Evolution from 1G to 4G Technologies ByDr. Muhammad Moinuddin
The First Mobile Generation 1G Goal: Provide basic voice service to mobile users over large area 1 G Systems developed late 70’s early 80’s, deployed in 80’s Advanced Mobile Phone System (AMPS) - USA Total Access Communications Systems (TACS) - UK Nordic Mobile Telephone (NMT) System – Scandanavian C450 - W. Germany NTT System - Nippon Telephone & Telegraph (NTT) – Japan Incompatible systems using different frequencies
Characteristics of 1G systems Use Cellular Concept to provide service to a geographic area (i.e. number of small adjacent cells to provide coverage) Frequency Reuse Handoff/Handover FDMA/FDD systems Macro Cells : 1-40 km radius Focus on AMPS system
AMPS Advanced Mobile Phone System is first generation wireless in US Earlier systems used line of sight radio (eg, AT&T’s Improved Mobile Telephone Service in 1960s) AT&T developed cellular concept in 1940s 1971 proposed High Capacity Mobile Phone Service to FCC 1979 FCC standardized it as AMPS in 800-900 MHz range 1983 launched in Chicago
AMPS (Contd.) Originally 40 MHz of spectrum separated into two bands of 20 MHz each (A and B band). Later expanded to 25 MHz each. FDD used with 45 MHz separation in uplink and downlink – prevents self interference. AMPS uses 30 kHz radio channels between mobile station and base stations Two service providers in area are each allocated 25 MHZ => 12.5 MHz for each direction => 416 pairs of channels: split into 395 voice channels + 21 control channels for signaling
AMPS (Contd.) Channels numbered consecutively 1-666 , when expanded kept same numbering assuming 30 KHz channels even in places were no spectrum allowed f(c)uplink = 825,000 + 30 x (c) KHz 1 ≤ c ≤ 799 f(c)uplink = 825,000 + 30 x (c-1023) KHz 991 ≤ c ≤ 1023 f(c)downlink = f(c)uplink + 45,000 KHz
Sectored Frequency Planningfor AMPS AMPS operators typically used either clusters of size 21 with no sectoring or clusters of 7 in cell frequency reuse pattern with 3 sectors per cell Use a Frequency Chart to plan cells: groups frequencies into 21 categories Cells 1-7 and sectors A,B,C in each cell
The Second Mobile Generation 2G The second generation (2G) of the wireless mobile network was based on low-band digital data signaling. The most popular 2G wireless technology is known as Global Systems for Mobile Communications (GSM). The first GSM systems used a 25MHz frequency spectrum in the 900MHz band.
2G Technologies Global System Mobile (GSM) Interim-Standard 136 (IS-136) or North America Digital Cellular (NADC) or US Digital Cellular (USDC) Pacific Digital Cellular (PDC) Interim-Standard 95 Code Division Multiple Access (CDMA) (IS-95 or cdmaOne)
GSM Architecture The available 25MHz of bandwidth into 124 carrier frequencies of 200 kHz each. Each frequency is then divided using a TDMA scheme into 8 timeslots and allows eight simultaneous calls on the same frequency. TDMA breaks down data transmission, such as a phone conversation, into fragments and transmits each fragment in a short burst, assigning each fragment a time slot. Today, GSM systems operate in the 900MHz and 1.8 GHz bands throughout the world with the exception of the Americas where they operate in the 1.9 GHz band.
Interim Standard-36 (IS-136) Started in 1991 Also known as North American Digital Cellular (NADC) or US Digital Cellular (USDC) Uses π/4-DQPSK, speech coding Uses TDMA with 3 time slotted users for each 30 kHz radio channel. Capacity improvement is 3 times that of AMPS and later 6 times due to advancement in DSP
Pacific Digital Cellular (PDC) A Japanese TDMA standard that is similar to IS-136 with more than 50 million users.
Interim Standard-95 (IS-95) It is a popular 2G CDMA standard. Supports up to 64 users that are orthogonally coded and simultaneously transmitted on each 1.25 MHz channel.
CDMA While GSM technology was developed in Europe, CDMA (Code Division Multiple Access) technology was developed in North America. CDMA uses spread spectrum technology to break up speech into small, digitized segments and encodes them to identify each call. CDMA distinguishes between multiple transmissions carried simultaneously on a single wireless signal.
Migration from 2G to 3GFigure 2.3 Various upgrade paths for 2G technologies.
