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On the Design of LAS Spreading Codes

On the Design of LAS Spreading Codes
On the Design of LAS Spreading Codes
A family of Large Area Synchronised (LAS) codes is studied, which exhibits a so-called Interference Free Window (IFW), where both the Inter Symbol Interference (ISI) and the Multiple User Interference (MAI) are suppressed, provided that the relative time offset of the codes is within the IFW. Hence, LAS codes have the potential of increasing the capacity of CDMA networks. However, a specific drawback of this family of sequences is their relatively low duty ratio. A modified algorithm is proposed for determining the constituent LA code’s pulse positions for the sake of improving the duty ratio of the corresponding LAS codes. It is shown that the modified LAS codes exhibit an 18.6% higher duty ratio, than that of the original LAS codes, when considering a minimum LA code pulse interval of 38. The LAS code design examples provided revealed that the system employing the proposed approach improved the data throughput by 40% for the scenario, when the required IFW is ±4-chips and the minimum pulse interval is 19. The availability of the LAS codes is also investigated in conjunction with for the various LS and LA code lengths, employing an extended LS code construction scheme for polyphase complementary sequences and orthogonal LA pulse codes. It is shown that these modified spreading code construction schemes can be combined for generating a family of LAS codes in order to meet various design requirements.
2172-2176
Choi, B.J.
e5e6cf6f-c5a9-4fa1-a038-81782918a1f9
Hanzo, L
66e7266f-3066-4fc0-8391-e000acce71a1
Choi, B.J.
e5e6cf6f-c5a9-4fa1-a038-81782918a1f9
Hanzo, L
66e7266f-3066-4fc0-8391-e000acce71a1

Choi, B.J. and Hanzo, L (2002) On the Design of LAS Spreading Codes. VTC'2002 (Fall), Canada. 24 - 28 Sep 2002. pp. 2172-2176 .

Record type: Conference or Workshop Item (Other)

Abstract

A family of Large Area Synchronised (LAS) codes is studied, which exhibits a so-called Interference Free Window (IFW), where both the Inter Symbol Interference (ISI) and the Multiple User Interference (MAI) are suppressed, provided that the relative time offset of the codes is within the IFW. Hence, LAS codes have the potential of increasing the capacity of CDMA networks. However, a specific drawback of this family of sequences is their relatively low duty ratio. A modified algorithm is proposed for determining the constituent LA code’s pulse positions for the sake of improving the duty ratio of the corresponding LAS codes. It is shown that the modified LAS codes exhibit an 18.6% higher duty ratio, than that of the original LAS codes, when considering a minimum LA code pulse interval of 38. The LAS code design examples provided revealed that the system employing the proposed approach improved the data throughput by 40% for the scenario, when the required IFW is ±4-chips and the minimum pulse interval is 19. The availability of the LAS codes is also investigated in conjunction with for the various LS and LA code lengths, employing an extended LS code construction scheme for polyphase complementary sequences and orthogonal LA pulse codes. It is shown that these modified spreading code construction schemes can be combined for generating a family of LAS codes in order to meet various design requirements.

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More information

Published date: 2002
Additional Information: Event Dates: 24-28 September
Venue - Dates: VTC'2002 (Fall), Canada, 2002-09-24 - 2002-09-28
Organisations: Southampton Wireless Group

Identifiers

Local EPrints ID: 257146
URI: http://eprints.soton.ac.uk/id/eprint/257146
PURE UUID: 35ca87b7-e984-435c-bcf5-2cd74bd395ec
ORCID for L Hanzo: ORCID iD orcid.org/0000-0002-2636-5214

Catalogue record

Date deposited: 26 Jun 2003
Last modified: 17 Dec 2019 02:03

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Contributors

Author: B.J. Choi
Author: L Hanzo ORCID iD

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