Thursday, 5 November 2015

LTE Indoor Distribution Link Budget(1.8G)

Indoor propagation model
Propagation scene divide into NLOS and LOS
For  LOS

For NLOSThe formula for the model is

Among the formula

Distance Loss coefficient, Residence and Office suggest to be 28
 frequencyUnit MHz
The distance between MS and TransmitterUnit  is  m
The coefficient of floor penetration loss
Slow fading margin, it’s value is connected with the requirement of coverage propability and the standard deviation of Indoor slow fading
When f=1850MHzthe formula above is
L=37.3+28log10 (d) + Lf + X
The Example of Indoor Link Budget
For easy to be understanding, for example, A large-scale office building, it is also has UMTS Indoor System, Some UMTS RRU has placed in the weak current wells of the building, and every RRU cover several floors near it. Among it
Look through the system drawing of every floor, the basic power configuration is :The UMTS’s output pilot power of the RRU is 33dbm, when it reaches to the ceiling antenna , the power is around 0dbm,the minimum value is -2dbm. Thus at frequency 2100MHz, the maximum Indoor distribution wired path Loss is around 35db.

Suggest we combine LTE signal to the building’s coverage system, LTE is single channel form.We need to add a 1.8 GHz and 2.1 GHz dual-band combiner, insertion loss about 0.5 dB, the rest of the device can be reused because they are broadband devices.
The location of the combiner suggest to place adjacent to the UMTS RRU. Thus can saves the number of combiners.
Due to the Loss of the feeder in the 1.8 GHz band is smaller than 2100 MHZ band, we should budget the reduce part’s feeder loss of the 1.8 GHz frequency. By sampling inspection, the distance of the the transmission path farside is close to 70 meters, 1.8 GHz spectrum feeder loss compare  2100 MHZ is around 0.5db smaller.  Overall consider two factors new combiner, and feeder loss, the future 1.8GHz frequency FDD - LTE network transmission part cable loss is equal to the existing 2.1 GHz UMTS network , the maximum loss is about 35 db.
 When the signal source of LTE RRU antenna port’s transmission power is 46 dbm, using single channel, with a downlink RSRP > - 100 dbm , the link budget result is as follows:
Spectral bandwidth(MHz)
20.0
Number of  RB
100
Transmission power of Signal Source (dBm)
46
Indoor Cable Loss (dB)
35.0
Maximum TX Power at Antenna Port (dBm)
11.0
Antenna Port RSRP(dBm)
-19.8
Antenna’s jumper wire insection loss (dB)
0.5
Antenna Gain (dBi)
2.0
MS’s RX Antenna Gain (dBi)
0.0
Body Loss(dB)
0.0
Other Loss (dB)
0.0
Require RSRP (dBm)
-100
Shadow Fading Margin (dB)
7.7
MAPL(dB)
74.0  
Coverage Estimate
 
Center Frequency (MHz)
1850
Path Loss at the location of 1m below  Antenna  Port
37.3
Covering Radius(m)
20.5

When the signal source of LTE RRU antenna port’s transmission power is 43 dbm, using single channel, with a downlink RSRP > - 100 dbm , the link budget result is as follows:
Spectral bandwidth(MHz)
20.0
Number of  RB
100
Transmission power of Signal Source (dBm)
43
Indoor Cable Loss (dB)
35.0
Maximum TX Power at Antenna Port (dBm)
8.0
Antenna Port RSRP(dBm)
-22.8
Antenna’s jumper wire insection loss (dB)
0.5
Antenna Gain (dBi)
2.0
MS’s RX Antenna Gain (dBi)
0.0
Body Loss(dB)
0.0
Other Loss (dB)
0.0
Require RSRP (dBm)
-100
Shadow Fading Margin (dB)
7.7
MAPL(dB)
71.0
Coverage Estimate
 
Center Frequency (MHz)
1850
Path Loss at the location of 1m below  Antenna  Port
37.3
Covering Radius(m)
16.0
When the signal source of LTE RRU antenna port’s transmission power is 46 dbm, using double channel, with a downlink RSRP > - 100 dbm , the link budget result is as follows:
Spectral bandwidth(MHz)
20.0
Number of  RB
100
Transmission power of Signal Source (dBm)
46
Indoor Cable Loss (dB)
35.0
Maximum TX Power at Antenna Port (dBm)
11.0
Antenna Port RSRP(dBm)
-16.8
Antenna’s jumper wire insection loss (dB)
0.5
Antenna Gain (dBi)
2.0
MS’s RX Antenna Gain (dBi)
0.0
Body Loss(dB)
0.0
Other Loss (dB)
0.0
Require RSRP (dBm)
-100
Shadow Fading Margin (dB)
7.7
MAPL(dB)
77.0
Coverage Estimate
 
Center Frequency (MHz)
1850
Path Loss at the location of 1m below  Antenna  Port
37.3
Covering Radius(m)
26.2
When the signal source of LTE RRU antenna port’s transmission power is 43 dbm, using double channel, with a downlink RSRP > - 100 dbm , the link budget result is as follows
Spectral bandwidth(MHz)
20.0
Number of  RB
100
Transmission power of Signal Source (dBm)
43
Indoor Cable Loss (dB)
35.0
Maximum TX Power at Antenna Port (dBm)
8.0
Antenna Port RSRP(dBm)
-19.8
Antenna’s jumper wire insection loss (dB)
0.5
Antenna Gain (dBi)
2.0
MS’s RX Antenna Gain (dBi)
0.0
Body Loss(dB)
0.0
Other Loss (dB)
0.0
Require RSRP (dBm)
-100
Shadow Fading Margin (dB)
7.7
MAPL(dB)
74.0
Coverage Estimate
 
Center Frequency (MHz)
1850
Path Loss at the location of 1m below  Antenna  Port
37.3
Covering Radius(m)
20.5

The above NLOS link budget result’s condition is has no obvious block .It  can evaluate whether the layout of the indoor antenna can meet the requirements.

Budi Prasetyo

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