To deliver a compelling quality of experience for subscribers, you must respond quickly to growing traffic demands. Modern Packet Microwave Mobile Backhaul products help you maximize the network’s performance by enabling rapid deployment of scalable backhaul to cell sites. Modern solutions include a portfolio of microwave products to address the backhaul needs of 2G, 3G, and LTE macro cells and 3G, LTE, and Wi-Fi® small cells. Radio spectrum is maximized using innovative techniques to maximize payload capacity to support the evolution to LTE and heterogeneous networks. Unique, common radio support for indoor and outdoor deployments enhances savings potential.
Packet Microwave Mobile Backhaul is a key component in a modern end-to-end mobile backhaul solution, which provides the flexibility, scale and operational simplicity to lower the total cost of ownership and simultaneously enhance the mobile service experience.
Rapidly support the optimal cell site location
Complete backhaul portfolio for macro cells and small cells
Support for all sites including both end and intermediate cell sites
Space and power efficiency
Full outdoor option to meet different microwave site space requirements
Achieve maximum spectral performance
Maximum bandwidth per band
Advanced quality of service levels supporting subscriber quality of experience
Scale the network cost effectively
Reliably bond radio channels to create larger microwave links
Any topology, any number of microwave link directions
Network awareness for both Carrier Ethernet and/or IP/MPLS networks
Be operationally efficient
Common radio for all cell sites
Evolutionary path from hybrid microwave to packet microwave at the touch of a button
Management beyond basic IP partner integration
Deployment, management, end-user benefits
Grow and retain subscribers by maximizing the mobile experience
Infrastructure support for increased subscriber bandwidth demands
Ability to react quickly to subscriber demand with optimally-located cell sites
Increased capacity that supports high bandwidth data applications
Packet Microwave Mobile Backhaul integrates a modern microwave portfolio with small cell optimized products to provide a complete backhaul offering for small cells and/or macro cells.
Read on in our following pages to find out more about technologies used in mobile backhaul applications
Boost capacity and reliability with advanced networking
With a modern microwave network, you should expect advanced Carrier Ethernet networking capabilities that can double network capacity while delivering high availability. These capabilities include:
Unique ring and mesh topology configurations that can double network capacity, improve reliability and reduce network costs
Integrated IP-microwave solutions that reduce space and power consumption
The ability to support TDM, Ethernet and IP services on a single packet-based network
Simplify operations with an end-to-end approach
Expect to see: a complete family of microwave solutions that addresses all network sizes and locations including tail, hub and backbone. With an approach that uses common equipment and software across all sites, vendors should help you streamline management processes and reduce TCO. Features offered:
Common radio transceivers that reduce the need for spares across all applications
A flexible range of Indoor Units (IDUs) and Outdoor Units (ODUs) to reduce space and power consumption
Common software and network management that simplify operations across the network
In radio technology, multiple-input and multiple-output, or MIMO , is a method for multiplying the capacity of a radio link using multiple transmit and receive antennas to exploit multipath propagation.
Earlier usage of the term “MIMO” referred to the use of multiple antennas at both the transmitter and the receiver. In modern usage, “MIMO” specifically refers to a practical technique for sending and receiving more than one data signal on the same radio channel at the same time via multipath propagation. MIMO is fundamentally different from smart antenna techniques developed to enhance the performance of a single data signal, such as beamforming and diversity.
MIMO can be sub-divided into three main categories, precoding, spatial multiplexing or SM, and diversity coding.
Precoding is multi-stream beamforming, in the narrowest definition. In more general terms, it is considered to be all spatial processing that occurs at the transmitter. In (single-stream) beamforming, the same signal is emitted from each of the transmit antennas with appropriate phase and gain weighting such that the signal power is maximized at the receiver input. The benefits of beamforming are to increase the received signal gain – by making signals emitted from different antennas add up constructively – and to reduce the multipath fading effect. In line-of-sight propagation, beamforming results in a well-defined directional pattern. However, conventional beams are not a good analogy in cellular networks, which are mainly characterized by multipath propagation. When the receiver has multiple antennas, the transmit beamforming cannot simultaneously maximize the signal level at all of the receive antennas, and precoding with multiple streams is often beneficial. Note that precoding requires knowledge of channel state information (CSI) at the transmitter and the receiver.
