Chain-based routing protocols such as PEGASIS reduce redundant transmissions in Wireless Sensor Networks (WSNs), yet their static link structures and greedy neighbor selection often result in long communication links, uneven energy depletion, and premature network failure. Achieving both globally optimized chain construction and energy-balanced routing under diverse network deployments therefore remains a significant research challenge. To address these limitations, this paper proposes GWO-PEGASIS, a scalable two-stage optimization framework that integrates K-means clustering for spatial partitioning with the Grey Wolf Optimizer (GWO) to construct globally optimized intra- and inter-cluster chains under connectivity constraints. In the first stage, K-means forms spatially compact clusters based on node density, initial energy, and spatial distribution. In the second stage, GWO enables adaptive chainhead selection, balanced multihop forwarding, and improved spatial load distribution. Extensive simulations validate the effectiveness of the proposed method: GWO-PEGASIS shortens total chain length by 10.46% relative to PEGASIS, more than doubles the network lifetime, and further improves lifetime by 11.2% and 14.6% over EB-PEGASIS-SCL and MC-CRITIC-KM, respectively. It also achieves the lowest per-round energy consumption, the most balanced residual-energy distribution, and the highest throughput among all evaluated protocols. These results demonstrate that GWO-PEGASIS offers a robust, energy-efficient, and scalable routing solution for WSNs, highlighting the strong potential of swarm-intelligence-driven optimization for addressing complex topology design challenges in resource-constrained environments.

This paper proposes an adaptive artificial-noise (AN) strategy to enhance the secrecy rate in reconfigurable intelligent surfaces (RIS)-assisted wireless networks with joint active/passive beamforming. Specifically, the AN jams not only the eavesdropper but also the legitimate user. If the AN significantly interferes with the legitimate user, the base station (BS) should adaptively choose not to transmit the AN. Additionally, we compare two RIS-beamforming schemes: the RIS-D and RIS-AN schemes. The RIS-D scheme adjusts the phase shifts of RIS elements to enhance the data signal of the legitimate user. The RIS-AN scheme aims to reflect and increase the interference to the eavesdropper. The adaptive AN strategy will jointly determine whether to transmit the AN and select the proper RIS-beamforming scheme. We introduce a heuristic design that jointly determines the active and passive beamforming vectors through closed-form expressions. We conduct comprehensive simulations to investigate how the AN affects the data rates of both the legitimate user and the eavesdropper under various integrating RIS/AN schemes. Simulation results show that by selecting the proper RIS/AN scheme, the adaptive AN strategy significantly improves the secrecy rate. Furthermore, the results also reveal key principles of adaptive selection based on the locations of the legitimate user and the eavesdropper.

Reconfigurable Intelligent Surface (RIS) is a transformative technology using the passive beamforming capabilities to create the programmable wireless environments. However, the control overhead is a challenging issue. The system needs to deliver the high-precision reflection coefficients to the RIS controller, for adjusting the phase shifts of the numerous RIS elements. Therefore, we propose a Spirograph-based discrete beamdirection strategy, which selects a set of non-uniformly distributed beam directions based on the generic patterns generated by the Spirograph (SG). We evaluate the achievable data rate and the number of controlling bits of SG-based method. We compare the SG-based method, the ideal continuous phase-shift method, and the SISO method. Simulation results show that with the properly-selected discrete beam directions, the SG-based method can achieve a comparable data rate as the ideal method, while having a lower control overhead.

This article proposes an innovative unicast/multicast unified, cross-layer, and control/user-plane splitting forwarding method, called wireless arithmetic label switching (WALS), for mobile ad hoc networks (MANETs). The WALS is based on a stateless approach: an arithmetic source-routed label is processed by the source and intermediate nodes without table lookup, causing lower protocol overheads and forwarding latency than the conventional stateless unicast/multicast routing protocols such as the dynamic source routing (DSR) and the differential destination multicast (DDM), respectively. Different from conventional unicasting/multicasting designs demanding distinct routing protocol stacks, the WALS requires a unified protocol stack, avoiding the need to distinguish unicast and multicast frames, thus simplifying the design of MANET devices. Mathematical analysis indicates that the WALS is highly scalable for both the network sizes and the number of multicast groups. Simulation results reveal that WALS effectively performs network scalability and the required overhead for the unicast and multicast capabilities. Additionally, WALS achieves superior to the other three state-of-the-art competitive multicast routing methods, including DVMRP, ODMRP, and MAODV on the performance of the packet processing latency and packet delivery ratio. As a result, the WALS can significantly enable the employment and management of integrated unicast and multicast services for MANETs.

