The second generation of cellular system was introduced after a decade of first generation. The last decade of 19th century started off with this digital generation. 2G systems were primarily aimed towards the voice market.
There were several shortcomings of the 1G systems, like limited coverage and lower capacity. As the popularity of cellular phones started increasing , the capacity of cellular systems was a challenge for the service providers.
Another shortcoming of 1G systems was the limited ability of the controller and the phones to exchange information during the course of a call. The control information was passed through the voice channel in a "blank and burst" basis. That means speech was briefly( 100 ms or may be more) interrupted whenever
the control message moves phone and the base station. I am sure this was a major issue as QoS was degraded.
The shift from analog to digital enhanced the performance of cellular systems.
Secondly to meet the increasing demands following techniques were used
1. The reuse of spectrum efficient digital speech codecs.
2. multiplexing techniques (frequency / time)
3. higher(tighter) frequency reuse by better performance of digital modulation and coding
There were several major 2G standards like GSM, IS-95 CDMA, IS- 135 TDMA.
1. GSM : This system originated in Europe in 1990. The frequency bands used are 850/900 MHz, 1.8/1.9 GHz with channel bandwidth of 200kHz. These systems were either TDMA or FDMA. FDD duplexing technique was implemented. The peak data rates supported by the system was 107 kbps(GPRS) and 384 kbps(EDGE). Typically user data rates were 20-40 kbps(GPRS) and 80-120 kbps(EDGE). The permissible latency was 600- 700 ms.
2. IS-95 : This was the first CDMA system using 850MHz/1.9 GHz frequency bands with 1.25 MHz channel bandwidth. The peak data rate was 115 kbps but typically a user could get a data rate upto 64 kbps. The user plane latency was greater than 600ms. (FYI : for LTE the latency is less than 100ms).
3. IS-54 : This system was later modified to IS-136. The frequency used was 850MHz/1.9 GHz with 30kHz channel bandwidth. TDMA/FDMA were the multiple access techniques. The data rate supported was very low, a peak of 12 kbps and typical user data rate was around 9 kbps.
The 2G systems not only provided improved voice quality but also supported some new applications like SMS , updates, alerts, bill payments. Later these systems were equipped to provide low data rates as well.
There were several shortcomings of the 1G systems, like limited coverage and lower capacity. As the popularity of cellular phones started increasing , the capacity of cellular systems was a challenge for the service providers.
Another shortcoming of 1G systems was the limited ability of the controller and the phones to exchange information during the course of a call. The control information was passed through the voice channel in a "blank and burst" basis. That means speech was briefly( 100 ms or may be more) interrupted whenever
the control message moves phone and the base station. I am sure this was a major issue as QoS was degraded.
The shift from analog to digital enhanced the performance of cellular systems.
Secondly to meet the increasing demands following techniques were used
1. The reuse of spectrum efficient digital speech codecs.
2. multiplexing techniques (frequency / time)
3. higher(tighter) frequency reuse by better performance of digital modulation and coding
There were several major 2G standards like GSM, IS-95 CDMA, IS- 135 TDMA.
1. GSM : This system originated in Europe in 1990. The frequency bands used are 850/900 MHz, 1.8/1.9 GHz with channel bandwidth of 200kHz. These systems were either TDMA or FDMA. FDD duplexing technique was implemented. The peak data rates supported by the system was 107 kbps(GPRS) and 384 kbps(EDGE). Typically user data rates were 20-40 kbps(GPRS) and 80-120 kbps(EDGE). The permissible latency was 600- 700 ms.
2. IS-95 : This was the first CDMA system using 850MHz/1.9 GHz frequency bands with 1.25 MHz channel bandwidth. The peak data rate was 115 kbps but typically a user could get a data rate upto 64 kbps. The user plane latency was greater than 600ms. (FYI : for LTE the latency is less than 100ms).
3. IS-54 : This system was later modified to IS-136. The frequency used was 850MHz/1.9 GHz with 30kHz channel bandwidth. TDMA/FDMA were the multiple access techniques. The data rate supported was very low, a peak of 12 kbps and typical user data rate was around 9 kbps.
The 2G systems not only provided improved voice quality but also supported some new applications like SMS , updates, alerts, bill payments. Later these systems were equipped to provide low data rates as well.
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