HSDPA Principles Seminar
Corrado Carbone - RO/QoS South
2
Agenda
3. Channel Structure
2. Architecture
1. Overview
5. InterFrequency Mobility Principles
6. Capacity Management
4. Accessibility & Mobility Principles
7. KPIs
3
Outline
• Let‟s get used with the main concepts of the HSDPA.
• HSDPA introduces new technologies in the UMTS world and consequently a new way to manage PS traffic.
• The most important impacts of it are on:
– Modulation
– Retransmission schemes
– Scheduling
– Usage of Power and Code
• This presentation reports an overview of the main issues to take in mind.
4
HSDPA Basic Principles
5
1 - Shared Channel Transmission (1/2)
• Shared-channel transmission implies that a certain amount of radio resources of a cell (codes and power) is seen as a common resource that is dynamically shared between users.
– The idea is that a part of the total downlink code resource is dynamically shared between a set of packet-data users, primarily in the time domain.
– The codes are allocated to a user only when they are actually to be used for transmission, leading to efficient code and power utilization.
• For P4 only 5 codes (SF = 16) will be available for the HSDPA feature and they will be shared on a time base.
Channelization codes allocated
for HS-DSCH transmission
5 codes (example) SF=16
SF=8
SF=4
SF=2
SF=1
User #1 User #2 User #3 User #4
TTI
Shared
channelization
codes
6
1 - Shared Channel Transmission (2/2)
• The Shared-channel transmission allows:
– Higher peak bit rate: all the resource can be allocated to a single user in case of low load.
– Better application performance being closer to the model TCP has being designed for.
– More efficient utilization of available code resources compared to the use of a dedicated channel, i.e. reduced risk for code-limited downlink.
• The Shared-channel transmission impacts:
– Scheduling become more complex
7
2 - Short 2 ms TTI (1/2)
• The Transmission Time Interval becomes extremely short in HSDPA; 2 ms compared to the 10 ms used by R99 high bit rate radio bearer.
• The HS channels are organised in sub-frame of 3 slots each; this means that the slot time 2/3 ms/slot is the same as for R99 slots (10/15 ms/slot).
• The scheduling and the link adaptation algorithms work at this frequency!
10 ms
20 ms
40 ms
80 ms
Earlier releases
2 ms
Rel 5 (HS-DSCH)
2 ms
8
2 - Short 2 ms TTI (2/2)
• The shorter TTI allows:
– Reduced air-interface delay: this is required by the the TCP at high data rates to Improved end-user performance
• The shorter TTI is necessary to benefit from other HSDPA features:
– Fast Link Adaptation
– Fast hybrid ARQ with soft combining
– Fast Channel-dependent Scheduling
2 ms
9
3 - HSDPA – Power Allocation
• HS-DSCH allocated power is decided by the RNC, prioritizing the DCH channel
• HS-DSCH adjusts the data rate to match the instantaneous radio conditions and the available transmission power in the RBS
– No closed loop power control is specified for HS-DSCH, unlike the DCH channel
• The system adjusts the data rate by
– varying the effective code rate
– changing the modulation scheme
• This leads to a higher efficiency in the usage of power.
Dedicated channels (power controlled)
Common channels
Power usage with dedicated channels
channels
t
Unused power
Power
HS-DSCH with dynamic power allocation t
Dedicated channels (power controlled)
Common channels
HS-DSCH (rate controlled)
To
tal
ce
ll p
ow
er
Power
To
tal
ce
ll p
ow
er
3GPP Release 99 3GPP Release 5
10
Link Adaptation
Available Power
4 - Fast Link Adaptation (1/3)
• The target for the link adaptation is to select a TFRC (Transport Format and Resource Combination) resulting in transmitting an as large transport block as possible with a reasonable error probability.
Channel Condition Coding
Modulation
TFC
Bit
Rate UE category
Traffic (buffers state)
11
4 - Fast Link Adaptation (2/3)
• Adjust transmission parameters to match instantaneous channel conditions
• HSDPA: Adapt on 2 ms TTI basis the Rate (“constant” power)
– Adaptive coding
– Adaptive modulation (QPSK or 16QAM)
• Link adaptation is implemented by allowing the MAC-hs to set the TFRC (Transport Format and Resource Combination) independently for each 2 ms HS-DSCH TTI
High data rate
Low data rate
feedback
12
4 - Fast Link Adaptation (3/3)
• In order to estimate current channel conditions, an estimate of the Channel Quality is reported by the UE to RBS (CQI).
• Based on the channel conditions and the available power, the network will select the Transport Format to have the maximum throughput achievable
High data rate
Low data rate
feedback
13
• Scheduling = which UE to transmit to at a given time instant
• There is a main tradeoff to choose between:
fairness vs. cell throughput
5 - Fast Channel-dependent Scheduling (1/2)
Every user has the
same “rights to
access the resource”
The user with better
radio condition
transmit more
User1 User2 User3 User4
time 2 ms 2 ms
14
5 - Fast Channel-dependent Scheduling (1/2)
• 2 opposite strategies are:
– Round Robin: radio resources are allocated to communication links on a sequential basis.
– Proportional Fair: transmit at fading peaks. This may lead to large variations in data rate between users.
high data rate
low data rate
Time
#2 #1 #2 #2 #1 #1 #1
User 2
User 1
Scheduled
user
15
6 - Fast Hybrid ARQ with Soft Combining (1/2)
• HSDPA introduces a new retransmission level “under” the RLC scheme in the RNC.
• This new “level” allows rapid retransmissions of erroneous data:
– Hybrid ARQ protocol terminated in RBS short RTT (typical example: 12 ms)
– Soft combining in UE of multiple transmission attempts reduced error rates for retransmissions
P1,1
P1,1
P1,2
P1,2
P2,1
P2,1
P2,2
P2,2
P3,1
P1,1 P2,1 P3,1
+ +
Transmitter
Receiver
16
6 - Fast Hybrid ARQ with Soft Combining (2/2)
• A fundamental difference between conventional ARQ (used in RLC) and HARQ is that:
– in the latter case received data blocks that cannot be correctly decoded are not discarded but buffered
– They are soft combined with later received retransmissions of the same set of information bits.
– Finally, decoding is applied to the combined signal.
17
7 - UE capabilities
• The UE capabilities are divided into a number of parameters:
– Total RLC AM and MAC-hs buffer size
– Maximum number of HS-DSCH transport channel bits received within a HS-DSCH TTI
– Support of HS-PDSCH Yes/No
– Maximum number of HS-DSCH codes received
– Total number of soft channel bits in HS-DSCH
– Minimum inter-TTI interval in HS-DSCH
– Supporting 16QAM
• These physical layer UE capabilities can be translated in a limit on the requirements for 3 different UE resources:
– the de-spreading resource (codes decoded in parallel)
– the soft buffer memory used by the hybrid ARQ functionality
– the turbo decoding speed (the maximum number of transport channel bits received within an HS-DSCH TTI and the minimum inter-TTI interval).
18
Throughput level: UE type cat 12
• There are several levels for throughput calculation: let‟s clarify!
• The biggest MAC-HS transport block size is 3440 including HS header and padding bits:
X 10 = + + = 3440 bits
RLC SDU
= 320 RLC
head = 16
MAC- HS SDU
head = 3360
MAC- HS
head = 21
Padding
bits = 59
That means the DSCH max scheduled bit rate could be 1720 kb/s:
That is including headers, padding and every type of retransmission
This is the level used by the RBS counters and Couei!
This corresponds to a max RAB bit rate of 1600 kb/s =320*10/2
In reality considering at least the HS retransmissions at this level the maximum bit rate could not be higher
than 1600*0.9 =1440 bit/s
19
Agenda
3. Channel Structure
2. Architecture
1. Overview
5. InterFrequency Mobility Principles
6. Capacity Management
4. Accessibility & Mobility Principles
7. KPIs
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Protocol stacks (1/4)
UE RBS SRNC
PHY
AAL2
ATM
FP MAC-hs
L1
RLC
User Data
PHY PHY
AAL2
ATM
AAL5
ATM
GTP-U
UDP/IP FP
RLC
MAC
CN
PHY
AAL5
ATM
GTP-U
UDP/IP
User Data
Uu Iub Iu
The figure shows the R99 protocol stack.
Note in particular that MAC is a protocol between the RNC and the
UE
MAC
L1
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Protocol stacks (2/4)
UE RBS SRNC
PHY L1
AAL2
ATM
MAC-hs
HS-DSCH
FP
MAC-d
MAC-hs
L1
RLC
User Data
PHY PHY
AAL2
ATM
AAL5
ATM
GTP-U
UDP/IP HS-DSCH
FP
RLC
MAC-d
CN
PHY
AAL5
ATM
GTP-U
UDP/IP
User Data
Uu Iub Iu
The new radio interface layer 2 functionality required by the HS-
DSCH (hybrid ARQ signaling, scheduling, etc) was placed in a new
functional entity of the MAC layer, called MAC-hs.
The physical layer was updated with new functionalities for HS-
DSCH (soft combining of retransmitted transport blocks, new
physical channels, etc.).
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Protocol stacks (3/4)
UE RBS SRNC
PHY L1
AAL2
ATM
MAC-hs
HS-DSCH
FP
MAC-d
MAC-hs
L1
RLC
RRC
PHY PHY
AAL2
ATM
AAL5
ATM
GTP-U
UDP/IP HS-DSCH
FP
RLC
MAC-d
CN
PHY
AAL5
ATM
GTP-U
UDP/IP
RRC
Uu Iub Iu
A new user-plane frame-handling protocol (UP FP) between the
SRNC, DRNC and Node B needed to be developed for the radio
network layer (RNL). It was based on the release 99 DSCH UP FP
used over Iur.
The layer 3 control-plane protocols (RRC, RNSAP and NBAP)
needed to be updated with control procedures, handling HS-DSCH.
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Protocol stacks (4/4)
UE RBS SRNC
PHY L1
AAL2
ATM
MAC-hs
HS-DSCH
FP
MAC-d
MAC-hs
L1
RLC
TCP/IP
PHY PHY
AAL2
ATM
AAL5
ATM
GTP-U
UDP/IP HS-DSCH
FP
RLC
MAC-d
CN
PHY
AAL5
ATM
GTP-U
UDP/IP
TCP/IP
Uu Iub Iu
Note that RLC does not have significant impact
When the HS-DSCH transport channel is used with AM RLC, it is
expected that RLC re-transmissions will be required only in rare
circumstances where the inner hybrid ARQ fails.
E.g. in handover situations, the transmit and receive buffers in the
MAC-hs layer may need to be re-initialized. This may cause data
loss, which would be taken care of by RLC retransmission.
