WCDMA vs HSDPA Network Technology
WCDMA (Wideband CDMA)
WCDMA is the multiple access technology used in 3G mobile networks radio access interface allowing subscribers to achieve more secured communication facility with much higher data rates. The original idea behind broadband communication networks is to provide higher data rates so that people can have video conferences, high speed internet access, mobile gaming, and video streaming through the mobile terminal. WCDMA was evolved as a part of 3GPP in order to achieving a worldwide interoperability among 3G networks.
The main feature behind WCDMA technique is that the 5MHz channel bandwidth is used to send the data signals over the air interface and in order to achieve this original signal is mixed with a pseudo random noise code which is also known as Direct Sequence CDMA. This is a unique code for each user and only the users who are having the correct code can decode the message. So with the high frequency associated with the pseudo signal original signal is modulated in to higher bandwidth and due to high spectrum original signals spectral components sink in the noise. As a result jammers can see the signal as a noise without the pseudo code.
WCDMA uses either TDD or FDD mode while achieving full duplex communication. In TDD the uplink and downlink data are sent over a single 5MHz channel with time multiplexing whilst the FDD mode uses two separate channels for uplink and downlink which are 190MHz band separated. Originally WCDMA uses QPSK as the modulation scheme. Data rates that WCDMA support are 384kbps in mobile environment and over 2Mbps in static environments as specified by ITU for 3G networks with data rates can carry up to 100 simultaneous voice calls or 2Mbps data speeds.
HSDPA (High Speed Downlink Packet Access)
HSDPA is the next phase of 3G UMTS for achieving data speeds for data oriented applications in which downlink data rates are increased irrespective of uplink. By moving to these newly specified networks it is possible to improve the capacity of networks and lower costs for per bit transmission.
The proposed networks are capable of delivering downlink data rates of 14.4 Mbps maximum with the higher order modulation schemes over the WCDMA 5MHz channel band width. This will use 16 QAM (Quadrature Amplitude Modulation) as the digital modulation scheme which is the factor increasing the data rates up to 14.4 Mbps and an added advantage of resilient to noise.
HSDPA mobile terminals are categorized in to 12 by 3GPP which defines the different data rates in HSDPA which are based on factors like TTI, Transport Block Size, modulation schemes etc.
Difference between WCDMA and HSDPA
1. HSDPA uses WCDMA with 16 QAM modulation technique and original WCDMA networks use QPSK as the modulation scheme.
2. WCDMA fro 3G networks are capable of providing data rates up to 2Mbps and HSDPA is capable of proving downlink data rates up to 14.4 Mbps.
3. Fast HARQ (Hybrid Automatic Repeat Request) is being used in HSDPA networks and traditional WCDMA networks don’t use this feature.
4. HSDPA hand sets are categorized in to 12 according to TTI, Transport Block Size, modulation schemes etc used for HSDPA networks and WDMA networks doesn’t categorized like that in original 3G network deployment.
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