Spatial multiplexing requires MIMO antenna configuration. In spatial multiplexing, a high-rate signal is split into multiple lower-rate streams and each stream is transmitted from a different transmit antenna in the same frequency channel. If these signals arrive at the receiver antenna array with sufficiently different spatial signatures and the receiver has accurate CSI, it can separate these streams into (almost) parallel channels. Spatial multiplexing is a very powerful technique for increasing channel capacity at higher signal-to-noise ratios (SNR). The maximum number of spatial streams is limited by the lesser of the number of antennas at the transmitter or receiver. Spatial multiplexing can be used without CSI at the transmitter, but can be combined with precoding if CSI is available. Spatial multiplexing can also be used for simultaneous transmission to multiple receivers, known as space-division multiple access or multi-user MIMO, in which case CSI is required at the transmitter. The scheduling of receivers with different spatial signatures allows good separability.
Diversity Coding techniques are used when there is no channel knowledge at the transmitter. In diversity methods, a single stream (unlike multiple streams in spatial multiplexing) is transmitted, but the signal is coded using techniques called space-time coding. The signal is emitted from each of the transmit antennas with full or near orthogonal coding. Diversity coding exploits the independent fading in the multiple antenna links to enhance signal diversity. Because there is no channel knowledge, there is no beamforming or array gain from diversity coding. Diversity coding can be combined with spatial multiplexing when some channel knowledge is available at the transmitter.
Forms of MIMO
Multi-antenna MIMO (or Single user MIMO) technology has been developed and implemented in some standards, e.g., 802.11n products.
Per Antenna Rate Control (PARC), Varanasi, Guess (1998), Chung, Huang, Lozano (2001)
Selective Per Antenna Rate Control (SPARC), Ericsson (2004)
The physical antenna spacing is selected to be large; multiple wavelengths at the base station. The antenna separation at the receiver is heavily space-constrained in handsets, though advanced antenna design and algorithm techniques are under discussion.
XPIC is a feature used on Carrier-Class Microwave Link installations to increase capacity and spectral efficiency of a link.
A Microwave Link using XPIC technology capabilities effectively doubles the potential capacity of a Microwave Path.
XPIC allows the assignment of the same frequency to both the vertical & horizontal Polarization on a Path. Where available frequencies are limited then it is possible to assign the same frequency twice on the same path using both Polarizations.
Using standard Microwave equipment from any of the major manufacturers, if a full block of eight frequencies were available for a 6 GHz Lower band path then eight frequencies could be assigned in each direction on the path, four per polarization.
By comparison. using equipment with XPIC capability, sixteen frequencies may be assigned each way on the same path (eight per polarization).
A popular choice for modern IP networks is the Full Outdoor Radio (FOR). Also called “Zero Footprint Radio”, “All Outdoor Radio”, “Outdoor IP Radio”.
In an FOR, the radio includes the modem, user network interface and all RF processing sections in a single unit. This is typically mounted on the customer rooftop or tower site mated to a high gain directional antenna.
Connectivity is typically Power over Ethernet (POE) and optional Fibre Optics (SFP) connection
The Full Outdoor Radio (FOR) architecture is popular with:
Internet Service providers (ISP)
Wireless ISPs (WISPs)
Full Outdoor Microwave Radios offer up to 400(364) Mbps and 800(728) Mbps Full Duplex payload (1.6Gbps aggregate capacity) and higher up to 3Gbps or more, 6-38GHz licensed frequency bands.
Using suitable antennas and sites, ultra-long-distance links exceeding 100km can be achieved. Distances depend on:
Required throughput (Mbps)
Desired Availability (%)
Antenna size (gain)
For more information on Full Outdoor Radios and Microwave Networks please Contact Us
In radio communications, a Fresnel zone (/freɪˈnɛl/ fray-nel), , is one of a (theoretically infinite) number of concentric ellipsoids which define volumes in the radiation pattern of a (usually) circular aperture. Fresnel zones result from diffraction by the circular aperture. The cross section of the first (innermost) Fresnel zone is circular. Subsequent Fresnel zones are annular (doughnut-shaped) in cross section, and concentric with the first. The Fresnel Zone is named after the physicist Augustin-Jean Fresnel.
