When mobile networks are discussed, it's usually about the air interface, i.e. the last few meters between the base station antenna and people's mobile devices. What gets little attention in the press, however, is how the data is transported between the base stations, the radio network controlers (in case of UMTS) and the core network. This is what's called the 'backhaul' network. On a very high level it's clear that UMTS and LTE networks today due to their broadband transmission speeds can no longer use 2 MBit/s E-1 connections but have to use something else. In practice that something else is either Fiber, copper cable or microwave. But which technologies are actually used over that medium in different parts of the backhaul network? This is what 'Mobile Backhaul' by Juha Salmelin and Esa Metsala gives an in-depth answer to. While reading the book I've learned a lot about how pervasive Ethernet technologies have become in recent years over any kind of medium. I've gained a much better understanding of how Ethernet protocol extensions for use in the WAN work and how MPLS plays into the game. In short, a very recommended read!