QoS QoS Issues in GPRS/UMTS Networks Issues in GPRS/UMTS Networks Shiao-Li Charles Tsao (曹孝櫟) Computer & Communications Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan, R.O.C. (工研院電通所) [email protected]TEL:886-3-591-4651 FAX:886-3-5820310
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QoS QoS Issues in GPRS/UMTS NetworksIssues in GPRS/UMTS Networks
Shiao-Li Charles Tsao (曹孝櫟)
Computer & Communications Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan, R.O.C.
• Why QoS ?• End-to-End QoS Architecture• QoS in GPRS Networks• QoS in UMTS Networks• QoS in 3G All IP• End-to-End QoS in Heterogeneous Wireless Network• Conclusions
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Why Why QoS QoS ??
• What is QoS ?– Quality of Service is a mechanism that provides a level of
assurance that ensures that a service or application can be delivered to the end-user in a satisfactory time frame (QoSforum)
– Depending on different users and different APs– does not create additional bandwidth– manages the existing bandwidth in more efficient way– allows for predictable delays, delay variation (jitter) and
packet loss rates
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WhyWhy QoSQoS ? (Cont.)? (Cont.)
• Why we need QoS ? – Consistent and predictable to real-time and non-real-time
service above a minimum level– Unique problems for wireless communication
• bandwidth-limiting (engineering approaches to solve QoSproblem over fixed network fail)
• error-prone (retransmission is what we always do over fixed network, but it costs too much over wireless network)
• time-variant
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WhyWhy QoSQoS ? (Cont.)? (Cont.)
• Do we need application QoS or end-to-end QoS ?– YES. That is why we need QoS
• QoS architecture– ATM QoS– IP QoS architecture
• MPLS, IntServ, DiffServ– QoS for optical networks
3 Modify PDP Context Req. (QoS Neg., Radio Priority) through neg. LLC SAP
MS either accepts the QoS or deactivates the PDP
context
4 Modify PDP Context Acpt.
SGSN selects radio priority based on QoS negotiated
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QoSQoS in GPRS Networks (Cont.)in GPRS Networks (Cont.)
• QoS during Handover (Inter-BSS)
SGSNMS New BSS GGSN Host
1 Data PacketsOld BSS
Data packet through the specific LLC SAP and to RLC/MAC with QoS profile and radio priority to new BSS
2 Data Packets
Data packet through the specific LLC SAP and to RLC/MAC with QoS profile and radio priority
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QoSQoS in GPRS Networks (Cont.)in GPRS Networks (Cont.)
• QoS during Handover (Inter-SGSN)
Old SGSNMS BSS GGSN Host
1 RA Update Req.
2 SGSN Context Req./Rsp./Ack. (QoS profile)
New SGSN
3 Update PDP Context Req. (QoS(QoS Neg.Neg.)
4 Update PDP Context Rsp. (QoS(QoS Neg.Neg.)
5 RA Update Acpt./Complete…
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QoSQoS in GPRS Networks (Cont.)in GPRS Networks (Cont.)
MS BSS SGSN GGSN
IP/X.25
Application
Host
Radio Priority
PDP Context (QoS Profile)PDP Context (QoS Profile)• QoS control and maintenance
L2L1
LLC QoS 1~4 SAP (delay class)Flow/Congestion Control
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QoSQoS in GPRS Networks (Cont.)in GPRS Networks (Cont.)
Flow control over frame relay
MS BSS SGSN GGSN
L1L2
IP/X.25
Application
Host
TCP/UDP Flows : no differentiated
Associate with PDP context based on PDP address
Through specific LLC SAPs based
on QoS delay class
QoS control based onQoS profiles and radio priorities
• Packet flow
IP QoS based on PDP context (QoS profile)IP QoS based on PDP context (QoS profile)
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QoSQoS in GPRS Networks (Cont.)in GPRS Networks (Cont.)
• Difficulties of QoS control in GPRS Networks– TDMA radio
• Best effort traffic• Shared capacity, no fixed reservation• Non-optimized handover for real-time packets
– BSS knows nothing about PDP context (QoS Profile)• Mapping complicated QoS profile into 4 priorities (LLC and
radio priorities)– No QoS mechanisms standardized on core network
• QoS mechanisms can be applied to core network, but the bottleneck is in radio interface
– One QoS profile per PDP address• No per flow QoS
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QoSQoS in UMTS Networksin UMTS Networks
• Why QoS in UMTS is important ?– 1G cellular system (AMPS)
• analog voice/circuit switch (radio network)– 2G cellular system (GSM)
• digital voice/circuit switch (radio network)– 2.5G cellular system (GPRS)
• digital data/packet switch (radio network)• Address QoS issues but not required to implement
– 3G cellular system (3GPP R99/R4)• digital voice/data/packet switch (radio network)• WCDMA introduced•• QoS QoS features are design in and ready for providing packet voicefeatures are design in and ready for providing packet voice
– Beyond 3G (3GPP R5/R6)• digital voice/data/packet switch (radio and core network)
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QoSQoS in UMTS Networks (Cont.)in UMTS Networks (Cont.)
• General ideas - Initiate
HLRRNC
1 : Subscribe time2 : Attach
UE
3 : PDP Context Activation
5 : RL/RB establishment
5‘ : RRM to map QoS to channels
SGSN GGSN
3‘ : IP QoS session mapping & establishment
4 : RAB establishment
4‘ : IP QoS session mapping & establishment
5 : PDP Modification if required
5‘ : IP QoS re-mapping if required
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QoSQoS in UMTS Networks (Cont.)in UMTS Networks (Cont.)
• General ideas – Modify and Roaming
RNC
1: Inter NodeB, RNC handovers
UE SGSN GGSN
2‘ : IP QoS session re-mapping & establishment
RNC
2 : Inter SGSN RAU
SGSN
1‘:RRM involved
RNC
3 :PDP Context Modification
3‘ : IP QoS session re-mapping & establishment
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QoSQoS in UMTS Networks (Cont.)in UMTS Networks (Cont.)
MobileMobile--initiated or initiated or networknetwork--initiated initiated
handoffs for handoffs for Seamless roamingSeamless roaming<<ietfietf--fastfast--mipv6>mipv6>
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EndEnd--toto--EndEnd QoSQoS in Heterogeneous in Heterogeneous Wireless Network (Cont.)Wireless Network (Cont.)
• QoS Problems for Intersystem Handoffs
InternetInternet
SGSN GGSN
SGSN GGSN
Packet radio networkPacket radio network
Router Gateway
Router Name Server
Wireless networkWireless network
Name Server
DHCP Server
MS
MS
HA/FA
HA/FA
Host
QoSQoS profile profile needs to be needs to be transferred transferred
during handoffsduring handoffs
Resource alone the new Resource alone the new routing path should be routing path should be reserved in advanced reserved in advanced
for some for some APsAPs
QoS QoS Profile should be Profile should be renegotiated with new renegotiated with new systems and translated systems and translated to new to new QoS QoS profileprofile
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ConclusionsConclusions
• GPRS suffers from design defects to support QoS• Maybe it is not required to build in QoS features in GPRS
– Radio interface is the bottleneck– The range of the QoS that radio interface can offer is quite different
from these of the fixed network. It does not make sense to map two scales which have a large gap
•• QoSQoS is required for 3G and is a MUST for B3Gis required for 3G and is a MUST for B3G• QoS features for 3G system such as UMTS has already designed has already designed
inin•• Take Take QoS QoS into consideration for 3G productsinto consideration for 3G products or deployment deployment
of 3G system of 3G system –– will also help you to move to B3G smoothlywill also help you to move to B3G smoothly