Survey of microcontrollers and
short-range radio transceivers for wireless
sensors
Bachelor Thesis
Ephrem Zewdu
MID SWEDEN UNIVERSITY
Department of Information Technology and Media (ITM)
Examiner: Lundgren jan, Jan.Lundgren@miun.se Supervisor: Bengt Oelman, Bengt.Oelmann@miun.se Author: Ephrem Zewdu, epye1000@student.miun.se
Degree programme: international Bachelor’s Program in Electronics, 180.0 credits Main field of study: Electronics design
Abstract
A significant growth was witnessed in the field of Wireless Sensor Networks (WSNs), in the previous decade. The objective of this study has been Survey of micro controllers and short-range radio transceivers for wireless sensors and provide an extensive overview of micro control-lers and RF-transceivers in the Market and compare the relevant proper-ties for designing wireless sensor nodes. In the survey, RF-transvers from Nordic semiconductors is extensively presented for short-rang wireless protocols some of the protocols are RF-Communication Mod-ule, Bluetooth Low Energy ModMod-ule, ZigBee module and Wi-Fi module. In WSNs node design Power consumption is one the most important design issue, this thesis work present the different type of WSN proto-cols energy consumption efficiency and power consumption, compared and conclude graphically.
Microcontrollers are the main part of WSNs node for processing and gathering sensor data. There is different microcontroller’s products in the market however the WSN protocols presented in this thesis uses Cortex-M4 processor which is one of ARM product, the specification and comparison of this product with other products is presented.
Keywords: Wireless Sensor Network (WSNs), RF-transceivers, wireless
Acknowledgements
First of all, I would like to express my sincere gratitude to my advisers Prof.Bengt Oelmann and Prof.Börje Norlin for letting me conduct this thesis under their supervision.
Many Thanks to a friend Xu Ye who have shared his knowledge and time to lend a helpful insight and feedback in this Thesis work.
I also would like to use this opportunity to extend my gratefulness to my family, Friends and all who has been at my side during this thesis work and the course of my study. All your words and supports have strengthened me in many ways.
Table of Content
Abstract ... iii Acknowledgements / Foreword ... iv Terminology / ... vi Mathematical Notation ………...viii 1 Introduction (Introduktion) ... 1 1.1 System Requirment... 1 1.2 Challenges of WSN……….2Error! Bookmark not defined. 1.3 Application of WSN ... 21.4 Architecture of WSN ... 3
2 Theory / RF Communication ... 4
2.1 BLE (Bluetooth Low Energy Comunication Modules . 8Error! Bookmark not defined. 2.1.1 ZigBee Communication ... 9
2.2 Wi-Fi Communication ... Error! Bookmark not defined. 2.3 Power Consuption ... 23 2.4 MICROCONTROLLER………24 2.5 OPERATING SYSTEMS………...26 3 Methodology ………..28 4 Rusult……….29 5 Conclusion………..35 5.1 Future work………36 References ………..37
Terminology
Acronyms
WSN Wireless sensor Network.
WPAN Wireless personal area network
WLAN Wireless local-area network.
GID Global identification GPS Global Positioning System RF Radio Frequency
RX Receive TX Transmit
ISM Industrial, Scientific, & Medical ACK Acknowledgemen
GFSK Gaussian frequency shift keying BPSK Binary phase-shift keying
ASK Amplitude Shift Keying
QPSK Quadrature Phase Shift Keying CCK Complementary Code Keying
FHSS Frequency Hopping Spread Spectrum DSSS Direct Sequence Spread Spectrum QFN Quad Flat No-lead package SPI Serial Peripheral Interface I²S Integrated Interchip Sound
NFC Near Field Communication
PPI Programmable Peripheral Interconnect BLE Bluetooth low Energy
Wi-Fi Wireless Fidelity (IEEE 802.11) MCU Micro Controller Unit
CPU Central Processing Unit RAM Random Access Memory FPU Floating Point Unit ANT Antenna
SoC System-on-Chip
ARM Advanced RISC Machine
OTA DFU Over-The-Air Device Firmware Upgrade RSSI Received Signal Strength Indicator FIFO First In, First Out
GPIO General - Purpose Input/Output ADC Analog to Digital Converter DC/DC Direct Current to Direct Current IoT Internet of Things
IEEE Institute of Electrical and Electronics Engineers
Mathematical notation
GHz Giga Hertz MHz Mega Hertz kB Kilobyte
Kbps KiloBytes Per Second Mbps MegaBits Per Second mA milliampere
Mbps MegaBits Per Second Ppm Parts Per Million
dBm Decibel relative to one milliwatt
1 Introduction
Wireless Sensor Networks (WSN) become very popular in research topics as they provide a promising platform with a flexible infrastruc-ture that allows variety of control methods to monitor different applica-tions in a lot of fields
The typical WSN is composed of two primary components which are: the node and the base station as indicated in Fig 1[1]
Fig. 1 [1]
In order to define the components of this typical system we have to know that the node is the device that has the sensor, transceivers and processing unit that are spread in multiple sites to monitor and gather information about certain phenomena ,while the base station is the part of the system that is responsible for collecting the received data from different nodes and keep them in the system storage based on the pur-pose of the system more over the base station sometimes can act as a gateway or router for data to give the data the remote manageability [1]
The node and the base station are communicating through different communication channels in order to transfer the gathered information between them. WSN uses wireless personal area network (WPAN), Bluetooth, ZigBee and RFID to transfer data between them .different details will be shown next for each type of these links to have a more detailed look about these communication links
is urgent because this can lead to a considerable reduction of costs for…, increased market shares within… and an improved work environment.”
