Hirohito Suda

Analysis of wireless geolocation in a non-line-of-sight environment

We present an analysis of the time-of-arrival (TOA), time-difference-of-arrival (TDOA), angle-of-arrival (AOA) and signal strength (SS) based positioning methods in a non-line-of-sight (NLOS) environment. Single path (line-of-sight (LOS) or NLOS) propagation is assumed. The best geolocation accuracy is evaluated in terms of the Cramer-Rao lower bound (CRLB) or the generalized CRLB (G-CRLB), depending on whether prior statistics of NLOS induced errors are unavailable or available. We then show that the maximum likelihood estimator (MLE) using only LOS estimates and the maximum a posteriori probability (MAP) estimator using both LOS and NLOS data can asymptotically achieve the CRLB and the G-CRLB, respectively. Hybrid schemes that adopt more than one type of position-pertaining data and the relationship among the four methods in terms of their positioning accuracy are also investigated.

On time-of-arrival positioning in a multipath environment

Wireless geolocation in a multipath environment is of particular interest for wideband communications. The conventional approach makes use of first-arriving signals only. In this paper, we investigate whether and under what conditions processing multipath delays should enhance the positioning accuracy. The best achievable positioning accuracy is evaluated in terms of the Cramer-Rao low bound (CRLB) and the generalized-CRLB (G-CRLB), depending on whether prior statistics of non-line-sight (NLOS) induced errors are available. We then show that such prior statics are critical to the accuracy improvement when the multipath delays are processed. Furthermore, the degree of accuracy enhancement depends on two major factors: the strength of multipath components and the variance of NLOS induced errors. The corresponding positioning receivers are also discussed. In previous work (Y. Qi and H. Kobayashi, Proc. 2002 IEEE Int. Conf. on Acoustic Speech and Sig. Proc., pp. 2473-2476, 2002, and Proc. IEEE Vehicle Tech. Conf., pp. 285-288, 2002), we developed an analysis of the time-of-arrival (TOA) positioning method in an NLOS environment, assuming single path propagation. The main results obtained there are extended and applied to the multipath case in this paper.

Radio access network design concept for the fourth generation mobile communication system

The growth in mobile multimedia services will accelerate over the next decade. This paper discusses service aspects and system requirements for the fourth generation mobile communication (4G) system that will allow us to provide higher-speed communications and deal with user demand in the next decade. This paper also proposes a new radio access network (RAN) structure suited to the 4G system. The principles of the proposed cluster-cellular RAN are localized handover processing and horizontal structure. The advantages of the proposed RAN are also discussed.

Multistage recursive interleaver for turbo codes in DS-CDMA mobile radio

A multistage recursive block interleaver (MIL) is proposed for the turbo code internal interleaver. Unlike conventional block interleavers, the MIL repeats permutations of rows and columns in a recursive manner until reaching the final interleaving length. The bit error rate (BER) and frame error rate (FER) performance with turbo coding and MIL under frequency-selective Rayleigh fading are evaluated by computer simulation for direct-sequence code-division multiple-access mobile radio. The performance of rate-1/3 turbo codes with MIL is compared with pseudorandom and S-random interleavers assuming a spreading chip rate of 4.096 Mcps and an information bit rate of 32 kbps. When the interleaving length is 3068 bits, turbo coding with MIL outperforms the pseudorandom interleaver by 0.4 dB at an average BER of 10/sup -6/ on a fading channel using the ITU-R defined Vehicular-B power-delay profile with the maximum Doppler frequency of f/sub D/ = 80 Hz. The results also show that turbo coding with MIL provides superior performance to convolutional and Reed-Solomon concatenated coding; the gain over concatenated coding is as much as 0.6 dB.