Cellular NetworkCellular Network
Wireless Computer CommunicationsWireless Computer Communications
Min-Xiou ChenMin-Xiou Chen
Why Cellular Mobile Why Cellular Mobile Telephone Systems?Telephone Systems?
Operational limitations of conventional Operational limitations of conventional mobile telephone systemsmobile telephone systems limited service capabilitylimited service capability poor service performancepoor service performance inefficient frequency spectrum utilizationinefficient frequency spectrum utilization
Mobility ManagementMobility Management
Mobility management enables Mobility management enables telecommunications networks totelecommunications networks to locate roaming mobile terminals (MTs) for locate roaming mobile terminals (MTs) for
call delivery call delivery ((location managementlocation management)) maintain connections with MTs that change maintain connections with MTs that change
their point of attachment their point of attachment ((handoff/handover handoff/handover managementmanagement))
Location ManagementLocation Management
MT periodically performs location MT periodically performs location registration (i.e., registration (i.e., location updatelocation update)) explicitly notify the network of its new access explicitly notify the network of its new access
point and store changes to its user location point and store changes to its user location profileprofile
when incoming calls arrive, the network when incoming calls arrive, the network performs performs call deliverycall delivery querying the user profile to deliver the calls to querying the user profile to deliver the calls to
the current cell location of the MTthe current cell location of the MT
IMSI ( International Mobile Subscriber Identity )IMSI ( International Mobile Subscriber Identity ) 行動用戶之全球唯一識別碼,作為驗證使用者身份行動用戶之全球唯一識別碼,作為驗證使用者身份 存於存於 HLR/AUCHLR/AUC 及燒錄於 及燒錄於 SIM SIM 卡中,卡中, 由由 MCC (Mobile Country Code )+MNC (Mobile Network MCC (Mobile Country Code )+MNC (Mobile Network
Code)+MSIN (Mobile Subscriber Identity Number)Code)+MSIN (Mobile Subscriber Identity Number) 所組成,所組成,長度不超過 長度不超過 15 15 碼,我國用 碼,我國用 15 15 碼,即 碼,即 IMSI = IMSI =
TMSI ( Temporary Mobile Subscriber Identity )TMSI ( Temporary Mobile Subscriber Identity ) 行動台行動台 中 中 SIM SIM 卡之區域性臨時識別碼卡之區域性臨時識別碼 長度不超過 長度不超過 32 32 位元。位元。 由 由 VLR VLR 產生,只在同一產生,只在同一 VLR VLR 服務區內有效。服務區內有效。
GSMGSM 身分之各種識別碼身分之各種識別碼 (Identity)(Identity)參數參數
GSMGSM 身分之各種識別碼身分之各種識別碼 (Identity)(Identity)參數參數
MSISDN ( Mobile Station ISDN )MSISDN ( Mobile Station ISDN ) 為行動台為行動台 (MS) (MS) 之全球唯一電話號碼之全球唯一電話號碼 長度不超過 長度不超過 15 15 碼,由碼,由 CC (Country Code)+NDC(National Destination CC (Country Code)+NDC(National Destination
Code)+SN(Subscriber Number)Code)+SN(Subscriber Number) 所組成,即 所組成,即 IMSI = 886-920-IMSI = 886-920-xxxxxxxxxxxx 。。
IMEI ( International Mobile Equipment Identity )IMEI ( International Mobile Equipment Identity ) 為行動台為行動台 設備之全球唯一識別碼,即手機製造產品序號設備之全球唯一識別碼,即手機製造產品序號 由由 TAC(Type Approval Code)+FAC(Final Assemble Code)+SNR(Serial TAC(Type Approval Code)+FAC(Final Assemble Code)+SNR(Serial
Number)+SP(Spare)Number)+SP(Spare) 所組成,長度 所組成,長度 15 15 碼。碼。 PIN ( Personal Identity Number ) PIN ( Personal Identity Number )
SIM SIM 卡之密碼,長度 卡之密碼,長度 4-6 4-6 碼碼 行動電話在插入 行動電話在插入 SIM SIM 卡後,需輸入正確之 卡後,需輸入正確之 PIN PIN 才能使用。 才能使用。
GSM Registration GSM Registration ProcedureProcedure
1: old TMSI + old 1: old TMSI + old VLR idVLR id
2: TMSI2: TMSIIMSIIMSI
3: location update3: location update
4: new TMSI4: new TMSI
5: registration 5: registration cancellationcancellation
HLR
VLRVLR
1
2
3
4
5
Call Delivery for Mobile Call Delivery for Mobile Terminated CallTerminated Call
MSC
MS
GMSC(INTX)
otherswitches
otherswitches
1 1
1
22
3
1
request roaming number
dial MSISDNallocate MSRN
3
routing
HLR VLR
3 paging
Registration Area Registration Area PlanningPlanning
Registration/Location Area (RA/LA)Registration/Location Area (RA/LA) consists of one or more cellsconsists of one or more cells the basic unit of registration/pagingthe basic unit of registration/paging
cell RA VLR PLMN GSM
Size of RA
Location update
Cost
Paging
Total
Hand-off (Hand-over)Hand-off (Hand-over)
Cell #1 Cell #2
Switches andProcessor
Hand-off (Hand-over):switches cells
Handoff ManagementHandoff Management
Ongoing calls are modified under two Ongoing calls are modified under two conditions: signal strength deterioration conditions: signal strength deterioration and user mobilityand user mobility
intra-cellintra-cell and and inter-cellinter-cell handoffs handoffs within and between cellswithin and between cells
softsoft handoff and handoff and hardhard handoff handoff without and with interruptions in radio linkswithout and with interruptions in radio links
Who Initiates the Who Initiates the Handoff?Handoff?
