Wireless digital communication system having hierarchical wireless repeaters with autonomous hand-off

• US 5,883,884 A
• Filed: 04/22/1996
• Issued: 03/16/1999
• Est. Priority Date: 04/22/1996
• Status: Expired due to Fees

• Current Assignee: Alwin C. Michaelson, Roger F. Atkinson
• Original Assignee: Alwin C. Michaelson, Roger F. Atkinson
• Inventors: Atkinson, Roger F.
• Primary Examiner(s): Jung, Min
• Application Number:
  US08/636,218
• Time in Patent Office: 1,058 Days
• Field of Search: 370/328, 370/329, 370/330, 370/331, 370/321, 370/332, 370/337, 370/347, 370/315, 370/319, 370/480, 370/481, 370/277, 370/279, 370/280, 370/293, 455/33.2, 455/33.4, 455/15, 455/16, 455/17, 455/20
• US Class Current: 370/279
• CPC Class Codes: H04B 7/2606 Arrangements for base station coverage control, e.g. by using relays in tunnels
• CPC Class Codes: H04W 16/26 Cell enhancers or enhancement, e.g. for tunnels, building shadow
• CPC Class Codes: H04W 36/00 Hand-off or reselection arrangements
• CPC Class Codes: H04W 72/04 Wireless resource allocation
• CPC Class Codes: H04W 74/04 Scheduled access hybrid access H04W74/02

Abstract

In a wireless communication system, a base unit transmits outgoing TDM signals within a base transmission coverage area at a first frequency. Repeaters in the base coverage area receive the outgoing signal and retransmit it within respective repeater coverage areas at respective frequencies, maintaining the same time slot orientation in TDM format. Several levels of repeaters form a hierarchy covering an expanded range. Remote subscriber units located in a coverage area receive the strongest outgoing frequency signal from a repeater/base unit in a time slot assigned to that unit for a particular call, which time slot is maintained for that call through successive levels of repeaters. Incoming TDMA signals from remote units use the same time slots used in received outgoing signals. The base unit transmits outgoing signals and receives incoming signals at the same frequency, but at different times. Each repeater receives outgoing signals from a lower level repeater (or from the base unit) at the transmission frequency of that lower level repeater, and immediately retransmits the signal in its own coverage at a different frequency. Incoming signals transmitted to any particular repeater from a remote unit in its coverage area, or from a higher level repeater, are at the outgoing transmission frequency for that repeater. Repeaters and remote units can switch between repeaters to communicate with the base unit depending upon received signal strength, thereby providing minimal interruption during communication.

Claims

1. A wireless communication system in which a system base station in communication with an external communications network transmits an outgoing signal to multiple remote system subscriber units as time division multiplex (TDM) bursts of multiple sequential time slots containing outgoing call information, and receives an incoming signal from the multiple remote units as time division multiple access (TDMA) bursts of multiple sequential time slots containing incoming call information, wherein said outgoing signal bursts and said incoming signal bursts alternate in time, and wherein each call between a remote unit and the base station has its information contained in a respective time slot, said system comprising:

a plurality of repeaters for receiving and retransmitting signals, said repeaters being positionally spaced from one another and from said base station and having, along with said base station, a respective plurality of transmission coverage areas in which signal transmissions from respective repeaters and from the base station can be received by remote units and/or other repeaters, wherein each transmission coverage area and its repeater have a level designation corresponding to the number of repeaters through which signals from the base station must be retransmitted to reach said each repeater, and wherein each repeater relays said outgoing signal to and from other repeaters and remote units located in the transmission coverage area of said each repeater;

wherein said base station includes means for transmitting said outgoing signal and receiving said incoming signal at a first carrier frequency;

wherein the repeaters in the transmission coverage area of said base station have a first of said level designations and include;

means for receiving said outgoing signal from said base station at said first carrier frequency and retransmitting said outgoing signal at a second carrier frequency different from said first carrier frequency; and

means for receiving said incoming signal at said second carrier frequency and retransmitting said incoming signal to said base station at said first carrier frequency, wherein said second carrier frequency at different first level repeaters may be the same or different depending upon whether or not the transmission coverage areas for those first level repeaters overlap; and

wherein each of said remote units includes;

means for automatically selecting the carrier frequency of the strongest of the outgoing signals received from the base station and repeaters; and

means for communicating at said selected carrier frequency, via the appropriate time slots in said outgoing and incoming signals, with the repeater or base station transmitting said strongest outgoing signal.

