The first operational 1G Cellular System was introduced and implemented by Nippon Telephone and Telegraph Company (NTT) in Tokyo, Japan in 1979. After two years 1G Mobile Systems reached Europe and two most famous 1G systems were introduced and implemented in Europe that are Nordic Mobile Telephones (NMT) and Total Access Communication Systems (TACS). The major problem associated with the European 1G systems was the lack of inter-operability between different mobile networks. So, Mobile Network didn’t guarantee any roaming services between different operators, though the system had the ability of handover and roaming within an operator network.

In 1983, USA introduced its 1G system known as Advanced Mobile Phone Systems. FCC allocated 40MHz bandwidth for AMPS which carried Six Hundred and Sixty Six (666) duplex channels in 800 MHz range and an individual uplink or downlink Channel had a bandwidth of 30KHz. Later, FCC allocated additional 10MHz bandwidth and as a result total Duplex Channels became 832 as further 166 Channels were introduced in conjunction with previous 666 channels. 

General Features of 1G Systems

The main features of 1G Analog Phones are listed below:

1. Analog Technology: 1G systems are purely Analog Systems
2. FDMA Access Technique : All 1G systems are FDMA based system
3. Modulation Scheme : All 1G systems are based on FM modulation scheme
4. Year of Introduction : 1980s to end of 80s
5. Services offered: Voice only.
6. Bad Utilization of Spectrum: Capacity of 1G is low because of FDMA access techniques.

1G NTT Technology in Japan:

NTT System was introduced in 1979 by Nippon Telephone and Telegraph Company in Japan.

Systems specification are as below:

• Total Number of Duplex Channels : 600
• Access Technique : FDMA
• Simplex Channel Bandwidth : 25 KHz
• RF Band Range : 800 MHz band
• Year of Introduction : 1979

1G Advanced Mobile Phone Systems (AMPS) Technology in USA:

In 1983, Federal Community of Communication (FCC) dedicated 40MHz bandwidth in range of 900 MHz for AMPS systems. The AMPS systems had 666 duplex channels with an individual channel having a bandwidth of 30 KHz. It was for the first time implemented in Chicago. Later on, in 1989 additional 10MHz bandwidth was allocated and hence 166 more duplex channels were introduced in the system. 1G AMPS systems have following specifications:

• RF Range : 800 MHz
• Individual Channel Bandwidth : 30 KHz
• Total No of channels : 832 (Duplex )
• Duplex Length : 45 MHz
• Total bandwidth dedicated to AMPS : 50 MHz
• Reverse Channel : 824-849 MHz
• Forward Channel : 869-894 MHz
• Modulation Scheme : FM
• Technology : Analog
• Access Technology : FDMA

Among 832 duplex channels, 21 channels were dedicated as control channels for call setup.

1G Systems in Europe:

Two basic Systems being introduced by Europe were:

• Nordic Mobile Telephone Systems (NMT)
• European Total Access Cellular System (ETACS)

Nordic Mobile Telephone Systems (NMT-450):

Two years after introduction of NTT systems in Japan, European version of 1G was introduced. 1G Nordic Mobile Telephone System (NMT-450) was introduced and implemented in 1981 by Nordic States that are Sweden, Finland, Norway, and Denmark. Following are the features of NTT-450

• Total Number of Duplex Channels: 180 channels (In Finland 160 channels).
• Modulation Scheme :FM
• Access Technique : FDMA
• Simplex Channel Bandwidth : 25 KHz
• RF Band Range : 450 MHz band
• Duplex Length : 10 MHz
• Year of Introduction : 1981

Nordic Mobile Telephone Systems (NMT-900):

Because of rapid success of NMT-450, Europe introduced another variant of NMT in 900 MHz range and called it NMT-900. Following are the features of NTT-900

• Total Number of Duplex Channels : 999 channels
• Modulation Scheme :FM
• Access Technique : FDMA
• Simplex Channel Bandwidth : 12.5 KHz
• RF Band Range : 900 MHz band
• Duplex Length : 10 MHz
• Year of Introduction : 1986

Comparison of NMT-450 and NMT-900

NMT-450	NMT-900
Low Frequency range	High Frequency range
High Transmitted Power	Low Transmitted Power
Large Cell Size	Small Cell Size
Less vulnerable to interference	More vulnerable to interference
No dedicated Control Channels and Mobile Phone scans vacant channels which is time consuming task	Dedicated Control Channels called Calling Channels, hence less setup time

Both NMT-450 and NMT-900 could coexist on same basestation.

European Total Access Cellular System (TACS):

TACS was introduced in 1985 and initially it was implemented in UK and then implemented in twenty five different European countries. Technically, it is European version of AMPS . First, it was named as TACS and then later version of system became ETACS.

TACS:

.Following are the features of TACS

• Modulation Scheme : FM
• Access Technique : FDMA
• Total Bandwidth allocated: 50MHz
• Simplex Channel Bandwidth : 25 KHz
• RF Band Range : 900 MHz band
• Uplink frequency range : 890-915 MHz
• Downlink frequency range:935-960
• Year of Introduction : 1985

ETACS:

Additional 16 MHz were allocated to ETACS in order to accommodate more users through this technology.

Narrow Band TACS (NTACS):

In narrow band TACS, the channel bandwidth was reduced from 25 KHz to 12.5 KHz. Following are features of NTACS:

• Modulation Scheme : FM
• Access Technique : FDMA
• Simplex Channel Bandwidth : 12.5 KHz
• RF Band Range : 900 MHz band
• Year of Introduction : 1993

Japanese version of TACS:

JTACS is the Japanese version of TACS:

Following are features of JTACS:

• Modulation Scheme :FM
• Access Technique : FDMA
• Simplex Channel Bandwidth : 25 KHz
• RF Band Range : 900 MHz band
• Year of Introduction : 1988

Deficiencies in 1G Systems

There are several deficiencies in AMPS, some of them are discussed below:

• 1G European Cellular Systems are incompatible with one another .The inoperability is due to different Frequency ranges of these Systems.
• Mobile Network does not guarantee any inter-operator roaming services. 
• Limited Serving area and very low Capacity.
• FDMA is not good technique in terms of system’s capacity.
• No Mobile Assisted Handover and hence more burden on MSC.