New Publications are available for Multiple access communication
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New Publications are available now online for this publication.
Please follow the links to view the publication.DRMA-CR: distributed reservation multiple access with consecutive requests for wireless sensor networks
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0592
In wireless sensor networks (WSNs), a medium access control (MAC) protocol should be designed to enhance channel throughput, end to end delay, and energy efficiency under the multi-hop communication. This paper proposes a distributed reservation multiple access with consecutive requests (DRMA-CR) as an efficient MAC protocol to comply with these design requirements. This scheme reduces channel access overhead by successively delivering data via the path reservation using consecutive request strategy on the multi-hop path. In addition, it efficiently allocates channel resources to all nodes on the reserved path according to the expected interference range. Also, it enables automatic time synchronisation among nodes based on the time information carried in control packets. Furthermore, it emphasizes energy efficiency by following a repeated duty cycle with active and inactive operations during idle period, and by performing an inactive operation during unrelated data transmission period. In simulation, DRMA-CR shows superior performance in channel throughput, end to end delay and energy efficiency than CSMA/CA with a small or large interference ranges. (5 pages)A dynamic resource allocation model along with adaptive power control in a multi-rate direct sequence CDMA with MIMO
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0074
A throughput maximization algorithm for a CDMA system comprising of variable bit rate (VBR) groups has been proposed. The algorithm is aimed at efficiently utilizing the radio resources for maximal throughput while meeting the minimum data transmission rate and Quality of Service (QoS) requirements of each user group. The power of each group is also dynamically controlled so as to minimize the cell interference thereby maximizing the system capacity. The model also predicts the reduction in effective cell radius because of cell breathing under Gaussian noise and a Rayleigh faded channel. The simulation of multiple input multiple output (MIMO) antenna in such a system reports an improvement in the Bit Error Rate (BER) performance of the system by up to 80%. The allocation scheme efficiently utilizes as much as 99.9% of the available bandwidth in the system.An adaptive method utilizing channel reciprocity in TDD-LTE system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0799
In a time-division-duplex (TDD) system the channel state information (CSI) can be obtained at the transmitter side due to channel reciprocity and it can be used to increase the spectral efficiency of a multiple-input multiple-output (MIMO) system. However, the frame architecture, system parameters, pilot architecture, the moving speed of UE and the interference structure affect the channel reciprocity. The transmission parameters assigned based on the reverse link measurements may lead to excessively high frame error rates, if the channel reciprocity doesn't exist or interference structure between transmission directions differs significantly. In this paper, an adaptive method of TDD-LTE system is studied. This method analyzes the above factors to propose a criterion of judging the channel reciprocity, compensates asymmetric interference, and then utilize balance of channel reciprocity and feedback. Analysis and simulation results show the proposed scheme can compensate the asymmetric interference, make using the channel reciprocity possible, reduce the feedback load and demonstrate better system performance.A hybrid TDMA protocol for ad hoc networks
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0694
This paper presents the detailed design scheme under OPNET simulation environment about how to implement HTDMA (Hybrid TDMA), a collision-avoid and dynamic slots assignment algorithm. HTDMA is free of "hidden terminal" and "exposed terminal". In OPNET simulation software, MANET (Mobile Ad Hoc Networks) node model are defined with MAC layer using IEEE802.11 protocol, so replace it with HTDMA easily. We compare HTDMA with IEEE802.11 through simulation. The simulation results show that HTDMA outperforms IEEE802.il in terms of end-to-end delay and packet delivery radio. Some future work and improvement are also discussed.Dynamic sectorisation based on genetic algorithms for OFDMA networks
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0681
OFDMA is the multiple access technique proposed for future communication systems. With growing demands for high data rates radio resource management is an important aspect for OFDMA systems. Sectorisation is one such radio resource management technique that has been proposed as an efficient scheme to improve system performance for GSM, CDMA and OFDMA systems. In this paper, a dynamic sectorisation method based on using a Genetic Algorithm (GA) for OFDMA networks is designed and verified by simulation. The algorithm proposed in this paper can give up to 50% enhancement of system throughput in OFDMA networks for heavily loaded and unbalanced traffic scenarios.Interference mitigation for downlink base station cooperation with joint distributed space-time coding
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0875
