EP0621708A2
Expired / Lapsed
EP
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An adaptive medium access control scheme for wireless LAN
Assignee: International Business Machines Corp
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Filing: 1994-04-13
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Granted: —
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Expires: 2014-04-13
Abstract
Abstract A Medium Access (MAC) Protocol is utilized for wireless radio access 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 fixed frame structure in which time is slotted, and time slots are grouped into fixed frames consisting of data and control subframes or periods. The fixed frame structure consists of three periods (A, B, and C) along with their respective headers. The first period, the A period, is the outbound channel which is used exclusively for data transfer from the base station to the remote stations. The following period, the B period, is the inbound channel that is used for contention-free data transfer from the remote stations to the base station. The allocation of the data slots in the A and B periods is performed by the base station. The last period of the frame, designated as the C period, is the control channel used for the 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 of the three periods may be varied using a movable boundary technique. 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 the C period, thus yielding high transmission efficiency.
Inventors
- 👤 Hamid Ahmadi
- 👤 David Frederick Bantz
- 👤 Frederic Jacques Bauchot
- 👤 Arvind Krishna
- 👤 Richard Orville La Maire
- 👤 Kadathur S. Natarajan
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 13:20
CPC Classifications
H; H04; H04W; H04W74/00; H04W74/02; H04W48/00; H04W48/08; H04W48/12; H04W84/00; H04W84/02; H04W84/10; H04W84/12
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
157 words
In a digital data radio communication system, the combination comprising: a plurality of remote stations, each of which includes a transceiver; a base station having a transceiver for radio communications with the transceivers of each of said plurality of remote stations, said base station including: means for defining a plurality of frames during which messages and data are transmitted, each of said plurality of frames being divided into three intervals, the first interval for transmission from said base station to said plurality of remote stations, the second interval for contention free transmission from said plurality of remote stations to said base station, and the third interval for contention access by said plurality of said remote stations for transmission to said base station; and 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 third interval.
Claim 2
Dependent Claim
56 words
The combination claimed in claim 1, wherein said third interval is divided into a plurality of sub-intervals in each of which a remote station may contend for access to transmit to said base station, and wherein said control indicia includes the probability of a remote station gaining access in a given sub-interval of said third interval.
Claim 3
Dependent Claim
35 words
The combination claimed in claim 2, including: means for providing an indication in a transmission from a remote station to said base station of whether or not a given transmission of data is a retransmission.
Claim 4
Dependent Claim
32 words
The combination claimed in claim 3, including: means for computing said control indicia as a function of said indication in a transmission from each of said remote stations in a given frame.
Claim 5
Dependent Claim
24 words
The combination claimed in at least one of claims 1 to 4, wherein said control indicia is recomputed from one frame to the next.
Claim 6
Dependent Claim
40 words
The combination claimed in at least one of claims 1 to 5, including means for changing said control indicia from one frame to the next as a function of an estimate of the number of remote stations contending for access.
Claim 7
Dependent Claim
78 words
The combination claimed in claim 6, wherein said third interval is divided into a plurality of sub-intervals in each of which a remote station may transmit to said base station, and wherein said means for changing said control indicia includes: means for computing said control indicia as a function of the ratio of the number of sub-intervals in which a successful transmission from a remote station to the base station occurs relative to the total number of sub-intervals.
Claim 8
Dependent Claim
69 words
The combination claimed in claim 6 or 7, wherein said means for changing said control indicia includes: means for computing said control indicia as a function of the ratio of the number of sub-intervals in which a remote station succeeds on its first attempt to transmit to the base station relative to the total number of remote stations that succeeded in an attempt to transmit to the base station.
Claim 9
Dependent Claim
45 words
The combination claimed in at least one of claims 1 to 8, wherein each of said frames are of a fixed length, including means for varying the duration of each of said three intervals as a function of the message traffic load of the system.
Claim 10
Dependent Claim
25 words
The combination claimed in at least one of claims 1 to 9, including: means for insuring that said third interval has a predetermined minimum duration.
