Chapters 1-21 Introduction to Wireless Communication Systems

Transcription

1 Chapters 1-21 Introduction to Wireless Communication Systems Yimin Zhang, Ph.D. Department of Electrical & Computer Engineering Villanova University Yimin Zhang, Villanova University 1

2 Outlines History Examples of Mobile Radio Systems Cordless Phone / Paging System / Cellular System Cellular Process To a mobile user / From a mobile user Roaming 2G, 2.5G, 3G Technologies Frequency Spectrum Allocations Yimin Zhang, Villanova University 2

3 A little History and Evolution of Mobile Radio 1897: Marconi invented wireless concept 1960 s & 1970 s: Bell laboratories developed the cellular concept 1970 s: Development of highly reliable, miniature solid state radio frequency hardware Wireless communication era was born Yimin Zhang, Villanova University 3

4 Wireless Communications Cellular phone users , million million Number of wireless users = Number of wired users Yimin Zhang, Villanova University 4

5 Worldwide Cellular Telephone Subscribers Yimin Zhang, Villanova University 5

6 The first portable units were really big and heavy. Yimin Zhang, Villanova University 6

7 Cellular Technologies Analog Cellular Technologies AMPS Advanced Mobile Phone System. Developed by Bell Labs in the 1970s and first used commercially in the United States in It operates in the 800 and 1900 MHz band in the United States and is the most widely distributed analog cellular standard. Digital Cellular Technologies D-AMPS (IS-54, now rolled into IS-136) Digital AMPS. Designed to use existing channels more efficiently, D-AMPS (IS-136) employs the same 30 khz channel spacing and frequency bands ( and MHz) as AMPS. By using TDMA instead of frequency division multiple access or FDMA, IS-136 increases the number of users from 1 to 3 per channel. An AMPS/D-AMPS infrastructure can support either Analog AMPS phone or digital AMPS phones. (The Federal Communications Commission mandated that digital cellular in the U.S. must act in a dual-mode capacity with analog). Operates in the 800 MHz band and 1900 MHz. Yimin Zhang, Villanova University 7

8 Cellular Technologies Digital Cellular Technologies GSM PCS Global System for Mobile Communications. The first European digital standard, developed to establish cellular compatibility throughout Europe. Its success has spread to all parts of the world and over 80 GSM networks are now operational. It operates at 900 and 1800 MHz in many parts of Europe and in England. Works at 1900 MHz in some parts of the United States. TDMA based. Personal Communications Service. The PCS frequency band in America is 1850 to 1990 MHz, encompassing a wide range of new digital cellular standards like N-CDMA and GSM Single-band GSM 900 phones cannot be used on PCS networks. PCS networks operate throughout the USA. Yimin Zhang, Villanova University 8

9 Cellular Technologies Digital Cellular Technologies CDMA cdmaone Code Division Multiple Access. Developed by Qualcomm characterized by high capacity and small cell radius. It uses the same frequency bands as AMPS and supports AMPS operation, employing spread-spectrum technology and a special coding scheme. It was adopted by the Telecommunications Industry Association (TIA) in Wide ranging wireless specification involving IS 95, IS-96, IS-98, IS-99, IS- 634 and IS-41.AT&T, Motorola, Lucent, ALPS, GSIC, Prime Co, Qualcomm, Samsung, Sony, US West, Sprint, Bell Atlantic, Time Warner are sponsors. Yimin Zhang, Villanova University 9

10 North America Goes to Digital: IS-54 In 1990 North American carriers faced the question -- how do we increase capacity? -- do we pick an analog or digital method? The answer was digital. In March 1990 the North American cellular network incorporated the IS-54B standard, the first North American dual mode digital cellular standard. This standard won over Motorola's Narrowband AMPS or NAMPS, an analog scheme that increased capacity by cutting down voice channels from 30KHz to 10KHz. IS- 54 on the other hand increased capacity by digital means: sampling, digitizing, and then multiplexing conversations, a technique called TDMA. This method separates calls by time, placing parts of individual conversations on the same frequency, one after the next. It tripled call capacity. Using IS-54, a cellular carrier could convert any of its systems' analog voice channels to digital. A dual mode phone uses digital channels where available and defaults to regular AMPS where they are not. IS-54 was, in fact, backward compatible with analog cellular and indeed happily co-exists on the same radio channels as AMPS. No analog customers were left behind; they simply couldn't access IS-54's new features. CANTEL got IS-54 going in Canada in IS-54 also supported authentication, a help in preventing fraud. IS-54, now rolled into IS-136, accounts for perhaps half of the cellular radio accounts in this country. Yimin Zhang, Villanova University 10

