Jaap Haartsen

Bluetooth: vision, goals, and architecture

A few years ago it was recognized that the vision of a truly low-cost, low-power radio-based cable replacement was feasible. Such a ubiquitous link would provide the basis for portable devices to communicate together in an ad hoc fashion by creating personal area networks which have similar advantages to their office environment counterpart - the local area network (LAN). Bluetooth is an effort by a consortium of companies to design a royalty free technology specification enabling this vision. This article describes the vision and goals of the Bluetooth program and introduces the radio-based technology.

Impact of non-reciprocal channel conditions in broadband TDD systems

Multi-path fading gives rise to frequency-dependent channel conditions. For narrowband TDD systems, channel conditions in uplink and downlink (or forward and reverse) can be assumed reciprocal. For broadband TDD systems applying frequency domain scheduling, reciprocal channel conditions are no longer valid. Using the coherence bandwidth for assessing the correlation between uplink and downlink can lead to invalid conclusions. By using cumulative distribution functions derived from a large number of channel realizations, it is shown that the radio attenuation at relatively small frequency offsets can differ by several dBs for a large percentage of the cases. This is particularly a problem in cognitive (UWB) radios that apply detect-and-avoid techniques and rely on uplink detection to protect the downlink reception. Until now, non-reciprocity between uplink and downlink channels was considered a challenge in case of detecting FDD systems. However, in this paper it is shown that even for detecting broadband TDD systems, reciprocity between uplink and downlink channels can no longer be assumed. Other challenges arise when adaptive antennas are used without feedback and downlink parameters are based on uplink measurements.

Bluetooth-ad-hoc networking in an uncoordinated environment

A new universal radio interface called Bluetooth/sup TM/ has been developed enabling electronic devices to connect and communicate via short-range radio links. The technology allows the design of low-power, small-sized, and low-cost radios that can be embedded in a wide range of future products. The Bluetooth system operates in the unlicensed Industrial-Scientific-Medical (ISM) band at 2.4 GHz which is globally available. Bluetooth radios use frequency hopping to spread their signals and to provide resistance against interference from other Bluetooth hoppers and other radio transmitters in the band. This paper addresses the challenges to provide ad-hoc network functions in the Bluetooth system. Both the needs for frequency hopping and the lack of a central controller in ad-hoc radio networks have placed special requirements on the design of the air interface. The paper further describes the coexistence of and bridging between independently hopping piconets, the concept of scatternets, and discusses hop synchronization in general.

Short-Range Connectivity with Bluetooth

In the last decades, progress in microelectronics and VLSI technology has fostered the widespread use of computing and communication applications in portable electronic devices. Up until now, information transfer between these devices has been cumbersome relying on cables and infrared. Recently, a new universal radio interface has been developed enabling electronic devices to connect and communicate via short-range radio connections. The Bluetooth™ radio technology eliminates the need for wires, cables and connectors between cordless or mobile phones, modems, headsets, PDAs, computers, printers, projectors, and so on, and paves the way for new and completely different devices and applications. Bluetooth is regarded as a complement and an extension to existing wireless technologies, addressing the short-range and inter-device connectivity. The technology enables the design of low-power, small-sized, and low-cost radios that can be embedded in existing portable devices. Eventually, embedded radios will lead towards ubiquitous connectivity.