Improving Network-Assisted Roaming for Controller-Less Wi-Fi

In an infrastructure wireless LAN, the access point (AP) is responsible for connecting mobile stations (STA) and wired stations. Each access point is assigned on one channel. Traditionally, one station selects AP to connect is based on the received signal strength indicator (RSSI). This approach may cause all active mobile stations to connect to few APs and lots of contentions/collisions will occur by the Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) protocol. Consequently, the total network throughput will be degraded. Contrarily, if all STAs can be equally distributed to all APs and the signal strength of any pair of STA and connected AP is still kept in an acceptable range, the spare bandwidth in wireless LAN (WLAN) will be utilized in a more efficient way. In this paper, a novel dynamic load balance algorithm is proposed for WLAN. Simulation results show the proposed algorithm has the ability to fairly distribute all STAs among APs. Moreover, it also maximizes the average RSSI between AP and connected STAs.

There has been widespread deployment of IEEE 802.11 wireless local area networks (LANs) because of high demand from mobile terminals, such as iPod and Android terminals. With the increasing energy consumption of the wireless LANs, the development of power saving technologies incorporated into the wireless LANs have become important. In wireless LANs, access points (APs) continuously consume the power regardless of the communication. Therefore, we have proposed the Radio-On-Demand (ROD) wireless LAN, which provides power saving schemes on the basis of the utilization of wireless LANs. In this study, we particularly focus on the power saving scheme of the APs, and propose the decentralized association management of ROD wireless LANs. In our scheme, an AP assigns associated stations (STAs) to new APs before switching to sleep mode. Simulation results show that the proposed scheme can realize sufficient power saving.

This paper deals with the problem of optimal association of stations (STAs) to access points (APs) for mulicast services in IEEE 802.11 WLAN. In a multicast session, all the subscribed STAs receive the multicast data packet at the same data rate (R min ) from their respective serving APs. A higher value of R min improves the multicast throughput by completing the ongoing multicast session in lesser time. This also improves the unicast throughput as the cycle duration is shared by the unicast and multicast sessions. To provide multicast services to the STAs, we need to select a minimum cardinality subset of APs as the system message overhead depends on this cardinality. However, such a minimum cardinality subset of APs may not be possible to activate simultaneously due to the limited number of available orthogonal frequency channels. In this paper, we develop a combined greedy algorithm that selects a subset of APs with minimum cardinality for which a conflict-free frequency assignment exists and finds an association between the STAs and the selected APs that maximizes the R min value. Through simulation we have shown that the proposed algorithm selects significantly less number of APs for different R min values in comparison to the well-known metrics for multicast association like RSSI, minimum hop-distance, normalized-cost and in-range STA number.

Fair and efficient resource allocation in IEEE 802.11ah WLAN with heterogeneous data rates

We propose a Cooperative Opportunistic Automatic Repeat ReQuest (CoARQ) scheme to solve the HOL-blocking problem in infrastructure IEEE 802.11 WLANs. HOL blocking occurs when the head-of-the-line packet at the Access Point (AP) queue blocks the transmission of packets to other destinations resulting in severe throughput degradation. When the AP transmits a packet to a mobile station (STA), some of the nodes in the vicinity can overhear this packet transmission successfully. If the original transmission by the AP is unsuccessful, our CoARQ scheme chooses the station (STA or AP) with the best channel to the intended receiver as a relay and the chosen relay forwards the AP's packet to the receiver. This way, our scheme removes the bottleneck at the AP, thereby providing significant improvements in the throughput of the AP. We analyse the performance of our scheme in an infrastructure WLAN under a TCP controlled file download scenario and our analytical results are further validated by extensive simulations.

Software-Defined Network (SDN) is one of the most predominant technologies for networking in the existing and next-generation networks. SDN can conFig. , control, protect, and optimize network resources through software. The fundamental benefit of SDN is enabling the application of dynamic management. In addition, the literature shows that partitioning a Software-Defined Wide Area Network (SD-WAN) into several logical networks efficiently will optimize its performance. The main aim of paper is to design an algorithm to slice SD-WAN dynamically into several virtual networks according to the server-clients’ correlation using the Virtual Local Area Network (VLAN). The several virtual networks improve QoS of SD-WAN and reduce its broadcasting domain. The proposed framework consists of two parts. The first part is the management algorithm that finds the best server for each client; then it groups this server with their client in a dedicated logical network. The second part includes creating a VLAN for each logical network in an SD-WAN. The application of the POX controller calculates and maintains the dynamic VLAN, which will be applied by the control plan to slice the topology in the data plan. SD-WAN topology is tested before and after applying VLANs. The results show enhancement in latency by 42.85%, throughput by 4.61%, loss packet by 72% and jitter by 47.86% after applying VLAN. Finally, the greatest gain is reducing the broadcasting ratio by 77.77%. Index Terms— Virtual Local Area Network (VLAN), Software-Defined Network (SDN), Software-Defined Wide Area Network (SD-WAN), Quality of Service (QoS), OpenFlow (OF).

