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Aspects of Coexistence Between WiFiand HSDPA
Final Workshop of CROSSNET (Cross-layer design and network planning for B3G systems)
Orlando CabralValdemar Monteiro
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Final Workshop of CROSSNET
| Lisboa, 19 de Fevereiro de 2008
Outline
• Global view of Cross-layer design and network planning for B3G systems (CROSSNET)• Cross-layer design• Cross-system and convergence
• Cross-layer studies for IEEE 802.11e• Differentiation mechanisms• Simulator validation• Cross-layer design proposal and results
• RAT selection for HSDPA and IEEE 802.11e• Interoperability scenario • Algorithm description• Results and scientific impact
• Conclusions and future work
3 | Lisboa, 19 de Fevereiro de 2008
Global view of CROSSNET - Objectives and work Organization
• The project was divided into three main areas: • Traffic modelling and Quality of Service (QoS)• Medium Access Control (MAC) definition and cross-layer
design• Network planning and optimisation, synthesis and integration
• In a scenario of heterogeneous networks, the interoperability among available radio access technologies should be seen by mobile users as the ability to successively attach to the access points and bases stations in a transparent way
Final Workshop of CROSSNET
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Coexistence
| Lisboa, 19 de Fevereiro de 2008
Final Workshop of CROSSNET
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Global view of CROSSNET - Cross-layer
• Implementation and validation of the High-Speed Downlink Packet Access (HSDPA) and IEEE 802.11e MAC protocol
• HSDPA R5 system level simulator facilitates the design, evaluation and optimization of scheduling and link-adaptation policies
text
NodeB
Channel Models
and Interference
Traffic Model
and Queues
Queue
Manager
DRA
L L IScheduler
Link
Adaptation
Power
Code
CQI
Slot
Radio
Resources
SIR
Cell Deployment and
Mobile Dynamics
H-
ARQ
H-
ARQ
UE
ARQ msg
(Ack/Nack)
Final Workshop of CROSSNET
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Global view of CROSSNET - Cross-system
• MOTION (HSDPA) and WE-MOVE (WiFi) simulation tools were integrated under a common simulation platform to perform Common Radio Resource Management studies• RAT selection for multimedia services
• Also UMTS (HSDPA) – WiMAX interoperability is being considered, however at this stage the WiMAX simulation platform is being validated for IEEE 802.16e Dynamic Resource Allocation strategies
Final Workshop of CROSSNET
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IEEE 802.11e – IFSs relationships
Priorities• SIFS (Short Inter Frame Spacing, IFS)
• highest priority, for ACK, CTS, polling response
• PIFS (PCF IFS)• medium priority, for time-bounded service using PCF
• AIFS (EDCA, arbitrary IFS, used by the QoS facility)• Priority depends of the access category.
Final Workshop of CROSSNET
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IEEE 802.11e – Block ACK
• The Block Ack mechanism is initialized by an exchange of ADDBA Request/Response frames.
• After initialization, blocks of QoS data frames can be transmitted from the originator to the recipient.
0.0E+00
5.0E+06
1.0E+07
1.5E+07
2.0E+07
2.5E+07
0 10 20 30 40 50
Stations
Goo
dput
[b/s
]BK
VI
VO
VI-BLOCK
BK-BLOCK
Final Workshop of CROSSNET
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IEEE 802.11 - State transition diagram
Final Workshop of CROSSNET
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Validation PHY layer without fragmentation
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SINR [dB]
Goo
dput
[Mb/
s]
Mod 8Mod 7Mod 6Mod 5Mod 4Mod 3Mod 2Mod 1
Final Workshop of CROSSNET
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Cross-layer concept used
OSI Model
BK BE VI VO
Virtual Collision Handler
Transmission
Attempt
Backoff
AIFS [0]
BC [0]
Backoff
AIFS [1]
BC [1]
Backoff
AIFS [2]
BC [2]
Backoff
AIFS [3]
BC [3]
Final Workshop of CROSSNET
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Cross-Layer for WiFi EDCA mode
• Scenario Description• WiFi system where a cell has a set N+1 IEEE 802.11e stations
communicating through the same wireless channel• Station 0 is the Access Point or QoS Access Points (QAP),
and the other N wireless terminals are QoS stations (QSTA)
• Novelties of Algorithm• Dynamically changing the Arbitration Inter Frame Spacing (AIFS) and
the contention window (CW) size, using as inputs delay and channel state information, can lead to enhanced channel utilization and system QoS
• By sharing network state information among users, optimal radio resource allocation parameters can be attained
Final Workshop of CROSSNET
13 | Lisboa, 19 de Fevereiro de 2008
Cross-Layer for WiFi EDCA mode• Algorithm Description
