Long gone are the days when systems only needed to be available some of the time. Today, there are demands on systems 24 hours a day, 7 days a week, all year round.
Even planning for maintenance requires significant collaboration and communication between those that support and maintain the system and the users. The modern day wireless microwave (MW) and millimeter wave (mmW) network demands an always-available, never-failing, high-capacity, ultra-fast system to support the ever-changing mission.
Ask all public safety first responders over the age of 45 what the one thing is you can’t take away from them, and most, if not all, will say their radio for communication. Additionally, if you were to poll first responders aged 25 and under from the same community, most would say their smartphones.
The point here is to emphasize the importance of the network, regardless of the device used. Network and radio frequency (RF) engineers responsible for designing these systems need to consider ALL stakeholders, both radio (LMR) and mobile (LTE) users, as essential to supporting the mission.
The following abstract from Jim Rugg, Director of Public Safety & Federal Markets at Ceragon Networks, North America, covers some of the essential elements required to design a mission-critical wireless backhaul network.
When designing the network, design engineers need to start by gathering an exhaustive list of key essential requirements that also consider design topologies.
Microwave networks have historically relied on daisy chain and tree backhaul topologies. With networks transitioning toward an Ethernet all IP-based service oriented architecture (SOA), Ethernet Ring Protection Switching (ERPS) ITU-T G.8032 is one system element that may be considered when there is a need to re-route packets in a digital wireless backhaul network following a failure.
Once a desired topology has been determined, the essential elements and feature functionality need to be captured next. The following is a list of key questions and solution recommendations to help you determine what feature functionality is critical for your system specifications:
- Does the system need to have resiliency by offering failover in the event of a catastrophic failure?
A: If yes, then hot stand-by (HSB) in a 1+1 scenario or a 2 + 0 scenario, where the extra radio interface allows for double capacity in optimum operational mode, are viable options. These will serve as a failover if one of the radio frequency unit (RFU) interfaces fail, and prevent there being idle radio without any capacity benefit.
- Does the system need to accommodate for rain fade based on the geographic location of planned deployment?
A: If yes, you may need to include adaptive coding and modulation (ACM). Adaptive modulation means dynamically varying the modulation in an errorless manner in order to maximize the throughput under momentary propagation conditions. In other words, a system can operate at its maximum throughput under clear sky conditions, and then decrease gradually under rain fade. For example, a link can change from 1024 QAM down to QPSK to keep the link alive without losing connection. Prior to the development of ACM, microwave designers had to design for worst-case conditions to avoid link outage. The benefits of using ACM include: longer link lengths (distance), smaller antennas as it saves on mast space, and higher availability (link reliability).
- What, if anything, can be done to allow wireless backhaul design engineers to increase system capacity if there is a limited amount of channel pairs available in a desired licensed frequency?
A: One technique that is highly effective is called cross polarization interference cancelling (XPIC). XPIC is a feature used on carrier-class microwave link installations to increase capacity and spectral efficiency. It effectively doubles a microwave path's potential capacity.
In order to guarantee that a wireless backhaul system meets or exceeds 99.999 uptime to support mission-critical communications, wireless backhaul designers need to work directly with a wireless backhaul technology solutions provider capable of meeting these requirements.
For wireless backhaul engineers tasked with designing the next generation mission-critical wireless backhaul networks, Ceragon rises to the challenge with its IP-20 Assured family of products. All of the Ceragon IP-20 radios contain a simple, easy-to-use, common interface, with additional features consistently added to solve the most complex design challenges that customers face.
We invite you to learn more about how Ceragon is solving wireless backhaul design challenges and ensuring peace of mind by making backhaul simple and secure.
To learn more, visit us at: http://info.ceragon.com/public-safety_free-network-performance-assessment
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