QoS in Wireless Networks ELG5125 Presentation Author: Thanh Cao email: thanhkcao@gmail Date: November 29, 2005 - PowerPoint PPT Presentation

• Report on schemes, specification to ensure, manage QoS in third- generation (3G) wireless networks, specifically in:
• UMTS QoS,
• End-to-end QoS.
• QoS mapping

• Evolution towards 3G
• Factors affecting QoS
• QoS Techniques
• Specifications
• Converting transport to IP
• IP mapping
• Conclusion

• Higher data rates (up to 2 Mbps)
• Supports QoS
• Based on standardized protocols, interfaces
• “unifies” competing protocols, technologies
• Offers multimedia services: voice, data, video
• Based on data packets, packet switching
• Data traffic will be dominating
• Evolving toward all-IP networks

• TDMA evolves into 3G wireless by UWC-136, which is based on IS-136/IS-136+ and IS-136 High Speed (IS-136HS).
• IS-136+ improves the voice and data services which currently use the existing 30-kHz channel bandwidth.
• IS-136+ packet data service is based on the GSM General Packet Radio Service (GPRS) architecture.
• IS-136 High Speed (IS-136HS) has two flavors: outdoor/vehicular and indoor.
• The outdoor 136HS is similar to the Enhanced Data rates for GSM Evolution (EDGE), and provides bit rates up to 384 kbps.
• The indoor 136HS provides bit rates up to 2 Mbps.

• IS-95, often referred to as North American CDMA (NA-CDMA), has two migration paths: IS-95B and cdma2000.
• Both IS-95B and cdma2000 provide smooth transition to IMT-2000 while maintaining backward compatibility with existing IS-95 infrastructure.
• IS-95B provides enhanced data rate by allowing transmission/reception of data on multiple channels.
• data rate up to 76.8 kbps or 115.2 kbps in either the uplink or downlink direction.
• Cdma2000 or wideband cdmaOne
• Further enhancement of IS-95B,
• Uses multi-carriers,
• includes wider channel bandwidth, a pilot channel, and power control

• GSM networks will enhance data services in three phases: General Packet Radio Services (GPRS), Enhanced Data rates for GSM Evolution (EDGE) and Wideband CDMA (WCDMA).
• GPRS allows GSM mobile subscribers to connect to an IP-based or X25-bases networks.
• EDGE has been approved by ETSI and UWCC as the outdoor/vehicular component of IS-136HS.
• EDGE is backward compatible with GSM/GPRS infrastructure.
• Wideband CDMA introduces a new air interface based on 5-MHz channel bandwidth.
• WCDMA is adopted as the air interface for 3G wireless (IMT-2000)
• See IMT-2000 next

• International Mobile Telecommunication (IMT-2000)
• An ITU development activity with contributions from:
• Japan: Association for Radio Industry and Business (ARIB)
• EU: European Telecommunications Standard Institute (ETSI)
• USA: Telecommunications Industry Association (TIA)
• Korea: Telecommunications Technology Association (TTA)
• A family of standards that will provide at least
• 384 kbps at pedestrian speed,
• 144 kbps at mobile speed,
• Up to 2 Mbps indoor.
• Adoption of Wideband CDMA with three optional modes:
• Direct Sequence Frequency-Division Duplex (ETSI, ARIB)
• Multi-carrier FDD (TIA)
• Direct Sequence Time-Division Duplex (ETSI)

Analog

2G

2.5G

3G

• “first” generation
• only voice services offered

• move to digital,
• radical changes to architecture and components,
• main services: voice, text-based short message service (SMS)

• intermediate technology
• modifications to 2G phone architectures (e.g. GPRS from GSM),
• more advanced data services.

• IMT-2000 standard,
• data rates from 144 kbps to 2 Mbps,
• enhanced multimedia messaging,
• MPEG-4 video,
• location-based services (GPS-enabled),
• mobile computing

Summary of Wireless Evolution

Source: RD Gitlin, “Next Generation Wireless Networking Presentation,” 2003, Columbia University.

