High peak-to-average power ratio (PAPR) has long posed a challenge for multi-carrier systems, impacting amplifier efficiency and overall system performance. This paper introduces dynamic angle fractional Fourier division multiplexing (DA-FrFDM), an innovative transmission framework that significantly reduces PAPR by dynamically selecting an optimal transform angle in the fractional Fourier domain. By exploiting the dual nature of PAPR across time and frequency domains, DA-FrFDM adaptively maps signals from an intermediate domain to time domain that minimizes peak fluctuations while preserving average power. A tailored optimization algorithm is developed to efficiently determine the angle that minimizes PAPR for each signal block. Simulation results demonstrate that DA-FrFDM outperforms state-of-the-art PAPR mitigation techniques such as clipping, selective mapping, and partial transmitted sequence, achieving superior PAPR reduction for both Gaussian and QAM signals. These findings highlight DA-FrFDM as a promising solution for enhancing power efficiency in future multi-carrier systems.

Small cell networks are considered one of the key technologies in the next generation wireless networks. One of the main challenges in this area of research is how to tackle the problems of interference and resource allocation, especially for the hyper dense deployment of small cells. In this paper, we study the problem of cooperative interference mitigation in a small cell network. In particular, we develop a novel algorithm for encouraging small cell base stations to cooperate with their neighbors. Considering coalitional structure, small cells can mitigate the co-tier interference within a coalition and thus increase the system capacity. A cooperative approach among the adjacent small cells is formulated as a coalitional structure generation with characteristic forms. Meanwhile, during the coalition being formed, the associated frequency resources are also assigned. In contrast to the previous small cells' cooperative algorithms, a new feature for the proposed algorithm requires the computation for pairs of players. The proposed algorithm will raise the efficiency and is particularly applicable to the mass small cells' deployment scenario.

We point out a flaw involved in the proof of Lemma 2 in the above-cited paper (IEEE/ACM Trans. Netw., vol. 17, no. 6, pp. 1846-1859, Dec. 2009) and provide a corrected version.

Equipping multi-channel in wireless networks brings not only an improved capacity region but also high challenge in designing joint channel-assignment and scheduling algorithms. With regard to the distributed and online strategies under multi- channel network systems, the implementation complexity is non-negligible and much higher than that of the single-channel cases. In this paper, we propose a low-complexity throughput guaranteed distributed policy, i.e., LDCSA, in multi- channel Ad hoc wireless networks, which has the property of low complexity, i.e., the computation time of the algorithm is low and increases neither with the size of network nor with the number of available channels. It is proved that the capacity region achieved by LDCSA can be arbitrarily close to that of other comparable maximal matching-based scheduling algorithms.

The authors propose two soft forwarding schemes for unitary space‐time modulation, namely estimate‐and‐forward (EF) and mutual information‐based forwarding (MIF), which are ideally suited for rapid piecewise‐constant fading scenarios with no channel state information both at transmitters and receivers. In the EF scheme, the relay regenerates signal via the conditional expectation of the source unitary space‐time (UST) signal given the received matrix at the relay node instead of hard decisions. The MIF scheme employs the instantaneous mutual information between the source UST signal and received matrix at the relay node as a measurement for maximum‐likelihood detection. The authors provide the relay forwarding functions, the normalisation factors, and the detection methods at the destination firstly. Above all, the generalised signal‐to‐noise ratio (SNR) at the destination for our unitary space‐time modulated relaying system is analysed and simulated firstly. Simulation results reveal that the proposed EF and MIF schemes can outperform the existing amplify‐and‐forward (AF) and detect‐and‐forward (DF) schemes in terms of bit‐error‐rate performances in most scenarios. For a parallel relay network with two relays, the proposed EF scheme achieves 2 and 3 dB SNR gain over AF and DF schemes, respectively. Moreover, the MIF scheme can further give about 1.5 dB SNR gain.

