Showing papers by "Jiandong Li published in 2005"

Relative degree adaptive flooding broadcast algorithm for ad hoc networks

Abstract: Broadcasting has been widely used in mobile Ad hoc networks as a communication means to disseminate information to all reachable nodes. Because radio signals are likely to overlap with others in a geographical area, straightforward broadcasting by flooding becomes very costly and results in serious redundancy, contention and collision, to which we refer as the broadcast storm problem. In this paper we propose the Relative Degree Adaptive flooding Broadcast (RDAB) algorithm for Ad hoc networks to efficiently reduce the broadcast overhead in the network. Based on the current situation of the network and the degree of the nodes, RDAB calculates the relative degree of the nodes, decides which nodes need to re-transmit and which nodes only need to receive. The higher the neighbor node's relative degree, the more uncovered nodes it can cover, hence these nodes can be selected to re-transmit broadcasting packets in the networks. We analyze the reliability and the validity of the RDAB algorithm to prove that the RDAB algorithm is a valid flooding broadcast algorithm. Simulation results show that the RDAB strategy outperforms the Ordinary Flooding Broadcast Method (OBM) and the Multipoint Relaying (MPR) protocol for Ad hoc networks.

Modulation and demodulation method for continuous phase signals

Abstract: Being adopted for modulation method in the invention, waveform storing quadrature modulation includes steps: decomposing Phase Phi(t, Alpha) to Thetan and Theta (t, Alpha); building a corresponding look up table, storing their sine value and cosine value; through look up table to obtain sine value and cosine value of Thetan and Theta (t, Alpha); then through difference operation to obtain baseband signal. Being adopted for demodulation method in the invention, simplified noncoherent viterbi algorithm simplifies state of CPM signal as Sigman'; receiver processes the intermediate frequency signal to obtain complex baseband signal GammaB (t); the baseband signal multiplied by a delayed and shifted signal obtains baseband differential signal; according to grid chart, calculating branch measure of each state Sigma n+1'; then estimating not simplified ML state Sigma' n+1 (Sigma' n+1), and tracing back to output code element. Features are: easy of calculation and implementation and robustness.

Digital modulation identification by wavelet analysis

Abstract: There is a need to determine the modulation type of an incoming signal. This paper proposes the use of the wavelet transform (WT) for modulation identification of digital signals without requiring any priori knowledge. The identifier consists of inter-class and intra-class identification. Different features have been used for different signals to increase the number of identification types and improve the processing rate. The performance of correct identification is increased too.

An algorithm for discovering physical topology in single subnet IP networks

Abstract: In this paper, we present a novel algorithm for discovering physical topology in heterogeneous (i.e. multi-vendor) single subnet IP networks. Our algorithm is based on standard SNMP MIB information that is widely supported by modern IP network elements. Algorithm resorts to the port's traffic when AFT information is insufficient. Simulation and analysis results show that this algorithm can discover the physical network topology accurately even if SNMP is not supported by some network elements.

Cost-efficient QoS routing protocol for mobile ad hoc networks

Abstract: A novel CEQRP (cost-efficient QoS routing protocol) for mobile ad hoc networks (MANETs) is proposed. CEQRP can provide QoS guarantee and is aimed at extending the battery's lifetime at each host by selecting the hosts with a long battery's remaining lifetime to forward packets. Simulation results show that CEQRP has good network performance. Furthermore, CEQRP shows distinct performance advantages in using a host's electric energy efficiently.

Digital Modulation Identification Based on Software Radio Platform

Abstract: This paper presents a modulation identification system based on software radio platform. The signals have been conveyed to baseband by frequency conversion. Only three features have been chosen, which are kurtosis of the envelope, variance of phase histogram differential coefficients and valid area of power spectrum density. A fuzzy classifier is used for identification. It is proved by the results that the system performs well with a high percentage of correct identification.