1.1
System Requirements
WSN systems have some requirements to ensure the smooth and flexible operation of the system, the system should have the following characteristics [2]
1. Affordable: the price of the components of the system must have low price since the system consists of thousands of nodes that spread in different location, also the price of the maintenance of the system should be economic inorder to achieve a realistic de-ployment
2. Secure: WSN should support the three services for security which are confidentiality, authenticity, and integrity
3. Programmable: nodes of WSN should have the programming ability to be able to modify the different functionality of them so that they can adapt to different operation requirement without the need to change the whole system
4. Fault tolerance: WSN should be able to handle node failure, also some kind of alarming mechanism should be available to show that there is an error at one of the nodes or a communication link 5. Scalable: WSN should support large number of nodes beside
adding extra nodes when needed 6.
1.2
Challenges of WSN
With the advancements in electronics components, power resources and communication links there are many challenges that must be understood when designing WSN [1]
1. limitation of functions: the nodes of WSN are characterized with limited resources so a well-designed architecture must be used to make the most out of these limited resources
2. Energy limitations: most of the nodes are placed in wide geo-graphical location or in a remote and hard to reach areas, so managing the available energy resources on the node must be deployed in an efficient way to increase the reliability of the node 3. Global identifications: Due to the large number of nodes in
WSN it is hard to make global identification (GID)for nodes, alt-hough some of the nodes use GPS satellites but this requires line of site with the sky and this is not available at some of the loca-tions
4. Latency: WSN should get the readings to be on the system with a suitable delay for each application, in some applications the con-tinuous change in the environmental conditions put constraints on the time delay in order to get readings before getting the read-ings out of date
1.3
Application of WSN
Military application : WSN was initially invented for military applications, it
was aiming to give monitoring system for remote areas about the movements of enemies or friendly armies, the usage of WSN in this application will require dense deployment for some nodes so that the damage of some nodes does not make an effect on the military operation [1]
Environmental monitoring: this type of applications covers a large
geographical area in order to record and monitor physical phenomena like: forest fires, level of carbon dioxide in air which can help in early detection of fire forest in remote areas, the nodes send the recorded and measured data to the central database according to a programmed way
Home automation: with technology advancements, nodes with the help of
mobile applications can offer extra control over home appliances like vacuum cleaner, air conditioner and microwave oven
Medical applications: WSN can be used by attaching a node to a patient to
measure his vital processes like heart beat and send it directly to his doctor or health care team within the hospital in order to give live health monitoring to the doctor
1.4
Architecture of WSN
WSN consists of three main components which are: wireless link, operating system and sensor nodes (some of them have built-in wireless link) with their circuitry [1]. We will show latest trends in these three components within the next section
2 Theory
RF communication
[3]RF communication works basically based on electromagnetic wave. The wave carries the electromagnetic energy of electromagnetic field through space. This wave includes different rays like Gamma rays, ultraviolet, visible light, infrared rays, Microwave rays and Radio Wave. Usually Radio waves used for wireless communication to carry signals. RF Transceivers are working in both way as transmitter and receiver in a single module. Since wireless communication started RF transceivers has been used. The main purposes of RF transceivers are to exchange information in the form of Voice, video and data. Which enables us to transmit them in a wireless medium. One of the important factors in RF communication is Antenna size. To optimize transmission and receiving data, an antenna should be where λ is the wave length of the carrier frequency, the other factor is energy consumption the energy consump-tion should be as low as possible. RF communicaconsump-tion has different advantages the likes of it is easy to use, its integrality with other devices and we can find it easily in the market.
Modulation Schema used, Data rate and transmission power affect the power consumption of Radio. There are four different operation modes of radios: Transmit, receive, Idle and sleep. From this mode of operation idle mode consume high power almost equal to receiving mode there-fore is important shutting down the Radio than leaving it idle.
General operational Modes of RF transceiver: RF transceivers can be configured to power down, standby, RX and TX mode.
Power down mood: The RF transceiver is switched off by the least
current consumption.
Standby mood I: Standby mode I is used to minimize average current
consumption while maintaining short start up times.
Standby mood II: more current is being used comparing to Standby
RX mood: it is an active mood where the transceiver used as a receiver. TX mood: it is also an active mood used as transmitting packets.
Fe1atures of RF Transceiver
[3] • GeneralWorldwide 2.4 GHz ISM band operation
Common antenna interface in transmit and receive GFSK modulation
250kbps, 1 and 2Mbps on air data rate • TX
Programmable output power: 0, -6, -12 or -18dBm 11.1mA at 0dBm output power
• RX
Fully integrated synthesizer
1 MHz frequency programming resolution Accepts low cost ±60 ppm 16 MHz crystal
1 MHz non-overlapping channel spacing at 1 Mbps 2 MHz non-overlapping channel spacing at 2 Mbps • Enhanced ShockBurst™
1 to 32 bytes dynamic payload length
Automatic packet handling (assembly/disassembly)
Automatic packet transaction handling (auto ACK, auto retrans-mit)
Fig.2 RF transceiver block diagram [3]
There is a number of different RF short range transceivers in the market for the Likes of nRF24 series and so on and can be given all details, Tabl.1 shows different Rf24 series and there basic specification with their prices from Nordic semiconductor.
