2013年4月19日星期五

Collect and plot data from an instrument in real time



Collect and plot data from an instrument in real time

Controlling Instruments and Serial Devices with MATLAB and Simulink [Webinar]


Serial Interface (RS-232 and RS-485) and MATLAB

2012年12月15日星期六

DFTS-OFDM for uplink transmission in LTE (ZZ)

Today multi-carrier transmission and OFDM are means to allow for very high overall transmission bandwidth while still being robust to signal corruption due to radio-channel frequency selectivity. However, a drawback of OFDM modulation, as well as any kind of multi-carrier transmission, is the large variations in the instantaneous power of the transmitted signal. Such power variations imply a reduced power-amplifier efficiency and higher power-amplifier cost. This is especially critical for the uplink, due to the high importance of low mobile-terminal power consumption and cost. Several methods have been proposed on how to reduce the large power variations of an OFDM signal. However, most of these methods have limitations in terms of to what extent the power variations can be reduced. Furthermore, most of the methods also imply a significant computational complexity and/or a reduced link performance. Thus, there is an interest to consider also wider-band single-carrier transmission as an alternative to multi-carrier transmission, especially for the uplink, i.e. for mobile-terminal transmission. One of such single-carrier transmission scheme can be implemented using DFT-spread OFDM

DFT-spread OFDM (DFTS-OFDM) is a transmission scheme that can combine the desired properties for uplink transmission i.e. : 
• Small variations in the instantaneous power of the transmitted signal (‘single carrier’ property). 
• Possibility for low-complexity high-quality equalization in the frequency domain. 
• Possibility for FDMA with flexible bandwidth assignment. 

Due to these properties, DFTS-OFDM has been selected as the uplink transmission scheme for LTE, which is the long-term 3G evolution.

DFTS-OFDM signal generation
PAR distribution for OFDM and DFTS-OFDM, respectively.

More detail can be accessed from here:
http://wirelesscafe.wordpress.com/2009/04/07/what-is-single-carrier-fdma-sc-fdma/

2012年12月3日星期一

How to calculate/plot confidence interval

http://people.richland.edu/james/lecture/m170/ch08-int.html

2012年10月8日星期一

Matlab "Out of Memory"

If you are using 32 bits Window XP, Vista and Window 7, the default memory loaded in Matlab is 2GB.

You can try to extend it by using the following:

1) Run the command in administrator:
2) > BCDEdit /set increaseuserva 3072

Restart the computer and matlab.

2012年9月4日星期二

Channel estimation in MIMO-OFDM

Wireless LAN Comes of Age:Understanding theIEEE 802.11n Amendment
by Thomas Paul and Tokunbo Ogunfunmi

published in IEEE circuits and systems magazine
Tutorial for WLAN design (including 802.11n, 802.11ac)

Check Section III. 2.5


Also, some tutorial on least square estimation techniques, which is used to derive the results in channel estimation.

http://www.stat.math.ethz.ch/~geer/bsa199_o.pdf