Simulation of a Multiple Input Multiple Output (MIMO) system using various Space Time Coding (STC) techniques in LabVIEW
(Undergraduation Major Project Thesis)

Click Here to  view the top level graphical user interface of the MIMO Simulation Model.

 ==============================================================================================

Download the stand-alone software developed as a part of the undergraduate thesis.

Required: LabVIEW Runtime Engine 2009 or later

MIMO Simulation Model.rar MIMO Simulation Model.rar
Size : 2.351 Kb
Type : rar

 ==============================================================================================

Showing category "Meetings" (Show all posts)

Solutions / Workarounds / Tweaks

Posted by Ujjval Shah on Wednesday, April 22, 2009, In : Query/Problem/Solution 
Solutions

The solutions provided here mainly discuss how to decrease the processing time. It also addresses some of the issues listed in the previous section.

Reentrant VIs

LabVIEW is a data flow programming tool. It can execute data independent codes in parallel if programmed in such a way. In the simulation there are several instances where a same chunk of code is repeated a number of times. This code is defined as a VI and is called every time the main code wants to utilize it. However by def...

Continue reading ...
 

Simulation Problems and Challenges - A summary

Posted by Ujjval Shah on Wednesday, April 22, 2009, In : Query/Problem/Solution 

Large processing time

The simulation model aims in finding the BER value for various SNR values and plots them on a chart. The processes involving in finding a BER value for a single SNR value are random generation of a large number of symbols, modulation of these symbols using one of the modulation schemes such as PSK, MIMO- STC scheme encoding, generating and applying a Rayleigh flat fading profile to it, generating and adding AWGN to it, decoding, demodulation and BER calculation. Each of...


Continue reading ...
 

SMUX BER vs. SNR curves

Posted by Ujjval Shah on Wednesday, April 22, 2009, In : Simulation 

Continue reading ...
 

MIMO MISO SIMO SISO BER vs. SNR curves

Posted by Ujjval Shah on Wednesday, April 22, 2009, In : Simulation 

Continue reading ...
 

RX Diversity BER vs. SNR curves

Posted by Ujjval Shah on Wednesday, April 22, 2009, In : Simulation 

Continue reading ...
 

SC, MRC BER vs. SNR curves

Posted by Ujjval Shah on Wednesday, April 22, 2009, In : Simulation 

Continue reading ...
 

2x1, 2x2 Alamouti BER vs. SNR curve

Posted by Ujjval Shah on Wednesday, April 22, 2009, In : Simulation 

Continue reading ...
 

GUI - The Front Panel

Posted by Ujjval Shah on Wednesday, April 22, 2009, In : Simulation 

Continue reading ...
 

Generalized Complex Orthogonal Space Time Block Codes

Posted by Ujjval Shah on Tuesday, April 14, 2009, In : Theory 
Some important results:

  1. Rate one generalized complex orthogonal designs do not exist for more than two transmit antennas
  2. The rate of a generalized complex orthogonal design cannot exceed R = 3/4 for more than two antennas
  3. Rate half, R = 0.5, generalized complex orthogonal designs exist for any number of transmit antennas 
  4. For a generator matrix for a given rate and number of antennas, a generator matrix of same rate for number of tranmist antennas less by one can be obtained by simply removin...

Continue reading ...
 

Selection Combining

Posted by Ujjval Shah on Tuesday, April 14, 2009, In : Query/Problem/Solution 
Selection combining involves the process of selecting one of the multiple receiver antennas and thus the communication channel which is least affected by noise.

The question: Is it possible to use this technique if there are more than two transmitter antennas?

My instinct says no, however i need to find out the answer and the reason for it as well.

------------------
edited on 22nd April

well the answer is yes as well as know.
for STBC you need to lock into one receiver antenna only during the tran...
Continue reading ...
 

Spatial Multiplexing

Posted by Ujjval Shah on Friday, April 3, 2009, In : Theory 
Till now most of the concentration was on diversity gains achieved by using both transmit and receive antennas in a multiple-input multiple-output (MIMO) channel. However, multiple transmit antennas can be utilized to achieve other goals as well. A higher capacity and as a result a higher transmission rate is possible by increasing the number of transmit antennas. Assume a MIMO channel with equal number of transmit and receive antennas. Then in a rich scattering environment the capacity incre...

Continue reading ...
 