The conventional routing protocol considers several local transmission factors in a single node for the many-to-one packet transmission. These factors lead to rapid energy consumption in some specific nodes, thereby generating energy holes to reduce network lifetime. In this article, a novel energy-balanced power-efficient gathering in sensor information systems (EB-PEGASISs) is proposed to improve energy efficiency and utilization for wireless sensor networks (WSNs). In the original power-efficient gathering in sensor information system (PEGASIS), the protocol constructs a chain-based network with the locally shortest distance rather than the globally optimal network length. To improve this, two construction algorithms are proposed to achieve the shortest network length in the EB-PEGASIS, including centralized formation and distributed construction schemes. In the centralized algorithm, the chain length of each starting node is computed, and the minimum chain length can be subsequently determined in the following packet transmission phase. In order to reduce formation complexity, a distributed method uses the$K$-means clustering algorithm to partition the network into clusters. In particular, it forms a subchain in each cluster and connects each subchain into the final shortest chain. Additionally, to balance the energy consumption among all nodes in the packet transmission phase, Jain’s fairness index for residual battery capacity is designed to minimize the fluctuation of energy consumption among nodes in a network. As a result, not only energy efficiency is achieved with the shortest chain length but also energy utilization is balanced for packet transmission. Ultimately, simulation results validate that the network lifetime of the EB-PEGASIS is about 2.46 times the original PEGASIS and 3.36 times the random projection-polar coordinate-chain (RPC) protocol for WSNs.

In traditional wireless sensor networks (WSNs), packets are mainly transmitted in a multihop routing manner. The multihop transmission, however, leads to a hotspot problem in the sink connectivity area (SCA), and the overall network efficiency is reduced due to the quick battery power exhaustion of nodes in that area. This article proposes a novel balanced routing algorithm with transmission range adjustment (BRATRA) to address the network efficiency problem, including the energy efficiency and utilization issues. First, a balanced routing strategy is designed to deal with the SCA load imbalance problem. With the shortest balanced path, the amounts of forwarding packets for the nodes in the SCA and all the other intralayers become more even. From the perspective of power equilibrium in each routing path, each node then determines its accurate transmission radius according to the derived formula and performs power control to realize the even power utilization between interlayers, thereby prolonging the overall network lifetime. Performance evaluation validates that the proposed BRATRA strategy can achieve efficient power utilization in each intralayer and double the network lifetime as compared to the Dijkstra routing strategy. Additionally, it yields better power utilization fairness among nodes, and on average only 5% of battery power is unused for all network nodes, resulting in a network lifespan ten times larger than that using a conventional strategy.

Typically, wireless sensor networks (WSNs) use limited-capacity batteries that cannot be recharged or replaced. In general, designing an energy-efficient routing protocol has a significant impact on prolonging the network lifetime. In this article, a novel distributed 2-hop cluster-routing protocol (D2CRP) is introduced to achieve energy efficiency in WSNs. In the cluster formation phase, each node obtains the information of its neighbor nodes within the 2-hop range to form the 2-hop cluster in a fully distributed manner. The transmission distance and residual energy are jointly considered to determine the energy-efficient cluster head (CH) in each 2-hop cluster. After the CH is generated, each member node can transmit packets to its 1-hop neighbor or the CH directly. To reduce the overall transmission distance for intercluster communication, multiple chains can be formed among CHs via their adjacent CHs that are closer to the base station (BS). As a result, energy-efficient intracluster and intercluster routing can be achieved for packet transmission. In addition, the optimal cluster number of 2-hop clustering is formulated and derived to minimize the energy consumption for both intracluster and intercluster communications. Simulation results show that the optimal cluster number of D2CRP can be achieved and D2CRP is effectively improved on the performances of network lifetime, energy consumption, and packet transmission than the other four state-of-the-art competitive routing protocols, including low-energy adaptive clustering hierarchy (LEACH), R-LEACH, power-efficient gathering in sensor information system (PEGASIS), and two-tier distributed fuzzy logic-based protocol (TTDFP).

