How can capacity affect the noise figure

[Femto_Engineer]

Hi,

I am reading the book ' Understanding UMTS radio Network: Modelling, Planning and Automated Optimization'

On page 224, it states:

'The typical range of base station receiver noise figure varies from 2.5 to 4 dB for a macro or wide range base station. For micro or pico base stations (medium range or local area BS), the noise figure could be higher (like for a UE), since the capacity would be limiting factor rather than the coverage range of the cell'.

My question is, how can capacity of a cell affect the noise figure of BS receiver?

regards

[billaugust]

Hi,

First of all, the noise figure is a SNR degradation measure between the input and output of one RF component. Thus better/more expansive RF gains smaller NF. Thus it is not decided by capacity or coverage at all.

Instead, the NF can affect the network capacity and coverage due to its relation with system SNR.

Coverage:
If we take a look at sensitivity S of voice service in GSM (C/I 9db).
N = N0 + NF = -121dbm + 4db = -117dbm
S = N + C/I = -117 + 8 = -108dbm
As we know, the tx power of a single UE is very limited, thus the NF of the BS receiver need to be small. In an indoor\micro environment, since the UE is quite close to the BS, that is not a big issue.

Capacity,
As the NF will affect SNR directly. It is actually also very important to capacity as well. For a voice dominant scenario, it may not be so important as data rates is fixed. However, for PS services, especially for UMTS HSPA+ or LTE, higher SNR means higher data rates thus higher capacity.

[Femto_Engineer]

So in other words, for micro or pico cells, where coverage is not a problem as compared to capacity, the receivers can have a little bit higher NF as compared to Macro BS receivers. right?

[firstmaxim]

Hi,

I am reading the book ' Understanding UMTS radio Network: Modelling, Planning and Automated Optimization'

On page 224, it states:

'The typical range of base station receiver noise figure varies from 2.5 to 4 dB for a macro or wide range base station. For micro or pico base stations (medium range or local area BS), the noise figure could be higher (like for a UE), since the capacity would be limiting factor rather than the coverage range of the cell'.

My question is, how can capacity of a cell affect the noise figure of BS receiver?

regards

Since the total noise at receiver is NF + 10logkT. If NF is small, noise reduces=> capacity increases.

[s52d]

Hi,

I am reading the book ' Understanding UMTS radio Network: Modelling, Planning and Automated Optimization'

On page 224, it states:

'The typical range of base station receiver noise figure varies from 2.5 to 4 dB for a macro or wide range base station. For micro or pico base stations (medium range or local area BS), the noise figure could be higher (like for a UE), since the capacity would be limiting factor rather than the coverage range of the cell'.

My question is, how can capacity of a cell affect the noise figure of BS receiver?

regards

Hi!

As Noise Figure is HW property, it is not influenced by capacity itself.
How I read it is: There is no need to get down to last dB with NF when designing pico cell,
as we probably do not care on last dB of coverege.

By definiton, pico/micro serves small area to add capacity, while coverage is done
by macro layer.
JOKE: As every TEMS engineers knows, nobody uses phones indoors,.

Thus, we can match poor terminal performance by having:
1. - higer NF and no diversity on uplink
2. - lower TX power on downlink
As a side effect: micro/pico are cheaper with lower power consumption compared to macto BS.

BR
s52d

p.s. It is good book you read. Too good to be read in .pdf, so I bought one.