Fronthaul, Midhaul, Backhaul: What Matters to Whom and Why

Acronyms are common in any industry, and can change over time. 

Backhaul is classically that portion of the network between the wide area network (the core network) and the access network, which runs from headends or central offices to customer locations). 

In a mobile network context, that classically meant the network connecting cell or radio sites and a mobile switching office (central office). With growing virtualization of the network, that has changed a bit. 

source: Redhat 

Many now use the term “fronthaul” to describe links between a central office or mobile switching center and radio sites. In the past, all of that might have been termed “backhaul.” In the new terminology, backhaul then refers to all metro connections, which we have classically called the “distribution” or “trunking”  network. 

Some prefer to use the term “midhaul” for metro or trunking connections between central offices and regional data centers, further restricting backhaul only to links between the wide area network and the regional data centers. 

That might not matter too much, if at all. The term fronthaul generally is meaningful when radio access network functions are virtualized. In such cases fronthaul describes the trunking network between radio sites and controller or baseband signal processing sites. 

It is helpful for radio access network designers and suppliers of RAN infrastructure, or for analyzing capital investment and some elements of operating cost. The distinction rarely is meaningful for discussions of business model, devices, revenue models, digital transformation or marketing. 

source: TechTarget.

That sort of change is not unusual. The way the connectivity industry uses terms always changes over time. The global definition of “broadband” in 1980 was any data rate of 1.5 Mbps or greater. These days the “legal” definition is whatever a government regulator says it is. Narrowband was 64 kbps. Sometimes we used the term “wideband” for data rates greater than narrowband but not at the broadband threshold. 

For a time, some internet service providers tried a new usage of “wideband” to mean “speeds faster than broadband,” though the nomenclature did not take. 

Sometimes the terms we use to describe whole industry segments become archaic, such as “telcos” and “cable TV operators” and the core value each provides: voice in the former case, television in the latter case. 

In the 1970s Integrated Services Digital Network was the next generation network. For enterprises, the commercial reality by the 1980s was frame relay, not ISDN. 

By the 1980s there was a contest between Broadband ISDN ( Asynchronous Transfer Mode) and internet protocol networks as the proposed next generation network. TCP/IP was supposed to be a transitional framework. 

As always, there were advantages and disadvantages for each alternative. Communications service providers always preferred platforms that had predictable performance. Data communications professionals preferred the simplicity and cost of TCP/IP, even if predictability was less. 

Everything was commercially settled once the internet emerged as the global driver of requirements in the communications and computing  businesses. Connectionless IP was far cheaper than connection-oriented ATM, in terms of interface cost. 

Many new mission-critical apps could function just fine with some amount of “best effort” packet delivery. And though voice remains important, most of the new devices with communications needs were “computing” devices.