A discrete-time Wiener phase noise channel model is introduced in which
multiple samples are available at the output for every input symbol. A lower
bound on the capacity is developed. At high signal-to-noise ratio (SNR), if the
number of samples per symbol grows with the square root of the SNR, the
capacity pre-log is at least 3/4. This is strictly greater than the capacity
pre-log of the Wiener phase noise channel with only one sample per symbol,
which is 1/2. It is shown that amplitude modulation achieves a pre-log of 1/2
while phase modulation achieves a pre-log of at least 1/4.Comment: To appear in ISIT 201