A data rate is selected for subcarriers of each frequency and spatial channel of a slowly varying frequency selective multicarrier channel to provide uniform bit loading (UBL) for faster link adaptation. Signal to noise ratios (SNRs) for subcarriers of the multicarrier communication channel may be calculated from channel state information and a transmit power level. A throughput may be estimated for the data rates from the SNRs and one of the data rates may be selected based on the estimated throughputs.

System and method for selecting data rates to provide uniform bit loading of subcarriers of a multicarrier communication channel

The class-AB/F power amplifier (PA), a multimode PA, which can operate at both class-AB and class-F modes, is analyzed and compared with the conventional class-F and class-AB PAs. The open-circuited third harmonic control circuit enhances the efficiency of the PA without deteriorating the linearity of class-AB mode of the PA. The voltage and current waveforms are simulated to evaluate the appropriate operation for the modes. To demonstrate the multimode PA, the PA is implemented using an InGaP/GaAs HBT process and it is tested with reverse-link IS-95A code division multiple access (CDMA) and PCS1900 global system for mobile communications signals in the personal communications service band. The class-AB operation for a CDMA signal delivers a power-added efficiency (PAE) of 38.9% and an adjacent channel power ratio of 49.5 and 56.5 dBc at the offset of 1.25 and 2.25 MHz, respectively, at the output power of 28 dBm. The maximum PAE of 64.7% under the class-F operation is measured at 32.5-dBm output power for a GSM signal. The class-AB/F PA is a good candidate for the multimode PA of next-generation wireless communication systems.

A Highly Efficient and Linear Class-AB/F Power Amplifier for Multimode Operation

A method for selecting transmission parameters of a multicarrier communication channel comprises setting a power level for active subcarriers of a multicarrier communication channel based on a number of the active subcarriers to achieve a highest channel capacity.

Multicarrier communication system and methods for link adaptation using uniform bit loading and subcarrier puncturing

A multicarrier transmitter includes a space-frequency interleaver and a space-frequency coder to encode multicarrier signals for transmission over a plurality of spatial channels.

Multicarrier transmitter, multicarrier receiver, and methods for communicating multiple spatial signal streams

A frame format provides for wideband wireless local area network communications and informs narrower-band communication units when the channels are occupied by wider-band communication units. In some embodiments, the frame format includes a channelization field identifying channels that are used for communicating subsequent wideband fields of a packet, and a wideband-header field communicated on the identified channels. The wideband-header field may identify sub-fields that may be present in the wideband-header field, and may identify the presence of a wideband-data field. A long-compatibility field may be present that provides protection at the MAC level. The long-compatibility field may transport MAC frames that may include medium-reservation information compatible with narrower-band communication units.

Systems and methods for high-throughput wideband wireless local area network communications

With the explosive growth of the mobile communication and the expansion of Internet services, Mobile multimedia services, e.g. more than 2Mb/s, are expected for future mobile communication systems. As 3G is still not sufficient to support future mobile communication strategy and according to the historical indication of a generation revolution once a decade, it is high time to discuss the development of the future generation mobile communication systems. After illuminating the impetus force to driven the 4G research, this paper studies the vision and framework of 4G, describes the adaptability features of terminals, networks and applications in 4G system and proposes some technologies in the design of future mobile communication systems.

Consideration and research issues for the future generation of mobile communication

In multiuser OFDM systems, because the subcarriers of each user undergo independent channel fading, then each subcarrier can be allocated to the most appropriate user to maximally improve the system capacity. In this paper, we study the optimal subcarrier and power allocation algorithm for wideband OFDM systems. To minimize total transmit power with constraints on BER and each user's rate requirement, in the two steps joint allocation method, we proposed an improved rate craving greedy multiuser dynamic subcarrier allocation algorithm. Analysis and simulation results show that our algorithm offers comparable complexity and better performance than original method.

Improved algorithm of multiuser dynamic subcarrier allocation in 0FDM system

OFDM and adaptive transmission are two most promising technique for next generation high data rate mobile communication systems. In this paper, we combine the two techniques and propose a simple and computational efficient adaptive bit and power allocation algorithm for broadband OFDM system. In the algorithm, first the bit and corresponding power are allocated to each sub-carrier according to channel condition, water filling theory and QoS requirement of the user, then the residual power is allocated to the sub-carriers which can use them most efficiently. In this way, this algorithm is efficient while calculation is less complex. Simulation results show the advantages of the proposed algorithm over those of equal bit loading algorithm and original SNR based adaptive allocation method.

https://ieeexplore.ieee.org/iel5/8688/27522/01226210.pdf

A modified sub-optimum adaptive bit and power allocation algorithm in wideband OFDM system

MIMO/OFDM is one of the promising technologies to improve the spectral efficiency, enhance system capacity and mitigate intersymbol interference in the fourth generation broadband mobile communication system. In this paper, we aim at the study of a communication system that employs both MIMO-OFDM and adaptive modulation/coding technologies. In this article, the performance of different modulation schemes including fixed modulation/coding and adaptive modulation/coding is analyzed and compared by simulation. We also propose an adaptive modulation/coding algorithm for multiuser MIMO-OFDM system. This adaptive allocation algorithm assigns the subcarriers and bits for users in the system with the minimum total transmission power and targeted bit error rate (BER) based on the time-variant MIMO channel condition. Computer simulation results demonstrate that the proposed algorithm is not only simple but can also have a relative low transmission power compared with the fix BPSK, QPSK and 16QAM modulation schemes.

Performance study of adaptive modulation/coding in MIMO-OFDM system

In OFDM systems, because channel fading on different sub-channels is different; when all OFDM sub-carriers use the same fixed modulation scheme, the error probability is dominated by the sub-carriers with the highest attenuation. Link adaptation can be used to enhance system throughput. According to the current link quality, the most appropriate modulation scheme can be selected on each sub-carrier to maintain acceptable error rate performance. In this paper, two link adaptation methods are considered. In the first method, a fixed number of weak sub-carriers which are highly attenuated are left out to improve the BER performance; in the second method, depending on the channel quality of each sub-carrier the modulation level on each sub-carrier is varied to adapt to the link conditions to improve the system throughput. The analysis and simulation results verify that the proposed link adaptation and coding scheme is effective in improving system throughput compared with the system with fixed modulation/coding.

Link adaptation of wideband OFDM systems in multi-path fading channel

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