Interference Avoidance Techniques and Decentralized Channel Access Schemes in Hotspot-Aided Cellular Networks

Computing & Wireless : Wireless and Communications

Available for licensing


  • Jeffrey Andrews, Ph.D. , Electrical and Computer Engineering
  • Vikram Chandrasekhar , Electrical and Computer Engineering

Background/unmet need

A two-tier cellular network comprising of a conventional macrocell overlaid with shorter range hotspots is an economical way to increase wireless capacity. One way to provide reliable hotspot access is through the concept of a femtocell (or home basestation), which is a low power, short range (10--50 meters) wireless data access point that provides high quality in-building coverage to home users and transports their wireless traffic over an internet-based backhaul. In a femtocell-aided cellular network, decentralized strategies for managing radio interference and providing reliable medium access are critical to ensure reliable communication. Commercial femtocell deployments will likely be deployed with minimal coordination and control overhead between femtocells and either the cellular network, or to neighboring femtocells. Alternatively, using expensive wireless spectrum to coordinate between the cellular network and hotspots is self-defeating as it undermines the principal argument?low capital and operating expenditures - for deploying femtocells in the first place. Consequently, low costs, limited backhaul capacity and scalability requirements will likely be the key issues that will dictate how vendors will design and manufacture femtocells.

Invention Description

This invention provides decentralized strategies for alleviating cross-tier interference in a hotspot-aided cellular network. Related contributions include enhancing indoor and outdoor coverage and maximizing spatial reuse in both underlay (universal frequency reuse) operation and overlay (frequency orthogonal) operation of the macrocell and femtocell Base Stations

The invention will enable interference management and provide low complexity medium access schemes in a two-tier cellular network. Benefits associated with this invention are higher capacity, better frequency reuse, low complexity, minimal network overhead and minimal control signaling across tiers.


  • Provides local intelligence at the femtocell in order to mitigate interference from neighboring femtocells as well as from cellular users. Such an interference adaptive behavior is not present in present hotspot deployment technologies.
  • Enables femtocells to minimize interference in systems either with full frequency reuse (e.g. current CDMA cellular systems) with/without spatial diversity (MIMO), or systems deploying frequency division access transmission schemes such as the 3GPP Long Term Evolution, the 802.16 Worldwide Interoperability for Microwave Access (WiMAX) WiMAX.
  • Optimized for interference management in existing and proposed wireless technologies.

Market potential/applications

Femtocell technology will be useful for providing enhanced in-home coverage and relaxing the traffic load on the conventional cellular network. Femtocells’ employing “open-access ” will assist outdoor cellular users to obtain better coverage provided they are within the radio range of the femtocell.

Development Stage

Proof of concept

IP Status

  • 1 U.S. patent application filed
  • 1 U.S. patent issued: 9,078,138

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