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Adaptive power loading with BER-constraint for OFDM systems

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The Journal of China Universities of Posts and Telecommunications 2009年第4期16卷 91-97页

作者： liu kai-ming ZHAO Jing CHEN Chang-xiang liu Yuan-an School of Electronic Engineering Beijing University of Posts and Telecommunications Beijing 100876 China International school Beijing University of Posts and Telecommunications Beijing 102209 China The No.30 Institute of China Electronic Technology Corporation Chengdu 610041 China

A novel adaptive power loading algorithm with the constraint of target overall bit error rate （BER） for orthogonal frequency division multiplexing （OFDM） systems is proposed in this article. The proposed algorithm aims to minimize the required transmit power with fixed data rate and uniform （nonadaptive） bit allocation, while guaranteeing the target overall BER. The power loading is based on the unequal-BER （UBER） strategy that allows unequal mean BERs on different subcarriers. The closed-form expressions for optimal BER and power distributions are derived in this article. Simulation results indicate the superiority of the proposed algorithm in terms of BER performance and algorithmic complexity.

关键词： OFDM adaptive modulation power loading unequal-BER uniform bit allocation

Fairness-oriented routing algorithm joint with power control and channel assignment for multi-radio multi-channel wireless mesh networks

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The Journal of China Universities of Posts and Telecommunications 2014年第5期21卷 55-60页

作者： liu kai-ming MA Tao liu Yuan-an KOU Ke-hao School of Electronic Engineering Beijing University of Posts and Telecommunications Beijing Key Laboratory of Work Safety Intelligent Monitoring Beijing University of Posts and Telecommunications

The multi-radio multi-channel wireless mesh network （MRMC-WMN） draws general attention because of its excellent throughput performance, robustness and relative low cost. The closed interactions among power control （PC）, channel assignment （CA） and routing is contributed to the performance of multi-radio multi-channel wireless mesh networks （MRMC-WMNs）. However, the joint PC, CA and routing （JPCR） design, desired to achieve a global optimization, was poor addressed. The authors present a routing algorithm joint with PC and CA （JPCRA） to seek the routing, power and channel scheme for each flow, which can improve the fairness performance. Firstly, considering available channels and power levels, the routing metric, called minimum flow rate, is designed based on the physical interference and Shannon channel models. The JPCRA is presented based on the genetic algorithm （GA） with simulated annealing to maximize the minimum flow rate, an non-deterministic polynomial-time hard （NP-Hard） problem. Simulations show the JPCRA obtains better fairness among different flows and higher network throughput.

关键词： channel assignment routing power control mesh networks multi-radio multi-channel

Parametric channel modeling based OFDM channel estimation

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The Journal of China Universities of Posts and Telecommunications 2014年第5期21卷 1-8页

作者： QING Hao-bo liu Yuan-an XIE Gang liu kai-ming liu Fang Beijing Key Laboratory of Work Safety Intelligent Monitoring Beijing University of Posts and Telecommunications Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and Telecommunications

A simplified parametric channel estimation approach was proposed for orthogonal frequency division multiplexing （OFDM） systems. Based on parametric channel model, this algorithm is composed of two parts： the estimation of channel parameters and channel interpolation. The exponentially embedded family （EEF） criterion is exploited to determine the number of channel paths as well as the multipath time delays. Consequently, the channel frequency responses is acquired via the estimated parameters. Additionally, the authors＇ scheme is computationally efficient owing to the needless of the eigenvalue decomposition or the estimation of signal parameters by the rotational invariance technique （ESPRIT）. Simulations are provided to validate the performance of this algorithm from perspectives of the probability of correct estimation and the mean square error （MSE）. It is demonstrated that this approach exhibits a superior performance over the existing algorithms.

关键词： channel estimation OFDM mean square error EEF criterion

Throughput oriented forwarders selection analysis for opportunistic routing in wireless mesh network

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The Journal of China Universities of Posts and Telecommunications 2013年第2期20卷 73-78页

作者： DU Xiao liu Yuan-an liu kai-ming TANG Bi-hua CHEN Xing School of Electronic Engineering Beijing University of Posts and Telecommunications

Opportunistic routing explicitly takes advantage of the broadcast nature of wireless communications by using a set of forwarders to opportunistically perform packet forwarding. A key issue in the design of opportunistic routing protocols is the forwarder list selection problem. This paper proposes a novel routing metric which shows the end-to-end throughput and a corresponding throughput oriented opportunistic routing forwarder-selecting algorithm throughput oriented forwarders selection （TOFS） through analyzing forwarding characteristics of forwarders. The algorithm puts forward a constraint mechanism that controls the number of forwarders by constraint of throughput for forwarders selection, achieving a better balance between number of forwarders and effective link stability by introducing the factor of transmission time. Simulation results show that the algorithm can improve the network end-to-end throughput effectively over existing methods.

关键词： wireless mesh networks (WMN) opportunistic routing throughput delivery probability

Degrees of freedom for MIMO interference broadcast channels

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The Journal of China Universities of Posts and Telecommunications 2014年第6期21卷 9-16页

作者： REN Hai-ying liu Yuan-an liu Fang GAO Jin-chun liu kai-ming XIE Gang School of Electronic Engineering Beijing University of Posts and Telecommunications

Multiple-input multiple-output（MIMO） interference broadcast channel（IBC） plays an important role in the modern wireless communications. The upper bound of degrees of freedom（Do F） and its corresponding achievable schemes was investigated. However, all the achievable schemes require perfect channel state information at transmitters（CSIT）. In absence of CSIT, the Do F value is still unknown. This article mainly focuses on the G-cell K-user MIMO IBC, where there are M antennas at each transmitter and N antennas at each receiver. The transmitters only know channel coherence time internals rather than the values of channel coefficients. The users in the same cell are assumed to be able to share the channel information. Based on a heterogeneous semi-staggered block fading model, a blind interference alignment（IA） scheme was proposed for this scenario. It is shown that when R≥1（ G-1） and R =min（M, KN） max（M, KN）, a total of GKMN（ M ＋KN） Do F can be achieved. The inner bound is same with the decomposition Do F upper bound. Since the complexity is an important performance index to evaluate the achievable scheme, the quantitative analysis for the complexity is presented.

