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Mobile Networks > Data Transmission > Flashcards

Data Transmission Flashcards

1
Q

Mobile receives PDCCH

A

Every subframe, mobile reads control format indicator, establishes the size of DL control region , and locations of search spaces; process each PDCCH candidate

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2
Q

Mobile sends 3 types of uplink control info to BS

A

1) hybrid ARQ acks of BS DL transmissions
2) Uplink Scheduling Requests
3) Channel State information

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3
Q

CQI (channel quality Indicator

A

4 bit quantity which indicates the max data rate that the mobile can handle with a block error ratio of 10% or below

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4
Q

If BS does not reply to scheduling requests

A

After mobile reaches max number of sched requests w/o reply, triggers Rand Acc Proc

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5
Q

BS explicitly schedules all transmissions mobile carries out on?

A

physical uplink shared channel

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6
Q

If mobile wishes to transmit o PUSCH but does not have the resources to do so

A

it sends a scheduling request on physical uplink control channel; if doesn’t have resources for this, initiates random access procedure

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7
Q

1st step of Random Access

A

Mobile transmits a random access preamble on the physical access channel (PRACH)

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8
Q

Mobile receives what 3 things following rand access proc?

A

resources for an uplink transmission on the PUSCH, initial value ofr the uplink timing advance, C-RNTI

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9
Q

How does mobile read cell’s random access configuration?

A

From SIB 2

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10
Q

Persistant Scheduling Mode

A

UE can send data to network any time since network is sending UL Grant all the time

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11
Q

Steps of Non Persistent Scheduling

A

1) UE sends SR (Sched Req. on PUCCH)
2) Network sends UL Grant (DCI 0) on PDCCH
3) UE perform blind decoding - check PDCCH Search space and check if any info encoded with C_RNTI allocated
4) UE transmit PUSCH based on RBs specified by DCI 0
5) Network decodes it (knows the UL RB because it allocated it)

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12
Q

MIB carries what?

A

DL Bandwidth, number of transmit antenna, reference signal transmit power,
System Frame number (SFN), PHICH Configuration

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13
Q

HARQ

A

Works at Phy Layer but controlled by MAC layer
If received data has an error then the receiver buffers the data and requests a re-transmission from the sender; when receiver receives the retransmitted data, it combines it with buffered data prior to channel decoding and error detection

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14
Q

UL HARQ

A

HARQ is synchronous in the UL

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15
Q

PDCCH

A

physical channel that carries downlink control information (DCI)

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16
Q

PDCCH carries what

A

scheduling assignments (DCI 0 -uplink sched. assignment)

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17
Q

DCI stands for

A

Downlink control indicator

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18
Q

DCI answers what questions

A

Which resource block carries your data? What kind of demodulation scheme do you need to use to decode data?

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19
Q

DCI carries what information?

A

1) UL resource allocation (persistent and non-persistent)

2) Descriptions about DL data transmitted to the UE

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20
Q

BSR - Buffer Status Report

A

Provide NW with info about how much data in its buffer waiting to be transmitted

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21
Q

reference signal

A

UE uses to figure out DL power

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22
Q

Purpose of RACH

A

1) achieve up link synchronization between ue and eNB

2) obtain the resource for Message 3

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23
Q

Tracking Area Update

TAU

A

Registers the UE in the tracking area of the current cell

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24
Q

When is TAU invoked

A

UE mobility, periodic update, change in UE properties, MME load rebalancing, NAS signaling connection recovery

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25
Q

TAU if UE in ECM_CONNECTED state

A

already NAS signaling connection; UE sends Tracking area update req msg to eN using the ULInformation Transfer msg; eNB forwards to MME

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26
Q

If UE in ECM_IDLE state when TAU procedure inovked and MME changed

A

the new MME is updated with the UE context (UE ids, mobility state, security params) from the old MME

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27
Q

VNF (virtualized network functions)

A

one or more virtual machines with differing software functionality and process execution that replace custom hardware

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28
Q

Examples of network functions

A

modulations, coding, multiple access, ciphering

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29
Q

functional split

A

permits mapping of network functions to protocol layers and defining the placement of these layers w/in different NEs