Alamouti Encoding with RX Diversity (MRC), BER Curves

Posted by Ujjval Shah on Saturday, March 28, 2009, In : Simulation 
The following result is for Alamouti Encoding with RX diversity using Maximal Ratio Combining technique at the Recevier

Following curves are the expected theoretical curves for various different TX and RX antennas.
The dotted curve for Na=4 is the curve to be compared with the above simulated curve.

Following is a quick comparison of all the three curves simulated till now:



Continue reading ...
 

RX Diversity

Posted by Ujjval Shah on Saturday, March 28, 2009, In : Theory 
RX Diversity means to have multiple antennas at the receiver.

There are basically three types of method to obtain RX Diversity:

  1. Selection Combining (SC): Here the receiver selects the best branch of all the receiver antennas and decodes the signal coming from that antenna. It is suboptimal and doesnt utilizes the energy of the signals from the other antennas.
  2. Maximal Ratio Combining (MRC): Here, the limitation of the SC technique is removed. In MRC, signals from all the antennas are weighted app...

Continue reading ...
 

UpConversion DownConversion Effect

Posted by Ujjval Shah on Tuesday, March 24, 2009, In : Simulation 
How does the inclusion of upconversion and downconversion affect the simulation results and upto what extent do they affect? 

As of now it is observed that for a set of same given symbol rate, samples per symbol, no of message symbols and other parameters the BER curves for the simulation using upconversion and downconversion and the one without using them are almost the same.



Continue reading ...
 

BER Curves for Alamouti scheme, high symbol rate

Posted by Ujjval Shah on Tuesday, March 24, 2009, In : Simulation 
As mentioned in previous posts, those curves were plotted at a symbol rate varying from 2-10Hz.
The published ones are plotted at 2bits/sec ie 1symbol/sec for QPSK. 

In all the curves shown till now, none of them match exactly to the published ones.

However it is observed that as the symbol rate is gradually increased, the simulated curve tends to become more and more similar to the published ones.

Consider following values:
symbol rate =500
no of samples per symbol =8
no of symbols =5k
doppler ...

Continue reading ...
 

BER Curves for Alamouti scheme, smoothed out

Posted by Ujjval Shah on Wednesday, March 18, 2009, In : Simulation 
The BER curves in the previous posts were plotted with the Fading and AWGN profile varying with each iteration and Eb/No value. Hence the graph had abrupt changes when the channel used to suddenly dive deep blotting out the signal, thus making the comparison for various Eb/No value difficult. Moreover a number of iterations had to be taken and mean was required to find out to get the most suitable reading; this resulted into lot of compuatational time.

Hence to avoid this a constant fading pro...

Continue reading ...
 

BER Curves for Alamouti scheme

Posted by Ujjval Shah on Monday, March 16, 2009, In : Simulation 
The BER curves donot follow exactly as per the ones published in the book i am referring to, however they do resemble them. moreover the performance after using alamouti scheme does increases but not significantly as per the book. i have attached the pics of simulated curves. they were taken with 3.5K no of symbols, 10Hz symbol rate, 1 Hz doppler spread, 8 samples per symbol and mean of 20 iterations per SNR value. These values gives a very good result but the time taken for it outrageously l...

Continue reading ...
 

Alamouti Encoding-Decoding 2

Posted by Ujjval Shah on Sunday, March 8, 2009, In : Simulation 
The simulation is complete.
As discussed in previous post, the entire simulation of a siso and mimo (with alamouti scheme) has been done.

Entire simulation is done for QAM Modulation. But the same can be realised for other modulation schemes too as only the values of the complex symbols (values I and Q) are going to change with modulation scheme and the Alamouti encoding remaining constant.

Two major impairments are included in the simulation- The Additive White Guassian Noise (AWGN) and Rayleig...

Continue reading ...
 

Alamouti Encoding-Decoding

Posted by Ujjval Shah on Sunday, March 1, 2009, In : Query/Problem/Solution 
Previously, i had already developed a code to encode complex constellation symbols into alamouti codes for two transmit antennas.

For the decoding process at the receiver (only one antenna currently) i am using the maximum likelihood receiver (mlr) algorithm for finding the original transmitted symbols. To find the advantage of using alamouti code i am comparing it with a siso transmission system. in this case i am using the QAM transreceiver example provided by NI. however besides the given A...

Continue reading ...
 

