Not too sure if you will be able to find datasheet for specific cell phone. These are proprietary information and mobile phone manufactures usually don’t share this type of information in public for various reasons. Depending on the business needs you should contact the vendors directly and seek datasheet, which might be obtained under a non-disclosure agreement (NDA). But there are a couple of other ways that you can obtain similar data.
Access Public Data from Federal Communications Commission (FCC)
If the mobile phone is sold in USA, then the mobile phone manufacture has to file a report with the FCC. This is public information, thus accessible through FCC web site. These reports will give you transmission power levels per the FCC test criteria, which might not be exactly what you are seeking, but you will get close. You will need the FCCID for the particular mobile phone which you should be able to find. Below is output power specification for a Samsung Galaxy S4.
IEEE 802.11 output power levels for Samsung Galaxy S4 (FCC)
FCCID Search form is a good place to start. You might be able obtain similar infomation for European Union (EU) too.
Test using Semi-anechoic chambers
This might be tedious and expensive, but can be done. There are a plethora of EMC test facilities that will glad to help you get this data.
Test using a GTEM chamber
This is less expensive, and can be done much more easily as long as you have access to the chamber and spectrum analyzer.
Specification from Wifi Module
But you might want to review widely available wifi modules. This might be the most practical method because you have access to datasheets with tolerances etc. Here are a few examples:
Chances are a wifi module with similar transmission power capabilities are in mobile phones.
- Federal Communications Commission USA
- FCC ID Help
- Samsung Galaxy S4 FCC Report
- 20 Highest and Lowest Radiation Cell Phones
- FCC Wireless Phones FAQS
- PCTEST Engineering Laboratory Inc
- Is interference between aircraft an issue for fly-by-wireless technology?
- License-Exempt Wireless Applications for Public Safety
- How to find out which certificates (FCC, CE etc.) are necessary for a product?