The MAC layer generates a new transport block every 10-ms (or multiple of blocks.)
A set of simultaneous transport blocks is the transport block set.
The transmission time interval (TTI) is the duration of each transport block set.
This can be 10, 20, 40, 80 ms.
TTI does not tell you data size. It tells you how often the [...]
The transport channel is a concept applied to the interface between the physical layer and the MAC layer.
All transport channels are unidirectional.
The physical layer operates in 10-ms time slices in the connected mode (HSDPA case: 2-ms).
The data is sent using transport blocks.
The spreading procedure in the UTRAN consists of two separate operations:
1. channelization
2. scrambling
Channelization uses orthogonal codes. Scrambling uses PN (Pseudo-Noise) codes.
Downlink:
channelization is for differentiating users.
scrambling is for differentiating base station.
Uplink:
channelization is for differentiating channels per UE
scrambling is for differentiating users.
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Orthogonality requires time synchronous properties. Thus, it cannot separate different uplink users as all UEs are [...]
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
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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: 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 is [...]
