Download Unified Wireless Access in Hot

2003/12/2 報告者：黃立維
Unified Wireless Access in HotSpot Environment
Theodore B. Zahariadis, Member, IEEE, and
Nikos A. Nikolaou, Member, IEEE
IEEE COMMUNICATIONS LETTERS, VOL. 6,
NO. 6, JUNE 2002
Introduction
• Interoperability, and mobility are the major
factors of differentiation in 3G/WLAN
network.
• Mobile Internet applications with minimum
delay, investment and operational cost in
“hot spots” is to utilize already available
wireless technologies, in a complementary
and interoperable manner.
Introduction
• A prime challenge toward “hot-spot”
deployment is the provision of sessionoriented connections,providing roaming
between heterogeneous wireless
technologies.
• This letter addresses the Unified Wireless
Access(UniWA) architecture that is capable
of support seamless handoff, utilizing
existing wireless network technologies.
Unified Wireless Access Architecture
• UniWA is a hierarchical approach[2] that
primarily focuses on “hot-spots”.
– [2] D.Forsberg et al.,”Distributing mobility agents
hierarchically under frequent location update”presented
at 6th IEEE Int.
• UniWA servers are organized in groups of
UniWA Local Server(ULS), which cover
“hot-spot” location, and UniWA Regional
Server(URS), which cover larger,regional
locations.
Unified Wireless Access Architecture
• Roaming within the same “hot-spot” is
considered as local mobility.
• Horizontal handover vs Vertical handover
• Horizontal handover to a neighboring “hotspot” is considered as regional roaming and
is provided by utilizing the Mobile IP.
• HLR(Home Location Register)
• VLR(Visiting Location Register)
Unified Wireless Access Architecture
UniWA Roaming Algorithm
Wireless LAN覆蓋範圍限制
– results in “many vertical roaming request”,
“many routing entries updates”, and “many
VLR and HLR signaling messages”.
– In order to minimize this overhead in UniWA,
we postpone the HLR update and treat the
roaming in local or regional layer.
UniWA Roaming Algorithm
• What is the drawbacks of the limited
WLAN’s coverage ？
• When is the roaming algorithm applied ？
• In order to minimize this overhead in
UniWA, the author postpone the HLR
update and treat the roaming in local or
regional layer.
UniWA Roaming Algorithm
• When a terminal roams to a new servicing area a
route between the new and the old ULS is created.
• This is repeated until the local path’s length
reaches a predefined threshold(TL).
• Then an optimal routing algorithm is invoked to
check if the path has some cycles, and if not a
regional path’s path is created between the URS.
• This is repeated until the regional path’s length
reaches a threshold(TR).
• Then the HLR is informed and the complete path
to the UniWA terminal is refreshed.
UniWA Paging/Traffic Routing
Algorithm
• Due to UniWA roaming algorithm, the
paging algorithm is also modified.
• Additionally to the direct indexing from
HLR to the mobile terminal via the VHL,we
have to trace the regional and local paths if
exist.
• However, this penalty is not significant in a
PCS network the longer the forward chain,
the largest saving can be obtained.
Performance Analysis
• Adapt the analytical model “Portable movement
modeling for PCS network” [4]
– [4]Yuguang Fang, Senior Member, IEEE, and Yi-Bing
Lin, Senior Member,IEEE
•
•
•
•
•
•
TL：local path’s length
TR：regional path’s length
“l” 一個terminal平均calls數
“1/m”`:terminal落在一個ULS的平均時間
Call-Mobility Ratio：CMR=p=“l/m”
n：使用者在兩個calls之間，漫遊了幾個UniWA
server？
Performance Analysis
Performance Analysis_CROAM
• CR is the cost of an HLR update
• CULS and CURS the cost of inserting/updating a
routing entry (lengthen the path) to a ULS and a
URS, respectively.
• Pr(n) is the probability that different UniWA
servers are crossed within two calls.
– “Reducing Location Update Cost in a PCS Network”
Yi-Bing Lin, Senior Member, IEEE
Performance Analysis_Cpage
• If CLL and CRL are the costs to follow an entry in
the ULS or the URS routing table.
• CP is the cost for a direct terminal paging
Performance Analysis
Performance Analysis
Performance Analysis
My Conclusion
• UniWA address a new architecture, that
focuses on “hot-spot” and provides
seamless handoff between IEEE 802.11 and
2G.
• UniWA can solve the more handoff when
the CMR is small.