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Throughput-Guaranteed Resource-Allocation Algorithms for Relay-Aided Cellular OFDMA System. 1 Megumi Kaneko, 2 Petar Popovski, and 1 Kazunori Hayashi 1 Graduate School of Informatics, Department of Systems Science, Kyoto University ( 京都大學 ) , Japan - PowerPoint PPT Presentation
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Throughput-Guaranteed Resource-Allocation
Algorithms for Relay-Aided Cellular OFDMA System
1Megumi Kaneko, 2Petar Popovski, and 1Kazunori Hayashi
1 Graduate School of Informatics, Department of Systems Science, Kyoto University (京都大學 ), Japan2 Department of Electronic Systems, Aalborg University (奧爾堡大學 ), Denmark
< IEEE Transactions on Vehicular Technology, vol. 58, no. 4, MAY 2009 >
Outline
• Introduction
• System model
• Goal
• Proposed Resource-Allocation Algorithms– Single-Relay Case: FTD and ATD
– Multiple-Relay Case: MRPA and MRAA
• Performance
• Conclusion
Introduction
• Installing relay stations in strategic positions in a cell– higher data rates can be provided in remote or shadowed areas
of the cell
– low-cost devices that can easily be deployed
BS
RS
MS
Direct link
Relayed link
Relayed link
Introduction
• This paper investigates the problem of resource allocation for a relay-aided cellular system based on OFDMA.
• This paper focuses on the downlink (DL) transmission from a BS to mobile stations (MSs) or RS in a single cell.
BS-Subframe (TBS)
BS–MSor
BS–RS
RS-Subframe (TRS)
RS–MS
TF
Time
Freq.
System model
• Relay station– stores the received packets
– decodes the received packets
– re-modulates the received packets
• Assume that packets sent to the RS in a frame cannot immediately be forwarded due to hardware limitations– The data for relayed users takes two frames to be delivered.
– The data for direct users takes one frame.
System model
• MSs feed back to the BS their CSI on every subchannel.– CSI = Channel-State Information
• Assumption that BS knows the achievable rate rk,n
– for each user k on subchannel n
• Path Selection– A user is linked to the RS only if rk
RS-MS 2 rkBS-MS ;
– Otherwise, it is linked to the BS.
Goal
• The BS-subframe is shared between the – direct users and BS-RS links
– If the BS forwarded all the packets for the relayed users as they arrive in the BS queue, there will be less resource that is available for the direct users.
BS-Subframe (TBS)
BS–MSAND
BS–RS
RS-Subframe (TRS)
RS–MSTime
Freq. relayed users
direct users
Goal
• The target of this work is to design an algorithms with good throughput and outage performance.– Single-Relay Case
– Multiple-Relay Case
RSBS
MS1
MS2
r1 > r2Outage !
r1
r2
Proposed Resource-Allocation Algorithms
• RS makes its own initial allocation to minimize the outage.
• BS optimizes the final allocation to improve the overall throughput.
– Single-Relay Case: FTD and ATD
– Multiple-Relay Case: MRPA and MRAA
BS-Subframe (TBS)
BS–MSor
BS–RS
RS-Subframe (TRS)
RS–MS
TF/2 TF/2
Single-Relay Case: FTDFixed Time-Division Algorithm
• RS makes its own initial allocation to minimize the outage.– rk,n : achievable rate on subchannel n for user k
– βk (t–1) : previous average rate for user k
– R : the minimum data rate requirement for user k
BS-Subframe (TBS)
BS–MSor
BS–RS
RS-Subframe (TRS)
RS–MS
TF/2 TF/2
3181.1
350350
300330)1(
,,
Rt
nknk
k
r
Average rates are higher than their required rates
42283.0
350350
300250)1(
,,
Rt
nknk
k
r
Single-Relay Case: FTDFixed Time-Division Algorithm
• RS makes its own initial allocation to minimize the outage.– rk,n : achievable rate on subchannel n for user k
– βk (t–1) : previous average rate for user k
– R : the minimum data rate requirement for user k
BS-Subframe (TBS)
BS–MSor
BS–RS
RS-Subframe (TRS)
RS–MS
TF/2 TF/2
Average rates are lower than their required rates
Single-Relay Case: FTDFixed Time-Division Algorithm
• If user k has the higher φ and its packets are queued at the RS, the user k is serviced first by RS.
