中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60280-0
摘要 ( 2403 ) PDF (199 KB)( 422 )
Customers’ satisfaction with services is reflected by quality of experience (QoE). Insofar, most studies on cooperative communication have been focused on improving the QoE of source users. However, the improvement of a source user’s QoE is obtained at cost of degradation of the relay user’s QoE. On the other hand, cooperative communications can achieve performance similar to that of a conventional multiple-input multiple-output (MIMO) system by forming virtual MIMO arrays. Hence, to improve the QoE performance of relay users, this article proposes the concept of a belief threshold at the destination user and a new cooperative scheme based on the belief threshold destination (BTD) technique, while without decaying the BER performance of the communication system.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60281-2
摘要 ( 3112 ) PDF (287 KB)( 422 )
The impact of mutual coupling on the performance of multiple-input multiple-output (MIMO) systems with compact antenna arrays is analyzed. This article aims to use the S-parameter modeling approach to examine the impact of mutual coupling on three system-related performance measures: antenna correlation, efficiency and bandwidth. It is shown that implementing a good matching network can drastically improve the system performance in the presence of strong mutual coupling. Experiment results indicate the superiority of cross-shaped antenna to dipole antenna.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60282-4
摘要 ( 3059 ) PDF (233 KB)( 419 )
By deducing the distribution of the normalized channel covariance matrix, a novel limited feedback scheme is proposed under multiple users (MU) multiple-input multiple-output (MIMO) broadcast channel (BC) system. The proposed scheme has advantages in three aspects. First, it has no constraints on the number of users or antennas. Second, each user’s feedback bits are independent of the number of receiving antennas. Third, the proposed scheme avoids the storage of large-size codebook on the transceivers. Simulation results show that the performance of the proposed scheme is close to the perfect channel state information (CSI) case and it just needs a small number of feedback bits.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60283-6
摘要 ( 2510 ) PDF (300 KB)( 452 )
This article puts forward a novel channel estimation and inter-carrier interference (ICI) suppression method for time-varying orthogonal frequency division multiplexing (OFDM) systems. The proposed adaptive finite impulse response (FIR) filter utilizes the time domain correlation of the subcarriers. Based on the one order auto-regressive (AR) model, a modified Kalman filter is exploited to track the channel variance. By solving the Yule-Walker equation, the coefficient of the AR process can be obtained from zero order Bessel function. However, when the channel is assumed not perfectly known, the above criterion will lead to an impractical application. To deal with it, the coefficient of the AR process is taken as a constant. Subsequently a new state space model is deduced and found. Simulation results show that the proposed method can work effectively at the speed of 144 km/h with a phase noise of 85 dBc/Hz at 100 kHz offset. The proposed method yields an improvement bit error rate (BER) compared with three of the existing algorithms with much lower complexity.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60284-8
摘要 ( 4079 ) PDF (320 KB)( 477 )
IEEE 802.15.4 protocol has attracted much attention in research and industrial communities as candidate technology for wireless body area sensor networks (WBASNs). IEEE 802.15.4 supports the exclusive use of a wireless channel through guaranteed time slot (GTS). However, on one hand, bandwidth underutilization rate may be lower because of the variance between the guaranteed bandwidth and the arrival rate. On the other hand, the waiting time for transmitting emergency notification is getting longer when the GTSs assigned to the nodes increase in WBASNs. To solve these problems, in this article, a new scheme is proposed to reduce transmission delay for the alarm notification in emergent situations. Simulation results are presented to validate the efficiency of the proposed scheme by comparing it with the medium access control (MAC) protocol of IEEE 802.15.4.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60285-X
摘要 ( 2367 ) PDF (295 KB)( 387 )
Hybrid automatic repeat request (HARQ) is a well-known technique for improving system throughput and link performance of wireless communication systems, including cooperative communication systems. The amplify-and-forward (AF) relaying method is one of the most attractive cooperative diversity schemes because of its low complexity. In this article, the end-to-end performance in terms of block error rate (BLER) and normalized throughput of AF relaying with HARQ transmission under the Rayleigh fading channel is analyzed. Numerical results validate the proposed analysis and demonstrate the gain of HARQ schemes in AF relaying systems. This analytical method can be extended to the systems with other HARQ protocols and other cooperative relaying schemes.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60286-1
