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5G Procedures Flashcards

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1
Q

The process by which UE measures and identifies the best beam.

A

Beam Sweeping by gNB and Beam Selection by UE

i) Multiple SSBs are being transmitted with a certain interval.

ii) Each SSB can be identified by a unique number called SSB index

iii) Each SSB is transmitted via a specific beam radiated in a certain direction

iv) Multiple UEs are located at various places around a gNB.

v) UE measures the signal strength of each SSB it detected for a certain period (a period of one SSB Set).

vi) From the measurement result, UE can identifies the SSB index with the strongest signal strength. This SSB with the strongest signal strength is the best beam for the UE 1.

https://www.sharetechnote.com/html/5G/5G_SS_Block.html

https://www.sharetechnote.com/html/5G/5G_Phy_BeamManagement.html

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2
Q

The parameter defining the maximum number of SSBs within a SS Burst set is called Lmax.

How many beams can be used in below 3GHz? And in which directions?

How many beams can be used in sub-6GHz? And in which directions?

How many beams can be used in mmWave? And in which directions?

A

SSBs are organized in burst sets, with a burst set consisting of one or more SSBs.

In sub 6 Ghz, Lmax is 4 or 8 and in mmWave Lmax is 64.

In other words, in sub6 Ghz, max 4 or 8 different beams can be used and they sweep in one dimension (horizontal only or vertical only). in mmWave max 64 different beams can be used and they can sweep in two dimensions (horizontal and vertical directions).

www.5GWorldPro.com

https://moniem-tech.com/2020/11/22/5g-nr-synchronization-signal-block-ssb/

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3
Q

This is a crucial technique used to direct the signal toward a specific user equipment (UE) to maximize signal quality and strength. This is particularly important in the mmWave bands, where signals are more susceptible to attenuation and blockage.

A

Beamforming

NR - SSB Beam Detection: The initial SSB beam detection process involves the gNB transmitting a set of SSBs across various directions (Each SSB burst is transmitted in different directions). The UE scans for these beams and measures the signal strength to determine which beam provides the best reception. The process is critical for establishing an initial link between the base station and the UE, allowing further communication to be optimized for the direction of the best signal.

https://www.sharetechnote.com/html/TechSlide/html/NR_SSB_Beam_Detection_01.html

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4
Q

This is part of the total channel bandwidth configured for a cell that is used for a UE at a specific moment of operation.

A

Bandwidth Part (BWP)

Usually a cell configures multiple BWPs out of the total channel bandwidth and select a specific one at each moment of operation.

  • BWPs can overlap in terms of frequency span and location
  • Minimum bandwidth of a BWP should be equal or larger than SSB Bandwidth
  • It is not mandatory for every BWP should transmit SSB
  • Max number of BWP that can configured is 4, but only one of them can be active at a specific time.
  • Each DL BWP should have at least one CORESET with UE Specific Search Space (USS)
  • In Primary DL BWP, there should be at least one CORESET with Common Search Space (CSS)
  • There are roughly 3 ways of BWP switching : Timer based, DCI based, RRC Based
  • It would require a certain amount of time to switch between BWPs and the minimum switching time is up to UE capability which should be informed to network via UE capability Information.

https://www.sharetechnote.com/html/5G/5G_CarrrierBandwidthPart.html

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5
Q

The minimum requirement for UE to camp on a cell

A

Decoded MIB and SIB1

https://www.sharetechnote.com/html/5G/5G_Mib_Sib.html

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6
Q

What are the number of vertical beams in 32T32R Massive MIMO?

A

2

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7
Q

True / False:
The beam scenarios for SSB already existed in 4G

A

False

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8
Q

True / False:
DSS LTE layer can be used as NR Anchor in NSA architecture

A

False

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9
Q

Which type of tilt does not exist in 5G Massive MIMO?

A

the Beamforming downtilt

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10
Q

True / False:
For cell-edge UEs, PMI-based weights are more accurate than SRS-based

A

True

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11
Q

In a frequency of 5G 2.3GHz, what is the maximum number of consecutive SSBs?