11 The Rise of GSM Europeans saw things differently. No new telephone system could accommodate their existing services on so many frequencies. They decided instead to start a new technology in a new radio band. Cellular structured but fully digital, the new service would incorporate the best thinking of the time. They patterned their new wireless standard after landline requirements for ISDN, hoping to make a wireless counterpart to it. The new service was called GSM. GSM first stood for Groupe Speciale Mobile, after the study group that created the standard. It's now known as Global System for Mobile Communications, although the "C" isn't included in the abbreviation. Yimin Zhang, Villanova University 11

12 Key Specifications of 2G Technologies Yimin Zhang, Villanova University 12

13 Upgrade Paths Yimin Zhang, Villanova University 13

14 2.5G and 3G Data Communication Standards Yimin Zhang, Villanova University 14

15 Examples of Mobile Radio Systems Garage door openers Remote controllers for home entertainment Cordless telephones Hand-held walkie-talkies Pagers/beepers Cellular telephones Yimin Zhang, Villanova University 15

16 Mobile Communication Systems - Mobile Station Service Coverage range Required infrastructure Functionality Complexity Hardware cost Carrier frequency TV remote control infra-red transmitter Garage door opener <100 MHz transmitter Paging system high high <1 GHz receiver Cordless phone moderate <100 MHz transceiver Cellular phone high high high moderate <1 GHz transceiver Yimin Zhang, Villanova University 16

17 Mobile Communication Systems - Base Station Service Coverage range Required infrastructure Functionality Complexity Hardware cost Carrier frequency TV remote control infra-red receiver Garage door opener <100 MHz receiver Paging system high high high high <1 GHz transmitter Cordless phone moderate <100 MHz transceiver Cellular phone high high high high <1 GHz transceiver Yimin Zhang, Villanova University 17

18 ... Examples of Mobile Radio Systems Mobile Describes a radio terminal attached to a high speed mobile platform (e.g., A cellular phone in a fast moving vehicle). Portable Describes a radio terminal that can be hand-held and used by someone at walking speed (e.g., cordless telephone). Subscriber Mobile or portable user. Base stations Link mobiles through a backbone network. Yimin Zhang, Villanova University 18

19 Types of Mobile Radio Transmission Systems Simplex Communication is possible only in one direction, (e.g., paging systems). Half Duplex Two way communication, but uses the same radio channel for both transmission and reception. User can only transmit or receive information. Full Duplex Simultaneous two-way radio transmission and reception between subscriber and base station. Two simultaneous but separate channels (FDD) or Adjacent timeslots on a single radio channel (TDD) Yimin Zhang, Villanova University 19

20 Cordless Telephone Systems Full duplex communication Few hundred meters Public Switched Telephone Network (PSTN) Fixed Port (Base Station) wireless link cordless handset Yimin Zhang, Villanova University 20

21 Paging Systems Paging systems are communication systems that send brief messages to a subscriber... Numeric messages Alpha-numeric message Voice message News headlines Stock quotes Faxes Paging System Coverage Areas 2 to 5 km Within individual buildings Worldwide coverage Yimin Zhang, Villanova University 21

22 Paging System: Wide Area System The paging control center dispatches pages received from the Public Switched Telephone Network (PSTN) throughout several cities at the same time. PSTN Paging control center Landline link Landline link City 1: Paging terminal City 2: Paging terminal Satellite link City N: Paging terminal Yimin Zhang, Villanova University 22

23 Cellular System Base stations (towers) provide radio access between mobile users and Mobile Switching Center (MSC). Mobile Switching Center PSTN Yimin Zhang, Villanova University 23

