Pa Pb in LTE and its impact on User Throughput
Downlink signals are made up of many different components. For example, Reference Signal, PDCCH, PDSCH etc.
The RS power and the SCH powers are key RF optimization parameters that influences the
cell coverage. It is set according to the cell size. The higher the setting, the larger the cell coverage on the downlink, but leaves smaller power headroom available for other downlink signals and channels.
The relation between RS power and power on PDSCH symbols (includes type A and type B
symbols), has to be defined and reported to the UE, in order for the UE to demodulate 16QAM
and 64QAM.1 PDSCH type A symbols has only PDSCH RE’s, PDSCH type B symbols has mixed
RS and PDSCH REs. Parameter PA sets the power of PDSCH type A RE relative to cell‐specific
RS, PB sets the power relation between PDSCH type B RE, and PDSCH type A RE (ρB/ρA in
3GPP). The ratio of PDSCH EPRE to cell‐specific RS EPRE among PDSCH REs for each OFDM symbol is denoted by either ρA or ρB according to the OFDM symbol index
p‐A setting: Power offset between the reference signal and PDSCH channel in the symbols
without reference signal, P‐A can be found in RRC connection setup message.
P‐B setting: Power offset between PDSCH channel in the symbols with reference signal and
PDSCH channel in the symbols without reference, P‐B and RS power can be found in SIB2
Important
For Nokia System Pa = dlrsboost [−3, −2 ,−1, 0 ,1.77, 3, 4.77 ,6]
How do we allocate power to each of the those channels ?
The simplest way for our understanding would be to allocate the same power to all of the these channels, but this would be only for the sake of our understanding.For decoding any down link data, the first step is to detect/decode reference signal. If the power of this reference signal is same as all other channel power, it would not be easy (though not impossible) to detect it. So more practical implementation is to make Reference Signal outstanding comparing to other channels
The mapping between the possible P‐B values and the
actual values of the ratio ρB/ρA
Utilization under different combination of P‐A and P‐B.
ρA and ρB parameters setting.
Reference:- .sharetechnote.com and LTE Optimization Engineering Handbook by Xincheng Zhang
The RS power and the SCH powers are key RF optimization parameters that influences the
cell coverage. It is set according to the cell size. The higher the setting, the larger the cell coverage on the downlink, but leaves smaller power headroom available for other downlink signals and channels.
The relation between RS power and power on PDSCH symbols (includes type A and type B
symbols), has to be defined and reported to the UE, in order for the UE to demodulate 16QAM
and 64QAM.1 PDSCH type A symbols has only PDSCH RE’s, PDSCH type B symbols has mixed
RS and PDSCH REs. Parameter PA sets the power of PDSCH type A RE relative to cell‐specific
RS, PB sets the power relation between PDSCH type B RE, and PDSCH type A RE (ρB/ρA in
3GPP). The ratio of PDSCH EPRE to cell‐specific RS EPRE among PDSCH REs for each OFDM symbol is denoted by either ρA or ρB according to the OFDM symbol index
p‐A setting: Power offset between the reference signal and PDSCH channel in the symbols
without reference signal, P‐A can be found in RRC connection setup message.
P‐B setting: Power offset between PDSCH channel in the symbols with reference signal and
PDSCH channel in the symbols without reference, P‐B and RS power can be found in SIB2
Important
For Nokia System Pa = dlrsboost [−3, −2 ,−1, 0 ,1.77, 3, 4.77 ,6]
How do we allocate power to each of the those channels ?
The simplest way for our understanding would be to allocate the same power to all of the these channels, but this would be only for the sake of our understanding.For decoding any down link data, the first step is to detect/decode reference signal. If the power of this reference signal is same as all other channel power, it would not be easy (though not impossible) to detect it. So more practical implementation is to make Reference Signal outstanding comparing to other channels
The mapping between the possible P‐B values and the
actual values of the ratio ρB/ρA
Utilization under different combination of P‐A and P‐B.
ρA and ρB parameters setting.
Reference:- .sharetechnote.com and LTE Optimization Engineering Handbook by Xincheng Zhang
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