performance Analysis
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orthogonal frequency division multiple access (OFDMA) and single carrier frequency division multiple access (SC - FDMA) are the two kinds of 4 g wireless multiple access scheme. In the long term evolution (LTE) downlink link access scheme based on OFDMA, at the same time, the uplink access scheme based on SC - FDMA. In this article, we deduced the OFDMA and SC - FDMA basic performance difference, and then demonstrates the comprehensive performance comparisons between them. Theoretical derivation results show that the system capacity is better than that of SC - FDMA OFDMA. Then, we use the numerical simulation results confirm the conclusion. Keywords: OFDMA SC - FDMA basic capacity of the uplink transmissionKeywords:
Frequency-division multiple access
This paper considers the problem of jointly compensating carrier frequency offsets (CFOs) and in-phase/quadrature-phase (I/Q) imbalance effects in orthogonal frequency-division multiple-access (OFDMA) or single-carrier frequency-division multiple-access (SC-FDMA) systems. Specifically, we propose a widely-linear time-varying minimum mean-output energy compensation scheme, by deriving its data-dependent frequency-shift implementation. The performance of the proposed receiver is assessed by Monte Carlo computer simulations.
Frequency-division multiple access
Carrier frequency offset
Quadrature (astronomy)
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The long term evolution (LTE) system employs orthogonal frequency division multiple access (OFDMA) and single carrier frequency division multiple access (SC-FDMA) for the downlink and uplink transmission, respectively. However, in most existing literatures regarding the two-way OFDMA resource allocation, all terminals are assumed under an OFDMA operation, and the allocation scheme is always considered solely under the frequency domain for subcarrier assignment. In this letter, a joint time and frequency resource allocation algorithm for the LTE two-way relaying is proposed, in which the permutation of the subframe and the resource block is discussed for augmenting the system capacity.
Frequency-division multiple access
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Resource Management
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In this paper, we propose a hybrid multiple-access scheme which combines IDMA (interleave division multiple access) and OFDMA (orthogonal frequency division multiple access), named OFDMA-IDMA. The advantages of this scheme are analyzed and the probable application scenarios are discussed. A scheduling method for uplink based on convergence analysis techniques is also proposed to group users to share the same time-frequency resources effectively.
Frequency-division multiple access
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Orthogonal frequency division multiple access (OFDMA) and Single Carrier Frequency Division Multiple Access (SC-FDMA) are the two major multiple access schemes for 4G wireless communications. In long term evolution (LTE) the downlink multiple access scheme is based on OFDMA and the uplink multiple access scheme is based on SC-FDMA. In this letter, we derive the fundamental performance difference between OFDMA and SC-FDMA, and present the general performance comparison between them. Analytical results show that OFDMA performance upper bounds SC-FDMA in the sense of capacity. The conclusion is further confirmed by numerical results.
Frequency-division multiple access
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In this paper, we present an analytical approach to design the inner region size for the fractional frequency reused (FFR) time division duplex (TDD) orthogonal frequency division multiple access (OFDMA) systems when supporting asymmetrical traffic services. In TDD system, supporting asymmetrical traffic can be achieved by adjusting the ratio of downlink and uplink transmission period. Nevertheless, the intercell interference may be deteriorated by the cross-slot interference resulting from the different downlink and uplink ratios among neighboring cells. Although the FFR technique can overcome the inter-cell interference, the impact of the cross-slot interference of TDD systems due to various downlink to uplink traffic ratios in different cells on the inner region size of a FFR-based OFDMA system is an open issue to our best knowledge. Intuitively, the larger the inner region of a FFR system, the higher the system capacity. Thus, this paper can provide a systematic method to determine the size of the inner region of FFR-based OFDMA system for different ratios of the downlink to uplink traffic among two neighbor cells.
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Frequency-division multiple access
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The Orthogonal Frequency Division Multiple Access (OFDMA) has recently emerged as one of the prime multiple access schemes for the future broadband wireless networks. In OFDMA, available subcarriers are grouped into subchannels, which are assigned to different users operating simultaneously. Preserving the orthogonality among these subchannels is essential, as it prevents the inter-carrier interference (ICI), which consequently eliminates multi-user interference (MUI). While the orthogonality among subchannels can be maintained relatively easily in the downlink, keeping the orthogonality in the uplink is much more difficult. In the uplink, the received signal is the sum of multiple signals coming from different users, each experiences a independent carrier frequency offset (CFO) due to oscillator instability and / or Doppler shift. Conventional CFO correction method used in the downlink are designed for single-user system, and therefore are not able to correct multiple CFOs in the uplink. The aim of this thesis is to provide practical solutions for the synchronization issues occurring in the uplink of the OFDMA-based broadband wireless systems. Several data-aided CFO estimation algorithms are proposed to achieve accurate measurements of the multiple CFOs in different scenarios. Once the estimates are available, novel MUI cancellation schemes are introduced to mitigate the selfand cross-interference occurring due to multiple CFOs. Evaluation results show that the proposed schemes outperform the existing techniques in literature with comparable or even lower additional complexity.