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30
Q

Radio Bearer

A

transports control signaling or user data packets w/ common QoS between UE and eNB

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31
Q

2 types of radio bearer

A

signaling: Signaling Radio Bearer (SRB)

carry user data: associated w/ EPS bearer

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32
Q

default radio bearer

A

able to carry various types of traffic w/o QoS; typically created during attach proc

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33
Q

dedicated radio bearer

A

carries specific data flow identified by Traffic Flow Template (TFT) with a given QoS; est. during Attach or after

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34
Q

Ciphering applies to what msgs

A

NAS signaling, RRC signaling on SRB1 and SRB2, user plane data

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35
Q

Integrity Protection Aplies to:

A

NAS signaling msgs, control plane data, RRC signaling on SRB1 and SRB2

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36
Q

Ciphering and integrity applied after what?

A

activation of security for both NAS and AS, only when UE in RRC_CONNECTED, when SRB1 is establish (SRB0 has no ciphering or integrity)

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37
Q

EPS security context

A

state between UE and core network (CN)

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38
Q

EPS NAS security context

A

exists in RRC_IDLE and RRC_CONNECTED; stays valid when RRC connection related; use Kasme

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39
Q

EPS AS security context

A

only in RRC_CONNECTED state; when RRC connection established, a new EPS AS security context is set up

40
Q

AKA

A

LTE-EPS authentication and key agreement

41
Q

EPS AKA

A

provides mutual auth between UE and NW, establishes Kasme, takes place during attach proc and Tracking Area UPdate (TAU) proc

42
Q

Who initiates AKA proc?

A

Network always initiates, UE can reject

43
Q

Power on Sequence (mobile switches on)

A

1) mobile selects a public land mobile network (PLMN) that it will register with
2) mobile (optionally) ask user to select a closed subscriber group (CSG)
3) mobile selects cell that belongs to selected network and CSG

44
Q

In network selection proc, mobile selects what to register with?

A

public land mobile network (PLMN)

45
Q

If mobile can’t find registered PLMN in network/cell selection, it does hat?

A

scans all LTE carrier frequencies it supports and identifies networks it can find; find strongest LTE cell on each freq, read SIB and identifies network

46
Q

automatic network selection mode

A

mobile runs in priority order through a list of networks that it should treat as home PLMNs, runs cell selection proc when find network

47
Q

manual mode

A

mobile presents user with the list of networks that it has found, user then selects preferred network

48
Q

2 Parameters for RRC Connection Request

A

1) Non-access stratum (NAS) identity (S-TMSI) or random

2) establishment cause

49
Q

How does mobile send RRC Connection Request

A

Radio Bearer 0 (configuration for this sent by BS in SIB2); message sent on common control channgel, uplink shared channel, and physical uplink shared channel

50
Q

eNB response to RRC Connection Request

A

RRC Connection Setup

51
Q

What is in the RRC Connection Setup

A

configures mobile’s physical layer and mac protocols; PUCCH resources, time for buffer status reporsts, hybrid ARQ transmissions

52
Q

RRC Connection Setup Complete

A

mobile sends to eNB after receiving the RRC Connection Setup msg

53
Q

What’s in the RRC Connection Setup Complete msg?

A

1) Mobile identifies PLMN it would like to register with
2) Globally unique identity of MME previously serving mobile (extracted from GUTI)
3) EPS mobility management message that BS will forward to MME

54
Q

Objectives of Attach Proc

A

1) mobile registers location with a serving MME
2) NW configures signalling radio bearer 2, which carries NAS signalling
3) Network gives mobile an IP
4) NW sets up default EPS bearer

55
Q

IMEI

A

International Mobile Equipment Identity

56
Q

Update location request

A

new MME sends the mobile’s IMSI to the HSS

57
Q

User specific key K

A

1:1 mapping with IMSI

58
Q

User specific key k derives CK and Ik, which are used to derive what?

A

Kasme (access security management entity) key

59
Q

From Kasme, derive 3 further keys?