Table.1 Comparison table of nRF24 series [4]
Part No.
Operating Frequency Type ISM Supply voltage Operating Temp Max.data rate Iterface Type Packag e/case Price nRF2401A 2.4 GHz 1.9v – 3.6V -40 to+85C 1Mb/s QFN-24 3,53€ nRF24AP1 2.4GHz 1.9v – 3.6V -40 to+85C 1 Mb/s QFN-24 6,82€ nRF24L01+ 2.4GHz 1.9v – 3.6V -40 to+85C 2 Mb/s SPI QFN-20 3,02€ nRF24LE1 2.4GHz 1.9v – 3.6V -40 to+85C 2 Mb/s SPI QFN-24 5,84€ nRF24AP2 2.4GHz 1.9v – 3.6V -40 to+85C 1 Mb/s QFN-32 6,25€ nRF24L01 2.4GHz 1.9v – 3.6V -40 to+85C 8 Mb/s SPI QFN-20 3,28€ nRF2401A 2.4GHz 1.9v – 3.6V -40 to+85C 1 Mb/s QFN-24 3,53€ nRF905 433 MHz to 915 MHz 1.9v – 3.6V -40 to+85C 50 kb/s SPI QFN-32 3,78€NRf24L01 Transceiver:
[5]NRF24L01 is a single chip radio transceiver developed by Nordic semiconductor. It Operate in the license-free 2.4GHz – 2.5GHz ISM band. It supports data rate 250kbps, 1Mbps and 2Mbps. For data rate of 250kbps and 1Mbps the channel bandwidth is approximately 1MHz. taking the minimum and maximum operating frequencies of 2400MHz and 2525MHz this gives 125 possible RF channels. However, at Baud of 2Mbps it occupies 2MHz bandwidth so to avoid overlapping channels and cancels the cross-talk at 2Mbps, it is recommended to keep 2MHz spacing between channels or more than 2MHz.
The nRF24L01+ transceiver module is the cheapest "2"-way RF solutions. The voltage operates from 1.9 to 3.6 V, but the logic pins are 5-volt tolerant, so it can be attached to an Arduino or 5V logic micro-controller without any level converter. The module withdraws a current of 12 mA while transmitting that is even lower than one LED. Built-in power down and standby modes makes power saving easily realizable.
SPI interface
[6]nRF2401+ transceiver module communicates over a 4-pin Serial Peripheral Interface (SPI) with a maximum data rate of 10Mbps.SPI basically works by the idea of master and slave in most application, the nRF2401+ works as a slave.
The nRF24L01+ has a feature that is called Multiceiver. It is stands for Multiple Transmitters Single Receiver. This feature allows each RF channel with a set of 6 unique addresses data pipes so that each module can communicate with 6 other modules in the same RF channel
2.1
BLE (
Bluetooth Low Energy) Communication Modules
[7] Bluetooth Low Energy: it is a wireless protocol operating in 2.4 GHz ISM band, since it operates in small coin cell battery, it is product and application depends on low power consumption. Over the last couple of years BLE evolves from Bluetooth 4.0 – Bluetooth 5 and Bluetooth 5.1. BLE helps us to connect devises and send data wirelessly. We are not only use BLE to connect devices to smart phone, it gives us a very wide option of connections wirelessly between two BLE devises, for instance we can use Bluetooth in Credit cards, sport equipment’s, door locks, automo-biles, gas sensors, light bulbs and so on.There is so many options in chip selection of BLE in the market, in this survey I focus on commonly used, good software support, Better RF performance and coastwise. Since Nordic semiconductor has been the best in BLE chips seller in the past year this survey based on, nRF52810, nRF52811, nRF52832, and nRF52840 chipsets. This chipset is commonly used in consumers and industrial prod-uct because of their easiness to use and good SDK support.
DEVELOPMENT TOOLS [8]
Nordic Semiconductor provides a complete range of hardware and software development tools for the nRF52 Series devices.
SoftDevices [8]
The Nordic protocol stacks are known as SoftDevices and comple-ment the nRF52 Series SoCs. All nRF52 Series are programmable with software stacks available from Nordic Semiconductor. This brings
stack version to be programmed into the nRF52 Series SoC. In this survey I focus on nRF52 Series for BLE.
