Two interference-based sub-carrier group assignment strategies in dynamic resource allocation are proposed for MC-CDMA wireless systems to achieve high throughput in a multi-cell environment. Least interfered group assignment (LIGA) selects for each session the sub-carrier group on which the user receives the minimum interference, while best channel ratio group assignment (BCRGA) chooses the sub-carrier group with the largest channel response-to-interference ratio. Both analytical framework and simulation model are developed for evaluation of throughput distribution of the proposed LIGA and BCRGA schemes. An iterative approach is devised to handle the complex interdependency between multi-cell interference profiles in the throughput analysis. Illustrative results show significant throughput improvement offered by the proposed interference-based assignment schemes for MC-CDMA multi-cell wireless systems. In particular, under low loading conditions, LIGA renders the best performance. However, as the load increases BCRGA tends to offer superior performance.

It is widely recognized that the next-generation wireless networks will integrate heterogeneous wireless technologies. The complementary characteristics of cellular networks and wireless local area networks (WLANs) make the interworking a promising trend. Admission control is one of the essential mechanisms to enhance QoS provisioning in a cellular/WLAN integrated network and utilize the overall resources efficiently. In this paper, we propose an effective admission control scheme for both voice and data services. The admission region is derived, taking into account the two-tier overlay structure, non-uniform traffic distribution and user mobility in the integrated network. The impact of traffic and mobility parameters on the admission scheme is evaluated, which provides some insights for further extension.

This paper proposes efficient resource allocation techniques for a domain-based wireless/wireline interworking architecture. Resource allocation is driven by the service level agreement (SLA). Each wireless domain can freely choose its internal resource management schemes to guarantee the customer access SLA (CASLA), while the border-crossing traffic is served by a DiffServ/MPLS core network according to the transit domain SLA (TRSLA). Specifically, we propose an engineered priority scheme for a cellular wireless domain, where the CASLA for each service class is met with efficient resource utilization and the interdomain TRSLA bandwidth requirement can be obtained conveniently. In the transit domain, the traffic load fluctuation from upstream access domains is tackled with an inter-TRSLA resource sharing technique, where the spare capacity from underloaded TRSLAs can be exploited by the overloaded TRSLAs to improve resource utilization.

In this paper, we study and quantify the impact of the most widely used security protocols, such as 802.1x, EAP, IPSEC, SSL and RADIUS, in wireless local area networks (WLANs). Based on the measurements in a wireless network testbed, we present quantitative, realistic findings with regards to both security functions as well as network performance. First, we describe experimental setup including system configuration and protocol stack. Then, we consider a variety of individual and hybrid security policies in order to capture the impact of security services at different network layers. Moreover, depending upon mobile nodes' current location, user mobility is categorized into non-roaming and roaming scenarios. In addition, we define several performance metrics such as authentication time, authentication messages, response time, throughput to measure the overhead associated with security policies on system performance. Comprehensive experimental measurements and analysis are provided for TCP/UDP traffic streams and network variations to demonstrate the impact of security protocols in WLANs.

Due to varying wireless channel conditions, the IEEE 802.11 wireless local area network (WLAN) standard supports multiple modulation types to accommodate the tradeoff between data rate and bit error rate. In Heusse(2003), Rousseau, Berger-Sabbatel and Duda theoretically analyzed a performance anomaly when multi-rate stations with different modulation types exist in IEEE 802.11 WLANs. The performance anomaly is: the aggregate throughput of those stations transmitting at a higher data rate will dramatically degrade below the same level as that of those stations transmitting at a lower data rate. In this paper, we address the anomaly problem and formulate a nonlinear mixed integer programming problem to maximize the total aggregate throughput of all stations subject to that the channel occupancy times among the stations transmitting at different data rates are kept at a fairness ratio. With its aid, a single-hop WLAN can dynamically accommodate the resource access usage to maximize the system throughput in varying fading environments. We prove that the optimization problem is intractable and propose a heuristic solution based on a penalty function with gradient-based approach to solve it. We show the effectiveness of the approach via computational experiments and provide some useful guidelines to regulate the parameters needed for the approach.