Capacity of a cellular system on the downlink is significantly limited by inter-cell interference (ICI), especially at the cell boundary. Multicell joint processing can mitigate inter-cell interference and thereby increase the spectral efficiency of cellular systems. In this paper, a joint distributed space-time coding (J-DSTC) and an inner J-DSTC base station cooperation scheme with precoding are proposed to remove the significant ICI experienced by the cell boundary users. Simulation results show that the proposed scheme can effectively suppress the inter-cell interference, and achieve more diversity gain compared to that without cooperation and is more spectrally efficient than that of no cooperation and BSs transmitting in a time-division multiple access manner to avoid ICI at the cell edge, while retains a comparatively low structural and computational complexity.Research on the 3G mobile network optimization
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0703
Based on the actual operation of the system and QoS status, the 3G mobile network optimization consists of system dynamic testing, analysis and adjustment to the existing system configuration to provide the highest QoS, the optimum coverage and the lowest network cost-effective. Capacity planning and pilot pollution are two of the key issues in CDMA network optimization. By coverage optimization, power control, access control, network capacity can be improved. And eliminating RF pollution by parameters adjustment can furtherly improve performance of CDMA network.WCDMA ratio network optimization approach based on measurement report
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0695
In this paper, a measurement report based and active network optimization approach is introduced. It differs from the conventional method that solving the problems based on customer complaints which is passive. By extracting and analyzing the relevant information from the measurement reports generated by the network within a continuous period of time, some common problems existing in the wireless network can be detected and located quickly and actually. Then network maintenance personnel can take specific measures to solve the corresponding problem which could improve the network quality of service Besides, a common method to decode the measurement report comply with 3GPP specification is also introduced.An improved backoff algorithm with node access fairness in WLAN
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0958
Distributed coordination function (DCF) is the most widely deployed medium access control (MAC) protocol for IEEE 802.11 Wireless Local Area Networks (WLANs). The carrier sense multiple access with collision avoidance (CSMA/CA) scheme which employs a binary exponential backoff (BEB) algorithm is used to reduce the collision probability. In this paper, we propose an improved collision backoff algorithm considering the node access fairness. In NAFB, different stations, including sending stations and non-sending stations, adopt different contention window adjustment strategies according to the sensed collision situations. Simulation results showed that the proposed algorithm not only ensures the fairness of node access in the network, but also improves the performance in terms of the network throughput, packet loss rate and average packet delay to some extent.System performance analysis of OFDMA based femtocell networks
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0700
OFDMA femtocells have been proposed as a viable solution not only to deal with the explosive growth of traffic but also to increase energy efficiency of cellular network. However, the system performance of the two-layer femtocell networks is quite different from macrocell networks.In this paper, we first analyze the performance of hierarchical network in terms of system capacity and energy efficiency, especially in the case of introducing sleep mode according to variant network load. Then, we evaluate the users' quality of service (QoS) under different factors, including the distance between macro base station (MBS) and femto base station (FBS), user location, FBS transmission (Tx) power and deployment density. The simulation results show that system capacity and energy efficiency can be improved significantly after FBS deployment and various kinds of factors have effects on users' QoS to different degrees. Our research results provide useful guidelines for the deployment of OFDMA femtocell networks.Marginal utility-based power coordination in OFDMA downlink
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0798
In this paper, we address the intercell interference (ICI) in multi-cell networks by dynamically sharing the spectrum through collaboration between base stations. Throughput marginal utility (TMU) is utilized in resource allocation, and a theoretic framework based on TMU optimization is formulated. A distributed power allocation scheme is developed to exploit the average channel statistics of other cells in interference mitigation. The proposed algorithm is shown to substantially outperform conventional schemes.Study of coexistence between UWB and mobile communication system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0699
The objective of the study is to investigate the impact of cumulative interference from multiple UWB systems to the downlink of GSM900, GSM-1800, TD-SCDMA and WCDMA. Since indoor environments are focused on, a three-dimensional geometry for the spatial distribution of the UWB devices is considered. To obtain a realistic scenario, a traffic model describing the transmission activity of the UWB devices is taken into account. In this paper, we use a statistical model, i.e. a probability density function (PDF), describing the cumulative interference from multiple UWB devices. With the model, the maximum interference from multiple UWB devices, the maximum acceptable UWB-device density, the minimum distance between UWB devices and receiver are derived in different link budget degradation.A power optimization algorithm for femtocells to suppress the uplink interference in OFDMA system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0679
