Bluetooth Low Energy (BLE) advertising network has been widely employed in various monitoring applications, where advertiser sensors update their time triggered (TT) or event triggered (ET) status in an advertising mode to a continuously scanning central scanner. This paper addresses the problem of minimizing the age of information (AoI) for monitoring over a BLE advertising network. Firstly, we propose a packet error rate-conditioned AoI model and derive the average Aol and peak AoI (PAol) in closed form. It is found that the conditional average Aol and PAol for TT traffic are smaller than those for ET traffic at the same traffic rate, λ. Additionally, when λ exceeds the advertising rate, these metrics are further derived in closed form under a zero-waiting policy, ensuring that fresh status is available at each advertising event. Secondly, we formulate two optimization problems aimed at minimizing the average Aol and PAol under zero-waiting policy, constrained by the advertising intervalTa. To minimize the average Aol, we propose two algorithms to compute the optimal exact and approximate values ofTa, utilizing a proposed bisection method and a derived approximate closed-form solution. To minimize the PAol, we also derive a closed-form solution, which is found sharing a similar structure to our derived approximate solution for minimizing the average AoI. Extensive simulation results demonstrate the accuracy of the proposed AoI model and the derived optimal solutions.

Wireless audio transmission has always been the focus of Bluetooth application scenarios. Future audio use cases, such as multistreaming to assist stereo imaging experiences, broadcast audio sharing, hearing aid support, etc., have higher requirements for Quality of Service (QoS). Bluetooth low-energy (BLE) Audio is considered to be a replacement for the Bluetooth classic audio standard in the next generation of audio applications. In low-energy (LE) Audio, the audio data is carried by connected isochronous streams (CISs), which is a logical transport that enables the transmission of isochronous data. However, until now, the performance of CIS-based LE Audio has not been fully analyzed. In this article, we propose a mathematical model to evaluate the performance of CIS, such as packet loss rate (PLR), throughput, backlog, delay, and average power consumption. In addition, the feasibility of multihop transmission based on CIS is explored, and the model is extended to analyze the end-to-end PLR and throughput. Finally, the accuracy of the proposed model is verified by simulation results, and the relationship between CIS parameters and performance is analyzed, providing guidance for parameter selection in LE Audio applications.

In this paper, we consider roadside infrastructure-to-roadside infrastructure communications in a vehicular ad hoc network. A remote roadside unit (RSU), which does not have connection to the backbone network, needs to send its data traffic to a central RSU (which has backbone connection) by using help from vehicles passing by. Cost is assigned to information transmission energy consumption, as well as possible violation of a soft delay bound. For each passing vehicle, the remote RSU needs to decide whether or not to ask for help from the vehicle, with a target at a minimal rate of cost. We derive an optimal decision strategy of the remote RSU, which is shown to have a conditional pure-threshold structure, i.e., when a vehicle arrives at the remote RSU, if the queuing delay of the data traffic at the remote RSU is above a threshold, it is optimal for the remote RSU to ask for help from the vehicle, with a condition that the vehicle's speed satisfies a requirement. We also provide a method that can theoretically derive the threshold. The conditional pure-threshold structure makes our derived strategy very easy to implement with very low computation complexity.

The next generation Internet of Things (IoT) is expected to support extremely diverse applications and terminals, which requires the massive connectivity. Unfortunately, current mobile communication systems with orthogonal multiple access technique can hardly satisfy this demand. On the other hand, the narrow band property has become the trend of the next generation IoT, however, the problem of interference alleviation in the narrow band system is difficult to be resolved. Recently, the sparse code multiple access (SCMA), a non- orthogonal multiple access technique for 5G, shows the obvious improvement in user connectivity and system capacity. After carrier aggregation brought into the future network, The IoT could offer the frequency hopping mechanism larger bandwidth resources. In this paper, by introducing frequency hopping mechanism to the SCMA, a frequency-hopping based sparse code multiple access (FH-SCMA) multiple access technique is proposed to meet the demand of both massive connectivity and the improvement in the interference alleviation. Simulation results show that the FH-SCMA obtains a spectrum efficiency gain of almost 300% compared with the frequency division multiple access (FDMA) based IoT system with frequency-hopping, and the performance of interference alleviation can also be significantly improved by about 2 to 5 times over the FDMA with frequency hopping.

