Cell/URA PCH

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Přetížení mobilních sítí,
iPhone efekt,
a co by nás tak ještě mohlo potkat.
For internal use only
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Co je za tím I. ?
• Většina operátorů mobilních sítí nedávno
začala s masivním prodejem
„Smartphones“
Google, iPhone, Nokia 97 ...
• Aplikace, které umožňují uživatelům online
připojení jsou velmi oblíbené
email, instant messaging, presence ...
• Smartphone aplikace zatěžují signalizační
kanály (tzv. Control Plane) daleko více než
standardní služby typu CS, PS a HSPA.
• Zatížení signalizačních kanálů vyžaduje,
aby operátoři mobilních sítí a jejich
dodavatelé WCDMA RAN technologií
přijali určitá opatření.
For internal use only
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Co je za tím II. ?
Výrobci mobilních telefonů :
„Musíme snížit spotřebu,
jinak budou naši
zakázníci nabíjet mobil i vícekrát denně:
Fast Dormancy“
Vývojáři aplikací :
„Naši klienti chtějí být online.
Musíme jim to umožnit:
Keep alive messages“
Uživatel
Operátoři mobilních sítí a jejich dodavatelé technologií :
„Vše pro spokojenost klientů !
Jak ale optimalizovat síť, když do ní stále někdo vrtá“
For internal use only
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Some networks are suffering from Smartphones
For internal use only
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Trocha teorie.
For internal use only
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Radio Resource Control States
RRC Connection
Establishment
Idle Mode
Cell DCH
Cell PCH
Cell PCH
RRC Connection Release
Dedicated Mode
URA PCH
RRC Connection Release
Cell FACH
URA PCH
Cell FACH
For internal use only
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Smart phone impact to HSPA networks
3GPP HSPA Radio Resource Control (RRC) States
3GPP standard
UE power
consumption
Data volumes
1. RRC states in WCDMA RAN are
designed to allow
• low UE power consumption,
• high network efficiency
• low response times to services
2. Large amount of data is carried on
Cell DCH state
3. Small amount of data is carried on
Cell FACH
4. Cell/URA PCH state is used for UE
power saving
>0.5 kB
Cell DCH
>200 mA
<0.5 kB
Cell
FACH
>100 mA
Cell/URA
PCH
<5 mA
IDLE
<5 mA
RAB
setup
= RRC connected
= IDLE
For internal use only
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© Nokia Siemens Networks
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Smart phone impact to HSPA networks
3GPP HSPA RRC State Changes
3GPP standard compliant solution:
1. RRC state changes are controlled
by network parameters
2. Terminal is moved from Cell DCH
to Cell FACH and further to Cell
PCH based on inactivity. The
typical optimized parameters are
2-3 seconds (use of short timers)
3. Optimal parameter settings use
short times and are designed for
low mobile (smart) phone power
consumption and long battery life
NSN RNCs have these features
included since many years
(RAN1.5 onwards, 2003).
For internal use only
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Cell DCH
Data volume
>0.5 kB
Cell
FACH
Cell/URA
PCH
2-3 s
inactivity
2-3 s
inactivity
RAB
setup
Idle
= RRC connected
= IDLE
Smart phone impact to HSPA networks
3GPP HSPA RRC State Changes
3GPP standard compliant solution:
• Cell PCH feature required to optimally
support smart phone behavior. Positive
effects:
1. Less RNC control plane capacity
needed
– Cell PCH state feature provides a
major increase in number of UEs
with RRC connection
– Cell PCH state feature keep UEs in
RRC connection state, no RAB
setup
2. Longer battery life for smart phone
– Complex RAB setup can be avoided
Cell DCH
Cell
FACH
Cell/URA
PCH
2-3 s
inactivity
2-3 s
inactivity
RAB
setup
Idle
from Idle state to Cell DCH state
which consumes lots of control plane
capacity
NSN RNCs have had Cell PCH state
supported for many years
(RAN1.5 onwards, 2003).
For internal use only
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= RRC connected
= IDLE
Cell/URA PCH
Other
network
switching
between
the RRC*
states
Data rate
High
1.
2.
3.
4.
5.
6.
RRCconnReq
RRCconnSetup
L1sync
NBAPsync
UEonDCH
RRCconnSetupCompl
ete
RRC:IDT
RANAP:InitialUEmess
age
RANAP:CommonId
RANAP:SMC
RRC:SMC
RRC:SMComplete
RANAP:SMComplete
RANAP:RABassignme
ntReq
GTPtunnelSetup
RRC:RBsetup
RRC:RBsetupComplet
e
RANAP:RABassignme
ntResp
RRC:MControl(HO)
RRC:MControl(TVM)
UEonDCH but without
u-plane
7.
8.
Low
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
Zero
19.
20.
21.
DCH/HSPA
Long inactivity timer
30 signaling
messages
CELL_FACH
Idle
Idle
2s
Optimized
state
mgmt. by
Nokia
Siemens
Networks
Time
Data rate
High
1.
2.
3.
4.
