Frequency-hopping Multiple Access Research Articles

Construction of Optimal Frequency Hopping Sequence Set with Low-Hit-Zone.

In quasi-synchronous frequency-hopping multiple access (QS-FHMA) systems, low-hit-zone (LHZ) frequency-hopping sequence (FHS) sets have been well-applied to reduce mutual interference (MI). In this paper, we propose three constructions of LHZ FHS sets with new parameters via interleaving techniques. The obtained sequences can be verified that they are optimal with respect to the Peng-Fan-Lee bound.

Optimal Low-Hit-Zone Frequency-Hopping Sequence Sets With Wide-Gap for FHMA Systems Under Follower Jamming

This letter is concerned with tackling both of the multi-access interference (MAI) and the follower jamming (FJ) in frequency-hopping multiple-access (FHMA) systems via novel FH sequence (FHS) design. We consider low-hit-zone (LHZ) FHS which provides lower MAIs in quasi-synchronous FHMA systems but suffers from FJ attack. We introduce an improved LHZ-FHS with wide-gap (i.e., WG-LHZ-FHS) for the neighboring carrier frequencies so as to combat the MAI and the FJ. We first present a general method to generate new WG-FHS sets and then construct the first known WG-LHZ-FHS sets with optimal periodic Hamming correlation (PHC) properties. Besides, the error-rate performance of the constructed WG-LHZ-FHS set imposed in an FHMA system under FJ is investigated. The numerical analysis and the system simulation results indicate that the proposed WG-LHZ-FHS set provides the better error-rate performance to combat the FJ as well as satisfactory capability of MAI suppression due to its combined merits of WG and LHZ.

Frequency-hopping sequence sets with no-hit-zone through Cartesian product

For quasi-synchronous (QS) frequency-hopping multiple access (FHMA) systems, relative time delay between different users can be allowed to vary in a domain around the origin. On the other hand, for frequency-hopping sequence (FHS) sets with no-hit-zone (NHZ), there will be no hit between different sequences in case their time delay does not exceed a certain region known as NHZ. In such circumstances, NHZ-FHS sets can be well applied in QS-FHMA systems to eliminate the mutual interference (MI) and have great practical significance. In this paper, based on Cartesian product theory, three designs of NHZ-FHS sets are presented. It turns out that the newly constructed NHZ-FHS sets have optimal periodic Hamming correlation (PHC) properties and can offer help in improving the corresponding communication system performances in practice.

Throughput analysis of dynamic spectrum anti-jamming multiple-access in HF communication systems

A multiple-access networking scheme based on the new dynamic spectrum anti-jamming system is proposed in this paper. The network consists of a center node and multiple user nodes. The center node detects spectrum holes in the operation band periodically according to the user performance target. Detected spectrum holes are allocated to users who request communication. Throughput of this networking scheme is analyzed over a high-frequency (HF) interference channel. The effect of error correction coding and spectrum hole information transmission error is discussed. Throughput of this scheme and conventional frequency-hopping multiple-access (FHMA) scheme are compared. Results show that user performance increase leads to throughput decrease, which can be offset by error correction coding. If spectrum hole information transmission is in error, the throughput is not affected much as long as the bit error rate is below 10−2. Furthermore, throughput of this scheme is obviously superior to the throughput of FHMA scheme.

Frequency-hopping sequence sets with good aperiodic Hamming correlation property

When a frequency-hopping sequence (FHS) set is applied to a frequency-hopping multiple-access (FHMA) system, its aperiodic Hamming correlation (AHC) or partial period Hamming correlation (PPHC) properties affect the system synchronization and acquisition performance at receiving terminals. However, for an FHS set, the researches on its AHC or PPHC are not well understood. In this paper, we first introduce a generalized method to construct new FHS sets through other FHS sets with optimal PPHC property. Via this method, we have the flexibility of choosing the parameters of newly constructed FHS sets, such that a large number of new FHS sets can be obtained. Then, we analyze the AHC performance of our newly constructed FHS sets. Finally, we present two new classes of FHS sets with good AHC property.