• IP QoS technologies have moved beyond “Best effort”; wireless must interoperate with IP QoS; therefore wireless must provide QoS.
• New coming services requiring QoS:
• Streaming applications need throughput and delay guarantees,
• Real-time applications (e.g. multimedia) need low delay,
• Other applications with different QoS requirements.
• Network Operators:
• Efficient use of network resources: avoid over-provisioning
• Service differentiating: offering Service Level Agreement
• Major QoS components: throughput, delay, jitter, error rates

• QoS of wireless network is affected by the following:
• Attenuation,
• Multi-path interference,
• Spectrum interference: for example spread-spectrum interferences from neighboring cells,
• Noise: Noise sources can be natural and man-made such as radio, TV and other radio-frequency transmission,
• Mobility: affects hand-over and resource utilization, management,
• Limited capacity: resources are costly.
• Higher error rates are typical
• QoS schemes must interact with those already in use in the Internet

Packet arrival

Monitoring

(QoS Parameters)

Mapping

Admission

control

Scheduling & resource allocation

Channel Condition (from physical layer)

QoS mechanisms: - mapping, admission control, scheduling, resource allocation.

- have to monitor and react to the environment in real time

• Admission Control: Limits number of flows admitted into the network so that each individual flow obtains its desired QoS.
• Scheduling:
• Scheduling affects delay, jitter and loss rate.
• Allows protection against misbehaving flows.

• Buffer Management: Controls the buffer size and decides which packets to drop.
• Controls packet loss rate.
• There are many packet drop strategies including weighted Random Early Detection (RED).
• Congestion Control: Prevents, handles and recovers from network congestion scenarios.

Traffic Class

Conversational

Streaming

Interactive

Background

Fundamental Characteristics

Conversational pattern (low delay)

Preservation of time relation between info entities

Preservation of time relation between info entities

Expect response to request

Preservation of payload contents

Destination does not expect data within a certain time

Preservation of payload contents

Application examples

Voice, voice over IP, video conferences

Streaming audio, video

Web browsing

Emails, SMS, background download

UMTS QoS Traffic Classes and Applications (Ref [5])

Traffic Class

Conversational

Streaming

Interactive

Background

Max bit rate (kbps)

2,000

2,000

2,000 - overhead

2,000 - overhead

Delivery order

Yes/no

Yes/no

Yes/no

Yes/no

Max SDU size

<= 1500, 1502

<= 1500, 1502

<= 1500, 1502

<= 1500, 1502

SDU format info

TBD

TBD

SDU error ratio

10-2, 7*10-3, 10-3, 10-4, 10-5

10-1, 10-2, 7*10-3, 10-3, 10-4, 10-5

10-3, 10-4, 10-6

10-3, 10-4, 10-6

Delivery of erroneous SDU

Yes/no

Yes/no

Yes/no

Yes/no

Transfer delay (ms)

100 (max)

300 (max)

Guaranteed bit rate

<= 2,000

<= 2,000

Traffic handling priority

1,2,3

Allocation/retention of priority

1,2,3

1,2,3

1,2,3

1,2,3

Source stats descriptor

Speech/unknown

Speech/unknown

Signaling indication

Yes/no

Attribute Value Ranges for UMTS Bearer Attributes (Ref [5])

• UMTS – Radio Access Bearer mapping:
• Same values between UMTS and Radio Access Bearer: max bit rate, delivery order, delivery of erroneous SDUs, guaranteed bit rate, traffic handling priority, maximum SDU size, SDU format information.
• Left as an implementation issue: residual BER, SDU error ratio, transfer delay, SDU format information, and source statistics descriptor.
• Other Attribute Mappings
• Attribute mapping from application attributes into UMTS bearer service is left as an operator or implementation issue.
• Attribute mapping from UMTS bearer service to CN bearer service is left as an operator issue.

Core Network

RNS

SRNC

RNS

SRNC

CRNC

CRNC

RAN

Node B

Node B

Node B

Node B

Node B

Node B

UE

RAN consists of many RNS, among which UE can roam (Ref [9])

• Current UMTS Terrestrial Radio Access Network (UTRAN) uses AAL2/ATM technology.
• Cases for IP as transport technology:
• IP QoS is approaching maturity
• IP network layer is independent of link, physical layers so it can support a wide selection of lower layers
• IP is becoming basis for packetization of voice, data, signaling, operation, administration and management (OAM) functions,
• 3G Core Network is already mostly IP-based.

