1. The document proposes a low-overhead uplink scheduling method for real-time services in WiMAX networks using load prediction to reduce scheduling overhead. It uses an Earlier Deadline First (EDF) scheduling algorithm and adaptive bandwidth scheduling scheme. 2. The method includes three modules: an information module to collect data on connection delays and bandwidth requirements, a scheduling database module to store this information, and a service assignment module to determine uplink subframe allocation. 3. Simulation results show the proposed method achieves better performance than weighted fair queuing (WFQ) and weighted round-robin (WRR) in terms of frame utilization, average throughput, average queuing delay, and packet loss

1. Wireless Embedded & Networking System Laboratory
Low-overhead Uplink Scheduling
Through Load Prediction for
WiMAX real-time services
W. Nie, H. Wang, N. Xiong2
IET Commun., 2011, Vol. 5, Iss. 8, pp. 1060–1067
Thomhert Suprapto Siadari
Dept. IT Convergence
Kumoh National Institute of Technology
February 3rd., 2012

2.  Introduction
 Problems & Solutions
 WiMAX Sample Frame
 WiMAX Service Classes
 Low-overhead Scheduling
 Simulation Results
 Conclusion & Future Works
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3.  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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4. Problems:
1. Large overhead uplink scheduling
2. Real-time services
3. Scheduling algorithm
Solutions/ Contributions:
1. Low-overhead uplink scheduling
2. Load prediction
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5.  PMP (BS to MSs)
 Transmission: Downlink & Uplink
 TDD
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6. 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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7. - Earlier Deadline First (EDF) scheduling
- Adaptive Bandwidth Scheduling
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8. - 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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9. - 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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10. 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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11. 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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12. 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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13. - 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
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14. 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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16. - Better performance than WFQ & WRR
- Sharply reduce MAP & MAC SDUs subheader overhead
- Improves system throughput
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17. - 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?
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