Hideo Kobayashi, Wuwei Lan, Peng Shi, Shuaichen Chang, Jiang Guo, Henghui Zhu, Zhiguo Wang, Patrick Ng. Proceedings of the 2025 Conference of the Nations of the Americas Chapter of the Association for Computational Linguistics: Human Language Technologies (Volume 1: Long Papers). 2025.

We present PAIRSPANBERT, a SPANBERTbased pre-trained model specialized for bridging resolution.PAIRSPANBERT is pre-trained with a novel objective that aims to learn the contexts in which two mentions are implicitly linked to each other from a large amount of data automatically generated either heuristically or via distance supervision with a knowledge graph.Despite the noise inherent in the automatically generated data, we achieve the best results reported to date on three evaluation datasets for bridging resolution when replacing SPANBERT with PAIRSPANBERT in a stateof-the-art resolver that jointly performs entity coreference resolution and bridging resolution.

We examine the extent to which supervised bridging resolvers can be improved without employing additional labeled bridging data by proposing a novel constrained multi-task learning framework for bridging resolution, within which we (1) design cross-task consistency constraints to guide the learning process; (2) pretrain the entity coreference model in the multitask framework on the large amount of publicly available coreference data; and (3) integrate prior knowledge encoded in rule-based resolvers.Our approach achieves state-of-theart results on three standard evaluation corpora.

The state of bridging resolution research is rather unsatisfactory: not only are state-of-the-art resolvers evaluated in unrealistic settings, but the neural models underlying these resolvers are weaker than those used for entity coreference resolution. In light of these problems, we evaluate bridging resolvers in an end-to-end setting, strengthen them with better encoders, and attempt to gain a better understanding of them via perturbation experiments and a manual analysis of their outputs.

While Yu and Poesio (2020) have recently demonstrated the superiority of their neural multi-task learning (MTL) model to rulebased approaches for bridging anaphora resolution, there is little understanding of (1) how it is better than the rule-based approaches (e.g., are the two approaches making similar or complementary mistakes?)and ( 2) what should be improved.To shed light on these issues, we (1) propose a hybrid rule-based and MTL approach that would enable a better understanding of their comparative strengths and weaknesses; and (2) perform a manual analysis of the errors made by the MTL model.

Bridging reference resolution is an anaphora resolution task that is arguably more challenging and less studied than entity coreference resolution.Given that significant progress has been made on coreference resolution in recent years, we believe that bridging resolution will receive increasing attention in the NLP community.Nevertheless, progress on bridging resolution is currently hampered in part by the scarcity of large annotated corpora for model training as well as the lack of standardized evaluation protocols.This paper presents a survey of the current state of research on bridging reference resolution and discusses future research directions.

This paper considers a problem of user and access point associations in heterogeneous wireless networks consisting of multiple radio access technologies. The current association policies are mostly based on a selfish user behavior optimizing their own decision criteria. Such simple strategies, however, might fail especially in a congested place with a large number of users. From this perspective, this study propounds a strategy for optimizing the problem that aims at sustainably and fairly maximizing the minimal utility of users. The minimal utilities can be obtained from bare essentials of the quality of experience and defined by considering different requirements of each user. In order to analyze characteristics of the proposed selection strategy, we conduct simulations comparing it with the other selection method under each evaluation criterion. Numerical results suggest that the proposed selection i) enhances the total minimal utility in sustainable and fair manners, ii) indicates a distinctive trend in load balancing and iii) requires a comparable computational time and handover frequency in contrast with the other selection.

This paper discusses an election problem of multiple leaders in a network divided into clusters which specifically takes a form of ring structures or cycles. The objective function is defined by considering a positional relation between adjacent leaders aiming at the reduction of communication latency in a distributed network control. We propose several heuristic approaches which can be adopted to solve the optimization problem in a polynomial time. Our simulations verify the effectiveness of the obtained solutions in different types of graph models.