Femtocell has been considered by the wireless industry as an effective solution not only to improve indoor coverage, but also to offload traffic from the overburdened macrocell networks. In hybrid macro/femto networks, macrocell may have to share the same frequency resource with femtocells, considering the spectrum availability and network infrastructure cost. Sharing the same spectrum may lead severe interference to macrocell users especially when femtocells are densely deployed. In this paper, a decentralized scheme is proposed for the protection of macrocell users' uplink by reducing femtocell users' transmission power. Simulation results confirm that the proposed method is feasible and effective.Capacity and cell range estimation of mobile WiMAX
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0952
The IEEE802.16 standard which has emerged as Broadband Wireless Access (BWA) technology, promises to deliver high data rate over large areas to a large number of subscribers in the near future. This paper analyzes the cell-range and capacity of downlink of OFDMA -based on the IEEE802.16e mobile WiMAX system with and without overheads. The analysis focuses in particular on the impact of Adaptive Modulation and Coding (AMC) as well as deriving an algorithm to determine the maximum numbers of subscribers that each specific WiMAX sector may support. An analytical study of the WiMAX propagation channel by using Cost-231 Hata Model is presented. Numerical results and discussion highlight the effect of overheads over the WiMAX system capacity by using Matlab to simulate the algorithm for different multi-users parameters.Study on different implementations of UWB wireless communication system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0961
The technology of ultra-wideband (UWB) has been widely used for its advantages about high transfer rate, large capacity, low cost, low-power etc. There are three kinds of implementation technologies: impulse radio (IR), Direct Sequence Code Division Multiple Access (DS-CDMA) and multiband orthogonal frequency division multiplexing (MB- OFDM). In this paper, features and solutions of UWB system are demonstrated and comparative study on these implementations are presented.Soft rake and DFE based IDMA systems for underwater acoustic channels
http://dl-live.theiet.org/content/conferences/10.1049/ic.2010.0231
Two single-element downlink interleave division multiple access (IDMA) based receivers employing adaptive decision feedback equalization (DFE) and conventional soft Rake are proposed for multi-user underwater communications channels. The chip-level DFE is optimized using time-multiplexed training based on the mean square error criterion (MSE), which is generated by exchanging soft information with the single-user's channel decoders. In contrast, the soft-Rake IDMA receiver utilizes iterative channel estimation with reconstructed multiple-access interference (MAI) signals and the detection is implemented using parallel interference cancellation (PIC) to remove MAI effects between users. Furthermore, in both receivers, the carrier phase recovery is jointly optimized. The receivers are investigated in short range shallow water acoustic channels using signals acquired during sea-trials in the North Sea. Results for synchronous multi-user scenarios with 2 and 4 users, at an effective rate of 439.5 bps per user for 4 kHz of system bandwidth, demonstrate that the DFE-based IDMA receiver can reduce intersymbol interference (ISI) efficiently while outperforming the standard soft Rake IDMA receiver. (5 pages)Modelling of FBG for encoding/decoding in SAC-OCDMA system
http://dl-live.theiet.org/content/conferences/10.1049/ic.2010.0207
A SAC-OCDMA system is proposed to be used in passive optical networks. Performance of the system depends on the spectral characteristics of the elements used such as optical source, encoding/decoding elements etc. An uniform FBG (UFBG) is proposed to be used for encoding/decoding of the SAC-OCDMA system. UFBG has side lobes in its spectral characteristics. It is characterized by the parameter, effective bandwidth. In this paper a model of UFBG is presented which further can be utilized for performance analysis of SAC- OCDMA system. (4 pages)Performance analysis and comparison of adaptive beam forming algorithms for smart antenna systems
http://dl-live.theiet.org/content/conferences/10.1049/ic.2010.0211
Smart Antenna Systems (SAS) are deployed in wireless communication system to improve the spectrum efficiency, eliminate the multi-access interference, co-channel interference (CCI) and the multi-path fading [1]. This intelligence enables the antenna systems to improve the range, quality and coverage of the system and leads to maximize the system capacity. This is achieved by beam forming algorithms and auto tracking of the desired signals. This uses the transmitted signals from a fixed set of antenna elements in an array which are weighted and combined to form a steering beam that tracks a mobile unit (MU) as it moves. This allows the SAS to dynamically focus radio frequency resources on a particular MU with minimal noise, interference and allied degrading effects. A systematic comparison and performance analysis of algorithms like Recursive Least Squares (RLS), Least Mean Squares (LMS) and Constant Modulus Algorithm (CMA) has been done in this paper. The analysis parameters used for comparison of above algorithms are response towards beam forming, interference rejection, convergence and bit error rate (BER). (5 pages)One scheme of cooperative diversity with two satellites based on the Alamouti code
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0640