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General impacts of the new architecture
• There will be impacts on the buffer capabilities
– for data in the RBS a new buffer is needed to store data of different users
– The mobile has to store erroneous PDU for Soft Combining
– Requirements on buffer could be different due to the new amount of transmitted data
• Algorithms have to be adapted:
– Admission and Congestion Control for example need new way to estimate the load and accept new users.
– Closed loop power control does not apply to HS.
– New algorithms that manage the new functionalities have to be introduced (buffer, scheduling).
• Mobility algorithm in particular is conditioned since the fast link adaptation does not allow the Soft Handover anymore.
• The e2e performance of the PS users significantly improves due to a smaller RTT.
25
• RBS
– New TX board in RBS
• RNC
– No HW upgrades
– Only SW!!
– Setup of HS-DSCH/HS-SCCH
HSDPA Basics: Node Impacts
R99: • Scheduling,
• TF selection,
• Link layer
retransmission
(ARQ)
Core
Network
RNC
Node B HSDPA: • Scheduling,
• Link
Adaptation,
• Hybrid ARQ
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Node Functionality
Iub
Iur
Iu
Associated
Dedicated
Channels
RNC Function:
RAB establishment & release
Channel switching
Mobility
Resource handling
Capacity management
L2 (MAC-d)
UL HS control channel power control
Certain flow control
RNC
27
Node Functionality
RBS Function:
L2 (MAC-hs)
Scheduling
HARQ process handling
Transport format selection
Certain flow control
DL HS shared control power control
Iub
Iur
Iu
Associated
Dedicated
Channels
RNC
28
Agenda
3. Channel Structure
2. Architecture
1. Overview
5. InterFrequency Mobility Principles
6. Capacity Management
4. Accessibility & Mobility Principles
7. KPIs
29
HSDPA new channels
• HSDPA introduces specific channels, 1transport and 3 physical channels:
– The transport channel High Speed Downlink Shared Channel (HS-DSCH) is a resource existing only in downlink and carries user data in HSDPA.
– The High Speed Physical Downlink Shared Channel (HS-PDSCH) is a downlink physical channel, to which the HS-DSCH channels are mapped.
– The High-Speed Shared Control Channels (HS-SCCH) is used for downlink control signaling and carries indication about UE scheduling.
– One Associated Dedicated Channel (A-DCH) pair (UL & DL) per HSDPA user in connected state, used for control signaling and uplink data transmission. The uplink control information is carried by the Uplink High Speed Dedicated Physical Control Channel (HS-DPCCH).
A-DCH
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Channel Structure
Associated
Dedicated
Channels
Control Channel
HS-PDSCH High-Speed Physical Downlink Shared Channel (Physical)
HS-DPCCH – High-Speed (related uplink) Dedicated Physical Control Channel
(Physical)
A-DCH – Associated Dedicated Channel – A-DCH (Transport)
HS-SCCH – High-Speed Shared Control Channel(s) (Physical)
HS-DSCH – High-Speed Downlink Shared Channel (Transport)
31
An overview of HS-DSCH and its associated channels
CN RNC RBS UE
-
DPCCH
DP DCH
HS DPCCH
HS-SCCH
HS-PDSCH HS -DSCH
DCCH
DCCH
DTCH Interactive PS RAB
DTCH Interactive PS RAB
DTCH Interactive PS RAB
DCCH NAS
DCCH NAS
RRC
User 1
User 2
User n
For each user
Radio Access Bearers: - Intera ctive - Background
Logical Channels:
-Dedicated Control Channel, DCCH
-Dedicated Traffic Channel, DTCH
Transport Channels:
-Dedicated Channel, DCH
-High-Speed Downlink Shared Channel, HS-DSCH
Physical Channels:
-Dedicated Physical Channel, DPCH
-DPCCH, Dedicated Physical Control Channel
-DPDCH, Dedicated Physical Data Channel
-HS-DPCCH, HS-DSCH Dedicated Physical Control Channel
-HS-DSCH Shared Control Channel, HS-SCCH
-High Speed Physical Downlink Shared Channel, HS-PDSCH
DPCH DCH
DCH
Iu Iub Uu
32
HS-DSCH : High-Speed Dedicated Shared Channel
• HS-DSCH is the transport channel used for data transmission on the downlink and is shared by all users in the cell. In the HSDPA first phase product release:
– the sharing of code resource is done in the time domain on a 2 ms time basis (TTI).
– The shared code resource consists of 5 channelization codes with fixed spreading factor SFHS-DSCH = 16, in this time frame.
• The HS-DSCH cannot be in soft/softer handover and no fast power control is used.
• The HS-DSCH uses all the excess power from the available transmission power at the base station left from the common and dedicated channels
33
HS-SCCH: High-Speed Shared Control Channel
• HS-SCCH is a downlink physical channel used to carry HS-DSCH related control signaling (Physical Layer signaling).
• It is shared among the HSDPA users on time division basis (TTI), with the same scheduling as for HS-DSCH.
• All UEs listen to the same HS-SCCH channel and after decoding, decide whether the information to start listening the HS-PDSCH was intended to that UE.
• Informs the UE about:
– HS-DSCH code set
– Modulation scheme (QPSK/16QAM)
– HS-DSCH transport format (number of transport blocks per TTI and number of bits per transport block)
– Hybrid ARQ information
• Never in soft handover
• The HS-SCCH has a spreading factor SFHS-DSCH = 128
34
A-DCH: Associated Dedicated Channel
• One A-DCH pair is set up for every HSDPA user in connected state.
• It is used for control signaling (RRC and NAS) in UL and DL.
• It is a new Radio Bearer corresponding to a 3.4 kbps SRB in the DL (Sf 256).
• In the uplink A-DCH is also used as the channel for data transmission, where the rate can be either 384 kbps or 64 kbps.
– The uplink data rate 384 kbps is selected as first priority and 64 kbps is used as a fall back rate if the path loss is judged to be too large or 384 kbps radio bearer setup fails for any reason (e.g. lack of radio or hardware resources).
• The uplink A-DCH channel also contains the High-Speed Dedicated Physical Control Channel (HS-DPCCH), the new physical channel that carries the L1 related signaling in UL.
35
HS-DPCCH: High-Speed Dedicated Physical Control Channel
• It is used for transmitting the following information from UE to RBS:
– HARQ acknowledgement (1 bit coded in 10)
– Channel quality indicator (5 bits coded to 20 bits in 2 slots)
– channel quality measurements based on CPICH
– reporting rate is configurable through RRC/NBAP signaling
– information reflecting the instantaneous downlink radio channel conditions to assist the RBS in the transport format selection (fast link adaptation) and the scheduling
– The HS-DPCCH has a spreading factor SFHS-DSCH = 256
• The A-DCH both UL and DL can be in soft/softer handover whilst the HS-DPCCH can never be in soft handover (softer is possible).
• HS-DPCCH (UL) is transmitted within a dedicated channel. The main idea is that it is power controlled from the other part of the A-DCH.
36
HSDPA Channel Operation
HS-DPCCH: CQI
HS-SCCH: DL Transfer Information
HS-DSCH: Data Transfer
HS-DPCCH: ACK/NACK
Physical Channels:
-Dedicated Physical Channel, DPCH
-DPCCH, Dedicated Physical Control Channel
-DPDCH, Dedicated Physical Data Channel
-HS-DPCCH, HS-DSCH Dedicated Physical Control Channel
-HS-DSCH Shared Control Channel, HS-SCCH
-High Speed Physical Downlink Shared Channel, HS-PDSCH
37
UserPlane: Overview
• There are 8 steps to transmit on the HS-DSCH:
– In the RNC, the Interactive RAB is mapped to a radio bearer to be transmitted on the HS-DSCH.
– The radio bearer is then processed by the RLC and MAC-d layer 2 protocols in the RNC.
– The resulting MAC-d PDUs are transmitted over Iub to the RBS using the HS-DSCH frame protocol.
– The MAC–hs receive the Channel Quality Indicator “adjusted” by the Node B
– The MAC-hs scheduling function selects in each TTI the user to which the HS-DSCH is transmitted.
– Following the selection of a user, the user data to transmit on the HS-DSCH is put into one of several HARQ processes in the MAC-hs HARQ protocol.
– The amount of data to transmit is determined by the TFRC selection algorithm.
– Hence the data is transmitted to the UE over the air interface.
38
RAB/RB Combination – Overview
• Interactive and background Packet Service
• New RABs defined:
– Interactive PS 64/HS
– PS 384/HS (optional)
• DL bit rate up to 4.32 Mbps in P4 (user data rate)
• About HS-DSCH:
– Max. 5 codes
– DL: QPSK or
– DL: 16QAM (optional)
– UL 64 kbps interactive radio bearer
– Supported by symmetric 3.4 kbps signaling radio bearer (SRB)
39
Agenda
3. Channel Structure
2. Architecture
1. Overview
5. InterFrequency Mobility Principles
6. Capacity Management
4. Accessibility & Mobility Principles
7. KPIs
Accessibility:
Call setup phases
40
f2 HS
Radio network functions
RNC RNC Iur
Iub Iub
Iu Iu
Associated
Dedicated
Channels
Iub
f1 f1
f2 HS f2 HS
f1
f1 f1 f1
1
Camping in idle 1 Access the HSDPA system 2
2
3
Move within the system 3
4
Move out of the system 4 Control the power 5
5
Decide which mobile and
how much to transmit to it 6
6
RRM policy 7
7
41
CS Streaming
SP0 not available
Note 1: It is possible to go to Idle from all states (Signaling connection release)
Note 2: QoS profiling on the PS Int RAB is handled by Channel Switching
Note 3: Same transitions is valid for PS Streaming 16/64 and PS Streaming 16/128
Note 4: RAB establishment on FACH depending on the setting for parameter PacketEstMode
RAB Release
Channel Switching
RAB Establishment
UDI (CS64) PS Streaming+Int 8/8
SP0
SP64
UDI+Int. 8/8
Int. 64/128
Int. 64/384
Int. 64/64
Int. FACH
Speech
SRB
Other int. RAB state
SRB RAB est on FACH
New!
New!
New!
State Diagram – non HSDPA-P4
42
SRB-
DCH
Idl
e
RAB
Establishment
RAB Release
Signaling
Connection
handling
HS-DSCH
(uplink 64 or 384)
The diagram is clearly much
easier. What does it means?
Few transitions
Only 2 HS RABs exist
The choice between 64 or 384
is done at the beginning and
cannot be changed during the
connection.
State Diagram – only HSDPA
43
Idle mode & RRC Connection Establishment
• In idle mode there is no difference between a user with HSDPA capability or not.
