The next-generation IEEE 802.11be network introduces advanced features such as Multi-Link Operation (MLO) and Enhanced Orthogonal Frequency Division Multiple Access (Enhanced OFDMA), along with a new Multiple Resource Unit (MRU) mechanism that improves spectrum efficiency for multiple users under strict latency constraints. This paper proposes a QoS-aware downlink scheduling mechanism, which jointly considers the MRU type-index mapping and real-time channel conditions to optimize resource allocation in environments with heterogeneous device coexistence. Unlike existing approaches, which overlook the feasibility of MRU allocation under IEEE 802.11be constraints, the proposed scheme achieves significant improvements in total network throughput and spectrum utilization, as demonstrated through simulation. These results highlight the proposed scheduling approach as a practical and scalable solution for next-generation low-latency wireless communication.

In this paper, we consider Switched-Delay-Lines (SDL) constructions of optical priority queues by using optical (bufferless) crossbar switches and optical fiber delay lines. In a priority queue, each packet is associated with a priority upon its arrival, the highest-priority packet is sent out from the queue whenever there is a departure request, and the lowest-priority packet is dropped from the queue whenever there is a buffer overflow. Given any system for SDL constructions of optical priority queues, the main research problem is twofold: (i) the design of the routing policy performed by the optical crossbar switches; (ii) the choice of the delays of the optical fiber delay lines. Sarwate and Anantharam are the first to propose a feedback system consisting of an optical$(M+2)\times (M+2)$crossbar switch and M optical fiber delay lines (seeFigure 1inSection I) for SDL constructions of optical priority queues, and they have shown that the largest buffer size that can possibly be achieved by using such a feedback system is$2^{M}$. However, whether this theoretical buffer size$2^{M}$can be achieved or not remains an open research problem. Currently, the best result in the literature was obtained by Cheng et al. and the achieved buffer size is$2^{O(\sqrt {\alpha M})}$, where$\alpha $is a constant that depends on the parameters used in their constructions. In this paper, we consider a discrete-time setting and use a feedback system consisting of an optical crossbar switch and multiple groups of optical first-in first-out (FIFO) multiplexers with delay one (FM1’s) for SDL constructions of optical priority queues under apriority-based routing policy (seeFigure 2inSection I). Our contributions are as follows: (i) We extend and generalize an important class of constructions that contains the optimal constructions in the work of Cheng et al. As a result, we achieve larger buffer sizes and less construction complexities/costs than those by Cheng et al. (ii) We obtain a closed-form expression for the maximum buffer size that is achieved by the optimal construction for the scenario that each group of FM1’s has the same number of FM1’s. (iii) Our constructions possess a salient feature, namely, fault-tolerant capability, that can tolerate the malfunctioning of some FM1’s by using the generalized results obtained in this paper. (iv) We show that our constructions can be implemented by using an optical$(M+2)\times (M+2)$crossbar switch andMoptical fiber delay lines, and achieve a buffer size$2^{O(\sqrt {\alpha M})}$, where$\alpha $is a constant that depends on the parameters used in our constructions and is better, i.e., larger, than that in the work of Cheng et al. in a very broad regime.

IEEE 802.11ax adopts orthogonal frequency division multiple access (OFDMA) technology in the physical layer to address the efficiency degradation problem as the device density increases. OFDMA allows multiple devices to transmit or receive the data from an access point (AP) at the same time by sharing available bandwidth. However, the success rate of random access is highly dependent on the number of devices. Transmission collisions will cause devices with high-priority data to experience higher transmission delays. In this paper, we design a multi-queue priority scheduler with timeslot reservation, which improves the efficiency of random access. Devices with high-priority data have a higher transmission probability. To achieve the expected access proportion, the scheduler can change the average access times of different priority devices based on the access rules and the number of queues. Thus, the proposed mechanism can not only meet the delay requirements of high-priority data but also avoid the starvation problem of low-priority data. Mathematics and simulations show that our mechanism has better throughput and delay performance in IEEE 802.11ax networks.

The use of Bluetooth Low Energy (BLE) beacons enhanced further for connectionless services such as location-specific information and navigation. With BLE 5.0, the way beacons deliver more information can move away from the current model of app-paired-to-device to a connectionless IoT. When users pass areas with installed BLE beacons, their mobile devices can receive specials, promotional contents, and discount coupons. However, the beacons are only broadcasting. This means that beacons are not able to collect information from the users with mobile devices. In this paper, we propose responsive advertising with the wait-slot scheme (RAWS) based on advertising extensions to improve the performance of the discovery process before further communications in BLE networks. Besides, we consider the energy consumption and investigate the latency-energy tradeoff with our proposed scheme. The theoretical lower bounds for both latency and energy of the discovery process as well as their tradeoff are presented. In addition, we formulate the state transition diagram for analyzing the performance of our proposed scheme. Simulation results validated by analysis results show that RAWS indeed improves the latency and the energy consumption of the discovery process in BLE networks.