Wireless multi-hop networks are candidate communication infrastructures in developing regions because their installation cost is quite low comparing to that for conventional wired networks. Reliable and scalable dissemination mechanism is required in practical multi-hop networks. Cooperative communication is a new scheme to improve communication performance to realize a reliable dissemination mechanism. However, high mobility networks have a big issue for autonomous control for cooperative communication. Additionally, conventional cooperative schemes cannot reduce packet collisions even if packet collisions are a big degradation factor of performance in dense multi-hop networks. We have discussed a new cooperative communication scheme that employs Orthogonal Frequency-Division Multiplexing (OFDM). Our scheme can improve communication performance and reduce packet collisions based on distributed control matter. Our advance evaluation has shown a good potential of the proposed scheme to improve communication performance in multi-hop network simulations. On the contrary, the feasibility of the proposed scheme with a real hardware device was not shown. This paper evaluates the feasibility of our original cooperative communication scheme on IEEE 802.11a standard devices. Almost all conventional cooperative communication schemes require a special physical layer and a media access control mechanism. We have focused on a characteristic of OFDM, where a receiver can demodulate multiple signals within a guard interval period. The experimental evaluation has been performed with software defined radio devices (USRP B200). We have implemented multiple transmitters, a receiver and a fading simulator for each transmitter with two USRP B200 devices. The results can show that the proposed scheme works well on IEEE 802.11a standard devices and improves communication performance in practical situations. Hence, the proposed scheme will be a new candidate of cooperative communication mechanisms that can employ general consumer devices and can realize effective dissemination mechanism for multi-hop networks.

This paper considers a problem of user and access point associations in heterogeneous wireless networks consisting of multiple radio access technologies. We propose a strategy for optimizing the problem that aims at maximizing the total minimal utility of users in the longer term. The minimal utilities can be obtained from bare essentials of the quality of experience and defined by considering different requirements of each user. In order to analyze characteristics of the proposed selection strategy, we conduct simulations comparing it with other selection mechanisms under criteria such as minimal utility, sustainability, fairness, and load balancing.

This paper aims to improve the network performance in cluster-based IEEE 802.15.4 beacon enabled WSNs with cluster mobility and traffic fluctuations. The cluster mobility and traffic fluctuations cause severe beacon collisions in such WSNs, leading to the great degradation in the network performance. To achieve the performance improvement, we introduce the traffic adaptive distributed backoff mechanism into previously proposed SD reuse mechanism for simple autonomous SD allocation, and examine the performance gain obtained by introducing the traffic adaptive distributed backoff mechanism. The simulation results demonstrate the effectiveness of the traffic adaptive distributed backoff in such type of WSNs.

Orthogonal Frequency Division Multiplexing (OFDM) signal would be damaged significantly by inter- carrier interference (ICI) in higher time-varying fading channels which leads fatal degradation of bit error rate (BER) performance due to the loss of orthogonality among subcarriers. To solve this problem, this paper proposes an iterative based maximum likelihood demodulation (MLD) method which can achieve better BER performance with lower computation complexity even in higher time-varying fading channels. The features of proposed method are to employ a time domain training sequence (TS) in the estimation of channel impulse response (CIR) instead of using pilot subcarriers in the frequency domain and to employ a time domain equalization (TDE) method with a maximum likelihood (ML) estimation instead of using a conventional frequency domain equalization (FDE) method. This paper also proposes a low-complexity iterative method for solving the simultaneous equations in the MLD method instead of using an inverse matrix calculation. This paper presents various simulation results in higher time-varying fading channels to demonstrate the effectiveness of proposed method as comparing with the conventional frequency domain equalization method.

Smartphones are a new type of mobile devices that users can install additional mobile software easily. In the almost all smartphone applications, client-server model is used because end-to-end communication is prevented by NAT routers. Recently, some smartphone applications provide real time services such as voice and video communication, online games etc. In these applications, end-to-end communication is suitable to reduce transmission delay and achieve efficient network usage. Also, IP mobility and security are important matters. However, the conventional IP mobility mechanisms are not suitable for these applications because most mechanisms are assumed to be installed in OS kernel. We have developed a novel IP mobility mechanism called NTMobile (Network Traversal with Mobility). NTMobile supports end-to-end IP mobility in IPv4 and IPv6 networks, however, it is assumed to be installed in Linux kernel as with other technologies. In this paper, we propose a new type of end-to-end mobility platform that provides end-to-end communication, mobility, and also secure data exchange functions in the application layer for smartphone applications. In the platform, we use NTMobile, which is ported as the application program. Then, we extend NTMobile to be suitable for smartphone devices and to provide secure data exchange. Client applications can achieve secure end-to-end communication and secure data exchange by sharing an encryption key between clients. Users also enjoy IP mobility which is the main function of NTMobile in each application. Finally, we confirmed that the developed module can work on Android system and iOS system.

