Bus arbitration infrastructure for deployment of wireless networks

• US 5,771,462 A
• Filed: 07/07/1995
• Issued: 06/23/1998
• Est. Priority Date: 07/07/1995
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Olsen, Claus Michael
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Bhattacharya, Sam
• Application Number:
  US08/499,534
• Time in Patent Office: 1,082 Days
• Field of Search: 455/33.4, 455/34.1, 455/51.2, 455/54.1, 455/56.1, 455/422, 455/450, 455/502, 455/503, 455/517, 455/524, 375/356
• US Class Current: 455/524
• CPC Class Codes: H04W 74/04 Scheduled access hybrid access H04W74/02
• CPC Class Codes: H04W 74/0816 with collision avoidance
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/085 Access point devices with remote components

Abstract

A method and apparatus for expanding the physical coverage area of a wireless communications network. More specifically, a number of transceivers are connected in a series configuration to a single base station, and each transceiver transmits signals to selected portions (subcells) of the physical coverage area. Each transceiver is connected to a delay unit where all of the delay units are adjusted so that downlink signals transmitted from the single base station will be transmitted from the transceivers to their respective subcells in phase with each other. Since all of the downlink signals from each of the transceivers result from the same downlink signal from the base station and since they are in phase with each other, a wireless unit anywhere in the physical coverage area will receive a downlink signal which is error free. Further, with this invention, when uplink signals are transmitted simultaneously from a number of wireless units in different subcells of the physical coverage area to the transceivers, the selection units will instantaneously select one and only one uplink signal to be received by the base station. Any one of the other simultaneously transmitted signals will be rejected throughout the duration of their signal.

Claims

1. In a wireless network having a base station which communicates with a plurality of wireless units in a physical coverage area, apparatus for expanding said physical coverage area of said base station, said coverage area having a plurality of subcells, said apparatus comprising:

a. a plurality of transceivers connected in both a downlink direction and an uplink direction to said base station, said transceivers being connected only in the downlink direction through a time delay mechanism for providing respective time delays in the transmission of downlink signals from said base station to said transceivers so that said downlink signals are transmitted from each of said transceivers to said wireless units in phase with each other, each of said transceivers transmitting said downlink signals into a respective one of said subcells and receiving uplink signals from said wireless units located in said respective one subcell, each said transceiver also being connected to a selection unit, said selection units together selecting from among all said wireless units transmitting an uplink signal to said transceivers at any given time a single uplink signal from a single wireless unit in only one subcell so that said selected single uplink and only said selected single uplink signal is received by said base station over an entire duration of said selected single uplink signal irrespective of other uplink signals being transmitted to said transceivers simultaneously by other wireless units.

2. An apparatus as recited in claim 1, wherein each said selection unit selects the received uplink signal that arrives first and blocks all other received uplink signals that arrive later than the selected uplink signal until the selected uplink signal has been completely forwarded to the base station, each said selection unit comprising a pair of inputs, where each of said inputs can receive a signal from one of said subcells, where said each selection unit will forward only one signal from one of said subcells at any given time, and wherein each said selection unit will forward a signal S from one of said inputs if and only if there is no other signal being forwarded from another input when S arrives at said one input of said selection unit.

3. An apparatus as recited in claim 2, wherein said selection unit will forward a signal S from one of said inputs if and only if said signal S arrives at said one input a certain minimum time after another signal has been completely forwarded from any one of said inputs.

4. An apparatus as recited in claim 2 wherein said pair of inputs are simultaneously connected to an output of said selection unit if and only if there is no signal present at any of said inputs and wherein one of said inputs I₁ is disconnected from said output if a signal should arrive at the other input I₂, and wherein I₁ is reconnected to said output when there are no signals present on any of said inputs.

5. An apparatus as recited in claim 2, further comprising means for broadcasting an alert busy signal from said base station to indicate one of said wireless units is currently transmitting an uplink signal when said uplink signal is being transmitted.

6. An apparatus as recited in claim 1, wherein said delay mechanism comprises a plurality of flip-flop circuits connected to each other in a series configuration through a plurality of switches and a clock recovery circuit for generating a clock signal that is synchronized with an input signal of said delay unit, wherein said switches are used to select a desired delay.

