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Bader Al-Manthari, Nidal Nasser, and Hossam Hassanein,“Downlink Scheduling With Economic Considerations for Future Wireless Networks,” IEEE TRANSACTIONS ON VEHICULAR TE

CHNOLOGY, Vol. 58, No. 2, FEBRUARY 2009.

Advisor： Yeong-Sung LinStudent： Chiu-Han Hsiao

Department of Information ManagementNational Taiwan University

Taipei, Taiwan, R. O. C.

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Outline Introduction Background Study

Problem Description and System Model

Centralized Downlink Packet Scheduler (CDPS)

Performance Evaluation

Experiment Result

Conclusion

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Introduction(1/2)

3G Universal Mobile Telecommunication System (UMTS)(2Mbps)

High-Speed Downlink Packet Access (HSDPA) (3.5G) can theoretically support up to 14.4 Mbps, which is seven times higher than the data rate offered by UMTS

A key component of radio-resource management (RRM) is packet scheduling, which is responsible for distributing the shared radio resources among the mobile users

we propose a novel centralized downlink packet scheduler (CDPS) scheme to be implemented at the base stations of future wireless cellular systems

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Introduction(2/2)

CDPS utilizes an opportunity cost function that allows service providers to control its degree of fairness and hence control the system capacity

CDPS is designed to balance between the requirements of connections (e.g., throughput, fairness, etc.) and the requirements of service providers (e.g., revenues)

CDPS can be configured to reduce to the maximum carrier-to-interference ratio (Max CIR) and proportional fairness (PF) schemes

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Background Study

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Multiple Access Methods

Multiple users share the available spectrum

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What is “IMT-2000”

IMT-2000 (Internet Mobile Telecommunications-2000) is the personalized global multi-media service, which unifies all the various mobile telephone system specs

Services– global roaming service

– multimedia communications

This is “ 3rd Generation Mobile Communication System”

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IMT-2000

ITU (International Telecommunication Union)IMT-2000

• Year 2000 Ready

• Operate at 2000 MHz

• Provide 2000K bps Data Rate

3G Data Rate Requirement• Vehicular -- 144 Kbps

• Pedestrian --- 384 Kbps

• Indoor --- 2Mbps

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IMT-2000 Evolution

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IMT-2000 Evolution

PDC

GSM

ARIB (W-CDMA)

GPRS

UTRA (W-CDMA)

EDGE

Wideband CDMA

TD-CDMA(TDD)

MulticarrierMulticode

W-CDMA(FDD)

AMPS IS-54

cdmaOne(IS-95)

IS-136

136+

136 HS

UWC-136

cdma2000

IS-95B

PDC

GSM

ARIB (W-CDMA)

GPRS

UTRA (W-CDMA)

EDGE

Wideband CDMA

TD-CDMA(TDD)


W-CDMA(FDD)

TD-CDMA(TDD)


W-CDMA(FDD)

AMPS IS-54

cdmaOne(IS-95)

IS-136

136+

136 HS

UWC-136

cdma2000

IS-95B

AMPS IS-54

cdmaOne(IS-95)

IS-136

136+

136 HS

UWC-136

cdma2000

IS-95B

• AMPS: Advanced Mobile Phone System• GSM: Global Systems for Mobile Comm.• GPRS: General Packet Radio Service• PDC: Personal (or Pacific) Digital Comm.• EDGE: Enhanced Data rates for GSM

(or global) Evolution• UTRA: UMTS Terrestrial Radio Access

• IEEE Spectrum, Aug. 1999 (Modified)

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IMT-2000 Terrestrial RTT Standardization

CDMA2000 (North America)– Based on Qualcom cdmaOne

– Support multi-carrier (MC)

– Use IS-41 to accomplish the core network compatibility

TD-SCDMA (Mainland)– 大唐電信 and Siemens

– TDD-based

– Requirement : time synchronization

– Limit coverage area of BS

WCDMA/UMTS (Japan and Europe)– NTT DoCoMo develops WCDMA

– Core network is based on GSM system

– UTRA (UMTS Terrestrial Radio) proposed by Europe is similar as WCDMA

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Network Upgrade Comparison: CDMA2000 1x vs. GPRS / W-CDMA

