XI Wei, YIN Chang-Chuan, LE Guang-Xin, SUN Gong-Mei
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60499-4
Abstract ( 2202 ) PDF (0 KB)( 407 )
Fractional frequency reuse (FFR) is an effective technique to mitigate co-channel interference in orthogonal frequency division multiple access (OFDMA)-based broadband cellular systems. In this paper, we present a generalized model for FFR under which all existing FFR schemes can be considered as its special cases. Additionally, quality factor has been proposed to indicate the quality of the subband. An interesting conclusion can be drawn that, as the power ratio in FFR is adjusted continuously, the corresponding quality factor varies smoothly. Subsequently, simulation is conducted based on worldwide interoperability for microwave access (WiMAX), and the result agrees well with our theoretical analysis. Finally, an effective range for power ratio is presented, which is very instructive to practical system design
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60500-8
Abstract ( 2318 ) PDF (0 KB)( 405 )
The multi-cell uplink power allocation problem for orthogonal frequency division multiplexing access (OFDMA) cellular networks is investigated with the uplink transmission power allocation on each co-frequency subchannel being defined as a multi-cell non-cooperative power allocation game (MNPG). The principle of the design of the utility function is given and a novel utility function is proposed for MNPG. By using this utility function, the minimum signal to interference plus noise ratio (SINR) requirement of a user can be guaranteed. It can be shown that MNPG will converge to the Nash equilibrium and that this Nash equilibrium is unique. In considering the simulation results, the effect of the algorithm parameters on the system performance is discussed, and the convergence of the MNPG is verified. The performance of MNPG is compared with that of traditional power allocation schemes, the simulation results showing that the proposed algorithm increases the cell-edge user throughput greatly with only a small decrease in cell total throughput; this gives a good tradeoff between the throughput of cell-edge users and the system spectrum efficiency.
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60501-X
Abstract ( 2136 ) PDF (0 KB)( 437 )
According to the property rights model of cognitive radio, primary users who own the spectral resource have the right to lease or trade part of it to secondary users in exchange for appropriate profit. In this paper, an implementation of this framework is investigated, where a primary link can lease the owned spectrum to secondary nodes in exchange for cooperation (relaying). A novel pricing model is proposed that enables the trading between spectrum and cooperation. Based on the demand of secondary nodes, the primary link attempts to maximize its quality of service (QoS) by setting the price of spectrum. Taking the price asked by primary link, the secondary nodes aim to obtain most profits by deciding the amount of spectrum to buy and then pay for it by cooperative transmission. The investigated model is conveniently cast in the framework of seller/buyer (Stackelberg) games. Analysis and numerical results show that our pricing model is effective and practical for spectrum leasing based on trading spectral resource for cooperation.
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60502-1
Abstract ( 2139 ) PDF (0 KB)( 389 )
In this paper, the dynamic control approaches for spectrum sensing are proposed, based on the theory that prediction is synonymous with data compression in computational learning. Firstly, a spectrum sensing sequence prediction scheme is proposed to reduce the spectrum sensing time and improve the throughput of secondary users. We use Ziv-Lempel data compression algorithm to design the prediction scheme, where spectrum band usage history is utilized. In addition, an iterative algorithm to find out the optimal number of spectrum bands allowed to sense is proposed, with the aim of maximizing the expected net reward of each secondary user in each time slot. Finally, extensive simulation results are shown to demonstrate the effectiveness of the proposed dynamic control approaches of spectrum sensing.
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60503-3
Abstract ( 2234 ) PDF (0 KB)( 386 )
This paper analyzes the spectrum sensing performance over fading channel, in which a licensee and multiple unlicensed users coexist and operate in the licensed channel in a local area. The overall average probabilities of detection and false alarm by jointly taking the fading and the locations of all secondary users into account are derived, and a statistical model of cumulate interference is constructed. Based on the cumulate interference, a closed-form expression of outage probability at the primary user’s receiver according to a specific distribution of the fading is obtained. Finally, the sensing parameters so as to minimize the total spectrum sensing error and maximize the average opportunistic throughput are obtained. It is noted that the overall average performance analysis and results here enable to benchmark the design of specific spectrum sensing algorithms.
