Symbol Perforation Reduction Schemes for Orthogonal Code Hopping Multiplexing

Jae Hoon CHUNG  Suwon PARK  Dan Keun SUNG  

IEICE TRANSACTIONS on Communications   Vol.E88-B   No.10   pp.4107-4111
Publication Date: 2005/10/01
Online ISSN: 
DOI: 10.1093/ietcom/e88-b.10.4107
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Wireless Communication Technologies
orthogonal code hopping multiplexing,  switched-beam array antenna,  group-level random codeword hopping-pattern allocation,  inter-beam softer handoff,  

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Our previously proposed orthogonal code hopping multiplexing (OCHM) [1],[2] scheme is designed to accommodate a large number of bursty downlink users. However, it may undergo link quality degradation due to symbol perforations occurring when all code-collision symbol values are not identical. In this letter, a group-level random codeword hopping-pattern allocation (GRCHA) scheme is proposed to produce fewer symbol perforations than the previous symbol-by-symbol random codeword hopping (SRCH) of OCHM [1]. The proposed GRCHA scheme combined with the spatial filtering capability of switched-beam array antennas (SBAA) is expected to significantly reduce the symbol perforation probability in the OCHM scheme, and inter-beam softer handoff is applied to cope with high symbol perforation probability for users in overlapping beam areas of SBAA. The performance is evaluated by theoretical analysis and simulation in terms of the average symbol perforation probability. The proposed GRCHA scheme yields better performance than the SRCH scheme and the dedicated codeword allocation scheme, and the diversity gain of inter-beam softer handoff mitigates the effect of high symbol perforation probability for users in the overlapping beam areas.