A novel power control algorithm and MAC protocol for CDMA-based mobile ad hoc network

Abstract: A single busy tone code-division-multiple-access (SBT-CDMA) protocol for mobile ad hoc network (MANET) is proposed. The RTS/CTS handshake mechanism, busy tone and power control are integrated with CDMA to improve the network performance. The RTS/CTS dialogue is used for the CDMA-code allocation and exchange of the power control information. Based on the difference between the calculation value and measurement value of the received busy tone power, a node can ascertain whether could initialize a RTS packet transmission. Based on the estimation of the channel gain, the transmission power of a data packet sender can be controlled exactly not only to improve the anti-MAI (multiple access interference) ability of the desired receiver, but also to reduce the interference on the undesired receivers around the sender. Simulation results show that SBT-CDMA can significantly reduce the packet collision and increase the channel utilization with lower energy consumption

Effect of mobility on the critical transmitting range for connectivity in wireless ad hoc networks

Abstract: The effect of mobility on the critical transmitting range in wireless ad hoc networks is discussed in this paper. A new parameter, pause probability P/sub pause/, which is the function of the minimum velocity V/sub min/, the maximum velocity V/sub max/ and the pause time t/sub pause/ of random waypoint (RWP) mobility model, is defined. Simulation results show that the effect of RWP parameter on the critical transmitting range is determined by P/sub pause/ that is, if P/sub pause/ smaller than 0.5, the critical transmitting range of mobile network is about 10 percent larger than that of stationary one, else it equals that of stationary network approximately. If the values of t/sub pause/, V/sub min/ and V/sub max/ are given, their effect on the critical transmitting range is determined since P/sub pause/ is the function of them.

QoS-oriented hybrid admission control in IEEE 802.11 WLAN

Abstract: A new QoS (quality of services)-oriented hybrid admission control (QHAC) scheme in IEEE 802.11 WLAN is proposed, in which the influence of the mobile station with slow speed on other stations is decreased by limiting its inter-request time. In addition, end-to-end performance metrics are also measured and applied to make a decision to admission control of new request. Simulation results show that QHAC scheme can efficiently improve the performance of IEEE 802.11 WLAN.

Hybrid splitting algorithm for wireless MAC

Abstract: Collision resolution using splitting algorithm is an effective strategy to improve the performance of Medium Access Control (MAC) protocol. In this letter, a novel splitting algorithm, Hybrid Splitting Algorithm (HSA) for wireless MAC, has been presented. The splitting procedure of HSA has related with both the generation time and the generation interval of the colliding packets. The maximum stable throughput of HSA is up to 0.51. As illustrated from the simulation results using both Poisson and Heavy Tail distributed traffic, HSA outperforms binary-tree and FCFS Splitting Algorithm.

Performance evaluation of access delay of efficient media access schemes for WLAN with smart antenna

Abstract: The use of smart antennas in extending coverage range and capacity of wireless LANs dictates the employment of novel media access control (MAC) schemes, with which the access point (AP) provides access to users by learning their spatial signatures. This paper puts forward an exact approach to analyze the performance of the schemes in terms of required time so that the AP becomes aware of user locations and grants access to the system. The numerical results show that the scheme which distinguishes the users residing in or out of broadcasting coverage range of the AP can provide rapider media access. In addition, the simulation results verify the theoretical approach.

An enhanced User-dependent Perfect-scheduling Multiple Access protocol for wireless packet network

Abstract: Based on the effective contention access and perfect scheduling transmission, an enhanced multiple access protocol - UPMA++ protocol is proposed, which integrates the advantages of random multiple access and fixed allocation multiple access protocols. It allocates the resource dynamically according to the factual traffic requirement, thus reducing the source waste. This protocol adjusts the length of contention access period and polling period effectively to resolve the conflicts between active stations and transmission stations, which active station expects to access the channel quickly and transmission station wants to transmit packet as soon as possible. By analysis, the optimal contention access period length for the given max polling period length is found, and the performance evaluations show UPMA++ protocol has a high throughput (up to 96%), low average message delay and small average message dropping probability.

Adaptive QoS-guarantee multiple access protocol in multimedia wireless network

Abstract: Integrating the advantages of random multiple access and designated allocation multiple access protocols, a novel multiple access protocol supporting quality of service (QoS) Traffic-dependent Perfect­ scheduling Multiple Access (TPMA) protocol is presented. Which dynamically allocates the resource according to the traffic requirement. It makes stations access channel discriminatively and arranges high priority packets to be transmitted without collision as soon as possible. Therefore, TPMA provides QoS supporting for various traffic and improves the performance of the network.

