What types of cables are defined for A-PHY? Is UDP possible?

MIPI A-PHY v1.0 defines coax or SDP (shielded differential pair) cables. There is nothing in the specification that prevents UDP (unshielded differential pair) implementation.

A-PHY v1.1 doubles the total downlink bandwidth from 16 to 32 Gbps by adding support for Star Quad (STQ) cables that provide dual differential pairs of conductors within a single shielded jacket. This enables two A-PHY ports over a single cable, saving cost, weight and complexity compared with using two separate coaxial or shielded twisted pair cables.