BLE Device Comparison
Table.2. BLE Device comparison [9]
From this Devices I mentioned and compare above the nRF52832 is the most popular chipsets used in many products. The extensive study of this module be given under
nRF52832: is a multiprotocol Bluetooth low energy (Bluetooth 5) ANT/ANT+ and 2.4GHz proprietary System-on-Chip Device. The nRF52832 is a powerful multiprotocol single chip solution for ULP wireless applications. It incorporates Nordic’s best-inclass perfor-mance radio transceiver, an ARM® Cortex™ M4F CPU and 512kB flash and 64kB RAM memory. The nRF52832 supports Bluetooth® low energy (Bluetooth 5), ANTTM and 2.4GHz proprietary proto-col stacks. The device also has a NFC-A tag interface for OOB pairing. [8]
Lowe power and higher performance: nRF52832 uses the 32-bit ARM Cortex M4F MCU together with extensive flash availability, 512kB in total with 400kB available for application development. Speed are considerably greater than for 8/16-bit platforms. The Programmable Peripheral Interconnect (PPI) system provides a 20-channel bus for direct and autonomous system peripheral com-munication without CPU intervention. This brings predictable latency times for peripheral to peripheral interaction and power saving benefits associated with leaving the CPU idle. The device has 2 global power modes ON/OFF, but all system blocks and peripherals have individual power management control which allows for an automatic switching RUN/IDLE for system blocks based only on those required/not required to achieve particular tasks.
The new radio is designed to support the Bluetooth 5 2Mbs mode. This means the nRF52832 can be qualified for Bluetooth 5 applica-tions. It supports Bluetooth low energy (Bluetooth 5), ANT and proprietary 2.4GHz applications. Output power is programmable between +4dBm and 20dBm and has receiver sensitivity of -96dBm for Bluetooth low energy 1Mbs). [8]
OTA DFU: The nRF52832 is supported by an Over-The-Air Device Firmware Upgrade (OTA DFU) feature. This allows for in the field updates of application software and Soft Device. Has a specification of On-air-data rate 2 Mbps and 1 Mbps Bluetooth LE, 1 Mbps ANT, 2 Mbps and 1 Mbps 2.4GHz proprietary [8]
Maximum re-use and easy migration: The nRF52832 have binary compatible peripherals with the nRF51 Series for most functions enabling easy migration between older parts and the new nRF52 Series. The backwards compatibility of most interfaces and the common SW architecture of the nRF51 Series S130 and the nRF52 Series S132 SoftDevices ensures that existing codebase for the nRF51 Series can in very large parts be re-used effortlessly on the nRF52 Series. [8]
nRF52832: KEY FEATURS [8] • Bluetooth 5 - 2Mbs mode
• 32-bit ARM Cortex M4F processor • 512kB flash + 64kB RAM
• interface: SPI/2-wire/ I²S/UART/PDM/QDEC
• Application development independent from protocol stack • Supports 1Mbit and 2Mbit Bluetooth low energy modes • On-air compatible with nRF51, nRF24AP and nRF24L Series • Sensitivity of -96 dbm for Bluetooth low energy
• Programmable output power from +4dBm to -20dBm • RSSI
• RAM mapped FIFOs using EasyDMA
• Dynamic on air payload length up to 256 Bytes • Flexible and configurable 32 pin GPIO
• Programmable Peripheral Interface – PPI • Simple ON/OFF global power modes • 12-bit/200KSPS ADC
• Quadrature demodulator
• Low cost external crystal 32MHz ± 40ppm for Bluetooth, ± 50ppm for ANT
• Single-ended antenna output (On-chip Balun) • Low power 32MHz crystal and RC oscillators • Ultra low-power 32kHz crystal and RC oscillators • Wide supply voltage range (1.7 V to 3.6 V)
• On-chip DC/DC buck converter
• Individual power management for all peripherals • Package options: 48-pin 6x6 QFN/WL-CSP
ESP32 [11]
ESP32 chipset includes Wi-Fi, Bluetooth Classic, Bluetooth Low-Energy, and a 240 MHz microcontroller and it’s still cheaper than any of the other modules, because of this I included it in this survey for comparison. It is designed and optimized for the best power performance, RF performance, robustness, versatility, features and reliability, for a wide variety of applications and different power profiles. ESP32 is applicable on Mobile, wearable electronics and internet of things ((IoT) application.
ESP32-contains dual core low-power Xtensa® 32-bit LX6
micro-processor. It has two separate processor cores that can be con-trolled individually.
Clock frequency from 80MHz to 240MHz Flash memory 16MB
Fig.5. ESP32 [12]
2.1.1 ZigBee: [13]
Zigbee is a standard that specifies the network stack above 802.15.4, there are many stacks based on 802.15.4: Zigbee, XBee, DigiMesh, Thread, etc. Zigbee only works on 802.15.4. 802.15.4 is a PAN ("Personal Area Network") technology, features that make it different from WiFi and Bluetooth is low speed, low energy, network resilience and extremely simple radio stage.
Zigbee supplies a complete network stack, top to bottom. Even the application data types and their encodings are rigidly specified. It is applicable on Smart home, building, industrial, retails, health and more.
