Simple and Effective Messaging and more:Whatsapp

Few months ago , I downloaded this application to my Android OS phone. Actualy it is very user friendly and I realy satisfied with this application.

 

Whatsapp is very popular real time messaging software for smart phones. We can say that It is simply sort of SMS+MMS+ File Sharing and uses GSM and/or Wi-Fi.

 





Whatsapp Chat Window



It is very easy to attach some file(s) during chatting. You can specify group and chat with your friends all together. Plus, you can add emotions.

 

Deleting message history and even changing background of chat screen is nice things. Also it has "last seen". it is very noteful to control your friends they were online or not :)

Another good thing is you do not annoy with boring adds during chating.

 

Application uses your phone contacts. So you do not need to add by putting  him/her email  etc account to app.

 

In my opinion, simplicity is just coming for that reason.

Total download number is between 100milion -500 milion. So it is fantastic huge number.

On the other hand, please be aware this application is not free. Ok. it seems it is free for first dowloading from Google Play Store but you need to check account settings. It is just trial version. You have to pay and there is 3 payment options for 1 -3 or 5 years.

Anyway, I put following picture which explains how to check your paying settings. Please just follow settings --> Account --> Paying Info --> Validity

Checking validity date of application

Overall, this is very cute application. Unfortunately, I heard some security vulnerabilities if you put your SIM to another phone. http://www.neowin.net/ explains this case in more detail.

 

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Are Base Transceiver Station and Mobile Healthy?

This is very common issue for many people and actualy. So we decided to explain this topic in scientific way.
RF is non -ionizing radiation category like Microwaves, Infrared etc. On the other hand,  ultraviolet, X-Rays, Gamma Rays are in ionizing radiotion category.

GSM Standards are defined by ETSI (European Telecommunication Standardization Institute) in Europe and FCC (Federal Communication Commission) in USA. Since RF is non-ionising radiation;
ICNIRP (International Commission on Non-Ionizing Radiation Protection ) rules are means a lot to us. WHO (World Health Organization) and ILO (International Labor Organization) recognizes the ICNIRP studies. Europe Countries take ICNIRP radiation limits about human health. In USA, FCC takes care the IEEE (Institute ofElectrical and Electronics Engineers) And ANSI (American National Standarts Institute) studies.

So , for GSM users like us, following values are important for us;

What is the meaning of above values?
Above things are just hazard limits  of RF and it is based on 0.1 celcius increasing human body heath.
On the other hand, In Turkey, above limits are more safety than Europe Countries.

As a result,

Output power of mobile phones dynamically changes according to distance between antenna tower etc. Average power is  1W, maximum 2W (it is up to GSM frequency too) and  Output power of BTS antenna is maximum 60W.  These values are not enought to heat water actually. This is good for us.
Also There is no clear evidence between cancer and GSM equipments. But it does not indicate that everything is green. Authorities are still searching the relationship between  Radio Frequncy and Human Health.
And please do not forget, somethings which seems innocent for people generally but it is more dangerous than GSM Freq. like High Voltage Lines.

We can just do following for better protection:

1. Do not make a call in your call without using any special kit. As, only one proof about hazard of GSM is, talking with mobile phone while driving, increases traffic accident risk :)
2. Do not make long calls or use headset etc
3. Try to keep distance your body and mobile
4. Distance between antenna and human might be at least ~9 meters.

By the way, We strongly reccomend following links for further information:


http://www.who.int/peh-emf/publications/en/mcmcradiationmobilephonebk.pdf

http://www.samsung.com/sar/sarMain?site_cd=&prd_mdl_name=GT-N7100&selNatCd=US&languageCode=EN

http://www.fcc.gov/encyclopedia/specific-absorption-rate-sar-cellular-telephones
Turkish Web Site:
http://www.biltek.tubitak.gov.tr/sandik/gsm.pdf
And very good  unit conversion site:
http://www.compeng.com.au/emc_conversion_tables_rf_calculator.aspx

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LTE Voice Codec AAC-ELD

We are using mp3 file format generally in our computers and mobile phones to be able to listen music.  In reality, we are not listening original sound there.  Original sound is sort of raw data and we are just hearing compressed version of original sound.

 Raw Voice
Raw voice for example 16 bit 44 kHz wave format (.wav) 3 minutes will be approximately 30 megabytes. This is very huge size. If it is compressed into 128Kbps mp3 then it is around 3 megabytes. Simply, we can see that file size significantly decreases if we use codec.

 

 

What is Codec?

Codec is a short name for coder-decoder the software that takes a raw data file and turns it into a compressed file. An audio codec is a device or computer program capable of coding or decoding a digital data stream of audio.  Because of original sound size is big, we need to use codec for many perspectives like network stability etc.

