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Relative Performance of BPSK and QPSK in the Presence of Complex Multiuser CDMA Interference

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Abstract

In a typical mobile communications channel, the multiple accessinterference (MAI) experienced by any user in a multiuser CDMA systemwill be complex-valued due to independent phase offsets betweensignals received from different users. In addition, complex spreadingcodes may also be employed, in which case MAI is complex-valued evenwithout phase offsets. This paper shows that complex MAI substantiallyalters the single-user relationship between BPSK and QPSK modulation,in which QPSK offers twice the bandwidth efficiency of BPSK withoutsacrificing BER versus E b /N 0 performance. Itis shown bothanalytically and through simulations that it is possible to adjustsystem parameters to achieve identical system bandwidth efficiency andBER performance in BPSK and QPSK systems using the conventionaldetector. The performance of the well-known successive interferencecanceller and decorrelating detector are also examined.

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Authors and Affiliations

  1. Centre for Wireless Communications, 20 Science Park Road, #02-34/37, TeleTech Park, Singapore, 117674

    Teng Joon Lim & Lars K. Rasmussen

  2. Oki Techno Centre Singapore, 20 Science Park Road, #02-06/10, TeleTech Park, Singapore

    Hiroki Sugimoto

Authors
  1. Teng Joon Lim
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  2. Lars K. Rasmussen
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  3. Hiroki Sugimoto
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Lim, T.J., Rasmussen, L.K. & Sugimoto, H. Relative Performance of BPSK and QPSK in the Presence of Complex Multiuser CDMA Interference. Wireless Personal Communications 13, 237–256 (2000). https://doi.org/10.1023/A:1008974119760

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  • DOI: https://doi.org/10.1023/A:1008974119760