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We consider the problem of cognitive code-division channelization (simultaneous power and code-channel allocation) for secondary transmission links co-existing with an unknown primary code-division multiple-access (CDMA) system. We first develop a blind primary-user identification scheme to detect the binary code sequences (signatures) utilized by primary users. To create a secondary link we propose...
The interference reduction capability of cell sectoring and power control algorithms have been considered separately as means to decrease the interference in code division multiple access (CDMA) cellular systems. In this paper, we present rotatable equal sectoring (RES) method for CDMA cellular systems in a 2D urban environment. In this method, the equal sectors of the base stations are rotating together...
In this paper, we propose smart step closed-loop power control (SSPC) algorithm in a direct sequence-code division multiple access (DS-CDMA) receiver in the presence of frequency-selective Rayleigh fading. This receiver consists of three stages. In the first stage, with constrained least mean squared (CLMS) algorithm, the desired users' signal in an arbitrary path is passed and the inter-path interference...
The cooperative CDMA system proposed in this paper performs two phases of transmission. In phase I, each user node transmits its own information which is received by the base station (BS) as well as the other user nodes; in phase II, each partner node relays a processed version of the information received in the previous phase. Two iterative detectors are developed at the B S to combat multiple access...
A novel beamspace eigen-fllter 2D Rake receiver for DS-CDMA communication system is proposed in this paper. The proposed algorithm's performance is very close to the optimal space-time algorithm and it can outperform the beamspace-frequency algorithm. Another advantage is that the proposed algorithm is computationally more efficient in comparing with the beamspace-frequency algorithm.
Combat multiple access interference(MAI) and near-far effect, to some degree, BP neural network can be better suppression interference, because of its use of the least squares method, prone to local minimum. In this paper, instead of using the MMSE algorithm for least squares and the addition of a new kind of constraints, and gain iterative formula of BP neural network blind multiuser detection algorithm,...
The interference reduction capability of antenna arrays, base station assignment and the power control algorithms have been considered separately as means to increase the capacity in wireless communication networks. In this paper, we propose base station assignment method based on minimizing the transmitter power (BSA-MTP) technique in a direct sequence-code division multiple access (DS-CDMA) receiver...
Multipath, Multiple-Access-Interference (MAI) and Near-Far effect are three main influences on the performance of CDMA-based communication and navigation systems. A great deal of research has been conducted to develop advanced signal processing algorithms and novel receiver structures useful for mitigation of these effects in mobile land wireless communication systems, such as UMTS. One effect way...
This paper discusses a multi-user access technique for Ultra-wideband Impulse Radio (UWB-IR) system in energy detection receiver. The UWB-IR system is modulated by On-Off shift Keying (OOK). As multi-users access scheme, the Code Division Multiple Access (CDMA) using the Optical Orthogonal Code (OOC) sequence is adopted. The integral interval and the sample energy threshold value are optimized to...
In the CDMA-based fingerprinting scheme, a fingerprint sequence is composed of two kinds of spread spectrum sequences generated from DCT basic vectors and PN sequences. In this study, the DCT basic vectors are randomly permuted in order to reduce the interference among colluders' fingerprint sequences, which effect is similar to the interleaver used in Turbo codes. Our experimental results reveal...
Interference cancellation (IC) is an effective and easy implemented technology in the multi-user system. Previous studies demonstrate the principles of IC and IC process which show a great improvement in the system capacity with IC. However, no research has focused on the IC system's capacity domain by giving an accurate formula. This article carries on the theoretical analysis of CDMA reverse link...
Robust adaptive multiuser detection schemes are developed for direct-sequence code-division multiple-access (DS-CDMA) multipath frequency-selective fading channels. Multiple access interference (MAI) and intersymbol interference (ISI) are presented in identical format in the expanded signal subspace, which provides convenience for symbol-by-symbol multiuser detection. The proposed multiuse detectors...
Smart antennas have received increasing interest due to its capability for improving the performance of wireless radio systems. In this work we studied the throughput maximization in a CDMA 1xEV-DO cellular system when a smart antenna array is implemented. We focus in the downlink of the CDMA cellular system and consider a packet data direct-sequence code division multiple access (DS-CDMA). We show...
Conventionally, an interweave cognitive radio (CR) system can be developed based on the assumption of spectrum sharing between a wide-band CR system and some narrow-band primary systems. In this paper, we explode this assumption by constructing an interweave CR system using a hierarchical wide-band two-dimensional (2D) spread multi-carrier directed-sequenced code division multiple access (MC-DS-CDMA)...
This paper discusses essential implementation aspects of simple amplify-and-forward type repeaters from the radio network planning point of view. Different RF-repeater configurations are assessed through numerical analysis and field measurements in WCDMA network. The target of this paper is to show the important factors regarding the repeater deployment, which have significant impact on the overall...
In this paper we analyze how femtocell base stations (FBS) cause interference in the receivers of user terminals connected to macro base stations. A coverage hole around a FBS appears when closed access strategies are used, i.e. when only authorized users can access the FBS, and when the FBS shares the same or a portion of the macrocell frequency channel. At the cell borders of a macrocell the coverage...
In this paper, we propose user grouping algorithms to provide power minimization in grouped STBC MC-CDMA systems. Depending on the channel fading conditions, power control is utilized to minimize the total transmitted power under a BER constraint. When the allocation is performed without a fair data rate requirement, we provide the optimal solution to the minimization problem. However when some fairness...
In this paper, we propose smart step closed-loop power control (SSPC) algorithm in a direct sequence-code division multiple access (DS-CDMA) receiver in the presence of frequency-selective Rayleigh fading. This receiver consists of three stages. In the first stage, with conjugate gradient (CG) adaptive beamforming algorithm, the desired users' signal in an arbitrary path is passed and the inter-path...
Attention to resource allocation algorithms for multiservice Code Division Multiple Access CDMA networks has focused on algorithms maximizing the uplink aggregate throughput. In the present paper we address the problem of the joint power and spreading factor (SF) allocation to non real-time (NRT) terminals on the uplink, once real time constraints are satisfied. An optimal algorithm is proposed, that...
In this paper, we analyze the interference distribution and gain of beamforming in closed access femtocells in downlink of a two-tier HSDPA cellular network. We show through simulations that indoor femtocell deployment leads to a dominant interferer scenario. According to results even simple null steering method based on the scarce codebook of HSDPA transmit diversity mode 1 can be beneficially applied...
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