摘要 ( 2543 ) PDF (190 KB)( 394 )
Multiple-input multiple-output (MIMO) technology can provide high data rate and substantial diversity. Space time block code (STBC) provides diversity gain and obtains signal of better quality even under bad channel conditions. However, it has no contribution to system average throughput. Vertical-bell laboratory layered space-time (VBLAST) improves peak data rate but leads to higher packet error rate (PER) at cell edge when the channel condition is poor. To get both higher system average throughput and cell edge throughput, an adaptive STBC-VBLAST transmission for downlink mobile WiMAX system is proposed and analyzed through system-level simulation in this article. The proposed approach compares the effective capacity of two candidate MIMO modes (STBC or VBLAST) and reports its decision to the base station with only one extra signaling bit. The simulation results show that the proposed approach can attain a balance between STBC and VBLAST. Besides, the cell throughput approximates that of pure VBLAST and the cell edge throughput is close to that of pure STBC.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60287-3
摘要 ( 2841 ) PDF (311 KB)( 1095 )
The error vector magnitude (EVM) is extensively applied as a metric for digital transmitter signal quality compliance in modern communication systems. This article is focused on the effects of local oscillator (LO) phase noise and nonlinear distortion of power amplifier on EVM. This article contributes to below aspects. First, the relationships between EVM and two effects, LO phase noise and nonlinear distortion of power amplifier, are derived and expressed. Second, to simplify the expression, the third-order intermodulation distortion (IMD3) is used to calculate the EVM. Then, an expression for the EVM is derived based on the digital transmitter model that considers local oscillator phase noise and nonlinear distortion of power amplifier. Finally, the math formula of bit error rate (BER) versus EVM is given which can be easier and more useful to predict BER, according to analysis of the relationship between EVM and signal to noise rate (SNR), inspired by the works of Rishad, Md. Shahriar and AHM, 2006. Simulations are carried out to display the performance of EVM based on these relationships.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60288-5
摘要 ( 3009 ) PDF (688 KB)( 542 )
Performance analysis and test for passive radio frequency identification (RFID) system at ultra high frequency (UHF) band in free space and line-of-sight (LOS) indoor environments are conducted in this article. Performance degradation of different materials is presented, in terms of power received by tag and reader, communication range and link information rates, etc. Particularly, the multipath fading and root mean square (RMS) delay spread in LOS indoor environments are analyzed by a 5-ray model with different polarization, such as horizontal polarization, vertical polarization and circular polarization. A practical test is carried out on an indoor balcony of an office building. In addition, the electric field environment is simulated to analyze multipath degradation using the tool of Ansoft HFSS. According to the test, the recognition rate is almost consistent with the results of theoretical analysis and simulation. The small scale fading and the field nulls are observed. The multipath degradation significantly affects the passive RFID system on communication range and recognition rate, and it is also one of the key limitations on system performance. The variations of power in multipath environments can also influence the information rates, while the rates are still enough for available standard and applications at short range.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60289-7
摘要 ( 2016 ) PDF (263 KB)( 452 )
Current quality of service (QoS) routing schemes for low earth orbit (LEO) satellites IP networks either neglect the varying population density or fail to guarantee end-to-end delay. As a remedy, QoS routing protocol based on mobile agent (QoSRP-MA) is proposed. QoSRP-MA is a source-based routing protocol. Once connection requests arrive, QoS mobile agents are dispatched from ingress satellite to explore routes, which migrate using satellite routing tables. Upon arriving in egress satellite, QoS mobile agents migrate back towards ingress satellite to reserve bandwidth. To construct satellite routing tables, load balancing routing algorithm based on mobile agent (LBRA-MA) is presented. In LBRP-MA, at regular intervals mobile agents launched on all satellites migrate autonomously to evaluate path cost and update routing tables. Moreover, path cost between source and destination is evaluated considering satellite geographical position as well as inter-satellite link (ISL) cost. Furthermore, ISL congestion index is considered to update routing table. Through simulations on a Courier-like constellation, it shows that QoSRP-MA can achieve guaranteed end-to-end delay bound with higher throughput, lower connection failing ratio and signaling overhead compared to high performance satellite routing (HPSR) scheme.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60290-3
