Energy efficient routing is a critical problem in multihop wireless networks due to the severe power constraint of wireless nodes. Despite its importance and many research efforts towards it, a distributed routing algorithm that maximizes network lifetime is still missing. To address this problem, we propose a novel utility-based nonlinear optimization formulation to the maximum lifetime routing problem. Based on this formulation, we further present a fully distributed, localized routing algorithm, which is proved to converge to the optimal point, where the network lifetime is maximized. Solid theoretical analysis and simulation results are presented to validate our solution

Recent research based on traffic measurements shows that Internet traffic flows have a fractal nature (i.e., self-similarity property), which causes an underestimation of network engineering parameters when using the conventional Poisson model. Preliminary field measurements demonstrate that packet data traffic in wireless communications also exhibits self-similarity. In this paper, we investigate the queuing behavior of self-similar traffic flows for data applications in packet-switching wireless networks. The traffic is generated by an on-off source with heavy-tailed on periods. We extend a previous relationship among the asymptotic distribution of loss probability, finite buffer size, traffic specifications, and transmission rate for a wireline system to a wireless system, taking into account wireless propagation channel characteristics. We also investigate the multiplexing of heavy-tailed traffic flows with a finite buffer for the downlink transmission of a cellular network. Computer simulation results demonstrate that assumptions made in the theoretical analysis are reasonable and the derived relationship is accurate

This paper presents two new layer 4 fairness measures, the worst case TCP fairness index and the TCP fairness index. The purpose of the two indices is to measure the performance of algorithms scheduling elastic traffic in wireless networks. Numerical evaluation of round-robin, proportional-fair and max-rate scheduling shows that the new measures can accurately classify the fairness properties of the studied scheduling algorithms. This means that the new fairness measures are appropriate for measuring TCP fairness. The worst case TCP fairness index is the primary measure. The TCP fairness index can be used as a complement in certain cases. The new fairness measures are also compared with two layer 2 fairness measures. Numerical evaluation shows that the new layer 4 measures and the layer 2 measures in some aspects show similar results. However, when evaluating transport layer fairness, it is better to use the new layer 4 measures as they actually measure fairness on layer 4 and the results are easier to interpret

cheduling plays an important role in providing quality of service (QoS) support for multimedia networks. We propose a cross-layer scheduler at the medium access control (MAC) layer for multiple connections with diverse QoS requirements, where each connection employs adaptive modulation and coding (AMC) scheme at the physical (PHY) layer. Each connection is assigned a priority, which is updated dynamically based on its channel and service quality; and the connection with the highest priority is scheduled each time. Our scheduler provides diverse QoS guarantees, uses the wireless bandwidth efficiently and enjoys flexibility, scalability and low implementation complexity. The performance of our scheduler is evaluated via simulations in the IEEE 802.16 standard setting

In this paper, we first propose an analytical model of WLANs (wireless LANs) with an arbitrary backoff distribution and AIFS (arbitration inter-frame space). From the analysis, we show that the achievable bandwidth is determined by the mean of backoff distribution regardless of the shape of the backoff distribution. We compare the effectiveness of four parameters on channel access differentiation, namely, the mean of backoff distribution, CWmin (initial contention window), the number of backoff stages, and AIFS. Numerical results show that the mean of backoff distribution provides weighted fair channel access most accurately. Second, based on the proposed analytic frame work, we develop three schemes for the uplink/downlink bandwidth differentiation in order to achieve weighted fairness between uplink and downlink transmissions. Note that IEEE 802.11 is known to have unfairness between uplink and downlink accesses. Each scheme is characterized according to the corresponding channel access rule. The simulation results show that the proposed schemes achieve high system throughput while accurately differentiating bandwidth allocation

Despite its support of prioritized services, the IEEE 802.11e enhanced distributed channel access (EDCA) cannot guarantee strict QoS required by real-time services such as voice and video without proper network control mechanisms. To overcome this deficiency, we first build an analytical model to derive upper bounds for both delay means and variations for services of different priorities in the non-saturated 802.11e WLAN, showing that the QoS requirements of real-time services can be satisfied if the input traffic is properly regulated. Based on the analysis, we then propose a call admission control scheme and a rate control scheme to ensure that QoS requirements of real-time services are statistically guaranteed and that best effort services can efficiently use the residual bandwidth

MIMO techniques using multiple antennas for both transmitting and receiving have recently manifested themselves to be very promising for future broadband wireless networks. Aiming to leverage the impact of these MIMO techniques on network protocol design in wireless LANs (WLANs), we take a utility approach to study channel-aware weighted proportional fair medium access control (WPF MAC) for QoS provisioning. Simply put, in this utility based approach, every user in a WLAN attempts to maximize its own utility, and the optimization procedure takes place in two stages: a channel contention phase that arbitrates fair channel access across the users via combining adaptive persistence mechanism with random backoff, and a data transmission phase that determines the transmission duration based on the channel conditions in each transmission round. Furthermore, adaptive beamforming is carried out by using the training signals embedded in the RTS/CTS handshake to enhance the spectral efficiency of the MIMO links. Using a stochastic approximation method, together with the Lyapunov stability theorems, we establish the stability of the adaptive persistence mechanism in the proposed WPF MAC and analyze the fairness across the users therein

Wireless extension points (EPs) are immobile devices that relay data between the access point and the mobile users in a heterogeneous wireless local area network (WLAN). In this paper, we investigate the optimal placement of EPs such that the throughput capacity of a rectilineal WLAN is maximized. Two channel models are studied, based on the Shannon capacity bound and IEEE 802.11 specifications. We propose an efficient EP placement algorithm that determines the optimal locations of a fixed number of EPs. Our results show that, for a wide range of system parameters, the optimally placed EPs can significantly increase the network throughput capacity. Moreover, we study how the number of EPs, transmission power, path loss exponent, channel models and traffic characteristics affect the optimal EP placement and expected throughput capacity of the network

In this paper, we study the provision of per-class QoS for IEEE 802.11e enhanced distributed channel access (EDCA) WLANs. We propose two mechanisms, called BIWF-SP and IDFQ-SP, based on backoff interval (BI) and inter-frame space (IFS), respectively. In our mechanisms, both strict priority and proportional fair service are supported. We describe the operations of the proposed mechanisms in details, and compare their performance with the original EDCA mechanism via simulations. The results show that both BIWF-SP and IDFQ-SP outperform the original EDCA in terms of the support for both strict priority and weighted fair service. Compared to IDFQ-SP, BIWF-SP is easier to be implemented in real systems; compared to BIWF-SP, IDFQ-SP has better aggregate throughput and is more stable. More importantly, both mechanisms conform to the IEEE 802.11e EDCA standard, rendering both good candidates to provide per-class QoS service for IEEE 802.11 WLANs

Grido is an architecture that targets a network operator intending to provide enhanced services to its customers. This is achieved by setting up a "backbone" overlay network. A backbone overlay is a set of Internet hosts dedicated to providing overlay services. A network operator can view Grido as a sandbox for rapid prototyping and market adoption assessment of novel services. In the past, overlay networks have been designed to mitigate deployment issues of functionalities such as multicast and QoS at the network layer. Grido provides a WS-agreement based negotiation interface complying with the current Global Grid Forum (GGF) standards. We propose to use a novel virtual coordinates-assisted overlay construction and maintenance protocol. We demonstrate using simulations, that Grido incurs a low latency overhead while maintaining sparse connectivity on the backbone overlay. Grido also incurs low overhead for virtual coordinates estimation and chooses the closest 5% overlay node to any IP address, 95% of the time