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Short review review of fo llow ing features: features: LTE10, LTE11, LTE571 Nidia Couto -
[email protected] The latest version of this NEI can be found here
For internal use
Main Ma in Me Menu nu
LTE10 LT E10 - EPS beare bearers rs for c onversational voice
LTE1 LT E11 1 - Robust Header Header Compressio n
LTE57 LT E571 1 - Controlled UL packet segmentation
RL20 - LTE10 - EPS bearers for conversational voice Table of Cont ents
1 2 3
Introduction Motivation and Feature Overview
4
Configuration Management
5
Dimensioning Aspects
6
Performance Aspects
Parameters
Interdependencies Interdependencies with Other Features and Functions Dimensioning Impacts and Examples
Technical Details Functionality and Implementation, Message Flows Counters and KPIs
NEI Contact: Nidia Couto / Dawid Czarnecki
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Techni cal Details
Table of Contents
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LTE10 - EPS bearers for conversational voice - IMS signaling
IMS – IP Multim edia Subsystem IP Multimedia Subsystem is an access-independent architecture that enables various types of multimedia services to mobile-users using common Internet-based protocols.
• Two new QCI bearers: ─ QCI1 bearer for transmission of voice packets ─ QCI5 bearer dedicated for IMS signaling
• O&M switch (schedulType) allows to define whether QCI5 bearer carries IMS signaling or not ─ If IMS signaling is not specified for QCI5, the bearer is weighted according to QCI-specific relative weight (schedulWeight on qciTab5)
If schedulType is not set for signaling, QCI5 is weighted as a regular bearer
Techni cal Details
Table of Contents
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LTE10 - EPS bearers for conversational voice – Impacts on RRM
• To ensure QoS for voice calls, both target bit rate and delay have to be maintained ‒
The Flexi BTS takes the GBR signaled via S1 interface into account for Radio Resource Management (Admission Control and Scheduler ).
The maximum GBR for EPS bearers with QCI 1 is limited by qci1GbrLimit (default: 250kbps). EPS bearers with GBR value higher than this will be rejected by eNB.
• Admission Control ‒
•
Due to QoS restrictions, two new thresholds for GBR bearers are introduced to radio admission control
GBR threshold for new calls: maxNumQci1Drb
GBR threshold for incoming calls: addNumQci1DrbRadioReasHo, addNumQci1DrbTimeCriticalHo
Scheduler ‒
Dynamic scheduling is applied for EPS bearers with QCI 1
‒
The uplink and downlink scheduler use the GBR delay budget for its scheduling decisions. The delay budget can be configured by the operator (delayTarget, schedulBSD, schedulWeight)
‒
Non-GBR data transmission might be reduced in order to achieve the GBR for voice users
‒
Voice service (as based on GBR bearers) is not subjected to rate capping functions
Configuration Management
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LTE10 – Parameters related to Radio Admission Control
O&M thresholds for RAC interaction with BM and MM for 10 MHz* MOC
Modifiable by
Abb reviat ed name
Values
Descr ipt ion
LNCEL
Operator
maxNumQci1Drb
range: 0-400, step: 1 default: 100 (for 10MHz band)
LNCEL
Operator
addNumQci1DrbRadioReasHo
range: 0-400, step: 1 default: 15 (for 10MHz band)
Additional margin for the maximum number of active GBRs in the cell accessing the cell via handover with HO-cause "HO desirable for radio reasons". This margin is added to the threshold maxNumQci1Drb.
LNCEL
Operator
addNumQci1DrbTimeCriticalHo
range: 0-400, step: 1 default: 20 (for 10MHz band)
Additional margin for the maximum number of active GBRs in the cell accessing the cell via hand over with HO-cause: "Time Critical HO". This margin is added to the threshold maxNumQci1Drb .
