We present a simple algorithm for the maximum independent set problem in an $n$-vertex graph with degree bounded by $4$, which runs in $O^*(1.1446^n)$ time and improves all previous algorithms for this problem. The algorithm is analyzed by using the ``Measure and Conquer'' method.
We use some good reduction and branching rules with a new idea on setting weights to obtain the improved time bound without increasing the number of branching rules in the algorithm.