A minimum approximate-BER beamforming approach for PSK modulated wireless systems

A beamforming algorithm is introduced based on the general objective function that approximates the bit error rate for the wireless systems with binary phase shift keying and quadrature phase shift keying modulation schemes. The proposed minimum approximate bit error rate (ABER) beamforming approach does not rely on the Gaussian assumption of the channel noise. Therefore, this approach is also applicable when the channel noise is non-Gaussian. The simulation results show that the proposed minimum ABER solution improves the standard minimum mean squares error beamforming solution, in terms of a smaller achievable system's bit error rate.

Nocturnal ranging behaviour of urban hedgehogs, Erinaceus europaeus, in relation to risk and reward

Urban areas have both positive and negative influences on wildlife. For terrestrial mammals, one of the principle problems is the risk associated with moving through the environment whilst foraging. In this study, we examined nocturnal patterns of movement of urban-dwelling hedgehogs (Erinaceus europaeus) in relation to (i) the risks posed by predators and motor vehicles and (ii) nightly weather patterns. Hedgehogs preferentially utilised the gardens of semi-detached and terraced houses. However, females, but not males, avoided the larger back gardens of detached houses, which contain more of the habitat features selected by badgers. This difference in the avoidance of predation risk is probably associated with sex differences in breeding behaviour. Differences in nightly movement patterns were consistent with strategies associated with mating behaviour and the accumulation of fat reserves for hibernation. Hedgehogs also exhibited differences in behaviour associated with the risks posed by humans; they avoided actively foraging near roads and road verges, but did not avoid crossing roads per se. They were, however, significantly more active after midnight when there was a marked reduction in vehicle and foot traffic. In particular, responses to increased temperature, which is associated with increased abundance of invertebrate prey, were only observed after midnight. This variation in the timing of bouts of activity would reduce the risks associated with human activities. There were also profound differences in both area ranged and activity with chronological year which warrant further investigation.

A model of intelligent building energy management for the indoor environment

People's interaction with the indoor environment plays a significant role in energy consumption in buildings. Mismatching and delaying occupants' feedback on the indoor environment to the building energy management system is the major barrier to the efficient energy management of buildings. There is an increasing trend towards the application of digital technology to support control systems in order to achieve energy efficiency in buildings. This article introduces a holistic, integrated, building energy management model called `smart sensor, optimum decision and intelligent control' (SMODIC). The model takes into account occupants' responses to the indoor environments in the control system. The model of optimal decision-making based on multiple criteria of indoor environments has been integrated into the whole system. The SMODIC model combines information technology and people centric concepts to achieve energy savings in buildings.

Physiological expression of human thermal comfort to indoor operative temperature in the non-HVAC environment

A physiological experiment was carried out in a naturally ventilated, non-HVAC indoor environment of a spacious experimental room. More than 300 healthy university students volunteered for this study. The purpose of the study was to investigate the human physiological indicators which could be used to characterise the indoor operative temperature changes in a building and their impact on human thermal comfort based on the different climatic characteristics people would experience in Chongqing, China. The study found that sensory nerve conduction velocity (SCV) could objectively provide a good indicator for assessment of the human response to changes in indoor operative temperatures in a naturally ventilated situation. The results showed that with the changes in the indoor operative temperatures, the changing trend in the nerve conduction velocity was basically the same as that of the skin temperature at the sensory nerve measuring segment (Tskin(scv)). There was good coherent consistency among the factors: indoor operative temperature, SCV and Tskin(scv) in a certain indoor operative temperature range. Through self-adaptation and self-feedback regulation, the human physiological indicators would produce certain adaptive changes to deal with the changes in indoor operative temperature. The findings of this study should provide the baseline data to inform guidelines for the development of thermal environment-related standards that could contribute to efficient use of energy in buildings in China.

Minimum neighbour and extended Kalman filter estimator: a practical distributed channel assignment scheme for dense wireless local area networks

Dense deployments of wireless local area networks (WLANs) are becoming a norm in many cities around the world. However, increased interference and traffic demands can severely limit the aggregate throughput achievable unless an effective channel assignment scheme is used. In this work, a simple and effective distributed channel assignment (DCA) scheme is proposed. It is shown that in order to maximise throughput, each access point (AP) simply chooses the channel with the minimum number of active neighbour nodes (i.e. nodes associated with neighbouring APs that have packets to send). However, application of such a scheme to practice depends critically on its ability to estimate the number of neighbour nodes in each channel, for which no practical estimator has been proposed before. In view of this, an extended Kalman filter (EKF) estimator and an estimate of the number of nodes by AP are proposed. These not only provide fast and accurate estimates but can also exploit channel switching information of neighbouring APs. Extensive packet level simulation results show that the proposed minimum neighbour and EKF estimator (MINEK) scheme is highly scalable and can provide significant throughput improvement over other channel assignment schemes.

Blind channel estimation in multi-rate multicarrier DS-CDMA systems

Multi-rate multicarrier DS-CDMA is a potentially attractive multiple access method for future broadband wireless multimedia networks that must support integrated voice/data traffic. This paper proposes a subspace based channel estimation scheme for multi-rate multicarrier DS-CDMA, which is applicable to both multicode and variable spreading factor systems. The performance of the proposed scheme for these two multi-rate systems is compared via numerical simulations.

A new signaling scheme for one-shot near-far resistant detection in DS/CDMA

This paper proposes a new signaling scheme: orthogonal on-off BPSK (O3BPSK), for near-far resistant detection in the asynchronous DS/CDMA systems (up-link). The temporally adjacent bits from different users in the received signals are decoupled by using the on-off signaling, and the original data rate is maintained with no increase in transmission rate by adopting an orthogonal structure. The detector at the receiver is a one-shot linear decorrelating detector, which depends upon neither hard-decision nor specific channel coding. Some computer simulations are shown to confirm the theoretical analysis.

Particle image velocimetry measurements of turbulent flow within outdoor and indoor urban scale models and flushing motions in urban canopy layers

We investigate the spatial characteristics of urban-like canopy flow by applying particle image velocimetry (PIV) to atmospheric turbulence. The study site was a Comprehensive Outdoor Scale MOdel (COSMO) experiment for urban climate in Japan. The PIV system captured the two-dimensional flow field within the canopy layer continuously for an hour with a sampling frequency of 30 Hz, thereby providing reliable outdoor turbulence statistics. PIV measurements in a wind-tunnel facility using similar roughness geometry, but with a lower sampling frequency of 4 Hz, were also done for comparison. The turbulent momentum flux from COSMO, and the wind tunnel showed similar values and distributions when scaled using friction velocity. Some different characteristics between outdoor and indoor flow fields were mainly caused by the larger fluctuations in wind direction for the atmospheric turbulence. The focus of the analysis is on a variety of instantaneous turbulent flow structures. One remarkable flow structure is termed 'flushing', that is, a large-scale upward motion prevailing across the whole vertical cross-section of a building gap. This is observed intermittently, whereby tracer particles are flushed vertically out from the canopy layer. Flushing phenomena are also observed in the wind tunnel where there is neither thermal stratification nor outer-layer turbulence. It is suggested that flushing phenomena are correlated with the passing of large-scale low-momentum regions above the canopy.