In this article, a balanced multipath routing and hybrid transmission approach (BMRHTA) is proposed to effectively alleviate the imbalance of the forwarding load in a sink connection area (SCA) and prolong the network lifecycle for wireless sensor networks (WSNs). To achieve the energy efficient and balanced WSNs, three design issues, including the multipath, multihop, and single-hop transmissions, are jointly optimized to maximize the overall network lifecycle. First, the path load aggregation phenomenon in the SCA, which makes the forwarding packet load unevenly distributed among hotspots, is examined. In order to achieve the load balance in SCA, multiple shortest balanced paths are generated in the BMRHTA model. In the first stage, two uncorrelated shortest paths are discovered from each node to the sink and the optimal path selection cycle can be determined to achieve the SCA load balance. Afterward, a network equilibrium policy is offered to resolve the optimal transmission period of energy balance via hybrid transmission. As a result, the balanced shortest paths, the path selection cycle and the transmission period can be determined in the network formation phase to avoid the excessive load concentration in the subsequent maintenance phase. Simulation results show that the joint two uncorrelated balanced routing and the proposed network equilibrium policy can nearly quadruple the network lifecycle extension, as compared to a conventional node power policy. Also, the proposed BMRHTA achieves better performance than the current state-of-the-art competitive approaches in terms of energy efficiency and lifecycle.

In this article, a distributed topology control approach with hierarchical self-routing (DTC-HSR) is presented for Bluetooth low-energy (BLE) networks. First, the conventional star piconet is replaced by the designed mesh-ring subnet with better throughput and lower delay. To achieve the goal of load balancing design, two phases, including the leader selection and the topology construction are executed in the proposed approach. In the leader selection phase, each master node discovers its adjacent slave nodes to determine a leader master as a coordinator. In the topology construction phase, the local mesh-ring subnet is first formed and then the global mesh-ring subnets are interconnected into the desired DTC-HSR topology. To form the local mesh-ring subnet, each leader master computes the desired number of piconets with even link connectivity and distributes the piconet connection information for each node to form a mesh-ring subnet. In addition, each master node connects with the other local mesh-ring subnets via its associated bridge nodes, including slave nodes, intrabridges, and interbridges to create the definitive DTC-HSR scatternet. Afterward, a hierarchical self-routing strategy is jointly employed for the DTC-HSR to efficiently deliver routed packets through different mesh-ring subnets. Simulation results demonstrate that the DTC-HSR topology with the even connectivity feature outperforms the dual-ring tree (DRT) and cluster-based mesh (CBM) approaches in terms of network transmission and energy efficiency performances. The DTC-HSR configuration thus achieves efficient topology construction and hierarchical self-routing for load balancing in BLE networks.

In the fifth-generation (5G) communication system, millimeter-wave (mmWave) technology brings superior capabilities, such as higher capacity, lower latency, and a flexible beamforming structure. The interference management strategies play an important role in mmWave beamforming networks to support the multibeam operation and maximize the overall data rates for user equipments (UEs). Currently, most of the existing research do not jointly consider designs, including the mainlobe interference (MI) avoidance and resource blocks (RBs) fairness allocation. In this article, a novel fairness allocation strategy is proposed to achieve the minimum MI and a fair RB assignment for mmWave networks. To achieve the minimum MI, an MI mitigation (MIM) algorithm is designed to maximize the data rate for each UE. With the adaptive mini-timeslot design, the MIM algorithm can achieve MI cancelation for all UEs at each identical timeslot and beam. To combine MIM and fairness for RB allocation among all UEs, the MIM-fairness allocation (MIM-FA) algorithm is also presented. Based on a novel mini-timeslot with designed multiple frames, the MIM-FA algorithm can simultaneously guarantee the fairness among all UEs and mitigate MI at each mini-timeslot for each beam. Additionally, the MIM-FA algorithm can be verified that it achieves the maximum user data rate with the identical number of RBs under the lowest number of frames. Simulation results validate that the proposed MIM and MIM-FA algorithms can provide a higher data rate and better fairness for different scenarios compared to current state-of-the-art competitive approaches.

