lte channel state information

© 2012 Agilent Technologies

Wireless Communications

Greater insight. Greater confidence. Accelerate next-generation wireless.

LTE Channel State Information (CSI)

Presented by: Sandy Fraser, Agilent Technologies



2© 2012 Agilent Technologies



Agenda

Channel State Information (CSI) – different forms and definitions

• Channel Quality Information, Pre-Coding Matrix Indicator, Rank Indicator

• Terminology

CSI controls, formats and reports

Test Summary

Examine one test each for wideband CQI, frequency selective (sub-band) CQI, PMI and RI

What Agilent can do for CSI test!!

Summary

This presentation relies on the listener understanding a little MIMO, so we will “revise” a little as we go through the talk






The whole CSI concept

Channel conditions change – FACT!!

1) A UE moves from one area of good reception to an area with bad

reception

2) A UE is moving along a street with deep/wide fades and highly

variable radio conditions

3) We are sat at a café downloading our mail when a delivery truck

parks in our line of sight to the eNB

In all these case CSI takes care of the UE’s movement to a more robust

coding scheme, less puncturing, lower modulation depth, different

allocation in either frequency or time.

As in life, success is all in……………………timing !






Terminology I

Spatial MultiplexingThe process of transmitting data from multiple

antennas on the same frequency at the same time

Transmit DiversityTransmission of common data, but modified in some

way, on more than one antenna

ChannelThe entire route, from transmission to reception,

including all the analog & RF circuits & antennas,

that could introduce unwanted coupling or distortion

(Channel) RankThe number of useable data stream (layers) in a

multi-antenna radio system

CorrelationA measure of the similarity between different signals

(after the receiver antennas)

Condition NumberA short term measure of the increase in SNR needed

to recover a spatially multiplexed signal






Terminology II

Codeword The input data after basic adaptation from the payload

(Transmission) LayerWith spatial multiplexing, it is synonymous with a

stream

PrecodingThe process of cross coupling the signals before

transmission (used in closed loop operation) to

equalize the demodulated performance of the layers

CodebookThe look-up table of cross coupling factors used for

precoding; shared by the mobile and base-station

Closed Loop MIMOA mechanism used to continuously adapt the

transmitted signal to suit the channel characteristics,

using the precoder

BeamformingThe process of cross coupling the signals at

transmitter (or receiver) to adapt to the channel.

LTE precoding is one example of doing this

BeamsteeringWhen beamforming with phased array, it is the

process of tracking the movement of the mobile






Agenda

Channel State Information – different forms and definitions

• Channel Quality Information, Pre-Coding Matrix Indicator, Rank

Indicator

• Terminology


Test Summary

Examine one test each for wideband CQI, frequency selective (sub-

band) CQI, PMI and RI


Summary






Information required by UE to

transmit/receive

UE’s need to know a lot of information before sending or receiving data

ALL of this information is send from the eNB to the UE on the Downlink Control Information (DCI)

Uplink Downlink

When the UE can transmit and on which

resources

When the UE should “listen” for DL data. DL data

may not be contiguous in frequency

Which modulation, transport block size

and redundancy version to use

Which modulation, transport block size and

redundancy version were used to transmit this data

Adjustments to align timing with eNB Is this downlink spatially multiplexed

Whether to hop the PUSCH or not For Spatially multiplexed DL what pre-coding has

been applied

Power level Which HARQ process does this data belong to

Transmit new block or re-transmit

NACK’d blocks

Is this new data or re-transmitted data






Downlink Control Information

(DCI) formats

DCI Format Payload Usage

0 UL Assignments RB Assignments, TPC, MCS, PUSCH hopping flag

1 DL Assignments RB Assignments, TPC, HARQ, MCS

1A DL Assignments (compact) RB Assignments, TPC, HARQ, MCS, RA

1B DL Assignments (compact with pre-coding) RB Assignments, TPC, HARQ, MCS, TPMI, PMI

1C DL Assignments (VERY compact) RB Assignments

1D DL Assignments (compact with pre-coding and

power offset) – Multi user MIMO

RB Assignments, TPC, HARQ, MCS, TPMI, DL Power

offset

2 DL Assignments for closed loop MIMO RB Assignments, TPC, HARQ, MCS, pre-coding

2A DL Assignments for open loop MIMO RB Assignments, TPC, HARQ, MCS, pre-coding

2B DL Assignments for dual layer TM8 beamforming RB Assignments, TPC, HARQ, MCS, pre-coding

2C DL Assignments for dual layer TM9 8 layer non

codebook multiplexing (Rel10)