Why 2.5G ? The Second Generation (2G) wireless networks are mostly based on circuit-switched technology which limit the data user to a single circuit switched voice channel 2G are thus, limited to data throughput rate of an individual user (approx on the order of 10kbps), 2G wireless technologies can handle some data capabilities such as fax and short message service (SMA) at the data rate of up to 9.6 kbps, but it is not suitable for web browsing, rapid email, and multimedia applications.
Features of 2.5G It allow existing 2G equipment to be modified and supplemented with new infrastructure to support high data rate transmission for Web browsing Email Mobile-Commerce (m-commerce) Location based mobile services Support Wireless Application Protocol (WAP) WAP is web browsing format language that allows standard web pages to be viewed in a compressed format
2.5G Standards So-called ‘2.5G’ systems are introduced to enhance the data capacity of GSM and mitigate some of its limitations. These systems add packet data capability to GSM networks. 2.5G standards are IS-95B, HSCSD, GPRS, EDGE technologies.
2.5G Technologies IS-95B (cdmaOne is upgraded which uses higher data rate than IS-95 and more efficient Handoff techniques) HSCSD (High Speed Circuit Switched Data) use a circuit switched technique in GSM network. Uses consecutive time slots instead of one which increases the data rate from 9,600 bps to 14,400 bps. By using 4 consecutive time slots it increases to 57.6 kbps
2.5G Technologies (Contd.) GPRS (General Packet Radio Services) is a packet based data network. Unlike HSCSD, which dedicates circuit switched channels to specific users, GPRS supports circuit switching for multi-user network sharing of individual radio channels and time slots. EDGE (Enhanced Data rate for GSM Evolution) introduces 8-PSK in addition to GSM’s standard GMSK modulation. EDGE allows for 9 different air interface formats known as multiple modulation and coding schems (MCS) with varying degree of error control protection.
GPRS vs WAP WAP defines how Web pages and similar data can be passed over limited bandwidth wireless channels to small screens being built into new mobile telephones. GPRS defines how to add IP support to the existing GSM infrastructure. Theoretical maximum speeds of up to 171.2 kilobits per second (kbps) are achievable with GPRS using all eight timeslots at the same time. This is about ten times as fast as old Circuit Switched Data services on GSM networks.
Third Mobile Generation Networks (3G) All 2G wireless systems are voice-centric. GSM includes short message service (SMS), enabling text messages of up to 160 characters to be sent. Most 2G systems also support some data over their voice paths, but at painfully slow speeds usually 9.6 Kb/s or 14.4 Kb/s.
3G Planning Planning for 3G started in the 1980s. Initial plans focused on multimedia applications such as videoconferencing for mobile phones. The First Key Issue is the evolution of Internet. It is clear that the real killer application was the Internet. Personal wireless Internet access will follow and users will want broadband Internet access wherever they go.
3G Planning The second key issue for 3G wireless is that users will want to roam worldwide and stay connected. Today, GSM leads in global roaming.
3G Planning The third issue for 3G systems is capacity. Cells can be made smaller, permitting frequency reuse, but only to a point. The next step is new technology and new bandwidth.
3G Specifications Todays 3G specifications 144 Kb/s while the user is on the move in an automobile or train 384 Kb/s for pedestrians 2 Mb/s for stationary users That is a big step up from 2G bandwidth using 8 to 13 Kb/s per channel to transport speech signals.
3G Evolution International Mobile Telecommunications-2000 (IMT-2000) is the official International Telecommunication Union name for 3G and is an initiative intended to provide wireless access to global telecommunication infrastructure through both satellite and terrestrial systems, serving fixed and mobile phone users via both public and private telephone networks.
3G Requirements Third-generation wireless also requires new infrastructure. There are two mobility infrastructures in wide use: GSM has the mobile access protocol, GSM-MAP The North American infrastructure uses the IS-41 mobility protocol. These protocol sets define the messages passed between home location registers and visitor location registers when locating a subscriber and the messages needed to deal with hand-offs as a subscriber moves from cell to cell.
3G Technologies 3GPP 3G W-CDMA (used in Universal Mobile Telecommunication Systems (UMTS)) TD-SCDMA (Time Division Synchronous CDMA) proposed by Japan. It uses infrastructure of GSM networks. It combines TDMA and TD techniques. 3GPP2 3Gcdma2000: provides evolutionary higher data rate upgrade path for users of 2G and 2.5G.
