On the Impact of Dynamic Spectrum Sharing Techniques on Legacy Radio Systems

The biggest challenge faced by dynamic spectrum sharing (SS) systems is the design of SS schemes that do not adversely impact existing legacy systems in the absence of perfect knowledge. We address this issue by developing a framework to evaluate the interference profile at a legacy receiver under different system scenarios which include the hidden node and imperfect-sensing problems. By analyzing the interference distributions and by comparing the two basic approaches to SS - interference-avoidance-based overlay and interference averaging-based underlay - we identify desirable characteristics for SS radio systems.We then leverage this knowledge to motivate the use of a hybrid SS approach that combines the benefits of the two basic approaches and substantially reduces the impact to the legacy system. The advantage provided by this approach is shown to increase with an increase in the bandwidth available to the SS system. In addition, the approach is more robust to imperfect information. The inclusion of log-normal shadowing is shown to further accentuate these performance trends.