1. Location Management for Mobile Networks
4과 Seminar
1999년4월 22일
전 화 숙
서울대학교
컴퓨터공학과

2. Outline 1. Introduction 2. Cellular Systems
3. Mobility Management: Location Management
4. Mobility Management: Handoff
5. Summary
* References
컴퓨터공학과, 전화숙
4과 세미나 ( )

3. Introduction Wireless Network: 배선공사 불필요  flexible user interface
Mobile Network: 단말기 휴대 가능, 사용자의 이동성 보장
Characteristics of wireless channel
전송매체: radio/infrared
radio (infrared) propagation: 반사, 회절, 굴절
 shadowing, fading, multipath
time-varying channel  dynamic channel capacity
 hostile transmission environment
Point-to-Point Communications:
source coding, channel coding, interleaving, modulation
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

4. Introduction Radio frequency 제한된 Resource
time-varying channel  dynamic channel capacity
효율적 이용 필요  셀룰러 기술, 다중 접속 기술
Cellular system
주파수 재사용 (spectrum reuse)
macrocell, microcell, picocell
다중 접속 (Multiple Access) 기술
한 cell 내에서 주파수 자원의 효율적 분배
FDMA, TDMA, CDMA, and hybrids
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

5. Information Rate (Mbps)
Introduction
Comparison of various wireless access systems
Wired Terminal
Information Rate (Mbps)
Fixed
Movable
or Still
Fast
Slow
Private
Indoor
Public
Cordless
Phone
0.1
100 10 1
Cellular C T 2
IMT-2000
Wireless LAN
Mobility
MBS*
*MBS: Mobile Broadband Systems
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

6. 이동통신망의 구조
Cellular Networks의 구성: 무선망 (radio network)  고정망 (fixed network)
Fixed Network BS
Radio Network
BS: Base Station
MS: Mobile Station (Terminal)
Cell MS
MSC
VLR AC
HLR
PSTN
Data Network
IWF
MSC: Mobile Switching Center
HLR: Home Location Register
VLR: Visitor Location Register
AC: Authentication Center
IWF: Interworking Function
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

7. Why Cellular? 주파수 재사용 (spectrum reuse)  Capacity 제고
Wider coverage in service area
초기의 이동통신 시스템 Cellular System BS MS
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

8. 셀룰라(Cellular) 시스템: Macrocell/Microcell
Overlaid microcells and macrocells configuration
Microcell
MSC
Macrocell
Overlaid microcells and macrocells configuration
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

9. Cellular 구조로부터 야기되는 문제: 이동성 관리
이동성관리 (Mobility Management)
위치관리 (Location Management):
목적: To deliver mobile-termination calls (or units of multimedia traffic) to appropriate (unpredictably) moving mobiles
구성요소:
Location Registration (incl Location Update),
Call Delivery (incl Paging)
Handoff:
call(or connection)이 설정된 상태(e.g., 통화 중)에서, 그 단말기를 service하는 기지국을 변경하는 일
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

10. Location Management Location Management includes two major tasks:
Location Registration: (어떤 단말기의) 최신의 location 정보를 유지하기 위해 location data base (location register)를 update하는 과정
Call Delivery: mobile-termination call이 발생했을 때, location data base의 information에 기초하여 목적 단말기를 찾는 과정
무선망 내에서의 작업:
location update: location registration을 위해, 단말기가 그 자신의 현재 위치를 network에 보고하는 일
paging (alerting): call delivery시 목적 단말기를 polling하는 신호를 정해진 영역내의 모든 cell로 방송하는 일
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

11. IS-41 IS-41C: MSC와 MSC 사이, MSC와 HLR 사이의 interface 표준
EIA/TIA IS-41-C, “Cellular radiotelecommunications intersystem operations,” 1995.
현재 국내의 CDMA 셀룰러 이동전화 및 PCS 시스템에 사용
Two-level data hierarchy:
Home Location Register (HLR), Visitor Location Register (VLR)
Location Register (LR): 대규모 database, 각 가입자의 mobile identification number (MIN, 전화번호)에 대하여 그 단말기의 현재의 location (cell 또는 registration area) id 정보를 수록
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