Radio spectrum allocated for use in unlicensed wireless networks is distributed across non-contiguous frequency bands. Existing MAC protocols, like IEEE 802.11, operate only in contiguous bands. Several small slices of frequency are available in lower frequency bands that are not utilized. We propose utilizing a sliver of unused spectrum in the lower frequency band as a low rate control channel to improve the capacity of infrastructure and multi-hop wireless networks. The proposed control channel-based MAC Protocol (C2M) increases the throughput by moving the contention resolution overheads to the separate low rate channel. We allow simultaneous channel contention and data transmission by incorporating advance reservation on the control channel, and data aggregation on the data channel. Simulation results show that compared to IEEE 802.11, C2M significantly improves network performance.

We consider the following two views of an IEEE 802.11 based Wireless LAN: (i) as seen by the WLAN medium and (ii) as seen by a user. In the system centric view, we model the WLAN medium as a server that allocates its resources to users in a round Robin manner. This resource sharing model not only provides a simple model for the system, it also enables us to derive the channel service rate and the total delay incurred in transmitting a packet. For Poisson arrivals, the resource sharing model takes the form of an M/G/1/PS system with the mean delay being the same as that in an equivalent M/M/1 system. We then take a user centric view and model each user's queue as a separate G/G/1 queue. We derive the probability distributions for the different delay sources, i.e., random back-off time, random number of collisions and random number of successful transmissions from other users. This user centric model can provide insights into understanding access and queuing delays in 802.11 DCF. Finally, we discuss the utility of these models for functions such as capacity analysis, admission control and QoS enforcement.

Recent advances in multi-radio multi-channel transmission technology have the potential of substantially improving the system capacity in multi-hop wireless networks. While previous work has primarily focused on the link level protocol design, in this paper we investigate the achievable performance gain, by jointly optimizing routing and scheduling in a multi-radio multichannel multi-hop network. We formulate the optimization under a deterministic model, and we seek to minimize overall system activation time in use to satisfy given end-to-end traffic demands subjected to the multi-access interference among neighboring transmissions and the radio interface constraint at each node. The exact solution to such an optimization problem is prohibitively complex due to the combinatorial complexity, particularly with the deployment of multi-radio and multi-channel. We develop a column generation based approach to solve this problem, which decomposes the original problem into sub-problems and solves them iteratively. Numerical results are given, and discussions as well as insights into the performance aspects for multi-radio multichannel deployment are provided.

In this paper, we introduce a novel concept of integrating ''macro-mobility" information obtained from the sociological movement pattern of mobile MANET users into routing. The extraction of this mobility information is based on our observation that the movement of a mobile user exhibits a partially repetitive "orbital" pattern involving a set of "hubs" in practice. This partially deterministic movement pattern is both practical and useful in locating nodes and routing packets to them without the need for constant tracking or flooding. Leveraging on this hub-based orbital pattern, we propose a sociological orbit aware location approximation and routing (SOLAR) protocol. Through extensive performance analysis we show that SOLAR significantly outperforms conventional routing protocols like dynamic source routing (DSR) and location aided routing (LAR) in terms of higher data throughput, lower control overhead, and lower end-to-end delay.

Efficient routing is very important for mobile ad hoc networks (MANETs). Most of the existing routing protocols consider homogeneous ad hoc networks, in which all nodes are of the same type, i.e., they have the same communication capabilities and characteristics. Although a homogeneous network model is simple and easy to analyze, it misses important characteristics of many realistic MANETs such as military battlefield networks. In addition, a homogeneous ad hoc network suffers from poor scalability. In many ad hoc networks, multiple types of nodes do co-exist; and nodes having larger transmission power, higher transmission data rate, and better processing capability, are more reliable and robust than other nodes. Hence, a heterogeneous network model is more realistic and provides many advantages for designing more efficient routing protocols. In this paper, we present a new routing protocol called multi-class (MC) routing, which is specifically designed for heterogeneous MANETs. Extensive simulation results demonstrate that the MC routing has very good performance, and out performs a popular routing protocol AODV (ad hoc on demand distance vector), in terms of reliability, scalability, route discovery latency, overhead, as well as packet delay and throughput.