This paper proposes a dynamic bound restriction iterative algorithm (DBRIA) framework, which can make iterative algorithms converge quickly. We apply this framework to realize computationally efficient iteration-based suboptimal bit and power allocation in OFDM systems. The implementation methods for three classes of suboptimal allocation algorithms are analyzed; margin-based, water-filling-based, and Lagrange-multiplier-based. We extend the water-filling-based power allocation algorithm to implement the bit allocation as well. Additional techniques for further reducing the computational complexity for all three allocation methods are also discussed. Simulation results show that both the maximum and the average computational complexity of all three allocation algorithms are reduced dramatically by applying the DBRIA and the additional techniques. For the water-filling-based algorithm, the allocation performance is also improved.

We point out that the model in (3) of [1] is not accurate enough to characterize the energy captured by realistic ultra-wideband (UWB) receivers and hence the average bit error rate (ABER) evaluated by using the framework in [1] can be remarkably far from the actual ABER of realistic UWB receivers. We also show that good performance can be achieved by using the framework in [1] if models tailored for realistic receivers are employed instead of the original model in (3) of [1].

This paper proposes a new optimal bit and power direct allocation algorithm. Based on the analysis of the regularity of the Greedy allocation result, we propose and prove a necessary and sufficient condition for the Greedy allocation result. According to this condition, a bit and power allocation algorithm aiming to allocate the total bits or total power at a time to all subchannels is proposed. The impact of SNR Gap on the allocation result and the technique to eliminate its impact are analyzed. Though iterations are needed to obtain the ideal allocation result, the computational complexity is lower than that of existing optimal algorithms in the literature, even lower than that of some suboptimal algorithms.

In this note, two typos in above-mentioned paper are pointed out and a sufficient condition to ensure the PER requirement in the optimization problem is provided.

In this paper, we proposed a new multicarrier, direct sequence code division multiple access, the so-called premulticoded MC-DS-CDMA system. In this scheme, the basic MC-DS-CDMA system is augmented with a precoder and a multicode encoder at the transmitter. The multicode encoder is an inverse Walsh-Hadamard transform (IWHT) unit, while the precoder is a recently suggested ldquoconstant amplituderdquo encoder that guarantees that the IWHT output stream has binary level. While IWHT, multicarrier (MC) transmission, and direct sequence spreading provide us with frequency diversity, the constant amplitude precoder ensures that the transmitted waveform is spread BPSK signal, minimizing peak to average-power ratio (PAPR) problem. The multicode and (MC) combination also addresses the need for flexible high data rate services in present day wireless communications. In the receiver, after matched filtering or correlation demodulation for each subcarrier and WHT operation, a detection strategy based on minimum-mean-square-error (MMSE) criterion is used. We have derived an upper bound for the bit error rate (BER) performance in Nakagami fading channel. Numerical results are compared with those obtained from a single carrier DS-CDMA system (SC-DS-CDMA) and a MC-DS-CDMA scheme without the precoding and IWHT units. We show that our proposed MC-DS-CDMA scheme has a much better BER performance compared with both of these schemes.

A new multi-carrier, direct sequence code division multiple access (MC-DS-CDMA) system with multi-code is proposed. Transmitted data are first serial-to-parallel converted to D parallel data streams and a pre-coding with a rate of D/M is followed. Next, these pre-coded parallel streams are multiplexed by an inverse Walsh-Hadamard transform (IWHT) (M/spl times/M) and M super-bit streams are formed. Due to using the pre-coding, the super-bit streams will be two-level symbol streams. Then, the super-bits are once more serial-to-parallel converted to form M parallel super-bit sub-streams. Finally, all the M parallel super-bit streams are direct sequence spread spectrum (DS-SS) modulated and transmitted using M orthogonal carriers. In the receiver, after demodulation and WHT operation, the strategy of minimum mean square error (MMSE) is used for detection. Based on a correlator receiver for each carrier, its upper bound of bit error rate (BER) performance over Nakagami fading channel is analyzed. Numerical results are compared with those of a single carrier DS-CDMA system (SC-DS-CDMA). It is shown that the proposed MC-DS-CDMA scheme has much better BER performance compared to the SC-DS-CDMA system.