WCDMA – Overview
WCDMA is 3G mobile Internet access technology. Find out about the 3G broadband wireless internet, the technology that has changed modern society.
What is WCDMA?
WCDMA – Wideband Code Division Multiple Access is a standard used in 3G mobile networks.
This 3G technology enables different services:
- Conventional voice
- Text or SMS messages
- MMS messages
- Broadband mobile wireless internet
WCDMA defines the behavior of Radio Access Network and user equipment (cellular phones and other 3G mobile devices). This Radio Access Network – RAN is part of the mobile network, which enables mobile wireless connection to different user devices. With this type of mobile wireless connection, cellular devices can enjoy different services.
Read more about what is 3G in the post What is 3G? Compare 3G Speed and 4G Speed.
It is hard to describe the WCDMA technology without basic knowledge in Radio networks and modulation techniques. In spite of this, I will try to explain it in simple words, so the average reader could understand this radio access technology.
- DS-CDMA System
- Carrier bandwidth of 5 MHz
- Highly variable user data rates
- Supports two basic modes: FDD and TDD
- Efficient power control
- Peak data rates up to 14.4 Mbps in downlink and 1.92 Mbps in uplink
Downlink and Uplink
It is useful to explain what exactly means uplink and downlink. In downlink connection information is carried from mobile operator network (RAN) to the user equipment (cell phone). In uplink connection information is carried from the cell phone to the mobile operator network.
WCDMA is wideband Direct-Sequence Code Division Multiple Access or DS-CDMA modulation. Modulation is the method of modifying the information signal. The reason of performing this modification is that signal can be physically transmitted. Modulation enables that your cellular device can contact other cellular device or internet over the mobile network.
User information in WCDMA is spread over a frequency bandwidth of 5 MHz and at the same time this data is coded with different codes. This usage of different codes of wide bandwidth enables relatively high bit rates.
WCDMA and UMTS Frequency Bands
WCDMA in 3G mobile broadband uses UMTS frequency bands. There are different frequency bands used for 3G. The frequency also depends on different world regions. Below is rough separation for different regions.
- 2100 MHz -IMT used in Europe, Asia, Africa and Oceania
- 1900 MHz -PCS used in North and Latin America
- 850 MHz -CLR used in North and Latin America
- 900 MHz – E-GSM used in Europe
Find out more about the UMTS and 3G mobile network in the post UMTS – 3G Mobile Network – How it Works.
Multiple Services with the Variable Bit Rates
WCDMA can enable quite variable data rates for users. This is called BoD or Bandwidth on Demand. Data rates can be changed among users every 10 ms. This fast radio capacity allocation is controlled in the RAN. The aim of this is to make the optimum throughput for different services in 3G network.
FDD and TDD – Two Basic Modes of Operation
WCDMA supports two different basic modes:
- FDD – Frequency Division Duplex
- TDD – Time Division Duplex
In FDD mode different 5 MHz carriers are used both for downlink and uplink. This kind of modulation is a real duplex mode. At the same time is present uplink and downlink information in different frequencies.
In TDD mode, there is only one 5MHz carrier for both downlink and uplink information. In this mode, there is no real duplex. At the same time only downlink or uplink information is transferred.
Efficient Power Control
The WCDMA mobile network supports efficient power control. With this feature saves battery of the user equipment and decreased level of noise in the network.
Efficient power control is accomplished in a way, when the level of signal from the user equipment is increased or decreased. In the RAN there is special module which determines the optimum level of the signal. If the cell phone is very close to the RAN, the level of the signal from the cell phone should be much lower than the level of a signal when it is far from the RAN.
You can always notice that the battery of your cell phone lasts much longer, if you spend more time in an area of high mobile signal.
HSPA – High Speed Packet Access
There are different versions of HSPA or High Speed Packet Access technology:
- HSDPA – High Speed Downlink Packet Access
- EUL – Enhanced Uplink or HSUPA – High Speed Uplink Packet Access
HSDPA, or High Speed Downlink Packet Access enables the theoretical maximum of 14.4 Mbps. EUL (Enhanced Uplink), sometimes called HSUPA (High Speed Uplink Packet Access), provides theoretical maximum uplink speeds of 1.92 Mbps.
If you are interested about 3G and 4G, check the post 3G vs 4G – What is a Better Mobile Internet Connection.
The Actual Speed in Mobile Networks
When we talk about speeds in mobile network, I must warn you for one crucial fact. There is a big difference between the theoretical maximum speed and the actual speed of one user. Sometimes you could even get, for a moment, very high speed. This maximum speed rarely can reach theoretical maximum. The problem is that maximum speed doesn’t last for a long time. The average speed, our effective speed, will be much lower, than the maximum speed, especially much lower than maximum theoretical speed.
WCDMA – Conclusion
WCDMA – Wideband Code Division Multiple Access is a base of 3G technology. You can also find the name UMTS – Mobile Broadband Access used for 3G technology. Its features have made closer social networks and streaming to normal users in everyday environments over their mobile terminals.
Classical WCDMA is not the latest 3G mobile technology. HSDPA and HSPA are enhancements to the WCDMA. Find out about this in the post HSDPA and HSPA – The Fastest 3G Technology.
More about the W-CDMA and UMTS read in wiki article W-CDMA (UMTS).