Section 3 MIMO and 5G

Chapter 4

Abstract

1. Introduction

47

Coherent Receiver for Turbo

K. Vasudevan, Shivani Singh and A. Phani Kumar Reddy

Single-user massive multiple-input multiple-output (MIMO) systems have a large number of antennas at the transmitter and receiver. This results in a large overall throughput (bit-rate), of the order of tens of gigabits per second, which is the main objective of the recent fifth-generation (5G) wireless standard. It is feasible to have a large number of antennas in mm-wave frequencies, due to the small size of the antennas. This chapter deals with the coherent detection of orthogonal frequency division multiplexed (OFDM) signals transmitted through frequencyselective Rayleigh fading MIMO wireless channels. Low complexity, discrete-time algorithms are developed for channel estimation, carrier and timing synchronization, and finally turbo decoding of the data at the receiver. Computer simulation

Keywords: 5G, channel capacity, channel estimation, single-user massive MIMO, OFDM, spatial multiplexing, retransmissions, synchronization, turbo codes

The main objective of the fifth-generation [1–15] wireless communication standard is to provide peak data rates of 10 gigabit per second (Gbps) for each user, ultralow latency (the time duration between transmission of information and getting a response) of less than 1 ms, and, last but not the least, very low bit error rates (BER) ( < 1010). High data rates are essential for streaming ultrahigh definition (4k) video. Low latency is required for future driverless cars and remote surgeries. An important feature of the 5G network is that it involves not only people but also smart devices. For example, it may be possible to control a microwave oven or geyser located in the home, from the office. High data rates are feasible by using a large number of transmitting antennas. For example, if each transmit antenna transmits at a rate of 100 megabits per second (Mbps), then using 100 transmit antennas would result in an overall bit-rate of 10 Gbps. This technique of increasing the overall bit-rate by using a large number of transmit antennas is also known as spatial multiplexing (not to be confused with spatial modulation [16–20], wherein not all the transmit antennas

th transmit

are simultaneously active). This is illustrated in Figure 1, where the i

antenna sends Ci bits of information and each of the receive antennas gets C=N bits

Coded Single-User Massive

MIMO-OFDM with

Retransmissions

results are presented to validate the theory.

## Chapter 4