• The UEs select the the cell with best Ec/N0 with the procedure ”cell reselection” as in R99.
• In second carrier sites, HSDPA is deployed in the second carrier only
– Most idle UEs will camp on f1
– Most HS users must be moved to f2 in order to get the ”HS service”
• There is no difference in the RRC Connection Establishment procedure between a user with HSDPA capability or not
– RRC Connection Request and Radio Connection Setup Complete contains information about the UE capability
f1 f1 f1
f2 HS f2 HS f2 HS
HS+ f1 HS+f1 Ec/No
f1
f2
44
UTRAN
RANAP: RAB Assignment Request
(establish PS Interactive/Background RAB)
Radio Bearer setup
RANAP: RAB Assignment Response
Serving HS - DSCH cell selection
SGSN UE
HSDPA capability analysis
SRB - DCH
Possible Inter frequency hard handover
RAB establishment
1
2
3
4
0
45
Capability analysis
• At the reception of RANAP RAB Assignment Request, if: – the present UE state is SRB-DCH and if the RAB mapping gives as result PS interactive
or PS background
– the “Access stratum release indicator” received from UE indicates Rel-5 or later release,
– the “Physical channel capability” received from UE indicates that the UE supports FDD HS-PDSCH (any HS-DSCH-physical-layer-category shall be supported),
– if the existing UE capability check for L2 are successful
The RNC performs the
Serving HS-DSCH cell selection
UTRAN
RANAP: RAB Assignment Request (establish PS Interactive/Background RAB)
Serving HS - DSCH cell selection
SGSN UE
HSDPA capability analysis
SRB - DCH
1
Otherwise the RAB is established in design base system.
46
Serving HS-DSCH cell selection
• When, at RAB establishment, the UE starts the procedure 3 results are possible:
– If the HS-DSCH is enabled in the best cell, the connection is set up in that cell.
• Otherwise the RNC check the coverage relation of the best cell.
– If the HS-DSCH is enabled in the target cell, an hard handover is tried to the new selected cell.
– If no cells are available and the connection is established on an
interactive DCH.
Current active set
New active set
DCH
2
47
Coverage relations
• The coverage relation is a unique uni-directional relation between two cells, a source and a target cell.
• The purpose of the coverage relation is to give the operator a possibility to distribute HSDPA downlink traffic among the cells of an RNC.
• The target cell covers almost the same area and can be assigned the same frequency or different ones. Typically the cells will be co-located.
A coverage relation is
defined for a source cell
with the parameters (3GPP
R5 25.423): hsPathLossThreshold
utranCellRef (the target cell)
coverageIndicator
2
48
Two Carriers scenario: IF HO
• In case the HSDPA is deployed on a second layer and the mobile access the network from the first layer the step will be the following:
f2 HS
f1
f2 HS f2 HS
f1 f1 f1
f1
Start the RAB establishment and the Cell Selection procedure..
When the attempt on the AS cells fails, check the coverage relation of
the best cell and its path loss
2nd carrier
1st carrier
The mobile ask for a SRB establishment on a cell of Carrier 1
f1
If everything is ok, perform a BLIND IF-HO
f2 HS
f1 f1
f2 HS f2 HS
f1 f1 f1
f1 If the IF HO succeed continue the RB set up on the new carrier..
Otherwise the RNC try to establish a R99 PS
RAB on the first carrier
f2 HS
f1 f1
f2 HS f2 HS
f1 f1 f1
f1
3
49
Interfrequency load distribution
• It adds the possibility to configure a "load-sharing margin" which can be used to reserve output power, for e.g. HSDPA traffic, in selected cells
• It makes the cell appear more loaded than it actually is
• It can be used to push traffic on a specific carrier
50
8. Iub and Iur Transport Bearer setup, AAL2 Connection setup
7. NBAP: Radio Link Reconfiguration Ready
4. RNSAP: Radio Link Reconfiguration Prepare
9. Set Activation time
2. Allocate resources
1. Admission request
10. RRC: Radio Bearer Setup – R5
12. RRC: Radio Bearer Setup Complete
11. Perform actions at Activation time
UE SRNC DRNC
9. NBAP: Radio Link Reconfiguration Commit
9. NBAP: Radio Link Reconfiguration Commit
9.RNSAP: Radio Link Reconfiguration Commit
5. Allocate resources 5. Allocate resources
6. NBAP: Radio Link Reconfiguration Ready 6. RNSAP: Radio Link Reconfiguration Ready
4. NBAP: Radio Link Reconfiguration Prepare
3. NBAP: Radio Link Reconfiguration Prepare
4. Allocate resources
4. Admission request
RBS RBS DRNC
13. Release resources
RB setup (1/2)
• If the result from the “Serving HS-DSCH cell selection” gives that a Serving HS-DSCH cell is selected
-> the “RB setup, SRB-DCH to PS interactive (64 or 384)/HS - HS-DSCH transition” is performed
• If the result gives that no Serving HS-DSCH cell is selected, but UE connection is still maintained
-> the RAB establishment is performed as in the design base.
4
51
RB setup (2/2)
• Different levels of Admission control runs in the RNC
– For the selected serving HS-DSCH cell, run Admission Control algorithm for the A-DCH configuration and for HS-DSCH configuration (number of serving links).
– For the other cells within SRNC, run Admission Control algorithm for the A-DCH configuration.
• The RANAP RAB Assignment Response is sent to the CN when the Radio Bearer Setup Complete has been received.
• The handling of UL/DL user data on RLC level is done as in the R99 for PS interactive RB.
4
52
UL: 64 or 384?
• Which UL A-DCH to set is decided during the AC phase.
• From an AC point of view, there are 2 guaranteed-hs service types:
– PS64/HS Interactive PS service with rate 64 kbps in uplink and HS-DSCH using up to 5 HS-PDSCH codes in downlink.
– PS384/HS Interactive PS service with rate 384 kbps in uplink and HS-DSCH using up to 5 HS-PDSCH codes in downlink.
• A part from the other AC check there are 2 special checks for the UL A-DCH:
– Histogram Admission Policy: requests demanding spreading factor 4 in uplink (PS384/HS radio connection type) are compared with sf4AdmUl.
– The path loss is checked in order to understand if a 384 UL bearer can be sustained.
• If the 384 RB is denied (or is accepted but the RBS don‟t find the synchronization in the establishment phase) the connection is established on the 64 RB.
4
53
Release of Iu-PS connection due to inactivity in HS-DSCH state (1/2)
• When a user finishes its transmission has to release the resources.
• The procedure is really simple:
– An "HS-DSCH inactivity" timer is started when there is no data to transmit.
– When the timer expires a Iu Release request is sent and the resources are released.
• The value of the timer is a system parameter hsdschInactivityTimer
54
Please note that..
• No Channel Switching, cell_DCH -> Idle:
– No cell_FACH for HS users.
– No “soft” switch between HSDPA and DCH
– No transition between the UL rate is possible
– The UE can regulate its rate in UL depending on the cell interference level. Hence a 384 RB in UL has to be considered as the maximum bit rate.
SRB
-
DC
H Idle
HS-DSCH
(uplink 64 or
384)
RAB Combinations:
Interactive 64/HS kbps PS RAB UL: Interactive 64 kbps PS RB + 3.4 kbps
SRBs on DPCH
DL: Interactive PS RB on HS-PDSCH + 3.4
kbps SRBs on DPCH
Interactive 384/HS kbps PS UL: Interactive 384 kbps PS RB + 3.4 kbps
SRBs on DPCH
DL: Interactive PS RB on HS-PDSCH + 3.4
kbps SRBs on DPCH
55
Incoming CS call
• A critical issue for the HSDPA in P4 is the management of the incoming call.
• Subsequent RAB assignments are rejected by RNC
– no multi RABs
f2 HS f HS f HS f
f
RNC
Iub
Iu
Speech
call Please note that..
UTRAN UE
1. RANAP: RAB Assignment Request (CS RAB)
MSC
2. RANAP: RAB Assignment Response
SGSN
PS Interactive 64/HS - HS-DSCH
If the current PS Interactive RB is allocated HS-DSCH resources, the RAB Assignment
response includes the unmapped RAB IDs in the “RABs failed to setup or modify” IE.
56
Agenda
3. Channel Structure
2. Architecture
1. Overview
5. InterFrequency Mobility Principles
6. Capacity Management
4. Accessibility & Mobility Principles
7. KPIs
Mobility:
Intra-HSDPA
57
RNC RNC Iur
Iub Iub
Iu Iu
Associated
Dedicated
Channels
Iub
HSDPA Mobility: introduction (1/3)
• After the cell selection, the network has to guarantee the mobility of the HSDPA users
• Since No Soft/Softer HO exist for HS-DSCH, there will be only one serving cell for the HS-DSCH.
• 2 algorithms are interested in the mobility of HSDPA users in connected mode:
– Serving HS-DSCH Cell Change
– A-DCH Soft/Softer HO
58
HSDPA Mobility: introduction (2/3)
• The HSDPA mobility will be splitted here in different issues:
– Measurement reporting handling
– Handover for A-DCH
– Serving HSDPA cell change
59
HSDPA Mobility: introduction (3/3)
• Note that when the UE is PS Interactive using HSDPA, the MEASUREMENT CONTROL includes only neighbor cells of type intra-frequency and no Compressed Mode is triggered, that means that Inter-Frequency and Inter-RAT Handover are not possible to be performed
• What happens when the mobile move to area without HSDPA coverage?
f2 HS
f1 f1
f2 HS f2 HS
f1
f1 f1 f1
2 layers
f2 HS HS HS f f
f
1 layer
60
Measurement reporting (1/2)
• While user moves in the network, it continues to perfom measurement on the CPICH of the detected cells.
• When a UE is setup on a dedicated channel:
– the SRNC sends a MEASUREMENT CONTROL (some information are broadcasted in the system information on the BCCH channel) orders the UE to start Intra frequency measurement.
– As soon as the triggering conditions are fullfilled, the UE sends a MEASUREMENT REPORT message to the SRNC indicating which event occurred and which among the measured cells fulfilled the event criteria.
61
Measurement reporting
• 4 types of intra-frequency measurements are defined in the 3GPP:
– Event 1a: Add cell - A primary CPICH enters the reporting range
– Event 1b: Delete cell - A primary CPICH leaves the reporting range
– Event 1c: Replace cell - A Non-active primary CPICH becomes better than an active primary CPICH
– Event 1d: Change of best cell - A primary CPICH becomes better than the previously best primary CPICH
– Event 1e: A primary CPICH becomes better than an absolute threshold
– Event 1f: A primary CPICH becomes worse than an absolute threshold
• Note that the RNC can configure more than 1 measurement report for the same event.
