Cross-Layer Wireless Resource Allocation
Abstract
A fundamental problem in networking is the allocation of limited resources among the users of the network. In a traditional layered network architecture, the resource to be allocated at the medium access control (MAC) and network layers is the use of communication links, viewed as "bit pipes" that deliver data at a fixed rate with occasional random errors. This bit pipe is a simple abstraction of the underlying physical and data link layers. There is growing awareness that this simple bit-pipe view is inadequate, particularly in the context of modern wireless data networks. Indeed, as highlighted throughout this issue, significant performance gains can be achieved by various cross-layer approaches, i.e., approaches that jointly consider physical layer and higher networking layer issues in an integrated framework. In this article, we consider several basic cross-layer resource allocation problems for wireless fading channels. Here, the resources to be allocated include the transmission power and rate assigned to each user. In modern wireless systems, a variety of link adaptation techniques such as adaptive modulation and coding or variable rate spreading are employed that enable a user's data rate to be adapted over time based in part on time varying channel fading. This results in a physical layer that is no longer well modeled as a fixed-rate bit pipe; instead, a much richer abstraction is required. In this setting, our focus is on characterizing fundamental performance limits, taking into account both network layer QoS and physical layer performance. We note that at the physical layer, fundamental communication limits established by information theory are, in many cases, well understood. However, when higher-layer objectives such as delay are taken into account, much less is known about fundamental performance tradeoffs. The problems surveyed in this article are attempts to address such basic questions.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 07, 2005
- Accession Number
- ADA435199
Entities
People
- Edmund Yeh
- Randall A. Berry
Organizations
- Northwestern University