5.15: Early Generations of Radio

5.8.1 1G, First Generation: Analog Radio

The initial cellular radio system was analog, with the dominant system being AMPS, the attributes of which are given in Table \(\PageIndex{2}\). This is a relatively simple system, but appropriate for the low levels of integration of the 1980s, as most of the functionality could be realized using analog circuits. The first

System	Year	Description
0G		Broadcast, no cells, few users, analog modulation
MTS	1946	Mobile telephone service, halfduplex, operator assist to establish call, push to talk
AMTS	1965	Advanced mobile telephone system, Japan, duplex, \(900\text{ MHz}\)
IMTS	1969	Improved mobile telephone service, duplex, up to \(13\) channels, \(60–100\text{ km}\) (\(40–60\text{ mile}\)) radius, direct dial using dual-tone multifrequency (DTMF) keypad
0.5G		FDMA, analog modulation
PALM	1971	(also Autotel) Public automated land mobile radiotelephone service, used digital signaling for supervisory messages, technology link between IMTS and AMPS
ARP	1971	Autoradiopuhelin (car radio phone), obsolete in \(2000\), used cells (\(30\text{ km}\) radius) but not hand-off, \(80\) channels at \(150\text{ MHz}\), simplex and later duplex
1G		Analog modulation, FSK for signaling, cellular, FDMA
NMT	1981	Nordic mobile telephone, \(12.5\text{ kHz}\) channel, \(450\text{ MHz},\: 900\text{ MHz}\)
AMPS	1983	Advanced mobile phone system, \(30\text{ kHz}\) channel
TACS	1985	Total access communication systems, \(25\text{ kHz}\) channel, widely used in Europe until 1990s, similar to AMPS
Hicap	1988	NTT’s mobile radiotelephone service in Japan
Mobitex	1990	National public access wireless data network, first public access wireless data communication services including two-way paging network services, \(12.5\text{ kHz}\) channel, GMSK
DataTac	1990	Point-to-point wireless data communications standard (like Mobitex), wireless wide area network, \(25\text{ kHz}\) channels, maximum bandwidth \(19.2\text{ kbit/s}\) (used by the original Blackberry device)
2G		Digital modulation
PHS	1990	Personal handyphone system, originally a cordless phone, now functions as both a cordless phone and as a mobile phone elsewhere
GSM	1991	Global system for mobile communications (formerly Groupe Special Mobile), TDMA, GMSK, constant envelope, \(200\text{ kHz}\) channel, maximum \(13.4\text{ kbits}\) per time slot (at \(1900\text{ MHz}\)), \(2\) billion customers in \(210\) countries
DAMPS	1991	Digital AMPS (formerly NADC [North American digital cellular] and prior to that as U.S. Digital Cellular [USDC]), narrowband, \(π/4\)DQPSK, \(30\text{ kHz}\) channel
PDC	1992	Personal Digital Cellular, Japan, \(25\text{ kHz}\) channel
CDMAOne	1995	Brand name of first CDMA system known as IS-95, spread spectrum, CDMA, \(1.25\text{ MHz}\) channel, QPSK
CSD	1997	Circuit switched data, original data transmission format developed for GSM, maximum bandwidth \(9.6\text{ kbit/s}\), used a single time slot
2.5G		Higher data rates
WiDEN	1996	Wideband integrated dispatch enhanced network, combines four \(25\text{ kHz}\) channels, maximum bandwidth \(100\text{ kbit/s}\)
GPRS	2000	General packet radio system, compatible with GSM network, used GSM time slot and higher-order modulation to send \(60\text{ kbits}\) per time slot, \(200\text{ kHz}\) channel, maximum bandwidth \(171.2\text{ kbit/s}\)
HSCSD	2000	High-speed circuit-switched data, compatible with GSM network, maximum bandwidth \(57.6\text{ kbit/s}\), higher quality of service than GPRS
2.75G		Medium bandwidth data—\(1\text{ Mbit/s}\)
CDMA2000	2000	CDMA, upgraded CDMAOne, double data rate, \(1.25\text{ MHz}\) channel
EDGE	2003	Enhanced data rate for GSM Evolution, compatible with GSM network, 8-PSK, TDMA, maximum bandwidth \(384\text{ kbit/s},\: 200\text{ kHz}\) channel
3G		Spread spectrum
FOMA	2001	Freedom of mobile multimedia access, first 3G service, NTT’s implementation of WCDMA
UMTS		Universal mobile telephone service, \(5\text{ MHz}\) channel, data up to \(2\text{ Mbit/s}\)
WCDMA	2004	Main 3G outside China
OFDMA	2007	Evolution to 4G (downlink high bandwidth data)
1xEV-DO		(IS-856) Evolution of CDMA2000, maximum downlink bandwidth \(307\text{ kbit/s}\), maximum uplink bandwidth \(153\text{ kbit/s}\)
TD-SCDMA	2006	Time division synchronous CDMA, China, uses the same band for transmit and receive, basestations and mobiles use different time slots to communicate, \(1.6\text{ MHz}\) channel
GAN/UMA	2006	Generic access network, formerly known as Unlicensed Mobile Access, provides GSM and GPRS mobile services over unlicensed spectrum technologies (e.g., Bluetooth and WiFi)
3.5G
UMTS/HSDPA	2006	Upgraded WCDMA, High-speed downlink packet access, download of \(7.2\text{ Mbit/s}\)
EV-DO Rev A	2006	CDMA2000 EV-DO revision A, downlink to \(3.1\text{ Mbit/s}\), uplink to \(1.8\text{ Mbit/s}\)
3.75G
UMTS/HSUPA	2007	High-speed uplink packet access, upload speeds to \(5.76\text{ Mbit/s}\)
EV-DO Rev B	2008	CDMA2000 EV-DO revision B, downlink to \(73\text{ Mbit/s}\), uplink to \(27\text{ Mbit/s}\)
UMTS/HSPA	2009	Upgraded WCDMA, High-speed packet access, downlink to \(40\text{ Mbit/s}\), upload to \(10\text{ Mbit/s}\). Eventually added CA and MIMO
3.9G	2009	WiMAX 1 (IEEE 802.16), \(10\text{ MHz}\) bandwidth; IP-based; branded as 4G by service providers; MIMO + OFDMA, downlink of \(37\text{ Mbit/s}\), uplink \(17\text{ Mbit/s}\) (for \(2\times 2\) MIMO); WiMAX 2, IEEE \(802.16\text{ m}\), \(20\text{ MHz}\) bandwidth, downlink of \(110\text{ Mbit/s}\), uplink \(70\text{ Mbit/s}\); not allowed in many countries
3.9G	2011	Long-term evolution (LTE); up to \(20\text{ MHz}\) channel bandwidth, IP-based; branded as 4G by service providers Low latency (for VoIP) + MIMO + OFDMA, downlink of \(100\text{ Mbit/s}\)
4G	2013	LTE-advanced, downlink of \(1\text{ Gbit/s}\) fixed, \(100\text{ Mbit/s}\) mobile, variable bandwidths of \(5–40\text{ MHz}\)
5G	2019	Millimeter waves with beam steering and massive MIMO; Mesh networks and cognitive radio