62
Mobility Example
0 5 10 15 -20
-15
-10
-5
0
time [s]
E c /N
0 [dB
]
cell 1
cell 2
cell 3
event 1d:
Change of best cell, to cell 3
Active set handling:
(Max active set = 3)
event 1a:
Add cell 2, to the AS
Add cell 3, to the AS
event 1b:
Delete cell2
2
1 3
63
Measurement reporting for HSDPA
• When PS Interactive using HSDPA is started, an extra MEASUREMENT CONTROL related only to the event 1d HS , is sent to the UE having another MEASUREMENT ID than the ones dealing with the conventional event 1d for Soft Handover evaluation.
• The reason for having a separate event 1d HS is
– to be able to get UE reports triggered by only Active Set cells
– to be able to use different hysteresis and time to trigger parameters to trigger HS-DSCH Cell Change.
– to use a different quality criteria (RSCP of the cells in the Active Set)
• Since the 1d Hs reported cell is already a member of the current Active Set, this event do not trigger any change in the AS.
64
R99 R99 R99
A-DCH handover
• In the previous slide it is stated that “there will be only one serving cell for the HS-DSCH”. This does not mean that the UE is connected to only one cell.
• For what concerns the A-DCH they continue to perfrom soft and softer hand-over as in normal R99 case.
• Note that HS-DPCCH can be only in softer HO.
• In the example supposing the best server does not change...
HS HS HS
HS HS HS HS
HS-DSCH
A-DCH
R99 HS
65
Serving HSDPA Cell Change (1/2)
• When the UE moves between cells, the HSDPA connection is maintained by means of intra frequency serving HS-DSCH Cell Change.
• HS-DSCH Cell Change evaluation performs the evaluation of a valid target cell within the current Active Set, only towards a “suitable HS-DSCH cell‟s”.
• A suitable HS-DSCH Cell is a cell that satisfies the following conditions:
– Cell in the current Active Set.
– Internal UTRAN cell.
– Cell having HS-DSCH enabled.
66
Serving HSDPA Cell Change (2/2)
• Serving HS-DSCH cell change is triggered by:
– Change of “Best cell” as indicated by receiving an event 1d, UE measurement report
– Removal of the Serving HS-DSCH cell from the active set due to receiving an event 1b, UE measurement report.
– Removal of the Serving HS-DSCH cell from the active set due to receiving an event 1c, UE measurement report.
– any other reason where the current serving HS-DSCH cell is to be removed from the active set.
• No support for HS-DSCH over Iur:
– RRC Directed Signaling Connection Re-establishment
67
Soft/softer HO for A-DCH and cell change for HSDPA channels
Measurement
quantity
time
P_CPICH 1
Reporting
event 1d-hs
P_CPICH 2 hsdhysteresis 1_
Reporting
event 1a
Rep. Range 1a
A-DCH in SHO with cell 1 and 2
HSDPA channels cell
change from cell 1 to cell 2
Rep. Range 1b
Reporting
event 1b
A-DCH on cell 2
only
Initially A-DCH and HSDPA
both only on cell 1
Note, there is of course a time-to-
trigger also for event 1d-hs
68
R99 f2 HS
HS HS
f2 HS f1 HS f1 HS
R99 R99
Serving HSDPA Cell Change
• If a suitable HS-DSCH cell can not be found within the current RNS a RRC connection release is triggered.
• After this a new cell selection can follow:
– Another connection establishment with a new Cell selection
– normal connection establishment on R99
– A connection establishment on GSM
f2 HS f2 HS f2 HS
f2 HS HS HS
Ex1
Ex 2
Ex 5
f2 HS f1 HS f1 HS
Cell Selection
Cell Selection
RNC RNC
f2 HS
R99 R99
f2 HS f2 HS
R99 R99 R99 R99
Ex3
R99 R99 R99
R99 R99 R99
f2 HS HS HS
f2 HS f2 HS f2 HS
GSM GSM GSM GSM GSM GSM
Ex 4
69
Radio Connection Supervision
• Separate parameter hsdschRcLostT determines how long time a HS user can be out-of-sync before the connection is released
• For HS users only the RL in the serving HS-DSCH cell is supervised.
– Sync status may change at serving HS-DSCH cell change
Whatever case
f2 HS f2 HS f2 HS
GSM GSM GSM
GSM GSM GSM
Radio Connection supervision is the
algorithm monitoring the
synchronization of a mobile, that is, if
the mobile is still connected or not.
70
Agenda
3. Channel Structure
2. Architecture
1. Overview
5. InterFrequency Mobility Principles
6. Capacity Management
4. Accessibility & Mobility Principles
7. KPIs
71
“Carrier” mobility
• A user conected with a UMTS network on a certain carrier can move out of the its layer coverage.
• There are 2 mechanisms to avoid the drop, at least for some services:
– Inter-RAT Handover
– Inter-Frequency Handover
f2 HS
f1 f1
f2 HS f2 HS
f1
f1 f1 f1
GSM GSM GSM
GSM GSM GSM
GSM GSM
GSM GSM GSM
GSM
• Most of the time anyway the passage between carriers happens in idle mode
72
IRAT/IF Handover in five steps (IRAT HO in the example)
UTRAN
UE moves to poor
carrier coverage area
and reports to UTRAN 1
UTRAN commands
CM measurements 2
UE finds suitable cells in another layer
and when coverage is even
worse it reports the candidates 3
UTRAN evaluates the
candidates and
commands the HO 4
UE gets access to the new LAYER 5
Core
Network
GSM/
Other Carrier
73
Layer Quality
time
Threshold 2
Threshold 3
Threshold 1
CM
Compressed Mode HO L2
L1
The problem is that there are several thresholds
IF&IRAT Handover: basic
• Main steps
– When the quality of the connection overcomes a certain thresholds (event 2d or 6a) UE reports a Measurement report and the network orders the UE to activate the CM and check the other layer.
– If the connection quality further degrades and the other layer has a quality high enough the HO is triggered (events 3a and 2b).
– If the connection quality turns out to be good, the UE signals it to the network and the mobile stops the CM (events 2f or 6b).
74
IRAT & IFHO procedures
• The evaluation process for HO execution depends on the quantity that started measurements (CPM) among:
– CPICH RSCP
– CPICH Ec/Io
– UE TX power
• At the same time, the cell in the target layer should have the quality good enough. That means:
– For GSM: the quality of the measured GSM cells is above a gsmThresh3a.
– For the second UMTS layer: the measured best cell on unused frequency is above both the thresholds nonUsedFreqThresh4_2bEcno and nonUsedFreqThresh4_2bRscp
• Both of the HO are hard HO:
– This means that there will be small interruptions in the data flow to and from the UE.
Evaluated In parallel
75
Initial
Cell
Target
Layer CPICH
Ec/No
HO
trigg
Start
CPM UE TX
power HO
trigg
Start
CPM
Other layer
good enough
CPICH
RSCP
Start
CPM
HO
trigg
CPM start and HO trigger
76
IRAT HO and Cell Change
• Until here, concerning 3G to 2G switch, only IRAT HO has been mentioned. Anyway when the UE is in connected mode with a PS RAB, the switching procedure to 2G is called “IRAT Cell Change”.
• Compared to IRAT HO:
– There is no difference in the evaluation procedure.
– In the Inter-RAT Cell Change case there are no resources reserved in the target cell before the Inter-RAT Cell Change is executed.
– There is significant outage period and a certain number of lost packets when moving toward 2G that have to be carefully evaluated
• (If the Inter-RAT Cell Change is evaluated and executed by the UE in Idle mode or connected mode on common channels it is denoted Cell Reselection or Inter-RAT Cell Reselection, see Idle Mode and Common Channel Behaviour for more details)
77
IF or IRAT?
• A decision has to be made to evaluate either Inter-Frequency handover or Inter-RAT Handover/Cell Change. This decision is based on parameters on RNC level, cell level, and UeRc state.
– Inter-Frequency handover is only attempted if C_IfHoAllowed is set to Allowed for the current UeRc state, and FddIfHoSupp (RNC) is set to On .
– Inter-RAT handover is only attempted if C_GsmHoAllowed is set to Allowed for the current UeRc state, and FddGsmHoSupp (RNC) is set to On.
– If both the conditions are verified the decision is based on a configurable parameter, hoType (cell), defined per cell (IFHO preferred, GSM preferred, None).
• Hence, for a certain cell only one of the 2 Handover types will be allowed.
Where?
f1
f2 HS
f1
GSM
GSM
? ?
78
• Dimensioning example
CIPICH dimensioning
CPICH power = 0.87 W
In the dimensioning process the power found
with CPICH is done in order to guarantee an
adeguate CPICH level (Ec/N0 > -16) within the
cell area (Range = 1.17 km).
Does that mean that the
boundary of a UMTS cell
corresponds to
CIPICH_EC/N0 = -16?
79
Which is the real area of a UMTS cell?
• When a GSM network or a second carrier is deployed the question is not easy to be answered.
• Only looking at the Ec/N0 suggested threshold for IF/IRAT HO we note that:
– usedFreqThresh2dEcno = -12
– utranRelThresh3aEcno = -1 (relative to 2d thr.) = -13
• Different terminals have different behaviours.
• The load changes the cell border.
80
Impact on coverage
WCDMA RBS
Area
without CM
CM start Ec/No
HO Ec/N0
CM start RSCP
HO RSCP
CM start Tx Pwr
HO RSCP
New area the cell
81
Notes for HSDPA
• HSDPA users, when in connected mode with a HSDSCH:
– will not be allowed to perform IF and IRAT HO.
– will not experience CM.
• Anyway:
– they can experiment it when in connected mode with a R99 RAB or in other dedicated connection.
– They can impact on other users behavior
Don’t forget idle mode!
Users change carrier or network even in idle mode and the
coprresponding parameters have to be carefully tuned as well.
82
GSM coverage
GSM only area
IRAT Cell Reselection
WCDMA unacceptable area
because of low RSCP
WCDMA unacceptable area
because of low Ec/No
WCDMA acceptable area
WCDMA Service
RSCP>qRxLevMin +P
Ec/No>qQualMin
GSM->WCDMA
entering area
Ec/No>FDDQMIN
RSCP>GSM_RLA +FDDQOFF
WCDMA->GSM normal
reselection area
RSCP+qHyst1 > GSM_RSSI-qOffset1
Ec/No>qQualMin+sRATsearch
Overall description of thresholds
WCDMA RBS
Unstable areas
83
Agenda
3. Channel Structure
2. Architecture
1. Overview
5. InterFrequency Mobility Principles
6. Capacity Management
4. Accessibility & Mobility Principles
7. KPIs
Capacity Management
Algorithm
84
Capacity Management (Overview)
• Capacity Management solution controls the load in the WCDMA cells.
