Partial　interference　alignment　(PIA)　strategies　for　the　K-user　interference　channel　are　considered.　Two　schemes　are　proposed　to　align　the　partial　interference　for　the　downlink　interference　channel　in　the　case　of　K＞3.　In　the　first　scheme,　strong　interferences　are　limited　as　much　as　possible　by　aligning　the　two　strongest　interferers　into　a　same　subspace　at　the　receiver.　While　the　second　scheme　is　to　design　its　precoding　matrix　(or　vector)　by　selecting　the　precoder　pair　which　maximizes　the　chordal　distance　between　designed　signal　subspace　and　interference　signal　subspace　in　the　set　of　pecoding　matrices　(or　vectors)　at　each　transmitter.　Simulation　results　show　that　compared　with　the　existing　schemes　which　don＇t　optimize　the　precoder,　such　as　Fixed-PIA,　the　proposed　schemes　can　improve　the　sum　rates　significantly　by　selecting　IA　forms　in　multi-input　multi-output　(MIMO)　systems.　©　(2014)　Trans　Tech　Publications,　Switzerland.