Fig.6.Zigbee application layer [14]
NRF52840 SoC is recommended for Zigbee from Nordic semiconduc-tor. It is a fully multiprotocol capable with full protocol concurrency. It is Dynamic multi-protocol transceiver support, Bluetooth 5 / Bluetooth low energy, IEEE 802.15.4/Thread, ANT/ANT, Proprietary 2.4GHz
KeFeatures of nRF52840 [13]
Microprocessor 64 MHz 32-bit Arm Cortex-M4 with FPU
Memory 1 MB Flash + 256 KB RAM
Operating Voltage Range 1.7 -5.5V
On-air data rate 802.15.4: 250 kbps
interface SPI/UART/PWM
2.2
WiFi Communication [15]
Wireless fidelity (Wi-Fi) or by it is Standard IEEE 802.11, first released in 1997 and since then is has been modified many times to achieve high level of quality of service (QoS) that include IEEE 802.11a/b/g standards for wireless local area networks (WLAN), this three versions basically function at 2.4GHz Frequency band for IEEE 802.11b/g and 5GHz Frequency band for IEEE 802.11/a. Wi-Fi use Unlicensed ISM band, its protocol is Spread Spectrum technique which is open for public use, the problem of Wi-Fi is that it is availa-ble for public use, when too many devices nearby to a Wi-Fi network can interfere each other since they use the same Band. To avoid such interference a 5m distance between the devices is recommended. Wi-Fi allows users to surf the Internet at broadband speeds when connected to an access point (AP) or in ad hoc mode. Next, we will see some of the communication modules of Wi-Fi. In this survey I will present Wi-Fi module form ESPRESSIF vendor. Espressif offer wide range of fully-certified Wi-Fi and BT SoC mod-ules.
Dual-core, single-core and single-core with 802.11b/g/n 2.4 GHz Wi-Fi are some of the module ESPRESSIF provide.
DUAL-CORE: Features [16]
• Has two independently-controlled CPU cores with adjustable clock fre-quency, ranging from 80 MHz to 240 MHz
• +19.5 dBm output at the antenna ensures a good physical range
• Sleep current is less than 5 μA, making it suitable for battery-powered and wearable-electronics applications.
• Integrates 4 MB flash.
• Peripherals include capacitive touch sensors, Hall sensor, low-noise sense amplifiers, SD card interface, Ethernet, high-speed SPI, UART, I2S and I2C
SINGLE-CORE: Features [16]
• High-performance 160 MHz single-core CPU
• +19.5 dBm output at the antenna ensures a good physical range
• Sleep current is less than 5 μA, making it suitable for battery-powered and wearable-electronics applications
• Peripherals include capacitive touch sensors, Hall sensor, low-noise sense amplifiers, SD card interface, Ethernet, high-speed SPI, UART, I2S and I2C
• Fully certified with integrated antenna and software stacks
Table.5. Single Core ESP32 [16]
SINGLE-CORE MODULES WITH 802.11b/g/n 2.4 GHz Wi-Fi: Features
• High-performance 160 MHz single-core CPU
• +19.5 dBm output at the antenna ensures a good physical range
• Sleep current is less than 20 μA, making it suitable for battery-powered and wearable-electronics applications
• Peripherals include UART, GPIO, I2C, I2S, SDIO, PWM, ADC and SPI • Fully certified with integrated antenna and software stacks [16]
ESP8266 WiFi Module
[17]ESP8266 is a complete and self-contained Wi-Fi network solutions that can carry software applications, it is a single-core Soc, it is applicable especially for mobile platform designers, provide an excellent capability to embed Wi-Fi with in other systems at low cost with greatest functionality.is around 6$. ESP8266 has a Built-in cache memory which will help improve system perfor-mance and reduce memory requirements and we can add it to any microcon-troller-based design, the connection is simple, just by SPI / SDIO interface or central processor AHB bridge interface. It can be integrated via GPIO ports, ESP8266 is highly integrated chip, including antenna switch balun, power management converter, it requires minimal external circuitry and includes front-end module, The system equipped with ESP8266 manifested leading features are: energy saving VoIP, quickly switch between the sleep / wake patterns, with low-power operation adaptive radio bias, front-end signal processing functions, troubleshooting and radio systems coexist features for common cellular / Bluetooth / DDR / LVDS / LCD interference.
Ultra-low power technology [17]
ESP8266 specifically for mobile devices, wearable electronics and networking applications design and make the machine to achieve the lowest energy con-sumption, together with several other patented technology. This energy-efficient constructed in three modes: active mode, sleep mode and deep sleep mode type. ESP8266 use high-end power management technology and logic systems to reduce non-essential functions of the power conversion between sleep patterns and work modes, in sleep mode it consumes less than 12uA current. Through programming, ESP8266 will automatically wake up when specific condition detected. ESP8266 automatic wake-up in the shortest time.
INTERFACE
ESP8266 contains multiple analog and digital interfaces, as follows: Main SI / SPI control (optional)
Main Serial Interface (SI) can run at two, three, four-wire bus configura-tion, is used to control the EEPROM or other I2C / SPI devices. Multiple devices share the two-wire I2C bus. Multiple SPI devices to share the clock and data signals, according to the chip select, each controlled by
such as serial flash, audio CODEC or other slave devices, installation, effectively giving it three different pins, making it the standard master SPI device. • SPI_EN0 • SPI_EN1 • SPI_EN2 FEATURES OF ESP8266: [17] • 802.11 b/g/n protocol • Wi-Fi Direct (P2P), soft-AP • Integrated TCP/IP protocol stack • Frequency range 2.412GHz – 2.484GHz • Working voltage 3.3V-3.6V
• Power down leakage current of < 10uA
• Integrated low power 32-bit CPU could be used as application processor
• SDIO 2.0, SPI, UART
• Wake up and transmit packets in < 2ms
• Standby power consumption of < 1.0mW (DTIM3) • Supports antenna diversity.
