Lecture 4 - Components of IOT Flashcards
What are sensors?
- Different sensors available to measure temperature, humidity, light, noise, pollution, pressure, torsion, tension, acceleration, position, images, magnetic fields, electric fields, etc etc.
- Sensors are now invisible and energy efficient, whilst maintaining a high measurement precision.
What are the key requirements for connectivity?
- Availability
- Reliability
- Viability
What is are the two frequency bands of a wireless system?
Frequency Band
Licensed
- With Infra-structure, based upon traditional cellular network such as celluar, paging, fixed wireless and satelite
—
Unlicensed - such as WLAN, bluetooth, machine to machine and PAN
- Infrastructureless, Adhoc
- Peer to Peer,
- Self-Organizing
What are the issues with wireless channel?
- Wireless communications is highly variable.
- Data sent over those channels is: error-prone, unreliable, latency issues
- The lesson is that wireless channels require aggressive management.
What are the requirements for a wireless system?
System Requirements
* Capacity: Bits flowing reliably (bps)
* Latency: Delay in delivering bits
* Coverage: Percentage of geographical locations with minimum level of service
* Cost of service
Additional Requirements on Transceiver:
* Power Consumption: Battery life, Complexity
* Portability: Size and weight
* Cost of Transceiver
What are the Data Transmission Requirements
Data Rate
Bit Error rate - BER
Latency
Traffic
What are the Spectrum Regulations
- In Australia frequency spectrum is controlled by ACMA, Australian Communications and Media Authority
- FCC, Federal Communications Commission in USA
- ETSI (European Telecommunications Standards Institute) in Europe.
- World wide spectrum is controlled by ITU Radio communication Sector (ITU-R)
- Auction spectral blocks for set applications e.g expensive 3G, 4G Auctions.
- Some spectrum for unlicensed use, which means that no one has to pay for leasing or buying that spectrum.
- Minimal rules on how can the spectrum be used, the so-called etiquette rules, e.g power spectral density of the emission at a particular point, most often, the antenna.
- These bands may become congested.
- A new approach to allow secondary (un-licenced users) to use primary ( licenced) spectrum with minimum interference, primarily restricted power transmission, example, UWB ( Ultra Wide Band)
What is Ultra-wideband?
- Ultra-wideband is a technology for transmitting information across a wide bandwidth (>500 MHz). This allows for the transmission of a large amount of signal energy without interfering with conventional narrowband and carrier wave transmission in the same frequency band.
What is the ISM Band?
- The Industrial, Scientific and Medical radio bands (ISM bands) are radio bands reserved internationally for the use of radio frequency energy for industrial, scientific and medical purposes other than telecommunications.
- Examples of applications in these bands include microwave ovens, medical diathermy machines etc.
- Communications equipment operating in these bands must tolerate any interference generated by ISM applications, and users have no regulatory protection from ISM device operation.
What is the Frequency band for IOT
For IoT, some bands are of particular interest,
* Band between 900 & 928 MHz - the ISM band.
* Similarly, in the areas of 2.4 gigahertz and 5.7 gigahertz.
* There are some bands at lower frequencies that are also appealing.
* These bands are essentially license-free operation so that a very large number of IoT devices can be deployed without having to pay for the usage of the band.
What is Wireless lan?
- The 802.11 working group currently documents use in five distinct frequency ranges: 2.4 GHz, 3.6 GHz, 4.9 GHz, 5 GHz, and 5.9 GHz bands.
- Each range is divided into a multitude of channels of bands.
- Countries apply their own regulations to the allowable channels, allowed users and maximum power levels within these frequency ranges.
What is Low Power Wifi (connectivity)?
- Wifi, despite higher power consumption, is a good candidate for IoT
- Wifi has achieved greater success and is nowadays has ubiquitously much higher presence
- Wifi has not been fairly suitable for sensor communication due to high energy consumption
- Wifi community started installing IC for duty cycle, whereby it remain in dormant mode if no sensing or transmission happening, thus making it energy efficient
- Further wifi can provide data rates from few Kbps to Mbps
- IEEE started working on IEEE 802.11ah, a wireless networking protocol published in 2017 to be called Wi-Fi HaLow (pronounced “HEY-Low”), where thousands of devices can be connected
- Applications
- Industrial Automation and Control
- Smart Metering
- Health Care Applications
What are some characteristics of Low Power Wifi?
- 6 thousands sensors can connect to single access point
- Can Communicate at 100 Kbps
- Default transmission power of 200 milli watt
- Range of about 1 KM compared to 10 meter or so of Zigbee
- Industrial, scientific, and medical radio band (ISM band) in the range of sub GHz
What is DBM?
- A power level of 0 dBm corresponds to a power of 1 milliwatt.
- To express an arbitrary power P in mW as x in dBm,
the following expression is used: x = 10 log (Base 10) (P/1mw) Or conversely P = 1 mw . 10(x/10)
2.4GHz vs 5Hz
- As the 2.4 GHz band becomes more crowded, many users are opting to use the 5 GHz ISM band. This not only provides more spectrum, but it is not as widely used by Wi-Fi as well as many other appliances including items such as microwave ovens, etc.
- Many of the 5 GHz Wi-Fi channels fall outside the accepted ISM unlicensed band and as a result various restrictions are placed on operation at these frequencies.
