Mini Slots Research Articles

OPTIMIZATION OF ENERGY EFFICIENCY IN MULTI-CHANNEL CO-OPERATIVE SPECTRUM SENSING IN COGNITIVE RADIO NETWORKS

In this paper, the focus is on energy efficiency in cooperative spectrum sensing in cognitive radio networks by considering multiple channels in a slotted time scenario. The sensing time consists of mini slots. A secondary user uses a mini-slot to sense a channel. Considering multiple channels, throughput, energy consumption, and, finally, energy efficiency are calculated. Additionally, the optimal number of mini-slots are obtained regarding throughput and energy efficiency using the particle swarm optimization algorithm. Simulation results are presented for the algorithms considered in this paper.

Simulation study for efficiency optimization of multi-beam klystron output cavity

Increasing klystron tubes’ efficiency is essential in developing new-generation colliders and free-electron lasers. Different factors can affect the efficiency of a multi-beam klystron. One of the significant factors is the electric field symmetry inside cavities, especially in the output section. In this research, two different types of couplers are investigated in the extraction cavity of a 40-beam klystron. The first approach is a single slot coupler, which is frequently utilized and easier to fabricate but disturbs the electric field symmetry inside the extraction cavity. The second method has a more complex structure with symmetric electric fields. In this design, the coupler consists of 28 mini slots on the inner wall of the coaxial extraction cavity. Both designs are evaluated via particle in cell simulations, and the results exhibit around 30% more power extracted from the structure with a symmetric field distribution. The symmetric structures can also decrease the number of back-streamed particles by up to 70%.

An energy-efficient command broadcast protocol in dynamic WSNs

In wireless sensor networks (WSNs), a sink must broadcast periodically a command message to a group of nodes or all nodes to control the operation of the network. However, the sparse distribution and limited resources of nodes bring difficulties for efficient broadcasting. In this paper, we propose an energy-efficient command broadcast protocol based on the construction of a spanning tree which includes maximizing the number of leaf nodes, and the allocation of one sharable slot to each tree level. The sharable slot that allocates to tree level will be divided into multiple mini slots, and non-leaf nodes at the same level will compete for broadcasting; in this way, collision can be reduced. Moreover, a node that moves to another level can use the sharable slot allocated to the new level without reallocating the slots. Extensive simulations prove that this approach not only achieves high reliability of message delivery but also energy efficiency.

Joint User-Slice Pairing and Association Framework Based on H-NOMA in RAN Slicing.

Multiservice cellular in Radio Access Network (RAN) Slicing has recently attained huge interest in enhancing isolation and flexibility. However, RAN slicing in heterogeneous networks (HetNet) architecture is not adequately explored. This study proposes a pairing-network slicing (NS) approach for Multiservice RAN that cares about quality of service (QoS), baseband resources, capacities of wireless fronthaul and backhaul links, and isolation. This intriguing approach helps address the increased need for mobile network traffic produced by a range of devices with various QoS requirements, including improved dependability, ultra-reliability low-latency communications (uRLLC), and enhanced broadband Mobile Services (eMBB). Our study displays a unique RAN slicing framework for user equipment (UE) for joint user-association. Multicell non-orthogonal multiple access (NOMA)-based resource allocation across 5G HetNet under successive interference cancelation (SIC) is seen to achieve the best performance. Joint user-slice pairing and association are optimization problems to maximize eMBB UE data rates while fulfilling uRLLC latency and reliability criteria. This is accomplished by guaranteeing the inter- and intra-isolation property of slicing to eliminate interferences between eMBB and uRLLC slices. We presented the UE-slice association (U-S. A) algorithm as a one-to-many matching game to create a stable connection between UE and one of the base stations (BSs). Next, we use the UE-slice pairing (U-S. P) algorithm to find stable uRLLC-eMBB pairs that coexist on the same spectrum. Numerical findings and performance analyses of the submitted association and pairing technique show they can all be RAN slicing criteria. We prove that the proposed algorithm optimizes system throughput while decreasing uRLLC latency by associating and pairing every uRLLC user in mini slots.