• The algorithm is based on dynamically changing the CW and the AIFS to assign a priority
• Fairness is provided by using as an input the metric
• QoS is ensured by using as an input
• Results • The proposed cross-layer algorithm showed
enhanced performance for voice traffic• can support at least 35% extra stations
with QoS
• Future work will target optimisation for the remaining service classes (background, streaming, and best effort)
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with scheduler-AP
without scheduler-AP
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0 10 20 30 40 50
StationsG
oodp
ut [b
/s]
without scheduler-AP
with scheduler-AP
Final Workshop of CROSSNET
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Conclusions- 802.11e Cross-layer Studies• The IEEE 802.11e event driven simulator allows the
evaluation and optimization of MAC protocols that includes acknowledgment policies and radio resource allocation strategies
• Utilizing a small CW for the voice access category leads to reduced goodput when the number of stations exceeds 65%
• Due to increased collisions causing the packet losses to exceed the retransmission threshold
• The proposed cross-layer algorithm showed enhanced performance for voice traffic
• Can support at least 35% extra stations with the required QoS
Final Workshop of CROSSNET
15 | Lisboa, 19 de Fevereiro de 2008
• This simulator will be extended:• to address the evaluation of interoperability protocols
for WiFi and HSDPA (in the context of the IT-MOTION tool)
• to investigate and validate Common Radio Resource Management (CRRM) techniques for HSDPA, WiMAXand WiFi
• Future work will target:• The joint application of block acknowledgment and
mixed traffic. • Handover policies between APs for multi-cell scenarios
Future work- 802.11e Cross-layer Studies
Final Workshop of CROSSNET
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RAT selection for HSDPA and IEEE 802.11e
17 | Lisboa, 19 de Fevereiro de 2008
RAT selection for HSDPA and IEEE 802.11e- Scenario Description
• Common coverage scenario with UMTS cell and with a WiFi hot-spot
• IP-based core network assumed that acts as the bridge between WiFi, and HSDPA
• NRTV services that can be streamed either over HSDPA, or WiFisystem
Final Workshop of CROSSNET
18 | Lisboa, 19 de Fevereiro de 2008
RAT selection for HSDPA and IEEE 802.11e- Algorithm description
• Suitability calculation for RAT selection among cells when new call is requested
• Targeted to flexible traffic• Flexibility imposes on the system, meaning that the service can be held
by each RAT
S (netw ork-centric suitability)
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Final Workshop of CROSSNET
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RAT selection for HSDPA and IEEE 802.11e-Novelties of Algorithm
• RAT selection based on load suitability where the systems are HSDPA and WiFi, under delay constraints services
• Concept of suitability is used in terms of preferred access system to accommodate the service, where Suitability can change as load increase
• The goal is to optimize the load in each RAT, measuring the diversity gain in quality of service (QoS) provisioning
Final Workshop of CROSSNET
20 | Lisboa, 19 de Fevereiro de 2008
RAT selection for HSDPA and IEEE 802.11e- Results and Scientific Impact• Results
• Gain of 60% on the supported QoS load achieved with the CRRM (intelligently adapted algorithm) over HSDPA alone
• Scientific impact• Exploring Common Management of the whole Radio Resources such that
the mobile assignment to different RATs is flexible and applicable to heterogeneous radio systems
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QoS
/ ser
vice
thro
ughp
ut (K
bps)
Number of user
CRMM vs HSDPA QoS Throughput
CRRM Goodput
NRTV offered load
HSDPA QoS
Final Workshop of CROSSNET
21 | Lisboa, 19 de Fevereiro de 2008
Conclusions and future work- HSDPA / WiFi CRRM studies
• CRRM was employed exploring the common management of the whole radio resources such that the assignment of mobiles to different radio technologies is flexible and considers the specific features of each system
• The goal of the proposed CRRM is to select the most appropriate radio network in co-located systems without deteriorating the quality of service
• Thanks to the CRRM algorithm, a 60% gain on system throughput (with QoS) can be achieved in a co-located HSDPA-WiFi system over HSDPA alone
Final Workshop of CROSSNET
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Future work- HSDPA / WiFi CRRM studies
• CRRM future work includes• Evaluation of the proposed algorithm for the HSDPA and
WiMAX 802.16e• Improvement on the algorithm to include load balancing between
HSDPA and 802.16e for established connections
Thank you !
http://www.e-projects.ubi.pt/crossnet
Final Workshop of CROSSNET