7. In a wireless network having a base station which communicates with a plurality of wireless units in a physical coverage area, an apparatus for expanding said physical coverage area of said base station, with said coverage having a plurality of subcells, said apparatus comprising:

a. a plurality of selection units connected to each other in a series configuration along the length of an uplink interconnection extending from said base station;

b. a plurality of transceivers, each transceiver being connected to one of said selection units, and each transceiver transmitting signals to and receiving signals from said wireless units which are in one of said subcells, wherein said series configuration of said selection units will forward to the base station a single uplink signal from only one subcell at any given time, said forwarded uplink signal being an earliest uplink signal transmitted by any one of said wireless units and being forwarded during an entire duration of said earliest uplink signal; and

c. a plurality of delay mechanisms, where an output of each of said delay mechanisms is connected to one of said transceivers and where an input of each of said delay mechanisms is connected to a shared downlink interconnect extending from said base station, where each delay mechanism provides delay so that signals transmitted from said base station through said transceivers and to said wireless units will be transmitted from said transceivers in phase with each other.

8. An apparatus as recited in claim 7, wherein said series configuration of said selection units will block any uplink signal that any one of said wireless units begins to transmit to said base station while said earliest uplink signal is being forwarded to said base station, said selection units blocking said any uplink signal for the entire duration of said any uplink signal.

9. In a wireless network having a base station which communicates with a plurality of wireless units in a physical coverage area, an apparatus for expanding said physical coverage area of said base station, with said coverage area having a plurality of subcells, said apparatus comprising:

a. a plurality of selection units connected to each other in a spanning tree configuration, with said base station connected to a root of said tree;

b. a plurality of delay units connected to said base station through said spanning tree configuration; and

c. a plurality of transceivers, with each of said transceivers connected to one of said selection units and one of said delay units, each of said transceivers for transmitting and receiving signals to and from wireless units in one of said subcells,

each of said selection units forwarding uplink signals towards the root of said tree configuration to said base station from only one of said subcells at a time, said selection units together forwarding to said base station a first uplink signal to be transmitted by a wireless unit after a previous uplink signal has been completely forwarded to said base station and wherein a signal from only one of said subcells can be transmitted to said base station at any given time, and

each of said delay units providing delay at each of said transceivers so that a signal broadcasted from said base station through said tree configuration will be transmitted from each of said transceivers to said wireless units in phase with each other.

10. A selector unit for forwarding a first signal to arrive at said selector unit without delay while completely blocking all other signals that arrive at said selector unit while said first signal is being forwarded, said unit comprising:

a. an output;

b. K inputs I.sub. through I_K ;

c. means for providing simultaneous connections from all of said K inputs to said outputs if and only if there are no signals on any of said K inputs;

d. means for disconnecting all of said K inputs except for a j-th input I_j of said K inputs if a signal arrives at said j-th input while there are no signals on any other of said K inputs; and

e. means for reconnecting said disconnected inputs I₁ through I_j-1 and I_j+1 through I_K after said signal on I_j has been completely forwarded to said output, each of said disconnected inputs being reconnected to said output if and only if there is no signal present on said each input and if and only if there is no signal being forwarded to said output on any other of said inputs.

11. An apparatus as recited in claim 10, wherein said inputs are connected to outputs of other selector units and/or to other signal sources and wherein said output is connected to an input of another selector unit or to a base station.

12. An apparatus as recited in claim 10 wherein said selection unit will forward a signal S from one of said K inputs if and only if said signal S arrives at any of said inputs a certain minimum time after another signal has been completely forwarded from one of said inputs.

13. An adjustable delay circuit for regenerating a received digital stream with a desired delay, said circuit comprising:

a. a plurality of flip-flop circuits connectable to each other in a series configuration;

b. a clock recovery circuit for generating a clock signal in phase with said digital stream, said clock signal for simultaneously clocking each of said flip-flop circuits; and

c. a plurality of switches, each of said switches connecting an output of a flip-flop to either an input of a next one of said flip-flops or to an output of said delay circuit, wherein a number of said flip-flop circuits are connected to each other in a series configuration by setting a number of said switches to connect to inputs of said number of flip-flop circuits so as to obtain said desired delay.