摘要 ( 2171 ) PDF (324 KB)( 409 )
Real-time variable bit rate (VBR) video is expected to take a significant portion of multimedia applications. However, plentiful challenges to VBR video service provision have been raised for its characteristic of high traffic abruptness. To support multi-user real-time VBR video transmission with high bandwidth utilization and satisfied quality of service (QoS), this article proposes a practical dynamic bandwidth management scheme. This scheme forecasts future media rate of VBR video by employing time-domain adaptive linear predictor and using media delivery index (MDI) as both QoS measurement and complementary management reference. In addition, to support multi-user application, an adjustment priorities classified strategy is also put forward. Finally, a test-bed based on this management scheme is established. The experimental results demonstrate that the scheme proposed in this article is efficient with bandwidth utilization increased by 20%60% compared to a fixed service rate and QoS guaranteed.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60291-5
摘要 ( 2053 ) PDF (433 KB)( 403 )
In this article, the problem of load balance in hierarchical routing network is studied. Since conventional shortest path first (SPF) algorithm over aggregated topology in hierarchical routing network may result in worse routing performance, a traffic sharing path selection algorithm and a variable weight scheme are put forward for hierarchical routing network, which can equilibrate the utilities of link resources and reduce the blocking probability of connections with the improvement on survivability. Simulations are conducted to evaluate proposed variable weight and traffics balance (VWTB) algorithm, which combines traffic sharing and variable weight. From the simulation results, it can be found that the proposed VWTB algorithm can balance the traffics and equilibrate the utilities of link resources significantly.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60292-7
摘要 ( 3364 ) PDF (261 KB)( 384 )
In this article, the capacity of wireless multi-hop networks with the frequency hopping (FH) technique is derived. Different from the previous work based on non- spread spectrum (SS) system, this study is based on frequency hopping spread spectrum (FHSS) and the retransmission mechanism. The analysis results show that the normalized transport capacity decreases as , when the total available frequency band is divided into M sub-bands for frequency hopping and the nodes are randomly distributed in space according to a Poisson point process with intensity . In this work, the best transmission range per hop to get the maximum capacity is also derived. Besides, the results summarize how the capacity of FH wireless multihop networks is affected by the outage probability, target signal to interference plus noise ratio (SINR) and other system parameters.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60298-8
摘要 ( 2141 ) PDF (426 KB)( 403 )
As a novel application technology, wireless video sensor networks become the current research focus, especially on target tracking and surveillance scenario. Based on multiple agents’ technique, this article introduces a series of intelligent algorithms such as simulated annealing algorithm (SA), genetic algorithm (GA), and ant colony optimization algorithm (ACO) or their mixed algorithms, to resolve the optimization of tasks schedule and data transmission. This article analyzes the performance of abovementioned algorithms and verifies their feasibility associated with agents. The simulations demonstrates that the mixed algorithms based on SA and GA obtain the optimal solution to tasks schedule, and those combined with SA-ACO show advantages on multimedia sensor networks routing optimization.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60293-9
摘要 ( 1917 ) PDF (172 KB)( 436 )
Dynamical running coding was previously proposed as a method for construction of steganographic schemes in digital steganography. In this article, a new approach of fast coding is proposed to improve steganographic efficiency. Original embedding method is discussed in two cases of constructing different generating matrix; however, the proposed method generalizes the problem to only one case by changing the construction method from the original method. Therefore, the complexity of the proposed method is less than the original method. Meanwhile, both theoretical analysis and experiment results show better performance in terms of distortions and alterations of the cover objects when embedding the same amount of information data bits, which proves a better resistance against steganalysis.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60294-0