• If user k has the higher φ than the allocated one but its packets are not queued at the RS, RS sends a Request Message to the BS.– User k set UReq
– φmax : The maximum value of φ for user in UReq
BS-Subframe (TBS)
BS–MSor
BS–RS
RS-Subframe (TRS)
RS–MS
TF/2 TF/2
Single-Relay Case: FTDFixed Time-Division Algorithm
BS
RS
MS1 MS2 MS3 MS4
DL Queue: MS1, MS2
φ1= 500 φ2= 600 φ3= 900 φ4= 400
DL Queue: MS3, MS7
φmax
φmin
φ3…
UReq
Single-Relay Case: FTDFixed Time-Division Algorithm
• BS optimizes the final allocation to improve the overall throughput.– BS calculates the number of sub-channels nBR that are required t
o send all the packets that are queued at the BS of the users in UReq.
– The φ metric of the direct user is compared with φmax, and the sub-channel n is allocated to the link with the highest value.
RS-Subframe (TRS)
RS–MS
TF/2 TF/2
BS-Subframe (TBS)
BS–MSor
BS–RS
φ
φmax
direct user
RS
BS
(950)
(400)
UReq (φmax)
Single-Relay Case: FTDFixed Time-Division Algorithm
• Channel utilization:
Number of allocated time slots for user k
Number of allocated packets for user kBM / RM
BS-Subframe (TBS)
BS–MS (BM)or
BS–RS
RS-Subframe (TRS)
RS–MS (RM)
TF
Single-Relay Case: FTDFixed Time-Division Algorithm
• Throughput:
Number of allocated time slots for user k
1 or 0
Single-Relay Case: ATDAdaptive Time-Division Algorithm
• Starting from the allocation by the FTD algorithm for TBS = TRS = TF /2, time division can be adapted to increase the overall throughput.
BS-Subframe (TBS)
BS–MSor
BS–RS
RS-Subframe (TRS)
RS–MS
TF/2 TF/2
Multiple-Relay Case: MRPAMultiple-RS Parallel with Activation Algorithm
• Path Selection (user k is on direct or relayed link)– User id linked to the RS only if ;
otherwise, it is linked to the BS. Due to• The data for relayed users takes at least two frames to be delivered.
• The data for direct users takes only one frame.
Direct link
Relayed link
BS-Subframe (TBS)
BS–MSor
BS–RS
RS-Subframe (TRS)
RS–MS
TF/2 TF/2
BS
RS
MS
Direct link
Relayed link
Multiple-Relay Case: MRPAMultiple-RS Parallel with Activation Algorithm
• If the number I of relays is an even number, there are I/2 relay pairs by regrouping the diametrically opposed relays.– Frequency reuse because of minimized interference.
• FTD-based resource allocation.
BS
RS1
RS6
RS5
RS4
RS3
RS2
Direct link
Relayed link
Multiple-Relay Case: MRPAMultiple-RS Parallel with Activation Algorithm
• If the number I of relays is an even number, there are I/2 relay pairs by regrouping the diametrically opposed relays.– Frequency reuse because of minimized interference.
• FTD-based resource allocation.
BS
RS1
RS6
RS5
RS4
RS3
RS2
Direct link
Relayed link
Multiple-Relay Case: MRAAMultiple-RS Adaptive Activation Algorithm
• Without assuming frequency reuse.
• RSj with the worst throughput is removed, and the RSj-subframe is reallocated to the BS-subframe.
– For higher throughput performance
– ATD-like resource allocation
BS
RS6
RS4
RS3
RS2
Performance– 實驗參數
• BS Cell : 1000m radius
• Relay placed in 800m away from BS
• BS/RS Power: 20/5 W
• Subchannels : 12
• Frame duration : 12 ms
• Packet arrive at BS : Poisson process
Performance – Single-Relay Case
Upper Bound
All Fwd: Relays selected in random w/o UReq
PFS: Proportional Fair Scheduling w/o considering R and w/o Relays
Upper / Lower Bound
Packets from BS through RS to MS is in the same frame
Performance – Single-Relay Case
Lower Bound
All Fwd: Relays selected in random w/o UReq
PFS: Proportional Fair Scheduling w/o considering R and w/o Relays
Upper Bound (throughput)
Performance – Multiple-Relay Case
Upper Bound
PFS: Proportional Fair Scheduling w/o considering R and w/o Relays
Performance – Multiple-Relay Case
Lower Bound
PFS: Proportional Fair Scheduling w/o considering R and w/o Relays
Conclusion
• This paper investigated the problem of resource allocation for a relay-aided cellular system based on OFDMA.
• Design FTD, ATD, MRPA and MRAA algorithms for good throughput and outage performance.
The End
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