Construction of optimal low-hit-zone frequency hopping sequence sets under periodic partial Hamming correlation

In practice, when a frequency-hopping sequence (FHS) set is applied in a frequency-hopping multiple-access (FHMA) system, its periodic partial Hamming correlation (PPHC) rather than its periodic Hamming correlation (PHC) within the whole period is used to evaluate the system performance. Moreover, FHS sets with low hit zone (LHZ) can be well applied in quasi-synchronous (QS) FHMA systems in which some relative time delay among different users within a zone around the origin can be allowed. Therefore, it is very urgent to conduct research on LHZ FHS sets with optimal PPHC property in depth. In this paper, we first derive a new tighter lower bound on the maximum PPHC of an LHZ FHS set. Then we present a new class of optimal one-coincidence FHS sets. Finally we have a construction of LHZ FHS sets which can be optimal with respect to our new lower bound.

Self-Organizing Hit Avoidance in Distributed Frequency Hopping Multiple Access Networks

In this paper, we investigate the frequency hit avoidance problem in distributed frequency hopping multiple access (FHMA) networks, in which each user intends to avoid the frequency hit with others by choosing the appropriate frequency set and frequency hopping sequence. First, we define the network hit degree as the metric for the hits, and formulate the frequency hit avoidance problem as an optimization problem of the network hit degree. Second, we formulate a non-cooperative game model to solve this optimization problem, and prove the game is an exact potential game, which illustrates that the Nash equilibria (NE) point of the game is the optimal solution of the optimization problem. Finally, we propose a fragment-based distributed hit avoidance (FDHA) learning algorithm and prove that the learning algorithm can converge to the NE point. The simulation results show that the proposed algorithm can converge to the optimal solution rapidly such that the FHMA network is hit-free.

New Constructions of Optimal Frequency-Hopping Sequence Sets with Low-Hit-Zone

The frequency-hopping sequence set with low-hit-zone (LHZ FHS set) is useful for eliminating multiple-access interference in quasi-synchronous frequency-hopping multiple access systems. In this paper, basing on Cyclotomy, the discrete logarithm function and the Chinese remainder theorem, we construct two classes of LHZ FHS sets which have new parameters not covered in the literature. It is proved that proposed LHZ FHS sets are optimal respectively with respect to the Peng-Fan-Lee bounds.

Theoretical lower bound on average periodic partial Hamming correlations of frequency‐hopping sequence set

Owing to the limited synchronisation time and hardware complexity of frequency-hopping multiple access (FHMA) systems, partial Hamming correlation of the frequency-hopping sequence (FHS) set applied by the FHMA system plays an increasingly important role in measuring the performance of the system. A new lower bound on the average periodic partial Hamming correlation which is tighter than the existing one in a particular case is introduced. The new lower bound includes some earlier theoretical lower bounds on the average Hamming correlation of the FHS set as special cases. A necessary and sufficient condition for obtaining optimality with regard to the new bound is also presented.

Concatenated Codes with Two Inner Coding Schemes in Frequency-Hopping Spread Spectrum Multiple-Access Channels

In this paper, we analyze the performance of a concatenated code with two different inner decoding schemes. One is the error- detecting inner coding, and the other is the error-detecting-and-correcting inner coding scheme. We compare the performance of the two decoding schemes for finite and infinite block length cases when the concatenated code is applied to slow frequency-hopping spread-spectrum multiple access (FH-SSMA) communication systems. Our results show that the error-detecting-and-correcting inner decoding scheme outperforms the error-detecting inner decoding scheme for finite block lengths, while there exists a performance trade-off for infinite block length case.

A lower bound on the average Hamming correlation of frequency-hopping sequence sets

The average Hamming correlation is an important indicator of frequency-hopping sequences (FHSs)which measures the average performance of FHSs employed in practical frequency-hopping multiple access (FHMA) communication systems.In this paper, a lower bound on average Hamming auto- andcross correlations of an FHS setis derived. It generalizes and improves the lower bound proposed recently by Peng, Niu and Tang.A simple necessary and sufficientcondition for an FHS set to meet the new bound is given.Based on this condition, two classes of FHS sets whose average Hamming correlations reach the proposed bound are introduced.

