An investigation into the viability of UWB as lower-layer for Bluetooth

Abstract

This report presents an investigation into some merging options between an upper-layer Bluetooth (BT) protocol stack with a lower-layer ECMA-368/9 Ultra Wideband (UWB) radio connection. A Bluetooth over Ultra Wideband (BToUWB) system is implemented by channelling an existing compliant Bluetooth connection’s data over an Ultra Wideband Medium Access Control (MAC) and Physical (PHY) layer radio channel. The aim of this project is to provide a description of the methodology used to create a BToUWB link and evaluate some advantages pertaining to the merger between the two Wireless Personal Area Network (WPAN) technologies. Prior to channelling data over a UWB connection, a compliant Bluetooth and UWB connection were configured between two Linux enabled computers by use of Bluetooth and UWB enabled Universal Serial Bus (USB) dongles. BlueZ, the official Bluetooth stack for Linux, were used to implement a modified Bluetooth stack. By modifying the open source BlueZ files, the Host Controller Interface (HCI) commands sent to the HCI sublayer by upper layer Logical Link Control and Adaptation Protocol (L2CAP) and Synchronous Connection-Oriented (SCO) implementations were hijacked and routed to a UWB “router and convergence” implementation for transmission over the UWB subsytem. Similarly lower level HCI events were spoofed to the L2CAP and SCO layers by the UWB convergence implementation upon receiving packets from the UWB subsystem. The commercial availability of UWB hardware through Wireless USB dongles enabled the realization of a compliant UWB link between the systems, requiring special driver modifications and Intel provided firmware to establish a WiMedia Logical Link Control Protocol (WLP) network. A specially developed test program generates L2CAP, Radio Frequency Communication (RFCOMM) and SCO Bluetooth data for testing the BToUWB link. The various Bluetooth data packets are routed from the Bluetooth stack to a developed kernel space routing module, which encapsulated the packets and route them via the WLP interface over the wireless high-speed UWB network to the remote system. On the remote side, the packets propagate its way back up through the UWB hardware and software module, and to the router module via call-back functions in the WLP interface. The router module strips the headers and injects the packets back into the Bluetooth L2CAP, RFCOMM or SCO layer for further Bluetooth processing. A test program running on the remote system, receives the test data and loops it back for asynchronous analyses, or stores it for later comparison in synchronous analyses. The results obtained from the system analyses shows how a Bluetooth system can benefit from implementing UWB as lower layer wireless interface over a short range by either improved asynchronous bandwidth, or synchronous reliability. The results also show some limitations of the pilot UWB hardware and firmware available over longer distances. In general, the successful transmission of Bluetooth data over the BToUWB implemented system proves the HCI layer to be a viable mergence point between the two protocols.