Stability and Dynamic Control of Underlay Mobile Edge Networks

This paper studies the stability and dynamic control of underlay mobile edge networks. First, the stability region for a multiuser edge network is obtained under the assumption of full channel state information. This result provides a benchmark figure for comparing performance of the proposed algorithms. Second, a centralized joint flow control and scheduling algorithm is proposed to stabilize the queues of edge devices while respecting the average and instantaneous interference power constraints at the core access point. This algorithm is proven to converge to a utility point arbitrarily close to the maximum achievable utility within the stability region. Finally, more practical implementation issues such as distributed scheduling are examined by designing efficient scheduling algorithms taking advantage of communications diversity. The proposed distributed solutions utilize mini slots for contention resolution and achieve a certain fraction of the utility optimal point. The performance lower bounds for distributed algorithms are determined analytically. The detailed simulation study is performed to pinpoint the cost of distributed control for mobile edge networks with respect to centralized control.

Multi slot-throughput tradeoff in an improved energy detector based faded cognitive radio network

In this paper, the impact of a multi slot based cooperative spectrum sensing (CSS) on the performance of a cognitive radio (CR) network has been investigated. Each CR user, equipped with an improved energy detector (IED), uses a number of mini slots of the sensing time to perform the spectrum sensing. Each CR uses OR logic to combine the sub local decisions generated in each mini slot to obtain a local decision at CR level. Local decisions are sent to fusion centre (FC) over reporting channel. The FC obtains a final decision about the presence of primary user (PU) by combining the local decisions using a fusion rule: Majority or Maximal Ratio Combining. The performance of the CSS is assessed in terms of detection probability and false alarm probability considering both the sensing and reporting channels are Rayleigh faded. Furthermore, the impact of a number of sensing slots and IED parameter on throughput of CR network is also evaluated under the proposed spectrum sensing scenario. Impacts of several sensing parameters such as sensing channel SNR and reporting channel SNR on the performance of CR network are also evaluated. Performances of two fusion rules under study are compared. Effect of sensing error and synchronisation error is indicated. Further the study is extended for independent but non identically distributed (i.n.i.d.) Rayleigh faded channels as well as for a multiple PU scenario also.

Efficient Patient Care Through Wireless Body Area Networks—Enhanced Technique for Handling Emergency Situations with Better Quality of Service

Wireless body area networks (WBAN) is a wireless network of sensors placed in and around the human body for monitoring the patient conditions remotely. The goal of WBAN networks is to report the patient condition to the monitoring system with maximum reliability and minimum delay and deliver the life critical data in the emergency situation with utmost priority. The proposed MAC protocol is aimed at delivery of emergency packets with maximum reliability and minimum delay through the introduction of mini slots in the beacon enabled superframe for exclusive transmission of the same. To improve the packet delivery ratio of the normal packets and decrease the energy consumption of the low data rate nodes, a packet rate based scheduled slot allocation is added to this protocol. Extensive simulations show that the proposed protocol is able to achieve nearly 98% packet delivery ratio and less than 100 ms delay for emergency packets. By varying the number of allocated scheduled slots based on the packet rate of the nodes, the proposed protocol has shown improved performance in the packet delivery ratio (93%) of normal packets as compared to IEEE 802.15.6 (85%), also the energy consumption of low data rate nodes has decreased by 64%. The results show that the proposed protocol is successful in realizing much better delay and packet delivery values for emergency and normal packets.

