User Manual

DELTANODE FIBER DAS MANUAL
©DeltaNode Solutions 2012
29
Revision 12-03
If you are using radiating cables, then calculate with the loss over the maximum length of radiating cable
you need to support and find the Remote Unit that has the highest total loss from the User Equipment
(mobile station) to the Base Station end.
3.2.1 Downlink
For the downlink you can usually just use the output power of the remote unit and then calculate your
link budget. Remember that if you have several carriers, you need to calculate your link budget with this
in account. For each new carrier you add, the power per carrier goes down as the power on the Remote
Unit is divided onto all the (active) downlink carriers.
To calculate the “per carrier” output power here is a general table of modifiers that are applied to the
output power of the remote unit:
1
2
3
4
5
6
7
8
9
10
0
-3,0
-4,8
-6,0
-7,0
-7,8
-8,5
-9,0
-9,5
-10,0
Table 12: Per carrier loss
As you can see there is a correlation that whenever the number of carriers double the per carrier power
is lowered with another 3 dB. Thus the formula for any number of carriers will be:


= 

10 

(

)
The output power for each type of remote unit and frequency band can be found in the data sheets in
chapter 2.2 Remote Unit where the relevant parameters for each remote system are discussed.
Remember to use the per carrier power in your link budget and not the composite because if as you
keep adding carriers to the system the power per carier will be lower. If you are planning on adding
additional carriers in the future you should plan your system for the maximum forseable number of
carriers.
Following is an example of a link budget. This link budget is also included in the DAS Calculator package.
If you do not have this package contact DeltaNode Solutions to receive a copy.
3.2.2 Uplink
Uplink calculations generally rely on having the noise figure at hand before so that the desensitization of
the base station can be calculated. However since the noise figure is dependent on the link budget, we
should be able to calculate a crude link budget at first, get our gain straight and then when we are done
we should be able to calculate the proper noise load using the DAS Calculator Tool (will be handled in
chapter 6). Therefore we will assume a standard noise figure for now, properly adjusted the DeltaNode
Fiber-DAS solution has a NF of less than 3 dB per uplink.
A reasonable assumption for the NF is around 3 dB, if we should get a better or worse NF later when the
DAS Calculator is employed we will just go back and correct the link budgets for this.
System Uplink Net Gain
The net gain is the total gain in the uplink from the Remote Unit port to the input port on the base
station. This chain looks something like this: