01. lte - rf configuration parameter.pdf

8/10/2019 01. LTE - RF Configuration Parameter.pdf

1/21

http://www.linkedin.com/pub/ray-khastur/36/965/b7a

LTE - RF Configuration Parameters


2/21

4G LTE - RF Configuration Parameters| Page 2

P I Planning


3/21

4G LTE - RF Configuration

Purpose of PCI PlanningCell ID groups are adopted in the cell search procedure of the LTE system.

Specifically, a specific ID within a cell group is determined through the PSCH,

and then a cell group ID determined through the SSCH.

As specified in 3GPP protocol, the cell ID at the physical layer consists of cel

group ID and the ID within the cell group.

There are 168 physical layer cell groups and each group consists of three IDs.

Therefore, totally there are 504 ( 0 to 503 ) PCIs.


4/21


PCI Overview In LTE systems, each cell has a physical cell identifier (PCI), enabling UE to

differentiate radio signals of different cells.

In LTE systems, cells are grouped. They are searched based on the primary andsecondary synchronization sequences.

The secondary synchronization sequence on the secondary synchronization channe

(SSCH) determines the cell group ID

The primary synchronization sequence on the primary synchronization channel (PS

determines the cell ID in a cell group.


5/21


PCI planning proposed for M LTE project PCI group code from 120 to 167 for IBC eNodeB

PCI 360 to 503

Propose 25% buffer for future expansion ( 468 to 503 reserved for future )

PCI group code from 0 to 119 for Outdoor eNodeB PCI 0 to 359

Propose 25% buffer for future expansion ( 270 to 359 reserved for future )

Planning rule To reduce PCI mod 3 result competition among neighboring cells to get better performa

under low load situation (referring to following 2 slides)

To avoid PCI mod 30 result competition among neighboring cells to avoid SRS interfereneighbor cell PRACH

Huawei use GENEX U-Net to plan PCI


6/21


PCI Mod 3 Reference Signal

RS pattern fordifferent Antenna

configuration 1 A n

t e n n a

P o r t

2 A n

t e n n a

p o r t s

4 A n

t e n n a

p o r t s

Antenna Port 0 Antenna Port 1 Antenna Port 2 Antenna Port 3

RE

No RS transmitfor this antenna portRS transmittedor this antenna port

RRRR

For 4*4 MIMO, the RS of Antenna 3

transmitted on OFDM symbols differ

Antenna 1, 2

No. of Antenna port

No. of RS per Antport per RB within

one Symbol

No. of RS for all Antports per RB within

one Symbol

1 2 2 2 2 4 4 2 4


7/21


PCI Mod 3 RS shift among neighbor cells Frequency domain location of the RS is determined by value of PCI mod 3

If RS is shifted, then it will help for better performance under low load

RS location vs PCI mod 3:


8/21


Assume there is a new site insert into Cyb

It is recommended to plan PCI after neigh

0

1

2

01

2

0

12

0

1

2

0

1

2

0

1

2

1

Step 1. Mark the PCI Mo

existing cells on the mapStep 2. Decide the PCI M

the new site on the map. Tto avoid same result coverStep 3. Choose un-used P

new site following the PC

result. New PCI shall not neighbor cell.

Step 4. Check the PCI mowith neighboring cell.

3

4

5

Note: Please use PowerPoint Slide Show mode to see the animation to play the steps.

How to Plan PCI manually


9/21


AFTER MODIFICATBEFORE

PCI Mod3 Planning

We need to check again aboutPCI Mod3 result, prevent co-channel interference from sameMod3 result.


10/21

4G LTE - RF Configuration P

What is Antenna Ports?


11/21


What is Antenna Ports?