RB Assignments, TPC, HARQ, MCS, pre-coding

3 TPC commands for PUSCH and PUCCH with 2

bit power adjustments

Power control, e.g. USER1, USER2, USER….etc using

TPC-PUCCH-RNTI and TPC-PUSCH-RNTI

3A TPC commands for PUSCH and PUCCH with

single bit power adjustments

Power control, e.g. USER1, USER2, USER….etc using

TPC-PUCCH-RNTI and TPC-PUSCH-RNTI

4 UL Assignments for up to 4 layers, 2 per

codeword and pre-coding (Rel10)

RB Assignments, TPC, HARQ, MCS, pre-coding






DCI example

N6061A Protocol logging






HARQ Link Adaptation

Retransmissions of a particular HARQ process use the same modulation and

coding scheme as the initial transmission. Each subsequent retransmission

simply reduces the effective code rate through incremental redundancy –

there are 4 redundancy versions for LTE

Link adaptation (AMC: adaptive modulation and coding) with various

modulation schemes and channel coding rates can be applied to the shared

data channel.

AMC optimises the transmission performance of each UE while maximizing

the system throughput.

• If we use too low a modulation depth e.g. QPSK during good radio conditions, then

we are utilizing more bandwidth (for a given desired data rate) than we need to

• If we use too high a modulation depth in poor conditions, we end up with too many

re-transmissions

• Either way we are not making efficient use of the resources available

Channel STATE Indicator, which includes Channel Quality Indicator (CQI) is

the means by which the channel conditions are reported to the eNB to

optimise AMC process.






LTE 3GPP Channel Quality Indictor

(CQI) 36.213 section 7.2

CQI

indexmodulation

coding rate x

1024efficiency

0 out of range

1 QPSK 78 0.1523

2 QPSK 120 0.2344

3 QPSK 193 0.3770

4 QPSK 308 0.6016

5 QPSK 449 0.8770

6 QPSK 602 1.1758

7 16QAM 378 1.4766

8 16QAM 490 1.9141

9 16QAM 616 2.4063

10 64QAM 466 2.7305

11 64QAM 567 3.3223

12 64QAM 666 3.9023

13 64QAM 772 4.5234

14 64QAM 873 5.1152

15 64QAM 948 5.5547

36.213 Table 7.2.3-1: 4-bit CQI Table

• CQI reports can be

• Wideband or per sub-band

• Semi static, Higher Layer Configured or UE selected

single or multiple sub-bands

• CQI only, or CQI plus Pre-coding Matrix Indicator

(PMI) / Rank Indicator (RI)

• Transmitted on PUCCH for sub-frames with no PUSCH

allocation or PUSCH with or without scheduling grant or

if no UL-SCH

• Depends on spatial multiplexing

• Reports can be periodic or aperiodic (when signaled by

DCI format 0 with CQI request field set to 1)

• The eNB need not necessarily use the CQI reported

from the UE






Channel State Indication CSI on

Uplink Channel Information (UCI)36.213 Section 7.2

Transmission Mode Payload

1. Single-antenna

port; port 0

UE selected sub-band CQI + wide-band CQI or

Higher Layer Configured wide-band and sub-band CQI, no PMI

2. Transmit diversity UE selected sub-band CQI + wide-band CQI or


3. Open-loop spatial

multiplexing

UE selected sub-band CQI + wide-band CQI or


4. Closed-loop spatial

multiplexing

Wide-band CQI per codeword + PMI for each sub-band or

UE selected sub-band and wide-band CQI per codeword + PMI or

Higher Layer Configured wide-band and sub-band CQI + PMI

5. Multi-user MIMO Higher Layer Configured wide-band and sub-band CQI + PMI

6. Closed-loop

Rank=1 pre-coding

Wide-band CQI per codeword + PMI for each sub-band or

UE selected sub-band and wide-band CQI per codeword + PMI or

Higher Layer Configured wide-band and sub-band CQI + PMI

TM7, 8, 9 not listed






UCI on the PUCCH or PUSCH

Format Bits per

sub-frame

Payload Mod’n

1 N/A No Ack/Nack, only SR N/A

1a 1 SISO Ack/Nack BPSK

1b 2 MIMO Ack/Nack QPSK

2 20 CSI, no Ack/Nack QPSK

2a * 21 CSI + SISO Ack/Nack B/QPSK

2b * 22 CSI + MIMO Ack/Nack B/QPSK

Physical Uplink Control Channel (PUCCH) or Physical Uplink Shared Channel carries the

Uplink Control Information CQI and ACK/NACK, and also scheduling requests

* For normal CP only

The number and position of Demodulation Reference Signal symbols will vary

depending on format






UCI example – N6061A Protocol logging

Aperiodic CQI report

with PMI and RI

Periodic CQI report

combined with

ACK/NACK reporting






Agenda



Indicator

• Terminology


Test Summary




Summary






The mandated CSI tests36.521 section 9, 36.101 section 9

There are 18 CSI tests

• 10 for CQI testing (both wide-band and sub-band CQI)

• 6 for PMI testing

• 2 for RI testing

Almost all are COMPARATIVE tests – several stages with varying conditions –results compared to ensure throughput gain

Almost all require AWGN and Fading

NONE are truly representative of real world conditions.

