Obviousness

Under 35 U.S.C. § 103, an invention is considered obvious if the differences between the claimed invention and the prior art are such that the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art (PHOSITA). For an obviousness rejection, there must be a motivation to combine the prior art references, and a reasonable expectation of success.

Based on the "BACKGROUND OF THE INVENTION" section of US patent 9001774, the following prior art and problem statement are identified:

Identified Prior Art:

1. U.S. patent application Ser. No. 11/327,799, filed on Jan. 6, 2006 (referred to hereafter as P1). This reference is explicitly incorporated by reference into US9001774. P1 discloses a technique for artificially introducing frequency diversity into an Orthogonal Frequency Division Multiplexing (OFDM) environment. Specifically, in the device disclosed in P1, "multiple copies of the same OFDM symbol are delayed by different delay values, then amplified by the same or different gain values, and then transmitted from different antennas." This process "artificially introduces frequency-selective fading in the OFDM channel, thereby allowing frequency selectivity to be exploited".

Problem Identified by US9001774 (as stated in its background):

The US9001774 patent identifies a need to improve upon the technique of P1. It states: "However, when selecting the symbol processing parameters (i.e., delay values and the gain values) applied to the OFDM symbols, it is important to take into consideration the user channel type and the mobile speed. To accomplish this, channel estimation is performed and the symbol processing parameters are determined based on the channel estimates and mobile speed. Therefore, there is a need for improved apparatuses and methods for performing channel estimation in an OFDM wireless network that artificially introduces frequency diversity by delaying and amplifying multiple copies of the same OFDM symbol and then transmitting the delayed and amplified OFDM symbols from different transmit antennas."

Analysis of Obviousness:

The claims of US9001774 address the problem stated in its background. For example, Claim 1 and Claim 6 are representative:

• Claim 1 of US9001774: "A method, comprising: receiving an uplink signal; determining a processing parameter for transmission of data on two antenna ports, the processing parameter including at least one of a time delay, a phase rotation and a gain based on the received uplink signal; transmitting a first pilot and a second pilot; and transmitting a first data symbol and a second data symbol on two antenna ports, at least one of the first data symbol and the second data symbol being processed based on the processing parameter."

• Claim 6 of US9001774: "A method, comprising: receiving a processing parameter for transmission of data on two antenna ports, the processing parameter including at least one of a time delay, a phase rotation and a gain determined based on a received uplink signal; receiving a first pilot, a second pilot, a first data symbol and a second data symbol transmitted on the two antenna ports; and demodulating the first data symbol and the second data symbol based on the processing parameter, the first pilot and the second pilot."

Combinations of Prior Art References and Motivation for Combination:

A PHOSITA would have been motivated to combine U.S. patent application Ser. No. 11/327,799 (P1) with the general knowledge in the art regarding channel estimation and adaptive transmission in wireless communication systems.

1. Teachings of P1: P1 clearly teaches the core concept of transmitting data symbols from multiple antennas with applied delays and gains to achieve artificial frequency diversity. This directly addresses the elements of transmitting processed data symbols with delays and gains from two antenna ports, as recited in Claims 1 and 6.

2. General Knowledge in the Art (Channel Estimation and Adaptive Transmission): At the priority date of US9001774 (April 21, 2005), it was a well-established practice in wireless communication systems, especially OFDM/OFDMA networks, to:

   • Transmit pilot signals (also known as training sequences or reference signals) from base stations to allow subscriber stations to estimate the wireless channel characteristics. The US9001774 patent itself lists "pilot" as a prior art keyword.
   • Perform channel estimation based on received signals (including pilot signals or uplink signals).
   • Use channel estimates to adapt various transmission parameters (e.g., modulation, coding rate, power, spatial processing parameters) to optimize system performance (e.g., throughput, reliability, spectral efficiency). This concept is broadly known as adaptive transmission or link adaptation.
   • Utilize feedback mechanisms, where a subscriber station estimates channel conditions and reports channel state information (CSI) or recommended transmission parameters back to the base station via an uplink signal. Alternatively, in TDD systems, channel reciprocity could be used, where the base station estimates the downlink channel from an uplink signal.

3. Motivation for Combination: The motivation for combining these elements is explicitly stated in the "BACKGROUND OF THE INVENTION" section of US9001774 itself. The patent identifies the problem that P1's delay diversity scheme, while introducing artificial frequency diversity, lacks a mechanism for optimally selecting the "delay values and the gain values" based on dynamic channel conditions, such as "user channel type and the mobile speed". The patent then explicitly states that "To accomplish this, channel estimation is performed and the symbol processing parameters are determined based on the channel estimates and mobile speed."

Therefore, a PHOSITA, aware of P1's delay diversity technique and the inherent challenge of optimizing its parameters, would have been directly motivated to apply conventional channel estimation and adaptive transmission principles. It would have been obvious to:

• Use standard pilot signals (transmitted as in Claim 1 or received as in Claim 6) to perform channel estimation.
• Determine the "processing parameter" (gains and delays, as described in P1, or their frequency-domain equivalent, phase rotation, as acknowledged in the patent's detailed description) based on these channel estimates.
• Either feed these determined parameters back to the base station via an uplink signal (as inferred from Claim 1, "receiving an uplink signal") or have the base station determine them from an uplink signal, for use in processing downlink data transmissions.
• Demodulate data symbols at the receiver using the knowledge of these parameters and the pilot signals (as in Claim 6).

The combination would yield a predictable improvement by making the delay diversity scheme adaptive and more efficient under varying channel conditions, directly addressing the "need" identified by the patent itself. The inclusion of "phase rotation" as a parameter would also be obvious, as the patent explains that a time delay in the time domain translates to a phase rotation in the frequency domain, a fundamental concept in OFDM systems.