QCI1-specific parameters for different bandwidths
Carrier BW
20 MHz
15 MHz
10 MHz
5 MHz
max PRBs
100 PRBs
75 PRBs
50 PRBs
25 PRBs
used PRBs for UL-signaling (PUCCH)
19 see RRM.2691
17 see RRM.2691
10 see RRM.2691
8 see RRM.2691
Parameter
Values for RL40. For earlier releases the number of QCI1 DRBs is limited to 150 in 5MHz and 200 in other BWs.
Threshold for the maximum number of established QCI1-GBR-DRBs in the cell
range, step size
default value
range, step size
default value
range, step size
default value
range, step size
default value
maxNumQci1Drb
0…600 step 1
100
0…500 step 1
100
0…400 step 1
100
0…200 step 1
75
addNumQci1DrbRadioReasHo
0…600 step 1
40
0…500 step 1
30
0…400 step 1
15
0…200 step 1
15
addNumQci1DrbTimeCriticalHo
0…600 step 1
40
0…500 step 1
30
0…400 step 1
20
0…200 step 1
15
LTE10 – Coverage Aspects No impact on coverage – Using retransmissions , HARQ gain can bring ~5dB improvement in LiBu
GSM/LTE RF sharing at 1800 MHz
• Only UL considered (limiting link) • Short retransmission delay in LTE allows for several
HARQ retransmissions within acceptable delay budget (50..70ms total packet delay at the air interface) – With the cost of reducing capacity as each retransmission will require a new scheduler allocation.
• Lowering AMR codec rate will also increase the cell range
Results slightly worse than GSM (7dBm higher power). Further improvement can be achieved after considering the gains of packet segmentation and TTI bundling in future releases.
•
Gain from RoHC already included in the calculations
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LTE10 – Capacity Aspects
Table of Contents
No impact on Cell Throughput – Number of UEs limited due to PDCCH resources
VoIP capacity example: Ass um pt io ns • • • •
VoIP codec AMR12.2 10MHz BW 3 PDCCH symbols PDCCH Alpha = 0.8
• Due to the big number of small packets being sent, the
bottleneck for VoIP users is not on on U-Plane, but on CPlane – Each allocation requires a PDDCH grant – For non cell edge users, grants can be reduced by
–
HARQ Gain (3 retransmissions)
aggregating multiple packets (max 3, subjected to delay target) and sending them all at once For user at the cell edge, each retransmission requires a separate PDCCH grant, reducing the number of supported users Alt ho ug h more r etrans mi ss io ns im prove robustness and coverage, increased PDCCH usage may lead to VoIP capacity degradatio n. Such calculations can be performed
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RL20 - LTE11 - Robust Header Compression Table of Cont ents
1 2 3
Introduction Motivation and Feature Overview
4
Configuration Management
5
Benefits and Gains
6
Dimensioning Aspects
Parameters
Interdependencies Interdependencies with Other Features and Functions
Simulation, Lab and Field Findings
Technical Details Functionality and Implementation, Message Flows
Dimensioning Impacts and Examples
NEI Contact: Nidia Couto / Dawid Czarnecki
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Introduction
Table of Contents
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LTE11 - Robust Header Compression
• The robust header compression (RoHC) function compresses the header of IP packets for the EPS bearer with QCI 1 320bits
• RoHC is supported for IPv4 and IPv6. • The following RoHC profiles are supported (3GPP R8): ‒ ROHC uncompressed (RFC 4995) ‒ ROHC RTP (RFC 3095, RFC 4815) ‒ ROHC UDP (RFC 3095, RFC 4815) ‒
Those RoHC profiles must be supported by all IMS-voice capable UEs (3GPP TS 36.306)
• Operation takes place between 3rd and 2nd OSI layer