All have separate FDD and TDD sections

7 are currently defined for Release 10 in 36.101 requirements (CSI reference symbols), but are not defined in the test procedures 36.521

These standards change regularly – this section last updated May 2012






36.521 Section 9

CSI Conformance Tests

Most requirements are tested using faded DL channels

Most are comparative tests, accomplished in several stages

Most employ fixed or minimally varied transmission conditions

Test Title and 3GPP 36.521

test referenceChannel

SNR options, test

countMode Description

CQI reporting under AWGN

9.2.1AWGN (1 x 2) 2,2 PUCCH 1-0

Comparison of BLER using CQImedian

+/-1 values


9.2.2AWGN (2 x 2) 2,2 PUCCH 1-1

Comparison of BLER for each

codeword using CQImedian +/-1 values


9.2.3

Defined in 36.101

(requirements), not in

36.521 (procedures)

Defined in 36.101


36.521 (procedures)

PUCCH 1-1CSI Reference Symbols – placeholder

R10 feature






Summary of test cases

continued - CQI

Test Title and 3GPP 36.521

test referenceChannel

SNR options, test


CQI Frequency-selective

scheduling

9.3.1.1

3GPP 36.101 Clause

B.2.4 with specific

fading conditions

2,2 PUSCH 3-0

Throughput with eNB random sub-band

allocation, then test with UE reported

sub-band allocation. Differential

minimum throughput gain ratio.


scheduling

9.3.1.2

Defined in 36.101


36.521 (procedures)

Defined in 36.101


36.521 (procedures)

PUSCH 3-1CSI Reference Symbols – placeholder

R10 feature

CQI Frequency non-

selective scheduling

9.3.2.1

EPA5, High 2,2

PUCCH 1-0 on

PUSCH to avoid

CQI and ACK

collisions

Compares Throughput using UE

reported CQI against fixed CQImedian

CQI Frequency non-

selective scheduling

9.3.2.2

Defined in 36.101


36.521 (procedures)

Defined in 36.101


36.521 (procedures)

PUCCH 1-1CSI Reference Symbols – placeholder

R10 feature


interference

9.3.3

Sub band size 6RB

3GPP 36.101 Clause

B.2.4 with specific

fading conditions

2,1 PUSCH 3-0





CQI UE-selected sub-band

9.3.4.1

Sub-band size 3RB

3GPP 36.101 Clause

B.2.4 with specific

fading conditions

2,2 PUSCH 2-0





CQI UE-selected sub-band

9.3.4.2

Sub-band size 6RB

3GPP 36.101 Clause

B.2.4 with specific

fading conditions

2,2

PUSCH 2-0

to avoid CQI and

ACK collisions











continued - PMI

Test Title and 3GPP

36.521 test referenceChannel

SNR options, test


Single PMI reporting

9.4.1.1EVA5, Low 2x2 1,1 PUSCH 3-1

Compares random pre-coding matrix

reported TP against UE reported pre-

coding matrix TP.


9.4.1.2EVA5, Low 4x2 1,1 PUCCH 2-1



coding matrix TP.


9.4.1.3

Defined in 36.101


36.521 (procedures)

Defined in 36.101


36.521 (procedures)


R10 feature

Multiple PMI reporting

9.4.2.1EPA5, Low 2x2 1,1 PUSCH 1-2



coding matrix TP.


9.4.2.2EVA5, Low 4x2 1,1 PUSCH 2-2



coding matrix TP.


9.4.2.3

Defined in 36.101


36.521 (procedures)

Defined in 36.101


36.521 (procedures)


R10 feature







continued - RI

Test Title and 3GPP

36.521 test referenceChannel

SNR options, test


Rank Indicator reporting

9.5.1.1EPA5, Low and high 2x2 1, 3

PUCCH 1-1

FDD Only

Compares TP with fixed rank, vs

reported rank for 3 separate channel

and rank conditions.


9.5.1.2EPA5, Low and high 2x2 1, 3

PUCCH 3-1

TDD Only

Compares TP with fixed rank, vs

reported rank for 3 separate channel

and rank conditions.


