# Wcdma

#### EngIntoHW

Joined Apr 24, 2010
143
Hi,

I'm currently studying that topic and would like to ask numerous questions please.

The chip rate of a WCDMA system is 3.84 Mcps.
Thus, the respective modulation symbol rates vary from 960K symbols/s to 15K symbols/k.
1. The modulation symbol rates refers to the data signal, before it's being spread?
Otherwise, I don't understand how they reached the 960K and 15K figures.

The frame length is 10ms and each frame is divided into 15 slots (2560 chip/slot at the chip rate 3.84 Mcps).
For separating channels from the same source, orthogonal variable spreading factor (OVSF) channelization codes are used.
In the downlink, Gold codes with a 10-ms period (38400 chips at 3.84 Mcps) are used to separate different cells, with the actual code itself length 2^18 - 1 chips.
2. Each channel takes 38400 chips out of the (2^18 - 1) exist in a Gold code, and each of the 15 slots of this frame takes 38400/15 chips out of these 38400 chips?
Did I get it right?

The carrier spacing has a raster of 200KHz, and can vary from 4.2 to 5.4 MHz. Figure 6.1 shows an example for the operator bandwidth of 15MHz within three cell layers.
3. I don't manage to understand that part.
What is operator, in terms of channel, cell, cluster?
What do they mean by three cell layers?

Thank you.

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#### EngIntoHW

Joined Apr 24, 2010
143
Thank you very much Bertus.

The PDF link is so wonderful.

I'll be reading it and will come back with any questions that I might have (Hopefully it's ok).

#### EngIntoHW

Joined Apr 24, 2010
143

1.
In WDCMA, channels are separated by codes, and not by frequency, as each channel uses almost the whole RF band (3.84MHz out of 5MHz).
The RF band of WDCMA channel is 5MHz, and each channel uses a bandwidth of 3.84MHz, right?

2.
If each channel has a unique code, does it mean that each cell phone needs to know both it's own code and the code of the channel it's using?

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