A

8

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12
Q

SSB is composed of:

A

PSS, SSS, PBCH
PSS(Primary Sync Signal),SSS(Secondary Sync Signal) and PBCH

PSS (Primary Synchronization Signal) and SSS (Secondary Synchronization Signal) are also referred to as “Synchronization Signal (SS)”

PBCH(Physical Broadcast Channel) is composed of PBCH DMRS(Demodulation Reference Signals (DM-RS)) and PBCH (Data)

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13
Q

What is the difference between SSB in LTE and 5G?

A

Major difference between LTE SS/PBCH and NR SSH lies in the periodicity of each channel.

In LTE, SS(PSS,SSS) are transmitted in every 5ms and PBCH is transmitted in every 10ms. That is, the periodicity of SS and PBCH are different in LTE.

However in NR, SS(PSS,SSS) and PBCH are transmitted all at the same time, which means their periodicity is all same.

Typical periodicity of SSB(SS+PBCH) in NR is 20ms, but the periodicity can vary in terms of 3GPP specification.

(In LTE, we didn’t use the term ‘SS Block’, but LTE also use PSS/SSS and PBCH which can be called as SS Block)

Reference: https://www.sharetechnote.com/html/5G/5G_SS_Block.html

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14
Q

Carries specific signals for establishing Downlink Synchronization

A

Synchronization Signal Block (SSB)

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15
Q

It serves as the primary channel through which a base station (eNodeB in LTE, gNodeB in 5G) transmits MIB to UEs.

It carries crucial information that a UE needs to decode other broadcast information and to establish a connection with the network.

A

PBCH

https://www.sharetechnote.com/html/5G/5G_PBCH.html

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16
Q

Name a few information that are contained in PBCH

A

PBCH Payload Generation: The broadcast channel (BCH) data is generated. This is the first step where the data that needs to be broadcasted is prepared.

Scrambling: The generated payload is scrambled. This step is crucial for mitigating interference and maintaining the integrity of the signal.

CRC Attachment: A Cyclic Redundancy Check (CRC) is attached to the scrambled data for error detection purposes.

Channel Coding: The data with the CRC is encoded to protect against potential errors during transmission.

Rate Matching: The encoded data is then processed through rate matching to ensure that it fits the available transmission resources.

Scrambling: The rate-matched data undergoes a second scrambling process. This could be for additional security or interference mitigation.

Modulation: The scrambled data is then modulated, which means it is converted into a waveform suitable for transmission over the radio frequency spectrum.

Resource Element Mapping: The modulated data is mapped onto the resource elements in the frequency-time grid for actual transmission.

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17
Q

Please arrange the following according to the Hierarchy of Frame Structure :
{ Slot, Frame, Subframe }

A

Frame(Radio Frame) –> SubFrame –> Slot (Same as in LTE)

https://www.sharetechnote.com/html/5G/5G_FrameStructure.html

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18
Q

Length of 1 Radio Frame in 5G

A

10 ms (Same as in LTE)

https://www.sharetechnote.com/html/5G/5G_FrameStructure.html

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19
Q

Length of 1 subframe in 5G

A

1 ms (same as in LTE)

https://www.sharetechnote.com/html/5G/5G_FrameStructure.html

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20
Q

Number of Subcarriers within 1 RB

A

12 (same as in LTE)

https://www.sharetechnote.com/html/5G/5G_FrameStructure.html

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21
Q

True / False:
Possible Numerologies (subcarrier spacing) : 15,30,60,120,240,480,960 in kHZ

A

True

https://www.sharetechnote.com/html/5G/5G_FrameStructure.html

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22
Q

True / False:
Length of a slot in time domain gets shorter as subcarrier spacing gets larger

A

True

https://www.sharetechnote.com/html/5G/5G_FrameStructure.html

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23
Q

5G frame structure is flexible, which means, the time-frequency resources are divided into resource blocks and further subdivided into resource grid elements.