Aiming at the low Earth orbiting (LEO) satellite mobile communication, the cooperative diversity technology is applied to the forward downlink in this paper, and one scheme for cooperative diversity with two satellites based on the Alamouti code is presented. To reduce the non-negligible path delay from the different satellite to the same terminal, the synchronous CDMA is used and satellites are distinguished by the spreading codes which are orthogonal each other in this scheme. Simulation results show the satellite cooperative diversity system can obtain better performance than the traditional uncoded BPSK system with the same fading channel and system parameters. Though the satellite cooperative diversity system has worse performance than the traditional satellite diversity system, it has the advantage in communication range and low complex mobile terminal. Particularly, this new scheme can be used as an effective means to improve the performance in the area where the gateway can not be built.UMTS mobile positioning simulator for vehicle location
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0686
In this paper, a tool for simulating UMTS mobile positioning in vehicular environment has been developed. The primary function of this simulator is to locate the UMTS mobile in realistic propagation environments. This tool first models the network configuration and radio propagation in a vehicular scenario. Based on the system level model, it then simulates the pilot signal transmitted by a base station to a mobile station through the 3GPP WCDMA FDD downlink. The received pilots at mobile station are processed to obtain the time-difference-of-arrival estimates which are used to construct the hyperbolic equations for mobile position calculation. The simulator has been implemented in the Matlab and Simulink environment.Performance analysis of multi-hop free space optical communications with pointing errors
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.1208
This paper investigates the performance of multi-hop free space optical (FSO) communications with pointing errors. A statistical model for the optical intensity fluctuation at the receiver due to the combined effects of atmospheric turbulence-induced fading, misalignment fading and pass-loss is presented. For given weather and misalignment conditions, a close-form analytical expression for the end-to-end outage probability of serial decode-and-forward (DF) multi-hop FSO communication is derived. Numerical results show that the serial DF multi-hop transmission is a promising technology to increase the performance of FSO communications. Moreover, the derived analytical expression can provide very well approximations to the simulation results.Performance of the buffer queue with priority for dynamic spectrum access
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0731
In this paper, we propose a new Dynamic Spectrum Access (DSA) scheme which employs a buffer queue with priority. Two coexist systems: primary system and secondary system are introduced, which share the same bandwidth. When all the bands are busy, the newly coming secondary user (SU) is inserted into the buffer queue according to the user's priority. The average waiting time and the average queue length of this model are studied. The simulation results indicate that our model can obtain a good tradeoff between average waiting time and interrupted probability. It may reduce the average waiting time of the higher priority user, also, although the average waiting time of the lower priority user increases, their interrupted probability reduces.Improved iterative water-filling algorithm in MU-MIMO system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0645
In this paper, an efficient user selection method for traditional iterative Water-Filling algorithm in Gaussian multiuser broadcast channel is developed to reduce the computational complexity. The new algorithm selects some effective users from all the users, and then allocates the entire power among the selected users applying Water-Filling algorithm. The vector Gaussian broadcast channel and the matrix Gaussian broadcast channel are considered respectively and the corresponding user selection methods are proposed. Theoretical analysis and simulation results show that the new algorithm can significantly improve the computational efficiency of the traditional iterative Water-Filling power allocation and can obtain almost the optimal sum capacity.Research on multi-rate quasi-synchronous coherent time-spreading OCDMA system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.1172
We propose a novel scheme of multi-rate quasi-synchronous coherent time-spreading OCDMA system, employing orthogonal variable spreading factor (OVSF) codes with a zero-correlation zone. Within permissible time delay, multiple-access interference and beat noise can be removed in multi-rate quasi-synchronous coherent time-spreading OCDMA system, and the near-far problem can also be eliminated. Simulation of eight simultaneous users with 1.25 Gbit/s and 0.625 Gbit/s is demonstrated, where the fiber link consists of 20 km single-mode fiber, plus 2 km Dispersion Compensating Fiber.A new optical code translation scheme for multi-hop network and simulation of multi-user asynchronous OCDMA system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.1184
Transparent optical code (OC) translator is an indispensable component to realize multi-hop and code-reuse in optical code division multiple access (OCDMA) as well as OC-label based optical packet switching (OPS) networks. In this paper, we propose a scheme for transparent OC translation based on superstructured fiber Bragg gratings (SSFBGs), and present the simulation result of 10 Gb/s 7-hop transmission by utilizing such OC translators. We also implement the simulation experiment of 8-user 5 Gb/s asynchronous OCDMA network and obtain decoded signals with distinct autocorrelation peak at matched receivers.Some considerations for interference suppression in multi-band frequency hopping UWB communications
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0612
