Heavy traffic limit theorems are established for a class of single server queueing models including those with heavy-tailed or long-range dependent arrivals and time-varying service rates. The models are motivated by wireless queueing systems for which there is an increasing evidence of the presence of heavy-tailed or long range dependent arrivals, and where the service rates vary with the changes in the wireless medium. Since changes in the wireless medium occur slowly, the service rate is assumed to vary slower than that of the arrivals.The main focus of the paper is to obtain the different possible limit forms that can arise depending on the relationship between established scalings for both the arrival and departure processes. The limit forms obtained here are driven by either Brownian motion (when the contribution from the departure process dominates the limit) or the limits of properly scaled arrivals (when the contribution from the arrival process dominates the limit), typical examples being stable Lévy motion or fractional Brownian motion. In particular, for the case where arrival process is given by the infinite source Poisson process, this relationship, which determines the type of the limiting queue-length process, is a simple condition involving the heavy tail exponent, arrival rate and channel variation parameter in the wireless medium model. The limit forms are also affected by the assumption of a slower varying service rate.To establish these limit results, two approaches are studied. In one approach, when the limit is driven by Brownian motion, the perturbed test function method is extended to incorporate reflection. In contrast, the second approach allows for non-Markovian driving processes in the limit. Both approaches involve averaging in the drift term arising from random service rates at the departures. In the second approach, this averaging is carried out directly and pathwise, thus sidestepping the assumption of driving Brownian motion used in the perturbed test function method. In the case of the infinite source Poisson model, when the limit is stable Lévy motion, it is also argued how the limit form can be deduced using infinitesimal operators.