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60504-5
Abstract ( 2028 ) PDF (0 KB)( 207 )
In the paper, polarization-sensitive array is exploited at the receiver of multiple input multiple output (MIMO) radar system, a novel method is proposed for joint estimation of direction of departure (DOD), direction of arrival (DOA) and polarization parameters for bistatic MIMO radars. A signal model of polarimetric MIMO radar is developed, and the multi-parameter estimation algorithm for target localization is described by exploiting polarization array processing and the invariance property in both transmitter array and receiver array. By making use of polarization diversity techniques, the proposed method has advantages over traditional localization algorithms for bistatic MIMO radar. Simulations show that the performance of DOD and DOA estimation is greatly enhanced when different states of polarization of echoes is fully utilized. Especially, when two targets are closely spaced and cannot be well separated in spatial domain, the estimation resolution of traditional algorithms will be greatly degraded. While the proposed algorithm can work well and achieve high-resolution identification and accurate localization of multiple targets.
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60505-7
Abstract ( 1969 ) PDF (0 KB)( 385 )
Cellular relay networks adopting orthogonal frequency division multiple (OFDM) technology has been widely accepted for next generation wireless communication due to its advantage in enlarging coverage scale as well as improving data rate. In order to improve the performance of user equipments (UEs) near the cell edge, especially to avoid the interference from inter-cell and intra cell, an enhanced soft frequency reuse scheme is adopted in this paper to assure inter-cell interference coordination (ICIC). Compared with traditional frequency allocation work, the proposed scheme is interference-aware and load-adaptive, which dynamically assigns available frequency among UEs under certain schedule method in variable traffic load condition and mitigates interference using information provided by interference indicator. It can improve signal-to-interference plus noise ratio (SINR) of the UE in each sub channel thus enable the system achieve better throughput and blocking probability performance. Simulation results prove that the proposed scheme may achieve desirable performance on throughput, blocking probability and spectral utilization in the sector under different traffic load compared with other schemes.
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60506-9
Abstract ( 2337 ) PDF (0 KB)( 366 )
In orthogonal frequency-division multiplexing (OFDM) amplify-and-forward (AF) relay networks, in order to exploit diversity gains over frequency-selective fading channels, the receiver needs to acquire the knowledge of channel state information (CSI). In this article, based on the recent methodology of distributed compressed sensing (DCS), a novel channel estimation scheme is proposed. The joint sparsity model 2 (JSM-2) in DCS theory and simultaneous orthogonal matching pursuit (SOMP) are both introduced to improve the estimation performance and increase the spectral efficiency. Simulation results show that compared with current compressed sensing (CS) methods, the estimation error of our scheme is reduced dramatically in high SNR region while the pilot number is still kept small.
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60507-0
Abstract ( 2403 ) PDF (0 KB)( 397 )
In this paper, we investigate the power and subcarrier allocation issue in the case of partial side information for downlink orthogonal frequency division multiple access (OFDMA) system. Relaxation method is utilized to characterize the necessary conditions of the optimal solution and the uniqueness of the optimal solution is proved. The game theoretical concept, surplus function is also introduced to analyze the optimal solution. Based on the theoretical analysis, we propose iterative surplus balancing algorithm (ISBA) that can jointly assign the power and subcarriers in multiple rounds, and then the optimality of ISBA is proved. Simulation results are presented to show the characteristics of the theoretical analysis and ISBA.
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60508-2
Abstract ( 2599 ) PDF (0 KB)( 397 )
Channel estimation for orthogonal frequency division multiplexing (OFDM) systems operating over doubly selective channels is complicated by the existence of intercarrier interference (ICI). This paper extends the idea of estimating time-variant channel impulse response (CIR) via time-averaged CIR proposed by Hijazi, and proposes a low-complexity channel estimation scheme with ICI suppression based on Karhunen-Loeve basis expansion model (KL-BEM), which is in a more general form. In the proposed scheme, the KL-BEM coefficients are obtained through their numerical relationship with the time-averaged CIR. The estimation performance is improved by adopting an expectation-maximization (EM)-based iterative structure combined with a low-complexity ICI equalizer and canceller. Theoretical analysis and simulation results show that the proposed scheme achieves superior performance over the original one with lower computational complexity.
