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Home Cell Phones Wireless-telephone-distribution-system-with-time-and-space-diversity-transmission-for-determining-receiver-location

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Details
Inventors: Bolgiano, D. Ridgely; LaVean, Gilbert E.;
Assignee: Interdigital Technology Corporation (Wilmington, DE)
Primary Examiner: Blum; Theodore M.
Assistant Examiner:
Attorney, Agent or Firm:

A wireless communication system combines time and space diversity to reduce fading and simplify receiver design. In particular, a data packet which carries digital telephone traffic, is transmitted at three different times from three different antennas. The mobile subscriber receiver thus receives the same data packet at three different times from three different antennas, and uses the best data packet or combination of the data packets to reduce the effects of fading. A transfer station receives a time division multiplex multiple access (TDMA) signal from a base station carrying telephone data packet traffic to form three data packet repeats at spatially diverse antennas locations. The transfer station further modulates a code division multiple access (CDMA) system using a TDMA signal which links the mobile subscriber receiver to the transfer station. Each data packet received at the transfer station is thus retransmitted at three different times to the mobile subscriber station on a CDMA link. In one embodiment, each transfer station includes the three space diversity antennas. In a second embodiment, three transfer stations, each with one spatially diverse antenna is used. The time division and code division multiplex signals transmitted from space diversity antennas provide the ability to determine subscriber location using the same communication signals which are used for the primary telephone data communication. Specifically, the subscriber station receiver uses the absolute and relative time of arrival of the three repeated data packets to determine the respective distances of the mobile subscriber station to the three transmitting antennas. Since the transmitting antennas are at known fixed locations, receiver location is determined.

DETAILED DESCRIPTION SYSTEM DESCRIPTION--FIRST EMBODIMENT FIGS.
1, 2, 3, 8, 9 In a first embodiment of the invention shown in FIG.
1, a mobile user having an antenna 10 is coupled to a CDMA transfer station 14.
The CDMA transfer station 14 further includes an antenna T, 16, antenna A, 11, antenna B, 12, and antenna C, 13.
Antennas A, B and C can be mounted either on separate structures as is shown, or on a single mast.
The only physical requirement is that the space between antennas should be sufficient for uncorrelated space diversity.
While a quarter wavelength spacing may be sufficient, at least ten wavelengths is preferable.
At 1 GHz, 10 wavelengths is about 30 feet, while at 5 GHz, 10 wavelengths is about 6 feet.
The mobile subscriber antenna 10 (also referred herein as the user terminal antenna, or the subscriber station antenna, or simply antenna U) is coupled by a bidirectional radio link to antennas A, B and C.
The CDMA transfer station 14 is further coupled by a bidirectional radio link through antenna T through appropriate switching to the public switch telephone network.
In operation, forward channel telephone voice traffic received in data packets on antenna T is transmitted on antenna A during time slot 1, repeated on antenna B during time slot 2, and further repeated on antenna C during time slot 3.
All three repeated data packets are sequentially received on antenna 10.
In the reverse direction, data packets representing telephone voice traffic transmitted from antenna 10 are substantially simultaneously received on antennas A, B and C.
The CDMA transfer station 14 further retransmits data packets received in the reverse direction through antenna T back to the telephone network.
FIG.
2 is an overview diagram of a system in accordance with the present invention that includes the different interconnections between the supporting network, i.
e.
, between the public switched network 20 and switching center and central processor 22, and the CDMA transfer stations 26, 28, 30, 32, 34, 36 and 38


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