Broadband Analog Network Coding (ANC) based on OFDM has been widely investigated to increase capacity of bi-directional relay communications. The broadband ANC based on OFDM technique is required to estimate channel frequency responses (CFRs) between both user terminals (UTs) and a relay station (RS) precisely so as to remove the self-information data from the received signal and to demodulate the other user's information data with frequency equalization. Many channel estimation methods have been proposed for the OFDM based broadband ANC. However bit error rate (BER) performance of these methods would be degraded relatively in higher time- varying fading channels due to the inaccurate estimation of CFR. To solve this problem, this paper proposes a CFR estimation method which can achieve better BER performance with keeping higher transmission efficiency even in higher time-varying fading channels. The salient features of proposed CFR estimation method are to enable the estimation of combined CFR at the UT for both channels between the UTs and RS by using scattered pilot subcarriers and to enable the demodulation of information data without feedback information of CFR estimated at the RS. This paper presents various simulation results in the higher time-varying fading channels to demonstrate the effectiveness of proposed CFR estimation method for the bi-directional OFDM based ANC.

This paper aims to provide performance enhancement to our previously proposed simple autonomous active period selection scheme for cluster-tree based IEEE 802.15.4 beacon enabled WSNs under cluster mobility environments. The cluster mobility causes severe beacon collisions and greatly degrades the system performance. To enhance the system performance of WSNs with cluster mobility, this paper proposes an active period reuse mechanism to the active period selection scheme, and investigates its system performance. The results evaluated by computer simulation demonstrate the proposed mechanism can improve the system in cluster-tree based WSNs under cluster mobility environments.

One of the major disadvantages of OFDM technique is the high PAPR in the time domain signal. The larger PAPR signal would cause the fatal degradation of BER performance and un-desirable spectrum regrowth in the nonlinear channel. One of the promising PAPR reduction methods is the Partial Transmit Sequence (PTS) method which can achieve better PAPR performance with reasonable computation complexity. But the PTS method is required to inform the side information to the receiver for the correct demodulation of data information by using the separate channel. To solve the above problem, this paper proposes a new PAPR reduction method without requiring the separate channel. The salient feature of the proposed method is to reduce the PAPR performance by reordering of clusters in the frequency domain at the transmitter and reconstructing the clusters by using the cluster ID under embedded in the data information at the receiver. The proposed method can achieve almost the same PAPR performance and computation complexity as those for the PTS method without requiring the transmission of side information. This paper presents various computer simulation results to verify the effectiveness of the proposed method.

This paper investigates simple active period selection mechanism for the cluster based WSNs employing traffic adaptive IEEE 802.15.4 beacon enabled mode, and proposes an autonomous distributed superframe duration (SD) selection scheme to reduce beacon collisions by using simple control mechanism. The proposed scheme autonomously selects an active SD by using beacon reception power monitoring with distributed fashion and also introduces a beacon status notice from sensor nodes (SNs) to their parent cluster heads (CHs) in order to prevent unnecessary SD selection at CHs. The results evaluated by computer simulation show that the proposed scheme can improve the tars mission performance while keeping the better power consumption performance in cluster-based WSNs under cluster mobility environments.

IP mobility is the technology that realizes a continuous communication even when communicating wireless nodes switch access networks. NTMobile (Network Traversal with Mobility) is a new type of IP mobility technology for the IPv4 and IPv6 networks. NTMobile nodes can also achieve IP mobility in global IP networks as well as in private IP networks by creating a tunnel route between a pair of NTMobile nodes. In NTMobile, network applications use virtual IP addresses to achieve a continuous communication at the time when real IP addresses change due to the switching of access networks or node movements. In NTMobile, we implement a packet manipulation method in the Linux kernel module so as to achieve high levels of throughput performance.

As a traffic adaptation technique in cluster-based wireless sensor networks (WSNs) employing IEEE 802.15.4 medium access control (MAC), the traffic adaptive 2-level active period control has been proposed in order to handle temporal and geographical nonuniform traffic fluctuations. This paper proposes a backoff control mechanism for the traffic adaptive 2-level active period control to enhance the system performance, especially transmission performance. The proposed mechanism autonomously adjusts the starting time of the backoff for the contention based channel accesses at the contention access period (CAP) specified by IEEE 802.15.4 MAC, and then, distributes the channel access timing to the wide range within the CAP, leading to lower channel access congestion. The results evaluated by computer simulation show that the proposed mechanism can improve the delay performance with keeping the throughput enhancement in the cluster-based WSNs under non-uniform traffic environments.