2.3 POWER CONSUMPTION: [15]
The two aspects in WSN, regarding power consumption is the power flow optimization between the storage elements (battery and supper- capacities) and the power management related to the wireless transmis-sion and successive functional stage of the micro-controllers and sensor transceivers.
ZigBee and Bluetooth LE mainly designed for portable devices and limited battery power because of this they have low power consump-tion, there for they are not affected significantly their battery life time. Wi-Fi is considered for a longer connection and support devices with a considerable power supply. Normally Wi-Fi is for bulk traffic transfer at high speed. Even if ZigBee and BLE protocols consume less power, Wi-Fi have a better energy consumption efficiency. Here under we will see graphically the different of power consumption and energy consump-tion efficiency for each protocol. The graph shows BL and ZigBee have a very low power consumption comparing with Wi-Fi.
The graph below shows Wi-Fi have a considerable better energy consumption efficiency per bit than BL and ZigBee
Fig.8. Comparison of Energy consumption efficiency [15]
2.4 MICROCONTROLLER:
Microcontrollers perform the main task in sensor nodes since sensor nods expect to be communicate. For processing and gathering sensor data, sensor nods should have processing unite with better energy consumption and computational capability of data with different opera-tional modes. Generally, microcontrollers include not only memory and processor unit but also non-volatile memory and different interfaces such as UART, USB, SPI and I2C, and peripherals such as A/D Convert-ers (ADCs), countConvert-ers and timConvert-ers because of this MUC can easily inter-face with digital and along sensors. Microprocessors and programmable logic allow great flexibility for CPU implementations.
There is a number of microcontrollers in the market which is used for wireless sensor network from 4 – 32 bits. PIC MUC, 80551 MUC, AVR MUC are 8-bit microcontroller.
The Texas Instruments MSP430F169 is a 16-bit, 8 MIPS, and ultra-low power CPU. It has 60Kbytes of program memory and 2Kbytes of data memory and The Motorola DragonBall MC9328MX1 is a 32-bit CPU with a Bluetooth Accelerator radio interface, an Analog Signal Pro-cessing (ASP) Module, a Multimedia Accelerator (MMA), and a DPLL Clock and Power Control Module that provides power management capabilities.
The three-wireless protocol in this survey use a microcontroller ARM CORTEX-M4 processor which is one of ARM CORTEX-M series, this series was released a few years ago, ARM CORTEX-M processor family is optimized for energy-efficient microcontrollers and found in many applications like in IoT, industrial and consumer devices.
This processor family is based on the M-profile Architecture that provides low-latency and have high accurate performance for deeply embedded system. Cortex-M55 is the latest in the market which is built on Armv8.1-M architecture with Arm Helium technology. The series start from Cortex-M0 processor, Cortex-M0 is the smallest Arm processor.
ARM CORTEX-M4: is designed to address digital signal that demands
an efficient, easy to use and signal processing capabilities. The benefit of ARM CORTEX-M4 is highly efficient signal processing functionality with low power and low cost this satisfy to be choices for the above wireless protocol. ARM CORTEX-M4 core with FPU is the latest generation of ARM processor for embedded system. It has low cost and low power consumption with small number of pin count this satisfy the need of MCU implementation. ARM CORTEX-M4 is built on Armv7E-M architecture.
Architecture Armv7E-M
Bus Interface 3x AMBA AHB-Lite interface (Harvard bus architecture) AMBA ATB interface for CoreSight debug components ISA Support Thumb/Thumb-2
Pipeline 3-stage + branch speculation DSP Extension Single cycle 16/32-bit MAC Single cycle dual 16-bit MAC 8/16-bit SIMD arithmetic Hardware Divide (2-12 Cycles)
Floating-Point Unit Optional single precision floating point unit IEEE 754 compliant
Memory Protection Optional 8 region MPU with sub regions and background region Bit Manipulation Integrated Bit Field Processing Instructions & Bus Level Bit Banding
Interrupt Priority Levels 8 to 256 priority levels Wake-up Interrupt Controller Optional
Sleep Modes Integrated WFI and WFE Instructions and Sleep On Exit capability Sleep & Deep Sleep Signals
Optional Retention Mode with Arm Power Management Kit
Debug Optional JTAG and Serial Wire Debug ports. Up to 8 Breakpoints and 4 Watchpoints
Trace Optional Instruction Trace (ETM), Data Trace (DWT), and Instrumentation Trace (ITM)
Table.7. ARM CORTEX-M4 Specification Table
2.5
Operating system
TinyOS [18]
TinyOS is a tiny microthreaded OS that attempts to address two issues: how to guarantee concurrent data flows among hardware devices, and how to provide modularized components with little processing and storage overhead. TinyOS uses an vent-based model to support high levels of concurrent application in a very small amount of memory. Compared with a stack-based threaded approach, which would require that stack space be reserved for each execution context, and because the switching rate of execution context is slower than in an event-based approach, TinyOS achieves higher throughput. It canrapidly create tasks associated with an event, with noblocking or polling. When CPU is idle, the process is maintained in a sleep state to conserve energy
TinyOS has a component-based programmingmodel, codified by the nesC language. his WNS operating system defines three types of com-ponents: hardware abstractions, synthetic hardware, and high-level software components.