This research presents a new multichain routing strategy named the destination-oriented routing algorithm (DORA). The proposed design generates a new multichain routing scheme to transmit packets for energy-balanced WSNs. Based on the multichain routing, the optimal transmission distance between any two nodes is derived by the mathematical analysis model. With the optimal distance, the design criterion is to select the furthest forwarding node within the communication range and the direction to the sink, thus forming the multichain structures by accurate distance, direction, and multiple paths. With the shorter chain routing, unnecessary energy loss can be reduced to prolong the global network lifespan. The simulation results demonstrate that the proposed DORA doubles the network lifespan, compared with that of conventional PEGASIS and improves 60% lifespan on the RPC protocol.

This study proposes a multiple mesh-ring (MMR) topology construction with a hybrid routing strategy for Bluetooth low energy (BLE) networks. To achieve the load-balancing network, three design phases, including leader selection, role decision, and scatternet formation, are executed to generate even MMR configurations. First, each master discovers its adjacent slaves to determine a coordinator. Second, the coordinator computes the desired number of piconets with even scatternet link connectivity and distributes the scatternet connection information for each master. Finally, each designated master connects with its associated nodes, including slaves, intrabridges, and interbridges to create the link balanced MMR scatternet. To jointly design an energy-efficient routing protocol for the MMR topology, a hybrid routing strategy is deployed to perform the shortest path routing inside the mesh-ring subnet, and self-routing through different mesh-ring layers. Simulation results demonstrate that the balanced MMR topology leads to a significant gain in terms of network transmission performance and network lifetime when compared to the conventional dual-ring tree (DRT) and cluster-based mesh (CBM) approaches for BLE networks.

This study presents a novel nonuniform power formation algorithm (NUPFA) for Bluetooth low-energy (BLE) networks. With two stages, NUPFA constructs the scatternet in a distributed manner. In the first stage, the master and slave nodes discover each other using low-level power to form an initial scatternet. In the second stage, each master alternatively scans or advertises using normal power to interconnect dual links among any two piconets until the whole scatternet is constructed. Using nonuniform power configuration, an energy-efficient scatternet is generated, since packet transmission power can be reduced in each piconet to minimize overall power consumption. With additional scatternet links, more routing paths can be utilized to reduce the path length and enhance network efficiency. simulation results show that compared with the existing cluster-based on-demand routing protocol (CORP) and Bluetooth Mesh schemes, the NUPFA protocol achieves superior energy efficiency for packet transmission. Also, the dual link features can effectively reduce packet latency, thereby improving the overall performance of BLE mesh networks.

In this paper, subcarrier pairing and power allocation are jointly investigated to maximize the energy efficiency (EE) of a dual-hop multicarrier decode-and-forward (DF) relay network. The optimization problem is formulated as a ratio of the spectrum efficiency (SE) over the entire power consumption of the network subject to total power and subcarrier pairing constraints. A near-optimal iterative scheme is proposed to perform the subcarrier pairing and power allocation for achieving the maximum EE of the network. A two-step suboptimal resource allocation scheme is further proposed to reduce the complexity, in which the subcarrier pairing is first performed by considering the channel quality of the source-to-relay (SR) and relay-to-destination (RD) links, followed by an energy-efficient power allocation scheme to maximize the EE. Numerical results are presented to confirm the effectiveness of the proposed schemes and to demonstrate the tradeoff between EE and SE performances.

Transmission policy of the hybrid energy model allows maximizing energy utilization of small cells in the wireless system. One of the key challenges in maximization of energy utilization is to minimize the grid power and energy wastage of green harvested energy (GHE) sources simultaneously. In this paper, unlike existing transmission policy solution which focuses only on one highlighted objective, we proposed multi-objective model checking for Markov decision process (MOMC-MDP) with linear temporal logic (LTL) to find the best feasible solution for packet transmissions in each time slot. Based on the MOMC-MDP for different battery status, the optimal transmission policy of small cells is obtained in order to deliver the highest harvest energy sources and guarantee the quality of service (QoS) demands. Numerical results show that the MOMC- MDP scheme can ensure to efficiently use the limited energy of battery while maximizing green energy utilization in real-time transmission.

