Just like KPN and Vodafone want T-Mobile 3g network, further modernize. The way in which that will happen through, for example, dual carrier-hsdpa+, such as KPN and Vodafone, remains to be seen. Details about the modernisation of want to T-Mobile later lost.
At this moment in time has T-Mobile on hsdpa+, a faster version of hsdpa, which, in turn, relies on the technique of umts. Dual carrier-hsda+ is going a step further, and works with new antennas and software to maintain two simultaneous connections with a phone. Phones should be suitable for the technique to directly benefit from it, but many modern phones, including the iPhone 5 and the LG Nexus, that.
The improvements to the 3g network at the time that T-Mobile is the roll-out of its 4g network to prepare; the company promises after the summer 4g. Mid next year will T-Mobile nationwide network. That the company nevertheless its 3g network and want to modernize it, is probably because existing devices can take advantage of. At this moment there are still very few 4g phones for the Dutch market.