Medium access control scheme for wireless LAN using a variable length interleaved time division frame
First Claim
1. A digital communication system 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;
a 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 of time slots, a first type A time slot for outbound transmission from said base station to said plurality of remote stations, a second type B time slot for contention free inbound transmission from said plurality of remote stations to said base station and a third type C time slot for contention access by said plurality of remote stations for transmission over said shared medium said defining means further includinga means responsive to traffic load on said shared medium for allocating in a given time frame a variable number of said type A, type B and type C slots; and
a means for interleaving within said given time frame groups of consecutive slots of the same type.
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Accused Products
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.
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Citations
35 Claims
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1. A digital communication system comprising:
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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; a 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 of time slots, a first type A time slot for outbound transmission from said base station to said plurality of remote stations, a second type B time slot for contention free inbound transmission from said plurality of remote stations to said base station and a third type C time slot for contention access by said plurality of remote stations for transmission over said shared medium said defining means further including a means responsive to traffic load on said shared medium for allocating in a given time frame a variable number of said type A, type B and type C slots; and a means for interleaving within said given time frame groups of consecutive slots of the same type. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A medium access control 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 comprising the steps of:
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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 of time slots, a type A time slot for outbound transmission from said base station to said plurality of remote stations, a type B time slots for contention free inbound transmission from said plurality of remote stations to said base station and a type C time slots for contention access by said plurality of remote stations for transmission over said shared medium; 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. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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Specification