Chunyi Song

A cognitive relay approach for multi-hop wireless ad hoc communication

Owing to retransmission of lost packets and bursty nature of source data, even an ad hoc network with low average traffic may suffer heavy traffic in some certain periods, which in further may degrade system performance, particularly in multi-hop wireless communication. Aiming to provide a solution to above problem, in this paper, we construct a hybrid system based on plural ad hoc networks, which are defined as primary radio networks (PRNs), and a secondary radio network (SRN). In the hybrid system, a cooperative relay scheme based on dynamic spectrum access, defined as cognitive relay, is adopted for retransmitting the lost packets of PRNs. Cognitive relay is carried out by SRN in spectrum hole. Simulation-based evaluation shows that the proposed cognitive relay, compared to existing retransmission protocol, is more effective in providing QoS-guaranteed communication.

Evaluations of elliptical modulation scheme

This work aimed to evaluate some modulation methods, which have been defined based on elliptical modulation scheme, namely are eccentricity shift keying (ESK), inclination angle shift keying (IASK) and elliptical phase shift keying (EPSK). In this paper, signal characteristics of these three modulation schemes and effect of eccentricity to the waveforms have been demonstrated and analysed, through observing real signals generated by using DSPs, both in time-domain and frequency-domain; performances of IASK, 4-EPSK and 8-EPSK, as three modulation methods capable of 1-bit, 2-bit and 3-bit information transmission under the same carrier frequency respectively, have been evaluated through Matlab simulation in terms of BER. Advantages over existing modulation schemes suggested that the newly proposed modulation schemes can contribute to the improvement of wide-band wireless communication systems.

Rate 2/3 Trellis-Coded 8-ary Elliptical Phase Shift Keying Modulation

In this paper, 8-ary Elliptical Phase Shift Keying (8EPSK) Trellis-Coded Modulation and set partitioning based on the sum of soft metric distance are proposed and developed. The criterion to design and search for good TCM codes is also presented. The performance of 8EPSK-TCM has been evaluated through Matlab simulation in terms of BER. The results show that the performance of 8EPSK-TCM outperforms the conventional 8PSK-TCM and 8EPSK convolutional codes.

Improvement on power efficiency of MPSK by employing elliptical signals

By replacing a circle with ellipses in constellations of MPSK (M=2,4,8), this paper propose several modulation schemes defined as M-ary elliptical phase shift keying (M-EPSK, M=2,4,8). Both mathematical analysis and computer simulations show that M-EPSK can improve power efficiency over MPSK, and have high flexibility to make trade-offs on power efficiency and bandwidth efficiency by varying eccentricities

Iterative Unequal Length Search Syndrome Decoding for Product Codes

In this paper, Iterative Unequal Length Search (ULS) Syndrome Decoding for Product Codes is proposed by introducing an idea of unequal length search space. The principle and realization of the algorithm is presented. Moreover, a mathematical performance and decoding complexity analysis is illustrated. Compared to the conventional Equal Length Search (ELS) Syndrome algorithm, experimental results indicate that the iterative ULS syndrome decoding algorithm, not only significantly reduces the decoding complexity, but also improves the error-correcting performance. Because of the balance between the odd and even circuits, the speed of parallel processing is increased and hardware resources are saved accordingly. Simulations results have shown that the proposed algorithm leads to a decrease of 25%~30% of search complexity and a gain of 0.3 dB in the BER performance for various subcodes.

A Proposal of an Efficient Timing Recovery Algorithm for 4-ary Elliptical Phase Shift Keying

M-ary elliptical phase shift keying (M-EPSK, M=2,4,8) have been proposed in our previous works. Evaluation results show that M-EPSK can achieve advantage over MPSK on noise performance. In particular, M-EPSK can adoptively make trade-offs between bandwidth efficiency and power efficiency by varying eccentricities. However, the analysis in previous works also shows that the achieved performance of M-EPSK is vulnerable to synchronization errors. To realize efficient signal detection and to provide simplicity for receiver 4-EPSK (M- EPSK of M=4), in this paper, we propose an efficient timing recovery algorithm for 4-EPSK by employing envelope characteristics of elliptical signals.