RRC:CellUpdate
RRC:CUConfirm(CRNTI)
RRC:UMIConfirm
UEonFACH with uplane
4 signaling
messages
Low
CELL_FACH
150 ms
*) RRC: Radio Resource Control
For internal use only
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inactive
PCH
PCH
Zero
Long inactivity timer
Time
Cell/URA PCH
Device power consumption
Other
network
switching
between
the RRC*
states
>200 mA
1.
2.
3.
4.
5.
6.
7.
8.
>100 mA
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
<5 mA
19.
20.
21.
RRCconnReq
RRCconnSetup
L1sync
NBAPsync
UEonDCH
RRCconnSetupCompl
ete
RRC:IDT
RANAP:InitialUEmess
age
RANAP:CommonId
RANAP:SMC
RRC:SMC
RRC:SMComplete
RANAP:SMComplete
RANAP:RABassignme
ntReq
GTPtunnelSetup
RRC:RBsetup
RRC:RBsetupComplet
e
RANAP:RABassignme
ntResp
RRC:MControl(HO)
RRC:MControl(TVM)
UEonDCH but without
u-plane
DCH/HSPA
Long inactivity timer
30 signaling
messages
CELL_FACH
Idle
Idle
2s
Time
Device power consumption
Optimized Data rate
state
mgmt. by
Nokia
Siemens
Networks
>200 mA
1.
2.
3.
4.
4 signaling
messages
CELL_FACH
150 ms
*) RRC: Radio Resource Control
/
inactive
PCH
PCH
<5 mA
For internal use only
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© Nokia Siemens Networks
Low device
power
consumption
with Nokia
Siemens
Networks
RRC:CellUpdate
RRC:CUConfirm(CRNTI)
RRC:UMIConfirm
UEonFACH with uplane
>100 mA
Long inactivity timer
Time
Keep alive messages
aneb
vývojáři aplikací zasahují
For internal use only
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© Nokia Siemens Networks
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Always on applications create control plane load
• Many applications require always on connectivity for a good service
experience.
• In order to maintain always on connectivity applications send keep-alive
messages frequently.
• Keep alive message consumes control plane resources.
• Due to explosion of keep alive messages sent control plane load has sky
rocketed in many WCDMA networks
Keep alive messages make RNC change UE states frequently
Cell DCH
state
Cell PCH / IDLE
Keep alive messages
For internal use only
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© Nokia Siemens Networks
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Fast Dormancy
aneb
výrobci mobilních telefonů zasahují
For internal use only
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Pohled účastníka mobilní sítě: moje priority
"future of mobility" survey
Klíčové potřeby účastníka
0%
20%
40%
60%
80%
100%
Zlepšená životnost baterie
Fixní cena za přístup k internetu
Nižší cena za mezinárodní roaming
Voice over IP (VoIP)
Zlepšený procesní výkon zařízení
Zlepšené pokrytí v méně obydlených oblastech
Aktivní “multiple SIM“ karta ve stejném zařízení
http://www.theregister.co.uk/2007/11/19/mobile_experience/
For internal use only
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Sudden changes in behaviour can happen
In Smart phone dominated network changes can happen overnight, caused by
new firmware or killer application
For example iPhone user-friendly firmware upgrade makes upgrades unheard fast:
in one network 50% of phones were upgraded within 1 week after the new
firmware came available – boosting the impact of new firmware
For internal use only
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Smart phone impact to HSPA networks
What Went Wrong? – Why Fast Dormancy was introduced
Why is Cell PCH state needed in RNC?
1. When Cell PCH is not supported, operators
are forced to use long timers to avoid
frequent RAB setups
– That leads to high UE power
consumption with always-on
applications
2. When UE power consumption was high,
some UE vendors implemented so called
“Fast Dormancy” functionality which
releases RRC/RAB connection when data
transmission is over.
DCH/
HSPA
Long timer
FACH
Long timer
PCH
RRC
idle
3. Frequent RAB release/setups causes
problems for network (RNC) capacity.
Only NSN implemented Cell PCH state in their RNC (2003). Many operations
are using Cell PCH power saving state
For internal use only
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A co dál ?
For internal use only
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3GPP Solution
• 3GPP Release 8 (TS 25.331) specified, network
controlled Fast Dormancy functionality clarifying
the UE behavior and providing the network with
information of what the UE actually wants to do,
but leaving the network in charge of the UE RRC
state.
• That is, the UE is not allowed to release RRC
connection and move to idle state on its own
without network control.
• When RNC receives SCRI from UE with a special
newly introduced cause value indicating the packet
data session end, the RNC can command the UE
to PCH state instead of releasing RRC connection
and dropping the UE to idle state.
• Not yet implemented in networks, nor UEs
For internal use only
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A co třeba úplně nová síť LTE ?
TX
Velmi rychlý
“Link
Adaptation“
(modulace dle
kvality kanálu)
MIMO
Tx Channel Rx
64QAM
Modulace
variabilita v šířce pásma
Krátký TTI = 1 ms
Transmission time
interval
HARQ: Hybrid
Automatic Repeat Request
DL: OFDMA
1
2
NACK
ACK
UL: SC-FDMA
1
Combined
2 decoding
Rx Buffer
For internal use only
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RX
Advanced Scheduling
Time & Freq. (Frequency
Selective Scheduling)
Děkuji
For internal use only
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