That is to say, when femtocells operate in closed access mode, sleeping control and user access only depend on the activity level of networks; while for open access mode, besides the activity level of networks, user access still depends on the location of users.
Typical subsystems include alarm, access control, closed-circuit video, two-way voice communication, parking control, and other related systems.
The FAPs can operate in three different access control modes: closed access, open access, and hybrid access [2, 3].
Most security professionals think of alarm, access control, and closed-circuit television (CCTV) systems first when securing a facility.
In conclusion, the SIR of each type of users needs a slightly different SIR model for the femtocell location (inner region or outer region) and femtocell access control (open or closed).
Some common physical security countermeasures are—electronic burglary systems, closed circuit television (CCTV) systems, electronic access control systems, perimeter security systems, locks, lighting, fire systems, and specialized protection systems.
On the other hand, whether a cellular user will be served by a femtocell is more complicated and dependent on the type of access control: (1) in closed access, a femtocell will not serve any cellular users, even if they are in its coverage; (2) in the open access, a femtocell will serve any cellular users as long as they are in its coverage, they are named neighboring cellular users.
Specifically, when a femtocell is configured in the closed subscriber group (CSG) manner (also called "closed access"), only the users included in the femtocell's access control list are allowed to use the femtocell resources.
Such access control may be acceptable in closed systems and networks but is not adequate in open systems and networks where the real identities and other critical information about requesters may not be known to the systems and networks.
Femtocell hybrid access is a promising choice to control user association between macrocells and femtocells [6, 7], rather than the closed access and open access mode which render femtocells fully closed and open to macro users.
