I’ve spent a lot of time recently talking to customers about microwave spectrum in the mobile backhaul. Improving interference discrimination using antennas such as Andrew Sentinel microwave antennas can potentially give you a dramatic way to improve your network performance by re-using bandwidth without the huge expense of buying more spectrum or using larger antennas.

It’s an often repeated story. If you’re involved in telecoms, you’re probably tired of the many presentations referring to smart phones and tablets driving the explosion of data and bandwidth requirements for the supporting networks. You’ll see a lot of information in the telecoms media about the various access technologies involved (e.g. small cells, LTE, Wi-Fi). Sadly, the backhaul has often been overlooked – the poor cousin perhaps to the Radio Access Network (RAN). Now the industry is waking up to the fact that all this data coming in from the RAN needs to be backhauled and many of the current backhaul networks simply aren’t up to the job.

Network equipment manufacturers are responding in many ways.
One of the ways they are achieving more capacity in backhaul is with improved modulation schemes.

But the higher order schemes need more bandwidth to work and are more susceptible to interference.

The chart above shows the typical data rates you can achieve on short haul links using different channel bandwidths and higher order modulation schemes. As you can see from the graph, the key to higher data rates is increased channel spacing (bandwidth) combined with higher order.

Microwave spectrum, then, is a real limiting factor.

Low side lobe (e.g. ETSI Class 4 - Andrew Sentinel) antennas are the answer here. Customer feedback from our first year of selling Sentinel shows one of the main use cases to be that better interference discrimination allows more re-use of channels.

As an example, 7 MHz channel bandwidth allows up to 160 paired channels in the 23 GHz band. Change that to 28 MHz and you are down to 40 paired channels but your data rate per link has improved by up to a factor of 4 (or more!). However you have now only 25% of the previous available channels.

So you could buy more bandwidth, but it can be expensive. Or, how about just re-using those available channels without buying bigger antennas? Wouldn't that be useful? Many of our customers are now running trials to see if this is possible in their networks and the answer is increasingly becoming yes!

The picture below (in the simplest of terms) explains the concept.

Figure 1 – A typical Class 3 network, 7 MHz channels with little need for channel re-use

Figure 2 – 28MHz to get increased data rates on each link. However channel re-use due to fewer available channels is now needed.

Figure 3 – Now use class 4 antennas and because of the improved interference discrimination, we can re-use the channels with little risk of interference.

But don’t just believe me—try it yourself! The above is, after all, just the concept – every network is different. We can give you the information you need to run your own simulations or do a live trial. Just as Class 3 microwave antennas took over from Class 2, I believe the industry is acknowledging that the time is now right for Class 4 antennas to take over from Class 3. What are your thoughts? Think this is something you’d like to look at for your network?

About the Author

Derren Oliver

Derren Oliver is Product Line Director for the Microwave Systems unit at CommScope. He has nearly 20 years of experience in the telecoms industry, beginning in test and measurement for both wireless and wireline networking products at Hewlett Packard, Agilent Technologies and Ixia before joining CommScope in 2010. He holds a bachelor degree with first class honors in electrical and electronic engineering from the United Kingdom’s Heriot-Watt University and an MBA from Edinburgh Business School.

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2 comments for "Creating More Bandwidth for the Mobile Backhaul"
Danny BenSimhon

Hi. The operators world wide gave-up to continuous need for upgrades in the traditional MW systems. With those old systems, the rates shown here are much lower then what they need. So, they use XPIC and higher modulation technics. That led to bigger antennas, doubling both modem cards and RF units, higher power consumption, heavier loads on the antenna polls. All that efforts, with lots of CAPEX and OPEX required, leads to maximum ~800Mbps. As MMW spectrum has been released in recent years with light licencing schemes, they are moving to use it because of its native capabilities: smallest footprint miniature all outdoor solution that can enable 1Gbps at relatively low modulation (64QAM) with smaller antenna, pencil-beams (<1 degree) that enables enormous re-use capabilities, with competitive prices. This is the real future of backhaul links.

Donald Gardner

Hi Danny, Thanks for your comment. Derren is otherwise occupied, so I figured I’d answer for him. I do not believe that anyone in the industry would argue that MMW radio links provide a valuable alternative solution, particularly over shorter link lengths. Recognizing this, CommScope has a range of 80 GHz antennas available that can be directly integrated to OEM radios. Personally, I would suggest that MMW solutions are complementary to other microwave frequency bands with each having their own particular sweet spot. It really is a matter of selecting the best solution for a given situation.

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