  We consider a cognitive radio network in a multi-channel licensed
environment. Secondary user transmits in a channel if the channel is sensed to
be vacant. This results in a tradeoff between sensing time and transmission
time. When secondary users are energy constrained, energy available for
transmission is less if more energy is used in sensing. This gives rise to an
energy tradeoff. For multiple primary channels, secondary users must decide
appropriate sensing time and transmission power in each channel to maximize
average aggregate-bit throughput in each frame duration while ensuring
quality-of-service of primary users. Considering time and energy as limited
resources, we formulate this problem as a resource allocation problem.
Initially a single secondary user scenario is considered and solution is
obtained using decomposition and alternating optimization techniques. Later we
extend the analysis for the case of multiple secondary users. Simulation
results are presented to study effect of channel occupancy, fading and energy
availability on performance of proposed method.
