Orthogonal frequency division multiplexing (OFDM) is an important technology that has been widely used in broadband wireless communications. However OFDM has some drawbacks, one of which is the high peak-to-average power ratio (PAPR) problem. Many techniques for reducing PAPR thus have been proposed in the literatures, where clipping and companding are effective techniques and have gained a lot of research interest. Based on the study of clipping and companding, this paper proposes a hybrid approach to reduce the PAPR of OFDM signals. An iterative clipping and filtering (ICF) technique and an enhanced nonlinear companding (ENC) scheme are used as the typical clipping and companding techniques in this paper. The results of the analysis show that the computational complexity of the proposed method is slightly higher than that of ENC, but much lower than that of ICF. And the simulation results show that the proposed method has better performance on PAPR reduction and bit error rate (BER) in contrast to ICF. On the other hand, compared to ENC with equal PAPR reduction, the proposed method still achieves better performance on BER.

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A Hybrid Approach to Reduce the PAPR of OFDM Signals Using Clipping and Companding

In this paper, a low complexity modified selective mapping (SLM) and companding based PAPR reduction scheme has been proposed to reduce the peak-to-average power ratio (PAPR) as well as computational complexity in localized orthogonal frequency division multiple access (OFDMA) system In long term evolution (LTE) downlink, OFDMA has been employed as a multiple access technique and uplink uses single carrier frequency division multiple access OFDMA systems preserve all the advantages and disadvantages of OFDM One of the major drawbacks in OFDMA is high PAPR In practice, SLM algorithms are most widely used to reduce PAPR due to its simple structure However, it suffers by more computational complexity To reduce complexity, in this paper three low complexity SLM structures are considered But, PAPR reduction is poorer than conventional SLM (C-SLM) Therefore, to further reduce PAPR, μ-law companding scheme is employed along with low complexity SLM in L-OFDMA To generate v candidate signal, first scheme employs one IFFT, scheme II uses two IFFT blocks and third proposed method uses (v/2 + 1) IFFT blocks In the first two proposed methods, the time domain sequences available at the output of IFFTs are convolved with perfect sequences In the third method, input data sequence is partitioned into two subblocks, first half of the input sequence is convolved with perfect sequence and C-SLM is applied to second half of the input data sequence μ-law companding is a non-linear companding transform which increases the average power of transmitting signals, thereby reducing PAPR of OFDM signal The simulation results show that, the proposed methods are well reducing PAPR with less computational complexity, so it is suitable for LTE downlink

A Low Complexity Modified SLM and Companding based PAPR Reduction in Localized OFDMA

The embodiment of the invention provides a cache resource allocation method and apparatus, applied to the technical field of resource utilization. The method comprises the following steps: segmenting a plurality of cache nodes in a core network into a plurality of network slices, randomly carrying out cache resource allocation on the cache nodes at first to obtain a current cache resource allocation matrix set, selecting a current cache resource allocation matrix in the set for optimization, until the current gain of a network operator corresponding to the optimized current cache resource allocation matrix is greater than the initial gain of the network operator corresponding to the selected current cache resource allocation matrix, obtaining a finally optimized cache resource allocation matrix, and carrying out cache resource allocation according the obtained cache resource allocation matrix. In combination with the internal network caching technology and the network slicing technology, the cache resources of the cache nodes are allocated to a plurality of network slices, and iterative optimization is performed on the cache resource allocation of the cache nodes to improve the cache resource allocation rate and the resource utilization rate.

Cache resource allocation method and apparatus

Single Carrier Frequency Division Multiple Access (SC-FDMA) has been implemented successfully for uplink communications in 3rd Generation Partnership Project Long Term Evolution. SC-FDMA has low peak to average power ratio (PAPR) in contrast to OFDMA due to lower signal envelope fluctuations in SC-FDMA signal. But still, there is a need to minimize PAPR in SC-FDMA systems. Although there are many methods to minimize PAPR in SC-FDMA systems they are highly complex or need side information to be transmitted. This paper proposes a new companding technique based on error function to minimize PAPR of conventional single carrier FDMA system in LTE uplink communications. Additionally, the proposed method improves the BER performance of single carrier FDMA system along with PAPR reduction. Simulation results demonstrate that proposed method provides better PAPR reduction when compared to μ law companding.