Partial Transmit Sequence (PTS) method is a well - known method which can reduce the peak-to-average ratio (PAPR) for an OFDM signal. A major drawback of PTS method is its higher computation complexity due to the necessity of larger number of inverse fast Fourier transforms (IFFT). The PTS method with low computation complexity, called decomposition PTS sub-blocking was proposed [1] which employs the radix-*- inverse fast Fourier transform (IFFT) for the signals at the middle stages of an TV-point radix-*- IFFT and decimation in frequency (DIF) domain. This method (DIF-IFFT) can reduce the computation complexity relatively while providing PAPR reduction similar to other PTS techniques. On the other hand, PTS method can improve PAPR reduction performance very well as increasing a number of weighting factors and clusters. However, the size of side information proportionally increases as increasing the number of weighting factors or/and clutters, which are required to inform the side information to the receiver for recovering the original data. In this paper, we propose the new weighting factor technique in conjunction with D-PTS sub-blocking technique which can improve both the PAPR performance and computation complexity without any increasing of side information.

The traffic adaptive 2-level active period control has been proposed for performance enhancement in cluster-based wireless sensor networks (WSNs) employing IEEE 802.15.4 medium access control (MAC) under temporal and geographical non-uniform traffic distribution. This paper proposes an adaptive backoff window control method for the traffic adaptive 2-level active period control. The proposed method adjusts the backoff window size according to the length of current active period, which is determined by the 2-level active period control, and the point of channel access in the active period and the elapsed time for transmitting packets. The results evaluated by computer simulation show that the proposed method can improve the throughput performance as well as energy efficiency in the cluster-based WSNs with non-uniform traffic distribution.

The major drawback of orthogonal frequency division multiplexing (OFDM) is a large peak-to-average power ratio (PAPR). To overcome the PAPR problem, many PAPR reduction methods have been proposed. Partial transmit sequence (PTS) method is a well known method to reduce the PAPR statistics of an OFDM signal. The PTS method can reduce the PAPR by controlling the multiplied weighting factor of sub-block both data sub carrier and clusters. The PTS method can improve PAPR reduction performance very well as increasing a number of weighting factors and clusters. However, the number of side information is proportionally increasing as increased number of weighting factors or/and clutters, which are required to inform the side information to the receiver for recovering the original data. In this paper, we propose the new weighting factor which can improve the PAPR reduction performance better than conventional PTS method. The proposed method doesn't have any additional number of side information and system complexity. The proposed method can achieve both a better PAPR performance and BER performance with keeping the same number of side information when compare with the conventional PTS method. This paper presents various computer simulation results to verify the effectiveness of proposed method.

This paper proposes an asymmetric traffic accommodation scheme using a multihop transmission technique for CDMA/FDD cellular communication systems. The proposed scheme exploits the multihop transmission for downlink packet transmissions, which require the large transmission power at their single-hop transmissions, in order to increase the downlink capacity. In these multihop transmissions, the uplink band is used for the transmissions from relay stations to destination mobile stations, and this leads more capacity enhancement in the downlink communications. The route selection method and power control for the multihop transmissions are also investigated for the proposed scheme. The proposed scheme is evaluated by computer simulation and the results show that the proposed scheme can achieve better system performance.

This paper proposes a dynamic frequency subband and code channel assignment method for multicast band division multicarrier CDMA systems. The proposed method introduces multiple channel multicast transmissions, where the multicast transmission is divided into two channels; one is for all users in the multicast group, and the other is for a part of the multicast users. The base stations individually assign the frequency subbands and code channels to these two multicast channels. The optimum and suboptimum solutions are proposed for the two-layered frequency subband and code channel assignment. The evaluation results show that the proposed method has superior throughput performance to the single channel multicast systems

The future satellite communication systems are required to support the higher transmission data rate for providing multimedia services by employing the efficient modulation method such as multi-level QAM. However, the employment of conventional single carrier transmission method with multi-level QAM would cause the fatal degradation of signal quality due to the non-linear amplifiers located at the Earth station and satellite. To overcome this problem, this paper proposes the multi-level QAM-OFDM technique with IDAR method designed for satellite channel. In the IDAR method, the characteristics of non-linear amplifiers are required to be known at the receiver. This paper also proposes the estimation method for the characteristics of the non-linear amplifiers by using low PAPR preamble symbols. Various computer simulations are conducted in this paper to verify the effectiveness of proposed method in the non-linear satellite channel