• There are several IP QoS technologies: over-provisioning, DiffServ, IntServ, MPLS, RSVP
• IntServ: fine control resolution, not scalable
• DiffServ: simple management, scalable
• DiffServ: allows network operators to offer different QoS to different traffic streams
• Prioritizes via DiffServ Code Point (DSCP) in IP header,
• Aggregates traffic into Per Hop Behavior (PHB) groups
• Two types of routers: edge and core
• Pushes complexity to edge routers (classification; policing, shaping, scheduling traffic)
• Simple core routers process based on PHB. Basic PHBs: Premium Forwarding/Expedite Forwarding (PF/EF), Assured Forwarding (AF), Best Effort (BE)

• Therefore, IP is being considered for UTRAN, facilitating end-to-end QoS, signaling, OAM.
• Mobile Wireless Internet Forum studied and concluded that IP is a viable transport option (Ref [9])
• Challenges: tight end-to-end delay, jitter, low packet loss ratio

• QoS in core network is left mostly to the operators:
• Which and where QoS capabilities are implemented,
• Mapping between DiffServ code points and UMTS traffic classes,
• Inter-operation between operators will be based on Service Level Agreement

• Proposal for mapping UMTS Traffic Classes to IP DiffServ:
• Ref [8] proposes Resource Control Layer (RCL) to expand UMTS Interactive traffic class due to:
• Traffic handling priority
• Packet loss rate
• Ref [8] proves that QoS is handled more efficient when UMTS QoS classes are mapped to RCL classes than mapping UMTS QoS directly to DiffServ classes.

UMTS Class

RCL

DiffServ

Characteristics

Conversational

PCBR

AF and EF PHBs

Max bit rate (kb/s)

< 2048

Max. per flow 200

Max packet size (bytes)

=< 1500, 1502

256

Packet error ratio

10-2, 7*10-3, 10-3, 10-4, 10-5

< 10-8

Transfer delay (ms)

100 (max)

150 (max)

Streaming

PVBR

AF4

Max bit rate (kb/s)

< 2048

Max. per flow 1000

Max packet size (bytes)

=< 1500, 1502

1000

Packet error ratio

10-1, 10-2, 7*10-3, 10-3, 10-4, 10-5

< 10-6

Transfer delay (ms)

250 (max)

250 (max)

Interactive

PMMPMC

AF3

Max bit rate (kb/s)

< 2048 - overhead

Max. per flow 250Max. per flow 50

Max packet size (bytes)

=< 1500, 1502

1500 1500

Packet error ratio

10-3, 10-4, 10-6

<10-3 < 10-4

Traffic handling priority

1, 2, 3

1 2, 3

Background

PMCBE

AF2 or AF1 or BE

Max bit rate (kb/s)

< 2048 - overhead

Max. per flow 50 No QoS

guarantees

Max packet size (bytes)

=< 1500, 1502

1500

Packet error ratio

10-3, 10-4, 10-6

< 10-4

• IMT-2000 tries to include, unify, inter-operate, standardize diversified and competing protocols, technologies,
• 3GPP defines a QoS framework
• We are evolving toward all-IP solution
• Many issues are still unresolved or intentionally left as “implementation, operator issues”
• QoS in the Air Interface is still unresolved.

[1] Chen L., Kayama H., Umeda N., “Power Resource Cooperation Control Considering Wireless QoS for CDMA Packet Mobil Communication Systems,“ The 13th IEEE International Symposium on Personal, Indoor, and Mobile Radio Communication, 2002.

[2] Dahlman E, Beming P, Knutsson J, Ovesjo F, Persson M, Roobol C, “WCDMA – The Radio Interface for Future Mobile Multimedia Communications,” IEEE Transactions on Vehicular Technology, Vol 47, No. 4, November 1998.

[3] Desposito J, “A Bump in the Path to 3G,” Electronic Design Online ID #3467, May 15, 2000.

[4] Dixit S, Guo Y, Antoniou Z, “Resource Management and Quality of Service in Third Generation Wireless Networks,” IEEE Communications Magazine Feb 2001, pp 125 – 133.

[5] ETSI, 3GPP, “Quality of Service Concept and Architecture,” 3GPP TS 23.107 version 6.3.0 Release 6.

[6] ETSI, 3GPP, “End-to-End Quality of Service Concept and Architecture,” 3GPP TS 23.207 version 6.6.0 Release 6.

[7] Guo JY, Chaskar H, “Class-Based Quality of Service over Air Interfaces in 4G Mobile Networks,” IEEE Communications Magazine, March 2002, pp 132 - 137.

[8] Maniatis SI, Nikolouzou EG, Venieris IS, “QoS Issues in the Converged 3G Wireless and Wired Networks,” IEEE Communications Magazine, August 2002.

[9] Mobile Wireless Internet Forum, “IP in the RAN as a Transport Option in 3rd Generation Mobile Systems,” Release 2.0.0, Reference number MWIF 2001.084.

[10] Saud L.C., Limos R.P., “Third Generation Mobile Wireless Networks Quality of Service, with a 2.5G Case Study Using Differentiated Service,” IEEE/Sarnoff Symposium on Advances in Wired and Wireless Communications, April 26 – 27, 2004, pp 71-74.