12. IS-41 Two-level data hierarchy :
LR update를 위한 Long haul traffic을 줄이는 것이 목표
HLR: MIN (전화번호)과 VLR id 수록
VLR: MSC마다 위치, MIN과 LA id 수록
구현 예) 전화번호의 국번별로 HLR이 정해짐 동작
동일 VLR 관장 구역 내에서 LA만 바뀌는 경우 (MSC내 이동) : VLR만 update하면 됨  long haul trunk 을 이용할 필요 없음
VLR 구역이 바뀌는 경우 (MSC간 이동) :
새로운 MSC는 HLR을 통해 해당 전화번호의 profile을 요청
 새로운 VLR에 신규등록  기존 VLR에서 삭제
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

13. Location Registration
Location Registration Procedure
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

14. Call Delivery Call Delivery Procedure 컴퓨터공학과, 전화숙 4과 세미나 (1999. 4.)
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

15. Location Update Location update: Reporting location to Network
Cell 단위 location update의 문제점:
cell 이동 시마다 location update를 하면 너무 빈번한 update 발생
Location Area (LA)
몇 개의 cell을 grouping
 Registration Area (RA) or Location Area (LA)
cell 이동 시가 아니라, LA이동 시에만 update
LR의 cell id field를 LA id로 대체
ex) Paging Area가 LA와 일치하는 경우, LA에 속한 모든 BTS를 통해 paging
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

16. Location Area Example for Concept of LA G A B C D E F Cell Boundary
Location Area (LA) Boundary
Moving Path
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

17. Location Update Movement-based location update:
according to the change of LA
Time-based location update:
according to the timer expiring
Distance-based location update:
according to the distance from the last reported base
Probabilistic location update
according to the result of persistence test
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

18. Paging
Paging: The signaling process to find out called MS when an mobile-termination call arrives.
Paging strategy: Example
(Step 0) Page the cell last recorded
(Step 1) Page the LA last recorded
(Step 2) Page the surrounding LAs
(Step 3) Page all the cell in the service area
total location management cost = registration cost + paging cost
Problem: minimize the total cost
frequent location update increases the registration cost
infrequent location update increases the paging cost
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

19. Paging Requirement for Paging Scheme simple implementation
MS: low power-consumption
minimize computational overhead
operate with less information (ex, without knowledge on probability distribution on mobility)
minimize the registration/paging cost
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

20. Location Management LA size : location update와 paging cost간의 tradeoff
Location management cost = location update cost+ paging cost
Call-rate와 mobility가 parameter
for high call-rate:
paging cost를 줄이는 것이 좋음
small LA
for high mobility:
location update cost를 줄이는 것이 좋음
large LA
call-to-mobility ratio를 통해 LA size를 결정
컴퓨터공학과, 전화숙
4과 세미나 ( )

21. Location Management Location Management Scheme의 Performance 측정
call-to-mobility ratio 당 DB transaction 수
call-to-mobility ratio 당 hop 수
call-to-mobility ratio 당 signaling traffic 양
Strategy 결정:
call-to-mobility ratio – cost graph에서 operating point를 찾는 작업
Intelligent paging:
각 단말기에 대해, 그 단말기가 존재할 가능성이 높은 LA의 list 유지
각 LA를 확률이 높은 순으로 sequential하게 paging
location update를 하지 않을 수 있음
컴퓨터공학과, 전화숙
4과 세미나 ( )

22. Handoff (Handover) Cell B Cell A 컴퓨터공학과, 전화숙 4과 세미나 (1999. 4.)
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

23. Handoff Procedure Soft Handoff
원래의 통화접속 기지국과의 통신링크를 단절하기 전에 새로운 기지국과의 통신링크를 개설
soft handoff 기간에는 두 기지국 모두와 통신링크 유지
Make-before-Break
현재 국내의 CDMA 셀룰러 이동전화 및 PCS 시스템에 사용
cf) two-way soft handoff , three-way soft handoff
cf) Softer Handoff
Hard Handoff
Break-before-Make
AMPS(아날로그)나 TDMA에서 사용
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

