Solution for 5G VoNR+ in IoT Communication Field

Analog Front End (AFE), also known as Radio Frequency Front End (RFFE), is designed by integrating high-speed amplifiers, receiver analog-to-digital converters (ADCs), transmit digital-to-analog converters (DACs), and continuously shrinking high-frequency filters. AFE solutions are used in 5G base stations and mobile phones.

Analog Front End (AFE)

Specifically, in 5G designs, AFE is needed to support multiple transmission and reception paths in the multiple-input multiple-output (MIMO) configuration. Therefore, it is not surprising that the increasing complexity of 5G limits the number of manufacturers with expertise in developing such complex RF subsystems. However, at the same time, as 5G designs mature, more and more suppliers are stepping up to address the AFE challenges.

This is because RF design represents a huge opportunity in 5G networks, which will deploy a large number of base stations in macro, micro, pico, and femto cellular devices to facilitate proper user coverage. 5G networks also require higher integration and miniaturization compared to 2G, 3G, and 4G to reduce power consumption and costs.

One key aspect of 5G technology is its ability to support applications in the Internet of Things (IoT) and Industrial Internet of Things (IIoT). AFE is at the core of this bandwidth innovation. The increased AFE bandwidth in 5G networks no longer serves only smartphones like previous cellular networks but can even be used for internet services on laptops and desktop computers.

The AFE design challenges in 5G aim to support higher data rates and large traffic volume. In addition to that, the significant growth in connected devices caters to highly diverse use cases and requirements. To meet the tremendous increase in wireless data traffic capacity, spectrum efficiency and reuse, higher speeds, and lower latency are the primary considerations in AFE design. While below the 6 GHz spectrum is crowded with various wireless applications, the spectrum above 6 GHz, especially in the millimeter-wave (mmWave) frequency range, is of great interest due to its wide available bandwidth. To support transmission in the most challenging outdoor areas of the mmWave frequency range, AFE's task is to improve high path loss, oxygen and H2O absorption, losses through foliage, and fading caused by rain.

Beamforming and beam tracking are the two most critical techniques used in AFE design to overcome all these adverse channel characteristics in millimeter-wave frequencies, extend transmission distances, and enhance service coverage. Speed is another key factor in AFE design. The operating speed of the 5G AFE architecture is higher than that of previous 2G, 3G, or 4G systems. The current 5G system is ten times faster than 4G LTE. The maximum speed of 5G is 10 Gbps with the potential to reach 20 Gbps, while 4G LTE operates at 1 Gbps, 3G at 42 Mbps, and 2G at 0.3 Mbps. Latency in 5G's radio front-end architecture has new elements that provide faster access speeds and low latency.

The latency of 5G AFE is significantly more important than that of previous 3G and 4G versions. The minimum latency of 5G is 1 millisecond or shorter. In contrast, the latency of 4G systems ranges from 50 milliseconds to 98 milliseconds, 3G systems have a latency of 212 milliseconds, and 2G systems go as high as 629 milliseconds. That is why the new 5G services now utilize the ultra-reliable low-latency communication (uRLLC) feature, which is especially needed in critical applications such as autonomous driving, robot control, factory automation, and vehicle-to-everything (V2X) communication.

Radio Frequency Front End (RFFE)

RF chip manufacturers have embraced the 5G design challenge with new AFE/RFFE solutions. The data converters in these AFE/RFFE support the channel bandwidth available in the millimeter-wave frequency range, opening the door to the commoditization of RF architecture by bringing the digital/analog divide closer to the antenna, potentially reducing the complexity of RF circuits.

The functional block diagram of AFE7988/89 highlights the new level of RF integration in 5G designs. Source: Texas Instruments. Next is the AD9081 and ADR554x RF front-ends introduced by Analog Devices Inc. for massive MIMO (M-MIMO) radios.

These AFEs significantly increase the number of transceiver channels operating simultaneously in multiple frequency bands while compressing all the necessary hardware into a smaller form factor.

The integrated dual-channel architecture allows RF designers to quickly scale their MIMO capacity to meet the bandwidth requirements of 5G. Source: Analog Devices Inc. Clearly, 5G transceivers must leverage integration advantages to reduce power consumption and costs due to the large number of antennas and frequency bands that need to be supported, as well as the significant number of devices required to achieve sufficient coverage.

The 5G AFE has four TX/RX paths with observation channels. Source: Xilinx. The RF sampling in 5G AFE/RFFE is getting closer to the antenna, simplifying and shrinking the radio form factor while achieving higher levels of integration. This, in turn, makes direct RF sampling in 5G base station and smartphone designs a reality. Therefore, as 5G designs continue to shrink, advanced packaging and integrated AFE/RFFE modularization are becoming increasingly feasible. Furthermore, with the advent of 6G terahertz frequencies, we will soon see even smaller AFE form factors.