Due to the dramatic growth of human demands for wireless business, wireless local area network (WLAN) achieves rapid popularization and world-wide development recently. In order to improve the efficiency of the next generation WLAN, especially in the dense deployment scenarios, IEEE sets up a new task group named TGax to draft out the amendment 802.11ax in 2014. The motion of TGax confirms that Enhanced Distributed Channel Access (EDCA) is still one important method of channel access in 802.11ax. In this paper, we show that the traditional EDCA mechanism faces the fairness issues, including intra-node problem and inter-node problem, in the next generation WLAN. Thus, we propose an enhanced virtual collision management mechanism named EVCM by introducing access weight factor and rate of successful access to improve fairness of EDCA. Simulation results show that the EVCM significantly improves both the intra-node fairness and inter-node fairness in the dense deployment scenarios. Especially, it obtains ten-fold intra-node fairness compared with EDCA, and three times inter-node fairness than that in EDCA.

The ever-increasing data demands and the density of wireless nodes require higher data rate in wireless networks. To satisfy the requirement, it is necessary to propose novel medium access control (MAC) protocols to enhance multiuser channel access and multiuser data transmission in wireless network. The existing studies prove that full-duplex (FD) is able to improve the network capability without any extra bandwidth. However, there are few studies focusing on multiuser FD MAC protocol design for the next generation wireless networks. In this paper, a multiuser FD MAC protocol named as MU-FuPlex is introduced based on our proposed system model, and the interference information collection, FD transmit opportunity (FD-TXOP) mechanism, and frame format design for MU-FuPlex are discussed. To the best of our knowledge, this is the first work focusing on the combination of multiuser MAC and FD technology. The simulation results confirm that MU-FuPlex significantly improves the saturation throughput up to 200% compared with IEEE 802.11 DCF.

The increase in collision and interference induced by the network densification poses the intractable challenge of improving network throughput. Channel reservation and cooperative transmission, two schemes improving the medium access control (MAC) efficiency and transmission reliability respectively, have drawn considerable attention. Joint optimization of reservation and cooperation is theoretically proved to be promising in improving the network throughput in our recent study. However, up to now no practical MAC protocol is proposed to evaluate its effectiveness. In this paper, we propose an ALOHA-based joint reservation and cooperation MAC (AJRC-MAC) protocol which adopts the reservation-based channel access and enables the cooperative transmission simultaneously for the dense wireless network. Simulation results evaluate the effectiveness of the joint reservation and cooperation, and show that a throughput gain of 330%, 250%, 130% can be achieved respectively for AJRC-MAC compared with the basic MAC, cooperation- only MAC and reservation-only MAC.

As the most widely used standards for wireless local area network (WLAN), IEEE 802.11 standards are continuously amended by introducing new techniques so as to meet the increasing demands. In order to verify the performance of amended protocols, network simulation is considered as a significant method. However, as far as we know, current simulation tools are only for either media access control layer (MAC) or physical layer (PHY). The separate simulation of MAC and PHY can hardly evaluate the performance of IEEE 802.11ax in whole system level for authenticity and objectivity. Hence, the next generation WLAN (IEEE 802.11ax) requires integrated system simulation to take impacts of both MAC and PHY techniques into account. Moreover, IEEE 802.11ax introduces some new techniques, such as orthogonal frequency division multiple access (OFDMA), multi-user multiple input multiple output (MU- MIMO) and non-continuous channel bonding. In this paper, we design and further implement the integrated link-system level simulation platform, which makes it possible to evaluate the new technologies for IEEE 802.11ax. Moreover, we propose a MAC protocol combining OFDMA, MU-MIMO, non-continuous channel bonding and link adaptation and further evaluate its performance. Finally, we validate performance gains of IEEE 802.11ax through simulation, and the simulation results show that IEEE 802.11ax has obviously higher throughput, better quality of service (QoS) and higher multi- channel efficiency. To the best of our knowledge, this is the first work to design and implement simulation platform for IEEE 802.11ax with an integrated link- system level framework.

As one of the significant driving forces of the future broadband heterogeneous networks (5G), the Next Generation WLAN (NGW) has been initiated following the 802.11 HEW (High-Efficiency WLAN) study group with a focus on improving spectrum efficiency and area throughput. However, Low-Rate-Links (LRLs) severely degrade the overall wireless network performance, particularly under the dense environments in the NGW. To improve the data rate of wireless links, cooperation communication is proposed to divide a low-rate-link into multiple successive wireless links with much higher data rate over the same frequency channel, which is denoted as `Serial-Coop'/`SC' strategy. However, the existing `Serial-Coop' strategy suffers from the disadvantage of large cumulative delay because the packets are relayed within two successive timeslots. In this paper, a distributed Multi-channel MAC protocol with Parallel Cooperation is proposed for the NGW, called PC-MMAC, to initiate concurrent cooperation communications over multiple frequency channels in a distributed fashion. Then, an approximate analysis on the upper bound of saturation throughput gain is derived. Further, an enhanced mechanism is proposed to strengthen the robustness of PC-MMAC, by dynamically adjusting the cooperation strategy based on the number of available data channels. Extensive simulation results show that the saturation throughput of PC-MMAC outperforms `Serial-Coop' strategy and `Non-Coop' scheme1by 25% and 33% respectively.