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60509-4
Abstract ( 2501 ) PDF (0 KB)( 418 )
Search efficiency and accuracy of resource are important considerations for search algorithm in peer-to-peer (P2P) network. Most search algorithms use flooding among neighbor nodes to search relevant resource. However, this usually causes great amount of redundant messages, which results in high search costs and low search precision. In this paper, we use vector space model (VSM) and relevance ranking algorithms to construct overlay network, and a novel search mechanism search with K-iteration preference (SKIP) based on semantic group for P2P networks is proposed to efficiently solve these problems. The key idea of SKIP is to reorder the semantic neighbors of nodes according to relevant scores and to utilize preference selection during the process of query. We analysis and implement the scheme and reveal that the SKIP provides a low overhead on topology maintenance, which can be effectively used in P2P searching and verify it outperformance in higher precision and lower search cost by comparing with current semantic-based searching mechanism gnutella-like efficient searching system (GES).
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60510-0
Abstract ( 2084 ) PDF (0 KB)( 370 )
This article studies the scalable broadcast scheme realized with the joint application of layered source coding, unequal error protection (UEP) and random network coding from the theoretical point of view. The success probability for any non-source node in a heterogeneous network to recover the most important layers of the source data is deduced. This probability proves that in this broadcast scheme every non-source node with enough capacity can always recover the source data partially or entirely as long as the finite field size is sufficiently large. Furthermore, a special construction for the local encoding kernel at the source node is proposed. With this special construction, an increased success probability for partial decoding at any non-source node is achieved, i.e., the partial decodability offered by the scalable broadcast scheme is improved.
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60511-2
Abstract ( 1992 ) PDF (0 KB)( 390 )
Network coding, which exploits the broadcast nature of wireless medium, is an effective way to improve network performance in wireless multi-hop networks, but the first practical wireless network coding system COPE cannot actively detect a route with more coding opportunities and limit the coding structure within two-hop regions. An on-demand coding-aware routing scheme (OCAR) for wireless Mesh networks is proposed to overcome the limitations specified above by actively detecting a route with more coding opportunities along the entire route rather than within two-hop regions. Utilizing more coding opportunities tends to route multiple flows ‘close to each other’ while avoiding interference requires routing multiple flows ‘away from each other’. OCAR achieves a tradeoff by adopting as routing metric in route discovery, which is not only coding-aware but also considers both inter and intra flow interference. Simulation results show that, compared with Ad-hoc on-demand distance vecfor routing (AODV) and AODV+COPE, OCAR can find more coding opportunities, thus effectively increase network throughput, reduce end to end delay and alleviate network congestion.
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60512-4
Abstract ( 2204 ) PDF (0 KB)( 347 )
This paper puts forward a novel cognitive cross-layer design algorithms for multihop wireless networks optimization across physical, mediam access control (MAC), network and transport layers. As is well known, the conventional layered-protocol architecture can not provide optimal performance for wireless networks, and cross-layer design is becoming increasingly important for improving the performance of wireless networks. In this study, we formulate a specific network utility maximization (NUM) problem that we believe is appropriate for multihop wireless networks. By using the dual algorithm, the NUM problem has been optimal decomposed and solved with a novel distributed cross-layer design algorithm from physical to transport layers. Our solution enjoys the benefits of cross-layer optimization while maintaining the simplicity and modularity of the traditional layered architecture. The proposed cross-layer design can guarantee the end-to-end goals of data flows while fully utilizing network resources. Computer simulations have evaluated an enhanced performance of the proposed algorithm at both average source rate and network throughput. Meanwhile, the proposed algorithm has low implementation complexity for practical reality.