2. The system of claim 1 wherein repeaters located in the transmission coverage area of a first level repeater have a second of said level designations and include:

means for receiving said outgoing signal from one of said first level repeaters at the second carrier frequency of that first level repeater and retransmitting said outgoing signal at a third carrier frequency different from that second carrier frequency; and

means for receiving incoming signals at said third carrier frequency and retransmitting said incoming signals to said one, of said first level repeaters at the second carrier frequency of said one of said first level repeaters;

wherein the third carrier frequency at different second level repeaters may be the same or different depending upon whether the transmission coverage areas for those second level repeaters overlap.

3. The system of claim 2 wherein each of said repeaters include a common transmitter for alternately transmitting said outgoing signal and at least portions of said incoming signal.

4. The system of claim 1 wherein repeaters at any level j, where j is greater than one, receive said outgoing signals from and transmit said incoming signals to a repeater at level (j-1) at a common carrier frequency, wherein said common carrier frequency may be the same or different at different repeaters depending upon whether or not the transmission coverage areas for those repeaters overlap.

5. The system of claim 4 wherein each repeater includes means responsive to call information in a time slot of the outgoing signal directed thereto for transmitting call information back toward the base station in a time slot of the incoming signal sequentially corresponding to the time slot of the outgoing signal containing the call information.

6. The apparatus of claim 5 wherein each of said repeaters includes means for receiving said outgoing signal at a carrier frequency in a portion of a prescribed frequency band and for retransmitting said outgoing signal at a carrier frequency in another portion of said prescribed frequency band.

7. The system of claim 5 wherein each of said repeaters include a common transmitter for alternately transmitting said outgoing signal and at least portions of said incoming signal.

8. A method for expanding wireless communication beyond the transmission coverage area of a base station serving to connect multiple remote subscriber units to a communication network, wherein said base station transmits an outgoing signal to the remote subscriber units in TDM bursts having multiple time slots each containing data for a respective call between a respective remote subscriber unit and said network, and wherein the base station receives an incoming signal from said remote subscriber units in TDMA bursts having multiple time slots each containing data for said respective call, said method comprising the steps of:

(a) transmitting said TDM bursts from said base station and transmitting said TDMA bursts from said remote subscriber units at different alternating times;

(b) expanding the transmission coverage area of the base station via at least a first repeater located in the transmission coverage area of said base station, said first repeater having a transmission coverage area extending beyond the base station transmission coverage area;

(c) transmitting said TDM bursts as a base station outgoing signal at a first carrier frequency throughout the base station transmission coverage area;

(d) in response to receiving said base station outgoing signal at said first repeater, transmitting said TDM bursts as a first repeater outgoing signal at a second carrier frequency throughout the first repeater transmission coverage area;

(e) in response to a current call between said network and an active remote subscriber unit located in the first repeater transmission coverage area, receiving said first repeater outgoing signal at said active remote subscriber unit and processing a time slot of said TDM burst assigned to said current call;

(f) transmitting to said first repeater from said active remote subscriber unit information in a time slot of said TDMA burst assigned to the current call at said second frequency as part of a first repeater incoming signal; and

(g) retransmitting from said first repeater to said base station at said first carrier frequency, as part of a first repeater incoming signal, the time slot of said TDMA burst transmitted by said active remote subscriber unit.

