Transcript Multimedia Communications QoS Support for Multimedia in IEEE 802.16 Networks Simulation Results Aadil Zia Khan Department of Computer Science Lahore University of Management Sciences Email: [email protected].

Multimedia
Communications
QoS Support for Multimedia in IEEE 802.16 Networks
Simulation Results
Aadil Zia Khan
Department of Computer Science
Lahore University of Management Sciences
Email: [email protected]
IEEE 802.16 Networks
(Introduction)

One of the most promising solutions for wireless broadband access

IEEE Project 802 working group 16 working towards building its standards

Commercial forum Worldwide Interoperability for Microwave Access (WiMAX) was
founded which includes more than 300 member companies

WiMAX will provide the last mile internet access to residential users

Especially useful in regions where wire lined infrastructure does not exist or can not be
setup

WiMAX will create an economical alternative to expensive leased line solutions for small
and medium enterprises
IEEE 802.16 Networks
(Benefits)




High Speed Access
Wireless
Broad Coverage
Mobility
IEEE 802.16 Networks
(Operation & Architecture)
Nodes


Tower / Base Station
Receiver / Subscriber Station
Network Architecture




Point-to-Mulitpoint
All the Subscriber Stations
communicate only through the
Base Station
Mesh
All the Subscriber Stations can
communicate through the Base
Station as well as directly with
other Subscriber Stations
IEEE 802.16 Networks
(Phy. Layer Communication)
Frequency Division Duplexing


The uplink and downlink
channels are on different
frequencies
Both the Half-Duplex and
Full-Duplex modes are
supported
Time Division Duplexing



The uplink and downlink
channels are on same
frequencies but occur at
different time intervals
TDD frame has a fixed
duration and is divided into
uplink and downlink
subframes
TDD framing is adaptive
IEEE 802.16 Networks
(MAC Layer Communication)


Connection oriented architecture
 Each communication belongs to a particular connection and
within that connection to a particular service flow class
Channel access
 UL-MAP and DL-MAP transmitted at the start of each frame
 UL-MAP defines slots for uplink channel access as well as
data burst profiles
 DL-MAP defines downlink data burst profiles
IEEE 802.16 Networks
(Bandwidth Allocation & Request)
SS Bandwidth Request



Use contention request
opportunities when polled by
the BS
Send a bandwidth request in
an allotted time slot
Piggyback a bandwidth
request on a data packet
BS Bandwidth Allocation



Grant per subscriber station
Grant per connection
Allocation decision based on
available resources,
bandwidth request and
Quality of Service
IEEE 802.16 Networks
(What is Qos)




Quality of Service, an architecture which treats packets
differently
One flow receives preferential treatment at the cost of other
lesser important flows
Guaranteed services are provided to the end users
QoS guarantees can be for the following

Delay

Delay Jitter

Reserved Bandwidth

Error Rate
IEEE 802.16 Networks
(QoS Classes)

WiMAX defines four services classes
 Unsolicited Grant Service
 For real time traffic with fixed packet size
 Provides fixed size unsolicited data grants periodically
 Real Time Polling Service
 For real time traffic with variable packet size
 BS offers unicast polls
 Contention isnt allowed but piggybacking is permissible
 Non Real Time Polling Service
 For non realtime flows requiring variable sized data grants
 BS offers unicast polls.
 Contention as well as piggybacking is allowed
 Best Effort
 BS doesn’t offer unicast polls
 SS reserves bandwidth by contention and piggybacking
IEEE 802.16 Networks
(Scheduling Requirements)

A good scheduling algorithm must catered to the following:
 Bandwidth utilization must be efficient. For example,
resources shouldn’t be allocated to a bad link.
 The scheduler should be able to cater to different QoS
requirements with a guarantee on the long term throughput
for all connections.
 The scheduler should be fair in both the long run as well as
the short run.
 The scheduler should have a low complexity so that the
decision making doesn’t waste time.
 The system should be scalable.
IEEE 802.16 Networks
(Scenario)