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60513-6
Abstract ( 2102 ) PDF (0 KB)( 391 )
This article puts forward a novel routing architecture for complex optical network, which core component is path calculation element (PCE). As is well known, the PCE-based distributed path computation structure is making the routing control and computation loosely coupled from traditional control plane. In the study, the resource allocation and routing algorithm are the critical part of PCE hierarchy. To compare the performance of new architecture and the traditional one, the user uses the flooding suppression, routing delay, resource utilization and traffic blocking probability as performance simulation parameters and taking the verification simulation on objective modular network testbed (OMNeT) platform against to source-node routing architecture. The numerical analysis, computer simulation and experiment work indicate that the operation of PCE-based routing architecture can reduce the flooding information of path calculation request as well as the routing hops significantly and improve the quality of service (QoS) by decreasing the blocking probability when failure happened.
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60514-8
Abstract ( 2041 ) PDF (0 KB)( 376 )
With the fast development of the micro-electro-mechanical systems (MEMS), wireless sensor networks (WSNs) have been extensively studied. Most of the studies focus on saving energy consumption because of restricted energy supply in WSNs. Cluster-based node scheduling scheme is commonly considered as one of the most energy-efficient approaches. However, it is not always so efficient especially when there exist hot spot and network attacks in WSNs. In this article, a secure coverage-preserved node scheduling scheme for WSNs based on energy prediction is proposed in an uneven deployment environment. The scheme is comprised of an uneven clustering algorithm based on arithmetic progression, a cover set partition algorithm based on trust and a node scheduling algorithm based on energy prediction. Simulation results show that network lifetime of the scheme is 350 rounds longer than that of other scheduling algorithms. Furthermore, the scheme can keep a high network coverage ratio during the network lifetime and achieve the designed objective which makes energy dissipation of most nodes in WSNs balanced.
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60515-X
Abstract ( 1921 ) PDF (0 KB)( 358 )
This article puts forward an Ad-hoc on-demand distance vector routing (AODV) routing overhead analysis method in mobile Ad-hoc network (MANET). Although multiple routing protocols have been proposed to improve the performance, scarcely any paper analyzed the routing overhead caused by routing setup and maintenance processes in mathematical way. Routing overhead consumes part of network resources and limits the supported traffic in the network. For on-demand routing protocols like AODV, the routing overhead depends on the link failure probability to a great extent. This article analyzes the collision probability caused by hidden-node problem and the impact on link failure probability. In chain and rectangle scenarios, it presents a mathematical analysis of the theoretical routing overhead of AODV protocol based on link failure probability. Simulations on OPNET 14.5 platform match well with the theoretical derivation which confirms the effectiveness of the analysis method.
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60516-1
Abstract ( 1945 ) PDF (0 KB)( 329 )
Hierarchical B-frames can bring high coding performance when introduced into H.264/AVC. However, the traditional rate control schemes can not work efficiently in such new coding framework. This article presents a rate control algorithm for hierarchical B-frames in H.264/AVC. Taking the feature of the dyadic hierarchical coding structure into consideration, the proposed algorithm includes group of pictures (GOP) layer, temporal layer and frame layer bits allocation. After frame layer bits allocation is complete, frame layer quantization parameters (QP) determination strategy is responsible for calculating the final QP. Experimental results show that compared with other rate control algorithms, the proposed one can improve the coding performance and reduce the mismatch of target bit rate and real bit rate.
The Journal of China Universities of Posts and Telecommunications, 2010, 17 (5). doi： 10.1016/S1005-8885(09)60517-3
Abstract ( 2093 ) PDF (0 KB)( 387 )
In optical coherent receivers, the timing error detector (TED) in synchronization loop can not work normally when signal is distorted by large dispersion. This paper proposes a novel clock synchronization scheme which adds a butterfly-structured adaptive equalizer to the loop to fulfill synchronizations, equalizations and polarization de-multiplexing of two polarization states simultaneously under the control of single voltage-controlled oscillator (VCO). Simulink simulation demonstrates the rationality and the feasibility of the combined loop with single VCO.