In an implementation of directed wireless communication, a multi-beam directed signal system coordinates directed wireless communication with client devices. A transmit beam-forming network routes data communication transmissions to the client devices via directed communication beams that are emanated from an antenna assembly, and a receive beam-forming network receives data communication receptions from the client devices via the directed communication beams.

Directed wireless communication

Wireless products and systems are quickly becoming an integral part of professional and private life styles and are being used in a large variety of vehicular, public and private environments. The design of these systems requires an accurate characterization of the communications channel defined by the transmitting and receiving antennas and the specific propagation characteristics of the radio link involved. This paper surveys the typical antenna design choices as well as the various propagation models applicable to modern wireless communications systems.

Antennas and propagation for wireless communications

We present a system architecture for a broadband indoor wireless digital communications system, capable of supporting ATM at transport bit rates up to about 160 Mb/s for broadband LANs. Access is via a radio system with carrier frequencies within the 20 to 60 GHz range, because of the relative abundance of available bandwidth in this range. The system design is shaped by a set of service requirements, by the characteristics of indoor millimeter wave radio channels, and by the constraints and opportunities of the relevant device technologies. The design includes a multi-access microcellular architecture accommodating ATM traffic with a wide range of broadband and narrowband bit rates and services in an office environment. A modern configuration incorporating bandwidth spreading, signal processing, and coding measures to provide immunity to the effects of radio channel fading, multipath, shadowing, interference and noise, and millimeter-wave component limitations has been developed. The architecture exploits millimeter-wave and SAW device technologies to design and realize the various transceiver components in low-cost, low-power monolithic and/or hybrid form.

A system architecture for broadband millimeter-wave access to an ATM LAN

A multibeam beamformer in combination with a decision feedback equalizer is considered for the base station in a single-cell 100-Mb/s TDMA/TDD QPSK indoor wireless network at 24 GHz. The outage rate in terms of required SNR/bit/antenna is estimated using a statistical, clustered propagation model and for beam selection diversity and two-beam combining.

Multibeam antennas for indoor wireless communications

We report theoretical/numerical estimation of ultimate limits of bandwidth efficient delivery of high bit-rate digital signals indoors Specifically, we analyze the Crawford Hill Bell Laboratories building Single omni transmit and receive antennas are assumed The signals incur attenuation and distortion due to multipath and at high bit-rates this frequency selectivity causes ISI Moreover, there is impairment by gaussian noise Transmit power and bandwidth constraints limit communications efficiency We illustrate this limiting of efficiency in examples assuming 52 GHz carrier, 10 MHz bandwidth and up to 1 W transmitted power The experimentally based WiSE ray-tracing tool models the channels from a base on the ceiling to workspaces in various rooms Movement within a workspace causes channel changes Computing the probability distribution of capacity shows substantial capacity for the omni-omni case with 10 MHz bandwidth for 100 mW transmitted For the most distant offices, for at least 95% of the area in a workspace, we obtain 36 bps/Hz We also examine diversity methods, illustrating substantial gains with nth order optimum combining (OC(n)):OC(2) improves capacity by over 35% in rooms where capacity is the lowest while OC(4) improves it 70% We put the results in a pragmatic perspective by highlighting the bit-rates achievable with decision feedback equalization

Initial estimation of communication efficiency of indoor wireless channels

typically 60 dB (relative to 1 meter, averaged over the multipath fading), while the rms delay spread is typically on the order of ns ,2,31. This rms delay spread limits wireless communications at very high data rates (up the dab rate to about Mbps, Current station to cover the entire floor of an office building, to increase this hh rate to 20 Mbps, but the circuitry is relative to 1 meter. This feasibility depends on two maintaining reasonable outage probability with a 60 dB factors: received power mar@n and propagation loss (relative to 1 meter) may be difficult to achieve. spread. Based on results using the propagationHere we consider the use of phased arrays (tested in prediction techniques of [l], supported by that neither multicarriers, equalization, nor antenna the power margin and decrease the delay spread of the communication link are economical methods for of Gbps. Note that if the multipath in a building increasing the data rate substantially above 10 to 20 generated signals at the receiver that were uniformly In this paper, we consider the feasibility of indoor to multi-GbPs)* In Particular we wish to use One base props& consider equalization or multicarrier processing which may have in Of 6o propagation loss near the complexity limit for an economical system and experimental to 622 Mbps, we OW experiment by using directive antennas) to increase arrays with less than l6O0 at One end Of a signa] at the receiver, thereby permitting data rates in Mbps for room indoor coverage. distributed in power and delay spread with respect to However, based On the propagation-prediction angle-of-arrival, antenna arrays would not be useful. techniques Of and verified by Our experimental However, results using the propagation-prediction techniques of [l] for in-building propagation over an entire floor of the Crawford Hill Building show that this is not the case. In particular, our results show that arrays at the transmitter and receiver with 25" beamwidths can isolate one ray, with high probability, and thereby achieve nearly the full gain of the antennas and eliminate experimental results for 622 Mbps at 19 GHz from several locations within the Crawford Hill building, using manually-scanned directive (1 5' beamwidth) horn antennas. We have investigated ways of economically fabricating antenna arrays with these beamwidths, which, high data rates economically feasible. In Section 2 we discuss the data rate limitations due to power margin and delay spread. The effect of antenna arrays is in Section 3, using both propagationmeasurements using directive antennas (15' beamwidth) at both ends of a link between the center of the Crawford Hill building to an end laboratory, we have shown that high-speed ubiquitous communication is feasible. Using antenna arrays with 50 to 2oo at both the transmitter and data rates in excess of 1 Gbps. receiver, we expect to Obtain entire floor coverage at delay spread. To suppofi this conclusion, we present

J. H. Winters

Papers

High data rate indoor wireless communications using antenna arrays