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WiMAX extension for NS2 by Chen et all
Five stationary SS nodes communicating through one BS node
All SS nodes equidistant from the BS
Five traffic types:
 Unsolicited Grants Service (Video)
 Real Time Polling Service (VoIP)
 Extended Real Time Polling Service (VoIP with silence suppression)
 Non real time Polling Service (FTP)
 Best Effort (web traffic)
Priority queuing based on these traffic types
Weighted Round Robin scheduling
Studied the effect of traffic, transport protocol and frame size on the throughput and
drop rate
IEEE 802.16 Networks
(Effect of Transport Protocol)
Invidual Throughput
12500
BE
12000
BE
11500
BE
BE
11000
BE
10500
1 2 3 4 5
6 7 8 9 10
tim e (sec)
Only BE Traffic Over UDP
throughput (bytes/sec)
throughput (bytes/sec)
Invidual Throughput
20000
15000
BE
BE
10000
BE
BE
5000
0
1 2 3 4 5
6 7 8 9 10
tim e (sec)
Only BE Traffic Over TCP
IEEE 802.16 Networks
(Effect of Transport Protocol)

Only BE traffic is used in all the five SS

Throughput graph is fairly similar for each traffic.

Variation in throughput is much lesser if TCP is used as compared to UDP.

Variation in throughput in the early seconds seen if UDP is used.

Almost no variation if TCP is used. However, the throughput jumps to a
much higher level after some time has elapsed.

If TCP is used, then the SS which had a higher throughput at the start
continues to have a higher throughput throughout the duration of the
simulation.

Aggregate throughput of the scenario is relatively stable if TCP is used as
compared to UDP.

The number of packets dropped at the BS is much higher in the case of
UDP and the number received is slightly higher in the case of TCP.
IEEE 802.16 Networks
(Effect of Transport Protocol)
45000
40000
35000
30000
25000
20000
15000
10000
5000
0
Invidual Throughput
BE
rtps
UGS
nrtps
ertps
1 2 3 4 5 6 7 8 9 10
tim e (sec)
Each SS Different Traffic Over UDP
throughput (bytes/sec)
throughput (bytes/sec)
Invidual Throughput
250000
be
200000
nrtps
150000
rtps
100000
ertps
50000
ugs
0
1
3
5
7
9
tim e (sec)
Each SS Different Traffic Over TCP
IEEE 802.16 Networks
(Effect of Transport Protocol)

Each SS has a different traffic type

If UDP is used, rtPS has the highest throughput, followed by nrtps, UGS,
ertPS and finally BE. UGS and ertPS are relatively equal. nrtPS, ertPS and
BE have the same least starting throughput which increases according to
the traffic type. BE remains the same throughout.

If TCP is used, then all the traffic types have the same starting throughput
which is relatively stable for BE and nrtPS. It is also stable for UGS but
there is a jump after an initial time period has elapsed. The ertPS
fluctuates and shows an increasing trend. rtPS has the largest and also
the greatest amount of fluctuations.

There are large fluctuations in the throughput at the start if TCP is used
and then the throughput becomes stable. However if UDP is used then
there is a large jump in the beginning and then the graph has small
fluctuations around an average point.

The number of packets dropped at the SS is much higher if TCP is used.
Highest loss in BE and nrtPS followed by ertPS, UGS and rtPS.
IEEE 802.16 Networks
(Effect of Transport Protocol)
Invidual Throughput
700000
600000
node1
500000
node2
400000
node3
300000
node4
200000
node5
100000
0
1
3
5
7
9
tim e (sec)
Each SS All Traffics Over UDP
throughput (bytes/sec)
throughput (bytes/sec)
Invidual Throughput
20000
node 1
15000
node 2
10000
node 3
node 4
5000
node 5
0
1
3
5
7
9
tim e (sec)
Each SS All Traffics Over TCP
IEEE 802.16 Networks
(Effect of Transport Protocol)

Each SS has all the five traffic types

If UDP is the underlying protocol, then the first SS has a much higher
throughput as compared to all the other SS which show a similar traffic
pattern.

If TCP is used, then all the SS show the same pattern around the same
average throughput.

The aggregate throughput takes a large jump in the beginning and then
remains constant if UDP is used. However if TCP is used then there is
a relatively smooth curve.

