Common Public Radio Interface, or CPRI in short, is a standard initially developed by Nokia Siemens. Soon it was joined by Ericcson, Huawei, NEC and Alcatel-Lucent, together comprising the five largest telecommunication equipment manufacturers in the world. With the inception of powerful handsets, wireless technologies have become more prevalent and consumer demand for high speed data fierce. Wireless companies are constantly under pressure to increase capacity and equipment suppliers to come up with novel methods to efficiently transport RF signals.

Traditionally, telecommunication equipment manufacturers like Ericsson and Alcatel-Lucent have sold equipment called Base Stations to wireless carriers. These are RF processing units that act as a gateway between carriers’ macro network (backhaul) and wireless fronthaul to consumer handsets. These analog setups have proven to be costly due to the large amount of energy, space, equipment and labor required to deploy. The largest associated cost is processing the high powered analog RF signals coming out of Base Stations. This is where CPRI comes in play.

Rather than transporting RF signals in analog form, equipment vendors offer a new solution: transporting wireless signals digitally as part of a fronthaul wireless network, commonly known as DAS (Distributed Antenna System). CPRI then, is a set of specifications set forth by equipment manufacturers in an effort to standardize the protocol between radio equipment control and radio equipment.

To make things easier to understand, RF base stations have been filling the role of radio equipment control and RF processing. They also conduct analog-to-digital (A/D) and digital-to-analog (D/A) conversions, leaving the distribution of fronthaul RF signals to 3rd party vendors. The inception of the CPRI standard means Base Stations can now concentrate on performing tasks like directing wireless traffic between carriers’ fronthaul and backhaul networks. RF processing and A/D processing are done at remote radio nodes. These nodes are now being connected to radio equipment control via fiber optic or Ethernet cable.

With the inception of CPRI, typical wireless fronthaul networks now resemble your everyday LAN (Local Access Network), with standard point-to-point, star, and chained configurations feasible in the deployment of radio equipment. Obviously, RF balancing and propagation requirements remain among remote radio nodes, but the use of passive auxiliary components has been greatly reduced.

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