Software defined radio (SDR) terminals have the ability of communicating via several mobile systems by reconfiguring their functions. Each mobile system is requested to support a handover from/to other mobile systems in order to allow SDR terminals to communicate dynamically with several mobile systems. The paper discusses system handover between random access type mobile communication systems, which can provide connection-less services. Then, a system handover employing transmission permission probability control is proposed. The proposed scheme controls packet transmissions from the mobile terminals which are connected to the alternative system using transmission permission probability. The permission probability is controlled according to the channel load which is estimated by statistically analyzing the number of transmissions included in each received packet. Simulation results show that the proposed scheme improves the performance of each mobile system.

A dynamic cell configuration (DCC) scheme has been proposed to reduce the performance degradation due to the nonuniform traffic distribution in CDMA microcellular communication systems employing a circuit switched architecture. In this paper, we discuss the DCC scheme for the common channel communications in the uplink channels of CDMA microcellular system with nonuniform traffic distribution. Then, we propose the DCC scheme with the system control based on the estimated channel load at each base station. The results of computer simulations show that the proposed scheme improves the system performance compared with the system without DCC scheme.

The orthogonal frequency division multiplexing (OFDM) system with a frequency domain equalization method has a potential capability to provide the high speed data with keeping high signal quality even under severe multipath fading environments. To realize the potential performances of OFDM technique, it is essential to realize the higher accurate channel estimator. This paper first presents the problems of conventional channel estimator based on discrete fourier transform (DFT) method and then proposes a novel channel estimator on the basis of discrete cosine transform (DCT) method to overcome the problems of DFT method. The frequency interpolation method based on the DCT method is also proposed to provide the accurate and efficient channel estimator, which can be used in the OFDMA and MIMO systems of using the scattered pilot symbols. This work presents the theoretical and computer simulation results to demonstrate the effectiveness of proposed DCT method as comparing with those for the conventional DFT method.

This paper proposes a downlink frequency band and slot selection scheme for cellular bandwidth division MC-CDMA systems. The proposed scheme selects transmission frequency band and slot according to the signal-to-interference ratio estimated by using the pilot signal at mobile stations. Simulation results show that the proposed scheme improves the downlink throughput but degrades delay performance and it has a trade off between throughput and delay performance. By selecting suitable control parameters, the proposed scheme achieves the throughput improvement without sacrificing the delay performance.

This paper discusses self-similarity in the uplink traffic of CDMA cellular packet communications. We estimate the Hurst parameter of transmission delay time, which is collected by using computer simulation, and analyze its power spectrum. We find that self-similarity and the 1/f power spectrum are observed in transmission delay time on the uplink of a CDMA cellular packet system. Self-similarity is also analyzed for various errors of transmission power control in order to discover the system conditions under which self-similarity appears. The results of these analyses show that the power control error has a large effect on the self-similarity: self-similarity appears in a system with an accurate power control, whereas it does not appear in a system with a large power control error.

This paper proposes a transmission power control scheme to improve geographical fairness for packet transmission in the downlink common channels of CDMA cellular systems. The proposed downlink transmission power control is based on the signal-to-interference ratio predicted at mobile stations. Throughput performance and transmission delay are evaluated under perfect power control conditions. Simulation results show that the proposed scheme improves the downlink throughput and geographical fairness in packet reception across the whole cell area.

Proposes a novel integration method of selection diversity and decision feedback equalization techniques for reception of TDMA carriers. The feature of the proposed method, called decision feedback diversity with decision feedback equalizer (DFD-DFE), is that selection diversity and decision feedback equalization techniques are integrated so as to achieve an additional improvement in the BER performance as the result of interworking between these two techniques. The algorithm of the DFD-DFE is first presented, and then computer simulation results for the performance of the proposed method are provided. The BER performance of the proposed method is also compared to the conventional selection diversity with decision feedback equalizer method (SD-DFE) and the dual diversity combining and equalization method (DDC-DFE) under typical mobile radio environments, in order to demonstrate the validity of the proposed method.>