Jason Frank Hunzinger

Learning complex temporal patterns with resource-dependent spike timing-dependent plasticity

Studies of spike timing-dependent plasticity (STDP) have revealed that long-term changes in the strength of a synapse may be modulated substantially by temporal relationships between multiple presynaptic and postsynaptic spikes. Whereas long-term potentiation (LTP) and long-term depression (LTD) of synaptic strength have been modeled as distinct or separate functional mechanisms, here, we propose a new shared resource model. A functional consequence of our model is fast, stable, and diverse unsupervised learning of temporal multispike patterns with a biologically consistent spiking neural network. Due to interdependencies between LTP and LTD, dendritic delays, and proactive homeostatic aspects of the model, neurons are equipped to learn to decode temporally coded information within spike bursts. Moreover, neurons learn spike timing with few exposures in substantial noise and jitter. Surprisingly, despite having only one parameter, the model also accurately predicts in vitro observations of STDP in more complex multispike trains, as well as rate-dependent effects. We discuss candidate commonalities in natural long-term plasticity mechanisms.

Relays in HSPA+: Power Control and Mobility

There is substantial and growing motivation to deploy wireless relays in 3G+ and 4G networks both in residential and commercial contexts to achieve significant coverage extension and capacity increases at potentially relatively low cost. However, relays operating in shared spectrum may introduce interference thus potentially counterbalancing gains, and conversely, relays requiring a dedicated resource (for access or backhaul) may raise issues of efficiency and load balancing including under or over use of either relay or macro (base station) resources. In this paper, we consider these issues and propose new power control and mobility algorithms to overcome these challenges. Results of our detailed system simulations are presented demonstrating how substantial gains in user experience, capacity, and coverage extension may be obtained in the context of HSPA+.