In this paper, we introduce new full-diversity spacefrequency block codes (SFBCs) based on orthogonal space-time block codes (OSTBCs). We show that the proposed schemes are capable of attaining full-diversity and rate-one characteristics for two transmit antennas, although the proof of full-diversity property is limited to the real constellations. Also for the QPSK constellation, we present evidences through simulations that demonstrate the full-diversity property of the proposed SFBCs. The proposed SFBCs also benefit from the maximum coding advantage when partial channel state information is available at the transmitter. Simulation results confirm the performance superiority of the proposed codes over other recently proposed SFBCs under the same complexity at the receiver side.Index Terms-Wireless communication, space-frequency coding, frequency-selective fading channels, multiple-input multipleoutput orthogonal frequency-division multiplexing (MIMO-OFDM) systems.

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This paper investigates fairness among all small‐cell users (SCUs) in terms of energy efficiency for the uplink transmission of interference‐limited orthogonal frequency‐division multiple access–based heterogeneous networks. Each SCU is treated by a minimum data rate. In addition, a maximum tolerable interference for the macro base station has been considered. The resulting resource allocation problem is formulated as a nonconvex mixed‐integer nonlinear problem. In order to solve the mixed‐integer nonlinear problem, the subchannel assignment and the power allocation are applied separately; an efficient subchannel assignment algorithm has been proposed where the co‐tier and cross‐tier interference in the most general form has been taken into account. Then, to solve the power allocation subproblem, an iterative algorithm has been proposed by applying generalized fractional programming and sequential convex programming when a specified subchannel assignment is in hand. Performance of the proposed model has been evaluated, and simulation results indicate a fair resource allocation with a very high energy efficiency among SCUs comparing the state‐of‐the‐art solutions.

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