wirelessoom
WCDMA has 3.84 Mcps (chip per second).
One 10-ms radio frame is divided into 15 slots.
1000 ms has 3.84 10^6 chips
10 ms has 3.84 10^4 chips
15 slots have 3.84 10^4 chips
1 slot has 38400/15 = 2560 chips
downlink spreading factor from 4 to 256
uplink spreading factor from 4 to 512
With spreading factor 4,
1 slot has 2560/4 = [...]
1. Binary XOR operation allows the original symbol reconstruction.
Do spread:
symbol sequence X (XOR) some code Y => some signal Z
Do despread:
some signal Z (XOR) some code Y => symbol sequence X
—————
2. Let’s assume there are 10 users who want to send its data X1, X2, …, X10.
Let’s assume they have their own codes Y1, Y2, [...]
For high data rate, simply send fast.
Which one is high data rate ? 2 bits for 1 second vs. 2 bits for 6 seconds.
So, if you want a high data rate, your sending rate should be fast.
Time and frequency relationship is reverse. Short time duration means wide bandwidth.
That’s why wide bandwidth is need for faster [...]
First, think about the definition of spreading factor (SF): the number of chips for each symbol.
Second, remember that a chip duration is fixed.
Third, what is symbol? Each symbol can represent some amount of bits. e.g., QPSK, each symbol represents 2 bits.
SF: 2 SF vs. 512 SF
Time: 2*delta vs. 512*delta
Data: 1 symbol vs. 1 symbol
where delta [...]