3G UMTS : W-CDMA UMTS use the radio technology called W-CDMA (Wideband Code Division Multiple Access). W-CDMA is characterized by the use of a wider band than CDMA. W-CDMA has additional advantages of Supports packet data rate up to 2 Mbps. Thus, allowing transmission of high quality data, multimedia, streaming audio, streaming video, broadcast-type of services, and many others. Increased system capacity, and communication quality by statistical multiplexing.
Wireless Local Loop (WLL) It uses Fixed Wireless Terminal (FWT) units which differ from conventional mobile terminal units operating within cellular networks such as GSM - in that a fixed wireless terminal will be limited to an almost permanent location with almost no roaming abilities. Can provide VOIP
Local Multipoint Distribution Service(LMDS) LMDS was conceived as a broadband, fixed wireless, point-to-multipoint technology for utilization in the last mile (shorter distance). Throughput capacity and reliable distance of the link depends on common radio link constraints and the modulation method used – either PSK or AM. In general deployment links of up to 5 miles (8 km) from the base station are possible, but distance is typically limited to about 1.5 miles (2.4 km) due to fade attenuation constraints. Some point-to-point systems also use the LMDS frequencies and can reach slightly farther distances due to increased antenna gain.
Future Mobile Generation Networks(4G) The new 4G framework to be established will try to accomplish new levels of user experience and multi-service capacity by, Integrating all the mobile technologies that exist GSM - Global System for Mobile Communications, GPRS - General Packet Radio Service, IMT-2000 - International Mobile Communications, Wi-Fi - Wireless Fidelity, Bluetooth etc.
4G Objectives The main objectives of 4G networks can be stated in the following properties: Ubiquity Multi-service platform Low bit cost
Ubiquity Ubiquity means that this new mobile network must be available to the user, any time, anywhere. To accomplish this objective services and technologies must be standardized in a worldwide scale. Furthermore the services to be implemented should be available not only to humans as have been the rule in previous systems, but also to everything that needs to communicate.
Multi-Service Platform A multi-service platform is an essential property of the new mobile generation, not only because it is the main reason for user transition, but also because it will give telecommunication operators access to new levels of traffic. Voice will loose its weight in the overall user bill with the raise of more and more data services.
Low-Bit Cost Low-bit cost is an essential requirement in a scenario where high volumes of data are being transmitted over the mobile network.
Key 4G technologies Orthogonal Frequency Division Multiplexing (OFDM) Software Defined Radio (SDR) Multiple-input multiple-output (MIMO)
What is 4G? Fourth Generation Technology Faster and more reliable 100 Mb/s (802.11g wireless = 54Mb/s, 3G = 2Mb/s) Lower cost than previous generations Multi-standard wireless system Bluetooth, Wired, Wireless (802.11x)
What is 4G? Ad Hoc Networking IPv6 Core OFDM used instead of CDMA Potentially IEEE standard 802.11n Most information is proprietary
Communications Architecture Broadcast layer: fix access points, (i.e. cell tower) connected by fiber, microwave, or satellite (ISP) Ad-hoc/hot-spot layer:wireless LANs (ie. internet at Starbuck’s). Personal Layer Gateway:devices that connect to upper layers; cell phone, fax, voice, data modem, MP3 players, PDAs. Info-Sensor layer:environmental sensors. Fiber-optic wire layer: high speed subterranean labyrinth of fiber optic cables and repeaters
Ad Hoc/Mesh Networks Spontaneous self organization of networks of devices Not necessarily connected to internet 4G will create hybrid wireless networks using Ad Hoc networks. Form of mesh networking–Very reliable
Smart Antennas Beam radio signals directly at a user to follow the user as they move Allow the same radio frequency to be used for other users without worry of interference Can’t keep up transmission speeds while device is moving fast (i.e. in a car) Only 32Mb/s at 62mph (vs100Mb/s) Seamless handoff between towers/access points One transmit antenna, two receive antennas Allows connection to two access points at once
OFDM Orthogonal Frequency Division Multiplexing Allows for transfer of more data than other forms of multiplexing (time, frequency, code, etc) Simplifies the design of the transmitter & receiver Allows for use of almost the entire frequency band No gaps to prevent interference needed Currently used in WiMax(802.16) and Wi- Fi(802.11a/g)
How OFDM works The frequencies are spaced so that the signals do not interfere with each other (no cross talk) Parallel Data Transmission -Allows for the sending of multiple signals simultaneously from the same antenna (or wire) to one device.