For meteor burst communications (MBC), although per-survivor processing (PSP) based on joint data and channel estimation provides superior performance and robustness for meteor burst communications (MBC), great computational complexity constrains its application in practice. On this occasion, a dimension-down PSP (D- PSP) algorithm and a adaptive state reduction of PSP (ASRP) algorithm are proposed to curve this problem in this paper. On the basis of this, the adaptive state reduction using a dimension-down PSP (ADPSP) is proposed to combine the advantages of D-PSP and ASRP, which reduces the computational time and memory size for exponentially decaying meteor burst channels and makes maximum likelihood sequence detection (MLSD) possible for adaptive data transmission. Simulation results are presented to validate the theoretical analysis. It is shown that deploying the proposed ADPSP algorithm can achieve a good tradeoff between performance and computational complexity dynamically, and provide reliable data transmission for MBC systems with adaptive coding and modulation.

High complexity of frequency-hopping (FH)/spread- spectrum(SS) sequence is of great importance to high-security multiple-access communication systems, for it makes FH/SS sequence difficult to be analyzed. In this paper, a new complexity metric to evaluate the unpredictability of FH/SS sequence based on the Fuzzy Entropy(FuzzyEn) is presented. Simulation and analytical results show that, the proposed FuzzyEn works can effectively discern the changing complexities of the FH/SS sequences, and are compared with complexity metric based on the Approximate Entropy(ApEn). The FuzzyEn scheme has obvious advantages in the robustness to resolution parameter, the dependence to observation length and the sensitivity to vector dimension.

Minimizing the total transmission power is one of the main objectives of efficient broadcast algorithms in wireless networks, where all nodes are powered by battery with limited energy supply. Cooperative transmission is an important way to make full use of the space diversity and can save the transmission power significantly, especially in the wireless broadcast transmission, where the nodes can accumulate the overheard information. In this paper, firstly a centralized cooperative broadcast algorithm, which permits multiple nodes to cooperate in transmitting the broadcast message, is proposed to save the total transmission power. Considering that the centralized algorithm requiring a global knowledge of the networks is impractical in large wireless networks, the distributed version of the centralized algorithm requiring only 1-hop neighborhood information is proposed under the assumption that limited frequency band is available. The distributed algorithm combines the physical (PHY) and medium-access-control (MAC) layer mechanisms to reach all the nodes in a cooperative way. Though the proposed distributed algorithm is inferior to the centralized algorithm in terms of total transmission power, it takes less resource to broadcast than the centralized algorithms. Simulation results show that both the centralized algorithm and distributed algorithm can get a better performance than the existing broadcast algorithms. Furthermore, the distributed algorithm can achieve the total transmission power close to the centralized algorithm.

High complexity of frequency-hopping (FH)/spread-spectrum (SS) sequence is of great importance to high-security multiple-access communication systems, for it makes FH/SS sequence difficult to be analyzed. With the growing development in the design of FH/SS sequence in much wider fields, the well-known complexity measures-the linear complexity (LC), the linear complexity profile (LCP) and the k-error linear complexity (k-error LC)-are widely used but not sufficient to evaluate the complexities of the sequences available, such as the cryptographical sequence and the chaotic sequence families. In this paper, a new complexity metric to evaluate the unpredictability of FH/SS sequence based on the approximate entropy (ApEn) is proposed in the view of the maximal randomness of the sequences with arbitrary length. And the theoretical bounds of the ApEn are derived from a probabilistic point of view. Simulations and analysis results show that, the proposed ApEn works effectively to discern the changing complexities of the FH/SS sequences with small number of samples, which provide superior performance over its candidates.

According to the characteristics of meteor burst channels, variable rate data transmission is often employed to improve the average system throughput, and the time-varying meteor channel in the presence of multi-path rays brings difficulties in both data detection and channel estimation at the receiver. As we know, per-survivor processing (PSP) based on the joint data and channel estimation of maximum likelihood sequence detection (MLSD) is often considered to obtain the optimal detection performance for time-varying channels. However, the great computational complexity of PSP is the major problem in practice. In this paper we propose an adaptive state reduction of PSP (ASRP) algorithm with few states in the trellis diagram for exponential decay of meteor channels. Based on the estimation of the meteor channel parameters, the adaptive threshold is derived to select the states close to the right one in the trellis to reduce the complexity of PSP. Theoretical analysis and computer simulations results show that the ASRP we proposed provides suboptimal performance and makes good tradeoff between the performance and the computational complexity, so that the reliable data transmission can be realized for MBC systems with adaptive modulation and coding (AMC).

Spatial subchannels in multiuser multiple-input multiple-output/orthogonal frequency-division multiplexing (MIMO/OFDM) systems are invested. With the goal of maximizing the overall system throughput, we derive the criterion of subcarrier allocation and introduce an adaptive resource allocation algorithm. Furthermore, a time-frequency blockwise loading design which may decrease the computational complexity is suggested. The simulation results show that the algorithm can achieve good performance and high transmission rate efficiently.