Arraycomm, Inc.

Intel Corporation

Trw Limited

Northrop Grumman Systems Corporation

Mithat Can Dogan

Mitchell D Trott

Stephen Deane Stearns

Marc H Goldburg

Branislav N Meandzija

Christopher Richard Uhlik

Paul Petrus

Sundar G Sankaran

The present invention efficiently stores a training sequence in a communications system, where the training sequence exhibits certain desirable characteristics when used by a peak to average power constrained modulation format. In one embodiment, the invention includes selecting a set of one or more original ordered sequences such that the set of ordered sequences has at least one desired property, creating a set of extended sequences, each based on an original ordered sequence by beginning with an element of an original sequence, cyclically appending elements of the original sequence in order to obtain a desired extended sequence length, and modifying each extended sequence using a corresponding modifying sequence, such that a training sequence can be generated from any one of the modified extended sequences by beginning with any one element of any one modified extended sequence and taking each element of the any one sequence in order to obtain the training sequence, the modifying sequence being selected so that the obtained training sequence when modulated by a selected modulation format has the at least one desired property of the corresponding original ordered sequence.

Method and apparatus for efficient storage of training sequences for peak to average power constrained modulation formats

Embodiments of the present invention can be used to generate a family of core training sequences having desired cross-correlation and out-of-phase auto-correlation properties for a communications system. The family can be generated by selecting seed sequences, so that the worst-case cross-correlation of the seed sequences is below a first initial threshold and the worst-case out-of-phase auto-correlation of the seed sequences is below a second initial threshold. Then, sequence families can be generated by inserting additional symbols into a corresponding seed sequence. Then, reduced sequence families can be generated by eliminating those sequences from the sequence families that have a worst-case out-of-phase auto-correlation above a third threshold. A sequence is selected from each reduced sequence family, so that the worst-case cross-correlation of the selected sequences is below a fourth threshold.

Generating training sequences in a communications system

In one embodiment, the present invention includes a slot in a repeating time division frame with a first training sequence, an information sequence after the first training sequence, and a second training sequence after the information sequence. In some embodiments either the first or the second training sequences indicates a type for the information sequence, such as a random access channel message and a traffic channel message, a configuration message, a channel assignment message, or a data traffic message.

Slot structure for radio communications system

A user terminal can be authenticated by an access point based on one message. In one embodiment, the present invention includes the access point receiving a message containing a shared secret encrypted with an access point public key, a user terminal certificate, and an authenticator string demonstrating possession by the user terminal of a user terminal private key. The access point can decrypt the shared secret using the private key of the access point paired with its private key. The access point can then authenticate the user terminal by checking the authenticator string using a user terminal public key included in the user terminal certificate to verify possession of the user terminal private key by the user terminal.

Terminal authentication in a wireless network

Some embodiments store a training sequence in a communications system. The stored training sequence exhibits certain desirable characteristics when used by a peak to average power constrained modulation format. In one embodiment, a set of original ordered sequences is selected to have at least one desired property. A set of extended sequences is created from the original sequences by beginning with an element of an original sequence and cyclically appending elements of the original sequence in order to obtain a desired extended sequence length. Each extended sequence is modified using a corresponding modifying sequence, such that a training sequence can be generated from any one of the modified extended sequences. Each modifying sequence is selected so that the generated training sequence when modulated by a selected modulation format has the at least one desired property of the corresponding original ordered sequence.

The certificate revocation lists at access points of a wireless access network can be reduced. In one embodiment, an Internet Service Provider ('ISP') connected to the wireless access network can receive a subscription request from a user terminal capable of accessing the ISP using the wireless access network. When the ISP assigns a subscription identifier to the user terminal, it also provides a service certificate signed by a certificate authority including the subscription identifier. In addition, the ISP also provides the user terminal one or more session certificates to be used to access the wireless access network, where the session certificates having a shorter validity period than the service certificate.

Reducing certificate revocation lists at access points in a wireless access network

Embodiments of the present invention can be used to select a training sequence used by a base station and a user terminal for communications. In one embodiment, selecting the training sequence to use includes first selecting a training sequence from a set of training sequences. Then, a shift indicator is received, the shift indicator indicating a number of symbols the training sequence is to be shifted. A shifted training sequence is generated by shifting the selected training sequence by the number indicated by the received shift indicator, and the shifted training sequence is used for communication with a first transceiver on a communications channel. In another embodiment, a shift indicator indicating a number of symbols a training sequence is to be shifted is first selected, and then used to generate a shifted training sequence by shifting the training sequence by the number of symbols indicated by the selected shift indicator. The shifted training sequence is then used for communicating with a transceiver on a communications channel.

