EP0709982A1
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EP
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Medium access control scheme for wireless LAN using a variable length interleaved time division frame
Assignee: International Business Machines Corp
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Filing: 1994-10-26
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Granted: —
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Expires: 2014-10-26
Abstract
Abstract A Medium Access (MAC) Protocol is utilized for wireless access, preferrably over a radio frequency channel, for a plurality of remote stations to a base station on a LAN. The MAC protocol is based on a reservation scheme for user data traffic and a random access technique for control and signalling traffic. There is a time division frame structure in which time is slotted. Time slots are grouped into variable length periods. The variable frame structure consists of a frame header followed by interleaved periods of different types (type A, B or C). Type A periods are allocated to the outbound channel which is used for data transfer from the base station to the remote stations. Type B periods, are allocated to the inbound channel that is used for contention-free data transfer from the remote stations to the base station. Allocation of the data slots in the A and B periods is performed by the base station. Type C periods are reserved to the control channel used for transmission of reservation requests and data from the remote stations to the base station in a random-access contention mode using a slotted Aloha protocol. The duration and sequence of periods may be varied by using a technique for interleaving periods of different types. The base station estimates the number of actively transmitting remote stations utilizing feedback information from the remote stations. This estimate is broadcast to the remote stations as control indicia to control their transmission attempts in C slots, thus yielding high transmission efficiency.
Inventors
- 👤 Frédéric Jacques Bauchot
- 👤 Frédéric Bernard Soleil de Nice Lefevre
- 👤 Luc Louis Revardel
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 14:52
CPC Classifications
H; H04; H04W; H04W74/00; H04W74/02; H04L; H04L12/00; H04L12/64; H04W72/00; H04W72/50; H04W72/52; H04W74/04; H04W74/08; H04W84/00; H04W84/02; H04W84/10; H04W84/12
Claims Analysis
Total Claims: 37
Claim 1
Independent Claim
194 words
A digital communication system, of the type comprising: a plurality of remote stations, each including a transceiver for communication over a shared medium; a base station having a transceiver for communication over said shared medium with the transceivers of each of said plurality of remote stations, said base station including means for defining a sequence of time frames during which messages and data are transmitted over said shared medium, each said time frame being divided into at least three types (A, B, C) of time slots, type A time slot for outbound transmission from said base station to said plurality of remote stations, type B time slots for contention free inbound transmission from said plurality of remote stations to said base station and type C time slots for contention access by said plurality of remote stations for transmission over said shared medium, said system being characterized in that said defining means comprise: means responsive to traffic load for allocating in a given time frame a variable number of said type A, type B and type C slots; and means for interleaving within said given time frame groups of consecutive slots of the same type.
Claim 2
Dependent Claim
31 words
The system of claim 1 wherein said base station's and said remote stations' transceivers include frequency hopping radio signalling means and wherein said shared medium is a wireless radio frequency channel.
Claim 3
Dependent Claim
28 words
The system of claim 2 wherein said means for defining a time frame comprise means for spreading said given time frame over one or more frequency hopping periods.
Claim 4
Dependent Claim
22 words
The system of claim 3 wherein said interleaving means comprise means for inserting in said time frame time slots for frequency hopping.
Claim 5
Independent Claim
54 words
The system of anyone of the previous claims wherein said means for interleaving within said given time frame groups of consecutive slots of the same type, referred to as respectively type A, type B and type C periods, comprise means for inserting a type C period after each type A or type B period.
Claim 6
Independent Claim
41 words
The system of anyone of the previous claims wherein said means for interleaving type A, type B and type C periods within said time frame comprise means for inserting a type C period at the end of said given time frame.
Claim 7
Independent Claim
97 words
The system of anyone of the previous claims wherein said means for allocating said time slots comprise: first means for queuing outbound transmission requests and second means for queuing inbound transmission requests; means which, in response to said interleaving means, dequeue one or more pending requests from either said first queuing means or said second queuing means; and means responsive to said dequeuing means for assigning a given period in said time frame to said one or more pending requests, said given period being type A for outbound transmission requests and type B for inbound transmissions requests.
Claim 8
Dependent Claim
35 words
The system of claim 7 wherein said interleaving means comprise means for causing said dequeuing means to alternatively dequeue one or more pending requests from respectively said first queuing means and said second queuing means.
Claim 9
Dependent Claim
60 words
The system of claim 7 or 8 wherein said interleaving means comprise means for causing said dequeueing means to dequeue in sequence one or more pending requests from said first queuing means, respectively said second queuing means, if said second queuing means, respectively said first queuing means is empty, until the duration of said given periods exceeds a predetermined value.
Claim 10
Independent Claim
32 words
The system of claims 7 or 8 or 9 wherein said interleaving means comprise means for causing said assigning means to insert a type C period between two consecutive said given periods.
Claim 11
Independent Claim
36 words
The system of anyone of the previous claims wherein said interleaving means comprise means for limiting the total number of successive type A, B and C periods in each said time frame to a predetermined value.
Claim 12
Independent Claim
49 words
The system of anyone of the previous claims wherein said base station further include means for including control indicia in a transmission from said base station to a given remote station that is indicative of the probability of said given remote station gaining access during said type C slots;
Claim 13
Dependent Claim
33 words
The system of claim 12 including means for providing an indication in a transmission from each said remote station to said base station of whether a given transmission of data is a retransmission.
Claim 14
Dependent Claim
32 words
The system of claim 13 including means for computing said control indicia as a function of said indications in transmissions from each said remote station over one or more said time frames.
Claim 15
Dependent Claim
27 words
The system of claim 14 wherein said means for computing said control indicia include means for recomputing said control indicia from one time frame to the next.