Cognitive frequency sharing among primary radio networks for multi-hop communication

In cognitive radio (CR), primary users have exclusive privilege to access their licensed channels. Therefore, a transmission failure occurs when one or more primary users access the licensed channel during a transmission by users in secondary radio network (SRN). We define such channel access by primary users as return of primary users. Transmission failure caused by return of primary users may not be neglectable if we consider the bursty nature of source data in large amount of networks, especially for multi-hop communication due to the large transmission duration. Furthermore, existing wireless communication systems are facing challenges on flexibility to bursty dynamic data traffics. Aiming to develop solutions for above tasks, we propose a cognitive frequency sharing (CFS) approach for transmitting packets of primary radio networks (PRNs). Under cooperation of SRN, plural independent PRNs share their idle spectrum resources (usually referred as to spectrum holes) in an opportunistic manner. CFS causes no influence to transmission independence within each PRN. Simulation results verify the effectiveness of CFS in improving both the throughput of PRNs and condition of spectrum holes that are for SRNpsilas use.

Improvement on Flexibility of Fixed Multiplexing Radio Networks by Employing Cognitive Relay

Fixed multiplexed access radio networks can realize collision-free transmission while suffering low flexibility, especially in ad hoc communication. This paper demonstrates that a dynamic spectrum access based cooperative relay technology, defined as cognitive relay, contributes toward improving the flexibility of fixed radio networks to bursty heavy traffic, unbalanced traffic loads and terminal mobility.

Effects of Eccentricity to Performance of M-ary Elliptical Phase Shift Keying (M=4,8)

M-ary Elliptical Phase Shift Keying (M-EPSK) have been proposed and evaluated through simulations in our previous works. According to the simulation results, M-EPSK (M=4,8) can achieve better noise performance than MPSK; in particular, M-EPSK can adaptively realize trade-offs between bandwidth efficiency and power efficiency by varying the eccentricity. Eccentricity is the main modulation variable that makes M-EPSK distinctive comparing with conventional MPSK. Substantial effects of eccentricity to performance of M-EPSK have been verified in simulations; however, prior to exploring applications of M-EPSK in communication systems, principle behind the effects of eccentricity to performance needs to be further studied. In this paper, we theoretically evaluate effects of eccentricity to decision parameters of performance, and then explore a novel solution based on approximate treatment to derive closed-form BER approximations of M-EPSK over an AWGN channel. In the BER approximations, the effects of eccentricity to both error performance and bandwidth efficiency of M-EPSK are mathematically derived. In addition, the theoretical results agree with simulation results.

Improvement on bit-error-rate performance of DS-CDMA by employing 4-elliptical phase shift keying

Some modtilation schemes with the general name of Elliptical Modulation Scheme.s, have been propused and evahtated, in terms of Bit-Ervor-Rate (BER) performance. name[\, are Eccentricity Shifr Keving (ESK), Inclination Angle Shift Keyinz (IASK). Rotation Freqriency Shlfi Keying (RFSK) and Elliptical Phase Shft Keying (EPSK). Based on their advantages over &sting modiilation schemes. this paper aimed to confirm the contvihiitions of 4-EPSK, one of Elliptical Modulation Schemes with 2-bit in?ur.mation tvan.smi.ssion capability, to the improvement uf CDMA commrmication systems. In the paper, we investigated the possible applications of 4-EPSK to CDMA systems. through evahiating BER performance of synchronous DS-CDMA by employing 4-EPSK a~ its mod2ilation scheme, with an M-sequence ar7d an orthogonal Gold sequence respectively, along with comparison to that of DS-CDMA by employing QPSK: simiilation restilts have been achieved based on changeable nrimber of zi.ser.s, under A WGN and flat Rayleigli .fading ernironmen/ respectively. Advantage.s of DS-CDMA -4-EPSK over e.risting DS-CDMA-QPSK achieved in .sim~ilatiims, implies that 1 7 ~ , employi~g 4-EPSK as its modrrlatiun scheme. CDMA swtems can be improved it? terms of BER per:jormauce.