qos guaranteed scheduling and resource allocation algorithm for ieee 802 16 ofdma system
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QoS-Guaranteed Scheduling and Resource Allocation Algorithm for IEEE 802.16 OFDMA System. ICC 2008. ICC 2008. Xinning Zhu 1 , Jiachuan Huo 2 , Xiaoxi Xu 2 , Chunxiu Xu 2 , Wei Ding 1 School of Continuing Education 1 , School of Telecommunication Engineering 2

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qos guaranteed scheduling and resource allocation algorithm for ieee 802 16 ofdma system

QoS-Guaranteed Scheduling and Resource Allocation Algorithm for IEEE 802.16 OFDMA System

ICC 2008

ICC 2008

Xinning Zhu1, Jiachuan Huo2, Xiaoxi Xu2, Chunxiu Xu2, Wei Ding1

School of Continuing Education1, School of Telecommunication Engineering2

Beijing University of Posts and Telecommunications

outline
Outline
  • Introduction
  • System Module
  • Proposed Scheduling and Resource Allocation Algorithm
  • Simulation Results
  • Conclusions
introduction
Introduction
  • Five classes of scheduling services are defined in IEEE 802.16:
    • Unsolicited Grant Service (UGS)
    • Real-Time Polling Service (rtPS)
    • Extended rtPS (ertPS)
    • Non-Real-Time Polling Service (nrtPS)
    • Best Effort (BE)
introduction1
Introduction
  • Efficient methods for QoS support in
    • IEEE 802.16 system
    • Deploying Wireless-OFDMA physical layer
  • In the OFDMA system, resources are scheduled in
    • Frequency
    • Time
    • Power domains
introduction2
Introduction
  • A user scheduling priority function for each active user and update it dynamically depending on each
    • User’s subchannel quality
    • Quality deviation on subchannels
    • Its connection’s QoS satisfaction
system module

FFT sizes

2048

1024

512

128

Total number of data subcarriers(Ndata)

1536

768

384

96

System Module
  • Adaptive Modulation and Coding (AMC)

Single BS

BS

SS1

SS2

SSN

N SS

system module1
System Module
  • Nine adjacent subcarriers form a bin which includes
    • 8 data subcarriers
    • 1 pilot subcarrier
  • An AMC slot is defined as
    • Nbinbins by Msymsymbols
      • Where Nbin × Msym= 6
  • A basic allocation unit consists of
    • 48 data subcarriers
system module2
System Module
  • Whole bandwidth can be divided into
    • K = Ndata/Nbinsubchannels
  • A downlink subframe consists of
    • subsequent M OFDMA symbols
      • Where M is a multiple of Msym
system module3
System Module
  • Focus on the downlink scheduling problem
  • Assume that BS has knowledge of
    • All subchannels of all users in the system
    • Wireless channel is constant over an entire downlink OFDMA subframe
  • Do NOT consider UGS and ertPS
    • UGS and ertPS connections are given the highest priority and allocated fixed slots first
proposed scheduling and resource allocation algorithm

Subchannel k

Priority

User i

ProposedScheduling and Resource Allocation Algorithm
  • A. Determination of Scheduling Priority

Cidenotes the QoS satisfaction indicator of user i

Sikis a variable reflecting current channel state

proposed scheduling and resource allocation algorithm1

Quantifies the normalized channel quality

ProposedScheduling and Resource Allocation Algorithm
  • A. Determination of Scheduling Priority

bikdenotes the information bits that can be carried

(as indicated in Table I)

bimaxdenotes the maximum number of bits of user i on all subchannels

bmaxeachsubcarrier can be loaded to at most bits per symbol when the most efficient AMC mode is selected

proposed scheduling and resource allocation algorithm2
ProposedScheduling and Resource Allocation Algorithm

bikdenotes the information bits that can be carried

bimaxdenotes the maximum number of bits of user i on all subchannels

proposed scheduling and resource allocation algorithm3
ProposedScheduling and Resource Allocation Algorithm
  • Maximum connection priority of user

Cijdenotes the QoS priority of connection j, which belongs to user i

proposed scheduling and resource allocation algorithm5
ProposedScheduling and Resource Allocation Algorithm
  • For rtPS connection j of user i, the QoS priority Cijis defined as

βrtPS∈[0, 1] is the rtPS-class coefficient as defined in [4]

Wijdenotes the longest packet waiting time of the connection j of user i

Tijis the maximum latency which is negotiated when the connection j is established

Tframe is the frame duration

proposed scheduling and resource allocation algorithm7
ProposedScheduling and Resource Allocation Algorithm
  • For nrtPS connection j of user i, the QoS priority is defined as

Qijdenotes the current number of bytes in the queue of connection j of user i

ϕijis the queue thresholds set to obtain the fill level indicator of the queue using the ratio Qij /ϕij

proposed scheduling and resource allocation algorithm8
ProposedScheduling and Resource Allocation Algorithm
  • B. Resource Allocation
    • Define the normalized channel quality deviation of subchannel k as follows

bkmaxis the maximum number of bits that can be carried by one subcarrier in one OFDMA symbol on subchannel

proposed scheduling and resource allocation algorithm10
ProposedScheduling and Resource Allocation Algorithm
  • The number of information bits should be sent can be expressed as
    • during the frame m + 1 for connection j of user i
proposed scheduling and resource allocation algorithm11
ProposedScheduling and Resource Allocation Algorithm
  • The number of information bits allocated to rtPS connection j of user i is given by
  • The number of OFDMA symbols needed to carry Δij(m+ 1) information bits on subchannel k equals to

Δ’ij(m+1) denotes the total bits of packets from the head of line to the finding packet

^

simulation results
Simulation Results
  • A time-varying and frequency-selective channel model, ITUPedestrian A multi-path model, is used
simulation results1
Simulation Results
  • A. Case 1: Multiple users with multiple rtPS connections each

Set the data buffer large enough that any packet drop will occur only when it fails to meet the latency requirement

simulation results3
Simulation Results
  • B. Case 2: Multiple users with multiple nrtPSconnectionseach
simulation results6
Simulation Results
  • B. Case 3: Multiple users with one rtPS, one nrtPS and oneBE connection each
conclusions
Conclusions
  • This paper developed an efficient scheduling and resource allocation algorithm
    • for multiple connections with diverse QoS requirements
    • which can be used in IEEE 802.16 OFDMA system
  • This paper scheduled
    • the user with the highest priority first
      • allocated the resource to the connection with the highest QoS priority
slide32

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