5G mobile connections will grow from 5 million in 2019 to nearly 600 million in 2023

By 2021, it is estimated that more people worldwide will have mobile phones (5.5 billion), which will exceed the number of people using tap water (5.3 billion). At the same time, video applications with tight bandwidth will further increase the demand for mobile networks, which will account for 78% of mobile traffic. 5G networks using massive multiple-input multiple-output (MIMO) technology will be the key to supporting this growth. According to Strategy Analytics, 5G mobile connections are expected to grow from 5 million in 2019 to nearly 600 million in 2023.

MIMO technology

As shown in Figure 1, a single-user MIMO system is used for 3G, while 4G uses a multi-user MIMO system technology.

figure 1

Each generation of wireless technology uses advances in antenna technology to help increase network speeds. 3G uses single-user MIMO, which uses multiple simultaneous data streams to transmit data from a base station to a single user. Multi-user MIMO is the dominant technology in 4G systems. It allocates different data streams to different users and has significant capacity and performance advantages compared with 3G (Figure 1). 5G will introduce massive MIMO to further increase capacity and provide data rates up to 20 Gb/s (Figure 2).

Figure 2: The evolution of MIMO will eventually lead to massive MIMO for 5G.

5G massive MIMO

The slogan of 5G is to increase network capacity and data rate while minimizing operator costs. Users also increasingly hope that wireless data services can provide wired quality.

5G massive MIMO will help operators achieve these goals. It will provide high data rates for many users and help increase capacity. It will support real-time multimedia services without the need for additional spectrum. In addition, massive MIMO will reduce energy consumption by using beamforming to direct signals to individual users. Beamforming technology focuses the signals from multiple antennas into a single strong beam.

Advantages of spatial multiplexing and massive MIMO

Massive-MIMO technology uses large antenna arrays (usually consisting of 64 dual polarizations, but at least 16 array elements) to take advantage of spatial multiplexing (Figure 3). Spatial multiplexing provides multiple parallel data streams in the same resource block. By expanding the total number of virtual channels, it can increase capacity and data rate without the need for additional towers and spectrum.

Figure 3: Various benefits are related to massive MIMO, such as spatial multiplexing.

In spatial multiplexing, each spatial channel carries independent information (Figure 4). If the environment is sufficiently scattered, many independent sub-channels are created in the same allocated bandwidth, thereby achieving multiplexing gain without incurring additional bandwidth or power costs. The multiplexing gain is also called the degree of freedom of the reference signal spatial constellation; in a massive MIMO configuration, the degree of freedom controls the overall capacity of the system.

Figure 4: Each channel that is spatially multiplexed with massive MIMO carries independent information.

Through massive MIMO, multiple antennas concentrate the transmitted and received signals into a small spatial area, thereby greatly improving throughput and energy efficiency. The more data streams, the higher the data rate, and the more efficient the use of radiated power. This method also improves link reliability. The increase in antennas means that more degrees of freedom can be spent on space diversity. It improves the selectivity of sending and receiving data streams, and enhances the interference cancellation function.

The benefits of massive MIMO include:

Prevent transmission in undesired directions and reduce interference

Reduce latency, achieve faster speed and higher reliability

Reduce fading and drop, improve signal-to-noise ratio (SNR)

Improve spectrum efficiency and high reliability

Improve energy efficiency

5G massive MIMO

And Sub-6GHz deployment

Obviously, in order to achieve the 5G target of 20Gb/s data rate, it is necessary to use millimeter wave (mmWave) spectrum. However, before mmWave can be used in mobile communications, several key challenges must be resolved.

Although operators and original equipment manufacturers (OEMs) are working hard to improve mmWave technology, below 6GHz will become the near-term 5G network technology. The Sub-6GHz frequency is suitable for rural and urban areas because the technology can provide high data rates over long distances (Figure 5). Operators are initially expected to deploy 5G in the 3,300~4,200-MHz and 4,400~5,000MHz frequency ranges, which will allow up to 100MHz channel bandwidth.

Figure 5: The difference in coverage and capacity is different between 5G mmWave and 6GHz.

