Shailesh Patil

Distributed Load-Balancing in a Multi-Carrier Wireless System

We consider a cellular network or a wireless local area network (WLAN), deployed with attachment points (APs) capable of transmission and reception in multiple radio-frequency (RF) carriers. A major factor contributing to the efficiency and stability of the network is the mechanism determining the connection of terminals to the appropriate AP and the RF carrier. This paper describes a practical, distributed, network-assisted and terminal-driven mechanism to determine the connections for load-balancing among the available RF carriers. The mechanism is based on a metric that we term as the service level indicating metric (SLIM). We extend the notion of SLIM to cases where Quality-of-Service (QoS) parameters are specified and propose a load-balancing mechanism for such cases. We demonstrate the near-optimality of the proposed mechanisms through 3GPP based simulations.

Effective OFDMA Based Signaling in Ad-Hoc Wireless Networks

Ad hoc wireless networks without central authority have attracted much attention in both academic society and industry. A key aspect of communications in such networks is the large dynamic range of interference. OFDMA (multiplexing simultaneous transmissions in different frequency tones) is an effective way of dealing with interference. On the other hand, there are many known distortions in transmit and receive chains of the communication devices, e.g. non linearity of the power amplifier, which can compromise the OFDMA orthogonality among the resources assigned to different transmissions. These distortions, together with the large dynamic range one would expect in ad hoc communications, can pose a threat to the effectiveness of communications in OFDMA ad hoc networks. In this paper, we propose and evaluate different signaling choices for communications in ad hoc networks, via both analysis and simulations. In particular, we observe that OFDMA based single tone signaling, i.e. each user transmits only on a single frequency tone, outperforms other signaling choices in many aspects.