关键词： blind IA DoF IBC MIMO

Resource scheduling in downlink LTE-advanced system with carrier aggregation

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The Journal of China Universities of Posts and Telecommunications 2012年第1期19卷 44-49,123页

作者： LIN Le-xiang liu Yuan-an liu Fang XIE Gang liu kai-ming GE Xin-yang School of Electronic Engineering Beijing University of Posts and Telecommunications Beijing 100876 China School of Information and Communication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

In this paper, we focus on the resource scheduling in the downlink of long term evolution advanced （LTE-A） assuming equal power allocation among subcarriers. Considering the backward compatibility, the LTE-A system serves LTE-A and long term evolution （LTE） users together with carrier aggregation （CA） technology. When CA is applied, a well-designed resource scheduling scheme is essential to the LTE-A system. Joint scheduling （JS） and independent scheduling （INS） are two resource scheduling schemes. JS is optimal in performance but with high complexity. Whereas INS is applied, the LTE users will acquire few resources because they can not support CA technology. And the system fairness is disappointing. In order to improve the system fairness without bringing high complexity to the system, an improved proportional fair （PF） scheduling algorithm base on INS is proposed. In this algorithm, we design a weigh factor which is related with the number of the carriers and the percentage of LTE users. Simulation result shows that the proposed algorithm can effectively enhance the throughput of LTE users and improve the system fairness.

关键词： LTE-advanced system resource allocation cartier aggregation proportional fairness

Capacity analysis of based-regular-topologies cognitive wireless mesh networks with power control

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The Journal of China Universities of Posts and Telecommunications 2013年第5期20卷 71-78页

作者： KOU Ke-hao TANG Bi-hua liu kai-ming MA Tao School of Electronic Engineering Beijing University of Posts and Telecommunications Beijing Key Laboratory of Work Safety Intelligent Monitoring Beijing University of Posts and Telecommunications

Capacity analysis is a fundamental and essential work for evaluating the performance of cognitive wireless mesh network （CWMN） which is considered a promising option for the future network. Power control is an efficient way to avoid interference and improve capacity of wireless mesh networks. In this paper, a quantitative result of the per-node average throughput capacity of CWMN with power control is deduced for the first time, which is much helpful for understanding the limitations of CWMN. Firstly, under the large-scale channel fading model and protocol interference model, a closed-form expression for the maximum channel capacity of each node with power control is presented, under the constraint that the interference tolerated by the primary users （PUs） does not exceed a threshold. And then, with the deduced channel capacity result, the per-node average throughput capacity of CWMN is derived based on two regular topologies, i.e. square topology and triangle topology. The simulation results indicate that the capacity is effectively improved with power control, and affected by topology, tolerated interference threshold, the number of cognitive users （CUs） and primary users （PUs）.

关键词： capacity cognitive wireless mesh networks power control regular topologies

Distributed channel assignment combined with routing over multi-radio multi-channel wireless mesh networks

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The Journal of China Universities of Posts and Telecommunications 2012年第4期19卷 6-13页

作者： YUAN Fei-fei LI Xu liu kai-ming liu Yuan-an DU Xiao SHI Xin-rong School of Electronic Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China

In order to realize the reduction of equipment cost and the demand of higher capacity, wireless mesh network （WMN） router devices usually have several interfaces and work on multi-channels. Jointing channel allocation, interface assignment and routing can efficiently improve the network capacity. This paper presents an efficient channel assignment scheme combined with the multi-radio link quality source routing （MR-LQSR） protocol, which is called channel assignment with MR-LQSR （CA-LQSR）. In this scheme, a physical interference model is established： calculated transmission time （CTT） is proposed as the metric of channel assignment, which can reflect the real network environment and channel interference best, and enhanced weighted cumulative expected transmission time （EWCETT） is proposed as the routing metric, which preserves load balancing and bandwidth of links. Meantime, the expression of EWCETT contains the value of CTT, thus the total cost time of channel assignment and routing can be reduced. Simulation results show that our method has advantage of higher throughput, lower end-to-end time delay, and less network cost over some other existing methods.

关键词： wireless mesh networks distributed channel assignment routing protocol MR-LQSR CA-LQSR

Distributed interference suppression scheme for multi-cell uplink OFDMA system based on non-cooperative game

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The Journal of China Universities of Posts and Telecommunications 2011年第2期18卷 65-71页

作者： CHANG Ling-jun TANG Bi-hua XIE Gang ZENG Ling-kang liu kai-ming School of Electronic Engineering Beijing University of Posts and Telecommunications Beijing 100876 China School of Information and Communication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

In this paper,a distributed interference suppression scheme is proposed for multi-cell uplink orthogonal frequency division multiple access（OFDMA） ***,we model resource allocation process as a non-cooperative *** we show the concept of Nash equilibrium（NE） and investigate its existence and uniqueness in *** enhance the performance of multi-cell OFDMA system,the further improvement process based on NE is *** adjustable parameters are set to make the system achieve different tradeoffs between the total capacity and *** results show that the proposed scheme can greatly improve the system performance comparing with conventional scheme.

关键词： multi-cell non-cooperative game OFDMA uplink ICI