Table \(\PageIndex{1}\): Major mobile communication systems with the year of first widespread use.

Property	Attribute
Number of physical channels	\(832;\: 2\) groups of \(416\) channels, each group has \(21\) signaling channels and \(395\) traffic or voice channels
Bandwidth per channel	\(30\text{ kHz}\)
Cell radius	\(2-20\text{ km}\)
Base-to-mobile frequency	\(869–894\text{ MHz}\) (downlink)
Mobile-to-base frequency	\(824–849\text{ MHz}\) (uplink) \(45\text{ MHz}\) between transmit and receive channels
Channel spacing	\(30\text{ kHz}\)
Modulation	FM with peak frequency deviation of \(±12\text{ kHz}\) Signaling channel uses FSK Can send data at \(10\text{ kbit/s}\)
Access method	FDMA
Basestation ERP	\(100\text{ W}\) per channel (maximum)
Channel coding	None
RF Specifications of Mobile Unit
Transmit RF power	\(3\text{ W}\) maximum (\(33\text{ dBm}\)) (\(600\text{ mW}\) for hand-held)
Transmit power control	\(10\) steps of \(4\text{ dB}\) attenuation each, minimum power is \(−4\text{ dBm}\)
Receive sensitivity	\(-116\text{ dBm}\)
Receive noise figure	\(6\text{ dB}\) measured at antenna terminals
Receive spurious response	\(−60\text{ dB}\) from center of the passband

Table \(\PageIndex{2}\): Attributes of AMPS

generation systems handled analog \(3\text{ kHz}\) voice transmissions with very limited ability to transmit digital information limited to signaling.

