Introduction

This is a practical Wideband Code Division Multiple Access (WCDMA) measurement procedures note. The objective of this note is to present measurement tips and procedures which will help a field-based network technician or RF engineer conduct Node B measurements on WCDMA access networks.

Evolution To WCDMA

In the mid 1980’s a second generation (2G) digital system known as the Global System for Mobile Communications (GSM) was introduced for mobile telephony. It significantly improved speech quality over the older analog-based systems and, as it was an international standard, enabled a single telephone number and mobile phone to be used by consumers around the world. It led to significantly improved connectivity and voice quality, as well as the introduction of a whole slew of new digital services like low-speed data. Proving to be very successful, GSM was officially adopted by the European Telecommunications Standardization Institute (ETSI) in 1991. It is now widely used in over 160 countries worldwide.
The success of GSM spurred the demand for further development in mobile telephony, and put it on an evolutionary path to third generation (3G) technology. Along the way, that development path has included 2G technologies like Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA). TDMA is similar in nature to GSM and provides for a tripling of network capacity over the earlier AMPS analog system. In contrast, CDMA is based on the principles of spread sprectrum communication. Access to it is provided via a system of digital coding.In 1997 a 2.5G system called the General Radio Packet Service (GPRS) was introduced to accommodate the growing demand for Internet applications. As opposed to the existing 2G systems, it offered higher data rates and Quality of Service (QoS) features for mobile users by dynamically allocating multiple channels. GPRS installs a packet switch network on top of the existing circuit switch network of GSM, without altering the radio interface.
In 1999, the International Telecommunications Union (ITU) began evaluating and accepting proposals for 3G protocols in an effort to coordinate worldwide migration to 3G mobile networks. These proposals were known as International Mobile Telecommunication 2000 (IMT-2000). One of the most important IMT-2000 proposals to emerge was Universal Telecommunications Services (UMTS). While GPRS is considered the first step in enhancing the GSM core network in preparation for EDGE and 3G, WCDMA is a 3G technology according to the 3GPP standard (Figure 1). It is the digital access system for the UMTS network and is today considered one of the world’s leading 3G wireless standards.

Understanding WCDMA

WCDMA is an approved 3G technology which increases data transmission rates via the Code Division Multiplexing air interface, rather than the Time Division Multiplexing air interface of GSM systems. It supports very high-speed multimedia services such as full-motion video, Internet access and video conferencing. It can also easily handle bandwidth-intensive applications such as data and image transmission via the Internet. WCDMA is a direct spreading technology, it spreads its transmissions over a wide, 5 MHz, carrier and can carry both voice and data simultaneously. It features a peak data rate of 384 kbps, a peak network downlink speed of 2 Mbps and average user throughputs (for file downloads) of 220-320 kbps. In addition, WCDMA boasts increased capacity over EDGE for high- bandwidth applications and features which include, among other things, enhanced security, QoS, multimedia support, and
reduced latency (Table 1).

WCDMA networks offer a number of significant benefits. They are:

• High bandwidth and low latency which contributes significantly to a higher-quality user experience and in turn increases data revenue and improves customer satisfaction.
• Support for a wide array of new and emerging multimedia services.
• Considered the most cost-effective means of adding significant capacity for both voice and data services.
• Far better integration of RF components in the base station as compared to any other radio or mobile technology. A WCDMA base station cabinet has several times the RF capacity of GSM cabinets.
• Extreme flexibility in allocating capacity to offer the optimal QoS for different traffic types. To date, WCDMA has been adopted for 3G use as specified in the 3GPP standard by ETSI in Europe, and as an ITU standard under the name “IMT-2000 direct spread.” NTT DoCoMo launched the first WCDMA service in 2001 and now has millions of subscribers. WCDMA (UMTS) is also the 3G technology of choice for many GSM/GPRS operators, with dozens currently in trials. More than 100 GSM/GPRS operators have even licensed new spectrum with the intent to launch
WCDMA services in the coming years.

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