Introduction 1 Reference [1] Wireless and Mobile Network Architectures，Yi-Bing Lin and Imrich Chlamtac，Wiley Computer Publishing。 [2] Introduction to GSM，陳俊宏，遠傳教育訓練 中心。 [3] GPRS and 3G Wireless Applications， Christoffer Andersson，Wiley Computer Publishing。 2 Outline ¾ Introduction ¾ PCS Architecture ¾ Cellular Telephony ¾ Cordless Telephony and Low-Tier PCS ¾ Third-Generation Wireless Systems ¾ Summary 3 Introduction 4 PCS ¾ Personal Communications Services (PCS) refers to a wide variety of wireless access and personal mobility services. ¾ PCS systems can connected to Public Switched Telephone Network (PSTN). ¾ Goal of PCS：enabling communications with a person at anytime, at any place and in any terminal form. 5 PCS Revolution First Generation Second Generation Third Generation JTACS Mobile Satellite JDC High-tier TACS Digit GSM GSM+,++ Cellar NMT Systems IMT-2000 AMPS NADC PCS Low-tier PHS Telecommunication PACS Systems CT0/1 CT2 DECT 6 Examples of Wireless Communications Systems (1/4) ¾ High-tier digital cellular systems ¾ For vehicular and pedestrian services • Global System for Mobile Communication (GSM), Digital Communication System-1800 (DCS1800) • IS-136 TDMA based Digital Advanced Mobile Phone Service (DAMPS) • Personal Digital Cellular (PDC) • IS-95 CDMA-based cdmaOne System 7 Examples of Wireless Communications Systems (2/4) ¾ Low-tier telecommunication systems ¾ For residential, business, and public cordless access applications • Cordless Telephone 2 (CT2) • Digital European Cordless Telephone (DECT) • Personal Access Communications Systems (PACS) • Personal Handy Phone System (PHS) 8 Examples of Wireless Communications Systems (3/4) ¾ Wideband wireless systems ¾ To accommodate Internet and multimedia services. • cdma2000 (evolved from cdmaOne) • W-CDMA (proposed by Europe) • TD-SCDMA (proposed by China/Europe) 9 Examples of Wireless Communications Systems (4/4) ¾ PCS umbrella • Paging systems • Trunking Radio • Mobile-satellite system • Unlicensed industrial, scientific, and medical （ISM）band technologies, as well as wireless local area networks（WLANs） 10 PCS Architecture 11 PSTN ¾ Public Switched Telephone Network Switch Taichung subscriber loop Switch trunk Switch Taipei 12 PLMN ¾ Public Land Mobile Network PLMN PSTN 13 The Basic PCS Architecture Mobility Wireline Transport Network Public Land Database Mobile Network Switch for Mobile Applications Base Station Controller Base Transceiver Station BTS Radio Network Mobile Station 14 PCS Architecture ¾ Each PCS technology has similar architectures which consists two parts： •Radio Network 9MS (Mobile Station) 9BS (Base Station) System • Wireline Transport Network 9MSC (Mobile Switching Center) 9The Mobility Database connected to MSC is used to track the locations of mobile station. 