Automated interference detection is required for operation and management services in wireless networks as Wireless Local Area Networks (WLANs) based on IEEE 802.11 Standard since co-channel interference from other wireless transmitters occurs irregularly. We propose a new approach for detecting the presence of interference on 802.11 links. Our solution focuses on the Access Point (AP)-initiated monitoring approach without Wireless Station (STA)-initiated additional function and sniffer devices. Our approach uses the geographical distribution of the response delay of the Acknowledgment packet (ACK) to the downlink packet that AP transmitted to STAs. The proposed method consists of a continuous monitoring step and a periodical diagnosis step to measure network statistics by ACK response delay between an AP and STAs and to detect whether and where interference occurs respectively. Comprehensive simulation results show that the proposed approach has a good accuracy and low misdetection ratio for diagnosing the interference existence and location in IEEE 802.11 WLANs.

To Our Readers

Many wireless local area network (WLAN) performance estimations are done with the assumption of uniformly distributed stations (STAs). In practice, on the contrary STAs are distributed unevenly among access points (APs), causing hot-spots and under utilized APs in a wireless network. Considering a WLAN is made up of multiple APs, having some APs carrying excessive loads (i.e. hot-spots) degrades both the considered APs as well as the overall network performance. The system performance can be improved by associating incoming STAs effectively throughout the network, in a sense to balance the network load evenly between APs and relieve the hot-spot congestion. Currently employed user association method in IEEE 802.11 WLANs considers only the received signal strength of APs at STAs, and associates STAs to the closest (in signal strength sense) AP, ignoring its load and interference value.Novel user association algorithms are required for congestion relief and network performance improvement. In this work, a new distributed association algorithm taking into consideration not only the received signal strength of the APs at STAs but also AP loadings and interference is proposed. A new AP load calculation method acknowledging the interference between STAs and APs is presented. Our simulations demonstrate that the proposed algorithm can improve the overall system throughput performance more than 50% and offers a better load distribution across the network compared to conventional association algorithm.

The next generation wireless local area network (WLAN) needs to significantly improve the area throughput in high-dense deployment scenario. Orthogonal frequency division multiple access (OFDMA), considered as the key technology of the next generation WLAN, has been adopted by IEEE 802.11ax. However, most existing studies have one tricky problem: interference extension problem, i.e., the stations (STAs) placed at dispersive locations from one basic service set (BSS) access channel and transmit data simultaneously through OFDMA, thereby interfering a large area and suppressing the potential transmissions around this BSS. Unfortunately, high-dense deployment scenario exacerbates interference extension problem. This article proposes a spatial clustering group division-based OFDMA (SCGD-OFDMA) protocol, which enables the geographically close STAs to form spatial clustering groups, named SCGs. Each SCG has a leader STA and several member STAs. Each SCG’s leader STA contends for channel resources. After that, the leader STAs that successfully contending channel are scheduled by the access point one by one to trigger its member STAs to transmit uplink data by using OFDMA. Therefore, the geographical interference area is reduced and the area throughput is improved since the concurrent STAs in one SCG are located in limited area. This article theoretically analyzes the optimal SCG establishment, and throughput and area throughput of SCGD-OFDMA. Theoretical analysis is consistent with simulation results. The simulation results also show that when the number of STAs is 200 and all resource units are used for random access, SCGD-OFDMA outperforms IEEE 802.11ax and OMAX in area throughput by 56.13% and 190.97%, respectively.

IEEE 802.11ax introduces Uplink Orthogonal Frequency Division Multiple Access (OFDMA)-based Random Access (UORA), a novel feature for facilitating random channel access in Wireless Local Area Networks (WLANs). Similar to the conventional random access scheme in WLANs, UORA employs the OFDMA backoff (OBO) procedure to access the channel’s Resource Units (RUs) and selects a random OBO counter within the OFDMA contention window (OCW) range. The Access Point (AP) can determine and communicate this OCW range to each station (STA). Multiple STAs accessing RUs result in transmission failure due to RU collisions, which occur when specific RUs remain unassessed by any STA, leading to wastage. Efforts to optimize channel efficiency require minimizing both collisions and idle RU despite the challenges arising from UORA’s distributed and random nature. The Fisher-Yates shuffle algorithm introduces a random uniform distribution strategy for managing RU allocations among STAs. The results demonstrate that this approach enables STAs to access RUs in a distributed manner, effectively reducing idle and wasted RUs, especially in scenarios involving a limited number of STAs. Furthermore, this approach effectively mitigates collisions among STAs, even in scenarios with a more significant number of STAs.