The 5G network can dynamically adjust the duration of each time slot based on the service’s needs.

True / False: A data-heavy service might get longer slots.

A

True

https://www.sharetechnote.com/html/5G/5G_FrameStructure.html

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24
Q

5G frame structure is flexible, which means, the time-frequency resources are divided into resource blocks and further subdivided into resource grid elements.

The 5G network can dynamically adjust the duration of each time slot based on the service’s needs.

True / False: The services that needs quick response times, like remote surgery or smart factories, might be allocated shorter slots.

A

True

https://www.sharetechnote.com/html/5G/5G_FrameStructure.html

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25
What does "self-contained slots" mean?
Self contained slot is the slot that contains "everything" within the single slot. The meaning of 'everything' in this context is - DCI (Downlink Control Information) scheduling, - PDSCH (DL data transmission) and - ACK/NACK feedback in PUCCH (Physical Uplink Control Channel) Therefore, self-contained slot means the slot where the scheduling, data transmission and HARQ feedback happens within the same slot. There can be self-contained slot for Uplink as well. It contains in the same slot: - UCI (Uplink Control Information) - PUSCH (Uplink Data transmission) - PDCCH (Physical Downlink Control Channel). In this case, k2 should be 0. Main purpose of the purpose of a self-contained slot is to support ultra-reliable and low-latency communications (URLLC) and key benefits of self-contained slot are: - Low latency - Improved efficiency - Simplified scheduling - Flexibility https://www.sharetechnote.com/html/5G/5G_SelfContainedSlot.html https://wirelessbrew.com/5g-nr/self-contained-slot-in-5g-nr/ https://www.sharetechnote.com/html/5G/5G_FrameStructure.html
26
What is the difference between the subcarrier spacing values of LTE and 5G?
In LTE there is only one type of subcarrier spacing, 15 Khz. NR supports multiple different types of subcarrier spacing {15,30,60,120,240,480,960 in kHZ} https://www.sharetechnote.com/html/5G/5G_FrameStructure.html
27
True / False: For slot with normal CP(Cyclic Prefix), the number of symbols for a slot is always 14 and for slot with extended CP, the number of symbols for a slot is always 12.
True https://www.sharetechnote.com/html/5G/5G_FrameStructure.html
28
This parameter is used to derive the slot in which PUSCH transmission occurs.
K2 (Ksub2) This is configured in PUSCH-TimeDomainResourceAllocationList IE (0...32) The IE PUSCH-TimeDomainResourceAllocation is used to configure a time-domain relation between PDCCH and PUSCH. PUSCH-TimeDomainResourceAllocationList contains one or more (up to 16) of such PUSCH-TimeDomainResourceAllocations. The UE determines the bit width of the DCI field based on the number of entries in the PUSCH-TimeDomainResourceAllocationList. The network indicates in the UL grant (DCI) which of the configured time domain allocations the UE shall apply for that UL grant. Value 0 in the DCI field refers to the first element in this list, value 1 in the DCI field refers to the second element in this list, and so on. If K2 = 0: it is a self-contained slot If K2 = , the UE applies the value 1 when PUSCH SCS is 15/30 kHz; the value 2 when PUSCH SCS is 60 kHz, and the value 3 when PUSCH SCS is 120KHz. https://howltestuffworks.blogspot.com/2019/12/5g-nr-pusch-resource-allocation-in-time.html
29
What is the relation between the numerology value to the number of slots within one radio frame?
At Normal Cyclic Prefix (CP) where there are 14 symbols in a slot, 10 slots in a 1subframe (fixed), when N=0 #subframe = 2^N, where - Numerology = N so : 2^1 = 2 subframes = 2x10 = 20 slots in one radio frame 2^2 = 4 subframes = 4x10 = 40 slots in one radio frame 2^3 = 8 subframes = 8x10 = 80 slots in one radio frame 2^4 = 16 subframes = 16x10 = 160 slots in one radio frame 2^5 = 32 subframes = 32x10 = 320 slots in one radio frame 2^6 = 64 subframes = 64x10 = 640 slots in one radio frame
