Stanford Telecommunications, Inc.

Other

Northrop Grumman Systems Corporation

Trw Limited

Alcatel USA Sourcing, L.p.

Alcatel Canada Inc.

John E Ohlson

Francis D Natali

Donald R Martin

Timothy F Cox

Robert A Frosch

Bruce Joseph Currivan

Shilpa Talwar

Jing Shiang Cheng

William Slivkoff

Francis F Natali

Michael J Pender, Jr

Emmanuel M Wildauer

MacGregor S Reid

In a wireless communication system which includes a synchronization signal generator which generates a synchronization sequence, an RF transmitter which transmits the synchronization signal, and one or more receiver that receives the signal, where the synchronization sequence employs M PN codes of the same length that are repeated in a pseudo-random fashion for N code periods. Each receiver incorporates M filters matched to the M PN codes whose outputs are post detection combined in a manner consistent with the pseudo-random code transmission sequence to provide signal detection and synchronization. In another aspect, the synchronization sequence employs M time-shifted versions of a PN code that are repeated in a pseudo-random fashion for N code periods and each receiver incorporates a filter matched to the unshifted PN code and whose output samples are post detection combined in a manner consistent with the pseudo-random code transmission sequence to provide signal detection and synchronization.

Rapid acquisition synchronization sequences for direct sequence spread spectrum systems using code time offsets

Data packets are selected for simultaneous transmission to multiple users using a transmitter with limited transmission power by first establishing transmission power requirements for each user, receiving in a queue a plurality of data packets for transmission to one or more users, and selecting one or more data packets for transmission in a composite burst with cumulative power for the selective packets not exceeding the limited transmission power. Data packets are selected for sequential composite bursts until all data packets in the queue have been transmitted, at which time transmission ceases until more incoming packets arrive at the queue. In selecting data packets for transmission, data packets which have previously been delayed in transmission can be given priority as well as priority based on quality of service subscribed by each user. Additionally a predetermined priority weight can be assigned to data packets and used for selection.

Power pooling in network downstream data transmission

A communications waveform format is provided for a satellite-based telecommunications system. The waveform format includes forward and return link waveforms between the satellite, earth stations and terminals. The forward and return links use orthogonal direct-sequence code division multiple access (ODS-CDMA) to minimize interference between users. The forward and return link spectrum may be divided into channels, the frequencies and spacing of which are adjustable to compensate for Doppler effects, thereby maintaining synchronization. The spectrum of the terminal links may be divided into multiple subbands (e.g., 38), each of which may support multiple (e.g., 80) ODS-CDM channels. The forward and return links support traffic channels (TCH), associated signaling channels (ASC), broadcast control channels (BCC), forward signaling channels (FSC) having paging slots (PAS) and channel allocation slots (CAS), call establishment channels (CEC), and loop signaling channels (LSC), a measurement reporting channel (MRC), and a return access channel (RAC). The RAC carries nonsynchronous spread spectrum pseudo-noise (PN) signal access bursts which are used by terminals to initially access the communications system.

Orthogonal code division multiple access waveform format for use in satellite based cellular telecommunications

An ODS-CDMA communications system is disclosed with at least one hub station and a plurality of user terminals. Each user is assigned a code which is orthogonal to all of the other user codes. The orthogonal code period is chosen such that the code repeats an integer number of times in a data symbol time and the code is synchronized with the symbol transitions so that no data transitions occur within the code. Thus, the selection of an orthogonal code book which enables a high rate data to be spread using shorter code words, and conversely, low data rate to be spread using longer code words, all of which remain mutually orthogonal.

Apparatus for incorporating multiple data rates in an orthogonal direct sequence code division multiple access (ODS-CDMA) communications system

A communications waveform format is provided for a satellite-based telecommunications system. The waveform format includes forward and return link waveforms between the satellite, earth stations and terminals. The forward and return links use orthogonal direct-sequence code division multiple access (ODS-CDMA) to minimize interference between users. The forward and return link spectrum may be divided into channels, the frequencies and spacing of which are adjustable to compensate for Doppler effects, thereby maintaining synchronization. The spectrum of the terminal links may be divided into multiple subbands (e.g., 38), each of which may support multiple (e.g., 80) ODS-CDMA channels. The forward and return links support traffic channels (TCH), associated signaling channels (ASC), broadcast control channels (BCC), forward signaling channels (FSC) having paging slots (PAS) and channel allocation slots (CAS), call establishment channels (CEC), and loop signaling channels (LSC), a measurement reporting channel (MRC), and a return access channel (RAC). The RAC carries nonsynchronous spread spectrum pseudo-noise (PN) signal access bursts which are used by terminals to initially access the communications system.

A communications waveform format is provided for a satellite-based telecommunications system. The waveform format includes forward and return link waveforms between the satellite, earth stations and terminals. The forward and return links use orthogonal direct-sequence code division multiple access (ODS-CDMA) to minimize interference between users. The forward and return link spectrum may be divided into channels, the frequencies and spacing of which are adjustable to compensate for Doppler effects, thereby maintaining synchronization. The spectrum of the terminal links may be divided into multiple subbands (e.g., 38), each of which may support multiple (e.g., 80) ODS-CDMA channels. The forward and return links support traffic channels (TCH), associated signaling channels (ASC), broadcast control channels (BCC), forward signaling channels (FST) having paging slots (PAS) and channel allocation slots (CAS), call establishment channels (CEC), and loop signaling channels (LSC), a measurement reporting channel (MRC), and a return access channel (RAC). The RAC carries nonsynchronous spread spectrum pseudo-noise (PN) signal access bursts which are used by terminals to initially access the communications system.

