Ncr Corporation

Johannes P Haagh

Adriaan Kamerman

Hans Van Driest

Wilhelmus J Diepstraten

Gerrit Smit

A wireless local area network (10) including a plurality of stations (12) utilizes dynamic transmit power level control such that only the power level needed for reliable transmission to a particular station (12) is utilized. Each transmitted information packet (80) contains a byte (92) representing the power level at which the packet (80) was transmitted. The power level at which the packet (80) is received is measured and a path attenuation value is calculated, averaged over a plurality of packets and utilized, together with a measured interference level also transmitted in the packet (80), to determined a transmit power level for that path. Also determined is an associated defer threshold level. The transmit power levels and associated defer threshold levels are stored in a table (270).

Power control method in a wireless communication system

A local area network system (10) includes a host computer (14) connected in a wired LAN (12) with a plurality of bridges (18). The bridges (18) further connect with respective wireless LANs (100, 200, . . . , 600) which operate on a common wireless communication channel and contain respective pluralities of terminals (102, 202, . . . , 602). When a download operation is effected for initially starting up a new added terminal (e.g. 102-1), the bridges (18) are adapted to identify download message frames issued by the host computer (14) and retransmit each such frame (400) over the wireless communication channel in non-overlapping time intervals by applying respective different delays. Also, each download message frame is transmitted twice by each of the bridges (18).

Method of transmitting selected message frames without individual

A radio LAN station is provided for receiving information frames including start and end delimiters and user data therebetween. The start and end delimiters include both data symbols and special non-data symbols. The data symbols and non-data symbols being transmitted to the radio LAN station are sent thereto via a spread spectrum signal. The data symbols and the non-data symbols are spread via first and second spreading codes, respectively. The receiving radio LAN station includes first and second correlators which respectively correlate the received spread spectrum signal against the first spreading code to retrieve the data symbols and against the second spreading code to retrieve the non-data symbols. Rectangular representations of the received data and non-data symbols are thus produced and are converted to polar form via appropriate rectangular to polar converters. The polar representations of the data and non-data symbols respectively exhibit a vector length Z and a vector length Z'. The receiving LAN station includes circuitry for determining that a symbol is a data symbol if Z - Z' is greater than or equal to a constant A, or that a symbol is a non-data symbol if Z - Z1 is less than said constant A. In this manner, the data and non-data symbols representing the start and end delimiters are detected.

Radio LAN station with improved frame delimiter detection in a spread

A data modem communication system includes a data modem transmitter adapted to transmit data on a main channel at a relatively high bit rate and to transmit data at a relatively low bit rate on a secondary channel. At the receiver, a single analog-to-digital converter (54) supplies digital signals via a notch filter (58) to the main channel receiver (60) and to the secondary channel receiver (62) wherein a single IIR low-pass digital filter (110) is utilized for processing at three different sample rates to eliminate the main channel signal with frequency conversion taking place between processing at the first and second sample rates. The invention enables the provision of a reliable secondary channel while using a minimum amount of circuitry for complex-valued digital signal processing.

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Eindhoven, Netherlands

Johannes P Haagh