Exam1 Flashcards
Internet of Things definition and what it enables
Network of physical objects, embedded with sensors, electronics, software, and network connectivity. Enables objects to collect and exchange data, and receive control commands and react accordingly
What is the data path
Data acquisition -> local data processing -> data communication-> data streaming -> data storage and cloud -> data analytics
What is data acquisition (DAQ)
Process of sampling signals that measure real world physical conditions, and converting the samples into digital numeric values that can be manipulated by a processor
What are DAQ systems integrated by
Sensors, to convert physical parameters to electrical signals
Signal conditioning circuitry, to convert sensor signals into a form that can be converted to digital values
Analog to digital converters, to convert conditioned sensor signals to digital values
What is a sensor
A device that responds to a stimulus or input quality by generating processable outputs
What is a transducer
A device that converts energy from one form to another (sensors are types of transducers)
What is the objective of a sensor
To achieve accurate and stable monitoring of target measurands
What rules to sensors try to follow
It is sensitive to the measurand property
It is insensitive to other properties it encounters
It does not influence the measured property
What is nanotechnology
Enables the development of miniature sensors that can measure events at a nanoscale. Smaller sensors and can measure magnitudes with extreme accuracy
What is signal conditioning
The manipulation of the analog signal in a way that it meets the requirements of the next stage. Examples of this is filtering (noise reduction and interference reduction) and amplification/attenuation (increase/decrease waves)
Analog vs digital signals
analog is based on circuit elements, digital is based on digital signal processors, A relies on analog systems to solve differential equations and B relies on numerical calculations applied to digital signal values, A is real time operations and B might not be real time, A is single purposeand B is flexible, A can have fluctuation in results based on system status (eg temperature) and B is repeatable
Analog to Digital Converter (ADC)
Samples signals in time - sampling frequency
Quantizes the sample amplitude - resolution
ADC is a big bottleneck for high speed digital signal processing/communications bc they are relatively slow
What are sensor interconnects
They enable the communication between the sensing unit with the processing unit. Some classification examples: analog vs digital, serial vs parallel, wired vs wireless
Tell me about serial communications
Send data one bit at a time. Some examples are CAN, I2C, USB
Tell me about parallel communicaions
Multiple bits are transmittable simultaneously. Some examples are CAMAC, PC Cards, ISA
Tell me about SPi
Synchronous serial interface, full-duplex, master-slave architecture with one master, rate is usually above 10Mbps. Uses 4 unidirectional lines. Basically, the master sets the clock and selects a slave device, then a master sends a bit over MOSI and slave sends a bit over MISO at the same time. This continues until data is done being sent and the master stops toggling the clock and deselects the slave.
Pros: faster than async, supports multiple slaves
Cons: needs more wires, master controls all communication (slaves cant talk to each other), and needs a separate line/wire for each slave
Tell me about I2C
Synchronous serial interface, packet switched, half-duplex, multi-master multi-slave, rates from 0.1 to max of 3.4 Mbps, only 2 lines/wires. Basically, the master sends a start bit with a 7 bit register address, and a bit for read/write. Then the slave with the register address sends back an ACK bit so then the data can start being transmitted (either slave sending or master sending). At the end of the data, the master sends back with a stop bit. Start bit is SDA high to low with SCL high, stop bit is SDA low to high with SCL high, everything else sent with SCL low.
Pros: only two lines, multiple masters and multiple slaves
Cons: slow, complex
Tell me about UART
Asynchronous serial interface (don’t synchronize with clock), full-duplex, minimal implementation is 2 lines, rates are from 9600 to 115200 bps. Basically, UART takes bytes of data and sends each bit in sequential fashion. A second UART reassembles the bits into bytes. idle state is high voltage. start bit is low. 5-9 bits are sent for one character.
Pros: simple, only two lines
Cons: can only communicate between 2 nodes, very slow
What are Computing Architectures
A set of rules and methods that describe the functionality, organization, and implementation of computer systems. Components are Instruction Set Architecture (ISA), Microarchitecture, and system design
What is Instruction Set Architecture (ISA)
Defines the machine code that the processor reads and actus upon, as well as word size, memory address modes, processor register, data types…
What is Microarchitecture
Describes how a particular processor will implement the ISA
What is System Design
includes all the other hardware components within a computing system
what is Complex Instruction Set Computer (CISC)
Architecture in which single instructions can execute several low-level operations (load from memory, arithmetic operations, memory store) or are capable of multi-step operations or addressing modes within single instructions. Examples are Intel x86,Intel 805 I, Motorola 68000
What is Reduced Instruction Set Computer (RISC)
Architecture that has a small set of simple and general instructions, rather than a large set of complex and specialized instructions. Usually, where memory is only accessed through specific instruction rather than a common part of most instructions. Examples are ARM, Atmel AVR, MIPS…
Tradeoffs of computer architectures
Performance with speed, latency and throughput, power requirements and energy consumption, memory capacity, size and weight, cost
What is a transistor
A transistor is an on/off switch that allows or prevents current from flowing through
Tell me some trends in microprocessor data
Transistors have increased steadily, single thread performance, frequency, and wattage had increased steadily but have recently plateaued, logical cores were usually pretty much the same, but then have been increasing in the last decade
What does processing speed depend on
The clock frequency (underlying transistor technology), data unit size, type of instructions and their execution order
What does energy consumption/power depend on
cost per instruction (set by word size and underlying technology), number of instructions to complete an operation, instructions per second, set by the clock frequency, instruction set and their implementation.
