Jarkko Kneckt

IEEE 802.11ac: Enhancements for very high throughput WLANs

The IEEE 802.11ac is an emerging very high throughput (VHT) WLAN standard that could achieve PHY data rates of close to 7 Gbps for the 5 GHz band. In this paper, we introduce the key mandatory and optional PHY features, as well as the MAC enhancements of 802.11ac over the existing 802.11n standard in the evolution towards higher data rates. Through numerical analysis and simulations, we compare the MAC performance between 802.11ac and 802.11n over three different frame aggregation mechanisms, viz., aggregate MAC service data unit (A-MSDU), aggregate MAC protocol data unit (A-MPDU), and hybrid A-MSDU/A-MPDU aggregation. Our results indicate that 802.11ac with a configuration of 80MHz and single (two) spatial stream(s) outperforms 802.11n with a configuration of 40 MHz and two spatial streams in terms of maximum throughput by 28% (84%). In addition, we demonstrate that hybrid A-MSDU/A-MPDU aggregation yields the best performance for both 802.11n and 802.11ac devices, and its improvement is a function of the maximum A-MSDU size.

Advances in D2D communications: Energy efficient service and device discovery radio

Device-to-Device communications with automated connectivity to sensors, machines and other users is an important enabler for a multitude of use cases with local social networks as one example. In this paper we focus on the main challenges to build a seamless user experience. In particular, we present a novel device beaconing scheme to facilitate service and device discovery. Moreover, the mechanism enables the exchange of small data packets and facilitates the connection setup of a suitable transport radio. We discuss the energy efficiency of the proposed device discovery mechanism and evaluate the capability to form a network in a residential scenario with different device densities.

On efficient discovery of next generation local area networks

In this paper we propose an energy efficient idle scanning method of local area networks, which could be provided within the framework of Automated Network Discovery and Service Function in 3GPP Long Term Evolution. Further, we combine it with a proposal to utilize an accelerometer, to limit the amount of scans during times when the UE is not moving. We evaluate the scanning strategies in a residential scenario where a model for varying access point density is applied based on the uptake of the 802.11n technology. We further extend this scenario by proposing a mobility model. The results show that without assistance the UE will spend a significant amount of energy on scanning in areas with low density of access points, which will result in insufficient stand-by performance. Further, our studies show that the proposed assistance with channel knowledge is an effective way to keep the energy consumption at a tolerable level.

Performance Analysis of IEEE 802.11ac DCF with Hidden Nodes

Recently, the IEEE 802.11 standard based Wireless Local Area Networks (WLAN) have become more popular and are widely deployed. It is anticipated that WLAN will play an important rule in the future wireless communication systems in order to provide several gigabits data rate. IEEE 802.11ac is one of the ongoing WLAN standard aiming to support very high throughput (VHT) with data rate of up to 6 Gbps below the 6 GHz band. In the development of IEEE 802.11ac standard, several new physical layer (PHY) and medium access control layer (MAC) features are taken into consideration, such as employing wider bandwidth in PHY and incrementing the limits of frame aggregation in MAC. However, due to the newly introduced features, some traditional techniques used in previous standards could face some problems. This paper presents a performance analysis of 802.11ac Distributed Coordination Function (DCF) in presence of hidden nodes in overlapping BSS (OBSS) environment. The effectiveness of DCF in IEEE 802.11ac WLAN when using different primary channels and different frequency bandwidth has also been discussed. Our results indicate that the traditional RTS/CTS handshake mechanism faces shortcomings and needs to be modified in order to support the newly defined 802.11ac amendment.

Enhanced channel scanning schemes for next generation WLAN system

The IEEE 802.11 standard based Wireless Local Area Networks (WLANs) are widely deployed and have gained greater popularity. It is anticipated that WLAN will play an important rule in the future wireless communication systems in order to provide several gigabits data rate. However, it has been a challenging problem to support the IEEE 802.11 WLAN devices to fully exploit the high throughput gains offered by the IEEE 802.11 standard whenever possible since the current channel scanning mechanisms in standard may result in unacceptable delay for network discovery. In this work, we review the behavior of passive and active channel scanning schemes of the current IEEE 802.11 specification, and also propose two enhancements for the active scanning mechanism based on the draft of IEEE 802.11ai standard. The proposed schemes can reduce the overhead of transmitted management messages while improving the channel scanning performance. In addition, it can also increase the speed of discovery of APs before associating with one and enable more precise discovery operations. Through simulation study, it is shown that simulation results can explicitly verify our expectations on the superorities of the proposed schemes.

Performance Analysis of the IEEE 802.11s PSM

With the introduction of IEEE 802.11 power save mode (PSM), a lot of work has been done to enhance the energy saving ability of the wireless nodes. The ultimate goal of the research is to make the networking equipment carbon neutral and prolong the lifetime of the energy limited device for various applications; in some cases it is a trade-off between energy efficiency and delay. However, few studies have been made until now in the area of IEEE 802.11s based link specific power mode. The essence of this method is the ability of a node to maintain different power modes with its different peer nodes at the same time. A new peer service period (PSP) mechanism is also proposed in IEEE 802.11s amendment for transmitting to a receiver operating in PSM. In this paper the performance of the link specific power mode is studied for a single- and a multilink network in terms of energy, delay throughput, and sleep duration. It is found that at small load the energy saving could be as high as eighty percent when compared with the active mode operation. A stochastic model, based on discrete time discrete state Markov chain, is developed for one peer link operation to study the system behavior closely during PSM operation.

Performance Study of IEEE 802.11s PSM in FTP-TCP

With the introduction of IEEE 802.11 power save mode (PSM), a lot of work has been done to enhance the energy saving ability of the nodes. The ultimate goal of the research is to make the networking equipments carbon neutral and prolong the lifetime of the energy limited devices for various applications; in some cases it is a trade-off between energy efficiency and delay. However, few studies have been made until now in the area of IEEE 802.11s based link specific power save mode. The link specific power save mode is a totally new concept. The essence of this method is the ability of a node to maintain different power save modes with its peer nodes. In this paper, the performance of the link specific PSM for FTP-TCP traffic is studied from the energy efficiency point of view. The throughput, the percentage of energy saving and the flow level fairness are examined in this study. Our results indicate that for a suitable combination of link specific PSM, the network not only achieves the same throughput as the active mode operation offers but also saves a significant amount of energy. The study also suggests that there is a trade-off among throughput, percentage of energy saving and fairness.