5.8.2 2G, Second Generation: Digital Radio

The second generation (2G) of cellular radio is characterized by digitization. Many different types of 2G digital systems were installed around the world. The 2G systems can transmit data and voice at rates of \(8–14.4\text{ kbit/s}\). This can be contrasted to the wireline phone system where, once signals reach the exchange, the \(3\text{ kHz}\) analog signals are sampled at \(64\text{ kbit/s}\) to achieve an undistorted signal representation. These cellular systems sacrifice some voice quality but use reasonably sophisticated algorithms that use the characteristics of speech to achieve greater than a factor of four compression.

In North America the first digital system introduced was the digital advanced mobile phone system (DAMPS) (originally known as North American Digital Cellular [NADC] and as the EIA/TIA interim standard IS-54). The system was designed to provide a transition from the then current 1G analog system to a fully digital system by reusing existing spectrum. The idea was that system providers could allocate a few of their channels for digital radio out of the total available. As analog radio was phased out, more of the channels could be committed to digital radio. The main motivation behind this system is that it provided three to five times the capacity of the analog system for the same bandwidth. The 2G GSM system provides a similar increase in capacity, and is compatible with the Integrated Services Digital Network (ISDN) which was the protocol used with the wired telephone system. The GSM system was initially (early 1990s) dominant in Europe and had the advantage that it did not need to coexist

Property	Attribute
Number of channels	\(125\) (for GSM-900)
Bandwidth per channel	\(200\text{ kHz}\)
Channel spacing	\(200\text{ kHz}\)
Cell radius	\(2-20\text{ km}\)
Base-to-mobile frequency	\(935–960\text{ MHz}\) (GSM-900)
Mobile-to-base frequency	\(890–915\text{ MHz}\) (GSM-900)
Modulation	GMSK, Slow frequency hopping (\(217\text{ hops/s}\))
Access method	TDMA, \(8\) slots per frame, user has one slot, each frame is \(4.615\text{ ms}\) and each slot is \(577\:\mu\text{s}\). There are \(148\) data bits and \(8.25\) guard bits in a slot.
Symbol duration	\(3.6828\:\mu\text{s}\)
Transmit rate	\(270.833\text{ kbit/s}\)

Table \(\PageIndex{3}\): Attributes of the GSM system. Uplink and downlink frequencies are for the GSM-900 implementation, see Table \(\PageIndex{4}\) for other GSM implementations. Slow frequency hoping improves robustness.

Band	Uplink \((\text{MHz})\)	Downlink \((\text{MHz})\)	Duplex Spacing \((\text{MHz})\)
GSM-900 GSM-1800	\(890-915\) \(1710-1785\)	\(935-960\) \(1805-1880\)	\(45\) \(95\)
GSM-900 extended	\(876-915\)	\(921-960\)	\(45\)
PCS-1900 GSM-850 (Americas)	\(1850-1910\) \(824-849\)	\(1930-1990\) \(869-894\)	\(80\) \(45\)
GSM-450 GSM-480 (Nordic, Eastern Europe, Russia)	\(450.4-457.6\) \(478.8-486\)	\(460.4-467.6\) \(488.8-496\)	\(10\) \(10\)

Table \(\PageIndex{4}\): GSM frequency bands. GSM channels have a bandwidth of \(200\text{ kHz}\). The base-to-mobile transmission is the downlink and the mobile-to-basestation transmission is the uplink. GSM-900 and GSM-1800 are used in most of the world.

with uncoordinated 1G analog phone systems. The attributes of the GSM system are shown in Tables \(\PageIndex{3}\) and \(\PageIndex{4}\).

From an RF design perspective, the main differences between analog and digital standards are

1. The RF envelope. In AMPS, FM was used, which produces a constant envelope RF signal. Consequently, high-efficiency saturation mode amplifiers (such as Class C) can be used. In most digital modulation schemes the modulation results in a nonconstant envelope. This is true for PSK modulation, as the transition from one symbol to another does not follow a circle on the constellation diagram. The information contained in the amplitude of the RF signal is just as important as the information contained in the phase or frequency of the signal. Consequently, with digital radio saturation mode amplifiers that severely distort the amplitude characteristic must be avoided.
2. Bursty RF. In an analog system, RF power is continually being transmitted. In a digital system, transmission is intermittent and the RF signal is bursty. Therefore an RF designer must be concerned about turn-on transients and thermal stability of the power amplifier.