• It includes 3 main algorithms:
Admission Control controls the utilization of
dedicated monitored resources by accepting or
refusing requests for utilization of these resources
Congestion Control detects overload situations on
some dedicated monitored resources and initiates
congestion resolve actions to decrease the load
Dedicated Monitored Resource Handling gathers
and provides information about the current usage of
critical resources
85
Dedicated Resources
• The Dedicated Monitored Resource Handling function collects and provides information about the current usage of resources that are critical to the load of the cell. There are three reasons for blocking:
• RF POWER:
the total transmitted carrier power is constantly monitored by the algorithm. When the value exceeds some configurable thresholds the admission/congestion take decisions for guaranteed and non-guaranteed service class connections
• CODE
– Code Usage: the total number of codes is monitored.
– Code Hystogram: the number of codes used for each SF are monitored. The max number of code for each SF is configurable. A control is also done on the maximum number of compressed mode connections
• ASE (Air-Speech Equivalent): This monitor is based on the estimation of the air-interface usage per radio link type (RB type) in a cell. Thresholds can be defined separately for the uplink and downlink, for guaranteed or non-guaranteed connections
86
Admission Control Algorithm
Downlink Transmitted Carrier Power
Monitor (for Admission purpose)
35% 75%
85%
default values
• Requests arrive to the AC at several moments:
– Radio Link Setup
– Radio Link Addition
– Radio Link Reconfiguration
– Compressed Mode Command
• Different thresholds exist for different types of request:
– (g,ho) guaranteed, handover
– (g,nho) guaranteed, non-handover
– (ng,ho) non-guaranteed, handover
– (ng,nho) non-guaranteed, non-handover
• The AC accepts requests until a certain threshold on a monitored resource (power in this case) is reached.
87
Congestion Control Algorithm
Downlink Transmitted Carrier Power
Monitor (for Congestion control)
Default values:
pwrOffset = +5% 90%
pwrHyst = 600 ms
• The congestion control has an unique threshold for all the service types (pwrAdm+
pwrAdmOffset +pwrOffset) to regard the cell as “congested”.
• The action to decrease the load in the cell considers instead the different priorities of the services.
88
Traffic Algorithms
• The PS traffic (non-guaranteed) is managed by the RRM algorithms with a lower priority at several levels:
– Lower threshold on AC
– First user to be considered for Congestion actions
• Besides RRM algorithms, even the Channel Switching algorithm acts to control the PS traffic.
89
HSDPA Monitored Resource Handling
• The way of measuring the resources has to be adapted to the HSDPA:
– The monitored power in the RNC keeps track only of the usage of total non-HS downlink transmitted carrier power.
– The reports of the power measurements are adapted to the capability of a cell:
– HSDPA capable „Transmitted carrier power of all codes not used for HS-PDSCH or HS-SCCH transmission‟
– HSDPA not capable „Transmitted carrier power‟
– 2 new dedicated monitored resource is introduced:
– the number of HS-serving links in a cell.
– The usage of SF 4 in uplink (the usage of the optional PS384/HS radio connection type)
– The measurement of code tree utilization considers the codes allocated for HS-PDSCH and HS-SCCH channels.
90
HSDPA Admission Control Algorithm
• The AC receives requests from a HS users in 2 moments:
– At RAB establishment; in particular after the serving HS-DSCH cell selection.
– For mobility, e.g. A Radio link Addition for A-DCH handover
– No AC is performed within a Cell Change procedure
– Note that there are neither Compressed Mode requests nor Radio Link Reconfiguration
f2 HS
RNC Iur
Iub
Iu
Associated
Dedicated
Channels
f HS f2 HS
R99 R99 R99
1
AC
91
HSDPA Admission Control Algorithm
• The AC performs several types of check:
– A-DCH:
– Total available codes (for A-DCH only).
– ASE (for A-DCH only).
– Power (for A-DCH)
– Code with SF=4 in UL (for A-DCH PS 384 in UL)
– (Hardware, new in P4)
– HS-DSCH:
– Number of HS-serving links (for RAB set up only)
92
HSDPA - Code Control
• There is no check on HSDSCH and HSSCCH codes done by the AC.
• The operator configure and “reserve” the number of HS-PDSCH codes allocated in a cell for HSDPA (numHsPdschCodes)
– Increase lock of the cell and release of traffic
– Decrease no effect on ongoing traffic
• The number of HS-SCCH (SF=128) codes is one
93
HSDPA – Number of HS users
• The operator can limit the number of users that can be allocated to the HS-DSCH cell (hsdpaUsersAdm)
• This limit enables the users allocated to the HS-DSCH (shared channel) to experience a sufficient end-to-end quality
• The new policy is only applied to requests for new HSDPA connections
# users on HS-PDSCH / HS-SCCH
Only serving cell
change of HSDPA
admitted
Request for
HSDPA resources
always admitted
hsdpaUsersAdm
94
HSDPA –UL Histogram AC
• The operator can set a limit for the ”guaranteed-hs” admission requests demanding spreading factor 4 in uplink that can be accepted (in cells where the PS384/HS is activated)
• The threshold is set according to the parameter sf4AdmUl
• This policy allows the operator to disable the PS384/HS feature on a cell basis
• sf4AdmUl can be reduced if the uplink is experienced as problematic, for example due to high Received Total Wideband Power or transport network problems
95
• New service class, ”guaranteed-hs”, assigned to the A-DCHs
• Highest priority for ”guaranteed-hs” service class in admission decisions to enable HSDPA users to use the excess power in high loaded (non-congested) cells
• Soft congestion is not affected by the introduction of HSDPA
Power
Ad
mis
sio
n G
ran
ted
R
ejec
t
Ad
mis
sio
n G
ran
ted
R
ejec
t
Ad
mis
sio
n G
ran
ted
R
ejec
t
Rej
ect
Ad
mis
sio
n
Gra
nte
d
no
n-g
uar
ante
ed /
no
n-h
and
over
no
n-g
uar
ante
ed /
han
do
ver
gu
aran
teed
/ n
on
-han
dover
gu
aran
teed
/ h
and
ov
er
Ad
mis
sio
n G
ran
ted
R
ejec
t g
ua
ran
teed
-hs
/ n
on
-han
dover
Ad
mis
sio
n G
ran
ted
R
ejec
t g
ua
ran
teed
-hs
/ h
and
ov
er
pwrAdm + pwrAdmOffset
pwrAdm
pwrAdm – beMarginPwrAdm
pwrAdm + pwrAdmOffset + pwrOffset
HSDPA DL Power Admission
96
HSDPA – “Link” Power Admission
HSDPA While the admission control on a
”session” level is performed by the
RNC, it is important to take in mind
that the RBS ”control” the HS access to
the shared resources.
Common channels
Dedicated channels
To
tal a
va
ila
ble
ce
ll p
ow
er
97
HSDPA - Congestion Control
tmInitialG
tmInitialGhs
tmCongActionNg
Release non-guaranteed traffic
tmCongActionGhs
Release guaranteed HS traffic
tmCongAction
Release guaranteed traffic
Time
Power
Congestion threshold
”guaranteed-hs” service class gets intermediate
priority (between ”non-guaranteed” and
”guaranteed”)
tmInitialGhs minimum time between start of DL
congestions and initiation of congestion resolve
action on HSDPA users
All non-guaranteed traffic
released.
tmCongActionGhs is restarted as
tmInitialGhs has not expired.
This policy enforces the higher retention priority of
CS services compared to interactive services
tmCongActionGhs time interval between congestion
release actions on HSDPA
releaseAseDIGhs amount of ASE to be released at
congestion resolve action
98
Agenda
3. Channel Structure
2. Architecture
1. Overview
5. InterFrequency Mobility Principles
6. Capacity Management
4. Accessibility & Mobility Principles
7. KPIs
Load Sharing
Techniques
99
Load Sharing (1/2)
• Load sharing features pool together resources from different parts of the entire network.
• 2 load-sharing features are available in the WCDMA RAN:
– Inter-Frequency Load Sharing
– Directed Retry to GSM
Both load-sharing features redirect calls during the connection setup phase: RRC connection setup for IF load Sharing
RAB setup for Directed retry
Both IF HO and Directed retry will be present at the same time but IF will act first!
100
• For load sharing purposes, cell load is defined as the ratio between the downlink transmitted carrier power and the admission limit, as given by the cell parameter pwrAdm.
• The load sharing algorithm acts only when the load of a cell overcomes a certain threshold:
– For IF, the threshold is set to 50%
– For directed retry both the threshold and the percentage of users to be redirected can be tuned
Time
Cell
Lo
ad
DR
thr
Time
Cell
Lo
ad
IF
50%
Cell Load = Tx_power/PwrAdm
Load Sharing (2/2)
For HSDPA cells, only the non-HSDPA part is counted
101
Directed Retry algorithm
• Speech call (without packet connection) is the only service that is targeted since it is also the only one that is safe to divert to GSM
• Directed Retry is performed during the RAB establishment procedure;
– the first request will be rejected with cause "Directed retry“
– a request is made to the core network to relocate the UE to a specific GSM cell, using the Inter-RAT handover procedure.
• This handover is a blind HO since the target cell is chosen not based on UE measurements. Therefore, the target cell must be co-located with the WCDMA cell.
There are 2 control parameters:
loadSharingGsmThreshold specifies
the minimum cell load at which off-loading to GSM
begins.
loadSharingGsmFraction specifies
the percentage of Directed Retry candidates to be diverted
to GSM
Time
Cell
Lo
ad
DR
loadSharingGsmThreshold
102
Inter-Frequency Load Sharing (1/2)
UMTS L2
UMTS L1
GSM
If the target cell is less loaded, the UE will not be instructed directly to go to the target cell but it will
be told to scan for a suitable cell in the frequency of the target cell, by sending an RRC Connection
Reject message.
3
3
The mobile starts a RRC connection establishment procedure ( NO distinction in RRC cause is made)
1
1
2
If the cell load is higher than 50%, the load of the co-located load-sharing neighbor is compared with
the accessed cell and the least loaded cell is chosen as target.
Lo
ad
Cell 2
Lo
ad
Cell 1
> = <
?