Carrier frequency offset
Orthogonality
WiMAX
Frequency-division multiple access
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본 논문에서는 다중 사용자 간 시간 동기 오차에 강인한 상향링크 OFDMA (Orthogonal Frequency Division Multiple Access) 두 기법, 즉, ZCZ (Zero Correlation Zone) 코드 시간축 확산 OFDMA 기법과 시간동기오차에 강한 SC-FDMA (Single Carrier Frequency Division Mmultiple Access)기법의 채널용량을 비교한다. 보다 현실적인 성능을 비교하기 위해 사용자 간 시간 동기 오차 뿐 아니라 상향링크 OFDMA 신호 생성의 가장 큰 이슈인 PAPR (Peak-to-Average Power Ratio)에 의한 신호의 왜곡효과도 함께 고려한다. 사용자 간 시간 동기 오차에 의 한 간섭이 존재하는 환경에서는 전력제어에 의해 증폭된 사용자들의 신호가 다른 사용자들의 신호에 큰 간섭으로 작용할 수 있다. 한편, 거리를 고려하여 증폭된 신호가 단말의 증폭기의 선형 증폭구간을 벗어나게 되면 신호의 왜곡이 발생하여 최종 성능의 저하를 발생시킬 수도 있다. 따라서, 기지국과 사용자 간의 거리만을 고려한 전력제어 방식이 아니라 최대 채널용량 성능을 갖게 하는 사용자 송신 전력 조합을 실험을 통해 찾는다. 즉, 사용자 단말의 전력 제한 수치와 사용자 시간 동기 오차의 최대범위 및 E b /E 0 등의 다양한 조합들에 대해 최대 채널용량 성능을 갖게 하는 송신전력 보정 계수(ASF: Adaptive Scaling Factor)을 실험을 통해 찾는다. 먼저, 송신전력 보정계수를 적용한 경우 두 상향링크 OFDMA 방식의 채널용량은 단순히 거리만을 고려한 전력제어 방식을 적용한 경우 즉, 송신전력 보정 계수=1인 경우에 비해 얼마나 높은 채널용량 성능을 가지는지 분석한다. 두 상향링크 OFDMA 방식의 채널용량 성능을 비교하면, 송신출력이 상대적으로 낮아도 되는 높은E b /E 0 환경에서는 시간 동기 오차에 보다 강인한 특성을 가진 ZCZ 코드 시간축 확산 OFDMA 기법의 채널용량 성능이 좋고, 반대로 상대적으로 높은 송신출력을 요구하는 낮은 E b /E 0 환경에서는 낮은 PAPR 특성을 갖는 시간동기오차에 강한 SC-FDMA 기법의 채널용량 성능이 보다 우수함을 다양한 실험을 통해 보인다.
Frequency-division multiple access
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orthogonal frequency division multiple access (OFDMA) and single carrier frequency division multiple access (SC - FDMA) are the two kinds of 4 g wireless multiple access scheme. In the long term evolution (LTE) downlink link access scheme based on OFDMA, at the same time, the uplink access scheme based on SC - FDMA. In this article, we deduced the OFDMA and SC - FDMA basic performance difference, and then demonstrates the comprehensive performance comparisons between them. Theoretical derivation results show that the system capacity is better than that of SC - FDMA OFDMA. Then, we use the numerical simulation results confirm the conclusion. Keywords: OFDMA SC - FDMA basic capacity of the uplink transmission
Frequency-division multiple access
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The 3GPP UTRA Long Term Evolution(LTE)selected Single Carrier Frequency Division Multiple Access(SC-FDMA) for uplink,and Orthogonal Frequency Division Multiple Access(OFDMA) for downlink.In this paper,the physical layer of the uplink is researched and simulated.Furthermore,the Frequency Domain Equalization(FDE) technology is specially studied for the high-speed wireless communication systems.The results indicate that the FDE technology can significantly improve the performance of anti-multipath interferences of the uplink.
Frequency-division multiple access
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중계기를 활용한 다중 입력 기술이 차세대 광대역 무선 이동 통신의 유력한 후보로 연구되고 있다. 본 논문에서는 채널 선택적 중계기 기반의 다중 입력 전송 시스템을 제안한다. 본 전송 시스템은 상하향 전송을 위해 SC-FDMA (Single Carrier Frequency Division Multiple Access)와 OFDMA (Orthogonal Frequency Division Multiple Access) 방식을 각각 채택한다. 단말기와 기지국 간 사용되는 부채널을 고정하고, 중계기와 단말기 또는 중계기와 기지국 사이의 채널 상태에 따라 선택적으로 부채널을 사용함으로써 수신 성능을 크게 향상시킬 수 있다. 실험 결과를 통해, 제안된 중계기 기반 시스템의 성능이 기존의 중계기 기반 시스템의 성능보다 우수함을 확인한다.
Frequency-division multiple access
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