Analysis of asynchronous frequency hopping multiple‐access network performance based on the frequency hopping sequences

In this study, the authors investigate the impact of the frequency-hopping (FH) sequence on the packet transmission performance of the asynchronous frequency-hopping multiple-access (FHMA) network. According to the model of the asynchronous FHMA network given in this study, the authors analyse the impact of the two important FH sequence factors – uniformity and frequency slot number – on the correct transmission probability and the packet transmission frequency efficiency. According to the non-collision probability analysed in this study, the uniformity of the FH sequence is an important issue to determine the correct packet transmission probability. Moreover, based on the definition of the packet transmission frequency efficiency given in this study, the optimal frequency slot number employed to obtain the maximum frequency efficiency is obtained. By employing three typical FH sequences, the simulation results are also included, which validates the theoretical analysis about the packet transmission performance of the asynchronous FHMA network.

Audio watermarking with high embedding capacity based on multiple access techniques

This paper deals with a new digital audio watermarking scheme based on multiple access techniques. In digital communication, multiple access techniques allow several users transmissions by taking the same communication channel. The present work proposes to embed multiple sub-watermarks in the same channel that is the audio signal. Our main objective is to investigate embedding capacity (the amount of information that can be hidden) limitations of our proposed audio watermarking system. Three multiple access techniques have been employed in the new multi-watermarking system: DS-CDMA (Direct-Sequence Code Division Multiple Access), FHMA (Frequency Hopped Multiple Access) and FDMA (Frequency Division Multiple Access). Experimental results allow us to make the choice on the best multiple access technique, in the multi-watermarking system, which significantly permits the highest embedding capacity (a data embedding rate up to 6 kb/s) with almost no loss of data imperceptibility and with acceptable extraction fidelity (BER≃10−2) even in presence of disturbances.

Managing Interference Correlation Through Random Medium Access

The capacity of wireless networks is fundamentally limited by interference. However, little research has focused on the interference correlation, which may greatly increase the local delay (namely the number of time slots required for a node to successfully transmit a packet). This paper focuses on the question whether increasing randomness in the MAC, specifically frequency-hopping multiple access (FHMA) and ALOHA, helps to reduce the effect of interference correlation. We derive closed-form results for the mean and variance of the local delay for the two MAC protocols and evaluate the optimal parameters that minimize the mean local delay. Based on the optimal parameters, we identify two operating regimes, the correlation-limited regime and the bandwidth-limited regime. Our results reveal that while the mean local delays for FHMA with N sub-bands and for ALOHA with transmit probability p essentially coincide when p=1/N, a fundamental discrepancy exists between their variances. We also discuss implications from the analysis, including an interesting mean delay-jitter tradeoff, and convenient bounds on the tail probability of the local delay, which shed useful insights into system design.

Performance of a Novel MFSK/FHMA System Employing No-Hit Zone Sequence Set over Rayleigh Fading Channel

To further suppress the multiple-access interference (MAI) in frequency-hopping multiple-access (FHMA) system, a novel kind of FH sequence set named as no-hit-zone (NHZ) sequence, is proposed for an FHMA system with M-ary FSK modulation (MFSK/FHMA) in this paper. Expressions for the decision variables are derived for the asynchronous MFSK/FHMA system with NHZ sequence set (MFSK/FHMA-NHZ) under a slow Rayleigh-fading channel model. For the special case of M=2, accurate analytic bit error rate (BER) is derived as a function of maximum relative delay D and the number of users K by a characteristic function method. The theoretical results validated by Monte Carlo simulations are used to investigate the dependence of the average BER on D and K. Comparison with the MFSK/FHMA system with Markov hit pattern (MFSK/FHMA-Markov) shows that MFSK/FHMA-NHZ system performs better than Markov hit pattern system as long as D is restricted in a certain range and further, the gain in the performance increases with increase in the value of K.

Design of an Acoustic Communication System Based on FHMA for Multiple Underwater Vehicles

This paper designs an underwater acoustic communication system based on tamed spread spectrum and Frequency Hopping Multiple Access (FHMA) for multiple underwater vehicles. In this system, multiple underwater vehicles can communicate with the console on the water surface simultaneously successfully. The communication system is com-posed of tamed spread spectrum modulation and demodulation, frequency hopping modulation and demodulation with synchronization function, 4FSK modulation and demodulation and Rake Receiver. In order to make the system more feasible, underwater channel and the effect of user number on Bit Error Ratio (BER) are also taken into account. The simulation results indicate that it is feasible to use this system to accomplish underwater communication reliably for multiple users due to the low BER.