Some considerations for interference suppression technologies in multi-band frequency hopping ultra-wideband communications are made. Based on this communication system, the novel coexisting interference detection algorithm is proposed in this paper. This new algorithm can be realized in low complexity and in comparatively low level sampling rate. With the estimation parameters provided by the new interference detection algorithm, the frequency hopping code generator can control code map to avoid the coexisting interference to other wireless victim in the same band. The mathematic analysis and computer simulation for this new algorithm are made. The simulation results show that the new algorithm can detect the coexisting interference effectively in low sampling rate. MB-FH UWB communication system can improve interference suppression performance evidently using this new interference detection algorithm combined with interference suppression measures.Performance comparison of LDPC-coded IDMA system with equal spreading and unequal spreading
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0634
A scheme of applying unequal spreading to LDPCCoded IDMA system was proposed. The issue of LDPC-Coded DDMA system with equal spreading and unequal spreading was studied. Gaussian approximation was applied to the messages probability density distribution function between nodes on factor graph of LDPC-Coded spreading system. We compare two cases, the first is optimization of LDPC with fixed spreading factor, and the second is joint optimization of LDPC and spreading degree. By means of iteration and applying the method of differential evolution we obtained degree profiles in the case of 8 users with equal spreading and unequal spreading on condition that the system spectral efficiency is the same. We constructed the check matrix randomly based on the optimized degree profiles and made simulations. It has shown that the performance of LDPC-Coded spreading IDMA system cannot be improved by joint optimization of LDPC code and spreading degree for AWGN Multiple Access Channel (MAC) from the perspective of approaching MAC channel capacity. The result gives us guidance in designing LDPC-Coded IDMA spreading system.Multi-user capacity of M-PPM UWB system using PSWF pulses
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0625
The information capacity model of M-ary PPM ultra-wideband communications is built over multiple-access and additive white Gaussian noise channel. The model extends the known capacity of PPM orthogonal pulses to incorporate specific UWB constraints. Based on Gaussian approximation for the multiple access interference, an expression of the UWB capacity is developed as a function of system parameter. The channel capacity of UWB communications using PSWF pulses subject to FCC spectral masks is computed, and the results is compared with that of 5<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">th</sup> and 7<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">th</sup> order Gauss pulse. The simulation results show that the UWB system with the PSWF pulses has more channel capacity than the system with Gaussian pulse. This conclusion presents a new view for the UWB pulse choice, which can facilitate system designers to improve the efficiency of UWB communications.A cognitive spatial multiplexing scheme for MIMOCDMA networks
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0639
The existing cognitive schemes have not considered cognitive spatial multiplexing (CSM) for MIMO-CDMA network, there are three vital problems to hinder CSM's application: spatial channels' estimation for mobile stations(MSs), space-time coding and decoding for base station (BS) and MSs, the implementation complexity of BS and MSs. To solve the problems, a simplified cognitive spatial multiplexing scheme is proposed, including BS and MS systems, where MIMO BS in a cell has two antennas and each MS of lower moving speed has one antenna only. To ensure communication quality of the network, the scheme applies LDPC as the channel coding instead of space-time coding for BSs and MSs. BS assigns the same CDMA channels for MSs to have larger space interval. Simulations show that good spatial multiplexing capacity and BER performance have been achieved by the proposed scheme.Bandwidth-satisfied QoS multicast routing in TDMA-based mobile ad hoc networks
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0807
The need for supporting real time multimedia applications for users of Mobile Ad hoc Network (MANET) is becoming essential. The aim of this paper is to construct bandwidth-satisfied multicast tree for QoS routing in TDMA-based mobile ad hoc networks. The paper proposes an efficient path bandwidth calculation algorithm. An effective multicasting routing algorithm is presented to build a multicast tree among all the multicast members. Simulation results show that compared with MAODV, our proposed QoS routing algorithm can significantly improve the performance of QoS multicast routing in MANETs in terms of success ratio and average delay.Resource allocation for OFDMA-based cognitive radio systems with minimum rate constraints
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0659
In this paper, we study the resource allocation problem for real-time services in OFDMA-based cognitive radio (CR) systems. A novel resource allocation algorithm is proposed to maximize the sum-rate of all CR users while keeping the interference introduced to the primary user (PU) under a specified threshold and at the same time to meet the constant transmission rate for each CR user to guarantee the real-time service. In contrast to classical resource allocation algorithms, the proposed algorithm can achieve higher transmission rate and guarantee each CR user's target transmission rate.GRDT: group-based reliable data transport in wireless body area sensor networks
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.1084
