Analytical Bit Error Rate Performance of DS-CDMA Ad Hoc Networks using Large Area Synchronous Spreading Sequences

The performance of large area synchronous (LAS) direct sequence code division multiple access (DS-CDMA) assisted ad hoc networks is investigated in the context of a single-hop infinite mesh of rectilinearly located ad hoc nodes. It is shown that LAS DS-CDMA exhibits a significantly better performance than the family of traditional spreading sequences used in a quasisynchronous DS-CDMA scenario having a low number of resolvable multipath components and a sufficiently high number of RAKE receiver branches. The benefits of LAS codes in ad hoc networks are multifold: (i) Their performance is noise-limited, rather than interference-limited, provided that the multipath and multi-user interference arrives within their interference free window. (ii) Under the same conditions LAS codes are robust against the ‘near–far’ effects imposed by ad hoc networks operating without base-station-aided power control, without accurate synchronisation and without implementationally complex interference cancellers

A VLSI architecture of JPEG2000 encoder

Copyright @ 2004 IEEEThis paper proposes a VLSI architecture of JPEG2000 encoder, which functionally consists of two parts: discrete wavelet transform (DWT) and embedded block coding with optimized truncation (EBCOT). For DWT, a spatial combinative lifting algorithm (SCLA)-based scheme with both 5/3 reversible and 9/7 irreversible filters is adopted to reduce 50% and 42% multiplication computations, respectively, compared with the conventional lifting-based implementation (LBI). For EBCOT, a dynamic memory control (DMC) strategy of Tier-1 encoding is adopted to reduce 60% scale of the on-chip wavelet coefficient storage and a subband parallel-processing method is employed to speed up the EBCOT context formation (CF) process; an architecture of Tier-2 encoding is presented to reduce the scale of on-chip bitstream buffering from full-tile size down to three-code-block size and considerably eliminate the iterations of the rate-distortion (RD) truncation.This work was supported in part by the China National High Technologies Research Program (863) under Grant 2002AA1Z142

Intrinsic electron-doping in nominal "non-doped" superconducting (La,Y)2_2CuO4_4 thin films grown by dc magnetron sputtering

The superconducting nominal "non-doped" $La_{1.85}Y_{0.15}CuO_4$ (LYCO) thin films are successfully prepared by dc magnetron-sputtering and in situ post-annealing in vacuum. The best $T_{C0}$ more than 13K is achieved in the optimal LYCO films with highly pure c-axis oriented T'-type structure. In the normal state, the quasi-quadratic temperature dependence of resistivity, the negative Hall coefficient and effect of oxygen content in the films are quite similar to the typical Ce-doped T'-214 cuprates, suggesting that T'-LYCO shows the electron-doping nature like known n-type cuprates, and is not a band superconductor as proposed previously. The charge carriers are considered to be induced by oxygen deficiency.Comment: 5 pages, 7 figure