9. The method of claim 8 further comprising the steps of:

(h) expanding the transmission coverage areas of the first repeater and base station via a second repeater located in the first repeater transmission coverage area but outside the base station transmission coverage area, said second repeater having a transmission coverage area extending beyond the first repeater transmission coverage area;

(i) in response to receiving said first repeater outgoing signal at said second repeater, transmitting said TDM bursts as a second repeater outgoing signal at a third frequency throughout the second repeater transmission coverage area;

(j) in response to a further current call between said network and a further active remote subscriber unit located in the second repeater transmission coverage area, receiving said second repeater outgoing signal at said further active remote subscriber unit and processing a time slot of said TDM burst assigned to said further current call;

(k) transmitting to said second repeater from said further active remote subscriber unit information in a time slot of said TDMA burst assigned to the further current call at said third frequency as part of a second repeater incoming signal;

(l) retransmitting from said second repeater to said first repeater at said second carrier frequency, as part of a second repeater incoming signal, the time slot of said TDMA burst transmitted by said further active remote subscriber unit; and

(m) retransmitting from said first repeater to said base station at said first carrier frequency, as part of said first repeater incoming signal, the time slot of said TDMA burst transmitted by said further active remote subscriber unit.

10. In a wireless communication system configured in hierarchical levels of repeaters, a method for transferring information comprising the steps of:

(a) interfacing a base station to a switching network to relay inbound and outbound communications;

(b) transmitting said outbound communications of said switching network in the form of outbound signals from said base station to said hierarchical levels of repeaters successively and transmitting said inbound communications successively through said hierarchical levels of repeaters and said base station in the form of inbound signals to relay said inbound communications to said switching network, wherein said inbound signals include multiple sequential inbound time slots containing incoming information from a final destination and said outbound signals include multiple sequential outbound time slots containing outgoing information from said switching network; and

(c) at each hierarchical level of repeaters;

(c.1) receiving said outbound signals at a first frequency of particular band and retransmitting said outbound signals at a second different frequency of said particular band; and

(c.2) receiving said inbound signals at said second frequency and retransmitting said inbound signals at said first frequency;

wherein said outbound communications traverse said base station and each hierarchical level of repeaters until reaching said final destination, and said inbound communications originate at said final destination and traverse said hierarchical levels of repeaters in reverse order and said base station until reaching said switching network.

11. The method of claim 10 wherein step (c.1) further comprises determining said second frequency based on frequencies not in use.

12. The method of claim 10 wherein step (c.1) further comprises determining from which level to receive said outbound signals based upon received signal strength.

13. The method of claim 10 wherein step (c.1) further comprises setting said first and second frequencies at opposite halves of said particular band.

14. The method of claim 10 wherein steps (c.1) and (c.2) comprise reusing said first and second frequencies at repeaters having non-overlapping transmission coverage areas.

15. In a wireless communication system, a repeater for retransmitting communications comprising:

an antenna for receiving and radiating inbound and outbound communications, wherein said inbound communications include multiple sequential inbound time slots containing incoming information from a communication destination and said outbound communications include multiple sequential outbound time slots containing outgoing information from a communication source;

a receiver for receiving said inbound and outbound communications at reception frequencies;

a receiver synthesizer for setting said reception frequencies;

a transmitter for transmitting said received inbound and outbound communications at transmission frequencies;

a transmitter synthesizer for setting said transmission frequencies;

at least one duplexer for passing signals to said receiver and controlling access to said antenna between said transmitter and said receiver by controlling simultaneous operation of said transmitter and receiver; and

a microcontroller for monitoring received signal quality of said inbound and outbound communications and controlling said transmitter and receiver synthesizers to set said transmission and reception frequencies at different parts of a particular frequency band, said microcontroller further including means for controlling said at least one duplexer to pass appropriate portions of a received band to said receiver and controlling access to said antenna by said transmitter and receiver.

16. In a wireless communication system wherein a system base station in communication with a communications network transmits an outgoing signal to multiple remote system subscriber units as time division multiplex (TDM) bursts of multiple sequential time slots containing outgoing call information and receives an incoming signal from the multiple remote units as time division multiple access (TDMA) bursts of multiple sequential time slots containing incoming call information, a method comprising the steps of:

(a) transmitting said outgoing signal bursts and said incoming signal bursts in time alternation;

(b) storing information for each call between a remote unit and the base station in a respective time slot;

