This paper proposes an enhancement to a previously reported adaptive peak-to-average power ratio (PAPR) reduction method based on clipping and filtering (CF) for eigenmode multiple-input multiple-output (MIMO) — orthogonal frequency division multiplexing (OFDM) signals. We enhance the method to accommodate the case with adaptive modulation and channel coding (AMC). Since the PAPR reduction process degrades the signal-to-interference and noise power ratio (SINR), the AMC should take into account this degradation before PAPR reduction to select accurately the modulation scheme and coding rate (MCS) for each spatial stream. We use the lookup table-based prediction of SINR after PAPR reduction, in which the interference caused by the PAPR reduction is obtained as a function of the stream index, frequency block index, clipping threshold for PAPR reduction, and input backoff (IBO) of the power amplifier. Simulation results show that the proposed PAPR reduction method increases the average throughput compared to the conventional CF method for a given adjacent channel leakage power ratio (ACLR) when we assume practical AMC.

In the Evolved UTRA (UMTS Terrestrial Radio Access) downlink, Orthogonal Frequency Division Multiplexing (OFDM) based radio access was adopted because of its inherent immunity to multipath interference and flexible accommodation of different spectrum arrangements. This paper presents the optimum adaptive modulation and channel coding (AMC) scheme when resource blocks (RBs) is simultaneously assigned to the same user when frequency and time domain channel-dependent scheduling is assumed in the downlink OFDMA radio access with single-antenna transmission. We start by presenting selection methods for the modulation and coding scheme (MCS) employing mutual information both for RB-common and RB-dependent modulation schemes. Simulation results show that, irrespective of the application of power adaptation to RB-dependent modulation, the improvement in the achievable throughput of the RB-dependent modulation scheme compared to that for the RB-common modulation scheme is slight, i.e., 4 to 5%. In addition, the number of required control signaling bits in the RB-dependent modulation scheme becomes greater than that for the RB-common modulation scheme. Therefore, we conclude that the RB-common modulation and channel coding rate scheme is preferred, when multiple RBs of the same coded stream are assigned to one user in the case of single-antenna transmission.

This paper presents laboratory experimental results on the throughput performance when key techniques such as adaptive modulation and channel coding (AMC) and hybrid automatic repeat request (ARQ) with packet combining are employed by an implemented transceiver based on the High-Speed Downlink Packet Access (HSDPA) air interface in a multipath fading channel. In AMC operation, we applied four modulation and coding schemes (MCSs): MCS1 (QPSK data modulation with the channel coding rate of R = 1/2, hereafter simply referred to as QPSK with R = 1/2), MCS2 (QPSK with R = 3/4), MCS3 (16 QAM with R = 1/2), and MCS4 (16 QAM with R = 3/4). The results elucidate that a peak average throughput above 5.0 Mbps is achieved at the average received signal energy per chip-to-background noise power spectrum density ratio (Ec/N0) of more than approximately 20 dB in a one-path fading channel; nevertheless, the achievable peak throughput becomes approximately 2.9 (2.6) Mbps due to severe multipath interference (MPI) in a two-path fading channel where the average signal power of the second path is 6 (3) dB lower than that of the first path, assuming nine-code-channel multiplexing with the fading maximum Doppler frequency of fD = 5 Hz. Furthermore, we clarify that although the throughput performance employing Type-II hybrid ARQ (i.e., Incremental redundancy) is almost the same as that employing Type-I hybrid ARQ with packet combining (i.e., Chase combining) in a two-path fading channel, Incremental redundancy exhibits superiority over Chase combing in a one-path fading channel for a high Doppler frequency channel such as fD = 80 Hz.

This paper proposes an adaptive radio parameter control scheme that utilizes an optimum radio parameter set comprising the maximum number of retransmissions in hybrid automatic repeat request (HARQ) in addition to the data modulation and channel coding scheme (MCS) according to the Quality of Service (QoS) requirements (i.e., the required packet error rate and delay) and propagation conditions such as the delay spread in the forward link of Orthogonal Frequency and Code Division Multiplexing (OFCDM) broadband wireless access. We elucidate by simulation evaluation that most of the optimum MCSs are common regardless of the delay requirement of traffic data, i.e., common between non-real time (NRT) and real-time (RT) class data. Concretely, the three MCSs of QPSK with the coding rate of R=1/2, 16QAM with R=1/2 and 3/4 are optimum ones, although the additional MCS of QPSK with R=1/3 is effective only for the RT class data in the lower received average received signal energy per symbol-to-background noise power density ratio (Es/N0) region. Furthermore, application of a much higher MCS set, 16QAM with R=5/6 and 64QAM with R=3/4, in addition to the three common MCSs improves the throughput under much higher Es/N0 conditions in a small delay spread environment. The simulation results show that the delay requirement, i.e., the maximum number of retransmissions, in HARQ does not affect the key radio parameter such as MCS, because of informative results such as a smaller number of retransmissions associated with a less-efficient MCS achieves a higher throughput than does using a more highly-efficient MCS allowing a larger number of retransmissions. Consequently, it is concluded that the proposed adaptive radio parameter control according to the QoS requirements substantially results in the selection of the optimum MCS irrespective of the delay requirement except for the extreme case where no retransmissions are allowed and for special propagation channel conditions.