NCHONCHO (Network-controlled handoff) or (Network-controlled handoff) or MAHOMAHO (Mobile-assisted Handoff) (Mobile-assisted Handoff) the networks generates a new connection, the networks generates a new connection,
finding new resources for the handoff and finding new resources for the handoff and performing any additional routing operationsperforming any additional routing operations
MCHOMCHO (Mobile-controlled handoff) (Mobile-controlled handoff) the MT finds the new resources and the the MT finds the new resources and the
network approvesnetwork approves
Three Classes of Handoffs Three Classes of Handoffs in GSMin GSM
MSC
BSC BSC
BTS BTS BTS
MSC
BSC
BTS
MS MS
MS MS
MSMS
1. different BTS, same BSC
2. different BSC, same MSC
3. different MSC, same PLMN(old MSC=anchor MSC new MSC=relay MSC)
Technical TermsTechnical Terms
Call drop rateCall drop rate The probability that an ongoing call is The probability that an ongoing call is
dropped due to handoffdropped due to handoff
Call blocking rateCall blocking rate The probability that a new call is denied due The probability that a new call is denied due
to lack of available channelto lack of available channel
Usually call drop rate is more important Usually call drop rate is more important than call blocking ratethan call blocking rate
Handoff Management:Handoff Management:Channel Reservation SchemeChannel Reservation Scheme
Reserve some channels for handoff callsReserve some channels for handoff calls Trade call blocking rate for call drop rateTrade call blocking rate for call drop rate
Channel Assignment Channel Assignment ProblemProblem
Allocate channels to cellsAllocate channels to cells should considershould consider
QoS (Quality of Service)QoS (Quality of Service) co-channel interferenceco-channel interference adjacent channel interferenceadjacent channel interference
spectrum utilizationspectrum utilization
GoalGoal :: maximize both QoS and maximize both QoS and spectrum utilizationspectrum utilization
Co-Channel and Adjacent-Co-Channel and Adjacent-Channel InterferenceChannel Interference
Co-channel interferenceCo-channel interference Radio signals assigned to the same channel Radio signals assigned to the same channel
will interfere with each otherwill interfere with each other
Adjacent channel interferenceAdjacent channel interference Two frequencies of wavelength close to Two frequencies of wavelength close to
each other will interfere with each other and each other will interfere with each other and should not be assigned to neighboring cellsshould not be assigned to neighboring cells
Co-channel interferenceCo-channel interference
A
BC
D
A channel assignedto A should not beassigned to B nor Cat the same time
However, it can beassigned to D withoutco-channel interference
Classification of Channel Classification of Channel Assignment SchemesAssignment Schemes
Fixed Channel AssignmentFixed Channel Assignment Each cell is assigned a fixed subset of Each cell is assigned a fixed subset of
frequenciesfrequencies low response time with low utilizationlow response time with low utilization
Dynamic Channel AssignmentDynamic Channel Assignment Does not give any frequency to any cell a Does not give any frequency to any cell a
prioripriori high response time with high utilizationhigh response time with high utilization
A Typical Fixed Channel A Typical Fixed Channel Assignment SchemeAssignment Scheme
All channels are dividedAll channels are dividedinto 7 disjoint setsinto 7 disjoint sets