9.5.2.1

Defined in 36.101


36.521 (procedures)

Defined in 36.101


36.521 (procedures)

FDD onlyCSI Reference Symbols – placeholder

R10 feature


9.5.2.2

Defined in 36.101


36.521 (procedures)

Defined in 36.101


36.521 (procedures)

TDD onlyCSI Reference Symbols – placeholder

R10 feature






Wideband CQI Test With AWGN

(PUCCH format 1.0), 9.2.1

Parameter Unit Test 1 Test 2

Bandwidth MHz 10

PDSCH transmission mode 1

Downlink power

allocation

dB 0

dB 0

Propagation condition and antenna

configurationAWGN (1 x 2)

SNR (Note 2) dB 0 1 6 7

dB[mW/15kHz] -98 -97 -92 -91

dB[mW/15kHz] -98 -98

Max number of HARQ transmissions 1

Physical channel for CQI reporting PUCCH Format 2

PUCCH Report Type 4

Reporting periodicity ms NP = 5

cqi-pmi-ConfigurationIndex 6

Note 1: Reference measurement channel according to Table A.4-1 with one sided dynamic OCNG

Pattern OP.1 FDD as described in Annex A.5.1.1.

Note 2: For each test, the minimum requirements shall be fulfilled for at least one of the two SNR(s) and

the respective wanted signal input level.

A

B

)(ˆ j

orI

)( j

ocN

PUCCH 1-0 static test (36.101 [10] Table 9.2.1-1)






Wideband CQI Test With AWGN

(PUCCH format 1.0), 9.2.1

Setup with conditions stated and measure the median value of CQI

90% of all 2000 CQI results obtained must be within +/- 1 of this median value

Take this median CQI-1 value and measure BLER which must be less than 10%.

Take the median CQI +1 value and measure the BLER which must be greater than 10%.

If the UE fails this test using the first SNR value (0 dB), then the test sequence can be repeated using the second value (1 dB). The UE must pass at least one of these two tests. The test is then repeated for the SNR of 6dB, and if necessary 7dB.

Med CQI Med CQI+1Med CQI-1

Test part 2

with lower

than optimal

data flow

results in low

BLER (less

than 10%)

Test part 3

with higher

than optimal

data flow

results in high

BLER (greater

than 10%)

Establish

Median

CQI in test

part 1






Frequency

Time

Frequency Selective CSIWhat if?

What if I have been allocated the resources in RED

BUT my UE measures the PURPLE area to be more suitable for

the measured channel conditions?

What happens if the conditions have changed by the time the UE

is moved to these RB’s?

This is the purpose of sub-band (frequency selective) CSI testing






Frequency selective (sub-band)

scheduling CQI test with fading, 9.3.1.1

Parameter Unit Test 1 Test 2

Bandwidth MHz 10 MHz

Transmission mode 1 (port 0)

SNR (Note 3) dB 9 10 14 15

dB[mW/15kHz] -89 -88 -84 -83

dB[mW/15kHz] -98 -98

Propagation channel3GPP 36.101 Clause B.2.4 with specific

fading conditions

Correlation Full

Reporting interval ms 5

CQI delay ms 8

Reporting mode PUSCH 3-0

Max number of HARQ

transmissions1

Note 1: If the UE reports in an available uplink reporting instance at subframe SF#n based on CQI

estimation at a downlink subframe not later than SF#(n-4), this reported subband or wideband

CQI cannot be applied at the eNB downlink before SF#(n+4)

Note 2: Reference measurement channel according to Table A.4-4 with one/two sided dynamic OCNG

Pattern OP.1/2 FDD as described in Annex A.5.1.1/2

Note 3: For each test, the minimum requirements shall be fulfilled for at least one of the two SNR(s)

and the respective wanted signal input level.

)(ˆ j

orI)( j

ocN

Sub-band test for single antenna transmission (FDD) (36.101 [10] Table 9.3.1.1.1.3-1)






Frequency selective (sub-band)

scheduling CQI test with fading, 9.3.1

Gather 2000 CQI reports

The sub-band differential CQI offset level of 0 shall be reported at least a % of the time but less than b % for

each sub-band

Parameter Test 1 Test 2

a [%] 2 2

b [%] 55 55

γ 1.1 1.1

One sub-band may be different size to others – this one is not used because it could skew the throughput

results

Ignoring reports from the UE, the 2nd stage of the test allocates random subbands to the UE and tests

throughput.

The 3rd stage of the test uses the highest ranking sub-bands reported by the UE

The ratio of stage 2 and 3 should represent a throughput gain of more than 10% AND the BLER must be

greater than 5%.

If the UE fails this test using the first SNR value (9 dB), then the test sequence can be repeated using the

second value (10 dB), the UE must pass at least one of these two tests. The test is then repeated using the

SNR values 14 (and if necessary) 15dB.






So Tell (or Remind) Me

How does MIMO work?