A

Knasenc, knasint, Kenb

60
Q

RRC_CONNECTED state

A

mobile is assigned to a serving eNB, and can freely communicate w/it using signalling msgs on SRB 1

61
Q

RRC_IDLE

A

radio access network knows nothing about the mobile, so no serving eNB is assigned and SRB 1 is torn down; RAN can still page mobile

62
Q

EMM Service Request

A

Mobile asks the serving MME to move it to ECM-CONNECTED

63
Q

SIM card

A

runs USIM, stores user info (phone number, home network id), carry out security calculations using secure keys

64
Q

mobile range of capabilities

A

max data, RATs supported, carrier frequencies they can transmit and receive

65
Q

S1 interface

A

base station connected to EPC

66
Q

S2 interface

A

base station to base station, used for signalling and packet forwarding during handover

67
Q

MME pool area

A

mobile can move without changing a serving MME

68
Q

M-TMSI

A

identifies a mobile to its serving MME

69
Q

MME communicates to mobile

A

through AS and NAS; the high-level signalling messages lie in the non-access stratum and are transported using the access stratum protocols

70
Q

MAC protocol

A

carries out low-level control of the physical layer, particularly by scheduling data transmissions between the mobile and base station

71
Q

radio link control (RLC) protocol

A

maintains the data link between the two devices

72
Q

What does PDCP stand for?

A

packet data convergence protocol

73
Q

What does PDCP do?

A

carries out higher-level transport functions that are related to header compression and security

74
Q

RRC protocol

A

base station controls a mobile’s radio communications by signalling

75
Q

MME controls’ a mobile’s high-level brehaviour using two protocols that lie in the air interface’s NAS

A

EPS session management

EPS mobility management

76
Q

EPS session management protocol

A

controls the data streams through which a mobile communicates with the outside world

77
Q

EPS mobility management protocol

A

handles internal bookkeeping w/in the EPC

78
Q

How does network transport EMM and ESM messages

A

embeds them into lower level RRC and S1-AP messages and then by using the transport mechanisms of the Uu and S1 interfaces

79
Q

Diameter protocol

A

HSS and MME

80
Q

UE capacity enquiry and response

A

serving eNB wishes to find out the mobile’s radio access capabilities

81
Q

What are RRC messages known as?

A

UL Information Transfer/DL Info Transfer

82
Q

What are S1-AP messages known as?

A

Uplink NAS transport and downlink NAS transport

83
Q

signalling radio bearers

A

carry signalling messages between the mobile and base station

84
Q

SRB 0

A

mobile and bs use to establish communications in RRC connection establishment; config defined in RRC messages known as system info messages which are broadcasted from eNB

85
Q

SRB 1

A

configured using messages exchanged on SRB0, transports some EMM and ESM message

86
Q

SRB 2

A

configured using signalling messages that are exchanged on SRB!, when mobile establishes communications with EPC - used to transport all of the remaining EMM and ESM messages

87
Q

3 parts of physical layer

A

transport channel processor - error management
physical channel processor - OFDMA, SC-FDMA, and multiple antenna transmission
analogue processor - radio frequ

88
Q

logical channel

A

data and signalling messages carried on these between RLC and MAC

89
Q

transport channel

A

between MAC and physical layer

90
Q

physical data channel

A

differnet levels of the physical layer

91
Q

where is control info created

A

in the transmitter by the transport channel processor

92
Q

Dedicated control channel

A

carries the mobile specific signalling messages on rignalling radio bearers 1 and 2 for mobiles in the RRC_CONNECTED state

93
Q

BCCH - broadcast control channel

A

carries RRC system info message; base station broadcasts to tell mobiles about cell configuration (SIBs and MIB)

94
Q

What does PCCH stand for?

A

paging control channel

95
Q

common control channel

A

carries messages on signalling radio beaer 0, for mobiles that are moving from RRC_IDLE to RCC_CONNECTED

96
Q

DRS

A

demodulation reference signal - mobile sends on uplink at same time as PUSCH and PUCCH as a phase reference for channel estimation

97
Q

SRS

A

mobile sends sounding reference signal for power reference at times configured by base station

Mobile Networks (2 decks)

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