1. Computer Review
Expansion Cards

2. What Are Expansion Cards
Secondary boards attached to the Motherboard that allow us to add functionality to our computer
May add peripheral ports, completely new abilities or expand upon abilities that the computer already possess
Allows us to upgrade one specific functionality of the computer without replace the whole thing
Popular expansion cards include
Video Cards
Sound Cards
TV Tuners
USB Host Cards
Network Interface Cards

3. PCI expansion cards Stands for Peripheral Component Interconnect
Has a notch towards the back to make sure that the card is being inserted correctly
Supports plug and play functionality, which means that installed devices are detected and configured automatically
Can run at 33 megahertz with a transfer speed of 133 megabytes per second, or at 55 MHz and 266 MB/s

4. PCI-X expansion cards Stands for PCI extended
Has a notch towards the back to make sure that the card is being inserted correctly
Uses a 64-bit interface to achieve a faster data rate, up to 1.06 GB/s
Is backwards compatible with standard PCI slots, though when in PCI slots, they are throttled down to PCI speeds
Typically seen in servers for networking cards

5. PCIe expansion cards Stands for PCI express
Created to replace PCI and PCI-X
Data rates depend both on the protocol version and the number of transmission lanes. PCIe 4.0 x1 supports 2 GB/s, and PCIe 4.0 x16 offers 32GB/s
Can run alongside legacy PCI technology, so you can see motherboards with both PCI and PCIe slots
PCIe 4.0 was officially formalized June 8th, 2017, and PCIe 5.0 has been preliminarily announce with standardization expected in 2019

6. PCIe X1
PCIe cards are defined by the number of transmission lanes that are used to transfer data
PCIe x1 provides 1 lane of transmission while PCIe x16 provides 16
PCIe defines x1, x2, x4, x8, x16, and x32
The most popular types are PCIe x1 and x16
PCIe x1 are usually used for network cards, USB cards and sound cards

7. PCIe X16 PCIe x16 cards are usually used for dedicated video cards
PCIe provides power, but for higher end video cards, additional power from the PSU must be connected
Keyed notch near the front of the card, and a hook at the back of the card to ensure proper seating

8. Recognizing PCI slots
It helps to be able to recognize PCI slots and cards visually, but card and motherboard documentation should provide answers if it is unclear what each port is
PCI have their keying tab near the end, PCIe have theirs near the front
PCIe x16 slots will have the locking tab as well

9. ESD Protection
Like most computer hardware, expansion cards are susceptible to damage from electrostatic discharge
Best practices include starting by grounding yourself by setting the computer on an ESD mat and connecting yourself to the mat by an ESD wrist strap
Keeping the component in an anti-static bag will also help to protect the card

10. Preparing the Case
Use a screwdriver to the remove an expansion slot cover corresponding to the PCI slot being used
Keep the screw nearby and store the cover in a safe place. The screw will be used to secure the expansion card, and the slot should be reinstalled if the component is removed. This helps with cooling by providing a closed system for air flow

11. Installing the Expansion Card to the Motherboard
Firmly press the expansion card into the slot. If the card won’t go in, double check that the slot and the connection tab are compatible
Do not rock the card too much or use excessive force to install the card. This could damage the component
Do not press too lightly either. The expansion card must go all the way in, otherwise the card won’t be seated properly, and won’t work. In the worst case scenarios, the card could be close enough to the connectors that the electricity can bridge the gap, and then the connection will short out and damage the card

12. Finishing and Setting Up
Use the screw that was removed to secure the expansion card, and make sure it doesn’t get unseated during operation
Install necessary drivers. This can be done by using windows update to select an appropriate driver, installing drivers from a manufacturer’s CD or by downloading the latest drivers from the manufacturer’s website
Windows Update will give you an up-to-date driver, but since it is not made by the people who made the expansion card it may not enable all of the devices features
The manufacturer’s CD will have appropriate, but perhaps old, drivers
The best and most up-to-date drivers will come from the manufacturer’s website

13. Introduction to Networking
Wireless Radio Frequencies

14. Wireless Radio Frequency as a Medium
In addition to wiring networks using copper wire or fiber optic cable, you can also use radio waves as the medium for a computer network, for a wireless network
This is considered an unbounded medium because unlike fiber optic or UTP cables the signal is not encased in a sheath
This means that the signals are able to move through spaces easier than cabled media, and that it is less secure

15. Available Frequencies
Wireless networks use specific radio frequency ranges that are regulated by the Federal Communications Commission (FCC). These are classified as Industrial Scientific and Medical (ISM) frequencies
The FCC has reserved these five frequency ranges to be used for wireless networks GHz, 5.15GHz, 5.25 GHz, GHz, and 5.8 GHz
The earliest Wi-fi standards used the 2.4 GHz band exclusively, but this was problematic because many other devices also used that same set of frequencies
With 2.4 GHz, the wireless network would be configured properly and running reliably, but if someone made a phone call of turned on a wireless microphone, used a cordless phone or turned on a baby monitor, network communications would be disrupted

