Will 5G Make Use of Dynamic Spectrum Access?
Dec 1, 2014 4:00 PM, Doug Irwin, CPBE AMD DRB
FARNBOROUGH, HAMPSHIRE, ENGLAND�Will 5G wireless access include DSA (dynamic spectrum access) as part of its new technology? This is one question posed by Julie Bradford in an article recently published in RCRWireless.com.
Dynamic spectrum access is a method in which unused parts of spectrum are identified and subsequently used for transmission. From the article: �By identifying unused sections of spectrum in the area in which it was operating, it was hoped that up to 10 times more spectrum would be available for transmissions.�
DARPA used DSA for a prototype �cognitive radio system'' about 10 years ago; but with the switchover to digital television, and the availability of TV �white spaces'', interest in DSA is growing. An obvious application is for the on-the-horizon cellular technology known (now) as 5G. There are at least 2 reasons for this:� The theoretical limits of what can be achieved through higher-order modulation schemes are being reached, with any gains insufficient to keep pace with demand, and; � There are some gains to be had with respect to multiple-input, multiple-outputs and Coordinated Multipoint, but not enough to keep up with demand.
Again from the article: �The last variable available to us in our attempts to increase capacity is spectrum, and (at least in theory) DSA maximizes availability and efficiency of spectrum across all operators.�
While the advantages of a properly operating cognitive system with DSA seem obvious, several cautions are put forth as well:� The switchover to digital TV occurred over 6 years ago, yet commercial use of white spaces is still limited by �complications of deploying these devices in practice.'' The �hidden node'' problem, in which one node of a cognitive system fails to identify the others, and generates interference in the system, is one such issue.� Regulators have already shied away from the cognitive approach; they then introduced beacons that identify spectrum usage; and now are settling on the use of a database of white spaces in each location that is used in addition to spectrum sensing.
At least in the immediate future, the large cell companies are putting much of their resources in to the acquisition of new spectrum.