Half-ZF beamforming scheme for downlink two-user multiple input single output-based non-orthogonal multiple access systems

2017 ◽  
Vol 11 (10) ◽  
pp. 1633-1640 ◽  
Author(s):  
Wenbo Cai ◽  
Guocheng Lv ◽  
Ye Jin
Keyword(s):  
Multiple Access ◽  
Single Output ◽  
Multiple Input

scholarly journals Nearest Neighbor Decoding and Pilot-Aided Channel Estimation for Fading Channels

Entropy ◽  
2020 ◽  
Vol 22 (9) ◽  
pp. 971
Author(s):  
A. Taufiq Asyhari ◽  
Tobias Koch ◽  
Albert Guillén i Fàbregas
Keyword(s):  
Channel Estimation ◽  
Fading Channels ◽  
Multiple Access ◽  
Nearest Neighbor ◽  
Signal To Noise Ratio ◽  
Multiple Input Multiple Output ◽  
Comparative Performance ◽  
Single Output ◽  
Multiple Input ◽  
Flat Fading

We study the information rates of noncoherent, stationary, Gaussian, and multiple-input multiple-output (MIMO) flat-fading channels that are achievable with nearest neighbor decoding and pilot-aided channel estimation. In particular, we investigate the behavior of these achievable rates in the limit as the signal-to-noise ratio (SNR) tends to infinity by analyzing the capacity pre-log, which is defined as the limiting ratio of the capacity to the logarithm of the SNR as the SNR tends to infinity. We demonstrate that a scheme estimating the channel using pilot symbols and detecting the message using nearest neighbor decoding (while assuming that the channel estimation is perfect) essentially achieves the capacity pre-log of noncoherent multiple-input single-output flat-fading channels, and it essentially achieves the best so far known lower bound on the capacity pre-log of noncoherent MIMO flat-fading channels. Extending the analysis to fading multiple-access channels reveals interesting relationships between the number of antennas and Doppler bandwidth in the comparative performance of joint transmission and time division multiple-access.

scholarly journals Random Beam-Based Non-Orthogonal Multiple Access for Low Latency K-User MISO Broadcast Channels

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4373
Author(s):  
Jung Hoon Lee ◽  
Yunjoo Kim ◽  
Jong Yeol Ryu
Keyword(s):  
Multiple Access ◽  
Broadcast Channels ◽  
Low Latency ◽  
Noise Power ◽  
User Grouping ◽  
Single Antenna ◽  
Single Output ◽  
Multiple Input ◽  
Single User ◽  
Random Beamforming

In this paper, we propose random beam-based non-orthogonal multiple access (NOMA) for low latency multiple-input single-output (MISO) broadcast channels, where there is a target signal-to-interference-plus-noise power ratio (SINR) for each user. In our system model, there is a multi-antenna transmitter with its own single antenna users, and the transmitter selects and serves some of them. For low latency, the transmitter exploits random beams, which can reduce the feedback overhead for the channel acquisition, and each beam can support more than a single user with NOMA. In our proposed random beam-based NOMA, each user feeds a selected beam index, the corresponding SINR, and the channel gain, so it feeds one more scalar value compared to the conventional random beamforming. By allocating the same powers across the beams, the transmitter independently selects NOMA users for each beam, so it can also reduce the computational complexity. We optimize our proposed scheme finding the optimal user grouping and the optimal power allocation. The numerical results show that our proposed scheme outperforms the conventional random beamforming by supporting more users for each beam.

scholarly journals Optimized Scheduling Technique of Null Subcarriers for Peak Power Control in 3GPP LTE Downlink

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Soobum Cho ◽  
Sang Kyu Park
Keyword(s):  
Power Efficiency ◽  
Multiple Access ◽  
Mimo Systems ◽  
Multiple Input Multiple Output ◽  
Average Power ◽  
Papr Reduction ◽  
Single Input Single Output ◽  
Single Output ◽  
Multiple Input ◽  
Input Multiple Output

Orthogonal frequency division multiple access (OFDMA) is a key multiple access technique for the long term evolution (LTE) downlink. However, high peak-to-average power ratio (PAPR) can cause the degradation of power efficiency. The well-known PAPR reduction technique, dummy sequence insertion (DSI), can be a realistic solution because of its structural simplicity. However, the large usage of subcarriers for the dummy sequences may decrease the transmitted data rate in the DSI scheme. In this paper, a novel DSI scheme is applied to the LTE system. Firstly, we obtain the null subcarriers in single-input single-output (SISO) and multiple-input multiple-output (MIMO) systems, respectively; then, optimized dummy sequences are inserted into the obtained null subcarrier. Simulation results show that Walsh-Hadamard transform (WHT) sequence is the best for the dummy sequence and the ratio of 16 to 20 for the WHT and randomly generated sequences has the maximum PAPR reduction performance. The number of near optimal iteration is derived to prevent exhausted iterations. It is also shown that there is no bit error rate (BER) degradation with the proposed technique in LTE downlink system.

scholarly journals Konsep Transmisi Tidak Koheren menggunakan Differential Unitary Modulation pada OFDMA

2021 ◽  
Vol 9 (3) ◽  
pp. 634
Author(s):  
DHONI PUTRA SETIAWAN ◽  
HARFAN HIAN RYANU ◽  
VINSENSIUS SIGIT WIDHI PRABOWO
Keyword(s):  
Multiple Access ◽  
High Mobility ◽  
Block Code ◽  
Differential Modulation ◽  
Frequency Division ◽  
Single Input Single Output ◽  
Single Output ◽  
Multiple Input ◽  
Modulation Techniques ◽  
Single Input

ABSTRAKDifferential modulation adalah sebuah teknik modulasi yang memungkinkan pengiriman informasi tanpa diperlukannya estimasi kondisi kanal di sisi penerima. Teknik ini biasa diimplementasikan pada kondisi dimana kanal transmisi berubah dengan sangat cepat, seperti ketika pengguna layanan dalam kondisi mobilitas yang sangat cepat. Pada artikel ini, beberapa teknik differential modulation yang dikembangkan dari Space Time Block Code (STBC) diujicobakan pada Orthogonal Frequency Division Multiple Access (OFDMA) dengan dua skema yang berbeda. Skema pertama menggunakan konsep sistem antena multiple-input multipleoutput (MIMO), dan skema kedua adalah skema single-input single-output (SISO). Hasil pengujian yang diperoleh, teknik differential modulation dengan skema yang ditawarkan pada artikel ini mampu memberikan kinerja yang lebih baik daripada teknik differential modulation yang konvensional. Hasil riset menunjukkan konsep transmisi tidak koheren dapat menjadi solusi potensial untuk sistem komunikasi nirkabel berkecepatan tinggi.Kata kunci: transmisi tidak koheren, differential modulation, mobilitas tinggi, OFDMA, STBC ABSTRACTDifferential modulation is a modulation technique that can be used without the presence of channel estimation in the receiver. This technique is usually implemented when the channel condition changes rapidly, for example, when the user is in a high mobility condition. In this paper, several differential modulation techniques, which are modified from space-time block code (STBC) are tested for Orthogonal Frequency Division Multiple Access (OFDMA) using two different schemes. The first scheme uses multiple-input multiple-output (MIMO) antenna system, while the second scheme use single-input single-output (SISO). Based on our results, the differential modulation techniques proposed in this paper can overcome the conventional differential modulation technique. This research shows the proposed non-coherent transmission could be a potential scheme for high mobility wireless communications.Keywords: non-coherent transmission, differential modulation, high mobility, OFDMA, STBC.

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