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access icon free Two-dimensional spreading scheme employing 2D orthogonal variable spreading factor codes for orthogonal frequency and code division multiplexing systems

© The Institution of Engineering and Technology
Received 12/04/2012, Accepted 24/11/2012, Revised 31/10/2012, Published

Future 4G systems require transmission of richer multimedia services which inevitably implies an increase in data rate. Orthogonal frequency and code division multiplexing (OFCDM) technique has shown promising results in achieving a high data rate while simultaneously combating multipath fading. OFCDM is an amalgamation of orthogonal frequency division multiplexing and two-dimensional (2D) spreading. 2D spreading helps to achieve diversity gains in both time and frequency domains. The present OFCDM systems employ 1D orthogonal variable spreading factor (OVSF) codes to achieve the required 2D spreading in code multiplexed channels. However, 2D OVSF codes have better correlation properties in comparison to 1D OVSF codes. Motivated by this principle, the authors propose a spreading scheme for OFCDM systems using 2D OVSF codes. The spreading scheme is designed to increase the system throughput and reduce multi-code interference. Here, the authors study the OFCDM system performance using the proposed spreading scheme in a multipath fast fading channel with varying spreading factors in both time and frequency domains. The results are compared with the existing OFCDM systems using 1D OVSF codes.

Inspec keywords: multipath channels; fading channels; time-frequency analysis; 4G mobile communication; orthogonal codes; OFDM modulation; channel coding; interference suppression

Other keywords: two-dimensional spreading scheme; 1D orthogonal variable spreading factor codes; frequency domains; code multiplexed channels; time domains; two-dimensional orthogonal variable spreading factor codes; orthogonal frequency and code division multiplexing systems; multicode interference reduction; OFCDM technique; multipath fast fading channel; 1D OVSF codes; 4G systems; 2D OVSF codes; multimedia services

Subjects: Codes; Mobile radio systems; Electromagnetic compatibility and interference; Mathematical analysis; Multiple access communication

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