1: Consider a moment in time, at a single frequency, and model the

channel as a box with fixed components inside:

2: Send a training signal first, that’s unique to A and to B. Measure

what comes out at C and D and therefore how they got coupled. [If

you know how they get coupled, you can work out how to uncouple them]

3: Everything going into the box will be coupled the same way, so

you apply what you found to the real data you want to sent

If we add two completely different

signals at A and B, they’ll get

mixed together, but in a precisely

defined way, dependant on the

values of Z1- Z4

A

BMIMO is used

uncouple signals

on twisted pairs

C

D






… and when does it not work?

Extreme example: If all the Z’s are the same, both

outputs are the same. This is a “keyhole” channel,

which does not support spatial multiplexing (rank =1)

A

B

Noise & interference always limit the modulation we use. With MIMO,

there is an ADDITIONAL factor – how well can you uncouple the

signals – measured by the Condition Number of the channel matrix

For every dB increase in

condition number, you

may need a dB increase

in the SNR

C

D






Why Precode (cross couple)

the SM signal?

No precoding – the layer

performance is unbalanced

Precoded to achieve

similar performance for

both layers






Precoding Matrix Index definition

3GPP TS 36.211 Table 6.3.4.2.3-1

Deals with FDD case

Only 3 (2 for TM4) choices

for spatial multiplexing (16

for the 4 layer case)

For single data stream

transmission, the precoding

produces beamsteering

(with 4 antennas)

Subband PMI reporting can

be configured down to the

resource block level






PMI Testing, 9.4.1.1

Parameter Unit Test 1

Bandwidth MHz 10

Transmission mode 6

Propagation channel EVA5

Precoding granularity PRB 50

Correlation and antenna configuration Low 2 x 2

Downlink power allocationdB -3

dB -3

dB[mW/15kHz] -98

Reporting mode PUSCH 3-1

Reporting interval ms 1

PMI delay (Note 2) ms 8

Measurement channel R.10 FDD

OCNG Pattern OP.1 FDD

Max number of HARQ transmissions 4

Redundancy version coding sequence {0,1,2,3}

Note 1: For random precoder selection, the precoder shall be updated in each TTI (1 ms granularity)

Note 2: If the UE reports in an available uplink reporting instance at subrame SF#n based on PMI

estimation at a downlink SF not later than SF#(n-4), this reported PMI cannot be applied at the

eNB downlink before SF#(n+4).

A

B

)( j

ocN

PMI test for single layer (FDD) (36.101 [10] Table 9.4.1.1.1.3-1)






PMI Testing, 9.4.1

The first stage of the test is performed in order to establish the value SNR(rnd). This is the Signal to Noise Ratio used during the second and third stages of the test.

36.101 Annex G.5.2 specifies how to establish the value SNR(rnd), by adjusting the SNR until the throughput is settled between 58% and 62% of the calculated maximum throughput t(rnd).

The second stage of the test is performed using random pre-coding

The third stage repeats stage 2 but using UE reported PMI values. Throughput results are obtained using these two different conditions, and the throughput ratio (γ ) is expressed as pre-coding gain

A pass is achieved if the ratio γ is exceeded.

Table 6.6-13. Minimum requirement (FDD) (36.101 [10] Table 9.4.1.1.1.3-2)

Parameter Test 1

γ 1.1

.






Rank Index

Only certain channel models are suitable for MIMO

If MIMO is used when the channel can only support 1 stream of data

the resulting throughput will be poor and resources wasted

If MIMO is NOT used when the channel CAN support more than one

stream, then the throughput will be low and resources wasted.






Rank Indication (RI) Testing, 9.5.1.1

Parameter Unit Test 1 Test 2 Test 3

Bandwidth MHz 10

PDSCH transmission mode 4

Downlink power

allocation

dB -3

dB -3

CodeBookSubsetRestriction

bitmap

000011 for fixed RI = 1

010000 for fixed RI = 2

010011 for UE reported RI

Propagation condition and antenna

configuration2 x 2 EPA5

Antenna correlation Low Low High

RI configurationFixed RI=2

and follow RI

Fixed RI=1

and follow RI

Fixed RI=2

and follow RI

SNR dB 0 20 20

dB[mW/15kHz] -98 -98 -98

dB[mW/15kHz] -98 -78 -78

Maximum number of HARQ

transmissions1

Reporting mode PUCCH 1-1 (Note 4)

Physical channel for CQI/PMI

reportingPUCCH Format 2

PUCCH Report Type for CQI/PMI 2

Physical channel for RI reporting PUSCH (Note 3)

PUCCH Report Type for RI 3

Reporting periodicity ms NP = 5

PMI and CQI delay ms 8

cqi-pmi-ConfigurationIndex 6

ri-ConfigurationInd 1

A

B

)( j

ocN)(ˆ j

orI

RI test (FDD) (36.101 [10] Table 9.5.1.1.3-1)

Note 1: If the UE reports in an available uplink

reporting instance at subframe SF#n

based on PMI and CQI estimation at a

downlink subframe not later than SF#(n-

4), this reported PMI and wideband CQI

cannot be applied at the eNB downlink

before SF#(n+4).