Systematics distributing information quickly and effectively to improve the performance of the network is the ability to divide a large broadcast domain into several smaller broadcast domains using VLANs (Virtual Local Area Network). Broadcastdomain smaller device would limit the activities involved in the broadcast and device divides into several groups based on their functions, Pasar Rebo District Office has several village and this will be applying VLAN technology. VLAN is used as an alternative to a router that is used to divide the private network for each floor of the District Office. Where each floor has a different network with one another so that the security of the network increases. VLAN configuration used was a model of VLAN trunking. This model uses a system of VTP (Virtual Trunking Protocol) Server and Client. Switches are used as a server can divide a network of ports available. While the client can only adjust the network that has been provided by the server switch. VLAN configurations are all using Cisco Catalyst Switches, After the network is configured to use VLAN VLAN then the next step would be the author of Virtual Private Network building which serves to connect the VLANs in the District Office and the Village Office located in the District of Pasar Rebo.

In this paper, we consider the problem of association of wireless stations (STAs) with an access network served by a wireless local area network (WLAN) and a 3G cellular network. There is a set of WLAN Access Points (APs) and a set of 3G Base Stations (BSs) and a number of STAs each of which needs to be associated with one of the APs or one of the BSs. We concentrate on downlink bulk elastic transfers. Each association provides each ST with a certain transfer rate. We evaluate an association on the basis of the sum log utility of the transfer rates and seek the utility maximizing association. We also obtain the optimal time scheduling of service from a 3G BS to the associated STAs. We propose a fast iterative heuristic algorithm to compute an association. Numerical results show that our algorithm converges in a few steps yielding an association that is within 1% (in objective value) of the optimal (obtained through exhaustive search); in most cases the algorithm yields an optimal solution.

In dense wireless local area network (WLAN) environments, the haphazard deployment of WLAN devices causes them to overlap. In such situations, a coverage adaptation through transmission power control (TPC) is required. At the same time, coverage holes should be taken into consideration for connectivity maintenance among devices. In this paper, a TPC scheme is proposed that reduces overlaps in an autonomous manner, without generating target coverage holes. The problem is formulated as a target coverage problem, in which wireless stations (STAs) are treated as target points, and the transmission power is appropriately controlled by the proposed scheme. In addition, we prove that the target coverage game is a potential game, and the proposed method is guaranteed to converge to a Nash equilibrium after a finite number of iterations. In order to prevent the occurrence of coverage holes that cannot be detected by the available STA information, we propose the exclusion of coverage boundary access points (APs) from reducing transmission power, with the idea that each boundary AP always contains the region covered by it alone. The coverage boundary APs are determined through Delaunay triangulation of all APs. The proposed scheme is evaluated by performing some simulations. The simulation results indicate that the proposed TPC scheme is effective in reducing coverage overlaps without generating coverage holes.

In the case of a 3G-WLAN interworking architecture, handoff latency is mainly caused by the delays incurred when a mobile station (STA) transfers a current security context to the target access network or establishes connectivity to a new access point (AP). Existing handoff optimization schemes have mostly focused on reducing the scanning time which is to discover nearby access points. Even though the time taken by a mobile STA to authenticate the target APs contributes to the total handoff delay, the schemes to optimize the authentication time have not yet been fully investigated for providing seamless connectivity to mobile users performing handoff in WLANs. As a solution, pre-authentication, a technique performing the authentication of target APs before the completion of the handoff procedure, has attracted considerable attention to reduce the overall delay related with a handoff, which is performed within inter-subnet and/or inter-administrative domain levels. Therefore, in this article, we propose a novel pre-authentication scheme to minimize the handoff delay in 3G-WLAN interworking architecture. The proposed scheme pre-authenticates a new AP directly through a switched channel in a short period of time. Our evaluation shows that the proposed scheme outperforms the existing authentication schemes defined in the IEEE 802.11 standards in terms of authentication delay, signaling cost, and mobility rate. The proposed mechanism offers an additional advantage in that it is easy to implement and deploy by simply modifying the device driver modules of clients' WLAN interfaces.