Recently, application services have become more and more diversified as new technology advances. The applications of Augmented Reality (AR) have received great attention from academics and operators. However, the complex computing required for AR applications has caused service operators to face the problems of poor user experience due to insufficient computing resources. Network function virtualization (NFV) enables operators to directly establish network functions on virtual machines and can flexibly adjust the number of each virtual network function (VNF) according to users' requirements. Thus, the system can reduce unnecessary waste of resources. In addition, we use multi-access edge computing (MEC) to provide computing resources. The edge server is close to users and reduces transmission cost of the system. This paper proposes an MEC-based VNF placement and scheduling scheme for AR applications. Considering the functional topology of AR applications, the compute-intensive application can provide good service quality for a large number of users within limited resources. The simulation shows that the proposed method can maintain good service quality as the number of user requests increases.

As cloud computing services have gained popularity, users view videos on websites (e.g., YouTube) to generate high CPU resource utilization and bandwidth for video streaming data centers. However, popular videos result in power-law features to cause imbalanced resource utilization. In addition, hotspot and idle servers generate extra power consumption in data centers. Previous studies considered to satisfy the requirements of users, provide faster access rates and save power consumption. However, fewer studies considered resource utilization with different popularity videos. Therefore, this paper proposes an energy efficient virtual machine (VM) management scheme with power-law features (VMPL). VMPL predicts the resource utilization of the video in the future based on the popularity, ensures enough resources for upcoming videos, and turns off idle servers for power saving. Simulation results validated by mathematical analysis show that VMPL has the best resource utilization and the lowest power consumption compared with Nash and Best-Fit algorithms.

Bluetooth Low Energy (BLE) Beacon technology is well on the way to becoming the future of business due to its inexpensive and low-power properties. All communications in BLE networks must involve neighbor discovery process (NDP) in the first place since a BLE device needs to create a connection or exchange information with its neighbors. Thus, the performance of the discovery latency is a challenging issue to be addressed for integrating BLE into the Beacon application development as the number of BLE devices increases. In this paper, we propose a twoway communication with wait-slot scheme (TCWS) to minimize the probability of collision occurring on the response frames of BLE devices and improve the latency of NDP. We formulate the state transition diagram for analyzing the performance of our proposed scheme. The results show that TCWS provides much better performance in terms of the probability of collision and the discovery latency in dense BLE networks.

In IEEE 802.16 specifications, a CRC field can be attached in the rear of a WiMAX MPDU. Thus, each intermediate node (relay node or base station) in an 802.16-based multihop network can perform error detection on a received WiMAX MPDU. On the sender, the ARQ mechanism will be enabled to retransmit the MPDU if a transmission error occurs and an ACK message cannot be received. However, the ARQ mechanism is unsuitable for real-time traffic due to the delay consideration and the CRC field becomes an option to reduce the overhead of a WiMAX MPDU. Once the CRC field is removed from a WiMAX MPDU, the error occurrence cannot be detected by the intermediate nodes in time, and the erroneous data is still forwarded in the network but discarded by the destination. The resources of nodes in a network are wasted. Hence, the error detection mechanism should be retained for real-time traffic, but the overhead of CRC should be reduced. In this paper, we study an efficient discrete-error-checking scheme (DECS) to reduce the CRC overhead for real-time traffic. The DECS only needs several CRC checking bits, which are attached behind some WiMAX MPDUs. The DECS can efficiently provide the error detection for the intermediate nodes to discard these erroneous and useless data early. Thus, the utilization of node resources and wireless bandwidth can be improved significantly.

ABSTRACT In order to satisfy quality‐of‐service requirements for real‐time multimedia applications over wireless networks, IEEE 802.11e has been proposed to enhance wireless‐access functionalities. In IEEE 802.11e, collisions occur frequently as the system load becomes heavy, and then, the latency for successfully transmitting data is lengthened seriously because of contention, handshaking, and backoff overheads for collision avoidance. In this paper, we propose a fragment‐based retransmission (FBR) scheme with quality‐of‐service considerations for IEEE 802.11e‐based wireless local area networks. Our FBR can be used in all proposed fragmentation‐based schemes and greatly decrease redundant transmission overheads. By utilizing FBR, the retransmission delay will be significantly improved to conform strict time requirements for real‐time multimedia applications. We develop an analytical model and a simulation model to investigate the performance of FBR. The capability of the proposed scheme is evaluated by a series of simulations, for which we have encouraging results. Copyright © 2011 John Wiley & Sons, Ltd.

