LTE-Radio-Procedures-Huawaei.pdf

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LTE Radio Interface Procedures

HUAWEI TECHNOLOGIES CO., LTD.

Contents 1- FAQs Frame Structure//Throughput Calculations etc 2- Reselection 3- SIBs 3- Registration IDLE Mode 4-Paging 5-Handover 6-DL Power Connected Mode Control 7-DL Scheduling Self Optimization Network 8-ANR 9-ICIC

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Page 2

FAQs

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Page 3

Frame Structure (FDD)

Related Concept 1- Radio Frame 2-Subframe 3-Slot 4- Subcarrier 5- Resource Block (Scheduling Minimum Unit) 6- Resource Element

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Channel BW (MHz)

RB Number

Subcarrier Number

1.4

6

72

3

15

180

5

25

300

10

50

600

15

75

900

20

100

1200

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Page 4

Number of Scheduled User in 1 TTI Scheduling information is in PDCCH frame. 1- Total Number of RE for PDCCH=100(RB for 100Mhz)*12(SC)*3 2- Total Number of bits for PDCCH in 1 TTI=100*12*3*Modulation

2bits for QPSK 4bits for 16QAM 6bits for 64QAM Based on CQI Take 6 as example: Total Number of bits for PDCCH in 1 TTI=100*12*3*6=21600 Number of bits required by each user for scheduling= 17 Total User support for scheuding =21600/17=1270 Users Note : Actually need to consider PCFICH+PHICH (from diagram) i.e. (1270-PCFICH-PHICH)/17 ~~ 1000 users approx

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Page 5

Downlink Calculation Downlink maximum throughput = Number of RB × 12 (Number of Sub-carrier with one RB) × 14 (Number of Symbols with a Sub-frame) × [ 1 － (RS overhead and PDCCH overhead) ] × Modulation symbols efficiency × MIMO × 1000 (Number of Sub-frame in one second) × Coding rate

Example: Calculate the FDD LTE system 10M, 2 * 2 MIMO, 64QAM, the Coding rate is 1. The single cell downlink physical layer theory rate = 50*12*14*(1-(2/21+1/21))*6*2*1000*1 =82.4Mbps 50  50 RB 12 One RB includes 12 sub-carrier 14  A sub-frame 14 symbol 6  64QAM each symbol represents 6 bits 2  2*2 MIMO 1000  1s=1000ms 2/21 RS overhead (total symbol of one RB=12*14=168, RS symbol number=16, 16/168=2/21) 1/21 PDCCH overhead (If downlink sub-frame PDCCH accounted for only a symbol, and the PDCCH symbol is the first symbol of the sub-frame, this is the minimal overhead in PDCCH, a downlink sub-frame occupies 8 subcarriers, so the minimal PDCCH overhead is 8 symbols, 8 / (14 * 12) =8/168= 1/21. 82.4Mbps this is an ideal value, because the SCH, BCH also take up some of the resources, and consider the coding rate, the actual Downlink peak rate around 70Mbps Page 6 HUAWEI TECHNOLOGIES CO., LTD.

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Uplink Calculation Uplink maximum throughput = Number of RB × 12 (Number of Sub-carrier with one RB) × 14 (Number of Symbols with a Sub-frame) × ( 1 － RS overhead ) × Modulation symbols efficiency × 1000 (Number of Sub-frame in one second) × Coding rate Example: Calculate the FDD LTE system 10M, None MIMO, 16QAM, the Coding rate is 1. The UE uplink physical layer theory rate = 46*12*14*(1-1/7)*4*1000*1=26.5Mbps 46  46 RB 12 One RB includes 12 sub-carrier 14  A sub-frame 14 symbol 4  16QAM each symbol represents 4 bits 1  Coding rate 1/7Pilot overhead 1000  1s=1000ms UE cat4 does not support 64QAM and MIMO in uplink, and consider the PUCCH occupied 4RB, the pilot overhead is 1/7, the uplink can reach the peak rate 25.6Mbps, in fact should also consider the impact of sounding and PRACH, the uplink peak rate around 25Mpbs HUAWEI TECHNOLOGIES CO., LTD.

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Page 7

Carrier Frequency EARFCN Calculation(3GPP : 36.104) Channel raster

Table 5.7.3-1 E-UTRA channel numbers

The channel raster is 100 kHz for all bands, which means that the carrier centre frequency must be an integer multiple of 100 kHz.

