Narrowband IoT Expansion Address Low-Power Requirements |Synopsys

Introduction

As the world continues to recover from a global pandemic, connectivity plays a crucial role in today’s technological recovery and ongoing evolution. The need for connected remote devices in the field continue to increase and now it’s become an absolute necessity to be able to sense the information, process it and communicate that information in a reliable, and efficient way. In the past, the main challenge for our ‘connected world’ was the ability to operate in remote locations with security capabilities and minimal power consumption. 

While the big networks and marketing firms have been emphasizing recent 4G/5G adoptions where the high speed/high throughput features prevail, those types of technologies are typically costly to implementation and target power-hungry end-products, making it impractical for deployment on a worldwide scale across all types of applications that don’t necessarily require the mentioned high throughputs and data rates but would still require a level of connectivity and reliability while also being able to address low-cost, low-power consumption and low-complexity requirements for products that can be deployed in massive numbers.  

To address those type of applications while still being able to benefit from legacy standards the 3GPP defined the Narrowband Internet of Things (NB-IoT) radio interface  to provide IoT services though wide-area cellular networks with a set of releases that put emphasis around simplicity in order to reduce costs and address the need of low power implementations to minimize battery consumption while still being adapted to work in difficult radio conditions, especially in locations that can’t easily be covered by conventional cellular technologies. 

In addition, due to the anticipated IoT market growth in terms of connected devices and applications, several efforts have been made to meet the connectivity needs. In recent years, many standards and communication protocols have been developed to support a wide range of applications for machine-to-machine communication, also known as machine-type communication (MTC). These standards and protocols were mostly dedicated to short-range applications and for well-defined usage, i.e. Bluetooth or Wi-Fi enabled devices, but in the last couple of years, long-range connectivity protocols such as Narrowband IoT have been developed and used for MTC in long-range applications, which has enabled the ability to support a broad range of applications and industries.


Massive IoT Connections by Numbers and Trends

Figure 1: Cellular IoT Connections by Segment and Technology (Billion)

According to Ericsson’s Mobility Report, the number of IoT devices connected by NB-IoT and LTE-M technologies is expected to overtake 2G/3G connected IoT devices in the near future and overtake broadband IoT in 2027 with more than 51% of all cellular IoT connections by that time (Figure 1). 

Bundling the NB-IoT protocol as part of the standard mobile 3GPP rollouts has served to accelerate adoption as many mobile network operators (MNOs) make modifications to their existing infrastructure to support features of the new releases. Furthermore, the growth of these massive IoT communications technologies, such as NB-IoT, has been recently enhanced by an added network capability that has enabled a co-existence between 4G/5G along with NB-IoT technologies in FDD bands via spectrum sharing. With these rollouts and enablement of massive IoT technologies into the existing cellular networks, the expectation for the global NB-IoT chipset market is expected to reach a $22.10 billion by 2030 with a CAGR estimate of 52.1% from the years 2021 to 2030.

From the infrastructure perspective, as shown in Figure 2, the global deployment of massive IoT technologies (both NB-IoT and LTE-M) has been primarily led by MNOs in the US and Europe. Asia and Eastern Europe are largely deploying NB-IoT alone (Cat-NB1, Cat-NB2). Overall, more than 124 service provides have commercially launched NB-IoT networks while 55 have launched Cat-M technologies, and around 40 services providers have launched both technologies.

Figure 2: Massive IoT Communications Deployment

Extending IoT Cellular Applications into New Territories

Having the support of MNOs, chipset and module manufacturers, and with the ability to co-exist with 2G, 3G, 4G and even 5G mobile networks, massive IoT communications (specifically the NB-IoT) enable a broad range of applications and services proposed to individuals and industries.  

The inherent capabilities of the NB-IoT systems allow them to be a great fit for the type of applications that do not require high data rates, but instead demand low-power consumption, low-cost devices that can be deployed in massive numbers in a range of sectors and applications, such as:

  • Consumer
    • Smart home
    • Smart appliances
    • Smart padlocks
    • Wearables
  • Smart Cities
    • Smart parking
    • Smart meters
  • Smart Agriculture
    • Soil moisture monitor
    • Air quality monitor
  • Smart Industry 
    • Fleet and asset management
    • Smart pallets
    • Monitoring and asset tracking
  • Enterprise
    • Smart access
    • Waste management and storage containers
    • On/Off buttons

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An Integrated NB-IoT Subsystem Solution

Since NB-IoT is the evolution of an already existing LTE technology, module manufacturers have looked at existing LTE-based modules and are trying to apply them to NB-IoT modules. This approach seems to be overkill due to the key drivers seen in the NB-IoT systems as well as the type of applications in which these modules would be deployed where the needs for low-cost devices, low-power consumption and simplicity are predominant factors. In addition, we see that typical applications do not need continuous data transfer between the user equipment (UE) and a baseband. Instead, the NB-IoT-based UE collects data from different sensors, processes it and transmits the processed results based on a specific event or timer. 

