Apple Inc.

Richard W Mincher

Kerry E Lynn

Edward W Geiger

Jonathan M Zweig

Stanley L Fickes

Jeffrey L Mullins

Aspects for achieving and utilizing synchronization among end stations in a wireless local area network (WLAN) are provided. In a method aspect, the method includes receiving a packet with a time synchronization field value from a first end station in a second end station of a communication group. The method further includes comparing upon receipt of the packet the time synchronization field value with a local time value in the second end station to determine whether the local time value requires updating to maintain synchronization between the first and second end stations. The comparing further determines whether a difference between the time synchronization field value and the local time value is greater than zero, and when the difference is greater than zero, the local time value is updated to the time synchronization field value. In a system aspect, the system includes at least two end stations, wherein each of the at least two end stations further includes a local clock unit, and a transmit/receive control unit coupled to the local clock unit. A time synchronization field register in the transmit/receive control unit stores a value of the local clock unit, with one of the at least two end stations comparing a time synchronization field register value of a packet upon receipt from another of the at least two end stations with a value of the local clock unit to determine whether updating of the local clock unit is necessary.

Method and system for synchronization in a wireless local area network

Method and system aspects for increasing throughput in a WLAN are provided. In a method aspect, a packet is transmitted from a first end station in the WLAN, the packet including an indication of a next end station in a chain of end stations having data ready for transmission in the WLAN. The method further includes transferring control of access before a predetermined time period has been exceeded to the next end station in the chain of end stations based upon the indicator. In addition, the method includes maintaining access to the network for a plurality of cooperating end stations established through continuous indication of the next end station in the chain of end stations without exceeding a maximum access time. In a system aspect, the system includes a first end station, the first end station transmitting a packet in the WLAN, and a second end station in a chain end stations cooperating with the first end station and acknowledging the packet from the first end station before a predetermined time period has been exceeded, the second end station identifying a next end station in the chain end of end stations to have access in the WLAN. Further, transmission access to the WLAN continues with the next end station in the chain end stations when the predetermined time period is not exceeded between transmitting and acknowledging.

Method and system for increasing throughput in a wireless local area

A system for sending and responding to information requests in a wireless communications network includes a display device, a central processing unit, memory means including random access memory and read-only memory, an input device, and a transmitter/receiver. The random access memory further comprises routines for processing, sending and receiving messages over the wireless network. The present invention also comprises a method for requesting information and a method for responding to requests for information. The preferred method for handling information requests comprises the steps of: monitoring the communications channel for availability; sending an information request over the channel; receiving the information request at each node within the network; preparing responses to the information request at each node; and sending the response to the information request over the channel if it is available. The method for responding to a request for information advantageously uses the minimum number of request to solicit the minimum number of replies to the information request.

System and method for sending and responding to information requests in

A method and apparatus for decryption using cache storage wherein imported ciphertext is decrypted to produce unencrypted plaintext data. As a communication sequence containing an initialization vector and a block of ciphertext is imported, the initialization vector is applied to a cache and to a decoder. The initialization vector is then compared with other initialization vectors stored in the cache to determine whether the specific initialization vector has previously been received and stored. If the specific initialization vector is found to be stored in the cache, then the PN sequence associated with that initialization vector is written to the decoder, and the stored PN sequence is used to decode the imported ciphertext. If a determination is made that the initialization vector has not been previously received, then the read cache signal instructs the multiplexer to connect the PN generator to the decoder, and the initialization vector is used to generate a new PN sequence. In order to improve the efficiency of future ciphertext decoding utilizing this specific initialization vector, the PN sequence associated with the initialization vector is then stored in the cache together with its corresponding initialization vector. When the next block of ciphertext is received using the same initialization vector, the PN sequence need not be regenerated by the PN generator, but rather may be read from the cache as a stored sequence.

Method and apparatus for decryption using cache storage

A distributed time synchronization system and method synchronizes nodes within a frequency hopping spread spectrum (FHSS) local area network (LAN) group to a virtual master clock value. Each node system of the present invention comprises a CPU, an input device, a display device, a printer or hard copy device, a given amount of RAM and ROM memory, a data storage device, a local clock, a transmitter/receiver, an antenna, a virtual master clock processor, and a common data bus. The method of the present invention comprises the inclusion of a node's local clock value in a message just prior to transmission over the network, storage of a node's local clock value in RAM after an incoming message has been received, and the calculation of the time delay between the sending node and the receiving node by the virtual master clock processor. The virtual master clock processor utilizes this time delay in maintaining a virtual master clock value, which it uses in adjusting the value of the node's local clock at periodic intervals. This synchronizes the receiving node to the virtual master clock value. If the magnitude of the time delay exceeds a maximum allowed value, the magnitude is clamped to the maximum allowed value, thereby maintaining synchronization within a predetermined tolerance. A node can receive a message transmitted over the FHSS LAN regardless of the message address. Synchronization is therefore maintained without requiring a node to be able to communicate with any specific node within the FHSS LAN group.

Distributed time synchronization system and method

A digital encryption structure allows the varying of the computational overhead by selectively reusing, according to the desired level of security, a pseudorandom encoding sequence at the transmitter end and by storing and reusing pseudorandom decoding sequences, associated with one or more transmitters at the receiver end. A public initialization vector is combined with a secret key to produce a deterministic sequence from a pseudorandom number generator. This pseudorandom sequence in turn, is used to convert plaintext to ciphertext. The sequence may be selectively reused by storing the sequence to a transmitter memory cache and iteratively reading the sequence from memory according to a counter which controls the level of security of the encryption system. The ciphertext is decrypted on the receiver end by invertibly combining the ciphertext with the same pseudorandom sequence used by the transmitter to originally encode the plaintext. The pseudorandom sequence is independently generated by the receiver end using the original key and initialization vector used in the transmitter end. Once generated in the receiver, the pseudorandom sequence is stored in a receiver cache for reuse with each iterative use of the stored transmitter pseudorandom sequence.

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San Jose, CA, United States of America

Richard W Mincher