24. Handoff Procedure in IS-95 CDMA
Soft Handoff Procedure
candidate set : active set에 들어갈 가능성이 있는 기지국 set
active set : handoff에 들어가 있는 기지국 set
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

25. Handoff: Resource Management
New Call vs. Handoff Call
The probability of interrupting or aborting a call due to handoff should be considerably less than that of blocking a new call.
 handoff are allocated additional capacity.
Example: guard channels
For existing cellular: circuit-switched call environment
Until a specified channel utilization threshold is reached: new calls and handoff call are treated identical
At the threshold point: new calls are blocked and handoff calls only are allowed in the system.
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

26. Handoff under Multimedia Environment
Overlaid microcells and macrocells configuration
 very complex handoff procedure
Complicate Resource Management
There are various bandwidth requirements in a cell.
More dynamic bandwidth assignment is required
Example
For a new call to be admitted:
there should be exist the available capacity in its current cell and in adjacent cells.
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

27. Summary Mobile network Combination of radio network and fixed network
Cellular system  Mobility management
Mobility management
location management
handoff
Further studies:
mobility management for advanced networks:
e.g., IMT-2000 and mobile ATM,
supporting mobile multimedia services,
having complex cell architecture.
· Code Division Multiple Access (CDMA) Systems: Advantages in capacity
· Existing CDMA Systems:
- Frequency division duplex (FDD) between uplink and downlink
- Uplink and downlink utilize equal bandwidth
- Major traffic is voice
· Conversational voice communications:
the traffic volumes of uplink and downlink are similar to each other usually.
· Next generation (so-called the third generation) mobile communications systems:
multimedia services, e.g., Internet access, electronic newspaper, or mobile computing
· Since mobile station (MS) tends to become a small and light one, the information data base and the computing power for multimedia services tend to locate at the network side rather than at the MS.
Þ utilization of radio resource is strongly biased toward the downlink against the uplink
Introduction
Þ bandwidth waste and capacity degradation
· This problem caused by traffic unbalance between two links is inherent in any FDD system.
Þ Time division duplex (TDD) systems can be a solution.
컴퓨터공학과, 전화숙
4과 세미나 ( )

28. References
A. Bar-Noy, I. Kessler, and M. Sidi, “Mobile users: To update or not to update?,” Wireless Networks, vol. 1, no. 2, pp , 1995.
I. F. Akyildiz, and S. M. Ho, “On location management for personal communications networks,” IEEE Commun. Mag.,vol. 34, no. 9, pp , Sept
D. G. Jeong and W. S. Jeon, “Probabilistic location update for advanced cellular mobile networks,” IEEE Commun. Letters, vol. 2, no. 1, pp. 8-10, Jan
EIA/TIA IS-41-C, “Cellular radiotelecommunications intersystem operations,” 1995.
Qualcomm Inc., The CDMA Network Engineering Handbook, Vol. 1: Concepts in CDMA, San Diego, USA, March 1993.
· A concept of CDMA/TDD system was proposed.
· The efficiency of the system under multimedia environment has been demonstrated: The frequency utilization of CDMA/TDD is very high even when the uplink and downlink traffic volumes are unbalanced.
· This, in turn, reduces drastically the blocking rate of multimedia calls (connections) in the proposed system compared with that in the traditional CDMA systems where the uplink and downlink use equal bandwidth.
· The proposed system can be used for third generation mobile communications systems and wireless ATM networks.
· Further works:
- Markov analysis
- Bandwidth allocation and call admission strategy based on multi-cell model
- Mobility management issues (e.g., handoff) in this CDMA/TDD system.
컴퓨터공학과, 전화숙
4과 세미나 ( )