This　study　investigates　the　cross-tier　base　station　(BS)　cooperation　in　non-uniform　heterogeneous　networks　where　the　distribution　of　pico　BSs　(PBSs)　is　modelled　as　Neyman-Scott　cluster　process.　The　authors　propose　an　edge　aware　cross-tier　cooperation　scheme　to　improve　the　performance　of　edge　hotspot　users　that　have　weaker　signal-to-interference-plus-noise　ratio　(SINR).　Taking　consideration　of　various　user　behaviours,　non-hotspot　users　are　only　served　by　the　nearest　macro　BS　whilst　the　hotspot　users　with　better　SINR　are　only　served　by　their　serving　PBSs.　The　edge　hotspot　users　who　suffer　from　high　cross-tier　interference　operate　in　the　cooperation　mode.　Stochastic　geometry　is　utilised　to　derive　the　SINR　and　energy　efficiency　performance　of　the　proposed　scheme,　which　is　compared　with　other　classical　schemes　such　as　full　cooperation　(FC)　and　traditional　non-cooperation　scheme.　Numerical　results　show　that　compared　with　the　FC　scheme,　the　proposed　scheme　can　maximise　the　energy　efficiency　of　the　network　by　an　optimal　cooperation　threshold,　when　SINR　coverage　is　larger　than　a　threshold.　The　authors　also　find　that　user　behaviour　have　little　effect　on　the　tradeoff　between　SINR　Coverage　and　energy　efficiency,　unless　spatial　aggregation　coefficient　is　very　small.