15 Mobile Station (MS) ¾ Handset, mobile phone, subscriber unit, portable ¾ Multi-mode handset 16 Base Station (BS) ¾ The radio coverage of a BS is called a Cell. ¾ The BS system is partitioned into • a controller • radio transmitters/receivers ¾ The BSs usually reach the wireline core network via land links or dedicated microwave 17 links. GSM Antenna 18 GSM Base Station 19 Cellular Concept cluster √ √ √ cell sector √ √ √ 20 Duplex Technologies ¾ Down-link: BS to handset ¾ Up-link: handset to BS ¾ Two duplex Technologies: •FDD（Frequency Division Duplex） •TDD（Time Division Duplex） 21 FDD Frequency A1 talks to A2 B1 talks to B2 Down Link C1 talks to C2 A2 talks to A1 Up B2 talks to B1 Link C2 talks to C1 Time 22 TDD Frequency A2 B2 C2 A1 B1 C1 talks talks talks talks talks talks to to to to to to A1 B1 C1 A2 B2 C2 ..... ..... Time 23 Multiple Access Technology ¾ FDMA（Frequency Division Multiple Access） ¾ TDMA（Time Division Multiple Access） ¾ CDMA（Code Division Multiple Access） 24 FDMA Frequency 30kHz for AMPS Time 25 TDMA Frequency 200kHz for GSM Time 4.615 ms/frame 8 time slots for GSM 26 CDMA (1/2) Frequency 1.25MHz for IS-95 20 ms/frame 32 channels 27 CDMA (2/2) ¾ Code Division Multiple Access (CDMA) • Direct Sequence Spread Spectrum (DSSS) • Frequency Hopping Spread Spectrum (FHSS) ¾ In DS-CDMA, every signal is processed with PN sequence (pseudo-noise sequence). • Faster-rate, wide-bandwidth digital signal • Each PN sequence is a unique orthogonal code. • User signals are distinguished by different PN sequences. 28 Example of PN (1/3) ¾ Assign PN code A: 00011011, B: 00101110, C: 01011100, D: 01000010 ¾ Transfer the PN to Bipolar chip sequences: • A=(-1,-1,-1,1,1,-1,1,1) B=(-1,-1,1,-1,1,1,1,-1) • C=(-1,1,-1,1,1,1,-1,-1) D=(-1,1,-1,-1,-1,-1,1,-1) ¾ Check: • A*A=1+1+1+1+1+1+1+1=8 • A*B=1+1-1-1+1-1+1-1=0 • A*C=1-1+1+1+1-1-1-1=0 • A*D=1-1+1-1-1+1+1-1=0 29 Example of PN (2/3) ¾ If 4 MSs want to receive A=1, B=1, C=1, D=1, then BS will send • S1=A*1+B*1+C*1+D*1=(-4,0,-2,0,2,0,2,-2) ¾ If 4 MSs want to receive A=1, B=1, C=0, D=1, then BS will send • S2 =A*1+B*1+C*(-1)+D*1 =(-2,-2,0,-2,0,-2,4,0) 30 Example of PN (3/3) ¾ MS C will receive •1/8* C*S1 = 1/8 * (-4,0,-2,0,2,0,2,-2) * (-1,1,-1,1, 1,1,-1,-1) = 1/8 * (4+0+2+0+2+0-2+2)= 1 • 1/8 * C*S2 = 1/8 * (-2,-2,0,-2,0,-2,4,0) * (-1,1,-1,1, 1,1,-1,-1) = 1/8 * (2-2+0-2+0-2-4+0)= -1 9-1 means “0” ¾ MS A will receive • A*S1=A*(A*1+B*1+C*1+D*1)=A*A*1+A*B*1+A*C*1 31 +A*D*1=8*1+0+0+0=8 Spread Spectrum Correlation Process Recovered Data Signal Received Signal + Wideband Interference Data Signal W Hz Direct Sequence Direct Sequence Spread Despread 0 f 0 f 0 f : Desired Signal : Interference 32 Cellular Telephony 33 1G Cellular Telephony ¾ Advanced Mobile Phone Service (AMPS) ¾ Total Access Communication System (TACS) ¾ NMT (Nordic Mobile Telephone) 450/900 ¾ NTT (Nippon Telephone & Telegraph) , JTACS (1988), NTACS (1993) ¾ C450 34 Advanced Mobile Phone Service (AMPS) (1/2) ¾ Analog FM radio for voice transmission ¾ FSK modulation for signal channels ¾ FDMA ¾ FDD ¾ Total 50 MHz=824-849 MHz(down-link) + 869-894 MHz(up-link) • 832 full-duplex channels using 1664 discrete frequencies ¾ 30kMHz spacing 35 Advanced Mobile Phone Service (AMPS) (2/2) ¾ Frequency reuse scheme for radio communication • 12-cell cluster using omni-directional antennas • 7-cell cluster using three sectors per BS • 4-cell cluster, 6-sector design in Motorola AMPS system. There are about 50 channels per cell. ¾ EIA/TIA IS-41 standard for roaming management. 