Abstract
Local multipoint distribution systems (LMDS), which are operating worldwide in the frequency range of 26 to 43GHz, have large bandwidths of 0.1 up to 2 GHz but a limited area coverage of a few kilometers only. This is due to line-of-sight (LOS) constraints for reliable point-to-multipoint links as well as due to large propagation losses. The size of the macrocells illuminated by the base stations, where LOS exists, is approximately 1 to 5 km. As suggested in the CRABS report (1999), the maximal spectral efficiency can be obtained with a dual frequency and polarization reuse plan. This frequency and polarization reuse leads to interference. In this paper, we report a new technique that uses trellis-coded modulation (TCM) for increasing the capacity of LMDS networks. Analytical expressions have been derived for pairwise error probability for both high and low SNR scenarios. Numerical simulations have shown that using the proposed TCM schemes in cochannel cells have resulted in a large decrease in interference, thereby allowing us to reduce the frequency reuse distance. In this paper, we present the strategy using two TCM schemes that allow the frequency reuse factor of unity, without compromising on the QoS caused by increased interference. Design rules for constructing TCM schemes are also proposed in this paper.
Highlights
Broadband radio access systems operating at millimeter waves, often called local multipoint distribution systems (LMDS), are currently being developed in the 26–43 GHz frequency range, having bandwidths of 0.1 up to 2 GHz [1, 2, 3, 4]
− A f d2, p, where EIRPD and EIRPI are the equivalent isotropic radiated powers of the desired and interfered signals at the customer location, GR(θ) is the receiver antenna gain at an angle θ off the boresight, Lfs is the free space path loss, Acs is the attenuation during clear sky, A f is the short-term enhancement due to atmospheric multipath and focussing effects, p is the time percentage for which A f exceeds a certain value [12, 13], d1 and d2 are the distances in km from the base station (BS) of the desired and cochannel cell, respectively
In this paper we propose a new scheme to increase the capacity of interference-limited LMDS networks
Summary
Broadband radio access systems operating at millimeter waves, often called local multipoint distribution systems (LMDS), are currently being developed in the 26–43 GHz frequency range, having bandwidths of 0.1 up to 2 GHz [1, 2, 3, 4]. LMDS are local cellular point-to-multipoint radio systems, delivering broadband services from a central transmitter or base station (BS) to fixed customer stations (CS) mounted on individual buildings, blocks of apartments, or buildings of residential as well as business customers within its cell size [5] (http://www.iec.org/online/tutorials/lmds/). These broadband radio access systems offer rapid infrastructure deployment and the ability to provide local content. We propose to explore the possibility of using only a single frequency coupled with horizontal and vertical polarizations for the LMDS network.
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