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Simplifying Network Architectures with Wireless Fronthaul

May 4th, 2015

As portable technology becomes more prevalent and network data capacity increases, the need for simplified network architectures at lower running costs becomes imperative.

To fix this issue, mobile operators have begun to move to a C-RAN architecture (otherwise known as Centralized-Ran and Cloud-RAN). This involves moving parts of the radio network control from a co-located state (antenna at the cell site) to locations deeper within the network. With this, a transmission type known as fronthaul is introduced into the network infrastructure. Fronthaul is a similar concept to backhaul; it essentially links the mobile network back to the wired network. The C-RAN approach is beneficial because it allows for flexibility within the network, decreases costs, and reserves the limited power and space that exists at cell sites.

To successfully shift to C-RAN architecture, a migration from COAX to fiber-based interconnections between the BBU (baseband unit) and the remote radio head (RRH) is necessary.

In traditional copper architectures, the BBU and RRH are located together inside a cabinet in the cell site. The baseband unit performs signal-processing functions and creates radio signals; the remote radio head then converts radio signals into radio frequency signals. From there, a coax cable connects the RRH to the antenna at the top of the site.

On the contrary, fiber-based interconnections are structured with the RRH and the antenna at the top of the cell site. The RRH is connected to the BBU in the cabinet through use of Digital Radio over Fiber (D-RoF) technology. The RRH in a fiber-based interconnection takes radio elements of a base station and separates them from the baseband controller, thus a CPRI or OBSAI is required. Since the interconnection is fiber-based, it has a low link loss; this helps to provide more power and bandwidth. This method also allows the possibility for use of long reach optics and provides flexibility for network operators by centralizing baseband units at a central office location.

The CPRI is a digital interface standard for encapsulating radio samples between radios and digital baseband processing units and allow for the connection of different radios to centralized controllers. The CPRI/OBSAI protocols are defined at a range of speeds from 600Mb/s to 10Gb/s, which are similar to 1G, 2.5G and 10G data rates of WDM optics. Due to this, the CPRI/OBSAI are able to be supported over WDM. This allows the potential to add WDM technology to fronthaul networks.

WDM fronthaul CPRI systems offers low delay, lower expenditures for both equipment costs/use of fiber resources, no specialized enclosures, no requirement for backup battery, and uses minimum power. Since CPRI is combined with WDM technology, a larger number of remote radio heads can share fiber with other services. It also allows for multiple wireless operators to share fiber. Fronthaul CWDM CPRI is a future-proof method that would reduce costs, simplify networks, and share resources to cater to the growing demands for higher bandwidths.

Through experience with customer support and troubleshooting, Precision Optical Transceivers is backed with extensive knowledge and expertise in the field of Wireless Fronthaul Networks. Precision also offers industrial temperature products to support this network architecture; these include passive Mux/DeMux and active WDM optical transceivers. For a complete listing of Wireless Fronthaul compatible products, visit http://www.precisionot.com/Products/Transceivers.html

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