Time of Arrival Estimation in Probability-Controlled Generalized CDMA Systems
نویسندگان
چکیده
In recent years, more and more wireless communications systems are required to provide also a positioning measurement. In code division multiple access (CDMA) communication systems, the positioning accuracy is significantly degraded by the multiple access interference (MAI) caused by other users in the system. This MAI is commonly managed by a power control mechanism, and yet, MAI has a major effect on positioning accuracy. Probability control is a recently introduced interference management mechanism. In this mechanism, a user with excess power chooses not to transmit some of its symbols. The information in the nontransmitted symbols is recovered by an error-correcting code (ECC), while all other users receive a more reliable data during these quiet periods. Previous research had shown that the implementation of a probability control mechanism can significantly reduce the MAI. In this paper, we show that probability control also improves the positioning accuracy. We focus on time-of-arrival (TOA)-based positioning systems. We analyze the TOA estimation performance in a generalized CDMA system, in which the probability control mechanism is employed, where the transmitted signal is noncontinuous with a symbol transmission probability smaller than 1. The accuracy of the TOA estimation is determined using appropriate modifications of the Cramer-Rao bound on the delay estimation. Keeping the average transmission power constant, we show that the TOA accuracy of each user does not depend on its transmission probability, while being a nondecreasing function of the transmission probability of any other user. Therefore, a generalized, noncontinuous CDMA system with a probability control mechanism can always achieve better positioning performance, for all users in the network, than a conventional, continuous, CDMA system.
منابع مشابه
Bit Error Performance for Asynchronous Ds Cdma Systems Over Multipath Rayleigh Fading Channels (RESEARCH NOTE)
In recent years, there has been considerable interest in the use of CDMA in mobile communications. Bit error rate is one of the most important parameters in the evaluation of CDMA systems. In this paper, we develop a technique to find an accurate approximation to the probability of bit error for asynchronous direct–sequence code division multiple–access (DS/CDMA) systems by modeling the multipl...
متن کاملBlind space–time joint channel and direction of arrival estimation for DS-CDMA systems
A blind space–time joint channel and direction of arrival (DoA) estimation method is proposed for DS-CDMA systems. The new method employs a linear antenna array and requires only the signature sequence and timing of the desired user to blindly estimate the channel and the DoA parameters. Two blind algorithms that exploit antenna arrays are also proposed for enhancing the channel estimates. Simu...
متن کاملCdma Wireless Location
Code Division Multiple Access (CDMA) systems and wireless location are studied in this paper. For CDMA systems, Maximal Ratio Combining (MRC) is applied for designing the RAKE receiver, and channel estimation is utilized to determine unknown channel gains. Time of Arrival (TOA) method is presented to estimate user’s location. The improvement on bit error rate (BER) and wireless location using a...
متن کاملReverse Link Outage Probabilities of Multicarrier CDMA Systems with Beamforming in the Presence of Carrier Frequency Offset
The outage probability of reverse link multicarrier (MC) code-division multiple access (CDMA) systems with beamforming in the presence of carrier frequency offset (CFO) is studied. A conventional uniform linear array (ULA) beamformer is utilized. An independent Nakagami fading channel is assumed for each subcarrier of all users. The outage probability is first investigated under a scenario wher...
متن کاملSpace-doppler Parameter Estimation for Space-time-doppler Reception in Time-varying Multipath Ds-cdma Systems
In this paper we propose a joint space-Doppler parameter estimation algorithm for fast-fading multipath DS-CDMA communication systems. The Doppler shifts induced by the relative motion between the transmitter and the receiver, together with the associated direction-of-arrival (DOA), are jointly estimated by a semi-blind subspace-type method. The Doppler effect is successfully eliminated by a sp...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- EURASIP J. Adv. Sig. Proc.
دوره 2008 شماره
صفحات -
تاریخ انتشار 2008