In this work, a reliable topology construction protocol (RTCP) called Dual‐Ring Tree scatternet with a self‐routing algorithm is proposed for hybrid single‐hop/multi‐hop situations. To benefit from the advantages of the hybrid scenarios, a dual‐ring subnet is presented as a single‐hop solution for one dense area, while a tree‐shaped subnet is designed as a multi‐hop solution for other sparse areas. To the best of the author's knowledge, this is the first time that such an algorithm has been presented to deal with the hybrid scenarios. Since the dual‐ring structure serves as the core network design, the resulting architecture demonstrates better fault tolerance capability than the conventional single ring networks do. In addition, a self‐routing protocol is introduced to efficiently deliver packets over the scatternet. Simulation results suggest that the RTCP scheme outperforms conventional Bluetooth hybrid ring tree (BlueHRT) and Bluetree methods in terms of routing performance and network survivability for Bluetooth ad hoc networks.

In this paper, a novel multi-carrier and multi-antenna for a multi-tier cellular network is presented for Long-Term Evolution Advanced (LTE-A) heterogeneous networks (Het-Nets) with carrier aggregation enhancement. First, we investigate a system model of frequency domain load balancing-based inter-cell interference coordination (ICIC) to minimize the total interference, while satisfying the required quality of service constraints. To achieve the desired system performance, a heuristic solution by joint spectrum and antenna allocation is then proposed, which operates at the base station side to enable efficient interference management. The optimal deployment for component carriers and antennas at the serving base station is updated for specific time periods while passively receiving the system information transmitted from neighboring base stations. Furthermore, system level simulations are carried out to demonstrate how the throughput can be greatly improved by our solution, as compared to conventional methods such as the randomized and static ICIC approaches.

Blue web is a self-organizing Bluetooth-based multihop network equipped with a scatter net formation algorithm and a hybrid routing protocol. Blue web uses a designated root node to initiate scatter net formation and two mechanisms are introduced. One is the role exchange mechanism in which only slave nodes serve as the role of relay through the whole scatter net. The other one is the return connection mechanism in which we convert the scatter net from a tree-shaped to a web-shaped topology. In this paper, a variant-hop algorithm in forming Bluetooth sensor scatter net is proposed. Based on the design of Blue web, this algorithm is a tier-based method to determine new roots and each new root spontaneously generates their individual web-shaped subnets. The heuristic method describes the variant-hop algorithms. With a constant k, a counter variable v, and return variable r as parameters, the variant-hop algorithm generates appropriate roots locally and evenly configures the subnet size. Computer simulation shows that this method achieves good network scalability and generates an efficient scatter net configuration for Bluetooth-based multihop sensor networks.

Blueweb is a self-organising Bluetooth-based multihop network equipped with a scatternet formation algorithm and a hybrid routing protocol. The hybrid routing protocol combines the reactive method globally and the proactive method locally to discover the optimal path for packet transmission. This protocol can be configured for a particular network through adjustment of a single parameter, the number of routing tier. A global configured method is proposed by the authors to determine the desired configuration for Blueweb routing protocol. The global configured method is used in the route master and designs three blocks, including the traffic generator, the query packet estimator and the global tier decision blocks. The traffic generator block uses a uniform end-to-end traffic model in each master to generate the query packets for various N-tiers. The query packet estimator block measures the local and global query packets to compute the local query probability. The global tier decision block uses the parameter of local query probability to determine the proper number of routing tier. Computer simulation results show that this method can efficiently improve the routing performance and make the routing tiers configurable for a Blueweb routing protocol.

The mobile ad hoc networks (MANETs) have received a lot of attention recently. While many routing protocols have been proposed for MANETs based on different criteria, few have considered the impact of multi-rate communication capability that is supported by many current WLAN products. Given a routing path, this paper provides an analytic tool to evaluate the expected throughput of the route, assuming that hosts move following the discrete-time, random-walk model. The derived result can be added as another metric for route selection. Simulation results are also presented.

A computer simulation study on both coverage and capacity performance of a distributed antenna based CDMA system is presented. Wideband direct sequence spread spectrum signalling with a perfect RAKE receiver is assumed. Computer simulations are used to evaluate the distribution of received signal strength in a single cell architecture, and the distribution of received signal's SIR in a cellular architecture, for both a central antenna based system and a distributed antenna based system. It is found from our simulation that a distributed antenna based system has the potential to provide larger coverage area and higher capacity as compared with a central antenna based system.