The first general answer is that mobile antennas are usually omni directional. As they are mobile the direction to the other subscribers is usually unknown and unpredictable.
For more specific answers you need to provide more definition in your questions.
Normally Planar Inverted F antennas are used.But its very difficult to design triband PIFA.so now-a-days FICA(Folded Inverted Conformal Antenna) are used mutiband coverage.All these antennas are Omnidirectional antenna.
For further info on FICA go thr the attached document.