A novel radio resource management approach for QoS Provisioning in multi-service

Multi-slot OFDMA Systems

Ahmed N. Zaki and Abraham O. Fapojuwo

Dept. of Electrical and Computer Engineering

The University of Calgary, Calgary, AB, Canada

WCNC 2008

Outline

• Introduction

• System model

• Optimal scheduling

• Suboptimal scheduling

• Simulation

• Conclusion

introduction

• In this paper, we consider the Radio Resource Management (RRM) in the downlink on OFDMA system

• RRM is the Problem of distributing– different resources

• Multi-user

introduction

• The general approach taken by all the past papers – Formulate the RRM problem– It can be optimally solved from the mathematic

al programming theory

• In the rest of thist paper will propose a suboptimal algorithm

introduction

• Assumptions– To allocate enough resource to each user– Each user will be satisfy a constant data rate– RT services are allocated a constant number of

bits every frame– Thus, each NRT services will depend on many

parameters

introduction

• Assumptions– Due to frequency selective fading, each user

may have a different SNR for the different subcarriers

– BS invokes the scheduling once during each frame

System model

• The total available bandwidth divided into K subchannels

• A frame length of W seconds• there are T available time slots per subchan

nel in the current frame• There are M different modulation/conding• There are N users that will be allocate resou

rce

System model

• let β denote the number of bits that can be transmitted in one time slot on any subchannel

• A logical subchannel is a physical subchannel that can only be used with one modulation/coding combination– Hence, the total number of logical subchannels G = K M.

– The number of data units transmitted on a logical subchannel ( Sg )

System model

• Xg,n equals the number of time slots allocated to the nth user on the gth logical subchannel

Optimal scheduling

Suboptimal scheduling_baseidea

• Network flow

SD1

a

b

cD2

82

3

4

5

8

67

Suboptimal scheduling_baseidea

• Network flow

SD1

a

b

cD2

82

3

4

5

8

67

Suboptimal scheduling_baseidea

• Network flow

SD1

a

b

cD2

82

3

4

5

8

67

2

3

33

2

30

5

3

Suboptimal scheduling_example

1

2

3

16

64

16

64

16

64

a

b

c

Subchannel usermodulation

10 slot

10 slot

10 slot

80 byte

120 byte

-5

-10

-5

-10

-10

-5-5

-530 byte

8 slot

12 slot

3 slot

2 slot

7 slot

0 slot

0 slot

Simulation

• The simulated system consists of a single cell

• The channel consists of 4 subchannels

• The available modulation schemes are QPSK, 16-QAM and 64-QAM

• The frame length is 10 msec

• Each subchannel has 7 time slots

Simulation

Simulation

Conclusion

• This paper proposed a novel approach for OFDMA radio resource management

• Simulations show that the proposed approach enhances the system performance