Importance of Fresnel zones
If unobstructed, radio waves will travel in a straight line from the transmitter to the receiver. But if there are reflective surfaces along the path, such as bodies of water or smooth terrain, the radio waves reflecting off those surfaces may arrive either out of phase or in phase with the signals that travel directly to the receiver. Waves that reflect off of surfaces within an even Fresnel zone are out of phase with the direct-path wave and reduce the power of the received signal. Waves that reflect off of surfaces within an odd Fresnel zone are in phase with the direct-path wave and can enhance the power of the received signal. Sometimes this results in the counter-intuitive finding that reducing the height of an antenna increases the signal-to-noise ratio.
Fresnel provided a means to calculate where the zones are–where a given obstacle will cause mostly in phase or mostly out of phase reflections between the transmitter and the receiver. Obstacles in the first Fresnel zone will create signals with a path-length phase shift of 0 to 180 degrees, in the second zone they will be 180 to 360 degrees out of phase, and so on. Even numbered zones have the maximum phase cancelling effect and odd numbered zones may actually add to the signal power.
To maximize receiver strength, one needs to minimize the effect of obstruction loss by removing obstacles from the radio frequency line of sight (RF LOS). The strongest signals are on the direct line between transmitter and receiver and always lie in the first Fresnel zone.
Determining Fresnel zone clearance
The concept of Fresnel zone clearance may be used to analyse interference by obstacles near the path of a radio beam. The first zone must be kept largely free from obstructions to avoid interfering with the radio reception. However, some obstruction of the Fresnel zones can often be tolerated. As a rule of thumb the maximum obstruction allowable is 40%, but the recommended obstruction is 20% or less.
For establishing Fresnel zones, first determine the RF Line of Sight (RF LOS), which in simple terms is a straight line between the transmitting and receiving antennas. Now the zone surrounding the RF Line of Sight is said to be the Fresnel zone.
Unlicensed and light licence wireless links is the most cost effective of all links and can be deployed in a matter of days. Currently in most countries there are a few unlicensed ISM-band frequencies that are used for point to point links and a few light licensed frequencies that provide interference free operation.
What is a Light Licensed microwave link?
Regional regulators (typically, in each country) are responsible for Spectrum Management of the Radio Spectrum. This naturally varies in each country due to different history of usage and allocation.
A Light License is where the licensee pays a small licence fee to register his/her radio link with regional regulators such as OFCOM (UK).
The regulator (such as OFCOM in the UK) use the licence to inform other potential users of the spectrum that there is already a radio link or links in the area when they register their own link prior to deployment. This information is also used to resolve disputes should interference arise.
Depending on which country you are in, these can include:
Licence free spectrum are the 5Ghz, 24Ghz, and 60GHz frequencies
Light licence spectrum operate in the 64-66GHz and 70/80GHz
Why consider unlicensed or light license links?
Low density areas not suffering from RF interference
Non-critical data transmission
When are licensed links mostly used?
Organisations looking to create a LAN across multiple buildings on the same site
Organisations looking to reduce the cost of existing leased lines
In low density areas where RF interference is low or free
When to consider opting for a licenced over unlicensed?
High density areas suffering from RF interference
Mission-critical data transmission
Is unlicensed or light licenced microwave right for you?
If you are looking for the simple answer, please contact Wireless Excellence for details. Our very experienced team are happy to discuss your requirements and advise on the best solution whatever your needs.
Modulation is a data transmission technique that transmits a message signal inside another higher frequency carrier by altering the carrier to look more like the message. Quadrature Amplitude Modulation (QAM) is a form of modulation that uses two carriers—offset in phase by 90 degrees—and varying symbol rates (i.e., transmitted bits per symbol) to increase throughput. The table in this blog post (Figure 1) describes the various common modulation levels, associated bits/symbol and incremental capacity improvement above the next lower modulation step.