Meeting with Prof A. S. Ranade

Posted by Ujjval Shah on Saturday, February 28, 2009, In : Meetings/Phone Conversations/Mails 

Today I had an hour long meeting with Prof. A. S. Ranade. It was the first official meeting where we discussed the project. I started off from point 0 – explaining what MIMO is. Then we moved on to ‘Diversity’- i.e. in a nutshell- sending replicas of signal to achiever better performance, which is the main idea behind mimo. Space Diversity being the area of interest in this project, we discussed what physical ways of achieving it are. Following that we discussed the two techniques of Ma...


Continue reading ...
 

Maximum Likelihood Detection and Receiver

Posted by Ujjval Shah on Friday, February 27, 2009, In : Theory 

The received signals at a receiver antenna in two time slots can be written as:

For more than two antennas, the  max lik rec function will be



...
Continue reading ...
 

Orthogonal Space-Time Block Codes (OSTBC)

Posted by Ujjval Shah on Friday, February 27, 2009, In : Theory 

The goal of space-time coding is to achieve the maximum diversity of NM, the maximum coding gain, and the highest possible throughput. In addition, the decoding complexity is very important.

Alamouti code

N = 2 M = 1

To transmit b bits/cycle, we use a modulation scheme that maps every b bits to one symbol from a constellation with 2bsymbols

First, the transmitter picks two symbols from the constellation using a block of 2b bits. If s1 and s2 are the selected symbols for a block...


Continue reading ...
 

Maximum Ratio Combining (MRC)

Posted by Ujjval Shah on Friday, February 27, 2009, In : Theory 

M receiver antennas receive M signals each represented as:

rm = αms + ηm,

where ηm is a white Gaussian noise sample added to the mth copy of the signal. A maximum-likelihood (ML) decoder combines these M received signals to find the most likely transmitted signal.We consider a coherent detection scheme where the receiver knows the channel path gains, αm. 

Owing to its array gain, MRC typically achieves a few dB better SNR than does SC.

 

...
Continue reading ...
 

Combining Methods

Posted by Ujjval Shah on Friday, February 27, 2009, In : Theory 

The source of diversity does not affect the method of combination with the exception of transmit antenna diversity. For example, receiving two versions of the transmitted signal through polarization diversity is the same as receiving two signals from two receive antennas for the purpose of combining

 There are two main combining methods that are utilized at the receiver:

  •  Maximum Ratio Combining (MRC)
  • Selection Combining

...
Continue reading ...
 

Probability Error

Posted by Ujjval Shah on Friday, February 27, 2009, In : Theory 

Probability Error for Diversity

P= c1e-c2 γ

γ –snr

in fading without diversity


In fading with diversity of NtxNr=Nd


Probability Error for Array Gain


...
Continue reading ...
 

Diversity Methods

Posted by Ujjval Shah on Friday, February 27, 2009, In : Theory 

The replica of the transmitted signal can be sent through different means [99]. For example, it can be transmitted in a different time slot, a different frequency, a different polarization, or a different antenna. The goal is to send two or more copies of the signal through independent fades. Then, since it is less likely to have all the independent paths in deep fades, using appropriate combining methods, the probability of error will be lower.

  •  Time slot – repetition
  • Frequency – fdd
  • Pol...


Continue reading ...
 

Diversity

Posted by Ujjval Shah on Friday, February 27, 2009, In : Theory 

The main idea behind “diversity” is to provide different replicas of the transmitted signal to the receiver. If these different replicas fade independently, it is less probable to have all copies of the transmitted signal in deep fade simultaneously. Therefore, the receiver can reliably decode the transmitted signal using these received signals. This can be done, for example, by picking the signal with the highest SNR or by combining the multiple received signals. As a result, the probabi...


Continue reading ...
 

Overview

Posted by Ujjval Shah on Friday, February 27, 2009,

Brief Summary of the project

Definition:

Simulation of a Multiple Input Multiple Output (MIMO) system using various Space Time Coding (STC) techniques in LabVIEW

MIMO-STC technique is one of the salient features of the WiMAX Mobile standarad, which along with Multiple Access scheme for multiple users, also marks it different from the WiMAX Fixed standard. The above simulation will be done specifically keeping in mind the WiMAX standard.

The success of the simulation will be done after com...


Continue reading ...
 
 

  

Make a Free Website with Yola.