A software defined radio comparison of received power with quadrature amplitude modulation and phase modulation schemes with and without a human

This paper presents the application of software-defined radio to the study of received power with and without a human in close proximity to a receiver transmitter pair. Software defined radio is increasingly being used in radio related research and teaching in Universities, Schools and Colleges. For teaching it is typically being used in the classroom in close proximity to users/observers. Because several transceiver sets are needed to compare two or more modulation techniques in conventional radio this presents significant challenges with matching, synchronisation and noise. Two or more separate systems are needed. In contrast with software defined radio simple changes to the ratios of I and Q modulators can execute several modulation methods using the same system. This paper examines the use of a typical software defined radio in close proximity to a user which is typical in a classroom situation. The most suitable of two modulation techniques for use with communication systems close to humans as a function of received power for a typical office environment is presented

The effects of water on an on-body monopole diversity antenna pair at 1800MHz

This paper presents the effect of water on a pair of 1.8GHz on-body diversity monopole antennas mounted on the forearm of a sitting male static volunteer. Application of a water layer to the forearm was seen to both reduce efficiency and increase directivity leading to a slight overall increase in gain. Increased gain was shown to increase antenna correlation thereby reducing diversity gain in the antenna pair

Rohacell radomes for delicate antennas on the body at 2.4GHz

This paper presents the use of two generic on-body antenna types, a probe and a magnetic dipole with and without a radome constructed of Rohacell. Its is shown that Rohacell minimally attenuates the electromagnetic signal transmitted or received by the antenna concluding to the cover being essentially transparent to radio waves at 2.4GHz and 5.8GHz. In on-body meaurements radomes can be used to protect the antenna surfaces from damage and protect nearby personnel from being accidentally struck by quickly rotating antennas. Performance of two on-body antennas is considered on and off the body by measurement and simulation. Results show that the Rohacell protection has negligible effect on the performance of the antenna systems regardless of loading by humans and polarity. This paper aims to enlighten use of Rohacell to protect antennas used for body centric experiments and experiments in body-centric settings

Human effect on on-body selective combining at 2.4 GHz

Use of the body as a platform for wearable electronics is a topical subject. Omnidirectional antennas are thought to be useful for antennas in body area networks. However, the desirable properties of omnidirectional radiation patterns close to humans are severely diminished due to the lossy load nature of biological matter and high levels of scattering due to mismatch. To alleviate these problems two or more antennas can be used on the body. In this paper, two on body antennas are used with selective combining and then compared with their free space equivalents. The frequency of operation is 2.4GHz

SIMO/MIMO body-centric space–time diversity over software-defined radio

This thesis is germane to body-centric communication measurements and analyses at different frequency bands. It presents measurements and analyses of the radio channels for humans. This research contains a novel and comprehensive study of body-centric single input multiple output (SIMO) diversity. This has included the analyses of diversity techniques with off-body communications in different settings within indoor environments. The objectives in this research are; investigating the benefits of using multiple antennas for off-body and on-body channels and studying the performance of diversity antennas for off-body in different environments with both genders. A further novel aspect of this thesis has been concerned with off-body channel characteristics using software defined radio (SDR) and LabVIEW using different modulation schemes for measurements and analyses. This method combines processing and control in software, paired with SDR for the over the air interface. The combination of SDR and LabVIEW is shown to provide a platform to facilitate experiments in the presence of humans that is useful for prototyping different types of radio channels. This method also gives a new aspect for a novel treatment of a 2x2 body-centric multiple input multiple output (MIMO) system. It is shown how the difficulties associated with implementing MIMO systems can be overcome by using SDR combined with LabVIEW. Studying the effects of water in the body-centric communication channels are also a new area of research presented here. This work has shown how water encapsulated within Polyacrylamide gel can be exploited as a cheap and available material to enhance the performance of on-body antennas. It is shown that water gives 1–3dB enhancements from the measurements of SIMO and MIMO systems with the human presence

User detection at the base station in a GSM 900 mobile phone system

Typically mobile handsets are used in close proximity to the users head, hand and shoulder. The radio frequency energy received and produced by the handset interacts with biological tissue causing severe perturbations to the radio channel. Human tissue is both dispersive and lossy therefore both the frequency and amplitude of any wave interacting with a user either in the uplink or the downlink will be changed. Identification of the presence of humans can be achieved by comparisons between the channel impulse response with and without a human user. This paper presents measurements and analytical framework for the determination of human presence in a cellular communication system over the air channel comprising a human, a handset and base station. For this analysis the chosen bearer is GSM