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Building a Cellular IP Building a Cellular IP TestbedTestbed
Javier Gomez and Andrew .T. CampbellJavier Gomez and Andrew .T. CampbellColumbia UniversityColumbia University
comet.columbia.edu/wirelesscomet.columbia.edu/wireless
support from Ericsson, Intel, Nortel and IBMsupport from Ericsson, Intel, Nortel and IBM
Wireless IP views
Wireless IP
Telecomm world
IP world
3G, IP
3GPP, 3GPP 2
etc...
Mobile IP
Micro-mobility approaches
3G Wireless Existing schemes
– IMT-2000– too many proposals
Pros– smooth mobility support
Cons– circuit model – complex/expensive infrastructure (e.g. MSCs)– strictly based on hierarchical networks
Mobile IP Existing schemes
– IPv4 mobility with/without route optimization– IPv6 mobility
Pros– Simple and scalable mobility solution
Cons– handoff latency and packet loss– signaling load and performance scalability– QOS
Micro-Mobility Schemes New proposals for fast handoff in IETF
– hierarchical foreign agents (Nokia,96)– Cellular IP (Columbia/Ericsson,98)– Hierarchical IPv6 (INRIA,98)– HAWAII (Lucent,99)– THEMA (Lucent/Nokia,99)
Other initiatives– ICEBERG (UCB/Ericsson)
Project started at Columbia with Ericsson, 97 Simple Vision:
– combining the strengths of “Cellular + IP” without inheriting their weaknesses.
Cellular IP inherits cellular technology principles– but implements these around the IP
paradigm Observation
– 3G and Internet fundamentally different
Cellular IP Project
fast and seamless handoff– per-mobile routing soft-state
real-time location tracking - implicit paging support for active and idle users
– “passive connectivity” single scalable protocol simplicity
– no new packet formats, encapsulation or address space
– distribute mobile-aware functions (e.g., costly MSC kit)
built a foundation for QOS support
Design Goals
Macro/micro mobility
base station
home agent
Internet w/ Mobile IP
mobile
mobile access network
base station – wireless access point– routes IP packets– integrated cellular control found in MSC and BSC– IP routing replaced by Cellular IP routing
gateways– mobile IP support macro-mobility– mobiles hosts attached to the network use the IP address of
the gateway as their Mobile IP COA– inside the network hosts are identified by their home
addresses and packets are routed without tunneling or address conversion
mobile host
Building Blocks
MobileIP/CellularIP
Location management & handoff are integrated with routing
data packets transmitted by a node are used to establish location and routing “soft-state”
no explicit signaling is required uplink packets are routed to the gateway on a
hop-by-hop basis downlink packets a routed on the reverse path idle mobiles allow state to timeout in-band paging mechanism locates idle hosts
Protocol Overview
Network Model
Internet w/ Mobile IP
foreign agent
home agent
C
B
E
D
F
G
R
R
Cellular IPMobile IP
Internet Mobile Access Network
A
Main Algorithms – Routing, handoff and paging
Uplink Packets: Shortest Path
Internet w/ Mobile IP
foreign agent
home agent
C
A
B
E
D
F
G
R
RR
host
Uplink packets: Create Location Information
Internet w/ Mobile IP
foreign agent
home agent
C
A
B
E
D
F
G
R
RR
host
Redirected uplink packets create new downlink path Optimal reuse of previous path
Hard Handoff
Internet w/ Mobile IP
foreign agent
home agent
C
A
B
E
D
F
G
R
RR
host
Delay device for synchronization
Semi-Soft Handoff
Internet w/ Mobile IP
foreign agent
home agent
C
A
B
E
D
F
G
R
RR
host
Control packets are regular IP packets with no payload They update routing entries Discarded before reaching the internet
OK, Some control Messaging
Internet w/ Mobile IP
foreign agent
home agent
C
A
B
E
D
F
G
R
RR
host
paging mechanism in-band signaling for paging using live data target and broadcast technique
Location Management of Idle Hosts
home agent
Internet w/ Mobile IP
foreign agent
C
A
B
E
D
F
G
R
RR
host
mobile and network have shared secret key– control messages are authenticated– Cache mappings cannot be created or
modified by data packets– control packets are ICMP– control packets must contain
timestamp and authentication information
Security
Implementation Model
Cellular IP Testbed I
Cellular IP Testbed II
Cellular IP nodes/mobiles hosts: Pentium 300 MHz
wired links– ethernet 10/100 Mbps
wireless links– Wavelan 2 Mbps– Lucent 802.11, 2-11 Mbps– Aironet 802.11, 2-11 Mbps
Hardware
Downlink Packet Loss @Handoff
TCP Throughput @Handoff
Cellular IP uses per-host routes in order to support high performance handoff
– does N impacts the performance?
Scalability
Cellular IPnode100 Mbps
N
100 Mbps Testmobilettcp
cellular IP node’s throughput
The main scalability bottleneck is the overhead associated with life tracking of mobiles
Cellular IP achieves scalability by:– separation of location management
between idle/active mobile hosts
Scalability
Totalpopulation of mobiles
idle
active
Today:– target coverage and high throughput as
primary design goals• there is no provision for frequency reuse• power control is difficult
Tomorrow?:– data access still random (CDMA/CSMA)– there is some sort of control channel...
• Improved frequency reuse/Handoff support• slotted paging = power savings
(Wireless LANs today/tomorrow?)
Summary 3G is being redefined toward IP centric solutions Number of new proposals on micro-mobility New 3GIP working group Cellular IP
– is capable of combining the strengths of “Cellular and IP” approaches without inheriting their weaknesses
source code available November 99– comet.Columbia.edu/cellularip
DEMO Cellular IP at IEEE MOMUC99
Andrew T. Campbell Javier Gomez Sanghyo Kim Bill Paul Andras G. Valko (Ericsson Research) Zoltan Turanyi (Ericsson Research) Chieh-Yih Wan
Cellular IP Team
Papers– "Design, Implementation and Evaluation of
Cellular IP", IEEE Personal Communications, August 200.0
Internet Draft– Cellular IP, Internet Draft, draft-ietf-mobileip-
cellularip-00.txt, IETF Mobile IP Working Group Document, December 1999.
Papers, IDs and source code– comet.columbia.edu/cellularip/publications.htm
Publications
