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Conference Paper
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This paper presents results of path loss measurements, in two indoor environments for both LoS and NLoS scenarios across a frequency range from 0.6-73 GHz using the multi-band custom designed channel sounders developed at Durham University. The data are analysed to estimate the path loss parameters for each frequency band with either the close in p...

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Context 1
... the current measurements, the two sounders were used to measure nine frequency bands with a waveform duration of 819.2 μs, which gives 1.2 kHz waveform repetition rate. Table 1 gives a summary of the measured frequency bands, the measured bandwidth, and the corresponding processing bandwidth. For all the measurements, omni-directional antennas were used at the transmitter and at the receiver with the transmit antenna placed at a height close to the ceiling at 2.2-2.6 m as would be deployed in an access point and the receive antenna at 1.5-1.6 m which is typical for users' applications. ...
Context 2
... measurements were collected over 1-2 seconds and then processed with bandwidths ranging from 250 MHz to 2 GHz as given in Table 1, to obtain average power delay profiles (PDP). Each PDP was then used to estimate the received power above the estimated noise floor similar, to the procedure followed in [6]. ...


... The conventional procedure for calibration is to disconnect the antennas from the channel sounder and to calibrate the RF front ends between the antenna ports and the antennas separately. 1 To calibrate the front ends, a full two-port calibration is prescribed for vector network analyzer (VNA)-based systems [8], [13], [16]; other correlation-based systems employ a back-to-back method [9]- [12], [15]. These calibration procedures have been well established for years and so are relatively standard and straightforward, yet some do not calibrate the front ends at all [4]- [7]. 1. ...
... And to enable precision antenna de-embedding, it is spherical angle (AZ and EL) that must be estimated, yet only a few papers do [9]- [11], [16] -the others either estimate AZ only [12], [13] or no angle at all. Finally, although an antenna may be classified as omnidirectional [15], antenna gain is never truly omnidirectional in both planes and so its effects on estimated path gain cannot be ignored. ...
... In any case, when different channel sounders are deployed by different organizations to record measurements [14], a meaningful comparison across bands is difficult to obtain since specific calibration procedures will vary from organization to organization. This is true even when different channel sounders are used by the same organization [4]- [8], [15] since calibration is never perfect. The comparison is more meaningful when the same organization uses the same channel sounder across all bands, albeit with different antennas [9]- [12]. ...
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Millimeter-wave (mmWave) communications promise Gigabit/s data rates thanks to the availability of large swaths of bandwidth between 10–100 GHz. Although cellular operators prefer the lower portions of the spectrum due to popular belief that propagation there is more favorable, the measurement campaigns to confirm this – conducted by ten organizations thus far – report conflicting results. Yet it is not clear whether the conflict can be attributed to the channel itself – measured in different environments and at different center frequencies – or to the differences in the organizations’ channel sounders and sounding techniques. In this paper, we propose a methodology to measure mmWave frequency dependence, using the 26.5–40 GHz band as an example. The methodology emphasizes calibration of the equipment so that the measurement results represent the channel alone (and not the channel coupled with the channel sounder). Our results confirm that free-space propagation is indeed frequency invariant – a well understood phenomena but to our knowledge reported nowhere else at mmWave to date. More interestingly, we found that specular paths – the strongest after the line-of-sight path and so pivotal to maintaining connectivity during blockage – are the least invariant compared to weaker diffracted and diffuse paths.