1. Video scheduling algorithm
Ben-Gurion University of the Negev Department of communication system engineering
Video scheduling algorithm
in OFDMA systems
Supervisors:
Dr. Shlomo Greenberg
Mr. Pavel Babich
Oded Sonin
Tomer Lichtenfeld

2. Video scheduling algorithm in OFDMA systems
Project goal
Finding a video scheduling algorithm for OFDMA systems that will provide high network bandwidth while supporting good video quality for the users.
Video scheduling algorithm in OFDMA systems

3. Video scheduling algorithm in OFDMA systems
Orthogonal Frequency Division Multiple Access (OFDMA) is a multi-user version of the popular OFDM digital modulation scheme.
FDM
OFDM
Video scheduling algorithm in OFDMA systems

4. Video scheduling algorithm in OFDMA systems
OFDMA (cont.)
Multiple access is achieved by assigning subsets of subcarriers to individual users.
This allows simultaneous low data rate transmission from several users.
OFDMA Channels assignment example
Pilot Sub carriers
User 1 Sub carriers
User 2 Sub carriers
Frequency
Guard band
Video scheduling algorithm in OFDMA systems

5. Video scheduling algorithm in OFDMA systems
MPEG
MPEG technology uses differential frame compression.
A loss of one packet can result a loss of Group Of Pictures (GOP).
MPEG GOP Structure
Video scheduling algorithm in OFDMA systems

6. Video scheduling algorithm in OFDMA systems
The Scheduling problem
Assigning resources to users in a way that maximizes the system performance.
In our case, providing a scheduling algorithm that will maximize the network performance in terms of bandwidth and video performance.
Video scheduling algorithm in OFDMA systems

7. Video scheduling algorithm in OFDMA systems
The proposed algorithm
Priority
Allocation
Assignment
Video scheduling algorithm in OFDMA systems

8. Video scheduling algorithm in OFDMA systems
The proposed algorithm
1. Priority
The algorithm is priority based. The bit rate for each user is proportional to his priority which is determined in real time by important criteria.
Video scheduling algorithm in OFDMA systems

9. Video scheduling algorithm in OFDMA systems
The proposed algorithm
1. Priority
P(i) is packet number i in the user’s buffer.
More important video frames give the user higher priority.
More urgent video frames give the user higher priority.
Larger packets give the user higher priority.
Priority
Packet Type 8 I 5 P0 4 P1 3 P2 2 P3 1 B
For each packet in the user buffer.
Video scheduling algorithm in OFDMA systems

10. Video scheduling algorithm in OFDMA systems
The proposed algorithm
1. Priority
2. Allocation
3. Assignment
Video scheduling algorithm in OFDMA systems

11. Video scheduling algorithm in OFDMA systems
The proposed algorithm
2. Allocation
The rate for each user is calculated according to the user priority and the estimation of the total bit rate in the network.
Video scheduling algorithm in OFDMA systems

12. Video scheduling algorithm in OFDMA systems
The proposed algorithm
2. Allocation
T_B_E - Total bit rate estimation.
Estimation_Factor – a dynamic variable, updated according to each assignment and the previous assignment.
Video scheduling algorithm in OFDMA systems

13. Video scheduling algorithm in OFDMA systems
The proposed algorithm
1. Priority
2. Allocation
3. Assignment
Video scheduling algorithm in OFDMA systems

14. Video scheduling algorithm in OFDMA systems
The proposed algorithm
3. Assignment
The problem is assigning the sub-carriers to the users in a way that will maximize bandwidth while supplying each user his necessary bit rate.
We use an algorithm from graph theory called Min Cost Flow, traditionally used to minimize cost in a flow network.
We translate our problem to a minimal cost flow problem in a graph.
Video scheduling algorithm in OFDMA systems

15. Video scheduling algorithm in OFDMA systems
The proposed algorithm
3. Assignment: Min Cost Flow
The links are:
Start  users
Users  channels
Channel  Target
The nodes are:
Users
Channels
Start
Target
User 1
User 2
User N
Channel M
Channel 1
Channel 2 S T
להוסיף
קיבולות ומשקולות
Video scheduling algorithm in OFDMA systems

16. Video scheduling algorithm in OFDMA systems
The simulation
We simulate a wireless OFDMA network base station, transmitting real time encoded MPEG video streams to multiple users.
We use MATLAB code to simulate the channel conditions and packet transmission.
The proposed algorithm is used to dynamically assign the OFDMA channels to the users.
We gather statistics about the performance of the algorithm and compare them with other scheduling algorithms performances.
Video scheduling algorithm in OFDMA systems

17. Video scheduling algorithm in OFDMA systems
Results
The algorithm will be measured by two parameters:
System throughput- amount of bits transmitted successfully by the base station to the receiving terminals in the cell.
Application QOS- percentage of unusable packets received by the terminals.
Video scheduling algorithm in OFDMA systems

18. Video scheduling algorithm in OFDMA systems
Preliminary result
The increase in application QoS is caused by the new priority function.
Video scheduling algorithm in OFDMA systems

19. Video scheduling algorithm in OFDMA systems
Preliminary result
The increase in system throughput is caused by the new assignment algorithm.
Video scheduling algorithm in OFDMA systems

20. Video scheduling algorithm in OFDMA systems
Further expected research
We expect to improve the preliminary results due to improvement of the assignment algorithm and the priority function.
Video scheduling algorithm in OFDMA systems

21. Video scheduling algorithm in OFDMA systems
The end
Video scheduling algorithm in OFDMA systems