Obviousness

To assess the obviousness of US patent 8385284 under 35 U.S.C. § 103, we must consider whether the claimed invention, at the time of the invention (before the priority date of 2007-12-20), would have been obvious to a person having ordinary skill in the art (PHOSITA) by combining existing prior art references. A PHOSITA in this field would be an engineer or researcher involved in designing wireless communication systems, particularly the physical and MAC layer signaling for mobile standards like 3GPP LTE or HSDPA, with an understanding of HARQ protocols and resource allocation.

The core of US patent 8385284 lies in reducing control channel overhead by efficiently signaling transport format (TF) and redundancy version (RV), often by combining them into a single field.

Primary Prior Art Reference

The patent itself identifies the state of the art, particularly in 3GPP HSDPA systems. As stated in the patent's background: "As described in section 4.6 of 3GPP TS 25.212, “Multiplexing and Channel Coding (FDD”), version 7.6.0, September 2007 (available at http://www.3gpp.org) in HSDPA the “Transport Format” (TF) (Transport-block size information (6 bits)), the “Redundancy and constellation Version” (RV/CV) (2 bits) and the “New Data Indicator” (NDI) (1 bit) are signaled separately by in total 9 bits."

Reference: 3GPP TS 25.212, "Multiplexing and Channel Coding (FDD”), version 7.6.0, September 2007.

Disclosure by 3GPP TS 25.212: This document, which predates the priority date of US8385284, explicitly teaches a control channel signaling mechanism for HSDPA in a mobile communication system. It describes the use of separate fields for:

• Transport Format (TF): 6 bits.
• Redundancy and Constellation Version (RV/CV): 2 bits.
• New Data Indicator (NDI): 1 bit.
  These fields are part of the L1/L2 control signaling associated with a transport block (a type of protocol data unit) and are used to convey user data.

Obviousness Analysis of Claim 1

Claim 1: "A control channel signal for use in a mobile communication system, the control channel signal associated to a protocol data unit transporting user data and comprising a control information field consisting of a number of bits jointly encoding a transport format and a redundancy version used for transmitting the protocol data unit."

1. Elements Disclosed by Prior Art: 3GPP TS 25.212 discloses a control channel signal in a mobile communication system, associated with a protocol data unit (transport block), which includes explicit signaling for both transport format and redundancy version.

2. Missing Element: The key difference between Claim 1 and 3GPP TS 25.212 is the "jointly encoding a transport format and a redundancy version" within a single control information field. 3GPP TS 25.212 describes these as separate, distinct fields.

3. Motivation to Combine/Modify: A PHOSITA in 2007 would have been strongly motivated to reduce control channel overhead in wireless communication systems. The patent itself identifies this as a primary objective: "One object of the invention is to reduce the amount of bits required for control channel signaling, such as for example L1/L2 control signaling, in uplink or downlink." The separate signaling of TF (6 bits) and RV (2 bits) in HSDPA systems, totaling 8 bits for these two parameters alone, would have been an obvious target for optimization.

   Given the desire to reduce bits, a PHOSITA would have considered known engineering techniques for more efficient signaling of related parameters, such as:

   • Implicit Signaling: Leveraging the fact that some redundancy versions might be fixed or implicitly determined for certain transport formats (e.g., RV0 for initial transmissions, as mentioned in the patent description), thereby reducing the need for explicit signaling.
   • Joint Encoding/Coding: Combining multiple related parameters into a single field where a specific bit combination represents a unique pair (or tuple) of values for those parameters. This is a common method to achieve bit savings when the total number of possible combinations is less than what would be required by separate fields, or when some combinations are more frequently used.

   The decision to jointly encode TF and RV into a single field represents a design choice aimed at achieving the universally desired goal of signaling efficiency in a resource-constrained wireless environment. While it might involve a trade-off in flexibility or increased complexity in encoding/decoding logic, the motivation for a PHOSITA to attempt such a combination to reduce overhead would have been high and within the ordinary skill in the art. The patent presents this as a "new format for the control channel information", a structural modification to existing signaling to achieve a known desirable outcome (bit reduction).

Therefore, it would have been obvious to a PHOSITA, seeking to reduce control channel overhead in mobile communication systems, to combine the separately signaled Transport Format and Redundancy Version fields, as taught by 3GPP TS 25.212, into a single jointly encoded control information field.

Obviousness of Other Independent Claims

The same reasoning applies to the other independent claims, as they describe the method, apparatus (base station and mobile terminal), and computer-readable media for implementing or utilizing the control channel signal described in Claim 1:

• Claim 13 (Method for Encoding): If the signal structure of Claim 1 is obvious, the method for a base station to generate and transmit such a signal would also be obvious, driven by the same motivation to save signaling bits.
• Claim 24 (Method for Mobile Terminal): Similarly, if the signal is obvious, the corresponding method for a mobile terminal to receive and interpret this signal to determine TF and RV, and then to receive or transmit data accordingly, would be an obvious counterpart implementation.
• Claim 31 (Base Station Apparatus): The base station apparatus configured to generate and transmit such a jointly encoded control channel signal would be an obvious implementation of the method of Claim 13.
• Claims 33 & 34 (Mobile Terminal Apparatus): A mobile terminal apparatus configured to receive and determine TF and RV from such a jointly encoded control channel signal, and then to transmit (Claim 33) or receive (Claim 34) data, would be an obvious implementation of the method of Claim 24.
• Claims 35 & 36 (Computer Readable Medium): Computer-readable media storing instructions to perform these obvious methods at a base station or mobile terminal would also be obvious to a PHOSITA.

Considering Other Embodiments (e.g., Jointly Encoding NDI)

The patent also describes embodiments where a New Data Indicator (NDI) or sequence number (SN) is additionally jointly encoded with TF and RV within the single field, or where a "shared field" is used to signal either TF (for initial transmission) or RV (for retransmission) depending on the NDI.

The motivation for these variations remains the same: reducing signaling overhead. Since 3GPP TS 25.212 also discloses a separate 1-bit NDI field, a PHOSITA would have had the same motivation to jointly encode NDI with TF and RV, or to use a shared field approach, to further optimize control channel efficiency. These represent further design choices in the same direction of bit reduction, given the known parameters in prior art.

In summary, the specific prior art reference 3GPP TS 25.212, combined with the widely recognized motivation to reduce control channel signaling overhead in wireless communication systems, would render the claims of US patent 8385284 obvious to a person having ordinary skill in the art.