GSM Codecs.

In GSM history, many codec types  have been developed.  These are;

Half Rate (HF)

Full Rate (FR)

Enhanced Full Rate (EFR)

 EFR introduced in 1997

Adaptive Multi Rate – Narrow Band (AMR or AMR-NB)

This is using in GSM and UMTS, introduced in end of 1990s.

Adaptive Multi Rate – Wide Band (AMR-WB)

Improved version of AMR due to a wider speech bandwidth compared to AMR Narrowband. It is commercially released in 2008. Also this is introduction with HD-Voice quality.

Advanced Audio Coding – Enhanced Low Delay

This is final developed codec for GSM World and using in LTE networks. This codec is designed for  Full-HD Voice. To be able to reach full HD voice quality,  codec  has to support  ~20khz frequency.  To compare differency; previously explained  HD-Voice branded codec  AMR-WB   supports only 7kHz.By the way, very important point is, both network and handsets have to support this feature.
 

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Which modulation types are being used in GSM and it's successors

If we quit pre-GSM wireless technologies, we can specify the mobile technologies as followings:

GSM
An open, digital cellular technology used for transmitting mobile voice and data services 
GPRS

A very widely deployed wireless data service, available now with most GSM networks

EDGE

GSM Evolution (EDGE) technology provides up to three times the data capacity of GPRS 
WCDMA or 3G

The air interface for one of the International Telecommunications Union’s family of third-generation (3G) mobile communications systems.
HSPA
 The set of technologies that enables operators to upgrade their existing 3G/WCDMA networks to carry more traffic and at faster speeds.

LTE
Designed to be backwards-compatible with GSM and HSPA, Long Term Evolution uses the OFDMA air interface, in combination with other technologies, to offer high throughput speeds and high capacity.

Wireless or not we are using 2 types of signal. One of them is carrier signal and the other one is data signal.

  
We can consider this sinus wave as our carrier signal as an example.

And let's consider above figure is our data signal.

To be able carry our data, we have to use carrier signal in order to send it to long distances.
Let's put all together in PSK modulation

                                     

Note: we need only one carrier for PSK. Some of the modulation types requires  2 different carrier signals like FSK. 


Modulation may be done by varying the amplitude,phase, or frequency of a high frequency carrier
inaccordance with the amplitude of the message signal. 

Main goal of enhanging modulation is just inreasing the number of bits carried by Hertz or bandwidth.
Now, let's briefly see the modulation types for GSM technologies:

GSM GPRS uses GMSK type modulation.

Note: It is common way to explain modulation types by using polar graph. The letter I means a carrier 'In Phase' with the carrier signal. And in the letter Q means 'Quadrature' (or perpendicular). Do not worry you can consider I and Q as X and Y axixes for angle. Also please see the link for further information regarding symbol and quantization http://en.wikipedia.org/wiki/Quantization_%28signal_processing%29

EDGE uses  8PSK modulation

UMTS and WCDMA
Regarding UMTS Release 99 it was QPSK.  After 3GPP Release 7 introduced 64QAM modulation for HSDPA and 16QAM for EUL

The advantage of using QAM is that it is a higher order form of modulation and as a result it is able to carry more bits of information per symbol. By selecting a higher order format of QAM, the data rate of a link can be increased.
The table below gives a summary of the bit rates of different forms of QAM and PSK.

LTE
LTE stands for Long Term Evalution and really trembles me as my expectations is very high for it.
Actualy my operator is using UMTS based tech in Istanbul and it is sufficient to watch something from youtube. (maybewe do not have so much data traffic because of unwanted bills :) )
Regarding 3GPP spects  we will introduce with 128 QAM


Now, it is enough to talk about modulation to prevent to go into deeper :)
See you in next blog. Please do not hesitate me to contact if you have suggestions, reccomendations or questions.
Have a great day.


REFERANCES
http://www.gsma.com/aboutus/gsm-technology
http://www.exaltcom.com/
http://www.ilmondodelletelecomunicazioni.it/argomento.php?id_lezione=43&id_capitolo=287
http://biosonicstelemetry.com/resources.php
Prof. Robert Webber from following link:
http://www.youtube.com/watch?v=-_TWtJsgzlw&NR=1&feature=endscreen
http://www.telecomhall.com/what-is-modulation.aspx
http://staff.neu.edu.tr/~fahri/mobile_L7.pdf
http://wireless.arcada.fi/MOBWI/material/CN_4_4.html
http://mobile-telecom-networks.com/umts/general/17-modulation-schemes-used-in-umts
http://www.radio-electronics.com/info/rf-technology-design/pm-phase-modulation
http://www.3gpp.org/ftp/Specs/html-info/36912.htm

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