Carrier frequency and EARFCN The carrier frequency in the uplink and downlink is designated by the E-UTRA Absolute Radio Frequency Channel Number (EARFCN) in the range 0 - 65535. The relation between EARFCN and the carrier frequency in MHz for the downlink is given by the following equation, where FDL_low and NOffs-DL are given in table 5.7.3-1 and NDL is the downlink EARFCN.

FDL = FDL_low + 0.1(NDL – NOffs-DL) The relation between EARFCN and the carrier frequency in MHz for the uplink is given by the following equation where FUL_low and NOffs-UL are given in table 5.7.3-1 and NUL is the uplink EARFCN.

FUL = FUL_low + 0.1(NUL – NOffs-UL)

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Downlink Uplink E-UTRA FDL_low [MHz] NOffs-DL Range of NDL FUL_low [MHz] NOffs-UL Range of NUL Operating Band 1 2110 0 0 – 599 1920 18000 18000 – 18599 2 1930 600 600 - 1199 1850 18600 18600 – 19199 3 1805 1200 1200 – 1949 1710 19200 19200 – 19949 4 2110 1950 1950 – 2399 1710 19950 19950 – 20399 5 869 2400 2400 – 2649 824 20400 20400 – 20649 6 875 2650 2650 – 2749 830 20650 20650 – 20749 7 2620 2750 2750 – 3449 2500 20750 20750 – 21449 8 925 3450 3450 – 3799 880 21450 21450 – 21799 9 1844.9 3800 3800 – 4149 1749.9 21800 21800 – 22149 10 2110 4150 4150 – 4749 1710 22150 22150 – 22749 11 1475.9 4750 4750 – 4949 1427.9 22750 22750 – 22949 12 728 5000 5000 – 5179 698 23000 23000 – 23179 13 746 5180 5180 – 5279 777 23180 23180 – 23279 14 758 5280 5280 – 5379 788 23280 23280 – 23379 … 17 734 5730 5730 – 5849 704 23730 23730 – 23849 18 860 5850 5850 – 5999 815 23850 23850 – 23999 19 875 6000 6000 – 6149 830 24000 24000 – 24149 20 791 6150 6150 - 6449 832 24150 24150 - 24449 21 1495.9 6450 6450 – 6599 1447.9 24450 24450 – 24599 … 33 1900 36000 36000 – 36199 1900 36000 36000 – 36199 34 2010 36200 36200 – 36349 2010 36200 36200 – 36349 35 1850 36350 36350 – 36949 1850 36350 36350 – 36949 36 1930 36950 36950 – 37549 1930 36950 36950 – 37549 37 1910 37550 37550 – 37749 1910 37550 37550 – 37749 38 2570 37750 37750 – 38249 2570 37750 37750 – 38249 39 1880 38250 38250 – 38649 1880 38250 38250 – 38649 40 2300 38650 38650 – 39649 2300 38650 38650 – 39649 NOTE: The channel numbers that designate carrier frequencies so close to the operating band edges that the carrier extends beyond the operating band edge shall not be used. This implies that the first 7, 15, 25, 50, 75 and 100 channel numbers at the lower operating band edge and the last 6, 14, 24, 49, 74 and 99 channel numbers at the upper operating band edge shall not be used for channel bandwidths of 1.4, 3, 5, 10, 15 and 20 MHz respectively.

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Page 8

Example FDL (center Freq) = FDL_low + 0.1(NDL (EARFCN) – NOffs-DL) Or

NDL (EARFCN)= 10*(FDL (center Freq) - FDL_low ) + NOffs-DL Say FDL (center Freq) = 1815 NDL (EARFCN)=10*(1815-1805)+1200 NDL (EARFCN)=1300

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Page 9

IDLE Mode Behavior Idle Mode Overview PLMN Selection Cell selection & cell reselection System Information reception Tracking area registration Paging monitoring procedure

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Idle Mode Overview A UE that is powered on but does not have an RRC connection to the radio network is defined as being in idle mode. In the case of idle mode management, the eNodeB sends configurations by broadcasting system information, and accordingly, UEs select suitable cells to camp on. Idle mode management can increase the access success rate, improve the quality of service, and ensure that UEs camp on cells with good signal quality.