Note 2: Reference measurement channel

according to Table A.4-1 with one sided

dynamic OCNG Pattern OP.1 FDD as

described in Annex A.5.1.1.

Note 3: To avoid collisions between RI reports

and HARQ-ACK it is necessary to report

both on PUSCH instead of PUCCH.

PDCCH DCI format 0 shall be transmitted

in downlink SF#4 and #9 to allow periodic

RI to multiplex with the HARQ-ACK on

PUSCH in uplink subframe SF#8 and #3.

Note 4: The bit field for precoding information in

DCI format 2 shall be mapped as:

-For reported RI = 1 and PMI = 0 >>

precoding information bit field index = 1










Rank Indication (RI) Testing, 9.5.1

Test stage (a) establishes the value t(fix), Using the CodeBookSubsetRestriction for fixed Rank (1 or 2), the

system simulator responds with UL grants to the UE based on the CQI, RI, and PMI reports from the UE.

For test stage (b), the UE is then told to use the CodeBookSubsetRestriction as for UE reported RI shown in

table 6.6-14, along with all the other parameters to establish t(reported).

The ratio of the two throughput values γ obtained from the two test stages should satisfy the requirements

shown in table 6.6-15

Table 6.6-15. RI minimum requirements (FDD) (36.101 [10] Table 9.5.1.1.3-2)

Parameter Test 1 Test 2 Test 3

γ1 N/A 1.05 N/A

γ2 1.0 N/A 1.1

The first test should give very similar throughput values for the two test stages. Due to the low SNR value

there will be little or no improvement expected. The second test should show a modest throughput

improvement, but will still be restricted due to the use of R1 for both test stages, while test three will show the

highest improvement because of the highest SNR and use of fixed R2 for the first stage of the test.






Agenda



Indicator

• Terminology


Test Summary




Summary






AWGN and OCNG

Required for most section 7,8,9 tests

AWGN - Settable SNR for each RF1, RF2,

MIMO or Normal settings for channel mode

Indicated values for NoC and Noise Amplitude

Amp > AWGN

OCNG – defined in 36.521-1 section A.5

Fills any un-used RB’s with OCNG

Mode > BSE > Func > OCNG






Closed Loop TM4 and TM6 testingBSE>mode setup>more>RRC>TM Mode

QPSK

MCS 0-9

16QAM

MCS 10-16

64QAM

MCS 17-25

DL MCS

AUTO

1

RI

AUTO

2

0

PMI

AUTO

1

3

2

CQIPMIRI

CHANNEL

EMULATOR

• BLER/Tput Testing

• Supports Test Mode

and E2E Testing

• Open Loop and Closed

Loop Testing

• Display CQI/RI/PMI

reported information






Comprehensive Throughput Reporting

DL and UL

throughput graphs

and values

Average throughput,

BLER, ACK, NACK

and StatDTX counts

New tab for channel

state information

(CQI, PMI, RI etc)






CSI ReportingCSI = channel state information – includes CQI, PMI, RI

New tab for channel state information (CQI, PMI, RI etc)

Wideband and sub-band reports

PMI, RI reports

Periodic, Aperiodic reporting (depends on scenario and front panel settings

36.521 section 9 automatic reports and measurements






Differential CQI reported values






CQI reporting for 36.521 Section 9CSI = channel state information – includes CQI, PMI, RI

Statistical CQI Performance

The Statistical CQI Performance measurement is used as part of

an RCT system to perform test cases in 36.521-1, section 9.

Mode > BSE > Func > More > RCT > Statistical CQI

Performance

Median CQI

This setting starts/initiates the collection of CQI reports from UE.

Aperiodic CQI, Periodic CQI

The scenario must contain the appropriate CQI Report

Configuration (either periodic or aperiodic) in the RRC Setup

message information. This enables the UE to generate the

correct CQI reports.

Mode > BSE > Func > More > CQI Median

DL Allocation based on CQI

Set the DL allocation to whatever the UE is reporting

Choose from Wideband or Sub-band and random Sub-band

Mode > BSE > Mode Setup > More > PHY > DL Resources >

CQI Reports






Sweep out

Trig

Out Pulse

Trig In

Ext Trig 1 In

E6621A PXT

(eNodeB emulator)

N9020A MXA Signal Analyzer

N5182A MXG Vector

Signal Generator

Does the CQI feedback

process act fast enough?