Claim 11
Dependent Claim
64 words
The combination claimed in at least one of claims 1 to 10, including: means for insuring that the second interval transmission time is greater than a minimum of a predetermined threshold or the transmission time for scheduled traffic in the second interval, and means for insuring that the first interval transmission time has priority over the second interval transmission time that exceeds said minimum.
Claim 12
Dependent Claim
84 words
The combination claimed in at least one of claims 1 to 11, wherein each of the three intervals are divided into slots, where the slot sizes in the first and second intervals are equal in size and are referred to as regular sized slots and each accommodates one wireless data packet, and the slots in the third interval are mini-slots which are smaller by a predetermined factor than the slots in the first and second interval, with each such mini-slot accommodating one control packet.
Claim 13
Dependent Claim
48 words
The combination claimed in claim 12, wherein the number of slots in the first, second and third intervals are TA, TB and TC, respectively, and said predetermined factor is the ratio of the regular sized slots relative to the mini-slots, with this ratio being referred to as R:1.
Claim 14
Dependent Claim
31 words
The combination claimed in claim 13, including: means for computing TA, TB and TC for a fixed frame size TF, according to the constraint: TF = TA + TB + TC/R.
Claim 15
Independent Claim
161 words
A method of operating a digital data radio communication system which includes a plurality of remote stations, each of which includes a transceiver, and a base station having a transceiver for radio communications with the transceivers of each of said plurality of remote stations, said method comprising the steps of: defining a plurality of frames, at said base station, during which messages and data are transmitted, each of said plurality of frames being divided into three intervals, the first interval for transmission from said base station to said plurality of remote stations, the second interval for contention free transmission from said plurality of remote stations to said base station, and the third interval for contention access by said plurality of remote stations for transmission to said base station; and 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 third interval.
Claim 16
Independent Claim
283 words
A method of operating a digital data radio communications system which includes a plurality of remote stations, each of which includes a transceiver, and a base station having a transceiver for radio communications with the transceivers of each of said plurality of remote stations, said method comprising the steps of: defining a plurality of frames, at said base station, of fixed frame length, each of said frames being divided into three periods A, B and C with each period being divided into slots, including headers, with the slot sizes in the A and B periods being equal in size and being referred to as regular sized slots, and each accommodating one wireless data packet, with the slots in the C period being mini-slots which are smaller by a predetermined factor than the slots in the A and B periods, with each such mini-slot accommodating one wireless control packet, with the A period being for communications from said base station to said plurality of remote stations, the B period being for allocated communications from said plurality of remote stations to said base station, and the C period being for access by contention for communications from said remote stations to said base station; varying the duration of each of the A, B and C periods as a function of message traffic load on the system; and including control indicia in one of the A, B and C periods that is indicative of the probability of a remote station gaining access for communication to said base station in the C period, including means for changing said control indicia from one frame to the next as a function of the number of remote stations contending for access.
Claim 17
Dependent Claim
141 words
In a digital data radio communications system the combination comprising: a plurality of remote stations, each of which includes a transceiver; a base station having a transceiver for radio communications with the transceivers of each of said plurality of remote stations, said base station including means for defining a plurality of frames during which information is transmitted between said plurality of remote stations and said base station, with a portion of each frame being allocated for contention access by said plurality of remote stations for transmission to said base station; means for providing an estimation of the number of remote stations that attempt to transmit based on feedback information in transmissions from remote stations in at least a previous frame; and means for a remote station to determine whether to transmit in a given frame as a function of said estimation.
Claim 18
Dependent Claim
173 words
In a digital data radio communications system the combination comprising: a plurality of remote stations, each of which includes a transceiver; a base station having a transceiver for radio communications with the transceivers of each of said plurality of remote stations, said base station including means for defining a plurality of frames during which information is transmitted between said plurality of remote stations and said base station, with a portion of each frame being allocated for contention access by said plurality of remote stations for transmission to said base station; means for providing an indication in a transmission of information from a remote station to said base station of whether or not there has been a previous attempt to transmit this information; means for providing an estimation of the number of remote stations that attempt to transmit based on said indication in transmissions from remote stations in at least a previous frame; and means for a remote station to determine whether to transmit in a given frame as a function of said estimation.
References Cited (Backward Citations)
No citation records indexed.
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