SGSN: Serving GPRS Support Node

GGSN: Gateway GPRS Support Node

MSC: Mobile Switching Center

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New Terms

WCDMA/UMTS Terms– BTS → Node B (NB)

– BSC → RNC (Radio Network Controller)• New job : RRM (Radio Resource Management)

Radio BearersChannels

– Logical Channel

– Transport Channel

– Physical Channel

Data forwarding direction– Uplink (reverse link)

– Downlink (forward link)

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3G Frequency Allocation in Taiwan

E

825

E

845

870

890 MHz

A BCBA C D D BA C D

191

5

20

197

5

35

45

60

201

0

202

5

15

20

ITU IMT-20001885MHz 2025MHz

ITU IMT-20002110MHz 2200MHz

21

10

216

5

25

35

50 MHz

3G 執照頻寬頻帶 (MHz)

A 2 x 15 MHz + 5 MHz 1920 ~ 1935, 2110 ~2125, 1915 ~ 1920

B 2 x 10 MHz + 5 MHz 1935 ~ 1945, 2125 ~ 2135, 2010 ~ 2015

C 2 x 15 MHz + 5 MHz 1945 ~ 1960, 2135 ~ 2150, 2015 ~ 2020

D 2 x 15 MHz + 5 MHz 1960 ~ 1975, 2150 ~ 2165, 2020 ~ 2025

E 2 x 20 MHz 825 ~ 845, 870 ~ 890

Apple - iPhone - 技術規格.htm

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WCDMA Standards

3GPP– www.3gpp.org

WCDMA– FDD mode– TDD mode

Release– R98 (1998)– R99 (200003 freeze) --- WCDMA– R4 (200103 freeze)– R5 (2002 freeze) --- HSDPA– R6 (2003 freeze) --- HSUPA– R7 (2007 freeze)– R8 (2008 freeze) --- LTE– R9 (ongoing)– R10 (ongoing) LTE: Long Term Evolution

http://www.3gpp.org/

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History (1/2)

Release 98 (1998)– This and earlier releases specify pre-3G GSM networks

Release 99 (2000 Q1)– Specified the first UMTS 3G networksfirst UMTS 3G networks, incorporating a CDMA

air interface

– USIM : mutual authentication (AKA)Release 4 (2001 Q2)

– Originally called the Release 2000 - added features including an All-IP Core Network

Release 5 (2002 Q1) – Introduced IMS and HSDPAHSDPA

Release 6 (2004 Q4 )– Integrated operation with WLAN networks and adds HSUPAHSUPA,

MBMS, enhancements to IMS such as Push to Talk over Cellular (PoC)

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History (2/2)

Release 7 (2007 Q4)– Focuses on decreasing latency, improvements to QoS and real-t

ime applications such as VoIP – also focus on HSPA+HSPA+ (High Speed Packet Access Evolution), M

IMO, SIM high-speed protocol and contactless front-end interface (Near Field Communication enabling operators to deliver contactless services like mobile payments), EDGE Evolution.

Release 8 (In progress, not ready before Mar 2009)– LTELTE, All-IP Network (SAE).All-IP Network (SAE). It constitutes UMTS as an entirel

y IP based fourth-generation network. Release 9 (In progress, expected to be frozen in Dec 200

9 )– SAES Enhancements, WiMAX and LTE/UMTS Interoperability

Release 10 (In progress) – LTE-AdvancedLTE-Advanced

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3GPP Development Progress

Functionality

Time1999 -12 2001 -03 2002 - 03/06

Release 1999Release 1999

Release 4Release 4

Release nRelease n

Release 5Release 5

UTRA FDD/TDD

modes, USIM,

AMR speech

codec, MMS,

LCS,

CAMEL etc.

