# [Question] WCDMA Bandwidth

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#### currentmirror2000

##### Member level 4
channel spacing wcdma

hi all,

in WCDMA, the chip rate is 3.84MHz and the channel spacing is 5MHz

which one i should choose to use as bandwidth in order to calculate the noise figure? 3.84MHz or 5MHz?

#### vfone

channel bandwidth, dect

3.84MHz

### currentmirror2000

Points: 2
V
Points: 2

#### currentmirror2000

##### Member level 4
wcdma bandwidth chip rate

vfone said:

thank you, but why? how about GSM900, GSM1800 and DECT?

for GSM900/1800 and DECT, they have data rate and channel spacing, which one should be used as bandwidth? and why?

#### vfone

wcdma bandwith

The noise figure is measured by integrating noise power across the full-received signal bandwidth of 3.84 MHz using a matched filter.
3.84MHz is the channel Bandwidth and 5MHz is the channel spacing.
Receiver sensitivity according to 3GPP spec is measured in dBm/3.84MHz.
In GSM the channel Bandwidth is 180kHz and channel spacing is 200kHz.

### currentmirror2000

Points: 2
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Points: 2

#### currentmirror2000

##### Member level 4
wcdma channel bandwidth 3.84mhz

vfone said:
The noise figure is measured by integrating noise power across the full-received signal bandwidth of 3.84 MHz using a matched filter.
3.84MHz is the channel Bandwidth and 5MHz is the channel spacing.
Receiver sensitivity according to 3GPP spec is measured in dBm/3.84MHz.
In GSM the channel Bandwidth is 180kHz and channel spacing is 200kHz.

can i use the channel spacing as bandwidth to calculate noise figure in GSM if the channel bandwidth is not given.

btw, how about DECT? similar as GSM?

thanks!

#### vfone

gsm wcdma bandwidth compare

There are 0.5dB difference in Noise Floor between 180kHz and 200KHz BW.
For a Sensitivity measurement would be no big difference between these two BW because anyway you need another ~10dB margin to reduce the Noise Floor significantly below the required sensitivity level.

GSM required Noise Floor = -102dBm – 10LOG(180000) – 10 = -164.5dBm/Hz

DECT has the same story.

### currentmirror2000

Points: 2

#### currentmirror2000

##### Member level 4
wcdma gsm noise floor

so you mean in GSM and DECT we can use the channel spacing as the bandwidth to calculate the noise figure approximately and in WCDMA we have to use the chip rate instead of the channel spacing as the bandwidth to calculate the noise figure. am i right?

in fact, i also have the data rate for WCDMA (+chip rate), GSM and DECT, what is this? why we cannot use the data rate as the bandwidth?

#### vfone

how is wcdma bandwidth calculated ?

For GSM/DECT you can use approximately the channel spacing for NF measurement, but I don’t understand why you don’t use the channel bandwidth, now when you know what is about.
In WCDMA (because is spread spectrum) the chip rate dictate the channel BW, and not the data rate.

### currentmirror2000

Points: 2

#### currentmirror2000

##### Member level 4
channel bandwidth of gsm

vfone said:
For GSM/DECT you can use approximately the channel spacing for NF measurement, but I don’t understand why you don’t use the channel bandwidth, now when you know what is about.
In WCDMA (because is spread spectrum) the chip rate dictate the channel BW, and not the data rate.

thank you very very much for your kind help!!!

to answer your question, it is simply because the channel bandwith is not given in the question/spec... only channle spacing and data rate are given for each case, in WCDMA chip rate is also given. so i was confused which to use

i think we can close this topic, thank you very much again

V
Points: 2