Contiki OS [18]
The Contiki operating system is an open source operating system for networked embedded systems in general, and wireless sensor nodes in particular.
Contiki system consists of the kernel, libraries, the program loader, and a set of processes. Communication between processes always goes through the kernel, which does not provide a hardware abstraction
layer, but lets device drivers and applications communicate directly with the hardware . Both the Contiki system and applications for the system are implemented in the C programming language. Because Contiki is implemented in C, it is highly portable. Contiki has been ported to a number of microcontroller architectures, including the Texas Instruments MSP430 and the Atmel AVR
Lite OS [18]
Lite OS is designed to provide a traditional Unix-like environment for programming WSN applications, it partitioned into three subsystems: Lite Shell, Lite FS, and the Kernel. Implemented on the base station PC side, the Lite Shell subsystem interacts with sensor nodes (motes) only when a user is present .Lite OS 2.0 is closely integrated with AVR Studio 5.0. This brings multiple advantages, such as IDE editing, debugging, and built-in JTAG support. LiteOS also supports software updates through a separation between the kernel and user applications, which are bridged through a suite of system calls.
3 Methodology
This survey was done by referring different Study papers, I have been trying to refer recently done Study papers since WSNs technology have a lot of development throw time, to make sure the specifications are precise I have been referred Datasheet form product developers and producers.
4 Results
Over all comparison of Bluetooth, Zigbee and Wi-Fi protocols!
Standard
Bluetooth Zig bee
Wi-Fi
IEEE spec. 802.15.1 802.15.4 802.11a/b/g
Frequency band 2.4 GHz 868/915MHz;2.4 GHz
2.4 GHz; 5 GHz
Max signal rate 1Mb/s 250Kb/s 54Mb/s
Nominal range 10m 10–100 m 100 m
Nominal TX power 0–10 dBm (™25)– 0 dBm 15–20 dBm
Number of RF channels 79 1/10;16 14 (2.4 GHz)
Channel bandwidth 1 MHz 0.3/0.6MHz; 2 MHz 22 MHz Modulation type GFSK BPSK (+ ASK),
O-QPSK
BPSK,
QPSK,COFDM, CCK, M-QAM
Network size 8 65000 2007
Data protection 16-bit CRC 16-bit CRC 32-bit CRC Power Consumption Medium Very low High Network topology A-hoc,small
network
Peertopeer,star or mesh
Point to point
Spreading FHSS DSSS DSSS
Power consumption
Table.9. Power consumption comparison for selected protocols [19]
Standard
RF
NRf24L01
Bluetooth
NRF52832
Zig bee
nRF52840
Wi-Fi
ESP8266
Standard Nrf24 Nrf52 Nrf52 Wi-Fib/g/n Frequency band 2.4GHz 2.4GHz 2.4GHz 2.412GHz- 2.484GHzMax signal rate 2 Mb/s 1Mb/s 250Kb/s 54Mb/s
Nominal range 15m-60m 10M 10M-100M 100M
Nominal current 50mA 80mA
Supply voltage 1.9v – 3.6V 1.7V – 3.6V 1.7v - 5.5v 3.3V -3.6V
CPU N/A 64 MHZ ARM
Cortex M4
64 MHZ ARM Cortex M4
ULP 32-bit cpu
Memory N/A Flash 256/512KB
RAM 32/64KB
Flash 1MB RAM 256KB
N/A Table.10. Comparison of selected chips form all protocols
Current and power consumption comparison from selected chip NRF24L01 [6] Standby-1---26μA Power down----900nA Rx mode---13.5mA@2Mbps Tx mode--- 11.3mA@0dBm Power consumption ----60mW Pow.Effciency---2.48 µW/bit NRF52832 [20]
Tx mode--- 5.3mA peak current (0dBm) Rx mode---5.4mA peak current in Rx.
Power and clock management in nRF52832: the main point of power and clock management system in nRF52832 is the power management unit (PWM)
Fig.9. Power management unit
The user application is not required to actively control power and clock, since the PMU is able to automatically detect which resources are
re-PMU will continuously optimize the system based on this
information
to achieve the lowest power consumption possible without user interac-tion.
There is different current consumption scenarios as the system being constantly tuned by the PMW, knowing the energy consumption of an application can be challenging if the designer is not able to do meas-urements on the hardware directly.
nRF52840
Compound current consumption of nRF52840: estimating the current consumption of an application can be challenging if the designer is not able to perform measurements directly on the hardware. To facilitate the estimation process, a set of current consumption scenarios are provided to show the typical current drawn from the VDD supply. Each scenario specifies a set of operations and conditions applying to the given scenar-io.
Table.12.Compound current consumption of nRF52840 [21]
ESP8266 power consumption
[22]Table.13.Test data of power consumption of ESP8266
Currently ESP8266 can support three low power mode: Light
5 Conclusions
This survey gives a broad overview of some of known RF communi-cation technology like RF, BLE, ZigBee and Wi-Fi, with a comparison in terms of specification some of the specification are stable and well defined by the standard, others such as power consumption and energy efficiency are open challenge and throw time the technology is improv-ing this aspect. It is difficult to give a simprov-ingle conclusion comparimprov-ing which one is better than the other, we can say Wi-Fi and Bluetooth LE provide higher data rate, while ZigBee gives us lower data rate, Gener-ally ZigBee and Bluetooth LE intended for WPAN communication and Wi-Fi is for WLAN in about 100m how ever in some application ZigBee can reach 100m range. Regarding power consumption and Energy Efficiency we can look the table and graph in the theory.
