Andrey M. Turlikov

WIRELESS BROADBAND ACCESS: WIMAX AND BEYOND - Investigation of Bandwidth Request Mechanisms under Point-to-Multipoint Mode of WiMAX Networks

The WiMAX standard specifies a metropolitan area broadband wireless access air interface. In order to support QoS for multimedia applications, various bandwidth request and scheduling mechanisms are suggested in WiMAX, in which a subscriber station can send request messages to a base station, and the base station can grant or reject the request according to the available radio resources. This article first compares two fundamental bandwidth request mechanisms specified in the standard, random access vs. polling under the point-to-multipoint mode, a mandatory transmission mode. Our results demonstrate that random access outperforms polling when the request rate is low. However, its performance degrades significantly when the channel is congested. Adaptive switching between random access and polling according to load can improve system performance. We also investigate the impact of channel noise on the random access request mechanism

Study of Beaconing for Car-to-Car Communication in Vehicular Ad-Hoc Networks

IEEE 802.11p is currently being developed international standard, which specifies physical (PHY) and medium access control (MAC) protocols for car-to-car and car-to-infrastructure communication and should become a basis for safety-related and infotainment applications in future vehicular ad-hoc networks (VANETs). In VANETs beaconing is one of the most important communication modes, which is used to advertise the presence of a car to its neighbor cars. For different applications timely and successful delivery of beacons containing speed, direction and position of a car is extremely important. In this paper, we present analytical methods for car-to-car communication analysis and investigate the influence of beacon generation rate on the mean beacon transmission delay and probability of a successful beacon reception in the IEEE 802.11p-based network in both saturated and unsaturated cases.

Capacity analysis of reservation-based random access for broadband wireless access networks

In this paper we propose a novel model for the capacity analysis on the reservation-based random multiple access system, which can be applied to the medium access control protocol of the emerging WiMax technology. In such a wireless broadband access system, in order to support QoS, the channel time is divided into consecutive frames, where each frame consists of some consequent mini-slots for the transmission of requests, used for the bandwidth reservation, and consequent slots for the actual data packet transmission. Three main outcomes are obtained: first, the upper and lower bounds of the capacity are derived for the considered system. Second, we found through the mathematical analysis that the transmission rate of reservation-based multiple access protocol is maximized, when the ratio between the number of mini-slots and that of the slots per frame is equal to the reciprocal of the random multiple access algorithms transmission rate. Third, in the case of WiMax networks with a large number of subscribers, our analysis takes into account both the capacity and the mean packet delay criteria and suggests to keep such a ratio constant and independent of application-level data traffic arrival rate.

Stabilizing multi-channel slotted aloha for machine-type communications

In this paper, we consider a wireless cellular system with an unbounded population of machine-type users. The system provides a number of non-interfering slotted-time channels which users contend for when sending their uplink data packets. We propose a provably stable control procedure for the channel access probability in the sense that it maintains a finite number of unserviced users in the system. We also compare the proposed algorithm against the optimal multi-channel slotted Aloha to conclude that our solution demonstrates near-optimum performance.

Energy efficient communications for future broadband cellular networks

Energy efficiency is increasingly important for wireless cellular systems due to the limited battery resources of mobile clients. While modern cellular standards emphasize low client battery consumption, existing techniques do not explicitly focus on reducing power that is consumed when a client is actively communicating with the network. In this paper, we evaluate the performance of the recently introduced power-bandwidth optimization techniques using realistic cellular system simulation model, which is compliant with the methodology proposed for the IEEE 802.16m standard. The paper addresses several practical trade-offs associated with the implementation of energy efficient schemes. Our simulation results indicate that energy efficient techniques continue to provide considerable power savings, even when accounting for realistic system parameters and channel environments.

Active-mode power optimization in OFDMA-based wireless networks

Energy efficiency is increasingly important for wireless cellular systems due to the limited battery resources of mobile clients. While modern cellular standards emphasize low client battery consumption, existing techniques do not explicitly focus on reducing power that is consumed when a client is actively communicating with the network. Based on high data rate demands of modern multimedia applications, active-mode power consumption should also be an important consideration for wireless system design and standards development. Recent work in this area shows that radio resource management schemes optimizing energy efficient metrics can provide considerable reduction in client power consumption. In this paper, we evaluate the performance of such techniques using realistic cellular system simulation model. Specifically, we focus on the emerging fourth generation IEEE 802.16m standard. Our simulation results indicate that energy efficient techniques continue to provide considerable power savings, even when accounting for realistic system parameters and channel environments.

Distributed Queue Random Multiple Access Algorithm for Centralized Data Networks

The development of efficient media access control protocols for new generation networks, such as IEEE 802.16 metropolitan wireless system, is a challenging task nowadays. The problem of designing an efficient random multiple access algorithm for centralized data network, where subscriber stations transmit bandwidth requests to the base station in an uplink channel, is a focus of the paper. For this purpose special model for a centralized network is considered and new random multiple access algorithm is developed and analyzed. This algorithm, further referred to as distributed queue algorithm (multi-FS-ALOHA), is shown to provide higher tenacity and lower mean delay for the request transmission in comparison to binary exponential backoff, standardized in IEEE 802.16, as well as FS-ALOHA it is based on. Optimization of parameters for the developed algorithm is fulfilled; impact of the noise on its performance is investigated. The analysis is conducted by means of both analytical techniques and simulations

IEEE 802.16m energy-efficient sleep mode operation analysis with mean delay restriction

IEEE 802.16e standard currently supports mobile subscriber stations, which substantiates the need for energy-efficient communication. In this paper we analyze a novel sleep mode mechanism to be considered for the future IEEE 802.16m standard. We study the overall message delay in the downlink channel and explicitly account for the sleep mode power consumption. Simple expressions are given based on M/D/1 queueing system with multiple vacations. The analytical approach is verified by simulation.

Optimizing energy efficiency of a multi-radio mobile device in heterogeneous beyond-4G networks

In this paper, we address the operation of a multi-radio mobile device in heterogeneous wireless deployments. We assume that such a device may efficiently control its radio interfaces when using the available radio access technologies. In particular, we investigate the potential of flexible transmit power allocation and develop a provably optimal power control scheme that strictly maximizes the energy efficiency of the mobile device, while at the same time satisfies the minimum required level of the user data rate. When compared against simpler (heuristic) power control strategies, our solution always demonstrates the best energy efficiency of the multi-radio device by enabling collaborative operation between several radio technologies, which makes it a useful benchmark for the future integrated beyond-4G wireless networks.

Modeling unreliable LSA operation in 3GPP LTE cellular networks

Presently, we observe an unprecedented growth of traffic volumes in modern cellular networks. Consequently, to effectively meet the impeding capacity crunch, current spectrum bands can be extended by using LSA (Licensed Shared Access) - the promising technology that allows an operator to lease additional frequency bands in order to satisfy the increasing data rate requirements. This technology is naturally suitable for the state-of-the-art 3GPP LTE cellular networks, since it allows to flexibly control resource allocation across the network users. Owing to that, the operator can employ the LSA band whenever desired to improve area capacity and increase data rate. However, due to the fact that the LSA band may be unexpectedly revoked by its original owner, there exists a certain chance of degradation in system performance and user service quality. This paper focuses on studying a one-cell 3GPP LTE system over the LSA technology, with both analysis and simulations, by proposing a baseline methodology to model the unreliable operation of an LSA frequency band.