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Wireless backhaul systems can be classified according to the following frequency bands:
These frequencies are typically used for long-haul connectivity. While these frequencies excel in propagation, they typically bear higher fees and channel width availability is rather low (from 28/30 MHz to 56/60 MHz and, in rare cases, 112 MHz).
These frequencies are typically used for short-haul connectivity. The higher bands within the range often make wider channels available – 112 MHz and even 224 MHz.
Engineering-wise, millimeter waves or widebands, reside in the 30-300 GHz range. When discussed in the context of wireless transmission, these refer to bands of 57 GHz and above. Millimeter waves have evolved as an extremely cost-effective solution for ultra-high-speed connectivity for short ranges. The 57–66 GHz band is referred to as V-Band. The 71–76 and 81–86 GHz bands are referred to as E-Band. W-Band refers to the spectrum around 100 GHz, and D-Band refers to the frequency range of 130-175 GHz. Different uses of V-Band and E-Band are based on the propagation characteristics of the two bands and the available distance derived from them. V-Band has a much shorter range and is typically used for intra-campus connectivity, surveillance camera infrastructures or small-cell backhaul. E-Band has a significantly higher range and can be used for business customer access, cell site connectivity or fiber backup. Generally, the higher the frequency band and the wider the channel, the greater the throughput. In E-Band, wide channels are available, with channel spacing ranging from 62.5 MHz up to 2000 MHz (or 2 GHz). It can handle 10 Gbps using a single 2 GHz channel.
E-Band implementation is more challenging for longer links due to high attenuation, which results in reduced availability. Multiband resolves this challenge by combining a microwave carrier with an E-Band carrier, thus achieving both high capacity and high availability for longer distances.
Some of today’s backhaul networks, primarily in emerging markets, still employ circuit-switched (or TDM) solutions, whether T1/E1 or high-capacity SDH/SONET. These networks, originally designed to carry voice-only services, have limited bandwidth capacity and offer a non-cost-efficient scalability model.
Today’s surge in mobile data usage is fueled by anticipation and adoption of advanced releases of 4G and 5G services. This surge is driving operators to accelerate and finalize the migration of their networks to a more flexible, feature-rich and cost-optimized IP network architecture. Additionally, the surge in data usage in densely populated areas is driving operators to explore new network architectures. Such architectures utilize a variety of small-cell technologies requiring the deployment of dense wireless backhaul networks in various microwave and millimeter-wave spectral bands.
In order to ensure the success of these network strategies, operators require solutions that can support any network architecture for backhaul, including both all-IP and hybrid (IP and TDM) service connectivity.
Utilizing all-outdoor solutions eliminates the need for indoor rack space for the networking unit. In cases where the other equipment at the site (e.g. RAN equipment) is also in an all-outdoor configuration, there is no need for a shelter – making site allocation and acquisition simpler, faster and more cost-effective.
Since the node is based on a single box that covers all functionality (radio and networking), the number of part numbers in the network is reduced significantly.
All-outdoor solutions allow lower power consumption. First, the direct consumption of the unit is significantly lower. On top of that, the lack of an indoor unit eliminates the need for an air conditioning system. The saving is both in the A/C system itself and in its power consumption, which is typically half the power consumption of the unit it needs to cool.
The fact that the active equipment is installed high above the ground leads to additional security. Attackers (e.g. vandals) need to use extreme measures to physically reach the equipment in order to sabotage it.
An architectural revolution in 5G RAN allows massive horizontal disaggregation of the classic base station as it splits its functionality to three separate functions: the central unit (CU), the distributed unit (DU), and the radio unit (RU).
Bringing huge flexibility, scalability and performance improvements to network operators, this disaggregation also creates several possible RAN architectures, which can all be implemented in different parts of the same network. These architectures include: (1) cell site RAN, in which all three functions are co-located (the “classic” cell site architecture); (2) split RAN, in which the DU and RU are co-located and the CU is located in a central location; (3) central RAN, in which only the RU is deployed in the tail sites while the CU and DU are centralized; (4) and dual split RAN, in which each of the three functions is located in a different site.
These architectures introduce connectivity types or segments that did not exist in previous generations, like midhaul (between the CU and DU) and fronthaul (between the DU and RU). Both of these segments are actually an integral part of the RAN architecture (as opposed to backhaul, which connects the RAN to the network’s core).
Choosing split, central or dual split architecture is typically done as part of network densification that calls for more cell sites. Midhaul and fronthaul have new low latency requirement as those transmission segments are actually a part of the base station.