23
456
71
23
456
71
23
456
71 2
345
67
12
345
67
12
345
67
1 23
456
71
23
456
71
Generations of Cellular Generations of Cellular SystemsSystems
The first generationThe first generation AMPSAMPS Analog system, circuit-switched serviceAnalog system, circuit-switched service
The second generationThe second generation GSM, IS-136, PDC, IS-95GSM, IS-136, PDC, IS-95 Digital system, circuit-switched serviceDigital system, circuit-switched service
2.5 G2.5 G GPRSGPRS Digital system, packet-switched serviceDigital system, packet-switched service
3 G3 G IMT-2000IMT-2000 Digital system, multimedia serviceDigital system, multimedia service
Advanced Mobile Phone Advanced Mobile Phone Service (AMPS)Service (AMPS)
Analog cellular system (1983)Analog cellular system (1983) Frequency Division Multiple Access (FDMA)Frequency Division Multiple Access (FDMA) 50 channels per cell50 channels per cell
BS
MTSOLE
MS
PSTN
AMPS (1/2)AMPS (1/2)
The first cellular systemThe first cellular system Developed during 1970s in Bell Lab.Developed during 1970s in Bell Lab. 10 years to generate the AMPS specification10 years to generate the AMPS specification 1974—1978 field trial in Chicago1974—1978 field trial in Chicago Commercial service has been available since Commercial service has been available since
19831983 FDMA (Frequency Division multiple Access) / FDMA (Frequency Division multiple Access) /
FDD (Frequency Division Duplex)FDD (Frequency Division Duplex) technology technology
AMPS (2/2)AMPS (2/2)
Channel spacing: 30 KHzChannel spacing: 30 KHz Frequency bandsFrequency bands
Forward link (BS Forward link (BS MS): 869 MHz – 894 MHz MS): 869 MHz – 894 MHz Reverse link (MS Reverse link (MS BS): 824 MHz – 849 MHz BS): 824 MHz – 849 MHz Total 832 full-duplex channelsTotal 832 full-duplex channels
Roaming management standard: Roaming management standard: EIA/TIA IS-41EIA/TIA IS-41
Service area: North America, TaiwanService area: North America, Taiwan
Digital Cellular Phone Digital Cellular Phone SystemsSystemsStandard
Frequency band
Multiple access
Duplex method
No. of channels
Channel spacing
Modulation
Channel bit rate
GSM 900 GSM1800 IS-54/-136 IS-95
270.83 kb/s 270.83 kb/s 48.6 kb/s 1.2288 Mb/s
GMSK GMSK p/4 DQPSK QPSK/DQPSK
200 kHz 200 kHz 30 kHz 1250 kHz
1248 users/channel
3748 users/channel
8323 users/channel
20798 users/channel
FDD FDD FDD FDD
CDMA/FDMATDMA/FDMATDMA/FDMATDMA/FDMA
down 935-960 up 880-915
down 1805-1880 up 1710-1785
down 869-894 up 824-849
down 869-894 up 824-849
Digital Cellular Phone Digital Cellular Phone Systems (Cont.)Systems (Cont.)
System IS-54 IS-95(DS) GSM 900/1800Portable txmit powerMax/avg.
600 mW/200mW
600 mW/600 mW
1W/125 mW
Speech coding VSELP QCELP RPE-LTPSpeech rate (Kbps) 7.95 8 (var.) 13Ch. coding 1/2 rate conv. 1/2 rate fwd
1/3 rate rev.1/2 rate conv.
Frame (ms) 40 20 4.615
IS-136 DAMPS (1/2)IS-136 DAMPS (1/2)
Also referred to as digital AMPS (DAMPS), Also referred to as digital AMPS (DAMPS), American Digital Cellular (ADC), North American Digital Cellular (ADC), North American TDMA (NA-TDMA), or even TDMA.American TDMA (NA-TDMA), or even TDMA.
The successor of IS-54 (IS-54c == IS-136)The successor of IS-54 (IS-54c == IS-136) About four months to create the IS-54 About four months to create the IS-54
specifications.specifications. The same frequency spectrum as AMPS.The same frequency spectrum as AMPS. Also defined for 1850 – 1990 PCS spectrum.Also defined for 1850 – 1990 PCS spectrum.
