Cristina Martello

Radio resource sharing for ad hoc networking with UWB

Ultra-wideband (UWB) radio is becoming a promising field for new generations digital communication systems. This technique, based mainly on the impulse radio paradigm, offers great flexibility and shows enormous potential in view of a future broadband wireless access. We present the main principles to design a multiaccess scheme based on UWB. The potential of UWB is exploited within a distributed ad hoc wireless system, where we describe the principles for the definition of a medium-access control (MAC) for mobile computing applications and we analyze the main performance results derived from simulations. A general framework for radio resource sharing is outlined for classes of traffic requiring both elastic-dynamic and guaranteed-reserved bandwidth. Then, we discuss the issue of supporting the proposed radio resource sharing scheme by means of a distributed MAC protocol.

MAC principles for an ultra wide band wireless access

Ultra wide band (UWB) radio is becoming a promising field for the design of new digital communication systems. This technique, mainly based on the impulse radio paradigm, offers great flexibility and enormous potentiality in view of a broadband wireless access. This paper presents the main principles for the development of a multi-access scheme based on UWB. The principles for the definition of a distributed medium access control for mobile computing applications are described as well as the detailed functional model involved in the capacity-sharing procedures.

Radio resource management in infrastructure-based and ad hoc UWB networks

Summary Modeling the resource manager of an ultra wide band (UWB) network is the main object of this paper. The model is tested in two different application scenarios: (i) a UWB WLAN access network to a backbone where the resource management module is implemented at the access points (APs); (ii) a UWB ad hoc network for either local communications or data exchange among sensors, with peer-to-peer links with distributed management. The design must include a quality of service (QoS)-aware strategy and must take into account coexistence issues raised by the use of UWB at the physical layer. Link quality is represented by the maximum end-to-end delay and minimum percentage of correct packets. From these parameters, the resource manager jointly selects the values of power and rate which must be adopted at the physical layer. In the model, radiated power by each device is supposed to be limited by an upper bound, reflecting thus the limitation imposed by regulation. QoS awareness and power constraints are satisfied, thanks to the implementation of an admission control function, which is centralized in the AP in the WLAN case and distributed in the ad hoc case. Major innovative aspects include: (i) taking into account UWB specific features; (ii) introducing QoS awareness based on network layer parameters rather than physical layer parameters; (iii) incorporating error protection functionalities for the optimization of transmission efficiency; (iv) considering both centralized and distributed resource management. Performance of the proposed resource manager module is evaluated in the presence of different classes of traffic, that is multimedia, voice, and data traffic. For each class of traffic, performance is expressed in terms of the maximum possible number of simultaneous connections for the WLAN case, and in terms of the effective achievable throughput for the ad hoc case. Results of simulations indicate that the behavior of the proposed scheme is strongly dependent upon the class of traffic in the WLAN scenario, while it is slightly affected by changes in traffic characteristics in the ad hoc case. Copyright # 2005 John Wiley & Sons, Ltd.

Integrating UWB radio access procedures with a stateless IP QoS paradigm

Ultra wide band (UWB) radio is an interesting radio paradigm for the provision of wireless access to the Internet, in the short-range area. The UWB technology has the potential to combine reduced transceiver complexity with low power consumption, flexible configuration of the radio links and robustness with respect to multipath fading. The IST project WHYLESS.COM, funded by the European Union, is studying the potentiality of this technique for the development of an open mobile access network, i.e., an access network based on a versatile air interface, which, when combined with suitable IP-based operations, can provide an open platform to support QoS aware services. In this paper, we present a proposal for a network architecture where UWB radio access procedures are combined with a stateless IP QoS paradigm.

Ultra wide band WLANs: a self-configuring resource control scheme for accessing UWB hot-spots with QoS guarantees

In the framework of wireless access networks the Hot-Spot concept is attracting several operators. In a Hot-Spot near stationary terminals may reach one or more Radio Access Points (RAP) offering wireless access to the fixed network. Mobile terminals should be able to register to the network, associate to a RAP and activate a wireless communication supporting given bit rates and Quality of Service (QoS) features. Several mobile users, requiring different services, enter and exit the Hot-Spot. In this scenario network operators should have the opportunity to configure quickly radio resources to serve the mobile terminals and to handle efficiently the network resources in order to maximize the income. Among the different technologies emerging in this field, we investigate the feasibility of a wireless access based on Ultra Wide Band (UWB) radio, combined with a flexible admission control scheme based on transmission power selection. We employ UWB in unlicensed mode, i.e., we operate in accordance to the limits imposed by the regulatory bodies (e.g., US Federal Communications Commission). The flexibility of the admission control depends mainly on the capability of a mobile terminal of “measuring” the environment it is entering and thus supporting the RAP in the selection of the appropriate transmission parameters. The proposed approach provides an admission policy based on the Maximum Extra Interference (MEI) and selects the power level through a simple interaction among the involved mobile terminals. The information for basing the decision on is collected through measurements and signaling. In order to increase the system efficiency, transmission parameters are selected in accordance to a “balancing” criterion (thus Balanced-MEI, B-MEI). The B-MEI approach keeps quite simple the admission of new mobile terminals in a RAP’s area but contemporarily satisfies the trade-off between fair resource assignment and system efficiency. This is a key trade-off in wireless access systems where interference effects determine the upper limit of the number of users that can be admitted in the network.

Improving Wireless Access Control Schemes via Adaptive Power Regulation

Two challenging issues for future wireless communication systems are the support of Quality of Service (QoS) and the definition of flexible access schemes to be used in heterogeneous systems (public cellular systems, wireless local area and ad-hoc networks). This paper deals with the class of Radio Resource Control (RRC) based on power regulation, where typical PHY layers parameters (powers, interference, etc.) are combined with upper layers ones to i) increase radio channel utilization; ii) perform admission control of heterogeneous wireless links; iii) maintain negotiated QoS levels expressed as a function of the Signal-to-Interference-Ratio (SIR). In the recent literature power control is mainly employed to dynamically adapt the transmission of concurrent links to the varying system conditions (due to channel quality, mobility) still guaranteeing the perceived QoS. In this framework, we investigate how the design of a suitable power control can be used in the support of traffic requiring some QoS guarantees. The paper presents a paradigm where all the RRC operations are performed in a distributed way, i.e., independently for each link involved in a communication. The distributed approach assures that the strategies are quite flexible to be used both in cellular-like systems and in ad-hoc networks.

Optimizing the radio resource utilization of multiaccess systems with a traffic-transmission quality adaptive packet scheduling

In this paper we state a general framework for radio resource allocation based on a matrix which highlights the trade-offs of complexity and efficiency. This framework is outlined for the systematic definition of scheduling algorithms that are jointly adaptive to traffic and to transmission quality in order to improve the radio resource utilization and the achievable throughput of cellular networks for the support of best-effort traffic. We consider the application of the matrix concept to both time division and code division multiple access, the latter scheme also bringing about mutual interference among competing users. Then we propose a scheduling algorithm for wireless systems, called channel adaptive open scheduling (CHAOS). The CHAOS performance in terms of throughput and delay is extensively compared with those resulting from a load adaptive channel independent scheduling (CIS). A major result of this work is the quantitative assessment of the performance advantage allowed by jointly accounting for traffic congestion and transmission quality. Moreover the main implementation issues related to the proposed algorithms are investigated.