16. 2.4 GHz
The reason that the 2.4 GHz band is congested is that there are only a limited number of channels available (11 channels)
To make matters worse, adjacent channels in this range actually overlap with each other considerably. This meant that if two devices in this frequency range were configured to use two adjacent channels (such as 5 and 6), they could interfere with each other even though they were on different channels
Unfortunately, there are actually only a handful of non-overlapping channels in the 2.4 GHz range - 1, 6, and 11
Since every device has to use one of these three channels, there was marked interference between devices, which could be very difficult to troubleshoot. It would only manifest itself while both devices were on at the same time. If the offending device were to be powered off, you would have no way to track it down

17. 2.4 GHz Channel Map

18. 5 GHz
Today, we have migrated away from the 2.4 GHz band to the 5 GHz band. The 5 GHz band provides 23 non-overlapping radio channels and is subject to less radio interference than the 2.4 GHz band
While it is, in general, better to use than the 2.4 GHz band, there are some issues
2.4 GHz tends to cover a larger area
2.4 GHz can penetrate walls and other obstacles better than 5 GHz
Although there are more channels, 5 GHz can still become congested if enough devices connect to it
In general, use 5 GHz when you are concerned about speed and performance and your device is capable of connecting to it, and use 2.4 GHz if your device either can’t connect to 5 GHz, needs a stable connection further from the router/access point, or uses wifi sporadically or for small amounts of data

19. Spread Spectrum Signal Transmission Technique
The IEEE standards specify ways to increase bandwidth and reduce interference when transferring data using radio waves
One of the primary ways this is done is using the spread spectrum signal transmission technique, sometimes called SSS
Using SSS, the access point on the wifi network varies the frequency used during transmission, so data is spread across a wide band of frequencies
An FM or AM radio is an example of a device without this technique. With a radio, the information is being transmitted on just a single frequency (or two frequencies in the case of FM stereo)
If your favorite station is that's the frequency you have to turn your radio to. If you turn it to you won't get anything, if you turn it to you won't get anything either. That's because the information is being sent on just two frequencies

20. Benefits of SSS
Using spread spectrum technology, wifi data is transmitted and received on multiple channels at the same time
For this to work, the transmitter and the receiver have to be in tune. They have to know which frequencies to use and how the data is going to be formatted as it comes across
This strategy provides two major benefits
It provides greater bandwidth than using a single, narrow frequency. If you're transmitting on multiple frequencies at the same time, you can send more data at once
It also eliminates communication failures due to interference on a single frequency. Using spread spectrum, we spread the data across multiple frequencies, so if there is interference on one of them we can compensate by using the other frequencies to send data.

21. Frequency Hopping Spread Spectrum
There are two different ways that SSS is implemented in a wireless computer network
The first is Frequency Hopping Spread Spectrum (FHSS)
With FHSS, the transmitter only uses one frequency at a time; however, it changes the frequency that it uses several times each second
The transmitter will begin transmitting on one frequency for just a few milliseconds and then it'll hop and start using a different frequency, and then after a few seconds it'll hop to the next frequency and start transmitting on it.
The transmitter and the receiver are in sync. The receiver follows the frequency that is going to be used so that the transmission continues to work correctly

22. Direct Sequence Spread Spectrum
The other option is Direct Sequence Spread Spectrum (DSSS)
DSSS is similar to frequency hopping, but slightly different
With DSSS, the transmitter takes a piece of information, divides it up into chunks, and then spreads the chunks across all the frequencies that it's using and sends them all at once
This really increases the bandwidth between the transmitter and the receiver compared to FHSS. Although FHSS uses multiple frequencies, only one is used at a time. By using multiple frequencies at the same time, DSSS allows for more data to be sent at one time
Spread spectrum technology was used in early wireless network standards, such as b and g, but later networking standard, such as n use a different technique called Orthogonal Frequency-Division Multiplexing (OFDM)

23. Orthogonal Frequency-Division Multiplexing
OFDM was designed specifically to address issues encountered on wireless networks where multiple, reflected copies of the same radio signal is received by a receiver
The reflections are created when the radio signal bounces off of environmental obstacles, such as walls or even buildings. Because the bounced signal is a reflection, it is identical to the original signal, but arrives slightly later than the original signal because the path it had to travel was slightly longer. The reflected signal is sometimes called a ghost signal
These ghost signals can severely disrupt wireless network communications, and transmitting large amounts of data over longer distances causes the disruption caused by ghosting to be worse

24. OFDM Benefits
OFDM is designed to mitigate disruptions caused by ghosting
It does this by breaking the data transmission into very small data streams, much like spread spectrum does
However, OFDM modulates adjacent radio signals orthogonally, which dramatically reduces the size of the frequency buffer between channels
This allows a very large number of very small data streams to be created within the same frequency range
The small size of the data streams reduces the negative effects of signal reflections, and helps the network ignore the echoed signals