14. In a wireless communications network having a plurality of wireless units WU₁,WU₂, . . . , WU_M, capable of communicating with a base station when in a defined coverage area, a method of controlling the flow of signals between said wireless units and said base station of said network, said method comprising:

a. transmitting a plurality of RTS signals from a number of said wireless units to said base station within a predefined time period, each said RTS signal indicating a request to transmit data signals or control signals from a corresponding one of said wireless units;

b. storing those of said plurality of RTS signals which are received by said base station;

c. sequentially transmitting a plurality of CTS signals from said base station, each said CTS signal indicating that one of said wireless units may transmit a data signal or a control signal to said base station, wherein each of said CTS signals is immediately followed by the transmission of a data signal or a control signal from one of said wireless units until each of said number of wireless units has transmitted at least one data signal or one control signal to said base station in accordance with said RTS signals.

15. In a wireless communications network having a plurality of wireless units WU₁, WU₂, . . . , WU_M, capable of communicating with a base station when in a defined coverage area, a method of controlling the flow of signals between said wireless units and said base station of said network, said method comprising:

a. transmitting a plurality of RTS signals from a number of said wireless units to said base station within a predefined time period T_RTS, each said RTS signal indicating a request to transmit a DATA packet from a corresponding one of said wireless units;

b. storing those of said plurality of RTS signals which are received by said base station;

c. transmitting a CTS signal from said base station after said time period T_RTS in response to one of said received RTS signals, said CTS signal indicating that one of said wireless units may transmit a DATA packet to said base station;

d. transmitting said DATA packet from said one wireless unit;

e. transmitting from said base station an ACK signal to said wireless unit immediately followed by another CTS signal, said ACK signal indicating that said DATA packet was received and said other CTS signal indicating that one of said wireless units may transmit a DATA packet to said base station; and

f. repeating step (e) for each RTS signal stored in said base station until all said DATA packets indicated by said stored RTS signals have been transmitted to said base station.

16. In a wireless communications network having a plurality of wireless units WU₁, WU₂, . . . , WU_M, capable of communicating with a base station when in a defined coverage area, a method of controlling the flow of signals between said wireless units and said base station of said network, said method comprising:

a. transmitting a plurality of RTS signals from a number of said wireless units to said base station within a predefined time period T_RTS, each said RTS signal indicating a request to transmit a DATA packet from a corresponding one of said wireless units;

b. storing those of said plurality of RTS signals which are received by said base station;

c. transmitting a CTS signal from said base station after said time period T_RTS in response to one of said received RTS signals, said CTS signal indicating that one of said wireless units may transmit a DATA packet to said base station;

d. transmitting said DATA packet from said one wireless unit;

e. transmitting from said base station an ACK signal to said wireless unit immediately followed by another CTS signal, said ACK signal indicating that said DATA packet was received and said other CTS signal indicating that one of said wireless units may transmit a DATA packet to said base station;

f. repeating step (e) for each RTS signal stored in said base station until all said DATA packets indicated by said stored RTS signals have been transmitted to said base station,

said method further comprising transmitting an RTS signal to a wireless unit, said wireless unit responding by transmitting a CTS signal to said base station, said base station responding by transmitting a DATA packet to said wireless unit, said wireless unit responding by transmitting an ACK signal to said base station and wherein this exchange of RTS CTS DATA and ACK signals occur outside of said time period T_RTS.

17. A method as recited in claim 16, further comprising periodically transmitting control signals from said base station to said wireless units, said control signals setting the duration of said time period T_RTS and indicating the number of times a wireless unit may submit the same RTS signal within said time period T_RTS.

18. In a wireless communications network having a plurality of wireless units WU₁,WU₂, . . . , WU_M, capable of communicating with a base station when in a defined coverage area, an apparatus for controlling the flow of signals between said wireless units and said base station of said network, said apparatus comprising:

a. means for transmitting a plurality of RTS signals from a number of said wireless units to said base station within a predefined time period, each said RTS indicating a request to transmit data signals or control signals from a corresponding one of said wireless units;

b. means for storing those of said plurality of RTS signals which are received by said base station;

c. means for sequentially transmitting a plurality of CTS signals from said base station, each said CTS signal indicating that one of said wireless units may transmit a data signal or a control signal to said base station, wherein each of said CTS signals is immediately followed by the transmission of a data signal or a control signal from one of said wireless units until each of said number of wireless units has transmitted at least one data signal or one control signal to said base station in accordance with said RTS signals.