6G: Introduction First generation (1G): Mobile networks were designed for voice services with data rates of up to 2.4 kbit/s. Analog signals used to transmit information, and there was no universal wireless standard. Second generation (2G): Was based on digital modulation techniques and offered data rates of 50 Kbit/s to 384 Kbit/s, supporting not only voice services but also data services such as Short Message Service (SMS). The flagship 2G standard was the Global System for Mobile (GSM) communications. Third generation (3G): Mobile networks provided data rates of at least 2 Mbit/s and enabled advanced services including web browsing, TV streaming, and video services with data rates of up to 20 Mbit/s. To achieve global roaming, 3GPP was established to define technical specifications and mobile standards. Fourth generation (4G): Mobile networks were introduced in the late 2010s. 4G is an entirely Internet Protocol (IP) based network capable of providing high speed data rates of up to 1 Gbit/s in downlink and up to 500 Mbit/s in uplink to support advanced applications such as digital video broadcasting. DVB), high-definition TV content and video chat. LTE-Advanced (LTE-A) has been the dominant 4G standard, integrating technologies such as coordinated multipoint (CoMP) transmission and reception, multiple-input multiple-output (MIMO), and orthogonal frequency division multiplexing (OFDM). Fifth generation (5G): Is to use not only the microwave band but also the millimeter-wave (mmWave) band for the first time to significantly increase data rates to 20 Gbit/s. Another feature of 5G is the more efficient use of spectrum, as measured by increasing the number of bits per Hz. ITU's International Mobile Telecommunications 2020 (IMT 2020) standard proposed the following three major 5G usage scenarios: 1. Enhanced Mobile Broadband (eMBB), 2. Ultra-Reliable and Low Latency Communications (URLLC), 3. Massive Machine Type Communications (mMTC). As 5G is entering the commercial deployment phase, research has begun to focus on 6G mobile networks, which are estimated to be deployed by 2030 Typically, next-generation systems do not emerge out of a vacuum, but rather follow industrial and technological trends from previous generations. Potential research directions for 6G in line with these trends were provided by Bi (2019), which included, among others: Sixth generation (6G): Is envisioned to provide even faster data speeds, lower latency, greater capacity, and support for advanced technologies such as artificial intelligence, virtual reality, augmented reality, and the Internet of Things (IoT). It may also include innovations such as terahertz frequency bands, massive MIMO (multiple-input multiple-output) systems, and advanced antenna techniques to enhance network performance. ● 6G will continue to move to higher frequencies with wider system bandwidth: given that the spectrum at lower frequencies is

1. 6G: Introduction

2. First generation (1G):
Mobile networks were designed for voice services with data rates of up to 2.4
kbit/s. Analog signals used to transmit information, and there was no universal
wireless standard.
Second generation (2G):
Was based on digital modulation techniques and offered data rates of 50
Kbit/s to 384 Kbit/s, supporting not only voice services but also data services
such as Short Message Service (SMS). The flagship 2G standard was the
Global System for Mobile (GSM) communications.
Third generation (3G):
Mobile networks provided data rates of at least 2 Mbit/s and enabled
advanced services including web browsing, TV streaming, and video services
with data rates of up to 20 Mbit/s. To achieve global roaming, 3GPP was
established to define technical specifications and mobile standards.
Fourth generation (4G):
Mobile networks were introduced in the late 2010s. 4G is an entirely Internet
Protocol (IP) based network capable of providing high speed data rates of up

3. to 1 Gbit/s in downlink and up to 500 Mbit/s in uplink to support advanced
applications such as digital video broadcasting. DVB), high-definition TV
content and video chat. LTE-Advanced (LTE-A) has been the dominant 4G
standard, integrating technologies such as coordinated multipoint (CoMP)
transmission and reception, multiple-input multiple-output (MIMO), and
orthogonal frequency division multiplexing (OFDM).
Fifth generation (5G):
Is to use not only the microwave band but also the millimeter-wave (mmWave)
band for the first time to significantly increase data rates to 20 Gbit/s. Another
feature of 5G is the more efficient use of spectrum, as measured by increasing
the number of bits per Hz. ITU's International Mobile Telecommunications
2020 (IMT 2020) standard proposed the following three major 5G usage
scenarios:
1. Enhanced Mobile Broadband (eMBB),
2. Ultra-Reliable and Low Latency Communications (URLLC),
3. Massive Machine Type Communications (mMTC).
As 5G is entering the commercial deployment phase, research has begun to
focus on 6G mobile networks, which are estimated to be deployed by 2030
Typically, next-generation systems do not emerge out of a vacuum, but rather
follow industrial and technological trends from previous generations. Potential
research directions for 6G in line with these trends were provided by Bi
(2019), which included, among others:
Sixth generation (6G):
Is envisioned to provide even faster data speeds, lower latency, greater
capacity, and support for advanced technologies such as artificial intelligence,
virtual reality, augmented reality, and the Internet of Things (IoT). It may also

4. include innovations such as terahertz frequency bands, massive MIMO
(multiple-input multiple-output) systems, and advanced antenna techniques to
enhance network performance.
● 6G will continue to move to higher frequencies with wider system
bandwidth: given that the spectrum at lower frequencies is nearly exhausted,
the current trend is to increase the data rate by more than 10 times for each
generation to achieve wider bandwidth at higher frequencies Is:
● Massive MIMO will remain a key technology for 6G: Massive MIMO has
been the defining technology for 5G which has enabled the antenna count to
increase from 2 to 64. Given that performance gains have saturated in the
areas of the channel coder and modulator, spectral efficiency increases for 6G
in the multiple antenna area will continue to be expected. MIMO Interview
Questions Answers.
● 6G will take cloud service to the next level: With consistently higher data
rates, lower latency, and lower transmission costs, many computational and
storage functions have been moved from smartphones to the cloud. As a
result, most of a smartphone's computational power can be focused on
presentation rendering, making VR, AR or XR more efficient and affordable.
Many Artificial Intelligence (AI) services that are intrinsically cloud based can
be more easily and widely proliferated. In addition to smartphones, low-cost
functional terminals may once again flourish, providing opportunities for
development in more application areas.
● Grant-free broadcasts may become more prominent in 6G: In previous
cellular network generations, broadcasts were primarily based on
grant-oriented designs with strong centralized system control. 6G will require
more advanced grant-free protocols and approaches. It is possible that
non-orthogonal multiple access (NOMA) technology may have another
chance to prevail due to its low-latency performance, even if it fails to take off
during the 5G time period.
● MMTC is more likely to take shape in the older generation before
succeeding in the next generation: MMTC has been one of the major

5. directions for next-generation system design since the growth of the
people-to-people communication market. High hopes are pinned on 5G
MMTC to deliver significant growth for the cellular industry. However, so far,
this expectation has been mismatched with reality.
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