New error function companding technique to minimize PAPR in LTE uplink communications

The invention provides a method and a device for allocating resources The method comprises the following steps: (101) determining the interference situation of any two of a plurality of device-to-device (D2D) user pairs; (102) primarily allocating the resources to the D2D user pairs according to the interference situation of any two of the D2D user pairs so as to allocate only one resource to each of the D2D user pairs; (103) on the basis of primary resource allocation, secondarily allocating the resources to the D2D user pairs so as to allocate at least one resource to each of the D2D user pairs According to the method and the device for allocating the resources to the D2D user pairs, the resources can be allocated to the D2D user pairs to the greatest extent on the premise of avoiding interference between the D2D user pairs, so that the throughput of a system is greatly improved under the condition of D2D and system resource reuse

Method and device for allocating resources

The 3rd generation partnership project long term evolution standard uses orthogonal frequency division multiplexing access in downlink and single carrier frequency division multiple access (SCFDMA) scheme for the uplink transmissions, which utilizes single carrier modulation and frequency domain equalization. In this paper, we proposed a Raised Cosine-like companding scheme to reduce the peak-to-average power ratio (PAPR) of SCFDMA signals. The proposed scheme can transform the original SCFDMA signals into Raised Cosine-like-distributed. Moreover, this scheme can compress the large signals, while maintaining the average power constant. Computer simulation results show that the proposed companding scheme can offer better PAPR reduction by properly choosing the parameters.

Raised Cosine-Like Companding Scheme for Peak-to-Average Power Ratio Reduction of SCFDMA Signals

An incremental iterative time-varying channel evaluation and inter carrier interference (ICI) elimination method of fast orthogonal frequency division multiplexing (OFDM) system is applied in the field of wireless communication channel evolution, and is used for channel evaluation based on pilot frequency in the circumstance that a severe ICI influence of a time-varying channel occurs. The incremental iterative time-varying channel evaluation and ICI elimination method of fast OFDM system is characterized in that the sum of an ICI and a channel noise (SIN) is taken as a denosing object of a Kalman wave filter, and the ICI influence when the Kalman wave filter evaluates is eliminated. In addition, an incremental mode is used by data used for iteration, the number of the sub-carrier waves used for measurement increases slowly along two sides of each pilot frequency point in an iterative process, and thus the influence caused by the ICI is suppressed. The performance of the incremental iterative time-varying channel evaluation and ICI elimination method of fast OFDM system is improved significantly compared with an existing algorithm in the circumstance that signal noise ratio (SNR) is small.

Incremental iterative time-varying channel evaluation and inter carrier interference (ICI) elimination method of fast orthogonal frequency division multiplexing (OFDM) system

The 3rd generation partnership project (3GPP) long term evolution (LTE) standard has adopted orthogonal frequency division multiplexing access (OFDMA) in downlink and single carrier-frequency division multiple access (SC-FDMA) scheme for the uplink transmissions, which utilizes single carrier modulation and frequency domain equalization. In this paper, we proposed a power-function companding scheme to reduce the peak-to-average power ratio (PAPR) of SC-FDMA signals. The proposed companding scheme can transform the original SC-FDMA signals into power-function-distributed. Moreover, the scheme can compress the large signals, while maintaining the average power constant. Computer simulation results show that the proposed companding scheme can offer better PAPR reduction by properly choosing the control parameters.

Power Function Companding Scheme for Peak-to-Average Power Ratio Reduction of SC-FDMA Signals

The invention relates to a computing and wireless resource cooperative dispatching method in mobile cloud video transmission. The method comprises the steps that a system model, namely a cloud network abstract model is established; a video distortion model is established, an optimization target is provided; a random Restless Bandit system is established; and cloud service selecting and bandwidth distributing are carried out. The problem that in the prior art, system performance can be severely affected through respective and independent cloud and mobile resource management is solved, by combining a dynamic cloud network and wireless resource management, the end-to-end performance suitable for video transmission in a mobile cloud network computing system is improved, important video application layer parameters, namely the frame inner refresh rate are perfected, program quality is evaluated through distortion magnitude, and video distortion-preventing performance is improved.

Computing and wireless resource cooperative dispatching method in mobile cloud video transmission

The invention relates to a randomization sampling lattice decoding method based on limited distance decoding. The method comprises the steps of initializing settings, establishing an MIMO system lattice decoding model, conducting lattice reduction and QR decomposition on a channel matrix sequentially, conducting sampling decoding on received signals according to the depth-first search strategy to obtain candidate lattice points in a lattice reduction region, and decoded output. According to the decoding method, under the situation that the sampling frequency set initially is fixed, the decoding performance approaches the decoding performance of a randomization sampling decoding algorithm with the increasing of the length of a candidate lattice point list set initially and the increasing the of the number of nodes in a tree, and the performance the same as that of the randomization sampling decoding algorithm can be finally obtained with an access node number and a candidate lattice point number smaller than those of the randomization sampling decoding algorithm; the common breadth-first search strategy is replaced with the depth-first search strategy, the performance close to the optimum performance is obtained with a smaller search node number, complexity is reduced, and decoding efficiency is improved.

Sun Enchang

Papers

Raised Cosine-Like Companding Scheme for Peak-to-Average Power Ratio Reduction of SCFDMA Signals

Incremental iterative time-varying channel evaluation and inter carrier interference (ICI) elimination method of fast orthogonal frequency division multiplexing (OFDM) system

Power Function Companding Scheme for Peak-to-Average Power Ratio Reduction of SC-FDMA Signals

Computing and wireless resource cooperative dispatching method in mobile cloud video transmission

Randomization sampling lattice decoding method based on limited distance decoding