A single small and efficient CPU/DSP processor, complemented with a few well-targeted hardware accelerators addressing one of the main requirements for low-cost devices (mainly determined by the silicon area) as well as the need for low-power consumption for battery-operated systems is the ideal basis for a flexible and modern NB-IoT modem 

The Synopsys DSP-enhanced ARC® EMxD processors are extremely well-suited for building NB-IoT modems. Their highly efficient 3-stage pipeline, combined with DSP instructions added into the instruction set architecture (ISA), allows the to execute both control and DSP codes, eliminating the needs for separate RISC and DSP processors for executing the control application and the NB-IoT protocol stack. 

The ARC EM11D processor provides XY memory with an advanced address generation unit for the efficient implementation of NB-IoT. This architecture provides up to three logical memories that the processor can access concurrently, allowing many NB-IoT modem functions to execute efficiently on the processor without additional hardware accelerators.  

The Synopsys ARC EM processors also provide the ability to extend the processor with custom instructions, using ARC Processor EXtension (APEX) technology, that can significantly accelerate the execution of certain functions.  Synopsys offers the integrated ARC IoT Communications Subsystem, which leverages the ARC EM11D processor and APEX instructions to ease development of an NB-IoT modem. This APEX technology enables the efficient implementation of a Viterbi decoder and trigonometric functions, which are prominent steps to be considered in the NB-IoT protocol stack for performing forward error correction in the receiver (Figure 3). 

In addition to these features, the ARC IoT Communications Subsystem also offers integrated peripherals to provide a wide range of SoC connectivity, a Digital Front End (DFE) for seamless integration to standard NB-IoT RF transceivers and an efficient power management unit, which will be explored in the next section. 

Figure 3: Synopsys DesignWare IoT Communications IP Subsystem

Addressing the Low-Power Challenges of NB-IoT Systems

As stated earlier, low-power consumption is a key requirement and challenge in the development of an NB-IoT modem that needs a combination of an efficient low-power processor/DSP and a mechanism that allows for clock switching and all I/O functions and the processor itself to be switched off independently. The ARC IoT Communication Subsystem’s integrated power management unit (PMU) and clock control unit (CCU) provide critical support for devices to meet stringent battery lifetime requirements set forth by the 3GPP. Many of these battery-operated systems are intended for “set-and-forget” applications where human interaction and the access to the device itself can be limited. The 3GPP standard defines several use cases based on frequency of communication (every 2 hours / once daily) and data bandwidth (50 bytes / 200 bytes). The expectation with a 5Wh battery is 10 years of battery lifetime for all use case combinations. 

To help SoC designers meet these goals, the subsystem provides several programmable power domains within the ARC EM11D processor as well as within the rest of the IoT Communications Subsystem logic. Aside from the always-on logic (AON), which is needed for data retention, clocking, power management, etc., the remaining domains can be controlled as needed to meet power requirements, which allows the ARC IoT Communications Subsystem to consume less than 1uW in standby power domains, ensuring more than 10 years of battery life in the end device. The subsystem power domains are shown in Figure 5. 

Figure 4: IoT Communications Subsystem Power Domains

Use cases for power management can be seen in Table 1 highlighting recommend states for the ARC EM11D processor, RF transceiver, and subsystem logic to minimize power consumption in active, sleep (memory retention, RF idle), and standby modes (RF powered OFF, only AON logic active).

 

Table 1: IoT Communications Subsystem Power Modes & Power Domains

Providing an Integrated Solution with Software Enablement

On the software front, in addition to an efficient implementation of the software stack, the processor needs to have excellent code density to allow for small memories and to avoid the need for DRAM, which will bring the systems costs down even further. The ARC IoT Communications Subsystem provides precisely that with a combination of a code density efficient processor, a base communications library and an optimized NB-IoT Layer 1 software licensable option with 3GPP Release 14 compliant software stack optimized for low memory.

The base communication software library supports all the base NB-IoT functions such as interpolation, FFTS, and modulation as well as all the low-level drivers for the DFE, host IF, USIM and UART interfaces. On the other hand, the NB-IoT Layer 1 (PHY) licensable option provides all the native low-level L1 API enabling integration with multiple protocol stacks (L2/L3) and multiple Radio Front Ends (RFEs) (Figure 5). As part of the documentation, an integration guide as well as application examples (i.e. NB-IoT synchronization, data channel handling) are provided to facilitate ease of use and allow an easy implementation.   

Figure 5: NB-IoT Communications Layer 1 Software

Summary

Support for low-cost, low-power wide-area communications is increasingly important for embedded IoT devices addressing a broad range of emerging smart applications. NB-IoT systems trending to become one of the key products to be implemented in the field, leveraging their low-power consumption capabilities, simplicity, cost-efficiency as well as the long-range, combined with ease of use, 2G/3G rollover and 4G/5G support. Because of this it is fair to predict that this protocol and the systems implementing it will become pervasive in different kinds of applications such as metering, industrial field, parking, wearables, agriculture devices and industrial production lines. Leveraging a pre-verified, integrated hardware and software solution that has been tested with key partners reduces risk and makes the job easier for the companies that implement it into their own SoCs. 

Synopsys’ ARC IoT Communications IP Subsystem provides a complete IoT solution to address a wide range of applications and meet stringent design requirements while enabling ease of use and faster time to market. 

For more information, visit the web page at: https://www.synopsys.com/dw/ipdir.php?ds=iot-comms-subsystem 


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