Day 1: Signal Design Flashcards by Gray Nguyen

What is the process of converting analog signals to digital signals?

Sampling

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Why do we convert digital to analog before transmitting?

It proprogates through space better

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Identify

The method of putting information onto a carrier signal by changing one or more properties of the wave in a pre-determined pattern to represent data

Modulation

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When we modulate, what are we changing?

Frequency, amplitude, and/or phase

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Identify

A method of encoding digital information (bits) onto an analog carrier wave for transmission over media that does not support direct digital transmission

Digital Modulation

Most common is shift-keying

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Presents digital data as variations in the amplitude of a carrier wave

Shift Keying

Amplitude Shift Keying

It is also relatively inexpensive.

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Shifts the output frequency between predetermined waves

Shift Keying

Frequency Shift Keying

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Changes the phase of a carrier wave

Phase Shift Keying

BPSK and QPSK most common mod scheme due to better efficiency; idea for video

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Identify

Stands for In-phase and Quadrature
It represents two 90 degrees perpendicular components to each other

Constellation Diagrams

I/Q

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Graphical representation showing possible symbol locations in I/Q space

Constellation Diagrams

Constellation Plots

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What do constellation diagrams represent?

Amplitude (I) and phase (Q) of a signal

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Identify

Uses 2 phase shifts 180 degrees apart

Modulation Scheme

BPSK

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Less sensitive to phase noise than other types

Modulation Scheme

BPSK

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Used when lower data rates are required or more robustness is required

Modulation Scheme

BPSK

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2 bits per symbol

Modulation Scheme

QPSK

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More susceptible to nosie than BPSK and QPSK

Modulation Scheme

8PSK

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Less BW required than BPSK and QPSK

Modulation Scheme

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Often used for digital video

Modulation Scheme

QAM

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Combination of modulating amplitude and phase

Modulation Scheme

QAM

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Expressed as a percentage (%) deviation of Rx’d symbol vs Reference Point

Error Vector Magnitude

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Expressed as a percentage (%), deviation of Rx’d symbol from desired phase angle

Phase Shift Error (PSE)

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The range of frequencies where the majority of the signal’s power resides

Occupied Bandwidth

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The bandwidth actually used for transmitting data

Effective Bandwidth

Always narrower than occupied BW due to guard intervals and other factors (ex. roll off factor)

How is effective bandwidth is closely related to symbol rate?

The faster symbols are transmitted (higher symbol rate), the more bandwidth is needed

# Identify Intentional periods (time) where signals do not transmit to prevent interfering with themselves

Guard Intervals

# Identify Unoccupied spaces between signals to prevent interfering with one another

Guard Bands

# Identify The difference in frequency between the effective and occupied bandwidth

Roll-off factor

# Identify Speed at which **raw data** is transmitted

Data rate

# Identify Overall speed of **all bits** being transmitted, including **raw data and any additional** bits **like error correction**

Total Bit Rate

Rate at which symbols (which can represent multiple bits) are transmitted (changes)

Symbol Rate

# Identify Adds "gain" to the signal (computational/coding)

Forward Error Correction (FEC)

# Identify Added in the MODEM (prior to Tx)

Forward Error Correction (FEC)

# Identify The ability to detect the presence of errors caused by noise or other impairments during transmission between the transmitter to the receiver | FEC

Error detection

# Identify The additional ability to reconstruct the original, error-free data | FEC

Error correction

# Identify Non-data bit added to data bit stream that enables receiver to detect errors or to detect and correct errors | FEC

Parity bit

# Identify The actual information (1s, 0s) you are attempting to send | FEC

Data bits

# Identify The entire series of "ones" or "zeros" (data and parity) | FEC

Bit stream

# Identify A radio technology allowing **one-way communication** from a transmitter to a receiver | Communication Protocols

Simplex

# Identify Operation mode of a radio communication system in which each end can **transmit and receive, but not simultaneously** | Communication Protocols

Half-duplex RF systems ## Footnote Ex. walkie-talkie, wireless keyboard, mouse

# Identify Radio system in which each end can **transmit and receive simultaneously** | Communication Protocols

Full-duplex RFsystem

# Identify Combining multiple signals into ONE signal (Analog or Digital)

Multiplexing

# Identify The separation of combined signals

De-multiplexing

What are the methods of multiplexing?

* Frequency Division MUX (FDM) * Time Division MUX (TDM) * Code Division MUX (CDM)

# Identify The process of **two or more signals** physically **taking turns on a channel (frequency)** ## Footnote This enables **efficient use of** the available **bandwidth**

Time Division Multiplexing (TDM)

# Identify **Assigns non-overlapping frequency ranges to different signals** or to each "user" of a medium

Frequency Division MUX (FDM)

A data signal is **sent** over a range of frequencies in an assigned frequency spectrum **using a pseudo-random spreading code**

Code Division MUX (CDM) ## Footnote Ex. cellular network

Multiple access differs from multiplexing because it occurs ____________ transmission.

After

What are the types of multiple access?

* Frequency Division Multiple Access (FDMA) * Time Division Multiple Access (TDMA) * Code Division Multiple Access (CDMA)

# Identify Users share the satellite simultaneously, but each user transmit at a single frequency

Frequency Division Multiple Access (FDMA)

# List Frequency Division Multiple Access (FDMA) Advantages

* Simplicity * Proven and reliable

# List Frequency Division Multiple Access (FDMA) Disadvantages

* Needs more BW as you add users * In-flexible, not easy to reconfigure

# Identify Users share a single RF channel without interference by allocating different time slots to each user

Time Division Multiple Access (TDMA)

Time Division Multiple Access (TDMA) Advantage

Efficient use of BW (user gets full BW during their time slot)

Time Division Multiple Access (TDMA) Disadvantages

* Needs to account for Tx delay for differing Earth Stations * Large Earth Segment investment (transmit equip/controllers) * Need for very precise time standards * Limited time slots

Tx technique that employs a scheme that **codes every digital packet it sends with a unique key** to allow users to be multiplexed over the **same frequency** channel

Code Division Multiple Access (CDMA)

# List Code Division Multiple Access (CDMA) Advantages

* More resistant to jamming and interference than FDMA and TDMA * Resistant to interception

Code Division Multiple Access (CDMA) Disadvantage

Equipment cost is much higher, along with the larger BW that is required