The second generation had a significant increase in the capacity and hence the number of users supported. But the third generation was a big jump in terms of data rate, services and applications. Besides these enhanced features, 3G systems also provide better Quality of Service for voice telephony, internet browsing, multimedia, location based services, etc.
There were certain requirements(laid by ITU) every 3G system has to fulfill. These are in terms of data rates.
1. 2 Mbps in fixed/building environment
2. 384 kbps in pedestrian environment
3. 144 kbps in vehicular environment
There are four major 3G standards
1. WCDMA
2. CDMA 2000
3. EV-DO
4. HSPA
Lets discuss each standard.
1. WCDMA : It's actually same as UMTS (Universal Mobile Telephone System). Initially I had a confusion between WCDMA and UMTS unless I got to know that UMTS is a standard based on WCDMA.(Why not to call it UMTS then !! :))
The basic specs include frequency bands 850/900MHz, 1.8/1.9/2.1GHz, channel bandwidth of 5MHz, peak data rate 384-2048 kbps (but typical user rate is just 150-300 kbps).The user plane latency was 100-200 ms and CDMA, FDD was implemented. DS SS - QPSK modulation scheme was used.
UMTS retains the basic architecture fron GSM networks but the air interface (WCDMA) is way different than that of GSM. Its is a DIrect sequence spread spectrum, here data is multiplied with psuedo random codes that provide channelization and scrmbling. It is specified for TDD and FDD both!! (although FDD is by far the most widely deployed).
Some of the important features of W-CDMA are
1. Use of Alamouti space-time coding for transmit diversity
2. Wider choice of spreading factors
3. multi code use by a single user is supported(higher data rates!!)
2.CDMA2000 : Well strictly speaking CDMA2000-1X did not meet the data rate requirements but CDMA2000 -3X did.Sometimes it is mentioned as CDMA-1X-EVDO. i.e. CDMA-1X EVolution Data Only. The specifications are frequency bands 450/850MHz 1.7/1.9/2.1GHz , 1.25MHz channel bandwidth, Data rates of DL:2.4–4.9Mbps UL:800–1800kbps, latency upto 200ms was observed. DS-SS: QPSK, 8PSK and 16QAM was the modulation scheme with Frequency division duplexing.
3. HSPA : High Speed Packet Access was another 3G standard. There were number of techniques developed for increasing the data speed like adaptive modulation , dynamic scheduling etc. Basically, HSPA is a combination of HSDPA and HSUPA . These were the two enhancements applied to WCDMA to further increase the data rate. Except for the modulation scheme that HSPA standard is same as WCDMA. The modulation scheme is adaptive and hence DS-SS: QPSK, 16QAM and 64QAM is used. The latency was reduced to 50-90 ms and the data rates were drastically increased to DL:3.6–14.4Mbps UL:2.3–5Mbps!!
There were certain requirements(laid by ITU) every 3G system has to fulfill. These are in terms of data rates.
1. 2 Mbps in fixed/building environment
2. 384 kbps in pedestrian environment
3. 144 kbps in vehicular environment
There are four major 3G standards
1. WCDMA
2. CDMA 2000
3. EV-DO
4. HSPA
Lets discuss each standard.
1. WCDMA : It's actually same as UMTS (Universal Mobile Telephone System). Initially I had a confusion between WCDMA and UMTS unless I got to know that UMTS is a standard based on WCDMA.(Why not to call it UMTS then !! :))
The basic specs include frequency bands 850/900MHz, 1.8/1.9/2.1GHz, channel bandwidth of 5MHz, peak data rate 384-2048 kbps (but typical user rate is just 150-300 kbps).The user plane latency was 100-200 ms and CDMA, FDD was implemented. DS SS - QPSK modulation scheme was used.
UMTS retains the basic architecture fron GSM networks but the air interface (WCDMA) is way different than that of GSM. Its is a DIrect sequence spread spectrum, here data is multiplied with psuedo random codes that provide channelization and scrmbling. It is specified for TDD and FDD both!! (although FDD is by far the most widely deployed).
Some of the important features of W-CDMA are
1. Use of Alamouti space-time coding for transmit diversity
2. Wider choice of spreading factors
3. multi code use by a single user is supported(higher data rates!!)
2.CDMA2000 : Well strictly speaking CDMA2000-1X did not meet the data rate requirements but CDMA2000 -3X did.Sometimes it is mentioned as CDMA-1X-EVDO. i.e. CDMA-1X EVolution Data Only. The specifications are frequency bands 450/850MHz 1.7/1.9/2.1GHz , 1.25MHz channel bandwidth, Data rates of DL:2.4–4.9Mbps UL:800–1800kbps, latency upto 200ms was observed. DS-SS: QPSK, 8PSK and 16QAM was the modulation scheme with Frequency division duplexing.
3. HSPA : High Speed Packet Access was another 3G standard. There were number of techniques developed for increasing the data speed like adaptive modulation , dynamic scheduling etc. Basically, HSPA is a combination of HSDPA and HSUPA . These were the two enhancements applied to WCDMA to further increase the data rate. Except for the modulation scheme that HSPA standard is same as WCDMA. The modulation scheme is adaptive and hence DS-SS: QPSK, 16QAM and 64QAM is used. The latency was reduced to 50-90 ms and the data rates were drastically increased to DL:3.6–14.4Mbps UL:2.3–5Mbps!!
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