24bits
40bits
244bits
Techni cal Details
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LTE11 - Robust Header Compression – Exemplification
Uncompressed transmission IP/UDP/RTP header consisting of predictable and unpredictable fields subjected to compression
MAC header, RLC header, VoIP payload, CRC checksum - not subjected to compression
Compressed transmission
x
10.0.0.10
10.0.0.10
6
10.0.0.10
3
3
10.0.0.10
7
7
10.0.0.10
0
0
10.0.0.10
1
1
10.0.0.10
8
8
Field predictable in the course of transmission – “Destination IP”
Unpredictable field
Initial transmission, “context” is initialized so that next transmissions can be compressed
“from now on assume Destination IP is 10.0.0.10”
Context - information about all fields that are predictable and their change patterns sent in the beginning of transmission to allow header compression
6
In the course of transmission header fields initialized in context do not have to be transmitted
Benefits and Gains
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LTE11 - Robust Header Compression – Exemplary Call
10 minutes of 12.2 kbps AMR coded VoIP call wit h talk spu rt/silent p eriod alternating every 1 second (SID packets excluded) ROHC header type
ROHC header bits
Samples
Samples [%]
To initialize the context of the decompressor
504
8
0,01%
To initialize the dynamic part of the context
120
1500
1,00%
To signal 6 LSBs of RTP Sequence Number
24
118961
79,31%
To update reference value of RTP SN
32
17625
11,75%
To signal more LSBs of the RTP SN
40
6000
4,00%
R-2-Ext3
Sent when compressor does not receive ACK for R-0-CRC
56
1500
1,00%
R-0-ACK
Used by decompressorto acknowledge received R-0-CRC or R-2-Ext3 packets
40
4406
2,94%
150000
100,00%
IR IR-DYN R-0 R-0-CRC R-2
Field description
TOTAL
Uncompressed header volume
Compressed header volume
IPv4/UDP/RTP packet overhead is 40 bytes
RoHC headers sizes are given in the table
15000 packets x 40B x 8b = 4.8 x 107 bits
504 x 8 + 120 x 1500 + … + 40 x 4406 = 4.1 x 106 bits
For this exemplary transmission , the overhead is r educed by 91.5% Source:
Representative transmission
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LTE11 - Robust Header Compression
RoHC Header Size Distribution 100% 100%
98% 95%
98% of RoHC headers si ze is smaller or equal to 40 bits
80% 90%
60% F D P
F D C
40%
85%
20%
80%
0% 504
120
24
32
40
RoHC header si ze [bits]
56
40
75% 24
32
40
56
RoHC header size [bits]
For link budget purp oses RoHC header size is assumed to be 40 bits
120
504
Dimensioning Aspects
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LTE11 - Robust Header Compression – Impact on Coverage
RL20@10MHz(12.2 kbps, no RoHC) • •
•
• • •
RL20@10MHz(12.2 kbps, RoHC) • •
Enhanced Pedestrian A 5Hz (EPA05) Equipment parameters: – Tx Power: eNB 40W / UE 23 dBm eNB 18 dBi / UE 0 dBi – Antenna Gain: – Feeder Loss: DL 0.4 dB / UL 0.4 dB (feederless) – Noise Figure: eNB 2.2 dB / UE 7 dB Other features: – eNB: 2 Tx antennas, 2 Rx antennas (2x2 MIMO) – UE: 1 Tx antenna, 2 Rx antennas (MRC) – DL F-domain Scheduler: channel-aware – UL F-domain Scheduler: channel-unaware Additional margins: – Interference margin for 50% load (~ 1…2dB) – 2.5 dB gain against shadowing IP/UDP/RTP header - 320 bits TTI bundling – off
DL 171 dB*
•
• • •
Enhanced Pedestrian A 5Hz (EPA05) Equipment parameters: – Tx Power: eNB 40W / UE 23 dBm eNB 18 dBi / UE 0 dBi – Antenna Gain: – Feeder Loss: DL 0.4 dB / UL 0.4 dB (feederless) – Noise Figure: eNB 2.2 dB / UE 7 dB Other features: – eNB: 2 Tx antennas, 2 Rx antennas (2x2 MIMO) – UE: 1 Tx antenna, 2 Rx antennas (MRC) – DL F-domain Scheduler: channel-aware – UL F-domain Scheduler: channel-unaware Additional margins: – Interference margin for 50% load (~1…2dB) – 2.5 dB gain against shadowing RoHC header - 40 bits TTI bundling - off