LCR TDD,

UTRA FDD

repeater function,

700MHz support

for GERAN

IMS phase 1,

HSDPA,

Wideband AMR,

IP transport

in UTRAN

WLAN/UMTS

Interworking ,

IMS phase 2

Release 6Release 6

2003/12

OFDM?

MIMO?

EDCH?

IMS further

Phase?

Time1999 -12 2001 -03 2002 - 03/06


Release 4Release 4

Release nRelease n

Release 5Release 5

,

Release 6Release 6

2003/12- - -


Release 4Release 4

Release nRelease n

Release 5Release 5MBMS,

,

Release 6Release 6

HSUPA,

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3GPP’s Evolution/Revolution Towards 4G

3GPP R4(WCDMA) 3GPP R5

(+HSDPA)

3GPP R5(+HSDPA)

3GPP R63GPP R6(+HSUPA)

3GPP R7(+MIMO)

3GPP R7(+MIMO)

IMT - 2000

2001/11/04 2002/06/24

EnchancedIMT - 2000

2003/09/26 2005/01/04

NewMobileAccess

R8LTE

OFDMA

3GPP R4 3GPP R5 3GPP R6 3GPP R7 3GPP R8Data Rate

(peak)

Systems

Forward Link

Reverse Link

2 Mbps

384 Kbps

> 10 Mbps

384 Kbps

> 10 Mbps

> 2 Mbps

> 20 Mbps

> 5 Mbps

100 Mbps

20 Mbps

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Radio Resource Management

CDPS is proposed

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Channel quality condition for scheduling decisions

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Packet Scheduler Model

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System Formulation

we emphasize recent scheduling schemes for data (non–real-time) services in future wireless cellular networks

the base station simultaneously serves n connections n ≥ 1 and selects one or more connections for transmission in a frame of some fixed time duration

These PDUs are stored in the transmission queue of the corresponding connection in a first-in–first-out fashion

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Utility Function

The user’s i (1 ≤ i ≤ n) preferences at time t as perceived by the service provider can be expressed by a utility function Ui(Xi1(t),Xi2(t), . . . , Xim(t)), – where n is the total number of users’ connections in the

system, – Xi1(t), . . . , Xim−1(t) are the chosen quantitative measures

of the user connection’s preferences in this system such as the average throughput, current data rate, average delay, etc.,

– Xim(t) is a fairness measure that represents how fair the scheduling scheme is to the user connection, and m is the maximum number of chosen quantitative measures.

We assume that the utility function is additive

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Objective Function

OCi(t) is the opportunity cost of serving connection iat time t, and K is a predefined constant value

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Cobb–Douglas Utility Function for Downlink Scheduling

Cobb-Douglas生產函數：簡稱 C-D生產函數

　最簡單之形式如： Q = AKαLβ

　

　式中 Q：產出量， K：資本使用量， L勞動使用量， A 、 α 及 β表固定常數，其數值可由實際統計資料估計出

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Cobb–Douglas生產函數

1. 若 α +β>1，則此生產為遞增的規模報酬；即若所有生產要素按相同比例增加，則產量增加的比例大於生產因素增加的比例。如：Q = 20K0.7L0.6

2. 若 α +β=1，則此生產為固定的規模報酬；即產量增加的比例等於生產因素增加的比例。例： Q = 50K0.4L0.6

3. 若 α +β<1，則此生產為遞減的規模報酬；即產量增加的比例小於生產因素增加的比例。例： Q = 100K0.5L0.3

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Definitions of Xi1(t) and Xi2(t)

Assuming m = 2 in our formulation of CDPS, the Cobb–Douglas utility function is expressed as Ui

(X1,X2) = X1c ·X2

d

– where c, d ≥ 0. Let X1 be any performance metric that the service provider wants to optimize, such as the average connection throughput or average delay. Let X2 be a fairness measure that increases as the connection’s or system’s perception of fairness increases, which results in an increase in U

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To maximize the system’s overall utility, we need to achieve the highest possible values of Xi1(t) and Xi2(t) for all connections.