30
How UE determines if the gNB is FR1 or FR2?
MIB: subCarrierSpacingCommon SIB: subcarrierSpacing in BWP parameters From MIB, there is subCarrierSpacingCommon IE, which is either: - scs15or60 for FR1 - scs30or120 for FR2 Then in SIB1 contains ServingCellConfigCommonSIB which contains downlinkConfigCommonSIB which contains initialDownlinkBWP which contains BWP-DownlinkCommon which contains generic parameters of BWP { locationsAndBandwidth, subcarrierSpacing , cyclicPrefix } subcarrierSpacing : Subcarrier spacing to be used in this BWP for all channels and reference signals unless explicitly configured elsewhere. It corresponds to subcarrier spacing according to 38.211-Table 4.2-1. The value kHz15 corresponds to=0, kHz30 to =1, and so on. Only the values 15 or 30 kHz (<6GHz), 60 or 120 kHz (>6GHz) are applicable. https://www.sharetechnote.com/html/5G/5G_Mib_Sib.html
31
The process that happens when you power on your phone.
Initial Attach https://www.sharetechnote.com/html/5G/5G_CallProcess_InitialAttach.html
32
The process wherein the UE (User Equipment) searches for nearby cells and acquires the synchronization signals (PSS and SSS) to synchronize with the gNB (gNodeB) timing.
Cell search and Synchronization https://www.sharetechnote.com/html/5G/5G_CallProcess_InitialAttach.html
33
Process of establishing radio resources.
RRC Connection Establishment
34
The Registration Request to AMF to register with the 5G network.
Network Registration
35
True or False: Authentication between UE and Network are bi-directional.
True
36
Security Setup: The UE and network establish security keys for secure communication. This happens in two phases (name both)
NAS security and RRC security
37
The process wherein AMF sends a Registration Accept message to the UE, confirming successful registration and providing configuration information such as the UE's 5G-GUTI (Globally Unique Temporary Identifier).
Network Acceptance
38
Network reconfigures RRC for the registered UE based on various UE capability.
RRC Reconfiguration
39
The process of establishing data pipe. UE initiate the process and network respond to the request and setting up the data pipe.
PDU Session Establishment
40
Two parts of synchronization between gNB and UE (in order)
Downlink synchronization first, then Uplink synchronization. Downlink Synchronization : the UE performs cell search and acquiring the synchronization signals, Primary Synchronization Signal (PSS) and Secondary Synchronization Signal (SSS), which help the UE to identify the cell and synchronize with its timing. Uplink Synchronization : This is achieved by RACH Process. The Random Access Channel (RACH) is used by the UE for initial uplink synchronization with the gNB. It involves transmitting a randomly chosen preamble from the UE, which the gNB detects and responds with a timing adjustment. This process enables the UE to align its transmission timing with the gNB, allowing for efficient communication. https://www.sharetechnote.com/html/5G/5G_CallProcess_InitialAttach.html
41
Once the security process is complete, sends a Registration Accept message to the UE, which includes the UE's 5G-GUTI (Globally Unique Temporary Identifier) and other relevant configuration information. The UE is now successfully registered with the 5G network.
AMF Access and Mobility Management Function
42
To establish a data session, the UE sends a PDU (Protocol Data Unit) Session Establishment Request message to . This message includes the UE's data session requirements, SSC Mode, PCO, DNN etc.
SMF Session Management Function
43
It is a mechanism to configure/divide a whole channel band into multiple segments and switch among the subbands depending on situation
BWP (BandWidth Part)
44
True or False: Minimum bandwidth of a BWP should be equal or less than SSB Bandwidth
