It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >

On the capacity of a cellular CDMA system

Quasisynchronous (QS) Code Division Multiple Access (CDMA) is currently being considered for a variety of wireless applications and services because QS-CDMA enables information transmission with a good quality of service. In this paper, for M-ary signaling, the Symbol Error Rate (SER) performance of QS-CDMA communication system with a maximal ratio combiner (MRC) over frequency-selective, time-nonselective multipath Generalized Gamma (GG3) fading channels is derived not only for any deterministic spreading sequences but also for any chip-limited chip waveforms, and it is investigated for Rectangular, Half-Sine, and Raised-Cosine chip waveforms by means of numerical and simulation results. Numerical and simulation results show that the performance of QS-CDMA is as good as or slightly better than synchronous CDMA (S-CDMA) when the maximum quasisynchronous delays do not need to be less than some specific values depending on the path power scattering. With this flexibility of quasisynchronous delays, both the transmitter and receiver complexities are reduced as quasisynchronous communication is a challenging task for researchers. Additionally, since not only the spreading sequences but also the partial autocorrelation functions of the chip waveform are influential on the performance of multipath QS-CDMA, a measure, Partial Power Ratio (PPR) is defined based on these partial autocorrelation functions in order to select or design a chip waveform for quasisynchronous communication. Furthermore, results show that QS-CDMA using the chip waveform whose PPR is greater has better performance.

Symbol Error Rate Performance of QS-CDMA over Frequency Selective Time Non-Selective Multipath Generalized Gamma Fading Channels

In this work, Symbol Error Rate (SER) performance of Quasi Synchronous (QS) CDMA system over frequency selective time non-selective multipath Nakagami-m fading channels is obtained for M-ary Phase Shift Keying (MPSK) signaling, deterministic spreading sequences and different chip waveforms with a maximal ratio combiner (MRC) at the receiver. We show that the performance of QS-CDMA will be as good as or slightly better than the synchronous performance of Direct Sequence (DS) CDMA when the maximal allowed time offset does not need to be less than 0.2 for Rectangular and 0.7 for Raised-Cosine chip waveform. With this flexibility of maximal allowed time offset, the complexity of synchronization task is reduced.

Analysis of QS-CDMA over Frequency Selective Time Non-Selective Nakagami-m Fading Channels

In this study, the performance of Quasisynchronous DS-CDMA (QS-CDMA) communication system with a maximal ratio combiner (MRC) over a frequency selective time non-selective multipath Generalized Gamma (GG) fading channel is derived for not only any deterministic spreading sequence but also any chip-limited chip waveform Numerical and simulation results show that the performance of QS-CDMA is as good as or slightly better than synchronous CDMA (S-CDMA) when the maximum quasisynchronous delays do not need to be less than some specific values depending on the path power scattering With this flexibility of quasisynchronous delays for the better performance, both the transmitter and receiver complexity is reduced as quasisynchronous communication is a challenging task for researchers Lastly, a measure, Partial Power Ratio (PPR), is defined based on the partial autocorrelation functions, to select or design a chip waveform for quasisynchronous communication Results show that QS-CDMA using the chip waveform whose PPR is greater, has better performance

Analysis of QS-CDMA for M-ary Signaling over Frequency Selective Generalized Gamma Slowly Fading Channels

In this paper the BER performance of a generalized quasi-synchronous code division multiple access (QS-CDMA) system over a multipath fading channel is evaluated. The maximal ratio combining (MRC) and the selection diversity reception are used in the system. The results indicate that significantly better performance is available by using new spreading codes than using conventional pseudonoise codes.

Bi Qi Long

Papers

The analysis of a generalized QS-CDMA system over a multipath Rayleigh fading channel