Reduced-complexity transmit-beamforming codebook search algorithm

Abstract

A two-stage reduced-complexity index search algorithm is proposed for finding the best vector in the codebook of quantised equal gain transmission based multiple-input multiple-output arrangements. When the number of transmit antennas is more than three, the normalised complexity is halved while maintaining the same symbol error rate as the benchmark.Introduction: The de facto fourth generation (4G) wireless systems have encompassed codebook (CB) based closed-loop multiple-input multiple-output (MIMOs) [1]. Quantised equal gain transmission (QEGT) imposes less stringent transmit amplifier linearity requirements than other MIMOs. Similar to other CB based MIMO schemes, QEGT requires a substantially increased CB size, as the number of transmit antennas increases. Hence, employing an efficient CB index search algorithm becomes essential. A single-user MIMO-OFDM system relying on transmit beamforming (BF) and using M t transmit as well as M r receive antennas is considered. The system model and QEGT CB design are the same as in [2]. This allows the direct contrasting of our efficient search to that in [2]. The matrix of channel impulse responses (CIR) H [ C Mr×Mt is assumed to have IID complex-valued Gaussian elements having a unit variance. The CIR is assumed to be perfectly estimated at the downlink receiver. Given the transmitted symbol of rank one s [ C, the received symbol x [ C is described by

Characterization of electrodeposited bismuth–tellurium nanowires and nanotubes

“…Bi 2 Te 3 nanotubes have been synthesized previously by different chemical routes, such as hydrothermal synthesis [23], solvothermal synthesis [24,36] and a low-temperature aqueous chemical method [37], galvanic displacement reaction of Ni nanowires [38]. A previous work from the present authors' group presents evidence of fabricating BiTe nanotubes via electrodeposition [39]; although no characterization studies were reported.…”