Wednesday, 11 November 2015

Airline Coverage Prach Plan

The Airline coverage network prach planning is different with the general prach planning. Because the coverage radius is as long as 100km and the height is as high as 10km. So network planning engineer should update the prach network planning to make the performance well.

   In the process of network planning during prach planning, it is usually to use the default value to set the prach planning. But this is different to airline coverage prach network planning. In the airline coverage, the radius is so long and the UE height is so high. So it is necessary to use the other value to make the prach planning. So the UE can be accessed successfully. This document describes how to set the value of prach planning during airline coverage.

  2.1 RaNcsType
       Configuration Principle: In order to support the 100km radius, it should be configurated as middle or low speed scene.
       Configuration Default Value: RaNcs Type = False.
       Configuration Reason: For the cells of airline coverage, RaNcs Type is configurated as middle or low scene.
2.2 PreambleFormat
       Configuration Principle: According the different cell radius to configurate PreambleFormat as 0~3.
       Configuration Default Value: Preamble = 3.
       Configuration Reason: For the cells of airline coverage, the cell radius is general 100km.
2.3 NcsPrach
       Configuration Principle: In middle or low speed scene, there is a relationship between this parameter and cell radius.
       Configuration Default Value: NcsPrach = 0.
       Configuration Reason: For the cells of airline coverage, the cell radius is general 100km and NcsPrach = 0.
2.4 NumRAPreambles
       Configuration Principle: Random access can be divided based on competitive and non-competitive. If the number of competitive preamble index is NumRAPreambles, non-competitive preamble index number is: cell users – NumRAPreambles.
       Configuration Default Value: NumRAPreambles =3.
       Configuration Reason: If a general cell which includes 5 logical root sequence and the NCS = 0. Then one cell includes 5 signature sequences. Because the load of competitive random access is low and majority of airlines are inter-cell handover (non-competitive random access). Then set aside 3 signature sequences as non-competitive preamble index. The remaining 2 signature sequences are competitive random access preamble index.
2.5 PrachConfIndex
       Configuration Principle: PrachConfIndex of random access configuration index is selected by Preamble Format and RA Slot.
       Configuration Default Value: PrachConfIndex = 49.
       Configuration Reason: If the cell random access conflict probability RACollProb is 0.01 seconds. The number of random access slots RASlot is 50 slot/s and it is enough. So the PRACH Desity value DRA is 0.5per10ms. For the FDD LTE system, the corresponding PrachConfIndex value is 49.
2.6 PrachFreqOffset
       Configuration Principle: Random access frequency resources PrachFreqOffset configuration principle is trying to avoiding interfering with control channel and traffic channel.
       Configuration Default Value: PrachFreqOffset = 1.
       Configuration Reason: For the Preamble Format3, in order to avoid interfering with control channel and traffic channel. PRACH is assigned immediately PUCCH resource block. In this 5MHz system, the bandwidth (25RBs) on both sides of each reserved 1RB for PUCCH transmission, total (0 to 24) RB. Random access frequency resources PrachFreqOffset configuration is 1RB.
2.7 RootSequenceStartNumber
       Configuration Principle: In the FDD LTE system, the ZC root sequence of Preamble Format3 allocation requirements do not conflict on the root sequence of the adjacent cell.
       Configuration Default Value: RootSequenceStartNumber = {3, 4} .
       Configuration Reason: In one general cell, if there is 4 logical root sequence and the NCS = 0. Then one cell has 4 signature sequences. The whole network needs 8 logical root sequences because the chained cells.
       For the chain cells, as long as the logical root sequence of 2 groups will be able to ensure the logical root sequence of neighboring cells do not conflict.
       When RootSequenceStartNumber = 3, indicating that the cell the logic used by the root sequence index number is {222,367};
       When RootSequenceStartNumber = 4, indicating the cell the logic used by the root sequence index number {826,827,830,831}.

 

RootSequenceStartNumber
Cell Users
Logic Root Sequence Index
1
3
22 23 826
2
827 830 831
3
4
22 23 6 7
4
826 827 830 831
5
5
22 23 6 7 8
6
9 826 827 830 831
7
6
22 23 6 7 8 9
8
2 3 826 827 830 831
9
7
22 23 6 7 8 9 2
10
3 4 5 826 827 830 831
11
8
22 23 6 7 8 9 2 3
12
4 5 12 13 826 827 830 831

Budi Prasetyo

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