  Base station (BS) sleeping has emerged as a viable solution to enhance the
overall network energy efficiency by inactivating the underutilized BSs.
However, it affects the performance of users in sleeping cells depending on
their BS association criteria, their channel conditions towards the active BSs,
and scheduling criteria and traffic loads at the active BSs. This paper
characterizes the performance of cellular systems with BS sleeping by
developing a systematic framework to derive the spectral efficiency and outage
probability of downlink transmission to the sleeping cell users taking into
account the aforementioned factors. In this context, we develop a user
association scheme in which a typical user in a sleeping cell selects a BS with
\textbf{M}aximum best-case \textbf{M}ean channel \textbf{A}ccess
\textbf{P}robability (MMAP) which is calculated by all active BSs based on
their existing traffic loads. We consider both greedy and round-robin schemes
at active BSs for scheduling users in a channel. Once the association is
performed, the exact access probability for a typical sleeping cell user and
the statistics of its received signal and interference powers are derived to
evaluate the spectral and energy efficiencies of transmission. For the sleeping
cell users, we also consider the conventional \textbf{M}aximum
\textbf{R}eceived \textbf{S}ignal \textbf{P}ower (MRSP)-based user association
scheme along with greedy and round-robin schemes at the BSs. The impact of
cell-zooming is incorporated in the derivations to analyze its feasibility in
reducing the coverage holes created by BS sleeping. Numerical results show the
trade-offs between spectral efficiency and energy efficiency in various network
scenarios. The accuracy of the analysis is verified through Monte-Carlo
simulations.