Sub-6GHz massive MIMO will solve the interference problem by using a large number of antennas in the base station and enable the base station to provide services to a large number of users in urban areas. Massive MIMO can also improve peak, average, and cell edge throughput, maximizing cost efficiency by providing the best balance between user coverage and capacity.

However, these technological advancements are not without system design challenges. Sub-6GHz massive MIMO beamforming technology will drive the demand for small, cost-effective power amplifiers (PA) that can be used in massive MIMO arrays. In addition, as 5G modulation schemes become more and more complex (ie, 256 QAM), wireless infrastructure power amplifiers will need to be very efficient under deep output power back-off conditions (up to 8 dB or higher). Achieve the necessary linearity.

Realize with GaN

5G Mass-MIMO Sub-6GHz

Gallium nitride (GaN) technology can play an important role in sub-6GHz 5G applications, helping to achieve goals such as higher data rates.

High output power, linearity and power consumption requirements are driving the conversion of PAs deployed by base station and network OEMs from using LDMOS technology to GaN. GaN provides multiple advantages for 5G sub-6GHz massive MIMO base station applications:

GaN performs well at frequencies of 3.5 GHz and above, while LDMOS is challenged at these high frequencies.

GaN has high breakdown voltage, high current density, high transition frequency, low on-resistance and low parasitic capacitance. These characteristics can be translated into high output power, wide bandwidth and high efficiency.

The average efficiency of GaN with Doherty PA configuration at 100 W output power reaches 50% to 60%, which significantly reduces transmission power consumption.

The high power density of GaN PA enables a small size that requires less printed circuit board (PCB) space.

The use of GaN in the Doherty PA configuration allows the use of a quad flat no-lead (QFN) plastic package instead of an expensive ceramic package.

The efficiency of GaN at high frequencies and wide bandwidth means that massive MIMO systems can be more compact. GaN can operate reliably at higher operating temperatures, which means it can use a smaller heat sink. This can achieve a more compact form factor.

Meet 6GHz

The following RFFE design goals

Building an RF front end (RFFE) to support these new sub-6GHz 5G applications will be a challenge. RFFE is critical to the power output, selectivity and power consumption of the system. The complexity and higher frequency range have driven the demand for RFFE integration, size reduction, lower power consumption, high output power, wider bandwidth, improved linearity and increased receiver sensitivity. In addition, the coupling requirements between the transceiver, RFFE and antenna are more stringent.

Some goals of 5G sub-6GHz RFFE, and how can GaN PA help achieve these goals? The details are as follows:

Higher frequency and higher bandwidth: 5G uses higher frequencies than 4G and requires wider component carrier bandwidth (up to 100 MHz). GaN-on-silicon-carbide (GaN-on-SiC) Doherty PA achieves a wider bandwidth and higher power added efficiency (PAE) than LDMOS at these frequencies. The higher efficiency, higher output impedance and lower parasitic capacitance of GaN devices allow easier broadband matching and expansion to very high output power.

High power efficiency at higher data rates: GaN has soft compression characteristics, making it easier to predistort and linearize. Therefore, it is easier to use for high-efficiency digital pre-distortion (DPD) applications. GaN can operate on multiple cellular frequency bands, helping network operators deploy carrier aggregation to increase spectrum and create larger data pipelines to increase network capacity.

Minimizing system power consumption: How do we meet the high data rate requirements of 5G? We need more infrastructure, such as data centers, servers, and small cells. This means an overall increase in network power consumption, which drives the demand for system efficiency and overall power savings, which seems difficult. Similarly, GaN can provide solutions by providing high output power and improving base station efficiency.

Figure 6 shows a block diagram of an exemplary sub-6GHz RFFE that uses Qorvo's Doherty PA design to achieve high efficiency.

Figure 6: This sub-6GHz massive MIMO RFFE includes Doherty PA.

Conclusion

5G mass-MIMO sub-6GHz infrastructure design has been launched. This means that the technology and system design required to solve higher frequency, higher power output and lower power consumption must now be provided to support the expansion of global operators. GaN can help operators and base station OEMs achieve the goals of 5G sub-6GHz and mmWave massive MIMO.