Qiyue Yu

A configurable dual-mode algorithm on delay-aware low-computation scheduling and resource allocation in LTE downlink

Long Term Evolution (LTE) has been proposed as a promising radio access technology to bring higher peak data rates and better spectral efficiency. However, scheduling and resource allocation in LTE still face huge design challenges due to their complexity. This paper divides the complex problem into three sub-problems: scheduling pattern, scheduling priority and quantity of scheduled data. Based on analysis of three sub-problems, a configurable dual-mode (CD) algorithm is proposed. CD algorithm is able to guarantee queuing delay with low loss of resource utilization and fairness by employing dual-mode scheduling mechanism. And it can be configured by three parameters catering to different performance requirements. By utilizing QoS Class Identifier (QCI) and Channel Quality Indicator (CQI) defined by LTE, low computation is realized in CD scheduler. Finally, performance evaluation of the proposed scheduler is presented. The results and correlative analysis testify effectiveness of CD algorithm.

Virtual multi-beamforming for distributed satellite clusters in space information networks

This article introduces some basic theories of space information networking (SIN), which is a novel research field. A SIN is a network that is able to achieve real-time acquisition, transmission, and processing of space information. The article first investigates the basic satellite-terrestrial architecture of SINs, and then three key technologies of SINs are presented, specifically more details on the high data rate transmission theory. The DSC is the foundation of high data rate transmission; thus, the core technology of DSC, which is beam/beamforming theory, is discussed in detail. Compared to the traditional spot beam theory, this article proposes a novel VBF concept, which is capable of increasing the channel capacity. Some key technologies are also investigated for VBF; they are channel capacity theoretical analysis, opportunistic beamforming, virtual multi-beamforming, and resource management.

A survey of two kinds of complementary coded CDMA wireless communications

In this article, we present a comprehensive survey of existing literature in the area of complementary coded CDMA (CC-CDMA) technique for wireless communications to provide an introduction and overview to the field. According to the kinds of independent sub-channels, we divide the existing CC-CDMA solutions into two categories: time division multiplex (TDM) and frequency division multiplex (FDM) CC-CDMA systems. Then we compared them in terms of resistance of multiuser interference and multi-path interference, implementation complexity and spread and spectrum efficiency.

A Novel Stability Weighted Clustering Algorithm for Multi-Hop Packet Radio Virtual Cellular Network

Cooperative communications exploit the spatial diversity inherent in multiuser system by allowing cooperation among users having a wide range of channel qualities. How to search the cluster-head and its member relay nodes to cooperate is important. Since nodes are coming into or out of the clusters time to time, the network topology is perturbed and the reconfiguration of the network is unavoidable. In this paper, we propose a new algorithm called stability weighted clustering algorithm (SWCA) to solve this problem. We define the stability by using a new metric of mobility. In the traditional WCA, the speed of every separate node is considered. However, our proposed algorithm introduces a new weight factor, which uses the relative speed of two nodes to represent the mobility of the network. Simulation results show that the SWCA achieves better stability than the traditional WCA while it performs almost the same performance as the WCA with respect to the dominant set update rate and the load balancing factor (LBF).

Application of cyclic delay transmit diversity to uplink 2-dimensional block spread CDMA with frequency-domain equalization

The presence of the multi-access interference (MAI) limits the uplink performance of code division multiple access (CDMA). 2-dimensional (2D) block spread CDMA makes it possible to achieve MAI free uplink transmission while obtaining the frequency diversity gain by using low-complexity single-user frequency-domain equalization (FDE). To further improve the uplink transmission performance, the transmit diversity technique can be used. Cyclic delay transmit diversity (CDTD) can strengthen the frequency-selectivity of the channel. In this paper, we apply CDTD to 2D block spread CDMA with MMSE-FDE. The achievable uplink BER performance is evaluated by computer simulation for both direct sequence CDMA and multi-carrier CDMA. It is shown that CDTD can offer improved uplink BER performance in a frequency-selective uplink channel.