24 Base Station - Mobile Network RCC RVC FVC FCC Forward Voice Channel Reverse Voice Channel Forward Control Channel Reverse Control Channel Yimin Zhang, Villanova University 24

25 Functions of Cellular System Provides wireless connection to the PSTN for any user location within the radio range of the system. High capacity is achieved: by limiting the coverage of each base station transmitter to a small geographical area called a Cell, and by the same radio channels being reused by another base station located some distance away Frequency reuse. Switching system, called handoff, enables call to proceed uninterrupted when the user moves from one cell to another. Typical MSC handles 100,000 cellular users and 5,000 simultaneous conversations at a time. Yimin Zhang, Villanova University 25

26 Telephone Call Made To Mobile User Incoming Telephone Call to Mobile X Base Stations PSTN 2, 6 Step 1 Mobile Switching Center 5 4 3, 7 Mobile X Yimin Zhang, Villanova University 26

27 Brief Outline of Cellular Process: Telephone Call Placed to a Mobile User Yimin Zhang, Villanova University 27

28 Brief Outline of Cellular Process: Telephone Call Placed to a Mobile User Step 1 The incoming telephone call to Mobile X is received at the MSC. Step 2 The MSC dispatches the request to all base stations in the cellular system. Step 3 The base stations broadcast the Mobile Identification Number (MIN), telephone number of Mobile X, as a paging message over the FCC throughout the cellular system. Step 4 The mobile receives the paging message sent by the base station it monitors and responds by identifying itself over the reverse control channel. Step 5 The base station relays the acknowledgement sent by the mobile and informs the MSC of the handshake. Step 6 The MSC instructs the base station to move the call to an issued voice channel within in the cell. Yimin Zhang, Villanova University 28

29 Brief Outline of Cellular Process: Telephone Call Placed to a Mobile User Step 7 The base station signals the mobile to change frequencies to an unused forward and reverse voice channel pair. At the point another data message (alert) is transmitted over the forward voice channel to instruct the mobile to ring. Now the call is in progress. The MSC adjusts the transmitted power of the mobile and changes the channel of the mobile end and base stations in order to maintain call quality. Yimin Zhang, Villanova University 29

30 Telephone Call Placed by Mobile Mobile Switching Center 3 2 PSTN 1 Telephone Call Placed by Mobile X Yimin Zhang, Villanova University 30

31 Telephone Call Placed by Mobile Yimin Zhang, Villanova University 31

32 Telephone Call Placed by Mobile Step 1 When a mobile originates a call, it sends the base station its telephone number (MIN), electronic serial number (ESN), and telephone number of called party. It also transmits a station class mark (SCM) which indicates what the maximum power level is for the particular user. Step 2 The cell base station receives the data and sends it to the MSC. Step 3 The MSC validates the request, makes connection to the called party through the PSTN and validates the base station and mobile user to move to an unused forward and reverse channel pair to al the conversation to begin. Yimin Zhang, Villanova University 32

33 Roaming All cellular systems provide a service called roaming. This als subscribers to operate in service areas other than the one from which service is subscribed. When a mobile enters a city or geographic area that is different from its home service area, it is registered as a roamer in the new service area. Periodically, the MSC issues a global command over each FCC in the system, asking for all mobiles which are previously unregistered to report their MIN and ESN over the RCC for billing purposes. If a particular mobile user has roaming authorization for billing purposes, MSC registers the subscriber as a valid roamer. Yimin Zhang, Villanova University 33

34 Frequency Spectrum for US Cellular Radio Service Channel Number Center Frequency (MHZ) 1 N N N (N 1023) N N N (N 1023) Channels are unused. Yimin Zhang, Villanova University 34

35 Yimin Zhang, Villanova University 35

36 Outlines History Examples of Mobile Radio Systems Cordless Phone / Paging System / Cellular System Cellular Process To a mobile user / From a mobile user Roaming 2G, 2.5G, 3G Technologies Frequency Spectrum Allocations Yimin Zhang, Villanova University 36