Shifted training sequences in a communications system

The certificate issued by a certificate authority used in authenticating a user terminal can be scrambled prior to being set to an access point. In one embodiment, the present invention includes a user terminal having a memory in which a user terminal certificate is stored. The user terminal also has a processor coupled to the memory to scramble the user terminal certificate using a shared secret to be known only by the user terminal and an access point of the wireless access network, and a transmitter coupled to the processor to send a message to the access point, the message including the scrambled user terminal certificate.

Terminal identity masking in a wireless network

The time reference of a user terminal that is derived from an unauthenticated access point can be certified by a trusted entity according to the present invention. In one embodiment, the present invention includes a user terminal obtaining a time reference from an access point of a wireless access network. The user terminal then receives a digital certificate having a validity period from the access point, the certificate being issued by a certificate authority. In one embodiment, the user terminal requests certification of the time reference by a trusted entity, and receives the certification. Then the user terminal can validate the digital certificate.

Time certification in a wireless communications network

A system and method for communicating information between two locations via a wireless microwave link is provided. The system includes at least two antennas, each to transmit information as a narrow beam signal to be directed toward a focal point at a remote location. The antennas include at least one antenna to transmit a narrow beam signal toward a redirection point different from the focal point. A redirection device is located at the redirection point to receive the narrow beam signal from the at least one antenna element and to redirect the received narrow beam signal toward the receiver. The redirection point is located such that the narrow beam signals from the at least two antenna elements converge and overlap to form proximate to the receiver, an interference pattern that includes peaks and nulls having a peak-to-peak spacing narrower than the width of each received narrow beam signal.

Antenna array for point-to-point microwave radio system

A method and apparatus are provided that generate, transmit, or receive a training sequence in a communications system, where the training sequence exhibits certain desirable characteristics when used by a peak to average power constrained modulation formal. In one embodiment, the invention includes selecting an original training sequence from a set of possible original training sequences having at least one desired property, forming a modified training sequence by modifying the original training sequence based on a corresponding modifying sequence, such that the modified training sequence exhibits the desired property of the original training sequence when used in a peak to average power constrained modulation format that would otherwise impair the desired property of the original training sequence.

Training sequences for peak to average power constrained modulation formats

A method and apparatus are provided that allows a delay to be chosen to be applied to a user terminal. According to one aspect of the present invention, the invention includes receiving a downlink broadcast burst from a base station, determining timing for an uplink burst from the received broadcast burst, selecting an amount of delay for the uplink burst, and transmitting an uplink burst to the base station using the determined timing and the selected amount of delay.

Training sequence with a random delay for a radio communications system

A method and apparatus are provided that allows a coarse timing approximation to be determined from analyzing only a portion of a received burst. The coarse timing can be refined by focusing on the coarse timing approximation. According to one aspect of the present invention, the invention includes receiving a burst having a known repeating core training sequence, selecting an analysis window to be substantially the same size as a multiple of a single repetition of the core training sequence, and over sampling the received burst for the portion overlapping the analysis window. The invention further includes calculating a cross correlation vector for a portion of the samples with respect to a selected part of the training sequence, each cross correlation vector corresponding to a relative timing hypothesis and each cross correlation vector combining samples that occur at intervals within the analysis window, the intervals corresponding to the period of the repeating core training sequence, calculating a least squares fit for each hypothesis using the calculated cross correlation vectors; and selecting the combination of samples corresponding to the minimal least squares fit as the relative timing of the selected part of the repeating core training sequence.

Relative timing acquisition for a radio communications system

A method and apparatus are provided that allows timing to be determined in two steps. According to one aspect of the present invention, the invention includes searching a received digital signal burst for a known repeating core sequence, the core sequence having a first symbol sequence, and, upon finding one of the core sequences, determining sequence timing of the found core sequence using the found core sequence. The invention further includes searching the received burst for a marker sequence following the repetition of the core sequence, the marker sequence having a second symbol sequence different from the first symbol sequence and upon finding the marker sequence, determining timing of the received digital signal burst using the found marker sequence.

Relative and absolute timing acquisition for a radio communications system

A training sequence for a radio communications system is provided. According to one aspect of the present invention, the invention includes a core sequence of symbols, a successive repetition of the core sequence, and a marker sequence having a sequence of symbols different from the core sequence.

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Sunnyvale, CA, United States of America

Mithat Can Dogan