The number of packets dropped is much higher if UDP is used.

The number of packets received by the BS is higher if TCP is used.

If UDP is used then the number of packets received is much higher at
the first SS compared to the other four SS.
IEEE 802.16 Networks
(Effect of Frame Size)
Individual Throughput
250000
25000
20000
15000
500
10000
200
5000
0
throughput (bytes/sec)
throughput (bytes/sec)
Individual Throughput
200000
150000
500
100000
200
50000
0
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
itm e (sec)
tim e (sec)
500 vs 200 using UGS Over UDP
500 vs 200 using UGS Over TCP
IEEE 802.16 Networks
(Effect of Frame Size)



If UGS over UDP is used, traffics having different sizes show similar
behavior, but for a larger size the starting throughput is lower.
If UGS over TCP is used, a smaller size will cause stability in throughput
while a larger size may face a large data burst.
The throughput is higher for a smaller frame size.
Conclusion

There is much research opportunity in this area.

Scheduling architectures are required which provide QoS
guarantees without being unfair to lower priority traffics.

Scheduling should be such that the SS further away from the
BS are not treated unfairly.

Scheduling should be such that as the SS move further away
from the BS their QoS gaurantees should be provided.
References
[1] C. Cicconetti, L. Lenzini, and E. Mingozzi, “Quality of Service Support in IEEE 802.16 Networks”
[2] http://en.wikipedia.org/wiki/WiMAX
[3] S. Ryu, B. Ryu, H. Seo, and M. Shin, “Urgency and Efficiency based Wireless Downlink Packet Scheduling Algorithm in OFDMA System”
[4] W. Park, S.Cho, and S. Bahk, “Scheduler Design for Multiple Traffic Classes in OFDMA Networks”
[5] K. Vinay, N. Sreenivasulul, D. Jayaraml, and D. Das, “Performance Evaluation of End-to-end Delay by Hybrid Scheduling Algorithm for QoS in
IEEE 802.16 Network”
[6] J. Sun, Y. Yao, and H. Zhu, “Quality of Service Scheduling for 802.16 Broadband Wireless Access Systems”
[7] W. K. Wong, H. Tang, S. Guo, and V. C. M. Leung, “Scheduling Algorithm in a Point-to-Multipoint Broadband Wireless Access Network”
[8] S. A. Xergias, N. Passas, and L. Merakos, “Flexible Resource Allocation in IEEE 802.16 Wireless Metropolitan Area Networks”
[9] H. S. Alavi, M. Mojdeh, and N. Yazdani, “A Quality of Service Architecture for IEEE 802.16 Standards”
[10] J. Chen, W. Jiao, and H. Wang “A Service Flow Management Strategy for IEEE 802.16 Broadband Wireless Access Systems in TDD Mode”
[11] N. Liu, X. Li, C. Pei, B. Yang, “Delay Character of a Novel Architecture for IEEE 802.16 Systems”
[12] M. Mehrjoo, M. Dianati, X. Shen, K. Naik “Opportunistic Fair Scheduling for the Downlink of IEEE 802.16Wireless Metropolitan Area
Networks”
[13] G. Song, Y. Li, “Utility-Based Resource Allocation and Scheduling in OFDM-Based Wireless Broadband Networks”
[14] F. De Pellegrini, D. Miorandi, E. Salvadori and N. Scalabrino. “QoS Support in WiMAX Networks: Issues and Experimental Measurements”
[15] Christian Müller, Anja Klein, Frank Wegner, “Coverage Extension of WiMax Using Multihop in a Low User Density Environment”
[16] D. Tarchi, R. Fantacci, and M. Bardazzi, “Quality of Service Management in IEEE 802.16 Wireless Metropolitan Area Networks”
[17] X. Meng, “An Efficient Scheduling For Diverse QoS Requirements in WiMAX”
[18] http://ndsl.csie.cgu.edu.tw/wimax_ns2.php
[19] Jenhui Chen et al, "The design and implementation of WiMAX module for ns-2 simulator", Proceeding from the 2006 workshop on ns-2: the
IP network simulator
[20] http://www.antd.nist.gov/seamlessandsecure/doc.html
Q & A