Abstract
In this paper, we derive analytical expressions to assess the performance of Time Division Duplexing (TDD) Direct Sequence-Code Division Multiple Access (DS-CDMA) systems with coherent bi-dimensional (2D) Rake receivers. Considering either hexagonal macrocellular and microcellular cross-shaped networks, we propose and evaluate different approaches to model the effects of the intercellular multiple access interference (MAl) on the performance of DS-CDMA systems with 2D Rake receivers. These results are then used on the performance comparison between coherent and optimum 2D Rake receivers. It is shown that soft handoff allows gains of 2 dB in the Signal-to-Interference-plus-Noise-Ratio (SINR) at the 2D Rake receiver output. Simulation results, ratified by theoretical upper bounds, show that the dynamic time slot allocation schemes allow considerable increase of the SINR at the receiver output with a concomitant improvement on the throughput.
Highlights
Considering a multitude of parameters, it has been concluded that the time variant and irregular spatial temporal channel characteristics have a strong influence on the performance of Time Division Duplexing (TDD) Direct Sequence-Code Division Multiple Access (DS-CDMA) systems with 2D RAKE receivers [I]
Considering a multitude of parameters, it has been concluded that the time variant and irregular spatial temporal channel characteristics have a strong influence on the performance of TDD DS-CDMA systems with 2D RAKE receivers [I]
it is assumed the following: (i) a receiver with M antennas and P taps per antenna whose response is obtained by the Maximum Ratio Combining (MRC) or coherent solution; (ii) the MAl is modeled as a flat power spectrum density and all received signals have the same average power; (iii) the fading is independent in all antennas (i.e. M[)=M)
Summary
Considering a multitude of parameters, it has been concluded that the time variant and irregular spatial temporal channel characteristics have a strong influence on the performance of TDD DS-CDMA systems with 2D RAKE receivers [I]. It is presented the steps to numerically estimate the SINR at the 2D Rake receiver output. Where hu is the M column vector that models the arrival at the antenna array of 1-th multi path of the k-th user. Where Cf.u is a complex random variable (RV) that models the channel gain for the l-th path of k-th user If it is assumed an array with M correlated antennas. Where Uk.hm is a complexRV that models the channel gain for k-th user at the I-th path at the m-th antenna element. The spatial covariance matrix (dimension MP by MP) of interference plus-noise at the target cell can be stated as: R= KNI Bs. vhere K is the number of MSs physically located in each of one of NBS hexagonal BSs. and the Additive White.
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