Transcript Introduction to Wireless Communications & Networks

Mobility Management
Mobility management enables telecomm
unications networks to
 Locate roaming mobile terminals (MTs) for
call delivery
 Maintain connections with MTs that change
their points of attachment
Introduction (cont.)
What is mobility management doing?
 1. Location management
location registration (or location updat
e)
call delivery (or search)
 2. Handoff management, caused by
signal strength deterioration
user mobility
Intracell vs. intercell handof
Introduction (cont.)
Two kinds of handoff
 soft handoff vs. hard handoff
Three ways to handoff
 network-controlled handoff (NCHO - AMPS)
 mobile-assisted handoff(MAHO - GSM, IS-
95)
 mobile-controlled handoff (MCHO - DECT,
PACS)
Introduction (cont.)
Three-Stage of process for handoff
 1. Initiation: the user, a network agent, or c
hanging network condition
 2. New connection generation: finding new
resources and performing routing operation
 3. Data flow control : delivery of data accor
ding to agreed-upon service guarantees
Introduction (cont.)
Handoff protocols usually rely on
 routing
 resource management
 data delivery systems
Handoff algorithms are network-protocol-dep
endent
It needs standardized wireless netowork archit
ecture to access regional, national and global
services as efficiently as those on the local lev
el
Future Wireless Network Archite
cture
The ITU has specified IMT-2000
 Hierarchical cell structure (HCS)
 Global network roaming
 Expanding radio spectrum
Future Wireless (cont.)
Hierarchical cell structure (HCS) consisti
ng of
 Picocells (in-building: high-capacity)
 Micro- and macrocells (urban and suburba
n terrestrial networks)
 Large satellite cells
 Base transceiver stations (BSs or BTSs) ca
n access terrestrial networks (PSTN, ATM, I
nternet)
Future Wireless (cont.)
 Satellite networks communicate with fixed e
arth stations (FESs)
 Mobile terminal (MT)
 Location area (LA): consist of multiple cells
 Cell site switch (CSS): govern one or more
BSs and will provide access to the serving
mobile network (PLAN, Internet, ATM, or sat
ellite)
Future Wireless (cont.)
Global roaming
 Terminal mobility, personal mobility, a
nd service provider mobility
Radio spectrum
 ITU promotes harmonized utilization o
f the radio spectrum and to facilitate t
he development of global PCS
Next generation network service portability
Mobility Management for PLMN
Architecture: key components
 Mobile terminal (MT)
 Base station (BS)
 Mobile switching center (MSC)
 Home location register (HLR)
 Visitor location register (VLR)
Mobility Management for PLMN (co
nt.)
Two standards for location management
in the PLMN:
 1. IS-41 for AMPS, IS-54, IS-136, PACS
 2. GSM MAP for GSM, DCS-1800, PCS-190
0
Both standards: two-level database hier
archy
The following figure shows the call deliv
ery procedure
Mobility Management for PLMN (co
nt.)
Location management research
 Database architecture
 Centralized vs. distributed
 Location update
 Time based (at a constant time interval)
 Movement based (movement threshold across
cell boundaries)
 Distance based (distance threshold): best perf
ormance but highest overhead
Mobility Management for PLMN (co
nt.)
 Terminal paging (a tradeoff between
paging cost vs. paging delay)
Paging under delay constraints
Update and paging under delay constr
aints
No single scheme that clearly outp
erforms the others under all system
parameters
Location Management in
3G UMTS
The service area is partitioned into Gate
way Location Areas (G-LAs)
A G-LA is further partitioned into Locati
on Areas (LAs)
An LA consists of a group of cells
The following figure shows a three-tier
mobility databases: HLR, GLR (optional),
and VLR
Location Management in
3G UMTS (cont.)
Location Management in
3G UMTS (cont.)
An HLR location update is performed wh
en an MT crosses a boundary of a G-LA
A GLR location update is performed wh
en an MT crosses a boundary of an LA
A VLR location update is performed whe
n an MT completes d movements betwe
en cells, where d is the movement thres
hold (movement-based location update)
Types of Handover in
3G WCDMA Mobile Networks [4]
4 types of handover (HO):
 Intra-system HO
 Intra-frequency HO
 Inter-frequency HO
 Inter-system HO
 Hard HO
 Intra-frequency HO
 Inter-frequency HO
Types of Handover in 3G WCDMA
Mobile Networks [4] (cont.)
 Soft HO and softer HO
 During soft HO, a mobile simultaneously com
municates with two (2-way SHO) or more cells
belonging to different BSs of the same RNC (i
ntra-RNC) or different RNCs (inter-RNC)
 In softer HO, a mobile is controlled by at least
two sectors under one BS (RNC not involved)
 SHO and softer HO are only possible within on
e frequency (intra-frequency HO)
Scenarios of Diff. Types of HO [4]
Mobility Management for Mobile IP
Mobile IP architecture (Figure)
 Discovery: How an MN finds a new Internet
attachment point when it moves from one pl
ace to another
 Registration: How an MN registers with its H
A (an internet router)
 Routing and tunneling: How an MN received
datagrams when it is away from home
Mobile IP location management (Figure)
Mobility Management for Mobile IP
(cont.)
Location registration
Handoff management
 Smooth handoff: for maintaing QoS
 Routing and Tunneling
Open probems
 Simultaneous binding: MN can maintain several CoA
s at one time
 Regionalized registration: localize the registration to
the lowest common FAs
 Security: protect the CoA’s and HA’s
Mobility Management for WATM
It focuses on 4 issues
 Latency
 Message delivery
 Connection routing
 Quality of service (QoS)
Mobility Management for WATM (c
ont.)
Deal with location management, termina
l paging, and handoff
For movement from position B.1.2 to p
osition A.2.2, the location registration pr
ocedure is shown as follows:
Mobility Management for WATM (c
ont.)
Handoff management research
 Full connection re-routing
 Route augmentation
 Partial connection re-routing
 Multicast connection re-routing
 maintaining the potential handoff connection i
n addition to the original connection, reducing
the time spent in finding a new route for hando
ff
Mobility Management for Satellite N
etworks
Satellite location management research
 The development of new LA definitions for LEO sate
llite networks
 Coverage area of a single satellite consists of small
-sized cells, which is called as spotbeams
Satellite handoff management research
 Intersatellite handoff
 Spotbean handoff (intrasatellite handoff)
 Link handoff: satellites near to polar regions turn off
their links to other satellites in the neighbor orbits;
Ongoing calls passing through these links need to b
e rerouted
Research Issues for Integrated Wir
eless Networks
The next generation of wireless networks prom
ises mobility without geographical constraints
or being tied to one particular network
Any network equipped for unified operation m
ust be able to support
 Inter-carrier (or intersystem) handoff
 Personal mobility
 Location management for a heterogeneous network
Mobility-related Research Issues f
or Next Generation Wireless Netwo
rks
Software radio
Location management
Inter-system handoff
Addressing and identification
Database issues
Routing issues
Standardization