Method and apparatus employing delay elements in multiple diversity paths of a wireless system repeater translator to allow for selective diversity and automatic level control in a time-division multiple access system

• US 6,088,570 A
• Filed: 11/24/1998
• Issued: 07/11/2000
• Est. Priority Date: 11/24/1998
• Status: Expired due to Term

• Current Assignee: Hanger Solutions, LLC (IP Investments Group LLC)
• Original Assignee: AirNet Communications Corporation (Tecore Incorporated)
• Inventors: Foley, Stephen J., Smith, Jeffrey W., Schmutz, Thomas R., Komara, Michael A.
• Primary Examiner(s): TO, DORIS HA
• Application Number:
  US09/198,485
• Time in Patent Office: 595 Days
• Field of Search: 455/11.1, 455/422, 455/501-502, 455/504, 455/506, 455/517, 455/524, 455/63, 455/67.1, 455/65, 455/67.3, 455/561, 455/101, 455/132-136, 455/272 , 455/277.1-278.1, 455/296, 370/321, 370/347
• US Class Current: 455/11.1
• CPC Class Codes: H04B 7/0802 using antenna selection H04B7/0868 takes precedence; antenna beam directivity switching H01Q3/24
• CPC Class Codes: H04B 7/0828 with delay elements in antenna paths
• CPC Class Codes: H04B 7/15542 Selecting at relay station its transmit and receive resources selection of wireless resources by user or terminal H04W72/02; arrangements affording multiple use of the transmission path by two-dimensional division of the resources H04L5/0003, or by allocating sub-channels H04L5/003
• CPC Class Codes: H04B 7/2606 Arrangements for base station coverage control, e.g. by using relays in tunnels
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

In a conventional Time Division Multiple Access (TDMA) wireless system, the specified distance between a mobile unit and the base transceiver system (BTS) cannot exceed predetermined distances because of time slot synchronization constraints. Furthermore, varying distances between mobile units and the BTS, as well as Rayleigh fading, caused by destructive interference effects between direct and reflected signals, create extreme signal strength variations in the initial uplink signal from the mobile stations. The use of spatially-diverse antennas for receiving uplink signals provides diversity gain and mitigates deep fades. Furthermore, selecting the stronger of the spatially-diverse uplink signals mitigates deep fades and reduces frequency usage in the backhaul frequency band. In this approach to extending TDMA system coverage, in-band translator components are located in the center of remote cells which would normally contain a base transceiver system (BTS). The in-band translators include delay elements to implement slot-by-slot selective spatial diversity and automatic level control in a predictive feedforward fashion. The selective diversity mitigates deep Rayleigh fades, while the dynamic automatic level control drastically reduces the uplink backhaul dynamic range to allow for greater backhaul distances. Predictive feedforward automatic level control also eliminates overload and saturation of the backhaul high power amplifier, normally caused by wide variations in uplink power levels.

Claims

1. In a cellular communication system comprising a plurality of cells, the plurality of cells being located substantially adjacent one another, and the cellular communication system operating over a specified frequency range, the cellular communication system making use of a frequency allocation plan that arranges the cells into clusters wherein only one of said cells within said cluster contains a broadband base transmitter station, the cellular communication system comprising:

an in-band translator apparatus located in each of said cluster of cells not containing said broadband base transmitter station, wherein said in-band translator apparatus employs delay elements to implement selective spatial diversity on a slot-by-slot basis.

2. A cellular telecommunications system as in claim 1, where said in-band translator apparatus employs delay elements to implement automatic level control.

3. A cellular telecommunications system as in claim 2, where said automatic level control is implemented in a predictive feedforward fashion.

4. A cellular communication system comprising a plurality of cells, the plurality of cells being located substantially adjacent one another, and the cellular communication system operating over a specified frequency range, the cellular communication system making use of a frequency allocation plan that arranges the cells into clusters, the system comprising:

a home base station including a multicarrier broadband base transceiver system for receiving and transmitting multiple radio signals on multiple respective carrier frequencies, including a demodulator for demodulating said received radio signals and for coupling demodulated signals to a switching means, and means for modulating signals received from the switching means and coupling them for radio transmission on the multiple carrier frequencies;

a plurality of in-band translator means, each of said plurality of in-band translator means located in a respective one of said plurality of cells in the cluster, each of said plurality of in-band translator means further including;

first translator means for receiving a first uplink signal from a mobile station located in the respective one of said plurality of cells and translating a carrier frequency of said first uplink signal to a first divergent carrier frequency within the specified radio frequency range to produce a first backhaul signal, said first translator means further including first delay means for receiving and delaying said first backhaul signal;

second translator means for receiving a second uplink signal from said mobile base station means and translating a carrier frequency of said second uplink signal to a second divergent carrier frequency within the specified radio frequency range, to produce a second backhaul signal, said second translator means further including second delay means for receiving and delaying said second backhaul signal,

detection means for determining the instantaneous power level of said first backhaul signal and the instantaneous power level of said second backhaul signal,

comparison means for comparing the instantaneous power level of said first backhaul signal to the instantaneous power level of said second backhaul signal,

selection means for selecting the one of said first divergent carrier frequency and said second divergent carrier frequency having the highest instantaneous power level, and then connecting said backhaul signal for transmission to the home base station means using said selected one of said first divergent carrier frequency and said second divergent carrier frequency having the highest instantaneous power level.

5. A cellular telecommunications system as in claim 4, where said second uplink signal received by said second translator means is spatially diverse from said first uplink signal.

6. A cellular telecommunications in-band translator comprising:

first translator means for receiving a first uplink signal from a mobile station located in the cell served by said in-band translator and translating a carrier frequency of said first uplink signal to a first divergent carrier frequency to produce a first backhaul signal, said first translator means further including first delay means for receiving and delaying said first backhaul signal,

second translator means for receiving a second uplink signal from said mobile base station and translating a carrier frequency of said second uplink signal to a second divergent carrier frequency to produce a second backhaul signal, said second translator means further including second delay means for receiving and delaying said second backhaul signal,

detection means for determining the instantaneous power level of said first backhaul signal and the instantaneous power level of said second backhaul signal,

comparison means for comparing the instantaneous power level of said first backhaul signal to the instantaneous power level of said second backhaul signal,

selection means for selecting the one of said first divergent carrier frequency and said second divergent carrier frequency having the highest instantaneous power level, and then connecting said backhaul signal for transmission to the home base station means using said selected one of said first divergent carrier frequency and said second divergent carrier frequency having the highest instantaneous power level; and

attenuation means for implementing automatic level control of said selected divergent carrier frequency signal to provide constant backhaul transmit power on a slot-by-slot basis for a GSM/TDMA waveform.

7. The cellular telecommunications in-band translator of claim 6, wherein said attenuation means implements automatic level control of said selected divergent carrier frequency signal based on the detected level of said selected divergent carrier frequency signal.