Nanoprocessors
Silicon based CMOS technology, operation frequency is a few GHz, transistors are super small - based on graphene. Nanomaterials will give unprecedented electrical and optical properties
What are target metrics for embedded systems/things?
Compact - ideally nonintrusive
Energy Efficient - ideally perpetual operation
Speed - fast but doesnt need to be too fast
Other aspects: heat dissipation, reliability, hardware security
What is a microprocessor
An integrated circuit (IC) that contains only a central processing unit (CPU). doesnt have memory or input/output pins. connected to a shared bus where you can connect devices for I/O or memory. Advantage: general purpose and can create your own system with only what you need
What is a microcontroller
An integrated circuit (IC) that integrates a microprocessor, memory (RAM/ROM), I/O pins, as well as peripherals such as serial ports, counters, clocks… Applications are limited by the peripherals in the IC. Advantage: compact and cheap
Graphics processing unit (GPU) vs CPU
GPUs usually designed to accelerate creation of images for a computer display, including texture mapping, image rotation, translation, shading, motion compensation, calculation of inverse DCT (discrete cosine transform), accelerated video decoding. Not really needed for most IoT applications unless multimedia or high performance are required (those are high cost and high energy consumption anyway). CPU is much more optimized for serial processing with few cores.
What is Application Specific Integrated Circuit? (ASIC)
A chip customized to perform a specific task rather than general-purpose applications
What is field programmable gatearray? (FPGA)
A device that can be reconfigured to create different digital circuits. Can create “any” IC (CPU, microcontroller).
Advantages: fully customizable, potentially faster
Disadvantages: cost and energy consumption, sometimes overkill for IoT applications
Arduino vs Pi
Arduino: microcontroller based board, easy to use, limited hardware control
Pi: compact computer on a board, general purpose computer that runs linux, many options
What are the Open System Interconnection model layers?
Application, Presentation, Session, Transport, Network, Data Link, Physical
What type of data is in the Transport layer?
Segments
What type of data is in the Network layer?
Packets
What type of layer is in the Data Link layer?
Frames
What type of data is in the Physical layer?
Bits
Why is data communication important
Sometimes needed for information exchange between sensors, information exchange with a remote sink, or enabling remote control. Sometimes its enough to have local data sensing and data processing to make a desicion
What supports wireless communication
Electromagnetism - near field communication with magnetic induction, radiowaves, microwaves, milimeter waves, terahertz waves, infrared, visible and ultra-violet optical signals
Acoustics - sound, ultra-sound signals
Molecules - ions, hormones, pheromones
What is a transceiver
Transmitter + receiver. The required hardware needed to generate and process wireless signals. Made from signal generators, modulators or mixers, amplifiers, filters
What is an antenna
the element that converts an electrical current in a propagating electromagnetic wave and vice versa
Nano transceivers and nano antennas
Use new materials and leverage new physics to make smaller, non-invasive, non-perceptible transceivers and antennas
What are the transceiver and antenna specifications?
Frequency band of operation, bandwidth, modulations, data-rate, transmission power, antenna gain, noise figure, sensitivity, communication distance/range, out of band emissions
What are the transceiver states
Transmit, receive, idle (ready to receive but not, some functions can be switched off to reduce energy consumption, sleep (significant parts are switched off, cant immediately receive something, recovery time and startup energy can be significant)
Energy consumption in IoT
Minimizing power requirements and energy consumption is a priority
What are the units for Power and Energy?
Power -> Watts
Energy -> Joules (Watts * Second)
Energy = Power * Time
What are the three domains of power/energy consumption in a sensor network
Communication, data processing (computation) and sensing
Tell me about energy consumption in communication
Sensor spends the most energy in data communication (transmission and reception), for short range transmission and reception are approximately the same, low pwoer short range transceivers consume 1-100 mW when ending and receiving - depends on how long theyre receiving. Transceiver circuitry has both active and start up power/energy consumption
Energy consumption vs packet size
as packet size is reduced, energy consumption is dominatedby the startup time on the order of hundreds of microseconds when large amounts of energy are wasted
Tell me about energy consumption during data processing
Energy during data processing is much less than communication. Performing local data processing is important in minimizing the total energy consumption of the system - try to perform as much processing as possible close to the data source.
