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Introduction to MIMO Systems
Published in Brijesh Kumbhani, Rakhesh Singh Kshetrimayum, MIMO Wireless Communications over Generalized Fading Channels, 2017
Brijesh Kumbhani, Rakhesh Singh Kshetrimayum
At this point, readers may feel that BER performance can be improved using more and more number of branches at the receiver and this takes care of the degradation in the BER due to higher order modulation techniques. However, if we observe Figure 1.4 carefully, the improvement in the BER for each additional branch keeps on reducing as we go on increasing the number of branches at the receiver. Again, number of branches at receiver cannot be increased indefinitely. So, even after using diversity techniques, it is not possible to deal with the requirement of the spectral efficiency. This opened the doors for using multiple antennas at the transmitter so that information can be transmitted simultaneously. Multiple antennas at the transmitter transmitting parallel data streams using the same channel. This enhances the data transmission rate of the channel and hence improves the spectral efficiency. Such communication systems using multiple antennas both at transmitter and receiver are known as MIMO systems [43, 93, 131]. MIMO systems get benefit from the scattering environment. In fact, scattering environment is the requirement for MIMO systems to function well. The requirement of rich scattering is explained in detail in the next section. Further in this chapter, we will discuss various aspects of MIMO systems and their variants.
Modulation Methods
Published in Jerry D. Gibson, The Communications Handbook, 2018
To achieve high spectral efficiency, modulation schemes must be selected that have a high bandwidth efficiency as measured in units of bits per second per Hertz of bandwidth. Many wireless communication systems, such as cellular telephones, operate on the principle of frequency reuse, where the carrier frequencies are reused at geographically separated locations. The link quality in these systems is limited by cochannel interference. Hence, modulation schemes must be identified that are both bandwidth efficient and capable of tolerating high levels of cochannel interference. More specifically, digital modulation techniques are chosen for wireless systems that satisfy the following properties.
Sparse Code Multiple Access (SCMA) for Cognitive Radio
Published in Rajeshree Raut, Ranjit Sawant, Shriraghavan Madbushi, Cognitive Radio, 2020
Rajeshree Raut, Ranjit Sawant, Shriraghavan Madbushi
The 5G wireless communication involves diverse applications, which will be deployed by 2020. The most important requirement of 5G is its high spectral efficiency. Apart from that, high throughput, better service, quality, low control signaling, and lower latency are some of the requirements to be met while using any access. In a cellular system, the channel bandwidth is limited, whereas it has to accommodate maximum users in it; thus, multiple access is a technique that helps the cellular communication to be more economical by maximum utilization of channel bandwidth as a physical layer technology. It enables the wireless base stations to identify various users and serve them.
An efficient SLM technique based on chaotic biogeography-based optimization algorithm for PAPR reduction in GFDM waveform
Published in Automatika, 2023
S. Selvin Pradeep Kumar, C. Agees Kumar, R. Jemila Rose
Spectral efficiency, measured in bits per second per Hz, is a valuable technique for performance analysis. Sum rate is a term used to describe spectral efficiency. The spectral efficiency of the stated PAPR reduction strategies is simulated using the parameters from Figure 7. Only Rayleigh fading is assumed in this simulation, not an AWGN channel. Less than 24fk BW is used by GFDM. Around edge subsymbol carriers have zero values due to the frequency domain RC filter. This suggests that GFDM’s effective BW is less than 2M. It uses 24 subsymbol carriers with 4fM, especially in GFDM. The difference between subsymbol carriers has been extended to 4fk, and the frequency of the GFDM SLM has been widely dispersed. Spectral efficiency in wireless communications speeds is affected by the number of users accessing the network concurrently. In this scenario, the data transfer rate depends on the transmission device’s bandwidth and the transmitted signal or the signal-to-noise power ratio. When the signal-to-noise ratio is improved, it also boosts spectral efficiency and channel capacity. To put it simply, more data must be sent over the available spectrum to use it efficiently.
A Brief Review on mm-Wave Antennas for 5G and Beyond Applications
Published in IETE Technical Review, 2023
Paikhomba Loktongbam, Debasish Pal, A. K. Bandyopadhyay, Chaitali Koley
Spectral efficiency enhancement is one of the major goals for 5G communication system. Efficiency enhancement can be implemented using a cognitive radio network. An unlicensed band can work together with a licensed band in interference-free mode or tolerable interference mode to enhance efficiency [191]. Operation in this mode needs strict spectrum monitoring, also known as spectrum sensing. Spectrum resources can be further improved by implementing densely deployed small cells. This architecture will enhance the data rate and the capacity of the mm-wave network, but the drawback of this system is spectral leakage and interference. These drawbacks can be avoided using suitable technique involving subcarrier frequencies [191].
Fractional sequential likelihood ascent search detector for interference cancelation in massive MIMO systems in 5G technology
Published in International Journal of Electronics, 2021
Anju V. Kulkarni, Radhika Menon, Pramodkumar H. Kulkarni
This section illustrates the interference mitigation technique in massive-MIMO systems using 5 G technology. Usually, 5 G technologies are employed as a solution for applications that involve high data rates. The conventional method undergoes the standardisation of 5 G network development. The goal of 5 G standardisation activities aims to fulfil the demands of each new application of MIMO systems. The communication between the transmitter and receiver augments spectral efficiency but poses challenges like interference. For eradicating the interference in massive-MIMO systems, the newly designed technique, namely Fractional–SLAS is employed. At first, the signals are transmitted through the transmitter by employing successive steps for encoding and modulating the input signals. The modulated signals are fetched using the transmitting antenna that helps to transmit the signals and the receiver receives the signals at the receiver side, which is then followed with demodulation and decoding of the signals. Thus, the interference in the signals is eradicated by applying the proposed Fractional-SLAS at the receiver end, which is the modification of the existing Sequential Likelihood Ascent Search Detector (SLAS) (Maciel et al., 2018) using the fractional calculus (Bhaladhare & Jinwala, 2014). The advantages of using the interference mitigation method using the proposed Fractional-SLAS are that the interference is completely eradicated from the signals without any delay or loss in the quality of the transmitted signal. Thus, the proposed interference mitigation techniques contain manipulation of the transmissions to avoid interactions between transmitter and receiver.