Claim 16
Independent Claim
37 words
The system of claims 14 or 15 wherein said means for computing said control indicia include means for computing said indicia as a function of an estimate of the number of said remote stations contending for access.
Claim 17
Dependent Claim
56 words
The system of claim 14 or 15 or 16 wherein said means for computing said control indicia include means for computing said control indicia as a function of the ratio of the number of C slots in which a successful transmission from one of said remote stations occurs, relative to the total number of C slots.
Claim 18
Independent Claim
73 words
The system of claims 14 or 15 or 16 or 17 wherein said means for computing said control indicia include means for computing said control indicia as a function of the ratio of the number of C slots in which said remote stations succeeded on a first attempt to transmit to said base station relative to the total number of remote stations that succeeded in an attempt to transmit to said base station.
Claim 19
Independent Claim
31 words
The system of anyone of the previous claims wherein said type C slots are dedicated to contention access by said plurality of remote stations for inbound transmission to said base station.
Claim 20
Independent Claim
196 words
A medium access control (MAC) method in a digital communication system of the type comprising a plurality of remote stations, each including a transceiver for communication over a shared medium and a base station having a transceiver for communication over said shared medium with the transceivers of each of said plurality of remote stations, said method including the steps of defining a sequence of time frames during which messages and data are transmitted over said shared medium, each said time frame being divided into at least three types (A, B, C) of time slots, type A time slot for outbound transmission from said base station to said plurality of remote stations, type B time slots for contention free inbound transmission from said plurality of remote stations to said base station and type C time slots for contention access by said plurality of remote stations for transmission over said shared medium, said method being characterized in that it further comprises the steps of: allocating in a given time frame a variable number of said type A, type B and type C slots; and interleaving within said given time frame groups of consecutive slots of the same type.
Claim 21
Dependent Claim
47 words
The method of claim 20 wherein said base station's and said remote stations' transceivers use frequency hopping radio signaling said shared medium being a radio frequency channel and wherein said method includes the step of spreading said given time frame over one or more frequency hopping periods.
Claim 22
Dependent Claim
19 words
The method of claim 21 comprising the step of inserting in said time frame time slots for frequency hopping.
Claim 23
Independent Claim
59 words
The method of anyone of claims 20 to 22 wherein the step of interleaving within said given time frame groups of consecutive slots of the same type (A, B, C), referred to as respectively type A, type B and type C periods, comprise the step of inserting a type C period after each type A or type B period.
Claim 24
Independent Claim
43 words
The method of anyone of claims 20 to 23 wherein the step of interleaving type A, type B and type C periods within said time frame comprise the step of inserting a type C period at the end of said given time frame.
Claim 25
Independent Claim
85 words
The method anyone of claims 20 to 24 wherein said step of allocating said time slots comprise the steps of: queuing outbound transmission requests in a first queue and queuing inbound transmission requests in a second queue; dequeuing one or more pending requests from either said first queue or said second queue; and assigning a given period in said time frame to said one or more pending requests, said given period being type A for outbound transmission requests and type B for inbound transmissions requests.
Claim 26
Dependent Claim
31 words
The method of claim 25 wherein said dequeuing step include the step of alternatively dequeuing one or more pending requests from respectively said first queue and said second queue in sequence.
Claim 27
Independent Claim
52 words
The method of claims 25 or 26 wherein said dequeuing step include the step of dequeuing in sequence one or more pending requests from said first queue, respectively said second queue, if said second queue, respectively said first queue is empty, until the duration of said given periods exceeds a predetermined value.
Claim 28
Independent Claim
38 words
The method of anyone of claims 20 to 27 wherein said interleaving step comprise the step of limiting the total number of successive type A, B and C periods in each said time frame to a predetermined value.
Claim 29
Independent Claim
47 words
The method of anyone of claims 20 to 28 further including the step of including control indicia in a transmission from said base station to a given remote station that is indicative of the probability of said given remote station gaining access during said type C slots;
Claim 30
Dependent Claim
60 words
The method of claim 29 further including the steps of: providing an indication in a transmission from each said remote station to said base station of whether a given transmission of data is a retransmission; and computing said control indicia as a function of said indications in transmissions from each said remote station over one or more said time frames.
Claim 31
Dependent Claim
19 words
The method of claim 30 wherein said step of computing said control indicia is performed for each time frame.
Claim 32
Independent Claim
34 words
The method of claims 30 or 31 wherein said step of computing said control includes computing said indicia as a function of an estimate of the number of said remote stations contending for access.
Claim 33
Independent Claim
54 words
The method of claims 30 or 31 or 32 wherein said step of computing said control indicia include computing said control indicia as a function of the ratio of the number of C slots in which a successful transmission from one of said remote stations occurs, relative to the total number of C slots.
Claim 34
Independent Claim
71 words
The method of claims 30 or 31 or 32 or 33 wherein said step of computing said control indicia includes computing said control indicia as a function of the ratio of the number of C slots in which said remote stations succeeded on a first attempt to transmit to said base station relative to the total number of remote stations that succeeded in an attempt to transmit to said base station.
Claim 35
Independent Claim
32 words
The method of anyone of claims 20 to 34 wherein said type C slots are dedicated to contention access by said plurality of remote stations for inbound transmission to said base station.
Claim 36
Dependent Claim
17 words
Base station apparatus comprising means for carrying out the method of anyone of claims 20 to 35.
Claim 37
Dependent Claim
17 words
Remote station apparatus comprising means for carrying out the method of anyone of claims 20 to 35.
References Cited (Backward Citations)
CA2115211A1
Cited
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