Capacity improvement by code-hopping in S-CDMA systems

Unal, B.S.; Tanik, Y.

doi:10.1109/icc.1998.685160

Cited by 7 publications

(3 citation statements)

References 11 publications

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“…One advantage of these code hopping schemes is code diversity [12]. In a multicell environment, cochannel interference in the downlink is averaged, and better BER performance can be expected.…”

Section: Ochmmentioning

confidence: 99%

“…Combining (11), (12), and (15), we can derive the mean synergy ratio for code-colliding modulation symbols including the effect of code collisions among three or more downlink channels. The mean synergy ratio for the code-colliding modulation symbolsλ s,QPSK , andλ s, 16 …”

Section: A Effect Of Code Collisions Related To Three or More Downlimentioning

confidence: 99%

“…Code hopping schemes based on spread spectrum systems have been studied [10]- [12]. One advantage of these code hopping schemes is code diversity [12].…”

Section: Ochmmentioning

confidence: 99%

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Synergy/Perforation Control for 16-QAM in Orthogonal Code Hopping Multiplexing

Moon

Kwon

Sung

2007

IEEE Trans. Veh. Technol.

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Orthogonal code hopping multiplexing (OCHM) is a statistical multiplexing scheme designed to accommodate a large number of allowable downlink channels in code division multiple access (CDMA) systems. However, OCHM may yield a worse bit error rate (BER) performance than the conventional CDMA systems due to code collisions. Therefore, a synergy/perforation operation, which is a control scheme for mapping code-colliding modulation symbols to specific constellation points on the I-Q plane, is needed to compensate for BER degradation, and this synergy/perforation operation should be defined separately with modulation types. Previously, synergy/perforation control schemes for quadrature phase shift keying (QPSK) and binary phase-shift keying (BPSK) have been proposed, but there has been no study of 16-quadratic-amplitude modulation (16-QAM) in OCHM. We propose two synergy/perforation control schemes for 16-QAM in OCHM and a log-likelihood ratio conversion scheme for 16-QAM in OCHM. The proposed control schemes are evaluated by an analytical approach and simulations and are compared to the previous scheme for QPSK modulation. We show that the proposed control scheme has a performance similar to that of QPSK modulation in terms of the mean synergy ratio for code-colliding modulation symbols and additional required E b /N 0 .

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Section: Ochmmentioning

confidence: 99%