Recent technological advances in sensors, low-power microelectronics and miniaturization, and wireless communications have promoted the research and development of wireless body area sensor networks (WBASN), which has gained a lot of attention from researchers for its promising application in medical care and health care field. Reliable data transmission, which means that data is timely transmitted to the sink node without loss, is one of the key points to a successful application of WBASN. In this paper, we proposed a Group-based Reliable Data Transport (GRDT) protocol, which can be used in WBASN for periodical data acquisition. GRDT protocol adopts TDMA (Time Division Multiple Access) and FDMA (Frequency Division Multiple Access) schemes to control channel access, which can avoid the emergence of congestion and tremendously improve the network throughput. Moreover, GRDT protocol provides block feedback message scheme instead of synchronous ACK for hop-by-hop loss recovery mechanism, which will significantly reduce transmission delay and improve the packets reception rate. In addition, GRDT provides mobility and scalability support. Experimental and simulation results show that GRDT protocol can provide more than 99% reliability and the network throughput is up to 111 kbps (with 100 sensor nodes and 5 router nodes).Fast iterative user selection for multiuser MIMO system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0641
In a downlink multiuser multi-input multi-output (MU-MIMO) communication system, a base station (BS) transmits to multiple mobile stations (MS) simultaneously over the same frequency band, thereby greatly increasing the channel capacity. However, in previous works, the multiuser spatial multiplexing system has no special strategies for selecting the multiuser channel. Although the exhaustive search algorithm can achieve optimal performance, its cost is large. In this paper, we propose a suboptimal user selection algorithm for the MU-MIMO system to save hardware resources and serve more users. The proposed selecting criterion bases on maximum total throughput by selecting the best channel of user. To reduce the complexity further more, we give out an iterative selection scheme. Compared with the optimal algorithm, the proposed algorithm achieves good sum capacity performance, has lower complexity, and is suitable for practical communication system. Simulation results show the performance of the proposed scheme.Enhancing the performance of IDMA system by irregular LDPC codes
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0631
A method to enhance the performance of IDMA system by means of irregular LDPC codes was studied. Interleavers were used as signature character for user identification and iterative turbo detection and decoding approach was employed with reduced complexity. Gaussian approximation was applied to approximate the message probability density function on factor graph with multiple users. Iterative message update formulas on factor graph were derived. Degree profiles were obtained by using the iterative formula. Simulation result shows that the performance of irregular LDPC-Coded LDMA system is better than that of (3,6) regular LDPC-Coded IDMA system in terms of BER and performance gain about 0.6 dB is achieved at BER 10s with 8 users for AWGN multiple access channel.Monitoring and control of terrestrial pipe cathode protection system based on wireless sensor network
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.1018
Cathode protection is often used to slow down the corrosion of terrestrial pipe. This paper aims to design and develop a system to monitor the terrestrial pipe cathode protection equipments, which can not only collect the potential information in time, but also fine-tune the guard mode of cathode protection on demand. This system integrates technology of wireless sensor networks and GPRS to collect potential data and realize remote data transmission. Mechanisms are adopted to effectively lower the energy assumption and to ensure reliability, such as work-on-duty, allowing for power saving in selection of hardware components, and using TDMA protocol to avoid collision. Trial running of the system has published good results with 96% or higher success ratio of data transmission and low power saving. In all, this system can meet the requirements of timely detecting physical exception of terrestrial pipeline and controlling wireless sensor networks on demand.CSMA/CA-based MAC protocol in cognitive radio network
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0643
Different from the MAC of IEEE 802.11, the application of IEEE 802.22 suffers the uncertain spectrum and frequency width, which can not ensure the access of mobile users to be valid. To solve the problem, in this paper, we modify the CSMA/CA mechanism in order to make it suit the Cognitive Radio environments, in which the spectrum can be effectively used. We validate the modification by numerical analysis.Performance evaluation of a 16-PSK trellis-coded DS-CDMA system utilized for a satellite to airplane/train link
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1235
The symbol-to-symbol error performance evaluation of a 16-PSK A/DS-CDMA coded satellite-to-airplane/train data link is treated, motivated by recent DVB-S2 similar communication experimentations by the TDP#5 payload onboard the AlphaSat platform. A Fourier-Bessel series based analysis utilizing the characteristic function (CF) expression of the overall disturbance vector is employed to model the simultaneous presence of strong fading and impulsive noise disturbances and strong Doppler frequency shifts. Obtained in quasi-real time simulation results show that the involvement of the trellis codes being constructed over the spreading sequences set leads into significant improvement of the performance of the mobile-to-satellite link. In addition, the presented analysis approach appears to be an attractive solution for concurrent payloads design and adaptive communication platforms, such as software radios. (6 pages)A soft interference cancellation method in OFDMA uplink