However, it is not possible to achieve high values of both Xi1(t) and Xi2(t) for all connections because of the tradeoff between capacity and fairness

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Given these two definitions, the fairness measure for connection i at time t, αi(t) can be defined

Si(t) is the average throughput for connection i up to time t

maxj Sj(t) is the maximum average throughput achieved among all connections up to time t.

the fairness measure for connection i is the ratio of its average throughput to the maximum throughput achieved among all the connections in the system. We call this measure the “relative fairness.”

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The opportunity cost of serving connection i at time t (i.e., the opportunity cost of fairness) is defined as

where Ri(t) is the current data rate for connection i at time t, which depends on its channel condition,

maxj Rj(t) is the maximum current data rate of all connections at time t

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c: the Cobb–Douglas utility function’s constant, where c ≥ 0. The value of this constant determines the weight on Xi1(t) in the Cobb–Douglas utility function

d: the Cobb–Douglas utility function’s constant, where d ≥ 1. The value of this constant determines the weight on Xi2(t) in the Cobb–Douglas utility function.

We restrict the value of this constant to an odd integer because our defined Xi2(t) in the adopted Cobb–Douglas utility function is a negative function

d must be odd

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Xi1(t) = Ri(t): the current data rate of connection i at time t

The utility of connection i being served increases as Ri(t) increases. It should be noted that other performance metrics could be used. However, we use the current data rate as the first component in the Cobb–Douglas utility function to increase the system capacity and, hence, achieve the efficiency objective

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Xi2(t) = f(αi(t), γi(t)) = 1 − γi −ln(αi(t))

γi > 1: the fairness measure, which is a function of the relative fairness that we defined to increase fairness in the system

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The parameter γi is used to control the shape of Xi2(t) and , hence, the level of fairness in the system

γi can be set to different values for different connections to allow the service provider to maintain different levels of fairness for different connections depending on the type of traffic they have, the amount of money they are expected to pay, their loyalty, etc.

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Objective function

Connection Selection

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Experiment Environment Setting

Simulation Model

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Simulation Parameters

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Test Environments

Case I: Ped A (Fig 5~12)– The mobile users in the Ped A environment move at a fi

xed speed of 3 km/h, which is the recommended value by the 3GPP

Case II: fixed differentiated channel conditions (Fig 13, 14)– The fixed channel environment is created to evaluate th

e performance of the CDPS under different fixed channel conditions (as opposed to Ped A in which the channel conditions of users vary with time, according to the models specified by the 3GPP)

2010/05/18 40OPLABFig. 5. Cell throughput. Fig. 6. Cell throughput with different values of K.

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Fig. 7. Distribution of connection average throughputs.

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Fig. 8. Distribution of connection average throughputs with different values of K.

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Fig. 9. User satisfaction with minimum throughput of 128 Kbps

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Fig. 10. User satisfaction with minimum throughput of 128 Kbps with different values of K.

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Fig. 11. User satisfaction with minimum throughput of 356 Kbps

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Fig. 12. User satisfaction with minimum throughput of 356 Kbps with different values of K.

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Fixed Differentiated Channel Conditions

Seven values are used for the SNR: −7, −4, −1, 2, 5, 8, and 11 dB

For each SNR value, there are ten connections (a total of 70 connections in the cell)

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Fig. 13. Average connection throughput for connections with different SNR values.

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Fig. 14. Percentage of packet loss for connections with different SNR values.

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Conclusions

we have proposed a CDPS scheme for future wireless cellular systems that is based on a utility function to represent the satisfactions of the mobile users as perceived by the service provider

Our scheme also utilizes an opportunity cost function to represent the satisfactions of the service provider

CDPS can simultaneously meet four design objectives, that is, efficiency, fairness, users’ satisfactions, and flexibility

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Comments

How does it work on real-time traffic or another service types? – X1

c may be delay or delay jitter.

– Objective function have to be modified.

How is the uplink data flow? What is the business model for a operator to

get maximum revenues? Strategy?

Thank you

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