Tan Xuezhi

Dynamic Spectrum Allocation in Cognitive Radio: Auction and Equilibrium

Cognitive radio is an emerging technique to improve the utilization of radio frequency spectrum in wireless communication networks. In this paper, we consider the problem of spectrum sharing among a few primary users and multiple secondary users through auction games. With the second-price auction and VCG auction, we adopt a utility function to obtain the optimal total payoffs the secondary users. User collusion and cooperation behaviors have been discussed by an interference graph. The simulation results show that user collusion usually deteriorate the efficiency of dynamic spectrum allocation and may cause instability of the communication system, while the cooperation among the secondary users can not only enhance the spectrum efficiency but also compensate the primary users through some cooperative mechanisms.

TOA estimation for UWB through-wall application

The wall filter effect on the UWB through-wall impulse is investigated. The problem addressed is the TOA estimation error for the UWB indoor application. Simulation and analysis point out that it is advisable to employ the proper impulse to achieve the high time resolution rather than to employ the impulse as short as possible. The high time resolution and distortion by wall filter effect should be trade off and well considered when the impulse is chosen for the through-wall application. The shorter through-wall impulse it is, the greater distortion it suffers. For templates mismatching with the received signal, the receiver estimates the wrong TOA against the peak of the correlation. The proposed solution is to modify the template according to the application scenarios for different wall materials. Mathematical analysis is exploited to show the validity of this method.

AOHR: AODV and OLSR Hybrid Routing Protocol for Mobile Ad Hoc Networks

A hybrid routing protocol named AOHR (AODV and OLSR hybrid routing) for mobile ad hoc networks is proposed in this paper. In AOHR, each node maintains topology information of a zone with radius not larger than a set value. By the proactive property of OLSR, when a node wants to communicate with another node within its zone, packets can be transmitted directly. Otherwise, a routing request procedure will be invoked by the reactive property of AODV. In addition, AOHR utilizes MPRs (multipoint relays) to reduce overheads of route requests. This paper also proposes dynamic zone radius maintenance for AOHR to dynamically adapt to various scenarios. Analysis and simulation results show that AOHR combines the characters of high data delivery fraction, low overheads, and short delay in AODV with the characters of optimized routing length in OLSR, which means that AOHR is immune from topological structures

PVPSU: Publicly Verifiable and Parallel Share Updates for Mobile Ad Hoc Networks

Based on RSA algorithm, this paper provides a publicly verifiable and parallel share update algorithm for mobile ad hoc networks. According to Diffie-Hellman assumption and public verifiability, this new algorithm improves security and robustness. In addition, communication rounds have been decreased from three to two. This paper also proposes a new multiplicative shuffle scheme for share updates. Our simulation and implementation evaluate and confirm that the solution is effective

A universal baseband signal processing system for I/Q modem based on DSP and ASSP

A universal baseband signal processing system for I/Q modem based on DSP and ASSP (application specific standard product) is proposed in this paper. By choosing an universal digital radio baseband processor (ASSP) as the co-processor of DSP, the computation burden on DSP has been released significantly. Compared with some traditional solutions to the issue, the technique discussed in this paper is more promising and attractive. It is extremely compact and power-efficient that is often required by the portable devices in mobile communication. While in the illustration of the system, special emphases are laid on the architecture and operation principle of the system and the algorithms used in the baseband signal processing.

Investigation on DID/DOD interface circuit in trunking communication system

This paper introduces a useful direct inward dialing/direct outward dialing (DID/DOD) interface circuit in a trunking communication system, which is controlled by a single-chip microprocessor. The double tone multi-frequency encode/decode circuit and voice integration circuit provides 2/4 wire conversion, voice indication, and DTMF code transmission and reception. The DID/DOD interface circuit provides the automatic access to voice and data communication between the radio subscriber and PABX/PSTN subscriber in a mobile communication system.

Performance analysis of multiple-access protocol ALOHA/PCD

This paper presents an improved ALOHA protocol named ALOHA/PCD (ALOHA with partial collision detection) and analyzes the performance of delay and channel throughput. The results are compared with the frame ALOHA protocol and simulation results are presented.