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1934
In OFDMA uplink, each user is affected by different frequency offsets, which destroy the orthogonality between subcarriers, introduce inter-carrier interference, and seriously lower the BER performance. So the inter-carrier interference cancellation is indispensable at the receiver. A soft interference cancellation method is proposed in this paper, which combines frequency offsets compensation with channel decoding, and exhibits good convergence performance.The frequency compensation to eliminate ICI in CBTC system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1937
The CBTC system is an advanced train control system which makes use of big-capacity digital communication between wayside and train, to transfer the information of the status of the train, as well as the controlling information. To prevent accidents which cause severe people injure and finance loss, the information reliability to be guaranteed. The metro railway wireless communication channel is complex for multi-path propagation, the receiving signal will suffer strong ISI and communication performance will be severely downgraded. OFDM is able to improve the performance of the wireless communication in CBTC, however, OFDM signals will suffer ICI when they are transmitted in the multipath channel of the CBTC, so how to reduce the ICI of the CBTC system is the main problem at present Firstly, this paper analyzes the multi-path channel of the CBTC, gets the conclusion of ICI caused by multi-path resides in the railway and establishes the model of it. By means of the analysis of the model, we propose the Frequency Compensation method to reduce the ICI of the system. Finally, extensive simulations show that the Frequency Compensation method is able to improve the performance of the system.An auction algorithm for subchannel allocation in OFDMA networks with service differentiation
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.2032
In this paper, we proposed an auction algorithm for the subchannel allocation in OFDMA cellular networks. This algorithm allows users to fairly compete for the using of the subchannel through a new bidding strategy. The bidding price is according to the difference between the logarithmic function of the data rate given by the subchannel at present slot and the long term average data rate. We introduce the active index to adjust the two parts contributing proportion to the bidding price and reveal the user's different willingness to pay for different services. For each subchannel, the user bid highest will be allocated the subchannel. The auction procedure can realize a competitive fairness from the perspective of the users. Numerical result shows that the proposed algorithm achieves different degrees of tradeoff between the system efficiency and fairness by using different active index set and also can provide differentiated services for different users.A solution for Ethernet-based real-time communication network of distributed numerical control system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1411
To improve the excellent compatibility and high real-time communication of distributed numerical control (DNC) system, this paper presents an Ethernet-based solution on real-time communication for each level of DNC, especially in the motion control level. In this solution, CSMA/CD in Ethernet takes the non-determinism, but for keeping Ethernet's compatibility and other advantages, a real-time control protocol is designed into the protocol stack of MAC and TCP/IP. And according the main features of DNC communication, a real-time control police based on time slot mechanism with CSMA/CD are proposed accordingly to schedule determinism, time-synchronization and short-circle transmission in the DNC control network. The feasibility of the solution has been tested by simulations and experiments. Thus, it provides a reference for real-time communication technologies of advanced manufacturing system. (6 pages)Performance analysis of unsaturated slotted IEEE 802.15.4 medium access layer
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1888
In this paper, we analyze the uplink performance of unsaturated slotted IEEE 802.15.4 medium access layer using the Markov chain model and the theory of M/G/l queues. In our treatment the emphasis is paid to retransmission due to collision of packets, since it plays a very important role in the behavior of the slotted CSMA-CA algorithm. The validity of the proposed model is demonstrated by good agreements between the model results and Network Simulator 2 (ns-2) simulations.Cyclic delay diversity for single carrier FDMA with linear precoding technology
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1967
Cyclic Delay Diversity (CDD) has been considered as an improving way to obtain frequency diversity. Single Carrier FDMA (SC-FDMA) combines the advantages of the OFDMA but with lower Peak to Average Power Ratio (PAPR). In this paper we propose SC-FDMA with CDD system which achieves full diversity without data rate loss. In addition we apply linear precoding to SC-FDMA-CDD system especially in Rayleigh fading channel to further improve the BER performance.Multiuser detection for time synchronous ARGOS signals
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1207
Multiuser detection has recently been a big challenge in the increase of the performance for a satellite communication system. In the previous studies on systems such as CDMA, researchers have derived general mathematical expressions to describe the system model. However, when it comes to specific system such as ARGOS system, solutions based on general expressions may no longer be valid and thus new mathematical derivations could be formulated. In this paper, we propose a new mathematical model for synchronous multiuser communication in ARGOS system and we analyse the performance of the optimum multiuser detector and some sub optimum techniques such as conventional, decorrelator, minimum mean square error, and successive interference cancellation detectors. (5 pages)Performance of smart antenna receivers implemented in different frequencies
