Average Packet Delay Analysis for Ultra Wideband Wireless Networks of Simple Nodes

Abstract

Networks using ultra-wideband wireless (UWB) as the physical layer show promise for application as personal area networks. UWB can provide high capacity (on the order of 1.3 Gbps over short distances) wireless links and allow variable capacity links to be formed between nodes. However, as with all communication technologies, there is an upper bound on the aggregate capacity of all links that transmit within specified interference boundaries.

Certain characteristics of UWB wireless links give rise to properties not seen with other wireless technologies. Two such properties are long synchronization times for establishing links between nodes and the ability to change individual link capacities by choosing pseudo-random (PN) codes of different lengths for channel coding.

The number of incoming and outgoing links for a single UWB node is driven by cost and technology and affects the topologies available for a network formed from UWB nodes. Whether composed of nodes with a single incoming and a single outgoing UWB link or M incoming and outgoing links UWB networks can be designed to minimize average network delay. UWB networks of different scales and node types also have unique management problems requiring specific management protocols in order to function efficiently. This thesis addresses the following problems related to networks composed of simple UWB nodes:

- Given a traffic matrix specifying the average packet delivery rate between nodes and an aggregate capacity bound for all links, determine a topology for the network and capacities for each link to minimize average packet delay.

- Given a traffic matrix specifying the average packet delivery rate between nodes, determine the effect of the acquisition time to establish a new network link on average packet delay and when packet switching operation performs better than packet forwarding operation.

- Given a ring network of UWB nodes, determine whether adding additional single direction links can improve delay performance for the network. Consider both fixed links and links that switch between nodes as a function of time.

- Given a ring network of UWB nodes, determine the network management issues for the network and propose protocols to efficiently address these issues.

Our contribution is three-fold: first, we derive analytical expressions for average delay in UWB networks with ring topologies. Then, we consider ways to add additional fixed or switching links to UWB ring networks in order to reduce average packet delay. We validate these analytical results via extensive simulations. Finally, we discuss the performance of protocols for managing such networks.