This post covers Wireless Communications: Principles and Practices by Theodore S. Rapport.

Basic Ideas

• The 3G - Fundamental System Design

  • 3G systems promise unparalleled wireless access in ways that have never been possible before. Multi-megabit Internet access, communications using Voice over Internet Protocol (VoIP), voice-activated calls, unparalleled network capacity, and ubiquitous “always-on” access are just some of the advantages being touted by 3G developers.
  • Companies developing 3G equipment envision users having the ability to receive live music, conduct interactive web sessions, and
  • have simultaneous voice and data access with multiple parties at the same time using a single mobile handset, whether driving, walking, or standing still in an office setting.
  • The International Telecommunications Union (ITU) formulated a plan to implement a global frequency band in the 2000 MHz range that would support a single, ubiquitous wireless communication standard for all countries throughout the world.
  • This plan, called International Mobile Telephone 2000 (IMT- 2000), has been successful in helping to cultivate active debate and technical analysis for new high speed mobile telephone solutions when compared to 2G.
  • The hope for a single worldwide standard has not materialized, as the worldwide user community remains split between two camps: GSM/IS-136/PDC and CDMA.
  • The eventual 3G evolution for CDMA systems leads to cdma2000. Several variants of CDMA 2000 are currently being developed, but they all are based on the fundamentals of IS-95 and IS-95B technologies.
  • The eventual 3G evolution for GSM, IS-136, and PDC systems leads to Wideband CDMA (W-CDMA), also called Universal Mobile Telecommunications Service (UMTS). W-CDMA is based on the network fundamentals of GSM, as well as the merged versions of GSM and IS-136 through EDGE. It is fair to say that these two major 3G technology camps, cdma2000 and W-CDMA, will remain popular throughout the early part of the 21st century.
  • Commercial grade 3G equipment is expected to be available in the 2002-2003 time frame. Two good Internet sources for up-to-the-minute 3G developments can be found at GSM World and the CDMA Developers Group.
  • The ITU IMT-2000 standards organizations are currently separated into two major organizations reflecting the two 3G camps: 3GPP (3G Partnership Project for Wideband CDMA standards based on backward compatibility with GSM and IS-136/PDC) and 3GPP2 (3G Partnership Project for cdma2000 standards based on backward compatibility with IS-95).
  • Countries throughout the world are currently determining new radio spectrum bands to accommodate the 3G networks that will likely be deployed in the 2004-2005 time frame.
  • ITU’s 2000 World Radio Conference established the 2500–2690 MHz, 1710–1885 MHz, and 806–960 MHZ bands as candidates for 3G.
  • In the US, additional spectrum in the upper UHF television bands near 700 MHz is also being considered for 3G.
  • Given the economic downturn of the telecommunications industry during 2001, many governments throughout the world, including the US, had postponed their 3G auctions and spectrum decisions as of late 2001.
  • Some European governments, however, auctioned off radio spectrum for 3G well before the telecommunications industry depression of 2001. The sale price of the spectrum was astounding! England’s first ever spectrum auction
  • The Universal Mobile Telecommunications System (UMTS) is a visionary air interface standard that has evolved since late 1996 under the auspices of the European Telecommunications Standards Institute (ETSI).
  • European carriers, manufacturers, and government regulators collectively developed the early versions of UMTS as a competitive open air-interface standard for third generation wireless telecommunications.
  • UMTS was submitted by ETSI to ITU’s IMT-2000 body in 1998 for consideration as a world standard.
  • At that time, UMTS was known as UMTS Terrestrial Radio Access (UTRA), and was designed to provide a high capacity upgrade path for GSM. Around the turn of the century, several other competing wideband CDMA (W-CDMA) proposals agreed to merge into a single W-CDMA standard, and this resulting W-CDMA standard is now called UMTS.
  • UMTS, or W-CDMA, assures backward compatibility with the second generation GSM, IS- 136, and PDC TDMA technologies, as well as all 2.5G TDMA technologies. The network structure and bit level packaging of GSM data is retained by W-CDMA, with additional capacity and bandwidth provided by a new CDMA air interface.
  • Today, W-CDMA is the primary focus of the 3GPP world standard body, and while ETSI remains the organizational body that coordinates the W-CDMA standards effort, W-CDMA development now involves leading manufacturers, carriers, engineers, and regulators from throughout the world within the 3GPP community.
  • The 3GPP standards body is developing W-CDMA for both wide area mobile cellular coverage (using FDD) as well as indoor cordless type applications (using TDD).
  • The 3G W-CDMA air interface standard had been designed for “always-on” packet based wireless service, so that computers, entertainment devices, and telephones may all share the same wireless network and be connected to the Internet, anytime, anywhere.
  • W-CDMA will support packet data rates up to 2.048 Mbps per user (if the user is stationary), thereby allowing high quality data, multimedia, streaming audio, streaming video, and broadcast-type services to consumers.
  • Future versions of W-CDMA will support stationary user data rates in excess of 8 Mbps. W-CDMA provides public and private network features, as well as videoconferencing and (VHE).
  • W-CDMA designers contemplate that broadcasting, mobile commerce (m-commerce), games, interactive video, and virtual private networking will be possible throughout the world, all from a small portable wireless device.
  • W-CDMA requires a minimum spectrum allocation of 5 MHz, which is an important distinction from the other G standards.
  • Although W-CDMA is designed to provide backward compatibility and interoperability for all GSM, IS-136/PDC, GPRS, and EDGE equipment and applications, it is clear that the wider air interface bandwidth of W-CDMA requires a complete change out of the RF equipment at each base station.
  • With W-CDMA data rates from as low as 8 kbps to as high as 2 Mbps will be carried simultaneously on a single W-CDMA 5 MHz radio channel, and each channel will be able to support between 100 and 350 simultaneous voice calls at once, depending on antenna sectoring, propagation conditions, user velocity, and antenna polarizations.
  • W-CDMA employs variable/selectable direct sequence
  • Time Division-Synchronous Code Division Multiple Access, or TD-SCDMA, is a 3G mobile telecommunications standard, being pursued in the People’s Republic of China by the Chinese Academy of Telecommunications Technology (CATT).
  • This proposal was adopted by ITU as one of the 3G options in late 1999. TD-SCDMA is based on spread spectrum technology.
  • TD-SCDMA uses TDD, in contrast to the FDD scheme used by W-CDMA.
  • By dynamically adjusting the number of timeslots used for downlink and uplink, the system can more easily accommodate asymmetric track with different data rate requirements on downlink and uplink than FDD schemes.
  • Since it does not require paired spectrum for downlink and uplink, spectrum allocation fexibility is also increased.
  • Also, using the same carrier frequency for uplink and downlink means that the channel condition is the same on both directions, and the base station can deduce the downlink channel information from uplink channel estimates, which is helpful to the application of beamforming techniques.
  • TD-SCDMA also uses TDMA in addition to the CDMA used in W-CDMA. This reduces the number of users in each timeslot, which reduces the implementation
  • Beyond 3G Networks
  • Beyond 3G networks, or 4G (Fourth Generation), represent the next complete evolution in wireless communications.
  • A 4G system will be able to provide a comprehensive IP solution where voice, data and streamed multimedia can be given to users at higher data rates than previous generations.
  • There is no formal denition for 4G ; however, there are certain objectives that are projected for 4G.
  • It will be capable of providing between 100 Mbit/s and 1 Gbit/s speeds both indoors and outdoors, with premium quality and high security. It would also support systems like multicarrie communication, MIMO and UWB.