Fronthaul

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The fronthaul portion of a C-RAN (Cloud Radio Access Network) telecommunications architecture comprises the intermediate links between the centralized radio controllers and the radio heads (or masts) at the "edge" of a cellular network. [1]

In general it is coincident with the backhaul network, but subtly different. Technically in a C-RAN the backhaul data is only decoded from the fronthaul network at the centralised controllers, from where it is then transferred to the core network.

It comprises dedicated fibers carrying data in the CPRI or OBSAI format. [2] This fiber network is either owned or leased by the mobile network operator. In the UK for example BT Openworld owns a majority of the fiber network to radio masts. There are proposals to modify Ethernet to make it more suitable for the Fronthaul network. [3]

Recently, a novel wireless fronthaul solution has been proposed for ultra-dense small cell deployment where networked flying platforms (NFPs) such UAVs, drones, tethered balloon and high-altitude/medium-altitude/low-altitude platforms carrying FSO transceivers have been introduced as aerial hubs to aggregate the small cell traffic and offer connectivity to the core network. [4]

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Small cells are low-powered cellular radio access nodes that operate in licensed and unlicensed spectrum that have a range of 10 meters to a few kilometers. Recent FCC orders have provided size and elevation guidelines to help more clearly define small cell equipment. They are "small" compared to a mobile macrocell, partly because they have a shorter range and partly because they typically handle fewer concurrent calls or sessions. As wireless carriers seek to 'densify' existing wireless networks to provide for the data capacity demands of "5G"; small cells are currently viewed as a solution to allow re-using the same frequencies and as an important method of increasing cellular network capacity, quality and resilience with a growing focus using LTE Advanced.

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Networked flying platforms (NFPs) are unmanned flying platforms of various types including unmanned aerial vehicles (UAVs), drones, tethered balloon and high-altitude/medium-altitude/low-altitude platforms (HAPs/MAPs/LAPs) carrying RF/mmWave/FSO payload (transceivers) along with an extended battery life capabilities, and are floating or moving in the air at a quasi-stationary positions with the ability to move horizontally and vertically to offer 5G and beyond 5G (B5G) cellular networks and network support services.

IEEE 1914.1 is a standard for packet-based fronthaul transport networks developed under IEEE 1914 Next Generation Fronthaul InterfaceNGFI (xhaul) Working Group. NGFI (xhaul) working group is sponsored by IEEE Communications Society/Standards Development Board (COM/SDB). IEEE 1914.1 standardizes architecture and requirements for mobile fronthaul network – spanning between cell sites and centralized baseband locations in Centralized, Collaborative, Cloud and Clean Radio Access Network C-RAN.

Aerial base station

An Aerial base station (ABS), also known as unmanned aerial vehicle (UAV)-mounted base station (BS), is a flying antenna system that works as a hub between the backhaul network and the access network. If more than one ABS is involved in such a relaying mechanism the so-called fly ad-hoc network (FANET) is established. FANETs are an aerial form of wireless ad hoc networks (WANET)s or mobile ad hoc networks (MANET)s.

References

  1. http://www.lightreading.com/what-the--bleep--is-fronthaul/a/d-id/707868
  2. http://www.equicom.hu/wp-content/uploads/EXFO_anote310_Understanding-Basics-CPRI-Fronthaul-Technology_en.pd%5B%5D
  3. http://www.ieee1904.org/3/meeting_archive/2015/02/tf3_1502_ashwood_1a.pdf
  4. Alzenad, M.; Shakir, M. Z.; Yanikomeroglu, H.; Alouini, M.-S. (2018). "FSO-based vertical backhaul/fronthaul framework for 5G+ wireless networks". IEEE Communications. 56 (1): 218–224. arXiv: 1607.01472 . doi:10.1109/MCOM.2017.1600735.