Reducing internal and external fragmentations of OVSF codes in WCDMA systems with multiple codes

Chih Min Chao*, Yu-Chee Tseng, Li-Chun Wang

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

35 Scopus citations

Abstract

In the 3GPP technical specification, OVSF codes are used as channelization codes. The use of OVSF codes can provide variable data rates to flexibly support applications with different bandwidth requirements. Most works in the literature assume that only one signal OVSF code is used to support one connection. This may sometimes waste the scarce wireless bandwidth since the allocated bandwidth will increase exponentially as the spreading factor decreases, i.e., a user may be "over-served". In this paper, we consider the possibility of using multiple OVSF codes to support a connection. We show how using multiple codes can reduce internal fragmentation and external fragmentation of a OVSF code tree. The tradeoff between bandwidth utilization and hardware complexity of a multi-code system is analyzed. The result shows that using 2 or 3 codes will be quite cost-effective. Several multi-code assignment and reassignment strategies, namely random, left-most, crowded-first-space, and crowded-first-code, are proposed based on such environment. Our simulation results show significant increase in code tree utilization and significant reduction in code blocking probability by using the crowded-first-space and crowded-first-code schemes.

Original languageEnglish
Title of host publication2003 IEEE Wireless Communications and Networking Conference, WCNC 2003
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages693-698
Number of pages6
ISBN (Electronic)0780377001
DOIs
StatePublished - 16 Mar 2003
Event2003 IEEE Wireless Communications and Networking Conference: The Dawn of Pervasive Communication, WCNC 2003 - New Orleans, United States
Duration: 16 Mar 200320 Mar 2003

Publication series

NameIEEE Wireless Communications and Networking Conference, WCNC
Volume1
ISSN (Print)1525-3511

Conference

Conference2003 IEEE Wireless Communications and Networking Conference: The Dawn of Pervasive Communication, WCNC 2003
CountryUnited States
CityNew Orleans
Period16/03/0320/03/03

Keywords

  • 3G
  • Mobile communication
  • OVSF
  • Personal communication services
  • WCDMA
  • Wireless communication

Fingerprint Dive into the research topics of 'Reducing internal and external fragmentations of OVSF codes in WCDMA systems with multiple codes'. Together they form a unique fingerprint.

Cite this