False Minimum bandwidth of a BWP should be equal or larger than SSB Bandwidth https://www.sharetechnote.com/html/5G/5G_CarrrierBandwidthPart.html
45
Triggered when a neighbor cell's signal quality becomes better than the serving cell by a predefined offset. This is commonly used for handover decisions.
A3 (Neighbor Cell Becomes Better)
46
Triggered when the serving cell's signal quality surpasses a configured threshold.
A1 (Serving Cell Becomes Better)
47
Triggered when the serving cell's signal quality drops below a threshold.
A2 (Serving Cell Becomes Worse)
48
In ENDC (Eutra / NR Dual Carrier), becomes the MCG(Main Cell Group) and become SCG(Secondary Cell Group).
In ENDC (Eutra / NR Dual Carrier), Eutra (LTE) become MCG(Main Cell Group) and NR become SCG(Secondary Cell Group), meaning that LTE is main cell and NR just work as a secondary cell. https://www.sharetechnote.com/html/5G/5G_LTE_Interworking.html
49
True or False: In ENDC, Core Network is based on NR Core.
False In ENDC, Core Network is based on LTE Core, NR just provide additional RAN pipe. https://www.sharetechnote.com/html/5G/5G_LTE_Interworking.html
50
In ENDC, Downlink traffic is always split between LTE and NR, but there is two options for Uplink traffic. What does Option 1 means?
Option 1 : All the uplink goes through LTE only https://www.sharetechnote.com/html/5G/5G_LTE_Interworking.html
51
In ENDC, Downlink traffic is always split between LTE and NR, but there is two options for Uplink traffic. What does Option 2 means?
Option 2 : Uplink gets split between LTE and NR. The ratio of the split is configured by RRC https://www.sharetechnote.com/html/5G/5G_LTE_Interworking.html
52
True or False: When NR is added to the LTE cell, UE should be able to detect SSB of NR cell and perform RACH procedure to NR
True https://www.sharetechnote.com/html/5G/5G_LTE_Interworking.html
53
The interface between MN(Master Node : MeNB) and the SN (Secondary Node : En-gNB) for C-Plane
X2-C
54
The interface between MN and CN(Core Network : MME in this case).
S1-MME
55
There is an interface between MN(Master Node : MeNB) and the SN (Secondary Node : En-gNB) for U-Plane
X2-U
56
The interface between MN and CN(Core Network : S-GW) for U-Plane.
S1-U
57
The interface(connection) between SN and CN (S-GW) for U-Plane
S1-U
58
The interface(connection) between SN(gNB) and CN(MME) in C-Plane.
There is NO DIRECT connection between SgNB and MME. (this is a trick question ;)
59
This is a message from UE to BTS (either gNB or eNB) (MAC layer command) saying 'I have this amount of data to send would you give grants big enough to transmit all of these data ?"
Buffer Status report (BSR) As a formal definition, 38.321-5.4.5 states as follows : The Buffer Status reporting (BSR) procedure is used to provide the serving gNB with information about UL data volume in the MAC entity. https://www.sharetechnote.com/html/5G/5G_MAC_CE_BSR.html
60
This parameter identifies the center frequency for a set of SS/PBCH blocks.
GSCN (Global Synchronization Channel Number) To select an appropriate center frequency, the following two requirements should be fulfilled: - The Resource Blocks occupied by the SS/PBCH blocks must be completely within the channel bandwidth. - The SS/PBCH blocks must be subcarrier aligned with the RBs belonging to the channel bandwidth (BW). https://www.rfwireless-world.com/articles/5g/5g-nr-gscn-global-synchronization-channel-number https://www.sharetechnote.com/html/5G/5G_FR_Bandwidth.html#GSCN
61
Which coverage measurement is used to indicate the signal strength of the broadcast channel that affects the access and handover
SS-RSRP
62
Which coverage measurement is used to reflect the signal strength of the traffic channel
CSI-RSRP
63
In EN-DC, what is the limiting channel that makes the user fallback from 5G to LTE channel in C-Band (low-band 5G channel)?
PUCCH
64
In 5G CA, UL data and control are moved to the low 5G band channel to improve the 5G DL Throughput
True
65

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