CQI Control Loop Testing

50ms noise bursts added to downlink






Testing CQI Using UE Reporting

(Delayed ) drop in

MCS in response to

CQI report from UE

HARQ retransmissions

occur throughout the

noise burst

2 frame quantisation

in response set by

reporting interval

Over-damped control loop

response showing impact

of reporting interval and

CQI UE report averaging






Testing CQI Using UE Reporting

Periods of StatDTX (No ACK’s or

NACK’s indicating no reception by

UE or no report sent by UE

Random re-transmissions and RV’s






Summary

LTE CSI testing is more involved than originally for W-CDMA

18 tests, FDD/TDD = 36, multi-steps = more than 100 test steps

Testing requires very specific setting capability in test equipment

Testing is largely static with fixed I_MCS, although using faded

conditions this does not represent the real world use case.

• Real world type testing may be required to ensure end user satisfaction.

• Fixed channel testing will be required to debug persistent throughput or

CSI reporting issues






Resources

Webcast for more detailed description of analysis using VSA software http://www.eetimes.com/electrical-engineers/education-

training/webinars/4211278/How-To-Verify-the-Data-In-Your-LTE-Uplink-Signal

Agilent VSA site: www.agilent.com/find/vsa

This webcast was recorded and will be available shortly along with the

slides

Everything related to the PXT network emulator including Radio (pre-)

Conformance testing www.agilent.com/find/pxt

Application notes, white papers, demonstrations, webcasts, training

events, related products and MUCH more: www.agilent.com/find/MIMO

http://www.eetimes.com/electrical-engineers/education-training/webinars/4211278/How-To-Verify-the-Data-In-Your-LTE-Uplink-Signal


























http://www.agilent.com/find/vsa

http://www.agilent.com/find/pxt

http://www.agilent.com/find/MIMO






Backup slides




BACKUP SLIDES - LTE - MIMO






Agenda

• Overview of Multi-antenna techniques

• LTE Terminology

• How MIMO works in LTE

LTE RF Design and Measurement Course






Multi-Antenna Techniques in LTE

• Just because there is more than one antenna, doesn’t mean it’s

MIMO

• Diversity can usefully be combined with MIMO Spatial Multiplexing to

improve performance

• A focus on the need to provide an increased DL data rate leads to an

asymmetric system in LTE






System & Antenna Configurations

Terms

SISO

Tx Rx

SIMO

Tx Rx0

Rx1

MISO

Tx0 Rx

Tx1

MIMO

Tx0

Tx1

Rx0

Rx1

“Input” and “Output” Refer to the Channel

Rx Diversity

Tx Diversity, Beamforming

Spatial Multiplexing






Terminology I

Spatial MultiplexingThe process of transmitting data from multiple

antennas on the same frequency at the same time

Transmit DiversityTransmission of common data, but modified in some

way, on more than one antenna

ChannelThe entire route, from transmission to reception,

including all the analog & RF circuits & antennas,

that could introduce unwanted coupling or distortion

(Channel) RankThe number of useable data stream (layers) in a

multi-antenna radio system

CorrelationA measure of the similarity between different signals

(after the receiver antennas)

Condition NumberA short term measure of the increase in SNR needed

to recover a spatially multiplexed signal






MIMO Spatial Multiplexing and Diversity

Both Important, Different Objectives

Multiple Antennas can be used in a variety of ways:

• Beamforming

• Transmit Diversity

• Receive Diversity

Diversity techniques protect against fading, and improve

coverage







Double Diversity does not make MIMO

Transmit Diversity + Receive Diversity = Spatial Multiplexing

MISO plus MRC

Rx0

Rx1

Tx0

Tx1

MIMO

Data modified and repeated on

second symbol (or subcarrier)

Data only transmitted once

Tx0

Tx1

Tx0

Tx1






MIMO Operation in LTE

In the Uplink, two mobiles are

used together to create the MIMO

signal.

Known as Multi-User MIMO

In the Downlink, it’s normally like

WLAN, the MIMO transmission is

sent to a single mobile.

Known as Single User MIMO







Terminology II

Codeword The input data after basic adaptation from the payload

(Transmission) LayerWith spatial multiplexing, it is synonymous with a

stream

PrecodingThe process of cross coupling the signals before

transmission (used in closed loop operation) to

equalize the demodulated performance of the layers

CodebookThe look-up table of cross coupling factors used for

precoding; shared by the mobile and base-station

Closed Loop MIMOA mechanism used to continuously adapt the

transmitted signal to suit the channel characteristics,

using the precoder

BeamformingThe process of cross coupling the signals at

transmitter (or receiver) to adapt to the channel.

LTE precoding is one example of doing this

BeamsteeringWhen beamforming with phased array, it is the

process of tracking the movement of the mobile






So Tell (or Remind) Me

How does MIMO work?

