With the influx of new technologies and applications requiring higher data rates and better service coverage, bandwidth and antenna array expansion are key to fast and reliable communication from high density 5G networks. The attendant infrastructure scaling, however, must be managed to minimize the growth of energy consumption as the number of data packets expands.
An integral part of the base station radio, transceivers up-convert and transfer the physical layer signal from the baseband signal processor to the RF or mmWave power amplifiers (PAs) and antennas. They also down-convert from the RF or mmWave analog signal and transfer it back to the baseband processor. With frequencies and bandwidth increasing, up- and down-conversion face challenges to ensure signal quality while minimizing power consumption. Analog circuits do not follow Moore’s law, they are not modular, and every circuit must be customized to meet unique requirements. To meet the tighter 5G New Radio (NR) specifications for data rates, noise and linearity, traditional analog circuit designs will consume more energy and board area.
HARDWARE INTELLIGENT CIRCUITS
Figure 1 HIC improves the performance of low-power mixed-signal ICs.
To address these 5G challenges, SiTune developed the recently announced SnowWings™, a multi-standard, scalable RF transceiver chipset using direct RF sampling, which provides significant advantages in cost and power consumption. The transceiver’s reduced power consumption is achieved using SiTune’s Hardware Intelligent Circuits (HIC™) technology, which enables the development of energy efficient radio units (RUs) and simplifies the radio access network (RAN) architecture. SnowWings provides a 70 percent reduction in power consumption compared to other devices in the market.
SiTune’s HIC is a patented design concept based on combining hardware and software to create calibration and digital correction techniques that optimize and improve the performance of custom, low-power analog circuits (see Figure 1). Rather than the traditional tradeoffs of increasing circuit area and power consumption to reduce noise and increase linearity, HIC technology builds on low-power circuit design and optimizes performance through “intelligent” modifications. This is done with enhanced mixed-signal IC design where the digital signal provides feedback, closing the loop to improve the performance of the analog circuit.
Figure 2 SnowWings transceiver block diagram, showing the interface to the RF front-end.
Based on direct RF sampling, the internal architecture of SnowWings (see Figure 2) uses high precision data converters and low noise amplifiers to ensure the received signal quality at the baseband and the transmit signal at the PA surpass the signal quality required for 5G NR. Using direct RF sampling avoids I/Q imbalance and local oscillator leakage. By disaggregating the digital baseband from the analog RF and IF, SnowWings handles the digital predistortion (DPD) for the PA, crest factor reduction and much of the critical digital signal processing operations. This capability enables flexible and scalable RU designs, where the RU can adapt to digital signal processing changes, split 7.x modifications and expansion of the antenna arrays. Also, SnowWings is flexible in choice of baseband, since it supports a standardized digital interface (JESD204B/C) for baseband IC processor or FPGA implementations, while achieving a low-power, high performance hardware design.
SnowWings supports any licensed or unlicensed band from 600 MHz to 7.2 GHz, including LTE, 5G NR and CBRS. To achieve hardware design flexibility, the innovative concept of multi-band convergence was implemented in the design, meaning a single pluggable IC can cover all sub-7 GHz bands with an additional low noise amplifier stage at the uplink and preamplifiers at the downlink. This capability supports dynamic spectrum sharing between LTE and 5G NR solutions using the non-standalone implementation.
SUPPORTING O-RAN
The 5G open RAN (O-RAN) architecture vision is about disaggregating hardware and software to promote open interfaces and interoperability. This involves virtualization of the distributed unit (DU) and central unit of the RAN to provide operators with faster network upgrades through remote software updates. Another important objective of the O-RAN concept is enabling network operators and private enterprises to select the best separate hardware components to build a network with the highest performance and lowest cost.
With the restructuring of the RAN architecture, partitioning O-RAN hardware components in such a way that hardware programmability and scalability is realized becomes particularly important. As shown in Figure 3, the transceiver architecture plays a key role in the RU, as the frequency bands, bandwidth, number of antenna arrays and other characteristics change depending on the application and usage. For example, for mMIMO, macro or small cell scenarios, the RU specifications vary widely and the functionality splits will change between the hardware RU and virtualized DU. The functional partitioning of SnowWings with its low-power enables a truly scalable RU design. Using multiple SnowWings ICs and stacking multiple programmable L1/low PHY solutions enables various mMIMO implementations without redefining the entire RU architecture. Providing mmWave and sub-7 GHz convergence in indoor and outdoor access points with a single transceiver provides flexibility.
Figure 3 O-RAN architecture.
SnowWings offers the lowest power consumption with design and architectural flexibility through patented innovations in RF, data converters, mixed-mode circuit design, digital correction techniques and algorithms for communication systems. Its 70 percent reduction in power consumption compared to other devices in the market, achieved through SiTune’s HIC technology, leads to lower cost RUs, reducing the total cost of ownership for enterprise and telecom product manufacturers and operators.
SiTune
San Jose, Calif.
www.situne-ic.com