IS-136 DAMPS (2/2)IS-136 DAMPS (2/2)
FDMA – TDMA (Time Division multiple Access) / FDD FDMA – TDMA (Time Division multiple Access) / FDD (Frequency Division Duplex) technology(Frequency Division Duplex) technology
Carrier spacing = 30kHz.Carrier spacing = 30kHz. 3 channels (time slots) per frequency carrier3 channels (time slots) per frequency carrier Speech coding rate: 7.95 kbpsSpeech coding rate: 7.95 kbps Capacity: about 3 times that of AMPSCapacity: about 3 times that of AMPS Roaming management standard: EIA/TIA IS-41Roaming management standard: EIA/TIA IS-41 Service area: North AmericaService area: North America
IS-95 cdmaOne (1/2)IS-95 cdmaOne (1/2)
Developed by QualcommDeveloped by Qualcomm Operating in US and Korea since 1996.Operating in US and Korea since 1996. DS-CDMA (Direct Sequence Code Division DS-CDMA (Direct Sequence Code Division
multiple Access) / FDD (Frequency Division multiple Access) / FDD (Frequency Division Duplex) technologyDuplex) technology
About two years to create the IS-95 specifications.About two years to create the IS-95 specifications. Frequency bandsFrequency bands
AMPS (824 – 894 MHz)AMPS (824 – 894 MHz) PCS (1850 – 1990 MHz)PCS (1850 – 1990 MHz)
IS-95 cdmaOne (2/2)IS-95 cdmaOne (2/2)
Carrier Spacing: 1.25 MHzCarrier Spacing: 1.25 MHz Capacity: 3 – 6 times than that of TDMA, 10 Capacity: 3 – 6 times than that of TDMA, 10
times than that of AMPS. (4 – 5 times than that times than that of AMPS. (4 – 5 times than that of GSM, 8 – 10 times than that of AMPS).of GSM, 8 – 10 times than that of AMPS).
Speech coding rate: 13 or 8 kbpsSpeech coding rate: 13 or 8 kbps Roaming management standard:Roaming management standard:
EIA/TIA IS-41EIA/TIA IS-41 Service area: North America, South Korea, Service area: North America, South Korea,
ChinaChina
Cordless Phone SystemsCordless Phone Systems
System CT2 CT2+ DECT PHS PACSDuplexing TDD TDD TDD FDDFrequency band(MHz)
864-868944-948
1880-1900
1895-1918
1850-1910/1930-1990
Carrier spacing(KHz)
100 1728 300 300/300
Number ofcarriers
40 10 77 16 pairs/10 MHz
Bearer channel/carrier
1 12 4 8/pair
Channel bit rate(kbps)
72 1152 384 384
Modulation GFSK GFSK /4 QPSK /4 QPSKSpeech coding 32 kbps 32 kbps 32 kbps 32 kbpsAverage handsetTX power (mW)
5 10 10 25
Peak handsetTX power (mW)
10 250 80 200
Frame duration(ms)
2 10 5 2.5
CT2CT2
Developed in EuropeDeveloped in Europe Available since 1989Available since 1989 FDMA / TDD (Time Division Duplexing) technologyFDMA / TDD (Time Division Duplexing) technology Speech coding rate: 32kbpsSpeech coding rate: 32kbps Data rate: 2.4 – 4.8 kbpsData rate: 2.4 – 4.8 kbps Max Tx power: 10mW.Max Tx power: 10mW. Do not support handoffDo not support handoff Do not support call-delivery (call-termination)Do not support call-delivery (call-termination) CT2+ supports call-deliveryCT2+ supports call-delivery
DECT (1/2)DECT (1/2)
DECT specifications were published in 1992DECT specifications were published in 1992 Pico-cell designPico-cell design Digital system; TDMA/TDD technologyDigital system; TDMA/TDD technology 12 frequency channels/frequency carrier12 frequency channels/frequency carrier Sleep mode is employed to conserve the power Sleep mode is employed to conserve the power
of MSs.of MSs. Time slot transfer: DECT may move a Time slot transfer: DECT may move a
conversation from one time slot to another to conversation from one time slot to another to avoid interferenceavoid interference
DECT (2/2)DECT (2/2)
Supports seamless handoffSupports seamless handoff Speech coding rate: 32 kbpsSpeech coding rate: 32 kbps Supports dynamic channel allocationSupports dynamic channel allocation Typically implemented as a wireless-PBX Typically implemented as a wireless-PBX
connected to the PSTNconnected to the PSTN Can interwork with GSM to allow users Can interwork with GSM to allow users
mobility, where the GSM handsets provide mobility, where the GSM handsets provide DECT connection capability.DECT connection capability.