Wireless mesh networks (WMNs) is a promising technology that provides broadband wireless Internet access. It is one of the most important challenges to establish multiple connections among stations (STAs) in WMNs. In this paper, we propose a novel automatic mesh scheme (AMS) of layer 2 to form WMN in IEEE 802.11 wireless networks. AMS establishes multiple connections from a STA to neighbor STAs and determines proper routing path effectively, where three objectives are optimized, i.e., minimizing the average hop count, balancing traffic load and without modifying the communicating procedure in IEEE 802.11 standard. AMS owns self-organization capacity, establishes multiple connections and determines routing path automatically. Our AMS only uses simple software functions without the cost of extra hardware overhead. Simulation results show that the proposed scheme significantly improves the system performance. Importantly, AMS that works very well has been implemented and exhaustively tested in a realistic test-bed.

Based on IEEE 802.16 specifications, the convergence sublayer (CS) of 802.16-based networks provides the function for heterogeneous upper layer protocols. The CS can encapsulate such as IP packets with variable lengths or ATM cells with fixed length in its MAC PDU and usually adds a CRC-32 field to the rear of the MAC PDU. Based on the CRC-32, each 802.16 relay node or BS can detect error occurrence on a MAC PDU and use ARQ mechanism to retransmit the corrupt MAC PDU. However, for real-time streaming (e.g., UDP streaming), the ARQ mechanism is not required and the CRC-32 is also removed. Once CRC-32 is removed from the MAC PDUs, PDU error will not be detected by the intermediate nodes in time and these corrupt IP packets or ATM cells will be still forwarded in the networks to waste radio bandwidth. Hence, the error detection mechanism could be maintained, but the large overhead of CRC-32 should be reduced for real-time streaming. In this paper, we propose an efficient discrete-error-checking scheme (DECS) to reduce the overhead of error detection for real-time streaming. The proposed DECS only needs a few checking bits inserted in the MAC PDU, and it can efficiently provide the error detection function. Moreover, a chase mechanism concurrently works on each relay node and BS to early discard these corrupt and useless IP packets or ATM cells. The concept of the DECS including the chase mechanism can be extensively implemented in many wire and wireless multi-hop networks to further improve bandwidth utilization.

IEEE 802.15.4 standard is designed to achieve low-power transmissions in low-rate and short-distance wireless personal area networks (WPANs). For the sake of reducing the control overheads, the modified CSMA/CA protocol used by 802.15.4 does not have the hidden device protection mechanism, such as RTS/CTS mechanism. Previous studies indicate that the probability of any two devices in a infrastructure network unheard of each other is around 41%. Therefore, the hidden device problem (HDP) results in inefficient data transmission and serious power consumption issues in WPAN. In this paper, we propose a cross-layer detection and allocation (CL-DNA) scheme to solve the HDP in IEEE 802.15.4 without the cost of extra control overhead in data transmissions. The proposed scheme detects hidden device relationships based on the overlapped signals and then allocates the hidden devices into distinct sub-periods for transmissions. Simulation results show that the proposed scheme significantly improves the goodput, and with reduction in the MAC delay and the power consumption.

IEEE 802.11 wireless networks utilize a hard handoff scheme when a mobile station is travelling from one area of coverage to another within a transmission duration. When the station is running a real-time multimedia application receiving data from the wireless network, in each pair of neighboring MAPs, contention scheme is used to transmit data. The latency for successfully transmitting data is seriously lengthened so that the deadlines of data frames are missed with high probabilities. In this paper, we propose a fuzzy-based cross-layer transmission (FCLT) scheme with QoS considerations for IEEE 802.11 mesh wireless networks, which utilizes the grey model and the fuzzy theorem. In the handoff procedure, some ratio of real-time data frames will be relayed to the next MAP based on received signal strength indication of PHY layer and contention window of MAC layer, which can meet the minimal QoS requirements. By utilizing FCLT, the ratios of data frames missing deadlines will be significantly improved to meet timing requirements for real-time multimedia applications. We develop a simulation model to investigate the performance of FCLT. The capability of the proposed scheme is evaluated by a series of experiments, for which we have encouraging results.

In order to satisfy QoS requirements for real-time multimedia applications over wireless networks, IEEE 802.11e has been proposed to enhance wireless-access functionalities. However, as system load is heavy, collisions occur most often and then the time needed for successfully transmitting data is lengthened seriously due to contention, handshaking, and long backoff processes for collision avoidance. It is important to keep QoS requirements satisfied. Therefore, we propose a fragment-based retransmission (FBR) scheme with QoS considerations for IEEE 802.11 wireless local area networks (WLAN). By utilizing IEEE 802.11e with FBR, the retransmission delay will be improved to conform strict time requirements for real-time multimedia applications. The capability of the proposed scheme is evaluated by a series of experiments, for which we have encouraging results.

