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5G Disruptive Technologies and Architecture
Published in Ashish Bagwari, Geetam Singh Tomar, Jyotshana Bagwari, Advanced Wireless Sensing Techniques for 5G Networks, 2018
Anu Mangal, M.A. Rizvi, Shadab Pasha Khan
In massive MIMO, the number of antennas is much larger, providing directivity to the signals. More directivity leads to less interference and more spectrum efficiency. Outdoor base stations are equipped with large antenna arrays and are connected to indoor base stations via optical fiber which is again distributed among different antennas of a complete building (a unit) called a DAS. Outdoor mobile users are equipped with a limited number of antennas, but their collaboration with each other forms a virtual large antenna array. Thus, a virtual MIMO link is established consisting of BS antenna arrays and a large antenna array. Large antenna arrays communicate with both outdoor base stations and stations and distributed antenna elements of BS and are installed outside every unit (building) (Figure 1.2).
MIMO Techniques for 5G Systems
Published in Athanasios G. Kanatas, Konstantina S. Nikita, Panagiotis Mathiopoulos, New Directions in Wireless Communications Systems, 2017
Athanasios G. Kanatas, Konstantinos Maliatsos
Multiuser MIMO (MU-MIMO) schemes have been proposed as an efficient way to deal with the shortcomings of practical SU-MIMO systems. In realistic networks, SU-MIMO systems are vulnerable in propagation conditions where either the SNIR is low, or due to the limited multipath richness and/or the presence of a strong line-of-sight (LOS) component the spatial correlation among antenna elements is high, or the number of antennas used at the mobile terminal (UE) is really small. All these factors affect the achievable diversity and spatial multiplexing gains. MU-MIMO antenna combining techniques in conjunction with resource allocation protocols among users provide unique benefits. The first is the robustness with respect to multipath richness, providing the capability to achieve full multiplexing gain regardless of the rank of each individual user. Furthermore, a compact antenna spacing at the BS is possible. The second benefit is the great opportunity to use single antenna terminals and still maintain the same diversity and multiplexing gains. To achieve these gains, however, the CSI of the users should be fed back to the BS. In a practical system this implies the design of a trade-off mechanism between feedback accuracy and uplink resources consumption, otherwise the practical settings are restricted to TDD or settings with low mobility, in order to extend in time the channel stationarity conditions.
Exploring the limited feedback schemes for 3D MIMO
Published in Amir Hussain, Mirjana Ivanovic, Electronics, Communications and Networks IV, 2015
Zheng Hu, Rongke Liu, Shaoli Kang, Xin Su, Hongtian Li
The BS is equipped with 2D antenna array. The number of antennas in horizontal direction is Nh and in vertical direction is Nv.So the total number of antennas is N=Nv⋅Nh. Figure 1 depicts the configuration of 2D antenna array in the BS. dv and dh are the antenna spaces in the vertical direction and horizontal direction respectively. Each user has Nr receiving antennas.
Joint Initial Uplink Synchronization and Interference Aware Resource Allocation for D2D Communication in the MU-OFDMA System
Published in IETE Journal of Research, 2023
With the use of this parameter, the importance rate for each antenna is estimated at the 5G MIMO base station. It is expressed as follows: For each user, BS computes corresponding in each antenna. Then the optimal antenna selection problem selects an optimal antenna for that user based on the following objective function The objective function for user is expressed as the function of maximizing computed for that user. Using the above-mentioned Equation, the base station estimates the importance rate for each antenna with respect to the considered user equipment in the network.
Interference Cancellation in Wireless Communications: Past, Present, and Future
Published in IETE Journal of Education, 2022
S. M. Zafaruddin, Pranay Bhardwaj
We illustrate the interference cancelation in massive MIMO considering uplink transmissions for two users. As shown in Figure 3, two users transmit and signals to a BS with M antennas. The received signal vector (of size ) at the BS is where is the channel vector between user 1 and M BS antenna, and is the channel vector between user 2 and M BS antenna. Here, denotes the channel gain between i-th single-antenna user and the j-th antenna at the BS. We denote by the vector of additive white Gaussian noise (AWGN). We can represent (5) in the matrix form: where with denotes the AWGN of the receiver equipped with i-th BS antenna.
Flexible Beamforming in 5G Wireless for Internet of Things
Published in IETE Technical Review, 2019
Mukesh Kumar Maheshwari, Mamta Agiwal, Navrati Saxena, Abhishek Roy
We use MATLAB-based system simulations to validate our FBF architecture. The simulation parameters are given in Table 1. The mmWave channel values and link budget parameters as considered in recent research work [19,32–34] are used. We place BSs using stochastic geometry-based PPP. Since 5G deployment is expected to be site-specific and random [3], PPP approach enables an effective analysis as the layout is closer to the actual deployments [35]. BSs are placed in an area of 1000 × 1000 m2 with mean value (ρ) equal to 10 and 30 for FBF and multi-site, respectively. A 360 ° coverage is secured by placing antennas in sectors. We consider antenna arrays with five beams at each BS. Random waypoint mobility model, with 100 users moving at the speed of 2–20 m/s, is considered for the analysis.