Evolution from symbol-level space-time coded MIMO to chip-level space-time coded MIMO: a review

Space-time coded multiple-input multiple-output MIMO technology is an important technique that improves the performance of wireless communication systems significantly without consuming bandwidth resource. This paper first discusses the characteristics and limitations of traditional symbol-level space-time coding schemes, which work largely on the basis of an assumption that signals are sent to a block-fading channel. Therefore, the symbol-level space-time coding schemes rely on symbol-level signal processing. Taking advantage of orthogonal complementary codes, we propose a novel MIMO scheme, in this paper, based on chip-level space-time coding that is different from the traditional symbol-level space-time coding. With the help of space-time-frequency complementary coding and multicarrier modem, the proposed scheme is able to achieve multipath interference-free and multiuser interference-free communications with simple a correlator detector. The proposed chip-level space-time coded MIMO works well even in a fast fading channel in addition to its flexibility to achieve diversity and multiplexing gains simultaneously in varying channel environments. Copyright

A Novel Weighted Clustering Algorithm Based on Power Distribution for Cooperative Communication Network

Cooperative communications is widely used to share the resources of different nodes, and achieve spatial diversity gain in multi-user network. The node which is chosen as cooperative node (cluster-head), consumes more transmit power for other nodes than itself. Because of this, traditional algorithm results in uneven power distribution. In this paper, we propose a new algorithm called weighted clustering algorithm based on power distribution (PDWCA) to solve the problem. Compared with traditional weighted clustering algorithm (WCA), the proposed algorithm adds a new weight factor decided by the power reward, which evaluates the power contributed to or service by others so as to guarantee uniform power distribution. In this paper, we also give a new definition of the measure of mobility which is more clear than the traditional one. Simulations results show that the performances are similar to WCA in terms of cluster-head number and load balancing factor (LBF); meanwhile, it can reach much better improvement on average transmit power.

Joint UKF and MMSE Channel Estimation for Uplink 2-Dimensional Block Spread MC-CDMA with Cyclic Delay Transmit Diversity

Multi-access interference (MAI) free uplink transmission can be achieved by 2-dimensional (2D) block spread code division multi access (CDMA), and low-complexity single-user frequency-domain equalization (FDE) is performed at base station to obtain the frequency diversity gain. Cyclic delay transmit diversity (CDTD) can further improve the transmission performance by obtaining a larger frequency diversity gain in the frequency selective fading channel. However, accurate estimation of the channel transfer function is the premise for the use of 2D block spread CDMA with CDTD. Unscented Kalman filter (UKF) is an attractive technology and suitable for the Rayleigh channel estimation in time domain, which can be used to assist the minimum mean square error (MMSE) criterion based channel estimation (CE) to improve the BER performance. This paper proposes a joint UKF and MMSE criterion CE method. The achievable uplink BER performance is evaluated by computer simulation for 2D block spread multi-carrier (MC) CDMA, which shows that the joint CE can improve the BER performance about 0.8dB compared with MMSE-CE when BER=10-4.

2FSK modulation for multiuser physical-layer network coding network

The physical-layer network coding (PNC) has become a hot research topic, since it can potentially reduce the transmission time slots and increase the channel capacity. However, current studies are mainly concentrated on three nodes (two users and one relay) network. This paper considers a specific multiuser network that includes M (M>2) users with one relay, and illustrates the transmission scheme and evaluates its bit error rate (BER), information theoretical capacity and anti-noise performance under AWGN channel. Moreover, 2FSK is considered in the proposed network, since it does not need accurate phase tracking. Simulation results show that its information theoretical capacity would decrease significantly with the number of users in this network increase, however the capacity of the proposed scheme is still better than that of the IEEE802.11 networks.

Maximum product of effective channel gains: an innovative user selection algorithm for downlink multi-user multiple input and multiple output

Recently, zero-forcing beamforming has been widely used for multiple-input and multiple-output broadcast channels, because it could provide suboptimal capacity with low complexity. To increase the sum data rate, a good user selection algorithm is attractive. In this paper, a new user selection algorithm named maximum product of effective channel gains is presented. The proposed algorithm is described mathematically, and the lower bound of the sum capacity is demonstrated to be proportional to the product of effective channel gains. Our simulation results show that maximum product of effective channel gains can achieve higher sum rate compared with the classical algorithm, semi-orthogonal user selection, with the same complexity order, especially when the signal-to-noise ratio is high; in addition, the complexity of the proposed algorithm is superior to minimum of the Frobenius norm of the pseudo-inverse algorithm. Meanwhile, the number of users that can be served simultaneously is equal to the number of transmission antennas, which is the maximum performance that can be achieved.Copyright