Today's fronthaul CPRI usually requires 2.4Gb/s to 7.2Gb/s, too much for G.fast. Today's wireless network often has a single Baseband Unit (BBU) supporting multiple Radio Units (RU), also called remote radio heads. Cellular speeds are just now rising from 100-150 megabits to 300-450 megabits, well within the capacity of G.fast. My initial reaction was "ho-hum," but BT's Richard Knowles pointed out what I had missed. Most fronthaul uses the Common Public Radio Interface, which requires much higher speeds. BT and Cavium found an alternative that brought fronthaul requirements down to G.fast speeds.
They may be spread across a building for better indoor coverage or may be kilometers away. The connection from a BBU in the field to the remotes is called "fronthaul." Backhaul is from BBU to the high capacity of the telco network. CPRI fronthaul speeds require fiber today.
Cavium and BT are developing an alternative to CPRI that requires less bandwidth.
Knowles writes, "By splitting the base station functionality above the physical layer we have successfully demonstrated a ‘Mid-haul’ solution which requires 10% overhead above the line rate. Using CPRI, the front haul would require 2.4Gb/s to support 150Mb/s, using the novel functional split this is reduced to 170Mb/s. Angel Atondo of Cavium explains what they are testing. "This trial splits the LTE L1-L2 protocol and significantly reduces the required fronthaul bandwidth."
There could be large savings in some locations up to 400 meters with copper available. 150 megabits won't be sufficient for long in many places because LTE is quickly moving to two and three carriers and higher order MIMO. Data rates of 300-800 megabits will become common.
Cavium and BT hope G.fast will bring down the effective cost of small cells, especially 5G in high frequencies. Five years ago, most of us expected substantial deployments of small cells and femtocells. It hasn't happened and some once very promising companies are no longer with us. The backhaul costs were just too high. Sometimes, real estate was also prohibitive. "The lab based demonstration showed successful operation of this concept over G.fast, a major milestone in our research," BT writes.
Here's the pr.
BT partners with Cavium in Cloud RAN trials
BT announced today that it has successfully used G.fast technology to deliver a ‘Cloud Radio Access Network’ (C-RAN) cellular network service over copper, in an experiment believed to be a world first.
C-RAN is a new network architecture used to connect cellular base-stations to mobile operators’ core networks. A traditional approach to C-RAN requires a dedicated fibre link to connect transmitters at the top of a cell tower to complex signal-processing equipment deeper in the network. This can involve complex and costly engineering work if no fibre is present in the ground to carry the signal.
Researchers at BT’s Adastral Park Labs in Ipswich, in collaboration with US-based semiconductor manufacturer Cavium, Inc. (NASDAQ: CAVM), have demonstrated that they can use G.fast technology to deliver cellular data over copper lines at speeds of 150 – 200Mbps.
This removes the need for mobile operators to invest in costly, high capacity backhaul links over dedicated fibre connections. By providing a far more economic “fronthaul” connection between the base station and the mobile operators’ core network, a C-RAN service delivered over G.fast would significantly lower the cost of deployment for mobile operators building out 4G networks today and 5G architectures in the future.
Dr Tim Whitley, MD for Research & Innovation at BT said: “Using G.fast to deliver a cellular network is an exciting breakthrough for C-RAN and yet another world first for our team of researchers at Adastral Park.
“These technologies will play a key role in 4G networks and will be fundamental to 5G architectures. The trials are another step towards a fixed and mobile network which will support customers’ increasing demands for data.”
“We are very excited to collaborate with BT, using Cavium OCTEON Fusion-M™ basestation and ThunderX® server processor technology to validate this new class of Radio Access application with G.fast technology.” said Raj Singh, General Manager of Cavium’s Wireless Broadband Group.
“Our successful testing has laid the groundwork for enabling LTE deployments today and 5G deployments in the future using G.fast.”
As well as exploring the role that G.fast may play in helping operators to roll out their 4G/5G networks, Openreach, BT’s local access network division, is also trialling G.fast as an access technology in Huntingdon and Gosforth, alongside a further BT technical trial in Swansea. G.fast is significant because by building on current Fibre-to-the-Cabinet (FTTC) technology, it allows Openreach to bring ultrafast speeds to a wide footprint far more rapidly and without the expense and disruption of running fibre directly into a home or business.
If the trials prove successful – and if UK regulation continues to encourage investment – the company has pledged to provide ultrafast speeds to 10m homes by 2020 and to the majority of the UK within a decade.
BT has invested c£500 million that in R&D every year. The company is one of the largest investors in R&D of any company in the UK and globally in the telecoms sector, and currently holds an astonishing 4,560 patents.
From Huawei ON FRONTHAUL
FrontHaul for indoor coverage
Indoor spaces isolated from macrocell coverage may have peak traffic at different times than those that occur outdoors, especially weekends and evenings. Examples of such areas are usually indoor stadiums, shopping centers, cafés/bars, convention centers, and government offices, covered by indoor lampsites, hotel BBUs, etc. Indoor small cells placed on ceilings or interior walls can use existing FTTx or Ethernet resources as per the availability.
However, wired solutions can play a useful role in small cell backhaul, and of course, the overall backhaul solution can be a hybrid of wired and wireless (such as short-length microwave connectivity).
FrontHaul for outdoor coverage
For outdoor FrontHaul coverage areas, microwave technologies, including E-Band (71 to 76GHz), V-Band (60GHz), and Sub Link (Sub 6GHz) are usually best for supporting the LOS/n-LOS/N-LOS terrains. This accelerates rollout and makes O&M quite a bit easier, while enabling full outdoor assembly and unified NMS solution. It is more adaptable in terms of site location (walls, rooftops, poles, etc.). PMP application is useful as it eliminates the need for line-of-sight, making it useful for hotspot areas, while PTP application, with its longer transmission distance (though line-of-sight) can connect PMP hub modules with macro sites.
BT's Richard Knowles