IP Verse

Cyclic diversity systems and methods

Patent No. US7623439 (titled "Cyclic diversity systems and methods") on May 4, 2005. The application was issued on Nov 24, 2009.

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Technical Landscape

In the mid-2000s when ’439 was filed, wireless communication systems were transitioning toward multi-antenna architectures at a time when signal transmission was typically implemented using single-input, single-output (SISO) configurations. During this era, systems commonly relied on linear delay diversity to improve signal robustness, but hardware and software constraints made it non-trivial to maintain backward compatibility with legacy receivers. Engineering practices were focused on managing multipath interference within Orthogonal Frequency Division Multiplexing (OFDM) frameworks, where the integration of multiple transmit antennas often introduced synchronization or decoding challenges for existing hardware designed for single-stream reception.

Prosecution Position

The disclosed invention addresses the technical problem of performance degradation and compatibility issues encountered when multi-antenna transmitters interact with legacy OFDM receivers. The architectural solution involves a logic configuration that applies a cyclic advance to specific sections of an OFDM packet for transmission on a secondary antenna, ensuring the duration of this advance remains less than the guard interval. This shift from linear delay to cyclic diversity achieves the technical effect of improving packet error rate performance while maintaining structural alignment with standard OFDM packet formats. By cyclically shifting training symbols or data segments in the time or frequency domain, the system enables enhanced diversity gain without exceeding the temporal constraints of the guard interval, thereby overcoming the limitations of conventional diversity mechanisms in mixed-device environments.

Claims

The patent contains 21 claims, with claims 1, 8, and 19 serving as the independent claims. These independent claims focus on a method and systems for transmitting orthogonal frequency division multiplexing (OFDM) signals by generating a first packet and a cyclically advanced version of that packet, where samples are shifted between the symbol data and guard interval portions, followed by the simultaneous transmission of both versions. The dependent claims serve to specify technical parameters such as shift durations and hardware implementations, including the use of specific processors, integrated circuits, and compliance with wireless standards, while also detailing the resulting impulse responses produced by receiver devices.

Key Claim Terms New

Definitions of key terms used in the patent claims.

Term (Source)Support for SpecificationInterpretation
Cyclically advancing
(Claim 1, Claim 8, Claim 19)		The cyclic diversity system comprises cyclic extension logic that provides cyclic advance diversity to one or more sections of OFDM packet structures. By providing cyclic advances, cyclic shift diversity is employed which enables legacy receivers to experience improved packet error rate performance. This involves cyclically advancing one or more sections of an OFDM packet relative to the packet to be transmitted on a first antenna.A process of shifting samples of an OFDM packet in a first direction such that a portion of the symbol data is moved into the guard interval and a corresponding portion of the guard interval is moved out, creating a cyclic shift diversity effect.
Guard interval portion
(Claim 1, Claim 8, Claim 19)		The system is configured to cyclically advance one or more sections of an OFDM packet where the duration of the cyclic advance has a duration less than a guard interval. The packet includes periodic structures such as long training symbols, short training symbols, and OFDM symbols. The guard interval is used to manage the impact of linear delay diversity on the symbol stream at the transmitter and receiver.A specific section of an OFDM packet comprised of a plurality of samples that serves as a temporal buffer, the duration of which defines the upper limit for the cyclic advance shift.
Shifted version
(Claim 1, Claim 8, Claim 19)		The system comprises logic configured to cyclically advance one or more sections of an OFDM packet relative to the OFDM packet to be transmitted on a first transmit antenna. The packet having the one or more cyclically advanced sections is to be transmitted on a second transmit antenna. This enables the use of multiple antennas in a single device while considering legacy receivers.A secondary version of the original OFDM packet generated by cyclically advancing samples, intended for substantially simultaneous transmission with the original packet on a different antenna.
Substantially simultaneously transmitting
(Claim 1, Claim 8, Claim 19)		The transmitter device is configured with cyclic extension logic that provides cyclic advance diversity to one or more sections of OFDM packet structures. The first transmit processor and the second transmit processor are configured to cause the transmission of the first OFDM packet and the shifted version via corresponding transmitters and antennas. This simultaneous transmission enables legacy receivers to experience improved performance compared to conventional diversity mechanisms.The concurrent transmission of the original OFDM packet and its cyclically shifted counterpart via different radio transmitters and antennas to achieve spatial diversity.
Symbol data portion
(Claim 1, Claim 8, Claim 19)		Cyclic diversity can be applied to one or more of the sections such as long training symbols, short training symbols, or OFDM symbols. These sections represent the periodic structures of a segment in the time domain or subcarrier structures in the frequency domain. The logic shifts samples from these portions to provide cyclic shift diversity.The part of the OFDM packet containing the primary information or training samples, from which a non-zero number of samples are shifted into the guard interval during the cyclic advance process.

Patent Summary

Litigation Cases New

US Latest litigation cases involving this patent.

Case NumberFiling DateTitle
1:25-cv-00834Jun 2, 2025Intellectual Ventures I Llc V. Lenovo Group Limited

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US7623439

Application Number
US11121661A
Filing Date
May 4, 2005
Publication Date
Nov 24, 2009
External Links
Slate, USPTO , Google Patents