2
50%
103
Free Resource = R[2]
Power/ pwrAdm
33%
100%
DL power in use 100%
Free Resource
Power/ pwrAdm
33%
Second Carrier
First Carrier
L[1] < 50 %
-> Don’t do anything
Free Resource = R[2]
Power/ pwrAdm
33%
100%
DL power in use 100%
Free Resource
Power/ pwrAdm
60%
Second Carrier
First Carrier
L[1] > 50 %
-> Compare the load with the
load sharing candidate
DL power in use 100%
Second Carrier
Free Resource
Power/ pwrAdm
33%
Free Resource
L[2] = 33% -- L[1] = 60%
L[1] > L[2] Select R[2],
Power/ pwrAdm
100%
First Carrier
60%
Free Resource = R[2]
Power/ pwrAdm
33%
L[2] = 33% -- L[1] = 60%
L[1] - 20% > L[2]
Select Second Carrier
100%
loadSharingThreshold (20%)
DL power in use 100%
Free Resource
Power/ pwrAdm
60%
To minimize excessive load sharing a hysteresis is used in the comparison,
loadSharingThreshold.
IF Load Sharing
Here an example of comparison between 2 different frequency is reported.
Layer 2
Layer 1
Lo
ad
Cell 2 Lo
ad
Cell 1
> = <
?
104
HSDPA – IF Load Sharing
Second Carrier Layer 2
Layer 1
Lo
ad
Cell 2 Lo
ad
Cell 1
> = <
? 50%
loadSharingMargin is a cell-specific parameter that specifies the amount of resource excluded from
load-sharing use (as a percentage of pwrAdm).
When loadSharingMargin is greater than 0, the cell appears to be more loaded than it really is, resulting
in more traffic being directed away from it
This parameter gives the operator the possibility to reserve a higher priority to the HSDPA users on
the second carriers (in case this is deployed and HSDPA is introduced there)
Free Resource = R[2]
Power/ pwrAdm
33%
100%
loadSharingThreshold
(20%)
L[2] = 33% + 10% -- L[1] = 60%
L[1] - 20% < L[2] 40% < 43%
Stay on the First Carrier
DL power in use 100%
Free Resource
Power/ pwrAdm
60%
loadSharingMargin (10%)
105
• Apart from the load sharing algorithm, other aspects have to be managed and tuned with the introduction of the second layer:
– Mobility:
– IF HO procedure is more critical compared to a normal SHO and has to be verified and tuned.
– The compressed mode activity increases in the border cells.
– Accessibility:
– The first IF Load Sharing will increase the call set up time.
– Terminal equipment limitations:
– At them moment, there are several terminal types not fully supporting the features to manage a second layer. In particular several models are not IF HO capable.
Inter-Frequency Load Sharing
106
Agenda
3. Channel Structure
2. Architecture
1. Overview
5. InterFrequency Mobility Principles
6. Capacity Management
4. Accessibility & Mobility Principles
7. KPIs
Cell Breathing
107
Coverage vs. traffic load
WCDMA RBS
DL
high
Load
UL
high
Loa
d
UL low
load DL low
load
A well known effect of WCDMA CPICH coverage is that it
changes depending on the load.
The DL coverage (considering the
Ec/N0 of the CPICH) in particular
decreases with the DL total power
(hence with the load).
CPICH_Ec/N0 in a point:
Ec/N0Cpich = RSCP/RSSI
= Pcpich/( (PtotIntra + Ptotinter + Noise)
(*P = received power)
108
Low load CM Area
CM start
IRAT
UL
high
Load
DL Problem CPICH Ec/N0 triggering
DL
high
Load
High load CM Area
CM start
IRAT
WCDMA RBS
Expected cell area
109
Agenda
3. Channel Structure
2. Architecture
1. Overview
5. InterFrequency Mobility Principles
6. KPIs
4. Accessibility & Mobility Principles
6. Capacity Management
Accessibility KPI
110
Accessibility (CSSR) KPI
The IF Load Sharing feature impacts on the RRC Establishment Success Rate
since several RRC Connection Attempts are rejected to be redirected towards the
other frequency. So it is expected that, in case of IFLS activated, the number of
RRC Connection Success will be reduced because of the Load Sharing Reject
events. To take into account this fact the LoadSharingRejects must be subtracted
from the total number of RRC_Attempts:
RRC Establishment Success Rate (IFLS) =
RRC_Success / ( RRC_Attempts – LoadSharingRejects)
CSSR is currently calculated by two factors:
RRC Establishment Success Rate = RRC_Success / RRC_Attempts *
RAB Establishment Success Rate = RAB_Success / RAB_Attempts
However the counter for Load Sharing Rejects (pmNoLoadSharingRrcConn)
is unique and it does not distinguish between CS, PS or any other kind of RRC
Connection cause.
This make not easy to adjust the RRC Success Rate for CS and for PS in
case of IFLS.
111
Proposed new formulae Here we tried to evaluate the performance of some formulae to derive the
RRC_Estab_Succ_Rate for PS and CS in case of IFLS.
(The results are taken from RNC???)
The tested formulae are:
ConnectReqpmTotNoRrc
CsConnectReqpmTotNoRrcnnaringRrcCopmNoLoadSh - CsConnectReqpmTotNoRrc
CsSuccConnectReqpmTotNoRrc __
CSSuccRRC
ConnectReqpmTotNoRrc
PsConnectReqpmTotNoRrcnnaringRrcCopmNoLoadSh - PsConnectReqpmTotNoRrc
PsSuccConnectReqpmTotNoRrc __
PSSuccRRC
The basic idea is to calculate the load sharing reject for PS and CS by a
wheight factor given by the fraction of the RRC_CS (or PS) respect to the total
number of RRCs. In case of RRC Succ general the formula is muche more
simple instead....
nnaringRrcCopmNoLoadSh - ConnectReqpmTotNoRrc
SuccConnectReqpmTotNoRrc __ generalSuccRRC
112
RRC Connection Establishment Success Rate CS and PS in case of Load Sharing
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
Days
0%
20%
40%
60%
80%
100%
120%
LoadSharingReject
RRC_SUC_CS_LS
RRC_SUC_PS_LS
Load Sharing Impact on Accessibility (CSSR) KPI - Results
The RRC Succ estimation CS and PS are
disturbed by the Load Sharing rejects.
We registered strong fluctuations of
values expecially in case of high IFLS
activity....
113
RRC Connection Establishment Success Rate General in case of Load Sharing
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
Days
0.0%
20.0%
40.0%
60.0%
80.0%
100.0%
120.0%
LoadSharingEvents
RRC_SUC_LS
Load Sharing Impact on Accessibility (CSSR) KPI - Results
In case of RRC Succ Rate calculated for all
kinds of RRC, the estimation is much more
stable instead and not affected by IFLS!
114
RRC Connection Estab. Succ. Rate comparison (General, CS, PS) including Load Sharing
80.0%
85.0%
90.0%
95.0%
100.0%
105.0%
110.0%
Days
RRC_SUC_LS
RRC_SUC_CS_LS
RRC_SUC_PS_LS
Load Sharing Impact on Accessibility (CSSR) KPI - Results
Here it is quite evident the noise introduced by
the load sharing in CS and PS RRC Succ
estimations.
>100% values
Strong KPI
deterioration
Please consider that the values are calculated on daily base. So they
should be quite stable
115
Conclusions (1/2) When Load sharing is introduce the accessibility formulae should be updated to
take into consideration the RRC Connection Attempts rejected to be redirected
towards the other frequency ().
While no problem should exist for the tot accessibility formula:
2 new formulae are proposed for the CS and PS specific KPIs:
However the estimation given by this KPI is not extremely stable/reliable and
accurate (the average error seems to be acceptable compared to the error that
affects the other formulae but the fluctuation are high).
ConnectReqpmTotNoRrc
CsConnectReqpmTotNoRrcnnaringRrcCopmNoLoadSh - CsConnectReqpmTotNoRrc
CsSuccConnectReqpmTotNoRrc __
CSSuccRRC
ConnectReqpmTotNoRrc
PsConnectReqpmTotNoRrcnnaringRrcCopmNoLoadSh - PsConnectReqpmTotNoRrc
PsSuccConnectReqpmTotNoRrc __
PSSuccRRC
nnaringRrcCopmNoLoadSh - ConnectReqpmTotNoRrc
SuccConnectReqpmTotNoRrc __ generalSuccRRC
116
Conclusions An alternative suggestion could be to use the following formula for CSSR
CSSR_CS = RRC_Succ_Global x RAB_CS_Succ
CSSR_PS = RRC_Succ_Global x RAB_PS_Succ
The estimation given by this KPI is much more stable/reliable and the average
error seems to be acceptable compared to the error that affects the other
formulae.
The main drawback of this solution is that the Global RRC Succ is often a little bit
worse compared with the real CS and PS values.
(This is probably related to different radio environment: i.e. the major part
of RRC Connections are established for registration purpose, when the
UE is entering back to 3G coverage; those radio procedures often occur
at cell coverage borders and so are affected by a worse performance.)
117
Agenda
3. Channel Structure
2. Architecture
1. Overview
5. InterFrequency Mobility Principles
6. KPIs
4. Accessibility & Mobility Principles
6. Capacity Management
RBS KPI
118
RBS Counters KPIs
• This appendix reports the main KPIs that could be used for HS testing divided by:
– Throughput
– Scheduling Ratio and Transmission efficiency
– CQI/ACK/NACK
– Power
– RBS RSSI
• Note that performing tests with a single HS user in a unloaded network is useful to:
– Have specific user information for a user
– Verify counters/KPI meanings and compare them with UE based KPI
119
Throughput Counters
• Counters: – pmSumAckedBits: the number of Media Access Control high-speed (MAC-hs) bits received and
acknowledged by the UE.
– pmSumTransmittedBits: the number of transmitted bits at MAC-hs, level including retransmissions
– pmSumNonEmptyUserBuffers: The number of user buffers containing high-speed data.
– pmNoActiveSubFrames: the number of subframes containing high-speed data transmitted by the RBS.
– pmNoInactiveRequiredSubFrames: the number of empty subframes transmitted even though data is scheduled for priority queue.
• Still not used:
– pmAverageUserRate (PDF): The distribution of the average user rate among all users allocated to high-speed-DSCH in the cell.
