Telecommunications – Carrier wave repeater or relay system – Two separate way transmission
Patent
1995-03-27
1997-10-14
Pham, Chi H.
Telecommunications
Carrier wave repeater or relay system
Two separate way transmission
455 14, 455 17, 455 334, 370279, 370293, 379 61, H04B 7212
Patent
active
056781776
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to RF repeaters for use in cordless telephone systems and, more particularly, for interfacing with cordless handsets and cordless base stations exchanging transmit and receive signals using time division duplex transmissions and is also applicable to frequency division duplex (FDD) transmissions.
The present RF repeater is useful in particular in telephone systems employing cable television plant as a signal conduit but may also be employed in cordless telephone systems utilizing dedicated coaxial cable and/or fibre optic and/or microwave signal conduits.
BACKGROUND ART
It is expected that Personal Communication Services (PCS) microcells will be supporting a rapidly increasing number of handsets in North America in the near future. To support this user base it is essential that the PCS microcells be both low power to assist frequency re-use and low cost, because the net capital costs of the PCS microcells will be a major factor in the economic viability of PCS.
What has been suggested by a number of organizations is that existing cable television distribution plant be used to interconnect microcell equipment. Taking advantage of the broadband and the nearly ubiquitous nature of cable plant, it has been further proposed that the microcell equipment consist of simple RF repeaters that translate off-air mobile voice traffic onto the cable plant and vice versa.
This approach uses the cable plant as a RF combining/splitting network since it preserves the basic RF amplitude and phase/frequency information. What has become apparent in tests is that this approach to PCS microcells yields both low capital costs and improved user service.
In summary, the low cost arises from the combination of simple technology, i.e. an RF repeater, using an existing asset base i.e. cable plant in a fashion that allows modulation/demodulation and public switched telephone network (PSTN) interface equipment to be centrally located. This allows these equipment costs to be amortised over a very large net coverage area.
The improved service arises from better call blocking probability associated with the ability to centralize the base station equipment rather than a priori allocation to specific microcells. Additionally, the cable plant can act to form distributed antenna arrays that can be shaped into "roamer corridors". Within these roamer corridors it is also possible to control the off-air dynamic range so as to reduce near user/far user interactions and line of sight blocking.
FIG. 1 illustrates the principal hardware elements and concepts of a prior art cordless telephone system employing base stations.
Base stations 1 operate at the off-air frequencies and perform demodulation and modulation functions for the telephone signals. The base stations 1 interface directly to twisted pair telecom lines.
The base stations 1 can be mounted to interface directly with nearby handsets (not shown), or can be located at a central site, as shown, where their ability to handle calls can be amortised over a larger network of microcells connected by TV cable plant, as mentioned above.
A remote antenna signal processor RASP 2 is located at the central site and interfaces one of the base stations to cable plant 4.
Typically, signals from the base stations 1 travel over the cable plant to the handsets in the 200-450 Mhz band. Signals travelling in the reverse direction use the 5-30 Mhz return band on the cable plant.
Bi-directional distribution amplifiers 6 need to be compatible with the cable plant 4 and provide return band capability.
Remote antenna drivers (RADs) 8 must be compatible with existing TV cable plant and they may be configured for either coaxial cable or fiber plant.
RADs 8 pick-up the off-air signals and relay then back to a central site via the plant's return path, and also broadcast PCS signals on the cable forward path (200-450 Mhz) to nearby handsets, after suitable heterodyne operations.
This prior art RAD-RASP design suffers a number of limitations, which comprise, specifically:
REFERENCES:
patent: 4234959 (1980-11-01), Andrea, III et al.
patent: 5187803 (1993-02-01), Sohner et al.
patent: 5321736 (1994-06-01), Beasley
patent: 5369728 (1994-11-01), Kawano et al.
patent: 5377255 (1994-12-01), Beasley
2777321 Canada Ltd.
Pham Chi H.
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