Multi-slot based spectrum sensing with improved energy detector for cognitive radio network in presence of Rayleigh fading

In this paper, the performance of multi-slot based spectrum sensing is investigated in a cooperative scenario where each cognitive radio (CR) user is equipped with an improved energy detector (IED). Two levels of fusion are employed: (i) sub-local decisions obtained in multiple mini slots are combined using OR logic fusion at a CR to obtain a local decision (ii) local decisions from CRs are combined using Majority logic fusion at FC to obtain final decision about the presence of PU. Both the sensing channel (S-channel) and reporting channel (R-channel) are assumed to be Rayleigh faded. Each CR sends its local decision over R-channel to FC after BPSK modulation. The performance of the cooperative spectrum sensing (CSS) using multi-slot and IED is assessed in terms of detection probability and false alarm probability. Furthermore, throughput of a CR is also evaluated under the proposed spectrum sensing scheme. Novel analytical expressions for the detection performance are developed. Performance of multi-slot based sensing is also compared with spectrum sensing without slotted sensing time. Impact of several sensing parameters such as sensing threshold, number of mini-slot, sensing channel SNR (SSNR), reporting channel SNR (RSNR) and IED parameters (p) on the detection performance of CR is indicated. The impact of multi-slot and IED parameter on throughput is also investigated.

DEC-MAC: delay- and energy-aware cooperative medium access control protocol for wireless sensor networks

This paper deals with two critical issues in wireless sensor networks: reducing the end-to-end packet delivery delay and increasing the network life- time through the use of cooperative communications. Here, we propose a delay- and energy-aware coop- erative medium access control (DEC-MAC) protocol, which trades-off between the packet delivery delay and a node's energy consumption while selecting a cooper- ative relay node. DEC-MAC attempts to balance the energy consumption of the sensor nodes by taking into account a node's residual energy as part of the relay selection metric, thus increasing the network's lifetime. The relay selection algorithm exploits the process of elimination and the complementary cumulative dis- tribution function for determining the most optimal relay within the shortest time period. Our numerical analysis demonstrates that the DEC-MAC protocol is able to determine the optimal relay in no more than three mini slots. Our simulation results show that the DEC-MAC protocol improves the end-to-end packet

Providing Balanced Throughput and Fairness Using Random Ranks and Mini Slots at MAC Layer in Ad hoc Networks

Ad hoc networks offer infrastructure free operation, where no entity can provide reliable coordination among nodes. Medium Access Control (MAC) protocols in such a network must overcome the inherent unreliability of the network and provide high throughput and adequate fairness to the different flows of traffic. In this paper, we propose a MAC protocol that can achieve an excellent balance between throughput and fairness. Our protocol utilizes control-message handshake similar to IEEE 802.11. The protocol makes use of granule time slots and sequence of pseudo random numbers to maximize spatial reuse and divide the throughput fairly among nodes. We have demonstrated the performance of this protocol using simulation with fixed topologies. Our simulation results include a detailed comparison between the proposed protocol and existing protocol that has been shown to excel in terms of throughput or fairness.

Randomly Ranked Mini Slots for Fair and Efficient Medium Access Control in Ad Hoc Networks

Ad hoc networks offer infrastructure-free operation, where no entity can provide reliable coordination among nodes. Medium Access Control (MAC) protocols in such a network must overcome the inherent unreliability of the network and provide high throughput and adequate fairness to the different flows of traffic. In this paper, we propose a MAC protocol that can achieve an excellent balance between throughput and fairness. Our protocol has two versions: Randomly Ranked Mini Slots (RRMS) utilizes control-message handshakes similar to IEEE 802.11. Randomly Ranked Mini Slots with Busy Tone (RRMS-BT) is the better performer of the two, but requires a receiver busy tone. The protocol makes use of granule time slots and sequences of pseudorandom numbers to maximize spatial reuse and divide the throughput fairly among nodes. We demonstrate the performance of this protocol using simulation with fixed and random topologies and show that these results are robust to difficult network configurations and unsynchronized clocks. We further develop novel metrics of long-term and short-term fairness for rigorous performance evaluation. Our simulation results include a detailed comparison between the proposed protocol and existing protocols that have been shown to excel in terms of throughput or fairness.