The wireless mesh network (WMN) has been an emerging technology in recent years. Because the transmission medium used in networking mesh APs is radio, WMN is not only easy and cost effective in deployment, but also has good scalability in coverage area and capacity. The IEEE 802.11 MAC protocol has been adopted as the de-facto medium access control. We assess the fitness of the IEEE 802.11 over WMN, and contend that it is really necessary to be changed so that it can be adapted to WMN. In this paper, we propose the MASH (medium access with scheduling) protocol, which schedules the packet transmission between mesh APs in a fully-distributed manner. Since out-of-band signaling is used and scheduling is executed to solve the hidden terminal problem and exposed terminal problem, the simulations show that both the network throughput and end-to-end delay can be significantly improved in this wireless multi-hop network.

This paper presents a system prototype to help elder persons being aware of changes in terrain ahead of them. Ultrasonic signal is used for the detection of terrain changes because of its stability in air transmission speed and its simplicity and cost in hardware designs. The prototype is designed and built using commercial-off-the-shelf (COTS) components with an 8051 microprocessor. It can detect obstacles of heights no more than 10 cm three steps away.

Based on IEEE 802.15.4 low-rate wireless personal area networks (LR-WPANs), this paper proposes a memorized backoff scheme (MBS) with the exponential weighted moving average (EWMA) approach to dynamically adjust the size of the contention window. The proposed scheme can be implemented in the standard IEEE 802.15.4 medium access control (MAC) protocol without adding any new message type and without modifying the communicating procedure. An analytic model and a simulation model are developed to evaluate the performance of IEEE 802.15.4, MBS and MBS+EWMA. The numerical results indicate that in terms of goodput, completion rate, average MAC delay, average queuing delay and average number of collisions for each data frame, our proposed scheme significantly outperforms the standard IEEE 802.15.4 backoff scheme.

The IEEE 802.11 standard and enhanced amendments have defined fourteen transmission rates (1/2/5.5/6/9/11/12/18/22/24/33/36/48/54 Mbit/s) for mobile stations to transmit and receive data frames. With the characteristic of modulation schemes, a higher level modulation scheme requires a higher signal-to-noise ratio (SNR) and, consequently, the data rate is inversely proportional with the transmission distance. Using a higher level modulation scheme, a higher network throughput can be expected; however, the frame error probability will also become higher. Doubtlessly, it is an open issue of selecting a proper modulation scheme for a pair of mobile stations in a time-varying indoor environment. This paper proposes a safe multiple access-rates transmission (SMART) scheme for enhancing the reliability of data transmission in the IEEE 802.11 multi-rate infrastructure wireless networks. The SMART scheme provides reliable transmission by reserving a retransmission period, which immediately follows the transmitted frame and is estimated from a lower transmission rate, for each transmitted frame. If any error occurs on the transmitted frame, the sender will retransmit it right away by using a lower transmission rate to make sure of successful retransmission. Otherwise, the reserved period will be taken by the access point (AP), which often has the longest waiting queue and is the bottleneck in infrastructure wireless networks. The efficiency of the proposed SMART scheme is evaluated by simulation. Simulation results show that the derived performance of the SMART scheme is significantly better than standard under the real environment with asymmetric traffic load.

In IEEE 802.11 infrastructure wireless local area networks (WLAN), all mobile stations (STAs) are coordinated by an access point (AP), which is a static device and plays the role of the bridge between wired and wireless networks. Such coordination is achieved by restricting all STAs to access the channel listened by AP. Within the 2.4 GHz unlicensed industry, science, and medicine (ISM) band defined in the IEEE 802.11 2.4 GHz physical layer (PHY) specifications, three of fourteen channels, which are independent and exclusive, can be used to transfer data packets at a same area concurrently. However, in most small/medium enterprises or home environments, one AP is sufficient for covering whole service area. This implies that the other two channels' capacity has being wasted by the single channel operation defined in standard. In order to overcome the drawback, we propose a new and simple CSMA based media access control (MAC) protocol, named wireless switch protocol (WSP), for promoting the IEEE 802.11 aggregate network throughput. This is simply achieved by allowing any pair of STAs in WLAN to exchange data packets in another idle channel after their handshaking with each other in the common channel, which is specified by AP. Simulation results show that the total network throughput of WSP is obviously depending on the time taken by the changing frequency channel and the intranet and Internet traffic distribution, where the intranet and Internet mean the data exchanged between mobile STAs, and between STA and wired host, respectively. If all data packets are intranet traffic and the traffic load is heavy, the improving ratio of derived goodput of proposed WSP and that of the IEEE 802.11 standard approximates 400%. In the worse case that all traffic is Internet traffic, the proposed WSP still obtains the similar throughput as that of IEEE 802.11 standard.