A RS-SISO algorithm for serially concatenated continuous phase modulation

Abstract: The complexity of the soft input soft output (SISO) algorithm is a major concern for iterative detection in serially concatenated continuous phase modulation (SCCPM). In this paper, a reduced state SISO (RS-SISO) algorithm is presented based on the idea of reduced state sequence detection (RSSD). Error events analysis of SCCPM is given. Theoretic analysis and simulation results show that the proposed algorithm provides both significant complexity reduction and little performance degradation compared with the optimal full state SISO algorithm.

A reduced iterative decoder for power and bandwidth efficient serially concatenated continuous phase modulation

Abstract: A reduced iterative decoder for power and bandwidth efficient serially concatenated continuous phase modulation (SCCPM) based on state fusing is proposed in this paper. The proposed algorithm is based on reduced state sequence detection (RSSD) used for CPM and applied to the inner CPM with finite state machine (FSM) structure. System design criterion and performance analysis are listed. Simulation results for binary 3RC signal with h = 1/2 and quaternary 3RC signal with h = 1/2 show that quaternary system provides better performance at the equivalent normalized double-sided bandwidth. The reduced iterative decoder of inner CPM with 4 states for binary 3RC CPM with h = 1/2 is degraded by at most 0.2 dB with respect to its optimal 8 state decoder; the reduced iterative decoder of inner CPM with 16 states for quaternary 3RC CPM with h = 1/2 is degraded by at most 0.5 dB with respect to its optimal 32 state decoder.

WPDM system based on FSE and ML algorithm for multipath fading channel

Abstract: In this paper, a novel wavelet packet division multiplexing (WPDM) system based on Fractionally Spaced Equalizers (FSE) and Maximum Likelihood (ML) algorithm is studied for multipath fading channels. New discrete wavelet packet transform structure based on FSE, which uses Least Mean Square (LMS) algorithm and ML detecting algorithm, are the two novel aspects of the presented system. It is demonstrated by simulation results that the FSE method is superior to the Zero-Forcing equalizers (ZFE) method in performance and the FSE-WPDM scheme can provide greater immunity to multipath fading channels and AWGN than the FSE-OFDM scheme.

A traffic overstock reslove scheme in WLAN

Abstract: A new Multiple Access Control (MAC) protocol—User Adaptive Scheduling Multiple Access (UASMA) protocol is proposed in this paper. It can well schedule the packet transmission according to the exact number of active Mobile Terminals (MTs) determined by self-organizing algorithm and adjust the number of packets sent by one node in one frame properly. UASMA protocol employs a special frame structure, which makes it possible to allocate channel resource to uplink and downlink traffic according to their respective service requirements. The proposed concept of referenced-frame-length can ensure the frame length varies in a certain range, and consequently increase the utilization efficiency of the channel greatly. Meanwhile, UASMA protocol uses an efficient collision resolution algorithm to guarantee that active MTs can access the channel rapidly. Finally, the performance of UASMA protocol is evaluated by simulation and it is also compared with carrier sense multiple access, rounding-poll and UPMA protocols. The results show that the UASMA has better performance than others.

A novel integer frequency offset estimator for OFDM

Abstract: One of the principal disadvantages of Orthogonal Frequency Division Multiplexing (OFDM) is very sensitive to carrier frequency offset. The integer frequency offset has no effect on the orthogonality among the subcarriers, but it causes a circular shift and phase rotation of the received data symbols sequence, resulting in a Bit Error Rate(BER) of 0.5. In this paper, a novel integer frequency offset estimator for OFDM is derived based on maximum likelihood estimation technique and exploration of the differential relation between two consecutive OFDM data symbol sequences in frequency domain. Its performance is compared with the conventional method by computer simulations for the additive white Gaussian noise channel and a multipath fading channel. Simulation results show that the performance of the proposed estimator is better than the conventional estimator.

Access delay of efficient media access schemes for wireless LAN with smart antenna

Abstract: An exact approach to analyze the access delay of the media access schemes that employ beamforming to locate users out of the broadcast range of the access point (AP) in a WLAN is put forward. Results show that the scheme which distinguishes the users residing in or out of broadcast range of the AP can provide rapider media access. And then the simulation verifies the proposed approach.