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This paper develops a new hidden pilots based algorithm for the carrier frequency offset (CFO) estimation of multicarrier DS-CDMA (MC-DS-CDMA) systems. Multiple CFO of different users in the uplink of MC-DS-CDMA systems may violate the orthogonality among subcarriers and induce both inter-carrier interference (ICI) and inter-user interference (IUI). This algorithm utilizes mutually orthogonal hidden...
According to the advantages of chaotic binary sequences, this paper presents a method of generating advanced hyperchaotic complex binary sequences called oversampled Ikeda map (IM) sequences (OIMS) by oversampling IM. To choose proper oversample rate, the relation between OIMS?? performance and adopted rates is analyzed via merit factor function of auto-correlation, mean-square cross-correlation (MSCC)...
In this paper, we propose a forcing mutation scheme from GA to perform a forcing mutation evolutionary multiuser detector (FME-MUD) and to largely reduce computational complexity. Simulation results show that with a few generations Gn=6, the proposed FME-MUD scheme outperforms the conventional genetic algorithm based multiuser detector (GA-MUD) especially at heavy system load.
The Constant Modulus Algorithm (CMA) criterion has been proved to possibly capture the interference instead of the desired user. To solve this problem, linearly constrained constant modulus algorithm (LCCMA) was proposed in paper, but LCCMA can not correct the phase error of the received signal. In this paper, a modified linearly constrained constant modulus algorithm (MLCCMA) for DS-CDMA system multi-user...
This paper presents the design of using a simple mixer circuit, constructed with Schottky diodes as the nonlinear device, to generate the intermodulation (IM) products for predistortion of high-power amplifiers (HPAs) in the base stations of cellular mobile systems. The design has a simple structure and requires no external dc bias voltage. A complex polynomial is used to model the characteristic...
Recently, multi-carrier code division multiple access (MC-CDMA) has been attracting much attention as a broadband wireless access technique for the next generation mobile communications systems. Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can take advantage of the channel frequency-selectivity and improve the average bit error rate (BER) performance...
The slotted ALOHA based random access faces the low throughput and long access delay problems when used in macro cell CDMA systems. This paper proposes the spread ALOHA based random access scheme as a solution. In our physical layer model, we studied the impact of multi-path on conflict interval and the multiple access interference (MAI) from both the traffic channels and the request channel. Based...
We propose a contention based medium access control (MAC) protocol which will extend traditional single channel wireless network such as IEEE 802.11 distributed coordination function (DCF) to be used in multiple code channels direct sequence code division multiple access (DS-CDMA) wireless networks. The DCF is a special case in our proposed MAC protocol. We assume the system exist a maximum allowable...
A modified Welch-Costas (MWC) code family for the spectral-amplitude coding (SAC) optical code-division multiple-access (OCDMA) system is proposed. On utilizing the property of the MWC codes, more compact coder/decoders can be realized via waveguide and fiber gratings. In addition, this system has a superior performance as compared to the previous Walsh-Hadamard coded OCDMA system.
This paper considers blind chip rate estimation of direct sequence spread spectrum (DS-SS) signals in multirate and multiuser direct-sequence code division multiple accesses (DS-CDMA) in channels having slow flat Rayleigh fading plus additive white Gaussian noise. Channel impulse response is estimated by a subspace method, and then the chip rate of each signal is obtained using number of zero crossing...
For the development of future wireless communication systems, an extremely spectrum-efficient transmission technology is required. Orthogonal frequency division multiplexing (OFDM) and multi-carrier code division multiple access (MC-CDMA) have been attracting much attention. The use of multiple-input multiple-output (MIMO) transmission is essential to achieve a very high speed data transmission with...
TD-SCDMA cell search is performed in three scenarios: downlink guide slot (DwPTs) position search, downlink synchronization code (SYNC_DL) position search and frame synchronization control. A fast method for every scenarios of downlink cell search in TD-SCDMA is proposed. Based on characteristics of frame and slot structure in TD-SCDMA, power-matching stencil method is used to find the position of...
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