Post on 20-Dec-2021
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Dynamic Resource Allocation for EfficientWireless Packet Data Communcations
B. Srikrishna
Assistant ProfessorDepartment of Electrical EngineeringIndian Institute of Technology Madras
Joint work with:M. Chandrashekar
V. SandeepParimal Parag
March 17, 2006
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Broadband Wireless
Internet
Wireless Local Area Network (WLAN)
Wireless Cellular
I Demand for mobile wireless internet access
I Need support for multimedia data transfer
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Broadband Wireless: Challenges
t
t
I High data rates and limited/expensive spectrum⇒ need high spectral efficiency
I Shared resources and multiple access
I Multipath fading channel
I Bursty traffic characteristics
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Broadband Wireless: Some Proposals
I Code-Division Multiple Access (CDMA)-basedI 1xEV-DO (HDR)I HSDPAI 1xEV-DV
I Orthogonal Frequency Division Multiplexing(OFDM)-based:
I FlashOFDMI IEEE 802.16eI IEEE 802.20
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Key Techniques
User 1 User 2 User 3
Periodic
reallocation of
resources
I Adaptation to channel and traffic conditionsI Dynamic resource allocation
I Reallocation period of the order of a few milliseconds
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Downlink Resource Allocation Problem
Channel information
User 1
User 2
User K
TrafficBasestation
I Physical resources: power and bandwidth
I Maximize system throughput
I Total transmit power constraint
I Fairness or Quality of Service (QoS) constraints
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Maximizing Capacity
User 1
User 2
User K
Basestation
Select theuser with
best channel
Channel K
Channel 2
Channel 1
I All power and bandwidth resources to one user
I User with best achievable rate chosen:
i = arg maxk
Rk ,
where Rk is the rate that can be supported by user k.
I No fairness or QoS constraint
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Maximizing Capacity: Parallel Channels
User 1
User 2
User K
Basestation
For each
best channeluser with
Select the
parallelchannel
Parallel Channels to each user
I Bandwidth resources split to achieve parallel channelsI For each channel n, user with best channel conditions
chosen:in = arg max
kRk,n.
I Water-filling power allocationI No fairness or QoS constraint
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Fairness and Quality of Service (QoS)
I Various notions of fairness or QoS
I Round-Robin
I Proportional Fairness [Tse02]
i = arg maxk
Rk
Rk,av,
where Rk,av is the average rate that can be supportedby user k.
I Modified-Largest Weighted Delay First (M-LWDF)[Andrews00]
i = arg maxk
γkWkRk ,
where Wk is the Head-Of-Line (HOL) packet delay foruser k, and γk = Ck
Rk,av.
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Resource Allocation in OFDM
Power
User 1
User 2
User 3Subc
arri
ers
I Available resources:I SubcarriersI Transmit power
I Channel is frequency-selective ⇒ subcarriers notidentical.
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
OFDM Resource Allocation Algorithms
I Channel Aware Only (CAO) SchedulingI Proportionally Fair (PF) subcarrier allocation [Rhee00]I PF subcarrier allocation + power optimization [Shen05]I Max utility subcarrier allocation + power optimization
[Song05]
I Channel Aware Queue Aware (CAQA) SchedulingI MLWDF for OFDM-TDMA [Andrews00]I MLWDF at subcarrier level [Parag05]
I Our WorkI Joint Subcarrier and Power Allocation (JSPA) approachI Optimize power allocation after each subcarrier is
allocated
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
MLWDF for OFDM-TDMA
I All subcarriers allocated to a single user in each slotI Select user i as:
I i = arg maxk
γkWkRk
I Wk : Head-Of-Line (HOL) packet delay for user kI Rk : Rate achievable for user k (water-filling)
I γk =Ck
Rk,av
I Ck = − log δk
Dkto achieve P[delay > Dk ] < δk
I Throughput optimal single-user scheduling ruleI Maximum stability: achieves stable queues if any
algorithm can achieve it
I Single-user scheduling in each time slot not optimal
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Subcarrier-wise Allocation
I Approach 1: MLWDF at the subcarrier level [Parag05]
I For each subcarrier n:I in = arg max
kγkWkRk,n
I Wk : Head-Of-Line (HOL) packet delay for user kI Rk,n: Rate achievable for user k on subcarrier nI Power allocation needed to allocate subcarriersI Uniform/fixed power allocation assumption
I Approach 2: [Song04]I Mean packet waiting time instead of Head-Of-Line
(HOL) packet delayI Other utility functions based on mean packet waiting
time
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Joint Subcarrier and Power Allocation
power
Split power equally amongst subcarriers
Start
Checkif all subcarriers
are allocated
Allocate a subcarrier to a user
Start
Split power equally amongst subcarriers
Allocate all subcarriers to users
Update each user’squeue
No
Yes
End
Optimize powerallocation with
Update each user’squeue
End
Optimize power
allocation with
power
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Joint Subcarrier and Power Allocation (JSPA)
I Optimal JSPA too complexI Sub-optimal JSPA
I Power optimization after each subcarrier is allocatedleads to better allocation of the remaining suncarriers
