The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Multipath between end-to-end hosts has been prevailing in Heterogeneous Wireless Networks nowadays, and thus path selection has become an important issue in research for reliable multipath transfer. Most existed path selection algorithms assume that the data and ACK paths are independent, which does not hold for self-contention based wireless networks. This paper has analyzed self-contention's influence...
Recently, handoff is a critical issue for stations in IEEE 802.11-based wireless networks. In order to provide VoIP (Voice over IP) and real-time streaming applications for stations, handoff mechanism must be provided for reducing latency and seamless communication. However, the IEEE802.11 standards handoff is not appropriate to supply their QoS, because it is based on a full-scanning approach. Full-scanning...
The provision of IP Multimedia Subsystem (IMS) introduces important advantages for users of 3G WLAN networks. However, a multi pass authentication procedure needs to be performed before accessing the IMS, resulting in added overhead and quality of service (QoS) degradation, which deters service providers from adopting the IMS model. The problem is further compounded when the user moves from one Wireless...
Deploying 3GPP LTE-Advanced to the ISM band resolves the deployment issue of obtaining feasible bandwidth from crowded spectrum. However, considering that wireless local area networks (WLANs) have been deployed to the ISM band, recent researches show that LTE-Advanced needs to provide communication opportunities for WLANs. Such a coexistence relies on applying the cognitive radio technology to LTE-Advanced...
Due to the rapid growth of real-time applications and the ubiquity of IEEE 802.11 MAC as a layer-2 protocol for wireless local area networks (WLANs), it is of increasing interest to support quality of service (QoS) in such WLANs. In this paper, we develop a simple but accurate enough analytical model for predicting queueing delay in non-homogeneous random access based WLANs. This leads to tractable...
Experimental evaluation of QoS mechanism defined in IEEE 802.11e standard is presented in this paper. Measurements were carried out in controlled laboratory conditions, with and without configured QoS. Mean and maximum delay, jitter and packet loss are measured in voice communications between two clients, competing with other voice clients. The results show that QoS mechanism brings significant improvements...
Being reliable and real-time, are the two most challenging requirements of wireless sensor and actuator networks (WSAN) due to the shared, error-prone and nondeterministic behaviour of wireless communication medium. In this paper, an adaptive data-rate and space-time coding (STC) scheme has been proposed for the IEEE 802.11-based Soft-Real-Time WSAN's utilizing Enhanced Distributed Channel Access...
Response delay problem and measurements of such delays have been reported in Part I. The response delay has a negative impact on the accuracy of spectrum sensing, which is the cornerstone of cognitive radio. In this paper, single-user prediction of channel state is proposed to minimize the negative impact of response delays caused by hardware platforms. Specifically, a modified hidden Markov model...
In multi-interface multi-channel (MIMC) based tactical ad hoc networks, QoS support is one of the main challenging issues for multi-hop transmissions. To support QoS in such a harsh environment, we propose a novel MAC scheme to minimize multi-hop as well as per-hop delay. The current IEEE 802.11 MAC protocols should contend to reserve the channel resource at every hop by each sender. The every-hop...
This paper proposes a solution for throughput and stringent delay problems of VoIP in Ad-Hoc mode of IEEE 802.11 WLAN standards. This paper analyses the behaviour different codecs and schemes of WLAN running on VoIP traffic and draws a conclusion on the performance of network based on the criteria of different QOS parameters. Later the suitability of different routing protocols like AODV, DSR, OLSR...
The 802.11 Wireless Standard defines methods for improving reliability and security on Wireless Local Area Networks (WLANs). Two methods that are especially desirable to enterprise networks are handoff and Remote Authentication Dial-In User Service (RADIUS). Handoff allows seamless mobility on a wireless network, thus providing users with the ability to roam among enterprise wireless access points...
In this paper, a unified analytical model is established to analyze the performance of backoff schemes in IEEE 802.11 DCF networks under saturation condition. It is shown that BEB suffers from deteriorated queueing performance due to a large second moment of access delay, and a key to reduce the second moment lies in the growth rate of the backoff window size. Quadratic Backoff (QB) is further proposed,...
Due to the rapid and independent developments of systems, heterogeneity has become a common feature of current networks. In order to harmonize two different networks and close the gap between their technologies, we need to develop a good mechanism for network selection, and access that best satisfy user requirements. Many public areas (collages, airports, hotels...etc) have different systems for providing...
There are real challenges in both the IEEE 802.11 wireless local area network (WLAN) protocol and the medium access control (MAC)-functions providing the required quality-of-service, high throughput and minimum latencies. The IEEE 802.11 layer supports both the distributed coordination function (DCF) and the enhanced DCF (EDCF). The different access categories (AC) within the EDCF can enhance the...
When multicasting through wireless multihop networks, frame losses at the wireless link cause data losses at the application layer because of no ACK (Acknowledgment) at both data link layer and transport layer. The authors propose a novel multicast scheme to reduce data losses at the application layer and to improve reliability. The scheme incorporates a retransmission mechanism into the data link...
Handover efficiency in wireless and mobile communication networks is an important factor in providing QoS guarantees for real time applications. The 802.11 standard requires a Mobile Node (MN) to scan all the possible channels (11 in the US) to discover available Access Points (AP's) during a handover. In a given 802.11 cell several channels are expected to be empty. Due to a full scan the MN ends...
Cooperation can greatly improve the performance of wireless networks, but not all the time. Due to the dynamics of the wireless network and incomplete information, in many cases, only some uncertain opportunities of cooperation can be found. When these situations arise, opportunistic cooperation techniques, such as algorithms for opportunistic routing, opportunistic spectrum sharing etc. have been...
One of the most popular applications of IEEE 802.16 network is to serve as a backhaul service for IEEE 802.11 networks. However, the traffic of an IEEE 802.16 connection aggregated from IEEE 802.11 networks fluctuates. Thus, efficient bandwidth reservation at the subscriber station (SS) is an importance issue. This study proposes a simple and flexible bandwidth reservation scheme at the SS, called...
Priority based packet transmission techniques are commonly used in communication networks to support multimedia services. In wireless networks mainly type of service or queue measurement based packet transmission priority techniques are used. This paper introduces a novel two stage traffic prediction and type of service based priority technique for an infrastructure based Wireless Local Area Network...
In wireless communication, the discovery of the surrounding access points is crucial to provide seamless connectivity to mobile users. In IEEE 802.11, this discovery process is performed by passive and active scanning functions. For both, timers are usually constant (within the 802.11 driver) and their configuration affects the two main scanning performance metrics, i.e., scanning latency and scanning...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.