摘要 ( 2867 ) PDF (209 KB)( 426 )
Distributed architecture is often adopted for the intrusion-tolerance system currently. However, this distributed intrusion- tolerance system has a consensus problem. To solve this problem, this article explores a distributed intrusion-tolerance system of hybrid time model based on trusted timely computing base (TTCB) and implement an atomic multicast protocol using TTCB services. The TTCB is a trust secure real-time component inside the server, with a well defined interface and separated from the operation system. It is in the synchronous communication environment, while the application layer in the server works asynchronously. By the atomic multicast protocol, it can be achieved that when the servers are over twice the number of faulty servers, the consensus can be satisfied. The performance evaluations show that the proposed protocol can yield larger good throughput with a lower unavailability.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60295-2
摘要 ( 2993 ) PDF (458 KB)( 1057 )
Information hiding techniques adopted in secret communication should meet the requirements of high hiding capacity, real-time and high robustness. For the purpose of real-time speech secure communication, an information hiding algorithm based on the analysis-by-synthesis (ABS) speech coding scheme is presented in this article. This algorithm substitutes secret speech data bits for linear predictive coefficients (LPCs) in linear predictive coding (LPC). Statistics show that the change of voiced signal track is slow and the codebook for LPCs vector is large in ABS coding scheme. Therefore, a new concept, filter similarity, is proposed to determine the LPC parameters for substituting with secret speech information, and to generate multi-codebook for saving storage space to store secret speech information. To achieve the best effects of information hiding, a dynamic threshold is built to make an optimal trade-off among hiding-capacity, security, robustness, transparence and real time. Experiments show that the proposed approach meets the requirements of information hiding and secret communication speech quality. The test results indicate that this approach reaches high hiding capacity with an excellent speech quality and complicating speakers’ recognition.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60296-4
摘要 ( 2018 ) PDF (165 KB)( 416 )
Data discretization contributes much to the induction of classification rules or trees by machine learning methods. The rough set theory is a valid tool for discretizing continuous information systems. Herein, a new method is proposed to improve those typical rough set based heuristic algorithms for data discretization, by utilizing decision information to reduce the scales of candidate cuts, and by more reasonably measuring cut significance with a new conception of cut selection probability. Simulations demonstrate that compared with other typical discretization algorithms based on the rough set theory, the proposed method is more capable and valid to discretize continuous information systems. It can effectively improve the predictive accuracies of information systems while still conceptually keeping their consistency.
中国邮电高校学报(英文版), 2009, 16 (6). doi： 10.1016/S1005-8885(08)60297-6
摘要 ( 2378 ) PDF (229 KB)( 483 )
Massively multiplayer online role-playing game (MMORPG) is one of the fastest-growing segments of the online game industry. MMORPG subscription refers to game accounts logged in during a certain period of time. MMORPG user mobility explains the dynamics of subscriber size change. This article explores the subscription characteristics and user mobility in different types of MMORPGs. It is found that subscription characteristics in different types of MMORPGs are marked by dissimilarity. On one hand, the curve of competition-based game subscription is linear, and the stability period is short, therefore it is necessary for the game operators to introduce new versions timely. On the other hand, the gradient rate of subscription in the community-based game is slow at first and then fast, and the stability period is long, hence it will take the game operator a long cycle to launch a new version. The difference of subscription curve is caused by the fact that user mobility in competition-based game is higher than in the community-based game, as attractiveness of community-based game can maintain a longer period due to network externality. The purpose of the study is to help the game operator to understand the development stage and features of the game and to make effective decisions to attract more players.