The invention relates to a threshold extension block phase estimator (TEBPE) which estimates phase in the presence of noise. Threshold and sector slips are controlled by an iterative calculation. This can be of crucial advantage in coded systems. Another attribute of the TEBPE is it can be configured as a hybrid feedback loop incorporating characteristics of both the BPE and the PLL. This gives a high degree of flexibility with very fast acquisition times at high signal-to-noise ratio (SNR), and improved threshold performance at low SNR.

Threshold extension block phase estimator for quasi-coherent communications systems

A method and apparatus for taking advantage of diverse signals. Trellis decoding takes advantage of multiple symbol noncoherent detection and diversity combining. Accordingly, combination of diverse signals effectively occurs pre-detection. Tracking loops are not necessary to set weights for each channel. In a QPSK embodiment employing a rate 1/2 convolutional code, an improvement in effective SNR of 1-3 dB may be achieved as compared with non-diverse reception.

Trellis decoding with multiple symbol noncoherent detection and diversity combining

A spread spectrum OCDMA communication system in which multiple base stations or beams from a satellite are deployed in a &ldquo;cellular&rdquo; coverage structure, system capacity is increased by dividing the available spectrum into non-overlapping frequency segments which are assigned to different cells in a frequency reuse pattern to provide greater system capacity than full frequency reuse in each cell.

Increased capacity in an OCDMA system for frequency isolation

A spread spectrum CDMA communication system in which base stations communicate with a plurality of subscriber terminals located in different beams of a multi-beam satellite relay system. A base station transmits a signal for each beam which is comprised of a set of orthogonally spaced subcarriers, each of which is modulated by a set of orthogonal functions which are overlaid with a pseudo-noise (PN) sequence forming a coded spreading sequence for an information signal. Each orthogonal function carries data for a single user in the beam. Selected carrier signals are modulated with information signals onto the subcarriers to form a beam signal. The available frequency spectrum is divided into non-overlapping segments which are assigned to different beams in a 1:N.sub.ru frequency reuse pattern. Each subscriber terminal has a receiver which coherently demodulate the base station signal. A PN spreading code, P2, with chipping rate N.sub.ru .chi.R.sub.c is applied to all of the beam signals simultaneously to spread the signal energy over a wider bandwidth to reduce the power spectral density in each beam. The receiver correlates the received signal with a synchronized replica of P2 to remove P2 from the incoming signal without affecting beam-to-beam frequency isolation. The subcarriers of the beam signal are orthogonally spaced across the available frequency spectrum with spacing N.sub.ru .chi.R.sub.c and N.sub.ru distinct sets of subcarriers frequencies are formed to be assigned in the 1:N.sub.ru beam frequency reuse pattern.

Flux density reduction in OCDMA satellite communication system

A method of paging assigns a unique digital address to mobile stations with each unique digital address being mapped into an orthogonal signal set which is then transmitted to all mobile stations. Each mobile station then correlates a received orthogonal signal function against an orthogonal function corresponding to its address. More particularly, each orthogonal signal set comprises a binary orthogonal signal set such as a set of Rademacher-Walsh functions. Other well known orthogonal function sets can be employed. For example, an mbit address can be partitioned into g binary sequences and each sequence is then uniquely mapped into one of 2.sup.m/g orthogonal functions.

Power efficient paging for mobile users in a terrestrial and satellite

A method and an apparatus are provided for transmission of band limited QPSK data which is orthogonal direct-sequence spread using a BPSK sequence which preserves the band limiting even with subsequent amplification by non-linear amplifiers. This feature allows inexpensive implementation in mass produced, portable communications devices.

Modulation method and system using constant envelope ODSCDMA with low

A spread spectrum CDMA communication system in which a base station communicates with a plurality of subscriber terminals and the base signal transmitted by the base station is comprised of a set of substantially orthogonal functions which are overlaid with a pseudo-noise (PN) sequence forming a coded spreading sequence for an information signal, each orthogonal function of the set carries data for a single user in the system. Information signals are modulated onto the carrier to form a transmit signal and the coded spreading sequence on the transmit signal for broadcasting, each subscriber terminal having a receiver for coherently demodulating the base station signal. A plurality of correlators, each respectively tuned to different functions of the orthogonal signal set, are each followed by an appropriate nonlinearity for removing the data modulation. The summed output of the correlators is used to improve the estimate of carrier phase over that obtained with a single correlator.

Forward link carrier recovery in an OCDMA spread spectrum communication

A spread spectrum CDMA communication system in which a station transmits a short synchronization signal to allow a second station to (1) recognize that a signal is present, (2) resolve frequency uncertainty, (3) acquire the spreading code timing, (4) acquire frame and symbol synchronization, and (5) demodulate data which may contain user identification and other data. The rapid acquisition channel (RAC) includes a burst signal comprising of an Acquisition Field during which the carrier is biphase modulated with a pseudo-noise (PN) sequence, a Sync Field during which a synchronization sequence is mod-2 added to the PN sequence with one chip of the sync sequence equal to one or more periods of the PN sequence, and a data field with m-ary orthogonal code words mod-2 added to the PN sequence with one chip of the code word equal to one or more periods of the PN sequence.

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Mountain View, CA, United States of America

John E Ohlson