Inter-subcarrier interference compensation in the frequency-hopped single-carrier frequency division multiple access communication system

Single-carrier frequency division multiple access (SC-FDMA) system having very good characteristic on peak-to-average power ratio is promising in communication area. But the performance of SC-FDMA system is very sensitive to inter-subcarrier interference (ICI), and existing phase noise suppression algorithm has reduced just phase noise only. Therefore the authors propose effective method, phase noise and frequency offset suppression (PNFS) algorithm, using comb-type pilot. PNFS algorithm can suppress phase noise, carrier frequency offset and even Doppler effect simultaneously in frequency domain. Through PNFS algorithm, SC-FDMA system has robust characteristic against ICI of performance degradation. Moreover, in these days, most electronic communication systems are weak to jamming. So, frequency-hopped (FH) scheme, which is one kind of spread spectrum techniques as a means of making performance better to supplement a disadvantage of SC-FDMA system on jamming attack, is considered. The authors would like to analyse ICI and jamming in SC-FDMA system and employ FH technique in SC-FDMA system because existing studies have not considered the situation regarding ICI and jamming exist simultaneously in mobile channel. So, the authors analyse degradation factors in FH-SC-FDMA system about ICI and jamming signal categorised as partial band jamming and multi-tone jamming. Then, the proposed FH-SC-FDMA system using PNFS algorithm has strong performances about ICI and jamming.

A New Set of Optimal Frequency-Hopping Sequences

In frequency-hopping (FH) multiple access systems, frequency-hopping sequences (FHSs) with optimal Hamming correlation properties are needed. Based on the d-form functions with ideal autocorrelation properties, a new set of FHSs is constructed. The new FHS set is optimal with respect to the Peng-Fan bounds and each FHS in the set is optimal with respect to the Lempel-Greenberger bound.

No-Hit-Zone Frequency-Hopping Sequence Sets with Optimal Hamming Autocorrelation

In quasi-synchronous frequency-hopping multiple access (QS-FHMA) systems, no-hit-zone frequency-hopping sequence (NHZ-FHS) sets are commonly employed to minimize multiple access interference. Several new constructions for optimal NHZ-FHS sets are presented in this paper, which are based on interleaving techniques. Two types of NHZ-FHS sets of length 2N for any integer N ≥ 3 are constructed, whose NHZ sizes are some even integers. An optimal NHZ-FHS set of length 2N with odd NHZ size for any integer N ≥ 6 is also presented. And then, optimal NHZ-FHS sets of length kN are given by generalizing one of the proposed constructions for NHZ-FHS sets of length 2N, where k and N are any positive integers such that 2 ≤ k < N. All the FHSs in the new NHZ-FHS sets are non-repeating FHSs which are optimal with respect to the Lempel-Greenberger bound. Our constructions give new parameters which are flexible in the selection of NHZ size and set size.

A Novel Modulation with Parallel Combinatory and High Compaction Multi-Carrier Modulation

In this paper, we propose a new modulation named parallel combinatory/high compaction multi-carrier modulation (PC/HC-MCM) using the techniques of parallel combinatory orthogonal frequency division multiplexing (PC-OFDM) and high compaction multi-carrier modulation (HC-MCM). Two types of PC/HC-MCM systems, which are named as modulated PC/HC-MCM system and (unmodulated) PC/HC-MCM system, can be designed. The modulated PC/HC-MCM system achieves better bit-error rate (BER) performance than that of HC-MCM system with equal bandwidth efficiency (BWE). The PC/HC-MCM system can obtain the better peak-to-average power ratio (PAPR) characteristics by selecting appropriate constellation for each subcarrier. On the other hand, since PC/HC-MCM can divide the PC-OFDM symbol duration into multiple time-slots, the advantages of frequency hopping (FH) can be applied in the PC/HC-MCM system. Therefore, we also combine the PC/HC-MCM and frequency hopping multiple access (FHMA) to propose a novel multiple access (MA) system. It can simultaneously transmit multiple users' data within one symbol duration of PC-OFDM.