Low-overhead Uplink Scheduling Through Load Prediction for WiMAX real-time servicesW. Nie, H. Wang, N. Xiong2IET Commun., 2011, Vol. 5, Iss. 8, pp. 1060–1067

Thomhert Suprapto SiadariDept. IT Convergence

Kumoh National Institute of Technology

February 3rd., 2012

Wireless Embedded & Networking System Laboratory

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Outline

Introduction

Problems & Solutions

WiMAX Sample Frame

WiMAX Service Classes

Low-overhead Scheduling

Simulation Results

Conclusion & Future Works

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Introduction

IEEE802.16

WiMAX 300 trials worldwide

Connection oriented

PHY & MAC Layer

Suffers problem of huge MAC overhead

No scheduling Algorithm standard

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Problems and Solutions

Problems:

1. Large overhead uplink scheduling

2. Real-time services

3. Scheduling algorithm

Solutions/ Contributions:

4. Low-overhead uplink scheduling

5. Load prediction

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WiMAX Sample Frame

PMP (BS to MSs)

Transmission: Downlink & Uplink

TDD

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WiMAX Service Classes

WiMAX service classes:

Unsolicited Grant Service (UGS) fixed-size data packets

Real-time polling service (rtPS) generate variable-size data packets periodically

Non-real-time polling service (nrtPS) bandwidth not on the basis of fixed packet size

Best Effort (BE) efficient service (web surfing)

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Low-Overhead Uplink Scheduling

- Earlier Deadline First (EDF) scheduling

- Adaptive Bandwidth Scheduling

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EDF Scheduling

- Information Module

- Scheduling Database Module

- Service Assignment Module

f : frame size (ms), uplink and downlink subframe contains;

di : the maximum delay of connection i (ms);

qi(t) : the queue length of connection i at time t(bit);

si [t, t + f ]: the number of bits required to be transmitted for connection i in the time interval [t, t + f ];

ai[t, t + f ]: the number of bits arriving for connection i in the time interval [t, t + f ];

Ndi[t, t + f ]: the number of bits waiting in the queue for connection i, which will expire in the time interval [t, t + f ].

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EDF Scheduling

- Selects SSs based on delay requirement

- Suitable for real-time services

- Deadline to each packet

- Allocate bandwidth to SS based on earliest deadline

Information Module Firstly delay requirement

rtPS connection input information module:

Output:

Secondly expiration time

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EDF Scheduling

Scheduling Database Module serves as a database of information for all connections

Service Assignment Module

- Determine uplink subframe allocation in terms of the number of bits per SS

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EDF Scheduling

Specific implementation steps:

Check BWrtps & Bufferi_deadline (bandwidth required by the deadline frame in cureent time

If

Guarantee the bandwidth of deadline packets

Allocate more bandwidth to active SS

If

The bandwidth requirement will be scheduled:

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Low Overhead Algorithm

C: the uplink channel capacity;

F: set of all SSs belonging to the rtPS class;

Bi: bandwidth allocated to connection i;

Dequeue i: remove packet P from the queue of connection i;

amount(P,): retrieve the packets P from the connection i. Convert the packets to number of symbols according to the signal-to-interference noise ratio [SINR(ji)] of connection i.

CreateIE(amount(P, ji)): create an IE for connection i with

amount(P, ji) number of symbols. Then, IE is added to the UL-MAP message.

Drop(rtPS): drop packets from the queues for all connections.

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Adaptive Scheduling Scheme

- Modeling the Arrival Process

PDF:

CDF of inter-arrival time:

- Estimation of Time: predict the response time when BS allocates the bandwidth to SS

- Tr = Reuest time

- Ti = Bandwidth response time

- Estimation of Time

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Adaptive Scheduling Scheme

Adaptive time slots calculating:

To calculate expected bandwidth:

To calculate required time slots

Given buffer calculate required time slot

Si(0,1) smooth parameter give ratio of the actual allocation bandwidth to previous predictions and requirements

If ε > 1 calculated bandwidth is closer to predicted bandwidth

If ε < 1 calculated bandwidth is closer to requested bandwidth

So, use ω = 0.05 to adjust Si.

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Simulation Results

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Conclusion & Future Work

- Better performance than WFQ & WRR

- Sharply reduce MAP & MAC SDUs subheader overhead

- Improves system throughput

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Yang harus dijawab setelah baca paper

- Problem yg ada itu apa?

- Solusi dan kontribusi yang ditwarkan apa?

- Metodenya? LOH: EDF & Adaptive sched schem?

- EDF utk apa sebenarmya? Ad a 3 module disini? Information module? Sched database module? Service assignment module? Specific implementation steps?

- Adaptive sched scheme: modeling Arrival process? estimation time? Adaptive time slots calculating? apa tujuannya semua ini?

- Simulasi frame ultilisation, average throughput, average queuing delay, packet loss? kenapa dalam real-time communication harus pake ini? Alasannya?

- Dia pake perbandingan WFQ dan WRR? kenapa? Dan hasilnya lebih baik? Kenapa? Ada apa dengann WFQ dan WRR?

- Dia kan pake load prediction? Kalo WFQ dan WRR pake load prediction juga gimana?