PHS (1/2)PHS (1/2)
Developed by the Research and Development Developed by the Research and Development Center for Radio System (RCR) in JapanCenter for Radio System (RCR) in Japan
Digital systemDigital system Offer services for homes, offices (1895 – Offer services for homes, offices (1895 –
1906.1 MHz), and outdoor (1906.1– 1918.1 1906.1 MHz), and outdoor (1906.1– 1918.1 MHz) environmentsMHz) environments
TDMA / TDD technologyTDMA / TDD technology Carrier spacing: 300 kHzCarrier spacing: 300 kHz 4 time slots/frequency carrier4 time slots/frequency carrier
PHS (2/2)PHS (2/2)
Supports sleep modeSupports sleep mode Supports dynamic channel allocationSupports dynamic channel allocation PHS utilizes dedicated control channels to PHS utilizes dedicated control channels to
carry system and signaling informationcarry system and signaling information Speech coding rate: 32 kbpsSpeech coding rate: 32 kbps User mobility: up to 100 km/hrUser mobility: up to 100 km/hr Data rateData rate
Current stage: up to 64 kbps Current stage: up to 64 kbps (( 大眾電信,大眾電信, Taiwan)Taiwan) Future: 128 kbsp Future: 128 kbsp 512 kbps 512 kbps 3G 3G
PACSPACS
Developed at Telcordia (formerly Bellcore)Developed at Telcordia (formerly Bellcore) Designed for Wireless Local Loop (WLL) and PCSDesigned for Wireless Local Loop (WLL) and PCS TDMA/FDD or TDMA/TDD technologyTDMA/FDD or TDMA/TDD technology 8 voice channels/frequency carrier8 voice channels/frequency carrier Speech coding rate: 32 kbpsSpeech coding rate: 32 kbps Mobile-controlled handoff (MCHO)Mobile-controlled handoff (MCHO) Roaming management: IS-41-like protocolRoaming management: IS-41-like protocol Supports both circuit-based and packet-based access Supports both circuit-based and packet-based access
protocolprotocol User mobility: up to 38 miles/hrUser mobility: up to 38 miles/hr
Data Services in DECTData Services in DECT
DECT data link layer is designed for DECT data link layer is designed for circuit and packer mode servicescircuit and packer mode services in the packet mode, it is possible to allocate in the packet mode, it is possible to allocate
multiple time slots to SUsmultiple time slots to SUs
Mobile Data SystemsMobile Data Systems
DataTAC/Ardis: IBM, Motorola -1983DataTAC/Ardis: IBM, Motorola -1983 MobiTex/RAM: Ericsson, Bellsouth -1989MobiTex/RAM: Ericsson, Bellsouth -1989 CDPD: Open System (IBM, AT&T) -1993CDPD: Open System (IBM, AT&T) -1993 GPRS: ETSIGPRS: ETSI
Mobile Data Systems Mobile Data Systems (cont.)(cont.)
System DataTAC MobiTex CDPDFreq. Band (MHz) 800 900, 400 800Channel spacing (KHz) 12.5/25 12.5/25 30Protocol RD-LAP MPAKS TCP/IPData rate (Kbps) 4.8/19.2 8/16 19.2Throughput (Kbps) 2.2/12.0 4-5 9.6-14.4Specification Closed Closed Open
GPRS (1/2)GPRS (1/2)
GSM data servicesGSM data services Short Message Services (SMS)Short Message Services (SMS) Bearer Services: 9.6 kbps (14.4 kbps for Phase 2+, 1996) Bearer Services: 9.6 kbps (14.4 kbps for Phase 2+, 1996)
circuit-switched datacircuit-switched data High Speed Circuit-Switched Data (HSCSD): 9.6 - 115.2 kbps High Speed Circuit-Switched Data (HSCSD): 9.6 - 115.2 kbps
(Phase 2+, 1997)(Phase 2+, 1997) GPRSGPRS
GSM Phase 2 + for GPRS is completed in 1998.GSM Phase 2 + for GPRS is completed in 1998. Provides best-effort packet-switched serviceProvides best-effort packet-switched service External Network: X.25, Internet (TCP/IP)External Network: X.25, Internet (TCP/IP)
GPRS (2/2)GPRS (2/2)
Up to 8 time slots can be assigned to a single userUp to 8 time slots can be assigned to a single user Coding schemes:Coding schemes:
CS-1: 9.06CS-1: 9.06 CS-2: 13.4CS-2: 13.4 CS-3: 13.6CS-3: 13.6 CS-4: 21.4 (no channel coding)CS-4: 21.4 (no channel coding)
Data rate: (9.06, 13.4, 15.6, 21.4, depends on channel Data rate: (9.06, 13.4, 15.6, 21.4, depends on channel coding) x (1 to 8) ==> 171.2 kbps (max)coding) x (1 to 8) ==> 171.2 kbps (max)
Additional equipments are introduced in GPRSAdditional equipments are introduced in GPRS Gateway GPRS Support Node (GGSN)Gateway GPRS Support Node (GGSN) Serving GPRS Support Node (SGSN)Serving GPRS Support Node (SGSN) Packet Control Unit (PCU)Packet Control Unit (PCU)
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