(c) receiving and retransmitting said outgoing and incoming signals via a plurality of repeaters positionally spaced from one another and from said base station having, along with said base station, a plurality of respective transmission coverage areas in which signal transmissions from respective repeaters and from the base station can be received by remote units and/or other repeaters, wherein each transmission coverage area and its repeater have a level designation corresponding to the number of repeaters through which signals from the base station must be transmitted to reach said each repeater, wherein the repeaters in the transmission coverage area of said base station have a first of said level designations, and wherein each repeater relays said outgoing signals to and from other repeaters and remote units located in the transmission coverage area of said each repeater;

(d) at said base station, transmitting said outgoing signal and receiving said incoming signal at a first carrier frequency;

(e) at each first level repeater, receiving said outgoing signal from said base station at said first carrier frequency and retransmitting said outgoing signal at a second carrier frequency different from said first carrier frequency, and receiving said incoming signals at said second carrier frequency and retransmitting said incoming signals to said base station at said first carrier frequency, wherein said second carrier frequency at different first level repeaters may be the same or different depending upon whether or not the transmission coverage areas for those first level repeaters overlap; and

(f) at each of said remote units, automatically selecting the carrier frequency of the strongest of the outgoing signals received from the base station and repeaters, and communicating at said selected carrier frequency and via the appropriate time slots in said outgoing and incoming signals with the repeater or base station transmitting said strongest outgoing signal.

17. The method of claim 16 further comprising the steps of:

(g) receiving and retransmitting said incoming and outgoing signals via second level repeaters positionally spaced in the transmission coverage area of said first level repeaters; and

(h) at said second level repeaters, receiving said outgoing signal from one of said first level repeaters at the second carrier frequency of that first level repeater and retransmitting said outgoing signal at a third carrier frequency different from that carrier frequency, and receiving incoming signals at said third carrier frequency and retransmitting said incoming signals to said one of said first level repeaters at the second carrier frequency of said one of said first level repeaters.

18. The method of claim 17 further comprising the step of, at each repeater, alternate 14 transmitting via a common transmitter said outgoing signal and at least portions of said incoming signal.

19. The method of claim 16 wherein repeaters at any level j, where j is greater than one, receive said outgoing signals from and transmit said incoming signals to a repeater at level (j-1) using a common carrier frequency, wherein said common carrier frequency may be the same or different at different repeaters depending upon whether or not the transmission coverage areas for those repeaters overlap.

20. The method of claim 19 futher comprising the step of, at each repeater, incrementing a level count in the retransmitted outgoing signal to identify the level designation of each repeater.

21. The method of claim 20 wherein step (g) further includes:

(g.1) selecting the carrier frequency of the strongest of the outgoing signals by selecting the carrier frequency of the outgoing signal received from the base station or repeater having the lowest level count.

22. A wireless communication system configured in hierarchical levels of repeaters for interfacing a switching network to transfer information comprising:

a base station for interfacing said switching network to relay inbound and outbound communications; and

a plurality of repeaters arranged in hierarchical levels wherein said base station transmits said outbound communications from said switching network in the form of outbound signals to said hierarchical levels of repeaters successively and said hierarchical levels of repeaters transmit said inbound communications in the form of inbound signals successively to said base station to relay said inbound communications to said switching network, wherein said inbound signals include multiple sequential inbound time slots containing incoming information from a final destination and said outbound signals include multiple sequential outbound time slots containing outgoing information from said switching network;

wherein each repeater within a hierarchical level includes;

means for receiving said outbound signals at a first frequency of a particular band and retransmitting said outbound signals at a different frequency of said particular band; and

means for receiving said inbound signals at said second frequency and retransmitting said inbound signals at said first frequency;

wherein said outbound communications traverse each hierarchical level of repeaters and said base station until reaching said final destination, and said inbound communications originate at said final destination and traverse said hierarchical levels of repeaters in reverse order and said base station until reaching said switching network.

23. The system of claim 22 wherein each repeater further includes a controller to determine said second frequency based on frequencies not in use.

24. The system of claim 22 wherein each repeater futher includes a controller to determine from which level to receive said outbound signals based upon received signal strength.

25. The system of claim 22 wherein each repeater further includes a controller to set said first and second frequencies at opposite halves of said particular band.

26. The system of claim 22 wherein each repeater futher includes means for reusing said first and second frequencies at repeaters having non-overlapping transmission coverage areas.