120
Throughput KPIs
• DSCH UE Thr. NET = Av. Throughput (PS-HS) without retransmission: Sum(pmSumAckedBits)/(Sum(pmSumNonEmptyUserBuffers)*0.002s)
• DSCH UE Thr. GROSS = Av. Throughput (PS-HS) with retransmission: Sum(pmSumTransmittedBits)/(Sum(pmSumNonEmptyUserBuffers)*0.002)
• DSCH Cell Thr. NET = The MAC-hs throughput on cell level
pmSumAckedBits / (0.002s * pmNoActiveSubFrame)
• DSCH Cell Thr. GROSS = The MAC-hs data rate on cell level
pmSumTransmittedBits / (0.002 s* pmNoActiveSubFrame)
• Cell Thr. NET = The MAC-hs throughput on cell level
pmSumAckedBits / (ROP period)
• Cell Thr. GROSS = The MAC-hs data rate on cell level
pmSumTransmittedBits / (ROP period)
121
Throughput KPIs Values – Live Network
RBS NameRBS
Sector
RBS
Sector
Carrier
Average
Number
Of UE In
a Queue
DSCH UE
Throughput
NET
DSCH UE
Throughput
GROSS
DSCH Cell
Throughput
NET
DSCH Cell
Throughput
GROSS
RBS32601-01 3 1 1 92.32 148.32 194.89 313.11
RBS05314-01 2 2 1 164.11 221.32 265.44 357.98
RBS37058-01 1 2 1 183.97 202.45 292.65 322.04
RBS00003-01 3 2 1 218.77 259.69 218.77 259.69
RBS34645-01 2 1 1 242.96 350.73 242.96 350.73
RBS01281-01 3 1 1 248.4 405.3 248.4 405.3
RBS37058-01 2 2 1 324.44 405.58 324.79 406.02
RBS01780-01 1 1 1 352.6 566.15 491.79 789.63
RBS00357-01 2 1 1 389 518.5 389 518.5
RBS00429-01 1 2 1 399.94 542.16 399.94 542.16
RBS37242-01 3 1 1 424.5 500.75 424.5 500.75
RBS34375-01 2 1 1.01 449.73 749.43 461.94 769.76
RBS01263-01 1 1 1 456.78 565.98 456.78 565.98
RBS23074-01 3 2 1 509.66 552.27 509.66 552.27
RBS23066-01 2 1 1 518.67 518.67 518.67 518.67
RBS04995-01 1 2 1 556.41 648.95 557.03 649.67
RBS00370-01 1 1 1 632.88 838.31 632.88 838.31
RBS01546-01 2 1 1 652.58 878.57 751.29 1,011.47
RBS01281-01 1 1 1 662.62 1,142.64 662.62 1,142.64
RBS34375-01 3 1 1 710.73 1,071.00 710.73 1,071.00
RBS23025-01 3 1 1.01 734.94 901.09 828.62 1,015.96
RBS37058-01 3 2 1 764.56 995.06 817.15 1,063.51
RBS00353-01 1 1 1 770.18 1,170.15 775.24 1,177.84
RBS34645-01 1 1 1 828.63 1,319.63 933.18 1,486.14
RBS23025-01 2 1 1 881.87 1,205.44 913.16 1,248.20
RBS05314-01 1 2 1 1,183.36 1,390.58 1,193.88 1,402.94
RBS00429-01 2 2 1 1,200.85 1,605.63 1,200.85 1,605.63
RBS01164-01 3 2 1 1,285.29 1,503.11 1,285.65 1,503.53
RBS01164-01 2 2 1 1,318.85 1,537.49 1,354.04 1,578.52
122
Transmission efficiency KPIs
• MAC Tx efficiency (or Efficiency factor ) =
Sum(pmNoActiveSubFrame )/ (Sum(pmNoActiveSubFrame)+Sum(pmNoInactiveRequiredSubFrame))
• Scheduling Ratio = This KPI simply highlights the percentage of time the HS-DSCH is used
Sum(pmNoActiveSubFrame)*0.002/ (ROP period)
• Transmission ratio = This highlight the percentage of time there is something to transmit. This is a good index on how efficiently the application level can exploit DSCH capabilities
(Sum(pmNoActiveSubFrame)+Sum(pmNoInactiveRequiredSubFrame))*0.002 /
(ROP period)
• Av.# UEs in queue
Sum(pmSumNonEmptyUserBuffers) / ( Sum(pmNoActiveSubFrame)+ Sum(pmNoInactiveRequiredSubFrames) )
123
( + )
Transmission Efficiency (1/2)
• The first index to look at when talking about transmission efficiency is the ratio between the used TTI (the one where something is transmitted) and the total #TTI in the test period
Mac Tx Efficiency = 99.05%
Scheduling Ratio = 81.3%
Nothing transmitted
PDU is transmitted
Buffer not empty but PDU not transmitted
Transmission Ratio = 82.8%
( + )
( + )
( + + )
124
Transmission Efficient KPIs Values – Live Network
RBS Name Sector Carrier
%
Scheduling
Ratio
%
Tranmission
Ratio
RBS32601-01 3 1 0.00% 0.00%
RBS05314-01 2 2 1.54% 2.49%
RBS37058-01 1 2 0.01% 0.02%
RBS00003-01 3 2 0.00% 0.00%
RBS34645-01 2 1 0.00% 0.00%
RBS01281-01 3 1 0.00% 0.00%
RBS37058-01 2 2 0.11% 0.11%
RBS01780-01 1 1 0.00% 0.00%
RBS00357-01 2 1 0.00% 0.00%
RBS00429-01 1 2 0.03% 0.03%
RBS37242-01 3 1 0.00% 0.00%
RBS34375-01 2 1 0.00% 0.00%
RBS01263-01 1 1 0.00% 0.00%
RBS23074-01 3 2 0.00% 0.00%
RBS23066-01 2 1 0.00% 0.00%
RBS04995-01 1 2 0.12% 0.12%
RBS00370-01 1 1 0.02% 0.02%
RBS01546-01 2 1 0.06% 0.07%
RBS01281-01 1 1 0.00% 0.00%
RBS34375-01 3 1 0.15% 0.15%
RBS23025-01 3 1 0.11% 0.12%
RBS37058-01 3 2 0.01% 0.01%
RBS00353-01 1 1 0.03% 0.03%
RBS34645-01 1 1 0.34% 0.38%
RBS23025-01 2 1 0.09% 0.09%
RBS05314-01 1 2 0.06% 0.06%
RBS00429-01 2 2 0.07% 0.07%
RBS01164-01 3 2 0.03% 0.03%
RBS01164-01 2 2 0.14% 0.15%
125
CQI/ACK/NACK counters
• pmReportedCqi: the Channel Quality Indicators (CQI) reported by the UE in the cell and received by the RBS.
• pmUsedCqi: the CQI, used by the RBS for scheduling the priority queue for the HS-DSCH.
• Within the reportedCQI tables, there is a column called “InvalidCQI”. This counter will be used as well
• pmAckReceived: The number of Acknowledgements (ACK) that the RBS receives from the User Equipment (UE) over the High-Speed Downlink Shared Channel (HS-DSCH).
• pmNackReceived: The number of Negative-Acknowledgements (NACK) that the RBS receives from the User Equipment (UE) over the High-Speed Downlink Shared Channel (HS-DSCH).
126
CQI/ACK/NACK KPIs
• HS-BLER: pmNackReceived /(pmNackReceived + pmAckReceived)
• RtxOverhead = Percentage of the Retransmitted bits over the total
100*(pmSumTransmittedBits - pmSumAckedBits) /(pmSumTransmittedBits)
• CQI specific
– Av. Reported
– Av. USed CQI
– Delta CQI = Difference between the 2 averaged values above. This is an index of how much “CQI adjustment” acts.
– CQIequalTo0 = Count(CQIreported=0)/Count(CQIreported). This is the main reason of MAC inefficiency
– InvalidCQI = invalideCQI/Count(CQIreported). Not clear what invlid means
• Proposal: (ACK+NACK)/ActiveTTI: still not clear WHAT WE CAN SEE FROM IT
(pmNackReceived+pmAckReceived)/ActiveFrame
127
HS scheduling
The CQI=0 percentage drop to 0.01%, almost nothing.
The BLER and the Retransmission rate are almost identical, that means the CQI adjustment
has been able to reach the target
Baseline Test 2
Reported BLER [%] 12,6 12,5
RtxOverhead [%] 14,8 15,0
Av Reported CQI 10,1 17,0
Av Used CQI 9,8 16,5
Delta CQI 0,32 0,48
(ACK+NACK)/Active [%] 98,68 97,29
CQI = 0 [%] 0,79 0,01
The BLER is the ratio between NACK
and (ACK + NACK)
The Rtx overhead is the ratio between
the transmitted and the acked bits
Delta CQI could be seen as index of the
CQI adjustment impact
When 0 is received no transmission will
be allowed to the mobile for the following
TTI
128
Integrity KPIs Values– Live Network
RBS
Name
RBS
Sector
RBS
Sector
Carrier
% HS-
BLER
% Rtx
Overhead
MAC
Transmission
Efficiency
RBS23066-01 2 1 0.00% 0.00% 100.00%
RBS37058-01 1 2 4.14% 9.13% 62.87%
RBS37242-01 3 1 8.85% 15.23% 100.00%
RBS23074-01 3 2 9.43% 7.72% 100.00%
RBS05314-01 2 2 10.01% 25.85% 61.83%
RBS04995-01 1 2 11.74% 14.26% 99.89%
RBS01164-01 2 2 12.03% 14.22% 97.41%
RBS05314-01 1 2 12.99% 14.90% 99.12%
RBS01164-01 3 2 13.28% 14.49% 99.97%
RBS01263-01 1 1 13.64% 19.29% 100.00%
RBS23025-01 3 1 14.18% 18.44% 89.32%
RBS37058-01 2 2 14.34% 20.01% 99.89%
RBS00003-01 3 2 15.38% 15.76% 100.00%
RBS37058-01 3 2 18.06% 23.16% 93.56%
RBS34375-01 2 1 18.24% 39.99% 98.14%
RBS01546-01 2 1 18.33% 25.72% 87.02%
RBS00370-01 1 1 18.44% 24.51% 100.00%
RBS00429-01 1 2 19.62% 26.23% 100.00%
RBS32601-01 3 1 21.05% 37.76% 47.37%
RBS23025-01 2 1 22.70% 26.84% 96.60%
RBS34375-01 3 1 23.36% 33.64% 100.00%
RBS01780-01 1 1 23.64% 37.72% 71.70%
RBS00429-01 2 2 24.27% 25.21% 100.00%
RBS00357-01 2 1 25.00% 24.98% 100.00%
RBS34645-01 1 1 27.50% 37.21% 88.80%
RBS00353-01 1 1 28.36% 34.18% 99.35%
RBS34645-01 2 1 30.77% 30.73% 100.00%
RBS01281-01 3 1 33.68% 38.71% 100.00%
RBS01281-01 1 1 38.09% 42.01% 100.00%
129
RBS power
• pmTransmittedCarrierPowerNonHs: The transmitted carrier power for all non high-speed codes in the cell.
• pmTransmittedCarrierPower: the transmitted carrier power measured at the TX reference point every 4 seconds.
• Notes:
– Every 100 ms the transmitted carrier power for all non high-speed codes in the cell are sampled. The problem is that there are not necessary data enough to transmit in every slot: hence some kind of “normalization” should be investigated.