Power consumption in memory
Flash writing and erasing is the most expensive and crucial - power for ram was negligible
Computation vs Communication cost
Comparing the two has a lot of dependencies. DACs and ADCs are the most energy consuming elements
SHOULD probably put the energy consumption model equation in here
What does the physical layer do? and what are signals and channels
Defines the way in which bits (0s and 1s) are transmitted as signals over a communication channel. A signal is a function that coveys information about the behavior or attributes of some phenomenon. A channel is the medium that carries the signal to be transmitted
What is a baseband signal and its bandwidth
a signal whose range of frequencies expands from 0Hz to a cut off frequency. Used in some wired networking standards (ethernet). TH bandwidth is the highest frequency of the signal
What is a passband signal and its bandwidth
A signal whose range of frequencies is away from 0Hz. Used in radio frequency (RF) communication, digital subscriber line (DSL) systems. The bandwidth is the difference between the upper and lower positive frequencies of the signal
Tell me about digital modulation / demodulation
The data that we want to transmit are digital bits. the wireless propagation is an analog medium, so analog waveforms are sent. the digital modulator at the transmitter converts digital data to analog waveforms. the digital demodulator at the receiver recovers the bits from the analog waveform
What does a digital modulator do
It sits at the transmitter and converts digital data (bits) to analog waveforms. Mechanism where binary sequence is converted to signal transmittable in the physical medium. Baseband is used in wired communication, Passband is used in wireless communication
What does digital demodulator do?
It sits at the receiver and tries to recover bits from the analog waveform.
What are the baseband modulations
Unipolar non-return-to-zero: 1 is positive voltage, 0 is null voltage
Bipolar non-return-to-zero: 1 is positive voltage, 0 is negative voltage
non-return-to-zero inverted: 1 is a transition at signal level, 0 is no transmission
What are the single carrier modulations
Types of passband modulations. these are the properties of a single tone known as carrier AcCos(2pifct) and are changed according to the data being transmitted. The types are:
Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK),
Phase Shift Keying (PSK),
Quadrature Amplitude Modulation
What are ASKs
Amplitude Shift Keying. Binary ASK (BASK): two amplitude levels are used to transmit a binary 1 and binary 0
more amplitude levels can be used to transmit mor symbols
What are FSKs
Frequency Shift Keying. Binary FSK (BFSK): two different frequency tones are used to transmit a binary 1 and binary 0. More frequency tones can be used to transmit more symbols
What are PSKs
Phase Shift keying. The phase of a carrier signal is shifted by a certain phase at each symbol transition. Binary PSK (BPSK): phase is shifted by 0 or 180 degrees. More phases can be used to transmit more signals
What is Quadrature Amplitude Modulation
A combination of amplitude and phase modulations
Tell me about In-phase and quadrature data
precisely varying the phase of a high-frequency carrier sine wave in a hardware circuit according to message signal is difficult. Instead in-phase and quadrature components are introduced to manipulate the signal in baseband before converting at the transmitter or receiver.
What is the Chip Spread Spectrum?
Information is encoded to the changes in carrier frequency across a large bandwidth. Signal occupies a wideband spectrum at all times
What is frequency hopping
When a transmitter hops among frequencies many times per second. It enhances security, has low interference, and a high spectral reuse. Used in military communications and Bluetooth
What are pulse-based modulations and what are the types?
These make use of pulse-shaped signals.
Pulse amplitude modulation (PAM): tow different pulse amplitudes are used to transmit either 0 or 1 - unipolar, bipolar, multi-level variations
Pulse position modulation (PPM): the relative temporal position of a pulse within a slot is used to transmit either 0 or 1 - multilevel ppms are common
What is multiplexing
The act of combining multiple signals over the same physical medium.
Enable one user to transmit more information at the same time => multiplexing
Enable multiple users to share the physical medium without interfering => multiple access
What are some common multiplexing techniques
Frequency division multiplexing (FDM), Time division multiplexing (TDM), and Code division multiplexing (CDM)
What is FDM
Frequency division mutliplexing. Utilizes different bandpass signals at different frequencies over the same medium simultaneously. The separation needs to be larger than twice the baseband signal bandwidth
What is Orthogonal Frequency division mutliplexing
When multiple sub-carriers can be used without any actual band guard, by properly designing their position and shape.
Narrow sub-carriers => very low data rate per carrier
Many parallel sub-bands used simultaneously => highly aggregated data-rate
What is TDM
Time division multiplexing. Different signals take different times or slots to utilize the physical medium. (need tight synchronization)
What is CDM
Code division mutliplexing.
To spread a narrowband signal over a wider frequency band. Multiple signals can occupy the same frequency band without altering each other as long as they use different orthogonal codes. The codes are binary signals who’s bits/chips are shorter than data bits.
To encode the data, the transmitted signal is multiplied by a specific code
To decode the data, the received signal is multiplied by the same code and the result of the product is added over the data bit duration.
Orthogonal Codes: correlation is 0
Tell me about demodulation at the receiver and problems
The receiver looks at the received waveform at tries to match it with the data bit that caused the transmitter to generate the waveform. Need one to one mapping between data and waveform. Best for digital signals, not analog signals
Problems:
Carrier frequency synchronization - frequency can vary between sender and receiver
Carrier phase synchronization - sometimes the receiver needs to know the carrier phase of the transmitted signal
Symbol synchronization: when does the symbol representing a bit start and end
Frame sync: when does a packet start/edn
Biggest problem: Received signal is not the transmitted signal because of the channel
What are some issues with Channel Response?