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Page 11

PLMN Selection

A PLMN identity consists of a Mobile Country Code (MCC) and a Mobile Network Code (MNC). When a UE is powered on or recovers from lack of coverage, after the cell search, the UE first selects the last registered PLMN and attempts to register on that PLMN. If the registration on the PLMN is successful, the UE shows the selected PLMN on the display, and now it can obtain service from an operator. If the last registered PLMN is unavailable or the registration on the PLMN fails, another PLMN can be automatically or manually selected according to the priorities of PLMNs stored in the USIM.

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Page 12

Cell Selection & Reselection Cell search is a procedure in which a UE achieves time and frequency synchronization with a cell, obtains the physical cell ID, and learns the signal quality and other information about the cell based on the physical cell ID. Before selecting or reselecting a cell, a UE performs a cell search on all carrier frequencies. In the Long Term Evolution (LTE) system, Synchronization Channels (SCHs) are specially used for cell search. There are two types of SCH: Primary Synchronization Channel (P-SCH) and Secondary Synchronization Channel (S-SCH). The cell search procedure on SCHs is as follows: The UE monitors the P-SCH to achieve clock synchronization with a maximum synchronization error of 5 ms. Physical cell IDs have one-to-one mapping with primary synchronization signals. Therefore, the UE acquires the physical cell ID by monitoring the P-SCH. The UE monitors the S-SCH to achieve frame synchronization, that is, time synchronization with the cell. Cell ID groups have a one-to-one relation with secondary synchronization signals. Therefore, the UE acquires the number of the cell ID group to which the physical cell ID belongs by monitoring the S-SCH. The UE monitors the downlink reference signal to acquire the signal quality in the cell. The UE monitors the Broadcast Channel (BCH) to acquire other information about the cell. HUAWEI TECHNOLOGIES CO., LTD.

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Page 13

Cell Selection Criteria 

During cell selection, a UE needs to check whether a cell fulfills the cell selection criteria. The cell selection is based on the RSRP of the E-UTRAN cell. Before a UE can select a cell to camp on, the RSRP of the cell must be higher than the user-defined minimum receive (RX) level Qrxlevmin of the cell.

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The formula for cell selection decision is as follows:



Srxlev > 0



where Srxlev = Qrxlevmeas - (Qrxlevmin + Qrxlevminoffset) - Pcompensation





Qrxlevmeas is the measured RX level in the cell (RSRP), expressed in decibels with reference to one milliwatt (dBm).



Qrxlevmin is the minimum required RX level (set in the eNodeB) in the cell, expressed in units of dBm.



Qrxlevminoffset is the offset to Qrxlevmin. This offset is taken into account when the UE attempts to camp on a cell in a higher-priority PLMN. That is, when camped on a cell in a VPLMN, the UE considers this offset parameter, which was signaled from the associated cell in the higher-priority PLMN, in the Srxlev evaluation.

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Pcompensation is generated according to the function max(PMax - UE Maximum Output Power, 0). The value is expressed in decibels (dB).



PMax is the maximum allowed transmit power of the UE in the cell, expressed in units of dBm. It is used in uplink transmission. HUAWEI TECHNOLOGIES CO., LTD.

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Page 14

Cell Reselection 

The signal strength of both serving cell and neighboring cells varies with the movement of UE and so the UE need to select the most suitable cell to camp on. This process is called cell reselection.

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Cell reselection process: 

Measurement Start criteria



Cell reselection criteria

Intra frequency Interfrequency (within LTE) InterRAT ( LTE to Other RAT) HUAWEI TECHNOLOGIES CO., LTD.

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Page 15

Intra frequency Measurement 

If the intra frequency measurement triggering threshold is not configured, the UE performs intra frequency measurements always.



If the intra frequency measurement triggering threshold is configured:

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Srxlev > SintraSearch, 



the UE does not perform intra frequency measurement.

Srxlev SNonIntraSearch, UE does not perform inter frequency / RAT measurement



When Srxlev

Cell 1

2

UE SS

< Now UE is in IDLE mode >

Cell 1

3

UE SS

RRC Connection Request

Cell 1

5

UE SS

RRC Connection Setup Complete

Cell 1

7

UE SS

Security Mode Complete

Cell 1

9

UE SS

RRCConnectionReconfigurationComplete

Cell 1

11

UE SS

RRCConnectionReconfigurationComplete

Cell 1

13

UE ---> SS

Measurement Report

Cell 1

14

UE SS

PRACH

Cell 2

16

UE SS

RRCConnectionReconfigurationComplete

Cell 2

18

UE SS

ueCapabilityInformation

Cell 2

20

UE ---> SS

ulInformationTransfer + Detach Request

Cell 2

21

UE