UL 150 dB*
DL 171.5 dB*
UL 153 dB*
Propagation •
Operating Band – FD-LTE:
• 2100 MHz
3dB gain due to less bandwidth needed per user (lower MCS used) * Max allowable path loss (clutter not considered, only system gains/losses)
•
COST 231 Hata 2-slope propagation model with – Antenna height NB: 30m – Antenna height MS: 1.5m Clutter dependent figures (Dense Urban / Urban / Suburban / Rural) – Std. dev.: 9 / 8 / 8 / 7 [dB] 94.4 / 94.0 / 94.0 / 89.9 [%] – Cell area prob.:
RL30 - LTE571 - Controlled UL packet segmentation Table of Cont ents
1
Introduction
2
Interdependencies
3
Motivation and Feature Overview
Interdependencies with Other Features and Functions
4
Configuration Management
5
Dimensioning Aspects
Technical Details
Parameters
Functionality and Implementation, Message Flows
Dimensioning Impacts and Examples
NEI Contact: Nidia Couto / Dawid Czarnecki
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Introduction
Table of Contents
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LTE571 - Controlled UL packet segmentation
• Packet Segmentation Algorithm is used as an extension to
RLC
16b
MAC
Link Adaptation for Uplink coverage improvement ‒ The enhancement in coverage comes at the cost of cell
Higher overhead
1/2
throughput L2 SDU 304b
‒ Due to increased number of time allocations per packet, PDCCH load also increases
Packet segmentation
• Packet segmentation is not an event-triggered mechanism, it is done automatically and only for UEs with poor radio channel ‒ LTE571 is simply an enhancement to the existing, nonconfigurable packet segmentation mechanism on Layer 2
m+1
Total energy per packet = 22.67dBm
RLC
RLC
MAC
MAC
L2 SDU 152b
L2 SDU 152b
16b
Padding Padding
Padding
m
2/2
TTIs
m
m+1
m+2
Total energy per packet = 25.37dBm
Increased robustness by spreading the packet in time domain
TTIs
Packet Segmentation when LTE571 is disabled
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LTE571 - Controlled UL packet segmentation
What happens with allocation when UE conditions are getting worse (LTE571 di sabled) 1.
Initially user is in good radio conditions so there’s no need for segmentation. It occupies the minimum number of PRBs needed to transmit its data with given MCS
2.
As radio conditions worsen, AMC decreases MCS order and, consequently, more PRBs are occupied
3. 4.
MAX_NUM_PRB (from ATB) is reached and whole packet can no longer be sent at once
5. 6. 7.
Packet is segmented. Original packet size is split into 2 packets (240b and 64b plus header). First part is sent with limit from ATB (256b TBS), second part with the lowest possible number of PRBs to ensure transport of 80b packet (144b TBS, remaining filled with padding).
9.
• •
RLC SDU size = 304 bits RLC + MAC header = 16 bits
Without LTE571, allocation of single PRB is allowed. This way only headers are transmitted
I TBS
MAX_NUM_PRB (from ATB)
N PRB 1
2
3
4
0
16
32
56
88
120
152
176
208
1
24
56
88
144
176
208
224
256
2
32
72
144
176
208
256
296
328
3
40
104
176
208
256
328
392
440
– 1 segment
4
56
120
208
256
328
408
488
552
– 2 segments
5
72
144
224
328
424
504
600
680
number of PRBs, increasing segmentation
– 3 segments
6
88
176
256
392
504
600
Packet will be segmented as much as needed to fit into the
– 5 segments
7
104
224
328
472
584
712
840
968
available allocation.
