Incentive-Oriented Downlink Scheduling for Wireless Networks with Real-Time and Non-Real-Time Flows...
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Transcript of Incentive-Oriented Downlink Scheduling for Wireless Networks with Real-Time and Non-Real-Time Flows...
Incentive-Oriented Downlink Scheduling forWireless Networks with Real-Time and
Non-Real-Time Flows
I-Hong Hou, Jing Zhu, and Rath Vannithamby
Motivation
• Wireless networks are increasingly used to serve real-time flows– VoIP, video streaming, online gaming
• In addition to throughput, these flows require strict per-packet delay guarantees
• Most current mechanisms belong to the paradigm of DiffServ
DiffServ
• Serve different flows differently• Usually, real-time flows get higher priorities
than non-real-time ones• Can be unfair to non-real-time flows• Non-real-time flows may lie about its category
to gain more service• Solution: charge real-time flows more
I am a real-time flow. I need small delay
You need to pay more
I require small throughput. Can I sacrifice throughput
for delay?
Goal of the paper
Design a scheduling policy that allows flows to tradeoff between high throughput and low delay by themselves
Desired Properties
• Incentive-compatibility: Flows optimize their own performance by reporting true category
• Versatility: The policy can work with various protocols in other layers– Different traffic patterns, different MAC, etc.
• Deadline awareness: The policy respects the deadlines of real-time flows
• Work conservation
Incentives of clients
• Non-real-time clients: Aim to maximize throughputs
• Real-time clients: Aim to maximize timely-throughput
• Timely-throughput: throughput of packets with delay < D
Basic Idea of Design
• Assume each client n has a weight of wn• Each client n is entitled to have wn/Σwn
channel time• Allocating channel time proportional to wn
maximizes and achieves proportional fairness• Deficit of client n: (The amount of channel
time that it is entitled) – (actual channel time)
Joint Deficit-Deadline (JDD) Policy
• A thin layer between Network layer and MAC layer
• Provides two functions: enqueue and dequeue– Interface defined by ns-2
• enqueue: a packet is labeled with deadline and put in the queue when it arrives from Network layer
• dequeue: forward a packet to MAC
Architecture of JDD
Enqueue
• When a packet arrives from Network layer• Mark the deadline of the packet
– Deadline of real-time flow = current time + D– Deadline of non-real-time flow = current time + a
large value (~ TCP timeout)
• Place the packet in the queue
Dequeue
• Delete all expired packets• Forward the packet with the earliest deadline
with the constraint that the corresponding client has positive deficit
• Earliest deadline: real-time packets usually got served first, and non-real-time packets need to wait
• Positive deficit: real-time packets receive smaller channel time
Ns-2 Simulation
• 10 clients, 5 of them are real-time ones, and the other 5 are non-real-time ones
• Real-time flows require a delay bound of 100ms
• All flows are generated by TCP• Use IEEE802.11 for the MAC• Weight of non-real-time clients = 1• Weight of real-time clients varies
Simulation Results
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90
0.51
1.52
2.53
3.54
Throughput of non-real-time
Timely-throughput of non-real-time
Timely-throughput of real-time
Weight of real-time client
Pe
rfo
rma
nc
e (
Mb
ps
)
Delay Distributions
0 0.1 0.2 0.3 0.4 0.5 0.60
0.2
0.4
0.6
0.8
1
1.2
Non-real-time
Delay (sec)
CD
F
Performance Comparison
• Compare against two other policies:– Earliest deadline first (EDF)– Weighted round robin (WRR)
• 10 clients, 5 real-time and 5 non-real-time• The distance between clients and the base
station is evenly distributed• Performance metric: • = throughput/timely-throughput
Simulation results for TCP
JDD WRR EDF0
500
1000
1500
2000
2500non-real-timereal-time
Pe
rfo
rma
nc
e (
kb
ps
)
JDD WRR EDF02468
101214161820
To
tal
we
igh
ted
lo
g
thro
ug
hp
ut
Simulation results for TFRC
JDD WRR EDF02468
101214161820
To
tal
we
igh
ted
lo
g
thro
ug
hp
ut
JDD WRR EDF0
500
1000
1500
2000
2500
3000
3500
non-real-time
real-time
Pe
rfo
rma
nc
e (
kb
ps
)
Simulation results for Interfering Network
• Add an additional link that causes interference
JDD WRR EDF02468
1012141618
To
tal
we
igh
ted
lo
g
thro
ug
hp
ut
JDD WRR EDF0
200400600800
10001200140016001800 non-real-time
real-time
Pe
rfo
rma
nc
e (
kb
ps
)
Conclusion
• We propose the JDD scheduling policy• The policy allows strategic clients to choose
between high throughput and low delay• The policy does not make any assumptions
on other layers, and can work with a wide range of different systems
• Simulation results show that JDD outperforms other policies