12/21


13/21


PRACH Random Access Channel (RACH) RACH procedure begins with a preamble (PRACH) PRACH resources assigned by eNB within PUSCH region

PRACH preamble fits into 6 PRBs Sufficient for timing estimation Invariant with bandwidth for low complexity Zadoff Chu sequence Excellent correlation properties

Zero correlation zone for different cyclic shifts Flat frequency spectrum Different sequences provided first by different cyclic shifts, then byroot sequences

Multiple PRACH formats suitable for different cell sizes


14/21


PRACH Planning Principle There are 64 PRACH preambles in each LTE cell for Radom Access Preambles are generated from root sequence ( Zadoff-Chu sequence ) a

shift

838 root sequences are defined by 3GPP with length 839 For example: for Cyclic Shift step 76, so-call Ncs = 76

Each root sequence can generate Rounddown(839/76) = 11 sequences To Generate 64 sequences, number of root sequences needed = Roundup(64/11) = 6 So available root sequences = Rounddown (838/6) = 139 (Index 0, 6, 12, 18, )

Root sequence needs to be reuse in the network Unlike UMTS, there isnt Cell ID related scramble code used for PRACH in LTE s

collision may occur if same root sequence is planned for PRACH among nearby c

Thus, we need to plan PRACH root sequence.

d d h l h f ( )


15/21


How to decide the cyclic shift step (Ncs) Ncs * Ts > T RTD + TMDS + Tdev

Ncs is mainly decided by Cell radius. TRTD = 2*R/C = 2*R / (3*10 8 ) seconds = 6.67 * R (us)

TRTD is round trip delay, decided by cell radius R C is light speed = 3*10 8 m/s

TMDS is Maximum time delay spread, 5us for Dense Urban and Urban Tdev is UE timing deviation due to un-ideal synchronization to the downlink

Typically, assume T MDS = 5us, UE timing deviation = 2us

Ts is PRACH sampling period, and Ts = 800/839 [us]If planned cell radius = 9.8Km, then Ncs = 76

PRACH N S l i


16/21


PRACH Ncs Selection Three dimensions needs to consider:

Cell radius Margin (over dimensioning for unexpected transmission delay spread)

Root sequence reuse in multi-cell environment Ncs=76 for M project LTE PRACH Planning in KV area For NLOS case, the transmission delay may be larger than LOS case, i.e., transmit dist

larger than cell radius, margin is needed to keep robust

Root sequence is enough for multi-cell reuse: 6 root sequences are needed for each cell838/6 = 139 unique sequences can be assigned for 139 cells

Same setting is just to simplify the network design. Ncs can also be set to different valuaccording to coverage scenario.

PRACH Pl i


17/21


PRACH PlanningStep 1 : Determine Ncs value by the cell radius. (E.g. Assume the cell radius i

9.8 km, take Ncs value 76)

Step 2 : The value of 839/76 is rounded down to 11, that is, each index should

generate 11 preamble sequences. In this case, 6 (64/11) root sequence indexes

are required to generate 64 preamble sequences.

Step 3 : The number of available root sequence indexes is 139 (0, 6

828)

Step 4 : The available root sequence indexes are assigned to cells. The reuse

distance shall be as far as possible

Huawei will use GENEX U-Net for PRACH planning

PRACH Pl i (I P j t)


18/21


PRACH Planning (I Project) Preambles are generated from root sequence (Zadoff-Chu sequence) and its cyclic shift step (Ncs)

Cell Radius ( r ) 10 km for low speed cells TMD indicates the maximum multi-path delay spread. For HLTE products, T MD equals to 5 millise

UE timing deviation is 2 milliseconds Ncs > 1.04875(6.67*10 +5+2) = 77. 03 According to the table Ncs for preamble format 0 to 3

The Ncs value is 93 , the Ncs configuration number 11

PRACH Pl i g (I P j t)


19/21


PRACH Planning (I Project) The number of preamble that can be generated is calculated as follow :

The number of ZC sequences is calculated as follows:9

93

839 Num

89

64m

PRACH Planning (I Project)


20/21


PRACH Planning (I Project)

InpuPara1)2)3)


21/21

01. lte - rf configuration parameter.pdf

Documents