The suitability of WSN protocols are highly regarded by the Applica-tion we choice to implement but as I give a comparison table for each protocol, which chipset set is better depend on application we are doing and cost wise, for RF communication the nRF24L01 chipset is recom-mended, for Bluetooth LE the nRF52832 is the popular chipset, there is ESP32 chipset for this protocol which have a lot of good features but the power consumption is around 100mA when using BLE radio this is over 10 times the current consumption that other BLE chips consume, for ZigBee the nRF52840 is recommended for its dynamism of support other protocols. For Wi-Fi, ESP8266 is recommended because of it is functionality and lower cost.
Microcontrollers: there is a lot of options in the market to select microcontrollers for WSN, in this survey I have been focused on one ARM microcontroller product ARM CORTEX-M4.
5.1
Future work
The survey focused on some of the common RF transceivers for short-range WSN technologies, there is a lot of RF transceivers and WSN protocols that can be considered, those are some of the protocols that can be seen in the future, Z-wave, NFC, HomePlug GP and UWB (Ultra-wideband) is recently have got a lot of attention in the market for un indoor short-range high speed wireless communication since it use a very low energy. Regarding RF transceivers there is plenty of options from Texas instrument, CC1101, CC2500, CC120 and many other products can be included. The same for microcontrollers there is different type of MUC that I mentioned in the theory can be presented extensively in the future
References
Here follows an example of an automatically numbered list of references according to the numbered list and cross references method, as de-scribed in chapters 2.4:
[1] Pule, Mompoloki, y Yahya, Abid, y Chuma, Joseph, y "Wireless sensor networks: A survey on monitoring water quality." Journal of Applied Research and Technology, vol. 15, no. 6, 2017
[2] Potdar, Vidyasagar & Sharif, Atif & Chang, Elizabeth. (2009). Wireless Sensor Networks: A Survey. Proceedings - International Conference on Advanced Information Networking and
Applications, AINA. 636-641. 10.1109/WAINA.2009.192.
[3] Nordic semiconductor ,” nRF24L01+Single Chip 2.4GHz Transceiver “Preliminary Product Specification v1.0,March 2008
[4]
https://eu.mouser.com/Nordic- Semiconductor/Semiconductors/Wireless-RF-Integrated-
Circuits/RF-Transceiver/_/N-3ri0rZ1yzvvqxZscv7?P=1yzrqvv&fbclid=IwAR00YVbQ6b_OqCcr CUw66XVGVFuG-O9kOUE4YZ0jIGf4UVIrm-xw52DyAzc
[5] Preliminary Product Specification: Revision Date: 08.03.2006. Data sheet order code: 080306-nRF24L01
[6] https://lastminuteengineers.com/nrf24l01-arduino-wireless-communication/ [7] https://www.nordicsemi.com/Products/Low-power-short-range-wireless/Bluetooth-5 [8] https://infocenter.nordicsemi.com/pdf/nRF52832_PB_v1.7.pdf [9] https://infocenter.nordicsemi.com/topic/struct_nrf52/struct/nrf52. html [10] https://www.aliexpress.com/item/32865934996.html
[11] https://www.espressif.com/sites/default/files/documentation/esp3 2_datasheet_en.pdf [12] https://www.makershop.de/plattformen/nodemcu/espressif-esp32-dev-kit-board/ [13] https://infocenter.nordicsemi.com/topic/struct_nrf52/struct/nrf528 40.html [14] https://www.nordicsemi.com/Products/Low-power-short-range-wireless/Zigbee
[15] J. Lee, Y. Su and C. Shen, "A Comparative Study of Wireless Protocols: Bluetooth, UWB, ZigBee, and Wi-Fi," IECON 2007 - 33rd Annual Con-ference of the IEEE Industrial Electronics Society, Taipei, 2007, pp. 46-51.
[16] https://www.espressif.com/en/products/hardware/modules [17]
https://cdn-shop.adafruit.com/product-files/2471/0A-ESP8266__Datasheet__EN_v4.3.pdf
[18] Farooq, Muhammad & Kunz, T.. (2011). Operating Systems for Wire-less Sensor Networks: A Survey. Sensors (Basel, Switzerland). 11. 5900-30.
[19] Borza, P.N.; Machedon-Pisu, M.; Hamza-Lup, F. Design of Wireless Sensors for IoT with Energy Storage and Communication Channel Heterogeneity. Sensors 2019, 19, 3364. [20] https://infocenter.nordicsemi.com/index.jsp?topic=%252Fcom.nor dic.infocenter.nrf52%252Fdita%252Fnrf52%252Fchips%252Fnrf52 832_ps.html [21] https://infocenter.nordicsemi.com/index.jsp?topic=%252Fcom.nor dic.infocenter.nrf52%252Fdita%252Fnrf52%252Fchips%252Fnrf52 832_ps.html [22] https://bbs.espressif.com/viewtopic.php?t=133
