With smartphones and tablets, mobile wireless has revolutionized the way people work ...
Wide area wireless connectivity allows access to Internet servers from anywhere, and the next step is to spread the power of wireless communications to machine type communications (MTCs), which will be used across manufacturing, city management, transportation and energy services Set off a revolution.
Sensors along the way convey traffic flow information to incoming vehicles and allow them to move freely. The same data can inform the customer of the expected arrival time of goods. Other nearby sensors track moisture and air pollution to ensure that the air is fresh and healthy And allow plants to get enough water and nutrients.All of these sensors will use wireless communication technology to stay in touch with the cloud sensor and they will also use other wireless services such as the Global Navigation Satellite System (GNSS) network to track their location .
Location identification is crucial not only for motion sensors, such as those mounted on transport trucks, but also for environmental sensors that are fixed in their life cycle.Location identification can reduce sensor deployment costs and allow them to accurately report where they are Position without operator intervention, and signal after inadvertent or intentional action.
Necessity of LPWAN
Widely distributed sensor and IoT nodes are necessary to support LPWAN applications.Many existing IoT applications are based on short-range protocols such as 6Lowpan, Bluetooth and Zigbee, which are affected by hundreds of The limited range of meters is not enough to support a new generation of large-scale MTC systems.
Protocols designed for LPWAN applications provide communication capabilities that can cover nodes between one kilometer or the nearest neighbor and nodes to expand the distance. This communication range drastically reduces deployment costs, including environmental sensors required by agriculture And other devices to monitor IoT nodes in highways, railways and rivers, as well as smart meters for homes In addition, LPWAN's typical frequencies go directly to equipment buried in the ground or in the basement without the need for additional expensive gateways .
There are many options for building an MTC, including access to the unlicensed and licensed bands. LoRA labeling works in an unlicensed band with a high data rate of 12.5kbit / s. The unlicensed band appears to provide lower operating costs, but in practice In operation, users still need to deploy their own gateway or rent equipment provided by third parties.Relying on the unlicensed band can also lead to higher risk, interference from other users in the same band.In addition, LoRA technology licensing will be Limiting the number of chip suppliers prevents integration into custom low-cost single-chip IoT controllers.
Cellular communications add options
On the other hand, cellular communications, due to the use of licensed frequency bands, prevent much interference and provide more overall flexibility and freedom to chip integrators. The 3GPP Standards Organization defines a series of IoT-ready protocols, most recently defined as narrow IoT (NB-IoT) .It can support penetration of underground signals, which is similar to the enhanced coverage form of GSM NB-IoT to the data rate from 10kbit / s to 50kbit / s, enhanced functionality can not only improve system performance , But also save energy.
For example, in the NB-IoT standard Release 14, the 3GPP committee experts found that maintaining relatively high throughput during transmission is more than limiting the bit rate A better approach, which allows IoT nodes to finish their transmissions faster and get into power-save hibernation mode, consumes less power during transmission - it is mainly done by the power amplifier (PA) Vendors are committed to deploying Release 14 as soon as possible to ensure that devices that are now under development support the real-world network.
NB-IoT architecture
To be able to support NB-IoT, an efficient computing architecture is required to handle the signal processing, modem protocol stacks and sensor applications required to achieve high peak data rates on a proprietary processor If these three tasks can be done on the same processor subsystem, silicon costs and power consumption are saved compared to dual-core processor builds. For example, CEVA analyzed the cellular IoT standard and found that it is strictly Of the power budget, the use of dedicated instructions to deal with high data throughput pipeline than plug-in hardware accelerator better overall performance.
The CEVA-X1 processor combines NB-IoT Dedicated Instruction with Very Long Instruction Word (VLIW) and Single Instruction Multiple Data (SIMD) architectures to effectively support LPWAN-compatible IoT nodes.The processor uses up to 10 stages of pipelining The design supports DSP-intensive code and adds many enhanced design support Jump-branch-intensive code not only for NB-IoT protocol but also for embedded control This design ensures that a processor can support NB-IoT All requirements, without the need to add additional coprocessors.
If the processor is running at 150MHz when the chip is set up, half of the processor's performance can run the application while the DSP core is transmitting or receiving data on the NB-IoT channel.
Complete NB-IoT platform
Further, CEVA's Dragonfly NB platform includes software support from the CEVA-X1 processor and partner ASTRI, along with a weekly device for energy-efficient IoT nodes, as many LPWAN-compliant IoT node applications need to be identified Position and RF transceivers that support both cellular mobile and GNSS signals. This low-IF architecture accomplishes RF to baseband data conversion to integrate and directly interface with a digital front-end unit (DFE). The transceiver provides an on-chip digital oscillation So there is no need to use the more expensive off-chip voltage control temperature compensation device.
The DFE provides sub-sampling filters to keep the base station and data in and out of the processor's memory space synchronized, minimizing software intervention and further saving energy.
In addition, a complete software stack provides end-to-end support for NB-IoT and GNSS to manage data communications and user application tasks through the RTOS operating system. With this platform designed for a new generation of large-scale MTC systems, Hope to support the rapid development of Internet of Things applications.