FREQUENCIES in the 20–60-GHz range are being considered for their wider allocated bandwidths and compact sized devices [1], [2]. However, path loss and absorption due to
typical building materials are higher at these frequencies than at cellular and PCS frequencies [1]. To compensate for this loss and reduce multipath spread, multibeam antennas have been considered [3], [4]. Driessen [5] showed that, with proper placement and pointing of a 15 beamwidth horn antenna at one end of the link and with a 45 or 70 beamwidth antenna at the other end of the link, 622 Mb/s BPSK and 1.244 Gb/s QPSK links without equalization could be established at 19 GHz with error-free performance for
many indoor locations. Gans et al. [6] concluded from a link budget analysis based
on a ray-tracing model that beam forming arrays with at least 50 elements at both ends of the link are required to achieve the long range and high bit rate of Driessen’s [5]. They also considered the required number of taps in a decision feedback equalizer
(DFE) versus the beam width, assuming an omnidirectional antenna at the user transmitter and a continuously steerable directionalantenna at the base station (BS) receiver [6]. In this paper, we consider the same general architecture as the second Gans model described above, but for a shorter range (50 ft) and a lower bit rate of 100 Mb/s. We assume a certain configuration of four linear beamformers (only discrete
beam-pointing choices) and a statistical (azimuth-only) propagation model that emphasizes clustering of paths in angle and delay [7]. This model has the significant delay spread in a narrow angular region that was mentioned in a caveat in [6]. In addition, we consider the use of tapering to reduce crossover loss and the use of two beams simultaneously (jointly equalized) for angle diversity. So, while our system requires no manual pointing of antennas, it does have the complexity of an equalizer.We assume TDMA/TDD QPSK, a very slowly varying channel (based on pedestrian movement), no interference, and beam selection on the uplink based simply on power. In cellular or unlicensed band applications consistent with high levels of interference, more robust beam-selection criteria are required to combat the “beam-falsing” problem [8]. Our link budget analysis is reported elsewhere [9]; in this paper,we consider onlySNRimprovements offered by various changes in BS receiver design. In particular,
we determine the tradeoffs between the amount of tapering, the number of angle diversity beams (one or two), the total number of beams, and the number of forward taps in the DFE.