Due to the increasingly scarce spectrum resources and densely deployed wireless networks, how to increase the spectrum utilization efficiency becomes a hot topic. Channel reservation and cooperative transmission have shown great potential to improve the spatial reuse and network capacity. However, it is difficult to avoid the shortcomings that simply adopting either scheme. In this paper, we propose the concept of reserved cooperative link and investigate the joint optimization of channel reservation and cooperative transmission to improve the network capacity. The concept of area capacity is introduced to characterize the spectral efficiency. After deriving its closed-form expression, the area capacity can be optimized by jointly selecting the optimal helper and employing the optimal reservation zone. Simulation results well validate our analysis, and show that the optimal reservation zone size is reduced by 30% compared with direct transmission with channel reservation. The corresponding optimal area capacity is significantly improved, and a gain of 140% can be obtained for the path loss exponent of 4.

In this paper, a heuristic clique based spatial time division multiplexing access (STDMA) scheduling algorithm is proposed for concurrent transmission in millimeter wave networks. Firstly, based on the physical interference model an interference level caused by one transmission request to another is defined, which transforms the SINR condition to a summation form. Then, an un-directional conflict graph is constructed, a feasible clique of which is proved corresponding to a feasible concurrent transmission requests group in one timeslot. Finally, a heuristic clique based STDMA scheduling algorithm is proposed to find the maximum feasible concurrent scheduled transmission requests in one timeslot. Extensive simulations are conducted, and the simulation results show that compared to the existing blind scheduling algorithm, the spatial sharing gain is improved by 11%-36%.

In ad hoc networks, interference is an important factor limiting the network capacity. Imposing a reservation zone around each receiver has been widely considered to mitigate the interference. A larger reservation zone can decrease the interference, but it also lowers the spatial reuse for reduced simultaneous transmissions. Therefore, there exists an optimal reservation zone to maximize the network capacity. In this paper, rate adaptation is brought to improve the channel reservation scheme, and network capacity achieved by jointly optimizing the data rate and reservation zone is investigated for spread-spectrum (SS) ad hoc networks. Compared to the transmission capacity with fixed data rate assumption, analytical and numerical results show that network capacity can be significantly improved, and the capacity gain remains constant in the order of 300% for direct sequence (DS) SS networks and increases with the growing spreading factors in the range of 300-800% for frequency hopping (FH) SS networks.

In IEEE 802.11 wireless local area network (WLAN), the quality of the experience (QoE) of HTTP video streaming is seriously influenced by the restricted bandwidth and shared resources. However, to the best of our knowledge, the assessment and optimization of QoE of HTTP video streaming in WLAN have not been fully studied yet. In this paper, we propose an objective metric to assess the QoE and obtain the relationship between this metric and the achieved MAC layer throughput, which makes the MAC layer be aware of the QoE performance directly. Then, a novel admission control and MAC layer parameter configuration algorithm is proposed, which optimizes the QoE of HTTP video streaming and guarantees the throughput requirement of background traffic. Simulation results show that the proposed algorithm outperforms legacy IEEE 802.11 DCF in QoE optimization by a factor of six or more when the number of background stations is large.

ABSTRACT For a wireless ad hoc network to achieve fault‐tolerance, it is desired that the network is bi‐connected. This means that each pair of nodes in the network have at least two node‐disjoint paths between them, and thus, failure at any single node does not partition the network. In other words, in a bi‐connected network, there is nocut‐node(defined as a node such that the removal of it partitions the network). To make a connected but not bi‐connected network become bi‐connected, actions should be taken such that all cut‐nodes become non‐cut‐nodes. In this research, we propose to deal with cut‐nodes from a new perspective. Specifically, we first introduce a new concept ofremovable node, defined as a non‐cut‐node such that the removal of it does not generate any new cut‐node in the network. Then, we propose to move a removable node to a new location around a cut‐node. In this way, the cut‐node becomes a non‐cut‐node, that is, the failure of it does not partition the network anymore. Algorithms are provided (i) to identify removable nodes; (ii) to match cut‐nodes with a feasible set of removable nodes, in which all nodes can be simultaneously removed from the network without generating any new cut‐node in the network; and (iii) to derive the final location of a removable node such that its movement distance is the shortest and the associated cut‐node becomes a non‐cut‐node. The proposed algorithms do not guarantee the final bi‐connectivity but have the merits of a large success rate (almost 100% in the simulation), a small number of moved nodes, and a short total movement distance. In addition, the proposed algorithms are shown to be effective even when there are a large portion of fixed nodes in the network. Copyright © 2011 John Wiley & Sons, Ltd.