I Power allocation to each user proportional to thenumber of subcarriers allocated
I HOL delay is estimated after each subcarrier is allocated
I Some practical constraints includedI Discrete-rate constraint: Integer bit M-QAM
constellationsI Extension to band-wise allocation: reduced
signaling/feedback
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Simulation Setup
I 128 subcarrier OFDM system
I 12 users, Bernoulli packet arrival, 100 slot buffer
I 6-tap multipath channel, average channel conditions aredifferent for each user
I QPSK to 64-QAM
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Results: Throughput vs. Arrival Rate
1 1.5 2 2.5 3 3.5 4 4.5 5 5.51
2
3
4
5
6
7
Arrival rate (Mbps)
Thro
ughp
ut (M
bps)
CAO+FPACAO+FPA+PAOCAO+JSPAMLWDFCAQA+FPACAQA+JSPAPtotal= 5 dBW
Homogenous rate users
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Results: Max. Arrival Rate vs. Transmit Power
4 4.5 5 5.5 6 6.5 7 7.5 82.5
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
Ptotal in dBW
Arriv
al ra
te (M
bps)
CAO+FPACAO+FPA+PAOCAO+JSPAMLWDFCAQA+FPACAQA+JSPAHomogenous rate users
I Max. arrival rate for less than 0.5% packets dropped
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Results: Delay Performance
5 10 15 20 25 30 35 40
10−1
100
101
delay (time slots)
P(de
lay>
x)CAO+FPACAO+FPA+PAOCAO+JSPAMLWDFCAQA+FPACAQA+JSPA
Ptotal = 8dBW Arrival rate = 3 MbpsHomogenous rate users
I Best and worst delay performance among users plotted
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Results: Band-wise Allocation
1 1.5 2 2.5 3 3.53
3.5
4
4.5
5
5.5
6
Delay spread (rms) µsec
Arriv
al ra
te (M
bps)
L = 1L = 2L = 4L = 8L = 16Ptotal = 5dBW
I L = Number of subcarriers in a sub-band
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Resource Allocation in CDMA
User 1
Power
code
sSp
read
ing
User 2
I Available resources:I Spreading codesI Transmit power
I For any given user, all spreading codes are similar (interms of channel conditions).
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Multiuser Scheduling
I Most algorithms are single-user scheduling algorithmsI Proportionally Fair [Tse02]I MLWDF [Andrews00]
I Recent results on multi-user scheduling algorithmsI Greedy and pairwise greedy allocation [Kumaran05]I Gradient-based scheduling [Agrawal04]
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Results: Maximum Supportable Traffic
0 1 2 3 4 5 6 7 8 90
0.1
0.2
0.3
0.4
Average Arrival Rate (Mbps)
Frac
tion
of p
acke
ts d
ropp
ed
MLWDFTWO USER
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Results: Delay Performance
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
10−2
10−1
100
Delay d (in sec)
Prob
[del
ay >
d]
MLWDFTWO−USER
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
Summary
I Dynamic resource allocation is essential to achieve highspectral efficiency
I Adaptation based on both channel and trafficinformation
I Some new results for OFDM and CDMA systemsI Joint subcarrier and power allocation in OFDMI Multiuser scheduling in CDMA
I Several open problems:I OptimalityI Quantifying the signaling/feedback overhead
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
References
E. F. Chaponniere, P. Black, J. M. Holtzman, andD. Tse, “Transmitter directed multiple receiver systemusing path diversity to equitably maximize throughput,”U. S. Patent No. 6449490, September 2002.
M. Andrews, K. Kumaran, K. Ramanan, A. Stolyar,R. Vijayakumar, and P. Whiting, “CDMA data QoSscheduling on the forward link with variable channelconditions,” Bell Labs Technical Memorandum, 2000.
W. Rhee and J. M. Cioffi, “Increase in capacity ofmultiuser OFDM system using dynamic subchannelallocation,” in Proceedings of the 51st IEEE VehicularTechnology Conference, vol. 2, Spring 2000, pp.1085–1089.
Z. Shen, J. G. Andrews, and B. L. Evans, “Adaptiveresource allocation in multiuser OFDM systems withproportional rate constraints,” IEEE Transactions onWireless Communications, vol. 4, no. 6, pp. 2726–2737,November 2005.
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
References
G. Song and Y. Li, “Cross-layer optimization for OFDMwireless networks-Part II: Algorithm development,” IEEETransactions on Wireless Communications, vol. 4, no. 2,pp. 625–634, March 2005.
P. Parag, S. Bhashyam, and R. Aravind, “A subcarrierallocation algorithm for OFDMA using buffer andchannel state information,” in Proceedings of the 62nd
IEEE Vehicular Technology Conference, vol. 1,September 2005, pp. 622–625.
G. Song, Y. G. Li, J. L. J. Cimini, and H. Zheng, “Jointchannel-aware and queue-aware data scheduling inmultiple shared wireless channels,” in Proceedings of theIEEE Wireless Communications and NetworkingConference, vol. 3, March 2004, pp. 1939–1944.
Dynamic ResourceAllocation for
Efficient WirelessPacket Data
Communcations
B. Srikrishna
Introduction
Problem
OFDM ResourceAllocation
Our Algorithm
Results
CDMA ResourceAllocation
Results
Summary
References
References
R. Agrawal, V. Subramanian, and R. Berry, “Jointscheduling and resource allocation in CDMA systems,”in 2nd Workshop on Modeling and Optimization inMobile, Ad Hoc, and Wireless Networks (WiOpt ’04),Cambridge, UK, March 2004.
K. Kumaran and H. Viswanathan, “Joint power andbandwidth allocation in downlink transmission,” IEEETransactions on Wireless Communications, vol. 4, no. 3,pp. 1008–1016, May 2005.