I would be more than happy to clarify your query for you. In the interim, you are more than welcome to browse online to dig deeper into all that high frequency trading encompasses. Telecommunication is a key part of the HFT as milliseconds, which in retrospect translates to millions. Therefore, within this technology, fibers and microwaves are used to transfer information. Some companies are specialising solely in building infrastructures- which essentially consists of telecommunication- as a means to beat their competitor and do trades faster than anyone else. Call it as you will, but indeed it is still within the realm of telecommunication. With regards to the PHD inquiry, please check online yourself for further information, but in laments terms, the cause of big  data and machine learning clearly implies data analysis.