Tuesday, 3 November 2015

TD-LTE downlink throughput analyze and simulation verification


 
This document is based on the project of China Mobile,To calculate the TD-LTE user throughput through the relation of the PDSCH Physical resources and MIMO gain,Use Atoll simulaton software to verify the result.
The China Mobile poroject parameter configuration as following table.
Table1 TD-LTE network configuration
Parameter
Value
Bandwith
20MHz
RB
100
Anterna port
2
CFI
2
RS power
12.2dBm
Frame switch period
5ms
Frame configuration
3DL:1UL
Special Frame configuration
10:2:2
Table 2  TD-LTE terminal parameter
Parameter
Value
Maximum power
23dBm
Minimum power
-40dBm
Noise figure
7dB
Transmission port
1
Reception port
2
 
TD-LTE downlink throughput prediction process as following.
Transmit Diversity
Ø  Determine the pixel location of the main service cell
Ø  Calculate the PDSCH CINR of single port.
Find out Transmit Diversity gain from MIMO configuration table.
Ø  Update the PDSCH CINR based on the Transmit Diversity gain.
Ø  According to the updated  PDSCH CINR ,Mapping to the bear level from the MSC table.
Ø  Calculate the downlink throughput through the relation of bearer efficiency and PDSCH available RE.
SU-MIMO
Ø  Determine the pixel location of the main service cell
Ø  Calculate the PDSCH CINR of single port.
Ø  Find out SU-MIMO gain from MIMO configuration table.
Ø  Update the PDSCH CINR based on the SU-MIMO gain.
Ø  According to the updated  PDSCH CINR ,Mapping to the bear level from the MSC table.
Ø  Based on the bearer efficiency and PDSCH available RE,Calculate the throughput that single port can support.
Ø  According the SU-MIMO gain from MIMO configuration table,To Calculate user Calculate by single port throughput multiply SU-MIMO gain.
According the above prodection process,TD-LTE downlink throughput can be calculate by following  formula.
User Downlink Transmit Diversity throughput=(PDSCH Transmit Diversity
RE)*(Bearer efficiency)/0.01 ------------------------------------------------------------------Formula 1
User Downlink SU-MIMO throughput=( PDSCH User Downlink RE)*Bearer efficiency*SU-MIMO gain/0.01 ----------------------------------------------------------------------Formula 2
According the curent network configuration,TD-LTE physical resource overhead of10MS frame as following table
Table3 Downlink physical resource overhead
Physical Resource
RE
RS
6000
PSS
144
SSS
144
PBCH
240
PDCCH
16000
PDSCH
96272
Free RE
6000
PDSCH available RE
124800
Atoll downlink bearer parameter configuration
Due to the downlink diversity mode is AMS,Select the transmit diversity area and use.
Atoll simulation tool to verify the result.
TD-LTE Downlink transmit diversity simulation:
The simulation result
Table4 Downlink transmit diversity simulation result
Diversity Mode (DL)
Transmit Diversity
PDSCH C/(I+N) (DL)
13.988 dB
Bearer (DL)
16 (DL-16)
Peak RLC Channel Throughput (DL)
18,484.2 kbps
From simulation result,This area use transmit diversity ,Bearer level is 16,The downlink  throughput is 18,484.2kbps.
According to the bearer configuration,the bearer efficiency is 1.92.
On the current netwok configuration,The PDSCH available RE is 96272.
Based on formula 1,TD-LTE downlink transmit diversity throughput=96272*1.92/0.01=18,484.2Kbps.     
From above analysis,TD-LTE calculate throughput of transmit diversity is same with simulation result.
Select one point in the SU-MIMO simulation area, Downlink SU-MIMO simulation as following:
The simulation analysis result:
Table 5 Downlink SU-MIMO simulation result
Diversity Mode (DL)
SU-MIMO
PDSCH C/(I+N) (DL)
24.68 dB
Bearer (DL)
28 (DL-28)
Peak RLC Channel Throughput (DL)
73,085.8 kbps
Form the abve simulation result,this area use SU-MIMO,bearer level is 28,The downlink throughput is 73,085.8kbps.
According to the bearer and MIMO configuration,the bearer efficiency is 4.32,the SU-MIMO gain is 1.757.
In the current network configuration,The PDSCH available RE is 96272.
From formal 2,the downlink SU-MIMO throughput=(PDSCH avdaable RE)*(bearer efficient)*(SU-MIMO gain)/0.01=96272*4.32*1.757/0.01=73,072.8Kbps
As above analysis,TD-LTE downlink throughput of SU-MIMO is almost same with the simulation result.
 
TD-LTE calculate throughput and Atoll simulation result statistics as following table.
Table6 TD-LTE calculate throughput and simulation result
scenario
Calculate ThroughputKbps
Simulation Result
Kbps
Transmit Diversity
18,484.2
18,484.2
SU-MIMO
73,072.8
73,085.8 kbps
From the above table,the TD-LTE calculate throughput is same with simulaton result.
From the TD-LTE system physical resource overhead and simulation analysis,the factor that will effect user throughput as following:
System bandwidth
Frame configuration
Antenna ports
Control channel overhead
MIMO diversity mode
MIMO gain
Terminal capability level
Description: http://support.zte.com.cn/support/KnowledgeBase/images/collapse.gif Summary and Notes
The document is based on the China Mobile network configuration,Introduce the TD-LTE system physical resource overhead,Calcute the user tthroughput according the relation of  physical resource overhead and MIMO gain,Use atoll simulation to verify the throughput of calculate result.

Budi Prasetyo

About Budi Prasetyo

All About LTE

Subscribe to this Blog via Email :