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.2030
The performance of directional RAKE receiver (DIRAKE) implemented in radio frequency, intermediate frequency and baseband is investigated as well as the numerical results. The DIRAKE is based on the smart antenna (SA) and traditional RAKE receiver, which results in the separation of signal from space domain. It is shown in the paper that the scheme of intermediate frequency has the highest performance cost, by which the multi-path interference can be restrained. For coherent demodulation unusable in baseband, interference would be amplified, which results in the fluctuation of performance. Though the performance of radio frequency scheme is best, it is too hard to realize in engineering.Tradeoff of channel coding and repetition-code spreading in IDMA systems
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1999
This paper presents a novel tradeoff of channel coding and repetition-code spreading in IDMA systems which is generalized from traditional DS-CDMA systems. With the help of separation result of coding and spreading given by Veeravalli, we solve the coding-spreading tradeoff problem in the way of concatenating channel coding followed by spreading. In particular, we take two kinds of channel coding, i.e. feed-forward convolutional code and turbo code into consideration in this tradeoff problem. A low-complexity soft rake serial interference cancellation-aided turbo-type multiuser detection is utilized over AWGN channels. Theoretical analysis and Monte Carlo simulations both reveal that under a preset bandwidth expansion, the tradeoff problem favours channel coding over repetition-code spreading in enhancing the system spectral efficiency.A method of combating timing jitter in UWB system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.0423
Ultra wideband (UWB) system is sensitive to timing jitter because of the extremely short duration of the pulses it employs. The effects of timing jitter on the performance of UWB system have been studied in many literatures. The results show that relatively modest timing jitter can markedly degrade the system throughput, bit error ratio (BER) performance and multiple-access performance, and it even can disable the correlation receiver in severe condition. So, measures should be taken to mitigate the effects caused by timing jitter. In this paper, a method of combating timing jitter by introducing additional modification to the conventional reference waveform at the receiver that is used to correlate with the received waveform is presented. The mathematical formulae of the additional modification corresponding to normal distribution of timing jitter are derived. The results of simulation show that the method adopting modified correlation template outperforms the method use conventional correlation template in BER performance, especially for the large amount of timing jitter in UWB correlation receiver. (4 pages)Code hopping communications with real-valued direct sequences for anti-interception
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1906
Using real-valued sequences, a new kind of Code Hopping Code Division Multiple Access (CH-CDMA) communication systems is proposed for anti-interception in this paper. With the same sequence period, the real-valued sequence sets are much more than the traditional integer sequence sets, so the codes for hopping are no longer deficient seriously as before, which improves the performance of anti-interception. Moreover, using real-valued sequences with Quasi-Zero Correlation Zone (QZCZ) may eliminate perfectly the Inter-Symbol Interference (ISI) and Multi-Access Interference (MAI) so as to overcome the far-near effect and improve the performance of anti-interference, which makes it convenient to build big-area networks on the war field.Uplink timing synchronization for OFDMA based mobile satellite communications
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1236
One of the problems that faces OFDMA based mobile satellite system is generally timing synchronization between a satellite and users within the beam. In a terrestrial OFDMA system, propagation delays are relatively very small and the differential delays between users within a cell may be considered inconsequential. However, in a satellite OFDMA system, it is not negligible because round trip delay in GEO based system is 250 ms and the differential delays within a beam can be over 10 ms depending on a beam size. Therefore, in this paper, we propose uplink timing synchronization and uplink resource allocation methods for satellite OFDMA or SC-FDMA based communication considering very large differential delay between users within a beam, aiming at the reuse of terrestrial OFDMA based radio interface as a satellite radio interface. The proposed methods can bring latency reduction and throughput increase. (6 pages)The performance of circular SA in CDMA application
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1911
This paper analyzes the performance of circular S A with 8 array elements in different application scenarios. For more code-channels pointing to different directions, according to the combination of the chip data, the directions for the main and side beam-lobes will change suddenly, which is hard to forecast. It is founded that the RAKE receiver couldn't been used to compensate for the effect of multi-path fading, making the instability of system rising suddenly. By which it can be shown that this SA transmission system for multi-directions is only suitable for walking mobile communication system with smaller covering range.