36 2G Cellular Telephony ¾ Global System for Mobile Communications (GSM) ¾ EIA/TIA IS-136 Digital Cellular System ¾ EIA/TIA IS-95 Digital Cellular System ¾ Japanese Digital Cellular (JDC) in Japan 37 Global System for Mobile Communications (GSM) (1/2) ¾ “Digital” cellular system • Groupe Special Mobile of Conference Europeenne des Posts et Telecommunications (CEPT) and European des Postes et Telecommunications (ETSI) ¾ TDMA/FDD ¾ 935-960 MHz for Downlink ¾ 890-915 MHz for Uplink ¾ 200 kHz for RF channel spacing ¾ Speech coding rate 13 Kbps 38 Global System for Mobile Communication (GSM) (2/2) ¾ Frequency carrier is divided into 8 time slots • Every pair of radio transceiver-receiver supports 8 voice channels. ¾ GSM Mobile Application Part (MAP) for roaming management ¾ Digital switch can provide many applications: • Example: point-to-point short messaging, group addressing, call waiting, multiparty services 39 EIA/TIA IS-136 Digital Cellular System (1/2) ¾ Digital AMPS (DAMPS), American Digital Cellular (ADC), or North American TDMA (NA-TDMA), IS-136 ¾ The successor to IS-54 ¾ The same spectrum used by AMPS • 3 times of capacity of AMPS ¾ TDMA/FDD ¾ 30 KHz frequency spacing 40 EIA/TIA IS-136 Digital Cellular System (2/2) ¾ 2 types of channel usage: • Full-rate: use 2 timeslot for a voice channel • Half-rate: use 1 timeslot for a voice channel ¾ Digital switch can provide many applications: • Example: point-to-point short messaging, broadcast messaging, group addressing, private user groups ¾ IS-41 standard for mobility management 41 EIA/TIA IS-95 Digital Cellular System (1/2) ¾ Qualcomm cdmaOne in USA since 1996 ¾ Korea in April, 1996. PLMN Vocoder Switch PSTN 42 EIA/TIA IS-95 Digital Cellular System (2/2) ¾ CDMA/DSSS for the air interface. • A shared 1.25 MHz channel bandwidth • User signals distinguished with different codes • MSs links to many BSs during phone calls. • No cell plan question • GPS for synchronization of BSs ¾ Interference-based capacity (soft capacity) • The capacity of IS-95 is 3-6 times of IS-136 system, and 10 times of AMPS. ¾ IS-41 for core network ¾ Advanced Radio Resource Management 43 Comparison of Cellular Systems System AMPS GSM IS-136 IS-95 JDC DCS1800 Region 美 歐,台灣 美 美,韓,中國 日 Duplex FDD FDD FDD FDD FDD MAC FDMA FDMA FDMA FDMA FDMA TDMA TDMA CDMA TDMA Downlink 870-890 935-960 869-894 869-894 810-826 (MHz) 1805-1880 Uplink (MHz) 825-845 890-915 824-849 824-849 940-956 1710-1785 Carrier 30kHz 200kHz 30kHz 1.25MHz 25kHz Channels 1 8 6 32 3 Speech rate 10 kps 13 kps 7.95kps 8 kps 11.2 kps Channel bit 270.833 kps 48.6 kps 1228.8 kps 42 kps rate 44 Cellular Characteristics ¾ The characteristics of the cellular system: • Support high mobility • Large coverage area • High transmission power of BS and handset • High signal process power (for handset) • Low voice quality • High network complexity ¾ Microcell is developed for: • Low transmission power • Low base station cost 45 • Increase capacity Low-Tier PCS 46 Examples of Low-Tier PCS ¾ Cordless Telephone, Second Generation (CT2) ¾ Digital European Cordless Telephone (DECT) ¾ Personal Handy Phone System (PHS) ¾ Personal Access Communications System (PACS) 47 Cordless Telephone, Second Generation (CT2) (1/2) ¾ Developed in Europe CT-1 since 1989.