Supporting LTE and multiple standards with SDR - Embedded.com

Supporting LTE and multiple standards with SDR

The demand for mobile broadband and data services is growing rapidly driven by the sales of smartphones and other connected devices. LTE, the fourth generation mobile network technology, promises to meet that demand with multi megabyte connections for mobile subscribers.

Analysys Mason predicts that by 2016 over 80% of global wireless data traffic will be generated indoors. The demand for high speed mobile broadband and data services will be concentrated to public spaces, such as coffee shops, shopping malls or offices, when people have the opportunity to stop and browse the internet, check emails and stream video. The challenge that RF and microwave engineers now face is how to deploy robust systems that are capable of dealing with multiple users in a small area transferring large amounts of data.

One solution is to deploy dedicated LTE base stations even in small areas, however this can be a costly and time consuming process. The drawback of installing new base stations configured to support LTE is that existing network equipment will have to be upgraded, or replaced, which will increase the number of network assets that will need ongoing management, and maintenance. However, there are techniques that can be employed to support LTE and squeeze more capacity, and benefit, out of existing spectrum allocations.
 
In traditional radio based communications, base-stations and repeaters have operated on fixed standards. Supported standards are hardwired into the equipment and so cannot be changed without a physical upgrade. Today, numerous mobile telecommunications networks exist, such as GPRS and 3G not to mention the networks used by the emergency services such as Terrestrial Trunked Radio (TETRA). This means that for each of these networks, dedicated network equipment has to be strategically positioned to deliver network coverage.

By adopting a software-defined-radio (SDR) approach RF engineers will be able to accommodate future developments and enhancements in network functionality without having to replace older equipment. With SDR, engineers can remotely change the radio standard that network components operate on simply by installing new software. Network equipment can also be used dynamically to support the networks standards that require additional bandwidth. In terms of future proofing networks and ensuring a return on investment in the network infrastructure, the benefits of SDR are clear. Regardless of future planned and unforeseen changes in the use of radio standards, with SDR the network hardware will be able to accommodate these changes with nothing more than a software upgrade.

In terms of addressing the challenges posed by the introduction of LTE, while SDR may provide long-term cost-savings and strategic advantages, more immediate obstacles have to be overcome before the network can be rolled out. Data intensive standards, such as LTE,

are not as propagation efficient as existing network standards, which means that more network equipment is required to deliver consistent coverage.

One cost-effective solution to this problem is radio repeaters. Repeaters can be placed on the edge of poor coverage areas to propagate LTE signals for a much lower cost than installing new base-stations. The repeater can be deployed along with a distributed antenna system, which allows mobile operators to provide wireless coverage and capacity for voice and data services across any given area. The antenna system will cater for high capacity usage without the risk of overload.

Up until now, such an approach has never been seriously considered or has only ever been seen as a temporary solution. But technological advances in digital signal processing have overcome the old detractors of repeaters including interference, noise and sensitivity reduction. In addition, SDR makes repeaters a long-term solution – not just a temporary fix. With the use of SDR, their ability to support multiple network standards makes them not only a cost-effective way to increase network coverage now but also a long term tool for propagating radio spectrums of all types – a value that extends far beyond the deployment of LTE.

Håkan Samuelsson is the Chief Technology Officer at Axell Wireless .

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