This is a very good text and regarded as one of the greats for a reason, but it glosses over a lot of lower concepts (like OFDM, which if I recall occupies only a single short chapter) and focuses very heavily on MIMO. Proakis and Salehi ("Digital Communications") and Goldsmith ("Wireless Communications") cover some of the "lower level" concepts like OFDM pretty well in depth from a theory standpoint. Goldsmith is a particularly good middle ground book. A highly underrated book is also Andreas Schwarzinger's "Digital Signal Processing in Modern Communication Systems", which covers how modems for these systems are actually implemented in real life and is quite approachable from an engineering standpoint.