1: Consider a moment in time, at a single frequency, and model the

channel as a box with fixed components inside:

2: Send a training signal first, that’s unique to A and to B. Measure

what comes out at C and D and therefore how they got coupled. [If

you know how they get coupled, you can work out how to uncouple them]

3: Everything going into the box will be coupled the same way, so

you apply what you found to the real data you want to sent

If we add two completely different

signals at A and B, they’ll get

mixed together, but in a precisely

defined way, dependant on the

values of Z1- Z4

A

BMIMO is used

uncouple signals

on twisted pairs

C

D






… and when does it not work?

Extreme example: If all the Z’s are the same, both

outputs are the same. This is a “keyhole” channel, which

does not support spatial multiplexing (rank =1)

A

B

Noise & interference always limit the modulation we use. With MIMO,

there is an ADDITIONAL factor – how well can you uncouple the

signals – measured by the Condition Number of the channel matrix

For every dB increase in

condition number, you

may need a dB increase

in the SNR






LTE Channel Training SignalsThe Reference Signals are what allow the receiver to calculate the channel coefficients. They NEVER overlap before they are t ransmitted

0l

0R

0R

0R

0R

6l 0l

0R

0R

0R

0R

6l

One

ante

nna

port

Tw

o a

nte

nna

port

s

Resource element (k,l)

Not used for transmission on this antenna port

Reference symbols on this antenna port

0l

0R

0R

0R

0R

6l 0l

0R

0R

0R

0R

6l 0l

1R

1R

1R

1R

6l 0l

1R

1R

1R

1R

6l

0l

0R

0R

0R

0R

6l 0l

0R

0R

0R

0R

6l 0l

1R

1R

1R

1R

6l 0l

1R

1R

1R

1R

6l

Four

ante

nna

port

s

0l 6l 0l

2R

6l 0l 6l 0l 6l

2R

2R

2R

3R

3R

3R

3R

even-numbered slots odd-numbered slots

Antenna port 0


Antenna port 1


Antenna port 2


Antenna port 3






What makes a good channel for MIMO?

A perfect MIMO channel:

By simple observation it follows that R0 = T0 and R1 = T1

This is a case that creates double the capacity

1 0

0 1

Channel H

0.8 0.2

0.3 -0.9

Channel H

h00

h11

T0

T1

R0

R1

But suppose we create a simple

static channel like this:

How do we know if it will provide

capacity gain?






The MIMO challenge

Recovering the signal

So is the earlier example good or bad for MIMO?

We can recover the original signal

In fact any H matrix other than the unity matrix can be resolved PROVIDED there is no external or internal noise!

0.8 0.2

0.3 -0.9

Channel HR0 = 0.8 T0 + 0.3 T1

R1 = 0.2 T0 - 0.9 T1

T0 = 1.15 R0 + 0.39 R1

T1 = 0.26 R0 - 1.03 R1

Giving:






Why Precode (cross couple)

the SM signal?

No precoding – the layer

performance is unbalanced

Precoded with 1,1,-1,1 –

similar performance for

both layers






Precoding Matrix Index definition

3GPP TS 36.211 Table 6.3.4.2.3-1

Deals with FDD case

Only 3 choices for spatial

multiplexing (16 for the 4

layer case)

For single data stream

transmission, the precoding

produces beamsteering

(with 4 antennas)

Subband PMI reporting can

be configured down to the

resource block level






Antenna influence on performance

The dynamic condition number example did not isolate effects from different components, including the antenna

In real life, the instantaneous channel matrix H is made up from the interaction of three components:

• The static 3D antenna pattern of the transmitter

• The dynamic multipath and Doppler characteristics of the radio channel

• The static 3D antenna pattern of the receiver

The overall antenna contribution is the product of the transmit and receive antennas known as the channel correlation matrix






Real life performance

Variation due to fading and variable interference

Variation due to

instantaneous

correlation

Most macrocell

activity takes

place in this

region

Variation in the

frequency

domain not

shown






Summary

MIMO Spatial Multiplexing is a powerful additional transmission scheme in the right conditions

The list of 7 modes for DL transmission highlights how the ENB and UE will have to work together to choose which multi-antenna technique to use:

LTE has seven different downlink transmission modes:

1.Single-antenna port; port 0 SISO

2.Transmit diversity MISO

3.Open-loop spatial multiplexing MIMO – no precoding

4.Closed-loop spatial multiplexing MIMO – with precoding

5.Multi-user MIMO MIMO - separate UE (for UL)

6.Closed-loop Rank=1 precoding MISO - beamsteering

7.Single-antenna port; port 5 MISO – beamsteering

lte channel state information

Documents