UMTS和WCDMA网络技术之间的差异

UMTS vs WCDMA Network Technology

UMTS and WCDMA are terms related to 3G mobile communication. While UMTS refers to the 3G network specification, WCDMA is one of the radio access technologies for UMTS.

UMTS (Universal Mobile Telecommunications System)

This is the successor of 2G (GSM) network specification in which much more consideration was given for higher data rates to support a variety of applications by mobile users. UMTS uses a totally different air interface for radio communications hence different from 2G in many ways and require specialized handsets for the new networks based on UMTS. WCDMA is the air interface technology being used in UMTS networks.

现在，3GPP维护UMT的规格，负责为第三代移动通信网络提供全球接受的技术规格和标准。该网络体系结构具有称为UTRAN（通用地面无线电访问网络）的核心网络和访问网络，该网络由节点B和RNC（无线电网络控制器）类似于BTS和BSC组成2G网络中。UMTS频率分配允许使用2GHz范围，特别是1885-2025 MHz和2110-2200 MHz，如1992年世界行政广播会议中指定

Most of the features UMTS has extracted from GSM networks. GSM initialize the concept of SIM (Subscriber Identity Module) which is used in UMTS also as USIM (Universal SIM) and the network architecture has similar components as mentioned above RNC and node B in access network. also UMTS uses FDD and TDD in which FDD uses two different frequencies for uplink and downlink whilst TDD mode utilize same frequency for uplink and downlink with time multiplexing for transmission and receiving. The TDD mode is most preferred since UMTS stresses on high speed data rates for mobile applications so by allocating more time higher data rates are possible with downlink other than uplink.

WCDMA (Wideband CDMA)

这是为UMTS无线电访问接口指定的多个访问技术，使订阅者能够实现具有更高数据速率的更安全的通信设施。在空气界面中利用WCDMA的UMTS允许宽带通信成为现实，因此人们可以通过移动终端（用户设备）进行视频会议，高速互联网访问，移动游戏和视频流。

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 frequency signal and due to high spectrum original signal spectral components sink in the noise. As a result jammers can see the signal as a noise without the pseudo code.

Frequency band assigned for FDD-WCDMA consists of 1920-1980 and 2110-2170 MHz Frequency paired uplink and downlink with 5MHz band width channels and duplex distance is 190 MHz s.

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.

Difference between UMTS and WCDMA 1. UMTS is the 3G specifications for mobile communications and WCDMA is one of the proposed radio access technologies for UMTS. 2. UMTS has defined TDD-CDMA or FDD-WCDMA with frequency ranges of 1920-1980 and 2110-2170 MHz Frequency Division Duplex (FDD, W-CDMA) and 1900-1920 and 2010-2025 MHz Time Division Duplex (TDD, TD/CDMA).