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Short Discussion Replies

100-150 word response for each one

1) The most interesting ammendament for me so far is the 802.11h-2003, this is when radar came into the spectrum and considerations were taken to either avoid detection or to avoid interfering with a transmit ion. The DFS will choose channels with low interference levels and it was part of the mandate by Unlicensed National Information Infrastructure (U-NII).

So we know that radars can be gigantic or very small, for example I use a radar in my boat not only for weather, but also to locate fish, my brother uses a radar to find birds, I am sure the military uses radars to find almost anything.

So I am trying to look what are the cons for radar usage and interference that could affect the radar, one concern I was discussing with my brother was how a dense object can throw off the reading from the radar and he mentioned dense forest could do the same, I am thinking its mostly related to the frequency not been strong enough.

Anyone else uses radars and experience with frequency interference?

2)

Roaming charges are when your mobile connection moves from one area covered by a mobile area (called a cell) to another mobile area covered by a different cell. The cell provider’s carrier is continually monitoring the strength of your received signal using a Signal to Nose Ratio (SNR). When the SNR becomes unacceptably weak, sophisticated algorithms attempt to determine which cell will provider you better service. Roaming charges apply because you are being charged extra for algorithms and because the antenna you switch to during roaming may be owned by a carrier other than your own.

What do you think would be an unacceptable SNR value? In other words, what SNR value would contribute to poor bandwidth/data rate?

3)

Chipping is a way of encoding data to aid in protecting it from interference and data corruption thru processing gain. Chipping begins when a system converts 1 bit of data into a series of bits known as chipping. Boolean XOR is used on the data along with pseudorandom number (PN). The sequencing spreads these bits over wider frequency and on the receiving end it is despread. If the data becomes corrupted prior to reaching the recieving end then the object can still interept the data by going thru the chips that it recieved correctly.

4) Correct! You can have brains,style and beauty too! Heddy Lamarr and a co-inventor used their musical talents to propose sending a signal (containing Latitude & Longitude position information) over the air, but to change the frequency of signal for each new position sent. They based their concept on an old-fashioned piano roll. Prior to recorded music you could purchase a roll of paper which would have hundreds of perforated dots/holes. The roll would be attached to a piano and as it scrolled the punctured dots would drive the piano keys~ which would then play a familiar tune. This works very similar to a music box, but the music box typically contains a metal cylinder with many pins on it. The pins pluck at teeth/comb as the cylinder rotates. The roll of a piano scroll could be very long while the cylinder of a music box would only revolve once and then repeat (i.e. 360o ) the sequence.

Prior to WWII you could transmit LAT/LONG information using amplitude modulation (AM) and carrier frequency. For instance, a 680 KHz carrier signal would be modulated by the position information. If the enemy knew you were broadcasting on 680 KHz they could jam your signal with their more powerful 680 KHz signal. In other words, the enemies signal would interfere with your RF signal to the extent that your receiver would be unable to de-modulate the Positon information.

Lamarr’s proposal was to change the frequency of every transmitted LAT/LONG position in such a way that enemy could not completely jam your signal. For example, let’s try to transmit seven (7) undetectable positions over the air using various frequencies.

POS # 1 transmit (Tx) via 530 KHz

POS # 2 via 1000 KHz

POS # 3 via 1700 KHz

POS # 4 via 1600 KHz

POS # 5 via 680 KHz

POS # 6 via 1800 KHz

POS # 7 via 900 KHz

To receive all seven (7) Positions correctly, the receiver needs to be aware of not only the carrier frequency, but also the order each of the seven (7) transmit frequencies. If the enemy set their jammer to 680 KHz only POS #5 may be corrupted, but the other six (6) positions would be received intact!

The switching of frequencies for each transmitted piece of information (in our case the information is LAT/LONG position) to avoid interference is called Frequency Hopping.

What might a disadvantage of using Frequency Hopping in either wartime for wireless network communications?

5) I wanted to talk a little about pg. 206-207 and how this might relate to an earlier topic or a clearer understanding of this to help me. 3.6 GHz Band – This amendment specified the use of the frequency range of 3.65 GHz to 3.7 GHz (Coleman & Westcott). Was this 3.6 GHz Band set because it would interfere with satellites and the government only wants to be able to use these frequencies?

4.9 GHz Band – The 802.11-2012 standard defines the frequency range of 4.94 GHz to 4.99 GHz in the United States for public safety organizations to use for the protection of life, health, or property. We have devices that support this so when we go to other places we can’t use it and is this why we go into roaming? Sorry I am confused somewhat and this is what I am understanding of this.

Future Wi-Fi Frequencies – The 2.4 GHz ISM band has remained the dominant license-free range of frequencies, known as a frequency band, that has been used for Wi-Fi communications since 1997. This was picked up and changed to 5 GHz because 2.4 GHz became overcrowded and can have more channels.

60 GHz New PHY and MAC layer enhancements have the potential of accomplishing speeds of up to 7 Gbps. Wow this was interesting and might be good for short range areas since it has difficulty going through walls. Not sure if this would be a bad idea if offices hooked up to LANs and maybe had their open Lounge areas with these capabilities. Seeing that this will be known as the WiGig brand was interesting to see that there is going to be something else out there besides the name Wi-Fi.

6) This part was very interesting because is something we use on a regular basis and we might not understand the differences, I was ignorant to this technology even if I use it and support it on a daily basis, not so much how it works, but the advancement over the last few years..


With WPAN we can go back to 1939 when the first remote control was used for the Mistery Control!, a battery device to control a console radio using battery and infrared technology, but the most common one would be the red light we see on our TV remotes. It was used the first time in the 1950 by Zenith and it was call the lazy bones, I can understand why.

If we move forward to today, I don’t believe I have a remote anymore, I control my TV with Bluetooth technology and I believe infrared will eventually dissapear in the form of a remote control.

Do you use bluetooth to control your TV, do you still use your remote? What do you think of the changes?

7) Radios communicate with each other in different ways. With a half duplex, both radios in the communication can send and receive messages, but only one at a time. Examples of this type of communication would be a walkie-talkie. The other type which is full duplex is when both radios can communicate at the same time, like during a phone call when both parties can talk at the same time and be heard clearly. Computers usually use the half duplex type of communication rather than the full duplex.

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