2. Must all operators who use microwave backhaul use higher-order QAMs?
Higher-order QAMs are not necessarily a must-have for all network operators. However, higher-order modulations do provide one method of obtaining higher data throughput and are a useful tool for meeting LTE backhaul capacity requirements.
3. What is the main advantage of using higher-order QAMs with microwave radios?
The main advantage is increased capacity, or higher throughput. However, capacity improvement diminishes with every higher modulation step (i.e., moving from 1024QAM to 2048QAM the improvement is only about 10 percent!), so the real capability of higher-order modulations alone to address the objective of increasing capacity is very limited. Other techniques will be needed.
4. What are the tradeoffs of higher-order QAMs on RF performance?
First, with each step increase in QAM the RF performance of the microwave radio is degraded as per the Carrier-to-Interference (C/I) ratio. For example, going from 1024QAM to 2048QAM will produce an increase of 5 dB in C/I (Figure 2). This results in the microwave link having much higher sensitivity to interference, making it more difficult to coordinate links and reducing link density. Along with this increase in phase noise there will be an increase in design complexity cost.
Also, by increasing from 1024QAM to 2048QAM, system gain will decrease from above 80 dB to just above 75 dB (Figure 2). With much lower system gain microwave links will have to be shorter and larger antennas will have to be employed—increasing total cost of ownership and introducing additional link design and path planning problems.
All of the above are the results of linear functions: they degrade in a one-to-one relationship with the move to higher-order QAMs. Meanwhile, the capacity increases derived from higher-order QAMs are the function of a flattening curve: Each step increase in QAM results in a reduced percentage increase in capacity compared to prior increases in QAM. The added capacity benefits are diminished when considering the added costs of higher C/I and lower system gain.
5. Do you need to use Adaptive Coding and Modulation (ACM) while using higher-order QAMs?
ACM should be implemented while employing high-order QAMs to offset lower system gain. However, while ACM does help mitigate the effects of more difficult propagation when using higher-order modulations, it cannot help offset increased C/I.
6. What gives CableFree a “heads-up” here when other big name companies seem to be supporting the technology?
CableFree realizes higher-order modulations are not a panacea—a cure-all. While every minor technology improvement in throughput can help, a focus on technologies that grow capacity in hundreds of percentage points vs. tens of percentage points is most critical now. CableFree believes that these hundreds-of-percentage-points-of-improvement-in-capacity solutions will be the most important moving forward. It is in these technologies that CableFree has a “heads-up.” Such techniques include deploying more spectrum—particularly in the form of multichannel RF bonding (N+0) solutions—to achieve a minimum of 200 percent capacity increase. This technique is subject to frequency availability, but with flexible N+0 implementations (such as being able to use frequency channels in different bands and different channel sizes) many congestion issues can be avoided.
Second, intelligently dimensioning the backhaul network based on proven rules, best practices and L2/L3 quality of service (QoS) capabilities is another technique to provide potentially very large gains in backhaul capacity. Higher-order modulations can be one tool to achieve required capacity increases in the backhaul network. However, their inherent drawbacks should be well understood, while the most attention should be paid to other techniques that deliver more meaningful and quantifiable benefits.
7. Will operators need to “retrofit” microwave radios to be capable of higher-order QAM operation in their existing microwave infrastructure? Or will completely new hardware be required?
This depends on the age and model of the existing radios. Older microwave systems will likely need to be “retrofitted” to support 512QAM and higher modulations. Recently installed microwave systems should be able to support these technologies without new hardware.
8. How will QAM evolve in the future? Is the introduction of higher-order QAMs an indefinite process, with no end in sight?
The introduction of higher-order QAMs is not an endless process. As per Figure 1 above in this blog post, the law of diminishing returns applies: Throughput percentage improvement declines as modulation rates increase. The cost and complexity of implementing higher-order QAMs probably is not worth the capacity increase benefits derived—not past 1024QAM, in any event.