– 8 segments
8
120
256
392
536
680
808
968
1096
– 19 segments
9
136
296
456
616
776
936
1096 1256
– headers only
10
144
328
504
680
872
1032
1224 1384
As radio conditions worsen MCS order drops (AMC) and PRB usage increases Further increase of #PRBs not possible - MAX_NUM_PRB (from ATB) would be exceeded. Segmentation needed. Worsening radio conditions Packet is segmented again – 304 bits are distributed into 3 segments (2 segments of 152b and 1 segment of 56b).
8.
Ass um pt io ns
As MCS cannot be further decreased, ATB has to reduce the
10. Once MAX_NUM_PRB is reduced to 1, UE will send only RLC+MAC headers and no data
5
6
7
8
MAX_NUM_PRB 712 808 (from ATB)
Packet Segmentation when LTE571 is enabled
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LTE571 - Controlled UL packet segmentation
What happens with allocation when UE conditions are getting worse (LTE571 enabled) 1.
Initially user is in good radio conditions so there’s no need for segmentation. It occupies the minimum number of PRBs needed to transmit its data with given MCS
2.
As radio conditions worsen, AMC decreases MCS order and, consequently, more PRBs are occupied
3. 4.
MAX_NUM_PRB (from ATB) is reached and whole packet can no longer be sent at once Packet is segmented. Original packet size is split into 2 packets (240b and 64b plus header). First part is sent with limit from ATB (256b TBS), second part with the lowest possible number of PRBs to ensure transport of 80b packet (144b TBS, remaining filled with padding).
Ass um pt io ns • •
RLC SDU size = 304 bits RLC + MAC header= 16 bits
LTE571 stablishes a New parameters introduc ed minimum TBS and PRB number to control generated• ulsMinTbs = 72 bits • ulsMinRbPerUe = 4 overhead MAX_NUM_PRB (from ATB) N I TBS
PRB
1
2
3
4
0
16
32
56
88
120
152
176
208
Further increase of #PRBs not possible - MAX_NUM_PRB (from ATB) would be exceeded. Segmentation needed.
1
24
56
88
144
176
208
224
256
7.
2
Packet is segmented again – 304 bits are distributed into 3 segments (2 segments of 152b and 1 segment of 88b). 40b padding need to be added to fulfill ulsMinTbs.
32
72
144
176
208
256
296
328
3
40
104
176
208
256
328
392
440
8.
As MCS cannot be further decreased, ATB has to reduce the
4
56
120
208
256
328
408
488
552
5
72
144
224
328
424
504
600
680
6
88
176
256
392
504
600
5. 6.
As radio conditions worsen MCS order drops (AMC) and PRB usage increases
number of PRBs, increasing segmentation
9.
Worsening radio conditions
Once the minimum number of PRBs is reached
5
6
7
8
MAX_NUM_PRB 712 808 (from ATB)
(ulsMinRbPerUe > MAX_NUM_PRB), no further
– 1 segment
7
104
224
328
472
584
712
840
968
segmentation is possible, even if MAX_NUM_PRB is
– 2 segments
8
120
256
392
536
680
808
968
1096
– 3 segments
9
136
296
456
616
776
936
1096 1256
– 5 segments
10
144
328
504
680
872
1032
1224 1384
reduced.
10. UE will keep been allocated ulsMinRbPerUe and sending at least ulsMinTbs bits of data
PRB assignment – New condit ion intro duced
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LTE571 - Controlled UL packet segmentation
IF ulsMinRbPerUe >= MAX_NUM_PRB : Minimum number of PRBs per UE (LTE571)
If LTE571 is enabled, PRB allocation is limited by ulsMinRBPerUe, whenver MAX_NUM_PRB is too small
PRBUE = max( redBwMinRbUl, PRB_ulsMinTbs, ulsMinRbPerUe)
Without ELSE: LTE571
Number of PRBs based on min TBS and MCS order (LTE571)
Without LTE571 upper limit for PRB allocation is always coming from ATB (MAX_NUM_PRB)
Ordinary Scheduled UEs
max(redBwMinRbUl, PRB_ulsMinTbs) PRBUE