130
0
0.1
0.2
0.3
0.4
0.5
0.6
1.0
1.3
1.6
2.0
2.5
3.2
4.0
5.0
6.3
7.9
10.0
12.6
15.8
20.0
TxCarrierPower
R99Power
Tx Power examples (almost 100% of Scheduling Ratio)
CCH power = 1.7 The Max power = 8.7
The power is calculated at the antenna reference point
131
Transmitted Power (2/2)
• The Average Tx power is:
– Total Carrier = 4.85 W
– R99 power = 1.63 W
– TotalHS_power = 3.22 W
• Note that the HS power is an estimation of the power transmitted for the HS on average during the test period but it is NOT an estimate of the power that HS required in the cell!
– The activity of the HS (when we transmit something) is still low (80%).
– Maybe a more interesting KPI could be:
– TotalHS_power/SchedulingRatio*100
= 100*3.22/81.3 = 3.96 W
• It is interesting to notice anyway that even with a single user the MaxTxPower is reached.
132
RBS list of counters
• pmTransmittedCarrierPowerNonHs: The transmitted carrier power for all non high-speed codes in the cell.
• pmTransmittedCarrierPower: the transmitted carrier power measured at the TX reference point every 4 seconds
• pmNoActiveSubFrames: the number of subframes containing high-speed data transmitted by the RBS.
• pmNoInactiveRequiredSubFrames: the number of empty subframes transmitted even though data is scheduled for priority queue.
• pmSumNonEmptyUserBuffers: The number of user buffers containing high-speed data.
• pmSumAckedBits:the number of Media Access Control high-speed (MAC-hs) bits received and acknowledged by the UE.
• pmSumTransmittedBits: Description The number of transmitted bits at MAC-hs, level including retransmissions
• pmReportedCqi: the Channel Quality Indicators (CQI) reported by the UE in the cell and received by the RBS.
• pmUsedCqi: the CQI, used by the RBS for scheduling the priority queue for the HS-DSCH. pmAckReceived: The number of Acknowledgements (ACK) that the RBS receives from the User Equipment (UE) over the High-Speed Downlink Shared Channel (HS-DSCH).
• pmNackReceived: The number of Negative-Acknowledgements (NACK) that the RBS receives from the User Equipment (UE) over the High-Speed Downlink Shared Channel (HS-DSCH). pmAverageRssi: The average Received Signal Strength Indication (RSSI).
133
Agenda
3. Channel Structure
2. Architecture
1. Overview
5. InterFrequency Mobility Principles
6. KPIs
4. Accessibility & Mobility Principles
6. Capacity Management
RNC KPI
134
• The length of time in seconds that a cell is available for Packet Interactive HS service is defined as cell HS availability. in the example, the cell HS availability during 24 hour period is reported.
1) HS cell Availability (24 Hours period)
Cell Availability (1)
100*3600*24
meMan)pmHsDownti meAutopmHsDownti( 3600*24 ch)Av_HS(Hsds
2) percentage of unplanned HS downtime (24 Hours period)
100*3600*24
meAutopmHsDownti (Hsdsch)Av_Auto_HS
3) percentage of planned HS downtime (24 Hours period)
100*3600*24
meMan pmHsDownti Hsdsch)Av_Man_HS(
135
New
New
New
Accessibility
• The new and existing cell counters used in the PS RAB establishment procedure are given in the following list:
Counter name
pmNoRabEstablishAttemptPacketInteractive
pmNoRabEstablishSuccessPacketInteractive
pmNoRabEstablishAttemptPacketInteractiveHs
pmNoRabEstablishSuccessPacketInteractiveHs
pmNoOutgoingHsHardHoAttempt
pmNoIncomingHsHardHoAttempt
pmNoHsHardHoReturnOldChSource
pmNoHsHardHoReturnOldChTarget
New/existing
Existing
Existing
New
New
New
The number of attempted RAB establishments for PS Interactive RAB
mapped on HS-DSCH (stepped for the selected Serving HS-DSCH cell
at RAB establishment and before possible Inter-Frequency HO).
The number of successful RAB establishments for PS
Interactive RAB mapped on HS-DSCH.
Number of successful Hard HO for serving
HS-DSCH cell selection (in the source cell).
Number of successful Hard HO for serving
HS-DSCH cell selection (in the target cell).
Number of failed Hard HO for serving HS-
DSCH cell selection and UE connection
maintained (in the source cell).
Number of failed Hard HO for serving HS-
DSCH cell selection and UE
connection maintained (in the target cell).
136
Accessibility/ IF counters
137
pmNoRabEstablishAttemptPacketInteractiveHs
Accessibility
• PS Interactive Total RAB establishment, success rate =
100 * pmNoRabEstablishSuccessPacketInteractive
(pmNoRabEstablishAttemptPacketInteractive –
pmNoOutgoingHsHardHoAttempt + pmNoIncomingHsHardHoAttempt
+pmNoHsHardHoReturnOldChSource- pmNoHsHardHoReturnOldChTarget )
PS Interactive HS RAB establishment success rate =
100 * pmNoRabEstablishSuccessPacketInteractiveHs
138
InterFrequency Handover
2) PS Interactive HS Hard Handover incoming success rate
100*AttemptngHsHardHopmNoIncomi
SuccessngHsHardHopmNoIncomi dIn_SPS_M_HSHar
3) PS Interactive HS Hard Handover return to old channel rate (source Cell) 100*
AttemptngHsHardHopmNoOutgoi
dChSourceHoReturnOlpmNoHsHard rcedOldCh_SouPS_M_HSHar
4) PS Interactive HS Hard Handover return to old channel rate (target Cell)
100*AttemptngHsHardHopmNoIncomi
dChTarget HoReturnOlpmNoHsHardget dOldCh_TarPS_M_HSHar
1) PS Interactive HS Hard Handover outgoing success rate
100*AttemptngHsHardHopmNoOutgoi
SuccessngHsHardHopmNoOutgoi dOut_SPS_M_HSHar
5) PS Interactive HS Hard Handover outgoing Lost connection rate
6) PS Interactive HS Hard Handover incoming Lost connection rate
100*
AttemptngHsHardHopmNoOutgoi
dChSource)HoReturnOlpmNoHsHardoSuccessingHsHardH(pmNoOutgo -AttemptngHsHardHopmNoOutgoidOut_Lost PS_M_HSHar
100*
AttemptngHsHardHopmNoIncomi
dChTarget)HoReturnOlpmNoHsHardoSuccessingHsHardH(pmNoIncom -AttemptngHsHardHopmNoIncomidIn_Lost PS_M_HSHar
139
pmInactivityHsIdle
Retainability
• The new and existing cell counters used for Retainability are given in the following list:
Counter name
pmNoSystemRabReleasePacket
pmNoNormalRabReleasePacket
pmChSwitchFachIdle
pmNoTpSwitchSp64Speech
pmNoSystemRbReleaseHs
pmNoNormalRbReleaseHs
New/existing
Existing
Existing
Existing
Existing
New
New
New
The number of signalling connection releases
triggered for PS Interactive RAB mapped on HS-
DSCH due to inactivity (Channel Switching
Evaluation algorithms request the execution of a
switch to idle). The counter is stepped at the reception of RANAP Iu Release
Command from CN, for HS channel cell or RANAP RAB
assignment Request (when the RAB is released) and the RANAP
cause is User Inactivity.
Number of system releases of packet RABs mapped
on HS-DSCH in the Serving HS-DSCH cell.
Number of successful normal releases of packet RABs
mapped on HS-DSCH in the Serving HS-DSCH cell.
140
Retainability
• HS Radio Bearer retainability, drop rate =
100 * pmNoSystemRbReleaseHs
pmNoSystemRbReleaseHs + pmNoNormalRbReleaseHs
Total PS Interactive retainability, drop rate =
100 * ( pmNoSystemRabReleasePacket )
pmNoSystemRabReleasePacket + pmNoNormalRabReleasePacket
141
System Utilization
• It is possible to measure HS A-DCH utilisation in terms of code usage and average number of users per cell.
• Two new set of counters shall be implemented. The first set is used to observe the HS A-DCH code utilisation per cell. The KPI indicates the the total number of A-DCH radio bearers established in a cell.
– ( pmSumPsHsAdchRabEstablish /pmSamplePsHsAdchRabEstablish )
• The second set is used to observe the average number of users per cell (hence the number of HS users), which is done by looking only at the best cell:
– (pmSumBestPsHsAdchRabEstablish /pmSampleBestPsHsAdchRabEstablish )
142
Throughput
143
Throughput
1) Average Throughput for PS interactive HS (RNC Level)
8*
nHs4ketDuratiopmTotalPacnHs3ketDuratiopmTotalPacnHs2ketDuratiopmTotalPacnHs1ketDuratiopmTotalPac
etDataHs4pmSentPacketDataHs3pmSentPack etDataHs2pmSentPack etDataHs1pmSentPack PPintHS_I_T
2) Retransmission Rate for PS interactive HS (RNC Level)
3412
etDataHs4pmSentPacketDataHs3pmSentPack etDataHs2pmSentPack etDataHs1pmSentPack1 etPintHS_I_R
PDHsPDHs
RetransHs2etDataInclpmSentPackRetransHs1etDataInclpmSentPack12P DHs
RetransHs4etDataInclpmSentPackRetransHs3etDataInclpmSentPack34P DHs
Where:
3) HSDPA total RLC data Traffic DL [MByte] (RNC Level)
1000000
etDataHs4pmSentPacketDataHs3pmSentPack etDataHs2pmSentPack etDataHs1pmSentPackATA PintHS_I_D
144
Retrans rate – live RNC
Object NameRetrans Rate
PS Int HS
RNCCN1 99.63%
RNCKS1 99.49%
RNCKS2 100.00%
RNCNY1 98.03%
145
Mobility
• For mobility only the HS serving cell change procedure is considered .
Counter name
pmNoHsCcSuccess
pmNoHsCcAttemptt
New/existing
New
New
The corresponding KPI is
1) Success rate for HS Cell
Change in target cell
Note that no AC is
requested in the cell
change procedure
100*mptpmHsCcAtte
esspmHsCcSucc SPS_M_HSCC_
146
Admission & Congestion Control
• Number of of radio links that are on SF=4 in UL
– pmSumSf4Ul /pmSamplesSf4Ul
• RNC counter monitoring no. of admission rejects (RAB setup) of HSDPA users
– pmNoOfNonHoReqDeniedHs
• RNC counters monitoring no. of HSDPA users (connections) released due to congestion
– pmNoOfTermHsCong & pmNoOfIurTermHsCong