We introduce a new model of spatial random multiple access systems with a
non-standard departure policy: all arriving messages are distributed uniformly
on a finite sphere in the space, and when a successful transmission of a single
message occurs, the transmitted message leaves the system together with all its
neighbours within a ball of a given radius centred at the message's location.
We consider three classes of protocols: centralised protocols and decentralised
protocols with either ternary or binary feedback; and analyse their stability.
Further, we discuss some asymptotic properties of stable protocols
